Performance and Results Annual Report 2007

ILT

Annual Report Fraunhofer Institute for Laser Technology ILT 2007 Foreword

Industry and the consumer society are A first step in this direction was the becoming ever more demanding. On combination of laser welding and cutt- the one hand, products are expected ing without retooling, using special to offer excellent value for money, optics. This success is likely to encou- which they can generally only do rage further synergies between such if they are mass-produced. On the processes as structuring and polishing other, more and more customers are in tool making. Laser-based solutions requesting high-quality solutions speci- could also help to miniaturize products ally tailored to their individual needs. while at the same time allowing for a Product managers are increasingly wide variety of product versions. Over confronted with such key concepts as the last few years, the Fraunhofer ILT ‘mass customization’ and ‘one-piece has developed various processing stra- flow’. A number of industrial sectors tegies such as the TWIST and SHADOW are producing a growing variety of techniques for high-speed precision products, while at the same time joining with flexible path control. These maintaining a good price-performance are of particular benefit to the clock- ratio and all the positive features of a making, medical and precision successful brand, such as an attractive engineering sectors. design, high functionality, excellent reliability and pronounced user-friend- The market trends of numerous in- liness. dustries are consistently pushing the development of laser technology. The Laser technology has proven to be an Fraunhofer ILT is responding to the excellent problem-solver in reconciling challenging questions and require- all these different requirements. It can ments of its industrial R&D partners be perfectly integrated into modern with creative solutions. Our annual production systems to ensure flexibility, report will give you an idea of our quality and automated operation. many and varied project results. We The Cluster of Excellence »Integrative would also be delighted to take on any Production Technology for High-Wage challenging tasks your own company Countries« at RWTH Aachen Univer- may have for us. With this prospect in sity, of which the Fraunhofer ILT is a mind, I wish you an inspiring read and member, has long been working to look forward to your feedback. solve the dilemma that opposes economies of scale and scope. The first Yours sincerely, achievements, such as the series production of customized dental prosthe- ses by selective laser melting, have already been introduced on the market in close collaboration with an innovative industrial partner. Another noteworthy Professor Reinhart Poprawe M.A. accomplishment is the combination of different laser manufacturing processes in integrated laser systems.

Fraunhofer ILT Annual Report 2007 3

Contents

Profile of the Institute 6 Some Special Research Results from the Business Areas Declaration of Principles 7 of Fraunhofer ILT

Business Areas 8 Laser and Plasma Sources 35 - 60

Board and Committees 10 Laser Material Processing 61 - 106

Contacts 11 Laser Plant and System Technology 107 - 118 Core Areas 12 Laser Measurement Services 14 and Testing Technology 119 - 139

Facts and Figures 16 Patents 140 References 19 Dissertations 141 Fraunhofer USA Center for Laser Technology CLT 20 Diploma Theses 141

Coopération Laser Scientific Publications 142 Franco-Allemande CLFA 22 Lectures 144 Fraunhofer Alliance Surface Engineering and Photonics VOP 24 Conventions and Conferences 148

The Fraunhofer-Gesellschaft Trade Fairs 150 at a Glance 26 Publications 151 Laser Technology at RWTH Aachen 28 CD-Rom »Laser Technology« 154

Cluster of Excellence Technical Book »Laser »Integrative Production Technology Technology for Manufacturing« 155 for High-Wage Countries« 30 Information Service 156 European Laser Institute ELI 32 Imprint 157 PhotonAix e. V. - Competence Network for Optical Technologies 33

Fraunhofer ILT Annual Report 2007 5 Profile of the Institute

In the business area »laser plant and Short Profile system technology« prototypes are developed, built up and installed on site. ILT - for more than twenty years, this ab- Process monitoring and control as well breviation has stood for extensive know- as system components and control how in laser technology. Innovative software are part of the activities. In solutions for manufacturing and pro- the business area »laser measurement duction problems, development of and testing technology« processes and new technical components, competent systems for inspection of surfaces, for DQS certified by advice and training, highly-qualified chemical analysis, for testing the accu- DIN EN ISO 9001 personnel, the latest technologies and racy of dimensions and geometry of Reg.-No.: DE-69572-01 an international reputation: these are workpieces as well as for analysis of the guarantors for long-term business static and dynamic deformations are relations. The numerous customers of developed. the Fraunhofer Institute for Laser Tech- nology ILT belong to various sectors The comprehensive offer of services like automobile industry, mechanical of the Fraunhofer Institute for Laser engineering, chemical and electrical Technology ranges from research and engineering, steel construction, preci- development as well as system construc- sion mechanics and optics. tion and quality assurance to advice and training. Industrial laser systems With more than 250 employees and from various manufacturers as well as 10.000 m2 of usable floor space the an extensive infrastructure are available Fraunhofer Institute for Laser Technolo- for the work on research and gy is world-wide one of the most development projects. important development and contract research institutes of its specific field. In the Laser User Center of the Fraun- The four business areas cover a wide hofer Institute for Laser Technology range of actual and vertical integrated guest companies work in their own topics. In the business area »laser and separated laboratories and offices. The plasma sources« development activities basis of this special form of technology are concentrated on innovative diode transfer is a long-term cooperation and solid state lasers for industrial use agreement with the institute in the as well as compact EUV-sources for field of research and development. lithographic use in semiconductor The surplus value lies in the use of the production. The business area »laser technical infrastructure and in the material processing« offers solutions information exchange with ILT´s in cutting, ablation, drilling, welding, experts. Already 10 companies profit soldering, surface treatment and micro from the advantages of the Laser User processing. The activities cover a wide Center. Besides laser manufacturers range of applications from macro and laser users, entrepreneurs from processing via nano structuring to the areas of special machine production, biophotonics. laser processing and laser measurement find a suitable frame to realize their ideas on an industrial scale.

6 Fraunhofer ILT Annual Report 2007 Declaration of Principles

Mission

We occupy an international top position in transferring laser technology to industrial application.

We continually expand the knowledge base and know-how in our sector and make significant contributions to the ongoing development of science and technology.

Working with our partners in industry, science and government, we create innovations on the basis of new beam sources and new applications.

Customers

The customers needs are the focus of our work.

Discretion, fairness and a spirit of part- Fascination Laser Management style nership are top priorities in our customer relationships. Our customers can rely The unique characteristics of laser light Cooperative, demanding and suppor- on us. and the resulting diversity of applica- tive. Knowing the value of our staff as tions, are a constant source of inspiration individuals and the value of their We tailor solutions and their cost- and fascination. know-how and their commitment effective implementation to the forms the basis of our management demands and expectations of our philosophy. We involve our staff in the customers, with the objective of formulation of goals and the decision- creating a competitive advantage. Staff making process. We place a high value on effective communication, goal- We support industry’s needs for new Teamwork between the individual oriented and efficient work and clear specialists and managerial staff and the group is the foundation of our decisions. through project-based partnerships success. with our customers.

We want our customers to be satisfied Position - because we want them to return. Strengths We work within vertical structures, Our broad spectrum of resources from research to application. enables us to offer one-stop solutions. Chances Our expertise extends from beam source, machining and measuring techniques, We strategically expand our knowledge to application, through to integration base across the network. of systems into the customer’s production line.

Fraunhofer ILT Annual Report 2007 7 Business Areas

Laser and Plasma Sources Laser Material Processing

This business area encompasses the Production processes addressed by development of diode laser modules this business area include cutting and and systems as well as diode-pumped joining techniques applying micro- and solid-state lasers with different reso- macro-technology, as well as surface nator structures (stab,slab,fiber), the engineering. The services provided design of new diode laser structures, extend from process development for the microassembly of diode lasers and the manufacture of sector-specific optical components, and the develop- products and the integration of these ment of plasma systems. processes in production lines, through simulation services for laser applications, For more than 10 years spinn-offs of to the production of samples in sup- the Fraunhofer ILT are set up in the port of series production start-up. The framework of some projects. In coope- strength of the business area is rooted ration with the Fraunhofer IAF new in its extensive process know-how, structures are being designed which which is tailored to specific customer permit the manufacture of diode lasers requirements in each case. In addition demonstrating higher beam quality. to process development, the business The business area continues to enjoy area offers complete system solutions a unique reputation in the assembly which utilize selected technology net- of high-power diode lasers and in works. Customers are offered laser- particular the installation of automated specific solutions that encompass design assembly and test facilities. Work in engineering, material specification, the plasma technology sphere focuses product design, production equipment on the development of EUV beam and quality assurance. In addition to sources for semiconductor lithography. the target market of material process- The main target markets for the busi- ing, the business area also addresses ness area as a whole are laser machining, customers in the medical engineering, medical engineering and metrology, biotechnology and chemical sectors. along with the component market for information and communications technology.

8 Fraunhofer ILT Annual Report 2007 Business Areas

Laser Plant and Laser Measurement System Technology and Testing Technology

This business area focuses on the deve- The services provided by this business lopment of prototype equipment for area include the development of mea- laser and plasma-technology applica- surement and testing processes and tions, as well as on laser systems related equipment for material analysis engineering, particularly in the fields and for geometric testing and surface of automation and quality assurance. inspection. The requisite measurement Areas of application embrace welding, and testing software is tailored to cutting, hardening, repair coating, customer-specific problem areas. Material drilling and micro-joining. The system analysis is based on the deployment of technology offered provides complete laser-spectroscopic processes, focusing solutions for process monitoring, com- on the analysis of metallic and oxidic ponents and control systems for preci- materials, identification testing of high- sion machining, laser-specific CAD/CAM alloy steels, rapid recognition of mate- technology modules, as well as soft- rials for recycling tasks and analysis of ware for measurement, open- and gases and dust. Special electronic com- closed-loop control and testing. For ponents are developed for the parallel its work in process monitoring in parti- processing of detector signals of high cular the business area can draw on bandwidth. extensive and, where required, patent- protected know-how. In this sector In biophotonics joint projects are car- numerous systems have already been ried out in the field of highly sensitive licensed for companies. Target markets fluorecence detection for protein chips include laser equipment and compo- and laser scattered light measurements nent manufacture as well as all sectors in sub-µl test volumes for protein of production industry which deploy crystallization. As part of the area’s lasers in their manufacturing activity work on geometric testing and surface or intend to do so. inspection components, devices and equipment are being developed for obtaining 1 to 3D information about the geometry or surface properties of workpieces. These include processes and special systems for testing the stability of bar and strip products and devices for the 1D to 3D scanning of unit goods. Target markets include the production and the recycling industry which conduct measurement and testing fast and close to the process.

Fraunhofer ILT Annual Report 2007 9 Board and Committees

Dr. Ulrich Steger Board Ministerium für Innovation, Science & Technology Council Wissenschaft, Forschung The Board of Trustees advises the und Technologie des Landes NRW The Fraunhofer-Gesellschaft’s Science Fraunhofer-Gesellschaft as well as the & Technology Council supports and Institute’s management and supports Dr. Klaus Wallmeroth advises the various bodies of the the links between interest groups and TRUMPF Laser GmbH & Co. KG Fraunhofer-Gesellschaft on scientific the research activities at the institute. and technical issues. The members The Board of Trustees during the year The 23rd Board of Trustees meeting are the institutes’directors and one under review consisted of: was held on September 19, 2007 representative elected from the science/ at the Fraunhofer ILT in Aachen. technology staff per institute. C. Baasel (chairman) Carl Baasel Lasertechnik GmbH Members of the Council from the ILT are: Prof. Dr. R. Poprawe, B. Theisen, Dr. Ulrich Hefter Directors’ Committee Dr. C. Janzen. Rofin-Sinar Laser GmbH The Directors’ Committee advises the Dipl.-Ing. H. Hornig Institute’s managers and is involved BMW AG in deciding on research and business Staff Association policy. The members of this committee Dr. U. Jaroni are: Dipl.-Betrw. (FH) Vasvija Alagic In March 2003 the staff association ThyssenKrupp Stahl AG MBA, Dipl.-Phys. A. Bauer, Dr. K. was elected by the employees of the Boucke, Dr. A. Gillner, Dr. J. Gottmann, Fraunhofer ILT and the Department Prof. Dr. G. Marowsky Dipl.-Ing. H.-D. Hoffmann, Dr. S. Kaierle, of Laser Technology. Members are: Laserlaboratorium Göttingen e. V. Dr. I. Kelbassa, Dr. E.-W. Kreutz, Prof. Dipl.-Ing. P. Abels, Dipl.-Ing. G. Backes, Dr. P. Loosen, Dr. W. Neff, Dr. R. Noll, M. Brankers, Dipl.-Phys. J. Geiger, MinRat Dipl.-Phys. T. Monsau Dr. D. Petring, Prof. Dr. R. Poprawe, M. Janßen, Dipl.-Phys. G. Otto, Ministerium für Arbeit und Soziales, Prof. Dr. W. Schulz, B. Theisen, B. Theisen (chair), Dr. A. Weisheit, Qualifikation und Technologie des Dr. B. Weikl, Dr. K. Wissenbach. Dipl.-Ing. N. Wolf. Landes NRW

Dr. Rüdiger Müller Osram Opto Semiconductors GmbH & Co. OHG Health & Safety Committee

Dr. Joseph Pankert The Health & Safety Committee is Philips Lighting B.V. responsible for all aspects of safety and laser safety at the Fraunhofer ILT. Prof. R. Salathé Members of this committee are: Ecole Polytechnique Fédéral Dipl.-Betrw. (FH) Vasvija Alagic MBA, de Lausanne K. Bongard, M. Brankers, A. Hilgers, Dr. E.-W. Kreutz, A. Lennertz, Dr. W. Neff, MinR Dr. Frank Schlie-Roosen E. Neuroth, Dipl.-Ing. M. Poggel, Bundesministerium für Bildung Prof. Dr. R. Poprawe, B. Theisen, und Forschung BMBF F. Voigt, Dipl.-Ing. N. Wolf, Dr. R. Keul (Berufsgenossenschaftlicher Arbeits- Dr. Dieter Steegmüller medizinischer Dienst BAD). DaimlerChrysler AG

10 Fraunhofer ILT Annual Report 2007 Contacts

Prof. Dr. Reinhart Poprawe M.A. (-110) Prof. Dr. Peter Loosen (-162) Dr. Dirk Petring (-210) Director Vice Director Cutting and Joining

Dipl.-Phys. Axel Bauer (-194) Dr. Konstantin Boucke (-132) Dr. Konrad Wissenbach (-147) Marketing and Communication Laser Components Surface Treatment

Dipl.-Betrw. Vasvija Alagic MBA (-181) Dipl.-Ing. Dieter Hoffmann (-206) Dr. Arnold Gillner (-148) Administration Solid State and Diode Lasers Micro Technology

Dr. Bruno Weikl (-134) Dr. Reinhard Noll (-138) Dr. Stefan Kaierle (-212) IT-Management Laser Measurement and System Technology Testing Technology

Dr. Alexander Drenker (-223) Dr. Willi Neff (-142) Prof. Dr. W. Schulz (-204) Quality Management Plasma Technology Modelling and Simulation

Fraunhofer ILT Annual Report 2007 11 Core Areas

Laser Components Laser Measurement and Testing Cutting and Joining Dr. Konstantin Boucke Technology Dr. Dirk Petring Dr. Reinhard Noll • Active und passive cooling • Cutting, perforating, drilling, of diode lasers • Laser measurement processes deep-engraving • Expansion-matched coolers and for online inspection tasks • Welding, brazing, soldering mounting technologies for laser • Development, construction, • High-speed processing diode bars integration and testing of laser • Thick section processing • Mounting of laser diode bars measurement and testing equipment • Cutting and joining of special with indium- and AuSn solder • Chemical analysis of solid, liquid materials • Characterization and testing and gaseous substances with laser • Welding with filler material of diode lasers in the wavelength spectroscopy • Laser-arc hybrid technologies regime between 630 nm and • Spectroscopic monitoring • Product-oriented process 2.1 µm of welding processes optimization • Design and assembly • Fluorescence analysis • Multi-functional manufacturing of micro-optical systems • Quantification of protein processes • Fiber coupling for singlemode interactions using label-free laser • Design and implementation and multimode fibers scattering methods of processing heads • Automation of high-precision • In vivo diagnostics for online mo- • Sensor-based process control assembly processes for lasers nitoring of minimal invasive surgery • Computer-supported simulation and optical systems • Measurement of distances, profiles and optimization and shapes with laser triangulation • Multimedia training and information • Real time operation and automation systems

Solid State and Diode Lasers Plasma Technology Surface Treatment Dipl.-Ing. Dieter Hoffmann Dr. Willi Neff Dr. Konrad Wissenbach

• Development of solid state • Development of plasma based • Fabrication of load orientated layers and diode lasers EUV/XUV-sources by means of heat treatment, trans- • Development of fiber lasers • Development, construction and formation hardening, remelting, • Methods and components integration of components for alloying, dispersing and laser cladding for frequency doubling EUV/XUV-measuring systems • Development of maintenance • Optical design for lasers, beam guid- (microscopy, surface characterization, and repair processes for tools and ing and forming of laser radiation measurement of reflectivity …) components • Development of diode laser modules • Power generators for pulsed • Development of powder feeding and systems plasma formation nozzles and inside processing heads • Design and characterization • Process control and monitoring • Rapid prototyping and rapid manu- of optical components systems for spatially arranged facturing for production of metallic • Development of components systems based on micro seconds and ceramic parts and tools for solid state and diode lasers • Atmospheric pressure plasma for • Polishing, structuring, smoothing surface modification (sterilization and roughening by remelting metals, of packaging material, functiona- glass and plastics lization …) • Functionalising of thin layers • Generation of structured layers by remelting • Cleaning of surfaces

12 Fraunhofer ILT Annual Report 2007 Core Areas

Micro Technology Modelling and Simulation System Technology Dr. Arnold Gillner Prof. Dr. Wolfgang Schulz Dr. Stefan Kaierle

• Laser micro welding of metals and • Generation of EUV-radiation • Process monitoring and control combinations of dissimilar classes • Design of optical resonators for quality assurance of material for high power diode lasers • Process analysis and process • Laser welding of thermoplastics • Beam guiding, beam shaping development tools and thermoplastic elastomers with • Flow and heat transport in gases • Development of online sensors and diode and fiber lasers and melt control systems (e. g. seam tracking, • Laser micro soldering of metals • Movement of phase boundaries velocity measurement, positioning, and glasses • Dynamical models of removing, distance measurement and control, • Micro bonding of glass, semicon- cutting, welding and drilling multi-sensor technology and net- ductors and ceramics • Evaluation and visualization of data works) • Laser-assisted punching, bending from measurement and simulation • Automated testing of processing and embossing processes • Computational steering of results (e. g. systems for seam • Precision cutting and drilling of simulations evaluation) metals, ceramics, semiconductors • Numerical methods and codes, • Process trials and testing and diamonds finite elements and finite volumes • Feasibility studies • Micro structuring with Excimer in domains with free boundaries, • Pilot-run series and Nd:YAG lasers adaptive cross linking • Integration of laser technology into • Micro drilling with solid-state lasers • Diagnostics of laser radiation and existing production facilities • Ablation and structuring processes laser manufacturing processes • Remote and scanner applications using picosecond and femtosecond • Integrated processing heads lasers • CAD/CAM-supported laser • Nano structuring by interference- processing based processes and multi-photon • Offline path planning and simulation excitation • Conception and design of plants • Micro tool engineering in hard • Pilot plants metals, ceramics and diamonds • Control techniques for laser plants • Surface structuring for functional • Consulting, education and training component design • Marking and labeling • Cutting and perforating of paper, plastics and composites • Laser medicine for tissue therapy • Laser applications for biotechnology • Cell manipulation and biophotonic analysis techniques • Photochemical processes • Consulting, feasibility studies, and development of processes for laser-based manufacturing • Process qualification under close-to-real production conditions

Fraunhofer ILT Annual Report 2007 13 Services

Services Cooperations with R&D-Partners

The services of the Fraunhofer Institute The Fraunhofer Institute for Laser for Laser Technology ILT are continually Technology ILT is cooperating with being adapted to the practical require- R&D-partners in different ways: ments of industry and include the • realization of bilateral, company solution of manufacturing problems specific R&D-projects with and as well as the realization of test series. without public support In detail this means: (contract for work and services) • development of laser beam sources • participation of companies in • manufacturing and assembling public-funded cooperative projects technology (cofinancing contract) • pulsed power supplies and control • production of test, pilot and technology prototype series by Fraunhofer ILT • beam guiding and forming to determine the reliability of • development, set-up and testing the process and minimize the of pilot plants starting risk • process development (contract for work and services) • process monitoring and control • companies with guest status at • model and test series Fraunhofer ILT • integration of laser technology into (special cooperation contracts) already existing production plants • X-ray and plasma systems By means of cooperation with other research organizations and specialized companies the Fraunhofer Institute for Laser Technology offers solutions even in the case of interdisciplinary tasks. A special advantage hereby consists in the direct access to the large resources of the Fraunhofer Society.

During the implementation phase of new laser processes and products, companies can acquire ‘guest status’ at the Fraunhofer Institute for Laser Technology and use the equipment, infrastructure and know-how of the institute as well as install their own systems.

14 Fraunhofer ILT Annual Report 2007 Services

• sensors for process control in laser Facilities material processing Fraunhofer ILT abroad • direct-writing and laser-PVD stations The usable floor space at the Fraun- • clean rooms for assembly of diode Since its foundation, Fraunhofer ILT hofer Institute for Laser Technology ILT lasers, diode laser systems and has been involved in many international amounts to more than 10,000 m2. diode pumped solid state lasers cooperations. The objective of these • live sience laboratory with S1 and cooperations is to recognize new Technical Infrastructure S2 classification trends and current developments and The technical infrastructure of the • devices for process diagnostics and to acquire further know-how. The institute includes a mechanical and high speed video analysis customers of Fraunhofer ILT can directly electronic workshop, a metallurgic • laser spectroscopic systems for the benefit from this. Fraunhofer ILT carries laboratory, a photographic laboratory, chemical analysis of solid, liquid and out bilateral projects as well as interna- a laboratory for optical metrology as gaseous materials tional cooperative projects with foreign well as a department for design and • laser triangulation sensors for companies and subsidiaries of German construction. The Fraunhofer ILT also distance and contour measurement companies abroad. These companies has a video conference room and a • laser coordinate measuring machine can also contact Fraunhofer ILT computer network. • confocal laser scanning microscopy through: • international subsidiaries of Scientific Infrastructure Fraunhofer ILT The scientific infrastructure includes • foreign cooperation partners of a library with international literature, Fraunhofer ILT patent and literature data bases as • liaison offices of the Fraunhofer well as programmes for calculation Society abroad of scientific problems and data bases for process documentation.

Equipment The equipment of the Fraunhofer Institute for Laser Technology ILT is permanently being adapted to the state-of-the-art. At present, essential components are:

• CO2-lasers up to 20 kW • lamps and diode pumped solid © AVIA-Luftbild, Aachen state lasers up to 8 kw Dipl.-Ing. Martin Jochum • disc lasers up to 8 kW • fiber lasers up to 4 kW • diode laser systems up to 3 kW • SLAB laser • excimer lasers • ultra short pulse laser • broadband tunable laser • five-axis gantry systems • three-axis processing stations • beam guiding systems • robot systems

Fraunhofer ILT Annual Report 2007 15 Facts and Figures

Employees

Employees at the Fraunhofer ILT 2007 number

Personnel 137 - Scientists and engineers 81 - Technical staff 35 - Administrative staff 21 Other employees 123 - Undergraduate assistants 113 - External employees 7 - Trainees 3 Total number of employees at the Fraunhofer ILT 260

• 3 members of staff completed their doctorates • 29 undergraduates carried out their final year projects at the Fraunhofer ILT

Employees 2007

44 % Undergraduate assistants

8 % Administrative staff

13 % Technical staff

4 % External employees, trainees • 6 Mitarbeiter haben ihre Promotion abgeschlossen 31 % Scientists/engineers • 26 Studenten haben ihre Diplomarbeit am Fraunhofer ILT durchgeführt

16 Fraunhofer ILT Annual Report 2007 Facts and Figures

Revenues and Expenses

Expenses 2007 Mill. EUR

- Staff costs 8,5 - Material costs 9,6 Expenses operating budget 18,1

Investments 3,8

Revenues 2007 Mill. EUR

- Industrial revenues 8,0 - Additional financing from Federal Government, States and the EU 6,3 - Basic financing from the Fraunhofer-Gesellschaft 3,8 Revenues operating budget 18,1 - Revenues from projects abroad (already included in total) 2,1

Investment revenues from industry 0,5

Fraunhofer industry ρInd 47,2 %

Expenses 2007 (100 %) Revenues 2007 (100 %)

44 % Material costs 35 % Additional financing from Federal Government, States and EU

17 % Investments 21 % Basic financing from the Fraunhofer-Gesellschaft

39 % Staff costs 44 % Industrial revenues (without investments)

Fraunhofer ILT Annual Report 2007 17 Facts and Figures

Budget Growth

The following graph illustrates the budget trend over the last 8 years.

Project revenues - public funding Project revenues - industrial funding Basic financing by Fraunhofer

18,6 18,0 18,1 17,5 17,1 17,4 16,4

14,8

18 Fraunhofer ILT Annual Report 2007 References

March 2008 Printed with the kind permission of our partners.

The companies listed here represent a selection of the Fraunhofer ILT’s many clients.

Fraunhofer ILT Annual Report 2007 19 Fraunhofer USA Center for Laser Technology CLT

The American partner universities’ Short Profile interest concentrates on: • Using the competence of the The Fraunhofer Center for Laser Tech- Fraunhofer Institutes nology CLT, located in Plymouth, • Using the experience in the Michigan, has a 1250 m2 development introduction of new technologies center housing $9 million worth of the into the market most varied, leading edge laser equip- • Providing the connection between ment in North America. This area has industry and university established itself as the center for laser • Providing practical training for production, system integration and students and graduate students industrial users in the USA. The CLT develops powerful, high- brilliance fiber lasers in collaboration The on-going goals are: with the University of Michigan. The • Integration in scientific and basic research is carried out at the industrial development in the USA university, while Fraunhofer undertakes • Accumulation of know-how at the the development of high-brilliance German parent institute through pump sources, system integration, student exchange programs and prototype construction and application early recognition of trends led by tests. In this context, the CLT has the USA implemented new technologies and • Know-how growth at CLT through manufacturing methods that make close cooperation with the University diode lasers comparable to solid-state of Michigan and the Wayne State lasers in terms of their performance. University as well as other leading The two establishments are currently US universities working together on a number of • Local provision of services to research projects in this area. international companies on both continents The CLT is also collaborating with • Strengthening position in the Wayne State University to develop R&D market cost-efficient manufacturing processes for alternative energy production and The central philosophy of Fraunhofer storage. The focus is on solar cells USA is the creation of a German- and lithium-ion batteries, which are American joint venture where give currently going through a huge de- and take occur in harmony. The win-win velopment spurt due to the trend situation is an essential prerequisite towards hybrid vehicles. Laser-induced for both sides. The Fraunhofer separation and joining of similar, but Gesellschaft is always interested in also dissimilar, classes of material such considering and trying to develop as metal and plastic form the techno- relationships on the American side logical basis for these processes. that strengthen mutually.

20 Fraunhofer ILT Annual Report 2007 Fraunhofer USA Center for Laser Technology CLT

In 2001, the Visotek company was spun off from the Fraunhofer CLT in Equipment Contact order to market the center’s results in the field of fiber-coupled high-power Current equipment in the CLT lab con- lasers and specialized lens systems. sists of: CO2 lasers with up to 8 kW 2007 saw the launch of Arbor Photo- power, Nd:YAG laser from 250 W to nics with the support of the University 4.4 kW, diode lasers from 30 W to of Michigan to market developments 3 kW, frequency trebled Nd:YAG laser in the area of flexible fiber lasers with and excimer laser, a number of special diffraction-limited beam quality and and hybrid optics, a series of 3, 5 and high pulse outputs. 6 axes systems, as well as several Dr. Stefan Heinemann robots. Director

46025 Port Street Services Plymouth References Michigan 48170 The CLT offers services in the field USA of laser processing, the development • US Air Force Research Laboratories of optical components and special • Office of Naval Research Phone +1 734 354-6300 laser systems. This covers the entire • Michigan Lifescience Corridor Extension -210 spectrum from feasibility studies, • Alcan Fax +1 734 354-3335 process development to pre-series • Borg Warner Automotive development as well as prototype • Dana Corporation [email protected] production of laser beam sources and • DaimlerChrysler www.clt.fraunhofer.com laser systems which are ready to use. • Ford Motor Company As an independent institution small • General Motors and mid-sized companies are given the • Hemlock Semiconductors opportunity to develop and test their • Nuvonyx processes on Fraunhofer machines • LASAG with the help of Fraunhofer personnel. • PRC It is also possible to develop and test • Rofin Sinar complete systems at the CLT. Our • Spectra Physics customers come from the automobile • Siemens VDO industry, construction industry, ship • Trumpf building and medical engineering. • Visteon

Employees Operating Budget 2007*

Both Germans and Americans are Mio. US$ employed at the CLT. The goal is to rotate German employees so that the Operating budget 2.4 collected experience can be brought - Staff costs 1.1 over to the parent institutes and to - Material costs 1.3 offer German employees the opportu- *Post-calculation has not occurred yet nity to become further qualified during their stay in the USA. Furthermore, students from the Technical University in Aachen write their diploma thesis in the USA.

Fraunhofer ILT Annual Report 2007 21 Coopération Laser Franco-Allemande CLFA

The CLFA is actively participating in the Short Profile realization of European research and is a result of increasing link of application At the CLFA in Paris, the Fraunhofer oriented research and development in Institute for Laser Technology ILT has the field of laser technology in Europe. been cooperating since 1997 with leading French research organizations, The cooperation of the Fraunhofer ILT including ARMINES, the École Natio- with the French partners contributes nale Supérieure des Mines de Paris to the improvement of the presence of ENSMP, the École Nationale Supérieure the Fraunhofer Gesellschaft in Europe de Mécanique et des Microtechniques with the advantages for the French ENSMM in Besancon,¸ the engineer uni- and German sides equally taken into versity Louis de Broglie in Rennes and consideration. On an international scale other major laser application centers this cooperation further strengthens the in France. Multidisciplinary teams of leading position of European industry specialists from Germany and France in the laser supported manufacturing work together on the transfer of laser process. assisted manufacturing processes to European industry. The Coopération The French partners’ interests concen- Laser Franco-Allemande is a member trate on: of the Club Laser et Procédés, the • Using the competence of the French association of laser manufac- Fraunhofer ILT for French companies turers and users. • Using the experience of the Fraun- hofer ILT in the introduction of new The on-going goals of the CLFA are: technologies • Integration into scientific and • Providing the connection between industrial development in France industry and university with practical • Growth in know-how by faster training for students and graduate recognition of trends in the fields students of European laser and production technology Together with their French cooperation • Strengthening the position in the partners, ILT staff at the CLFA recently R&D market spun off a new company called Poly- • Assembly of a European competence Shape, which provides French custo- center for laser technology mers with services in the field of ge- • Increase of mobility and qualification nerative manufacturing processes. level of employees Its technology was presented to interested industrial partners at a joint stand during the Paris Air Show at Le Bourget in June 2007.

22 Fraunhofer ILT Annual Report 2007 Coopération Laser Franco-Allemande CLFA

Services Equipment Contact

The CLFA offers services in the field of In addition to the technical resources laser material processing. This covers available at the Fraunhofer ILT in the entire spectrum from application Germany, the CLFA possesses its oriented fundamental research and own infrastructure at the Centre des training, feasibility studies and process Matériaux Pierre-Marie Fourt, an out- development to pre-series development station of the Ecole des Mines de Paris and system integration. Small and mid- based in Evry, south of Paris. Facilities sized companies have the opportunity include access to the center’s material Dr. Wolfgang Knapp here to get to know and test laser analysis laboratories. The technical Director technology in an independent system. infrastructure of other French partners The open development platform allows can also be shared on a project- or CLFA c/o Armines the French customers to test and qua- customer-specific basis. 60 Boulevard Saint Michel lify new laser supported manufacturing 75272 PARIS Cedex 6 processes. France

Locations Phone +33 1 4051-9476 Fax +33 1 4634-2305 Employees Paris - at the École Nationale Supérieure des Mines de Paris ENSMP, in central [email protected] At the CLFA employees from France Paris. www.ilt.fraunhofer.de/clfa.html and Germany work together. A mutual exchange of personnel occurs between Evry - on the premises of the Centre Aachen and Paris for joint projects. des Matériaux Pierre-Marie Fourt, The employees therefore have the roughly 40 km south of Paris. opportunity to improve their competence especially with regard to mobility and international project management.

Fraunhofer ILT Annual Report 2007 23 Fraunhofer Alliance Surface Engineering and Photonics VOP

Competence by Networking Fraunhofer Institute for Physical Measurement Techniques IPM Six Fraunhofer Institutes cooperate in the Network Surface Engineering and The Fraunhofer IPM develops optical Photonics VOP. Complementary com- systems for applications in spectros- petencies allow to adapt the research copy and light exposure technology. activities to the rapid technological A major focus is the realisation of highly progress in all industrial application dynamical systems. Besides a rapid fields in a permanent, apace and flexible activation, they require special compe- way. Co-ordinated strategies, in line tencies in signal processing as realised with the current needs of the market, through robust and low maintenance create synergy effects and provide measurement systems for the infra- a larger service for the benefit of the structure monitoring of high speed customers. roads.

Fraunhofer Institute for Electron Fraunhofer Institute for Beam and Plasma Technology FEP Laser Technology ILT

The ambition of FEP is the research In the area of laser technology, the and development of innovative interactive relationship between laser processes for the utilisation of high development and laser applications is performance electron beams and of prime importance. New lasers allow vacuum sealed plasmas for surface new applications, and new applications technology. Priority is given to problems set the stage for new laser systems. like process monitoring, quality control, This is why the Fraunhofer ILT is conti- reproducibility, scaling, and profitability. nually expanding its core competencies through close cooperation with leading laser manufacturers and innovative laser consumers.

Above: Fraunhofer FEP Middle: Fraunhofer IPM Below: Fraunhofer ILT

24 Fraunhofer ILT Annual Report 2007 Fraunhofer Network Surface Engineering and Photonics VOP

Fraunhofer Institute for Surface Fraunhofer Institute for Material Engineering and Thin Films IST and Beam Technology IWS

As an industry oriented R&D service The Fraunhofer IWS is conducting centre, the Fraunhofer Institute for research in the areas of laser techno- Surface Engineering and Thin Films IST logy (e.g. laser beam welding, cutting, is pooling competencies in the areas hardening), surface technology (e.g. film deposition, coating application build-up welding), micro machining as and film characterization. Presently, the well as thin film and nano technology. institute is operating in the following The integration of material testing and business fields: mechanical and auto- characterisation into research and motive engineering; tools; energy; development constitutes and upgrades glass and facade; optics; information the IWS spectrum. and communication; life science and ecology.

Contact und Coordination

Fraunhofer Institute for Applied Speaker of the Network Optics and Precision Engineering IOF Prof. Dr. Eckhard Beyer

The core of the research activity of Coordination Fraunhofer IOF is optical systems Udo Klotzbach engineering aimed at a steady improve- Telephone: ++49 (0)351 / 2583252 ment of light control. The institute's [email protected] focus is on multifunctional optical www.vop.fraunhofer.de coatings, optical measurement systems, micro-optical systems, systems for the The Institutes characterisation of optics and compo- www.fep.fraunhofer.de nents for precision mechanics assem- www.ipm.fraunhofer.de blies and systems. www.ilt.fraunhofer.de www.ist.fraunhofer.de www.iof.fraunhofer.de IST www.iws.fraunhofer.de

FEP ILT

Above: Fraunhofer IST IWS Middle: Fraunhofer IOF Below: Fraunhofer IWS

IOF

IPM

Fraunhofer ILT Annual Report 2007 25 The Fraunhofer-Gesellschaft at a Glance

At present, the Fraunhofer-Gesellschaft • Process engineering The Fraunhofer-Gesellschaft maintains more than 80 research units, • Energy and construction including 56 Fraunhofer Institutes, at engineering, environmental and Research of practical utility lies at the 40 different locations in Germany. The health research heart of all activities pursued by the majority of the 13,000 staff are qualified • Technical/economic studies, Fraunhofer-Gesellschaft. Founded in scientists and engineers, who work information transfer 1949, the research organization under- with an annual research budget of 1.3 takes applied research that drives eco- billion euros. Of this sum, more than nomic development and serves the 1 billion euros is generated through wider benefit of society. Its services are contract research. Two thirds of the Target Groups solicited by customers and contractual Fraunhofer-Gesellschaft’s contract re- partners in industry, the service sector search revenue is derived from contracts The Fraunhofer-Gesellschaft is commit- and public administration. The orga- with industry and from publicly financed ted to working for the economy as a nization also accepts commissions from research projects. Only one third is whole, for individual businesses and German federal and Länder ministries contributed by the German federal for society. The targets and benefi- and government departments to par- and Länder governments in the form ciaries of our research activities are: ticipate in future-oriented research proof institutional funding, enabling the • The Economy: Small, medium-sized jects with the aim of finding innovative institutes to work ahead on solutions and large companies from industry solutions to issues concerning the indus- to problems that will not become and service sectors can all benefit trial economy and society in general. acutely relevant to industry and society from contract research. The Fraun- until five or ten years from now. hofer-Gesellschaft develops con- Applied research has a knock-on effect crete, practical and innovative that extends beyond the direct benefits Affiliated research centers and represen- solutions and furthers the application perceived by the customer: Through tative offices in Europe, the USA and of new technologies.The Fraun- their research and development work, Asia provide contact with the regions hofer-Gesellschaft is an important the Fraunhofer Institutes help to rein- of greatest importance to present and ‘supplier’ of innovative know-how force the competitive strength of the future scientific progress and economic to small and medium-sized com- economy in their local region, and development. panies (SMEs) not equipped with throughout Germany and Europe. They their own R&D department. do so by promoting innovation, accele- The Fraunhofer-Gesellschaft is a recog- • Country and society: Strategic rating technological progress, improv- nized non-profit organization which research projects are carried out at ing the acceptance of new technologies, takes its name from Joseph von Fraun- federal and state level, promoting and not least by disseminating their hofer (1787-1826), the illustrious key technologies or innovations in knowledge and helping to train the Munich researcher, inventor and entre- fields of particular public interest, urgently needed future generation of preneur. e.g. environmental protection, scientists and engineers. energy technologies and preven- tative health care. The Fraunhofer- As an employer, the Fraunhofer-Gesell- Gesellschaft also participates in schaft offers its staff the opportunity to Fields of Research technology programs initiated by develop the professional and personal the European Union. skills that will allow them to take up The Fraunhofer-Gesellschaft concentrates positions of responsibility within their on research in the following fields: institute, in other scientific domains, in • Materials technology, component industry and in society. Students work- behavior ing at the Fraunhofer Institutes have • Production and manufacturing excellent prospects of starting and technology developing a career in industry by virtue • Information and communication of the practical training and experience technology they have acquired. • Microelectronics, microsystems engineering • Sensor systems, testing technology

26 Fraunhofer ILT Annual Report 2007 The Fraunhofer-Gesellschaft at a Glance

Range of Services The Advantages of Contract Research Facilities in Germany Research The Fraunhofer-Gesellschaft develops products and services to full maturity. Cooperation between all the Fraunho- We work closely with our clients to fer institutes means that our clients create individual solutions, combining have access to a large number of the efforts of several Fraunhofer insti- experts covering a wide range of com- tutes if necessary, in order to develop petencies. Thanks to common quality more complex system solutions. The standards and professional project services provided by the Fraunhofer- management, the Fraunhofer institutes Gesellschaft are: ensure that research projects achieve • Product optimization and results that can be relied on. Our insti- development through to prototype tutes are equipped with up-to-date manufacture laboratory technology, making them • Optimization and development attractive to companies of all sizes and of technologies and production from all industrial sectors. As a strong processes community, we can provide our part- • Support for the introduction of ners with reliability and economic new technologies via: benefits: the Fraunhofer-Gesellschaft - Testing in demonstration centers can bring the knowledge already using highly advanced equipment gained from cost-intensive preliminary - In-house training for the staff research into joint projects. involved - On-going support, also subsequent to the introduction of new processes and products • Assistance in assessing new technologies via: - Feasibility studies - Market analyses - Trend analyses - Life cycle analyses - Evaluation of cost-effectiveness • Supplementary services, e.g.: - Advice on funding, especially for SMEs - Testing services and quality validation

Fraunhofer ILT Annual Report 2007 27 Laser Technology at RWTH Aachen

Jointly shaping the future Chair for Laser Technology LLT

The RWTH Aachen University Chairs The department of laser technology at for Laser Technology LLT and the Tech- RWTH Aachen University has been en- nology of Optical Systems TOS, along gaged in application-oriented research with the study and research depart- and development in the fields of inte- ment for the non-linear dynamics of grated optics, integrative production, laser production methods NLD, repre- ablation - modification - diagnosis sent an outstanding cluster of exper- (AMD), drilling and generative processes tise in the field of optical technologies. since 1985. Its activities in integrated This permits supercritical treatment of optics focus on investigating the inte- basic and application-related research gration of high-power diode lasers topics. The close cooperation with the with waveguide lasers and beam-shap- Fraunhofer Institute for Laser Technolo- ing optical components, as well as the gy ILT not only permits industrial con- development of novel integrated power tract research on the basis of sound lasers. The Cluster of Excellence »In- fundamental knowledge, but also pro- tegrative Production Technology for vides new stimuli for the advanced High-Wage Countries«, in which the development of optical methods, com- LLT is involved, is working largely on ponents and systems. The synergy of the integration of optical technologies infrastructure and know-how is put to into production processes and on the active use under a single roof. production of optical systems.

This structure particularly benefits up- Ultra-short pulsed lasers are being and-coming young scientists and engi- tested in basic experiments and used neers. Knowledge of current industrial to process nano and micro components and scientific requirements in the opti- of practical relevance by ablation, mo- cal technologies flows directly into the dification or melting. Single-pulse, per- planning of the curriculum. Furthermore, cussion and spiral drilling techniques undergraduates and postgraduate as well as trepanning are being used to students can put their theoretical know- process metals and multi-layer systems ledge into practice through project mostly made up of metals and ceramics. work at the three chairs and at the This technology is useful for drilling Fraunhofer ILT. University courses are holes in turbine blades for the aerospace drawn up jointly as well. The interdis- industry, for example. Work in the field ciplinary collaboration between phy- of generative processes focuses mainly sicians and engineers, for instance, on new materials, smaller structures, has resulted in a university seminar for higher build-up rates, micro coating, advanced dental training being set up. process monitoring and control, and Teaching, research and innovation - the development and enhancement of those are the bricks with which the the university’s own plants and systems. three university departments and the Fraunhofer ILT are building the future. Contact Prof. Dr. Reinhart Poprawe M. A. Director of the department Phone +49 241 8906-109 Fax +49 241 8906-121 [email protected]

Academic director Dr. Ingomar Kelbassa (deputy director) Phone +49 241 8906-143 [email protected] 28 Fraunhofer ILT Annual Report 2007 Laser Technology at RWTH Aachen

Chair for the Technology Study and research department of Optical Systems TOS for the non linear dynamics of laser production methods NLD By establishing the Chair for the Tech- nology of Optical Systems in 2004, Founded in 2005, the study and re- RWTH Aachen accorded recognition to search department for the non linear the increasingly central role of highly dynamics of laser production methods developed optical systems in manufac- NLD explores the basic principles of turing, the IT industries and the life optical technology, with emphasis on sciences. Research activities focus on modeling and simulation. the development and integration of optical components and systems for Mathematical, physical and experimen- laser beam sources and laser devices. tal methods are being applied and enhanced to investigate technical Highly corrected focusing systems for systems. The application of mathema- a high laser output, beam homogeni- tical models is helping to achieve a zation facilities and innovative beam better understanding of dynamic inter- shaping systems are all key compo- relationships and to create new pro- nents of laser systems used in produc- cess engineering concepts. The results tion engineering. The performance of these analyses are made available of fiber lasers and diode-pumped solid- to industrial partners in the form of state lasers, for instance, is determined practical applications in collaboration by optical coupling and pump light with the Fraunhofer Institute for Laser homogenizers. Waveguide structures Technology ILT. for frequency conversion are yet another topic of research. In the area of The main educational objective is to high-power diode lasers, micro- and teach a scientific, methodological macro-optical components are deve- approach to modeling on the basis of loped and combined to form complete practical examples. Models are derived systems. In addition, assembly tech- from the experimental diagnosis of niques are optimized. laser manufacturing processes and the numerical calculation of selected Contact model tasks. The diagnostic findings Prof. Dr. Peter Loosen and the numerical calculations are Director of the department then used to mathematically reduce Phone + 49 241 8906-162 the model equations. The solution Fax +49 241 8906-121 characteristics of the reduced equations [email protected] are fully contained in the solutions to the starting equations, and are not unnecessarily complex.

Contact Prof. Dr. Wolfgang Schulz Director of the study and research department Phone +49 241 8906-204 Fax +49 241 8906-121 [email protected]

Fraunhofer ILT Annual Report 2007 29 Cluster of Excellence »Integrative Production Technology for High-Wage Countries«

A similar divergence is evident with res- Cluster of Excellence pect to the second factor, that of planning efficiency. Manufacturers in high- In the Cluster of Excellence »Integrative wage countries aim to continuously Production Technology for High-Wage optimize their processes, using corres- Countries« process engineers and pondingly sophisticated, capital-intensive materials scientists based in Aachen planning methods and instruments, are developing new concepts and and technologically superior production technologies offering a sustainable systems. In low-wage countries, by approach to industrial manufacturing. contrast, production needs are better served by simple, robust, supply-chain- A total of 18 chairs and institutes oriented processes. of RWTH Aachen, together with the Fraunhofer Institutes for Laser Techno- In order to maintain a sustainable com- logy ILT and for Production Technology petitive advantage for production sites IPT, are working on this project, which in high-wage countries, it is no longer in the first instance will run until the sufficient to aim for a better position end of 2011. that maximizes economies of scale and scope or reconciles the opposing Funding of approx. 40 million euros extremes of a planning-oriented and a has been granted to this Cluster of value-oriented approach. Instead, the Excellence, an initiative that unites the goal of research must be to cancel out largest number of research groups in these opposite poles as far as possible. Europe devoted to the objective of Ways must be found to allow a greater preserving manufacturing activities in variability of products while at the high-wage countries. same time being able to manufacture them at cost levels equivalent to mass production. This calls for value-optimized supply chains suited to each product, Production in high-wage countries without excessive planning overheads The production dilemma: Scale/scope that would compromise their cost- vs. planning-oriented/value-oriented, The competition between manufac- effectiveness. source: WZL Aachen. turers in high-wage and low-wage countries typically manifests itself as Tomorrow’s production technology a two-dimensional problem, opposing therefore requires a thoroughly new production efficiency and planning understanding of these elementary, efficiency. interrelated factors.

In each case there are divergent approaches. With respect to production efficiency, low-wage countries tend Integrative production to focus exclusively on economies of scale, whereas high-wage countries The Cluster of Excellence »Integrative are obliged to seek a balanced equili- Production Technology for High-Wage brium between scale and scope, in Countries« is aiming for the long-term other words being able to satisfy cus- goal of increasing the competitiveness tomer requirements in respect of a of German production technology. The particular product while at the same overarching hypothetical solution lies time attaining a minimum production in achieving the next higher level of volume. production integration.

30 Fraunhofer ILT Annual Report 2007 Cluster of Excellence »Integrative Production Technology for High-Wage Countries«

Individualized production Self-optimizing production

Individualized production involves Self-optimization is a way of optimiz- allowing for a high degree of product ing production processes without variability and dynamics at costs equi- increasing the volume of upstream valent to those of mass production. planning activities. In the cluster Concepts are being developed that will domain Self-optimizing Production, enable the optimum combination and methods and technologies are being configuration of the different elements developed to increase the cognitive in a production system to be identified. capabilities of production systems such At the same time, advanced manufac- as a laser cutting plant or an assembly turing technologies such as selective system for optical components. laser melting (SLM) are being further refined, and will eventually enable one-piece-flow concepts to be implemented at the same costs as mass Contacts production. Fraunhofer ILT The official opening of the Dipl.-Phys. Christian Hinke Cluster of Excellence in October Phone: +49 241 8906-352 2006, source: WZL Aachen. Virtual production [email protected]

The introduction of greater flexibility in Cluster of Exellence Office production processes necessarily results Dr. Lutz Schapp in an increased volume of preparatory Phone: +49 241 80-27590 and planning activities. In the cluster [email protected] domain Virtual Production Systems, the aim is therefore to improve planning quality while simultaneously reducing the quantity of work involved. This is being done by developing discrete models representing, for instance, laser welding processes and materials, linking them together and integrating them in a virtual supply chain.

Hybrid production

By integrating a number of discrete processes in a single hybrid process, it is possible to reduce the length of supply chains and hence organize them more efficiently. In the cluster domain Hybrid Production, methods are being investigated that will enable supply chains to be systematically hybridized, and hybrid technologies such as laser-assisted incremental sheet Source: WZL Aachen. forming are being developed.

Fraunhofer ILT Annual Report 2007 31 European Laser Institute ELI

Furthermore, the international co- Short Profile operation of industry and research, especially in the field of EU research The European Laser Institute was foun- support, is forced by ELI. Amongst ded in 2003 through an EU-funded ini- others, ELI creates adequate platforms tiative. The ELI mission is to strengthen by organizing conferences, workshops, and further enhance Europe’s position summerschools etc. In the future, this in the field of laser technology. In addi- is supported by the cooperation with tion, ELI aims to raise public awareness the respective representations (e. g. of the significance and prospects of the EPIC, AILU, WLT). A strong cooperation European laser technology industry. ELI with the Laser Institute of America is a network composed of more than (LIA) already exists in the organization 20 leading research facilities including of international conferences (ICALEO, the Fraunhofer ILT as well as small and PICALO, ALAW) as well as the Journal medium-sized companies. This means of Laser Applications (JLA). that in addition to its participation in regional and national competence networks, as an ELI member the Fraunhofer ILT is also part of an influential, Euro- Executive Commitee pean-level laser technology network. The members of the committee representing the ELI are: • Dr. Stefan Kaierle (chairman), Fraunhofer ILT, Germany • Abdelkrim Chehaibou, Institut de Soudure, France • Dr. François De Schutter, Lasercentrum Vlaanderen, Belgium • Dr. Paul Hilton, TWI, Great Britain • Dr. Wolfgang Knapp, CLFA, France • Prof. Dr. Veli Kujanpää, Lappeenranta University of Technology, Finland • Prof. Dr. José Luis Ocaña, Centro Láser U.P.M., Spain

Contact

Dr. Stefan Kaierle Phone +49 241 8906-212 Fax +49 241 8906-121 [email protected]

32 Fraunhofer ILT Annual Report 2007 PhotonAix e. V. Competence Network for Optical Technologies

Short Profile Highlights 2007

PhotonAix, the Competence Network Besides participating in Photonics West for Optical Technologies and Systems, 2007 in San Jose, USA, and LASER was founded in 2002 by the Fraunhofer 2007 in Munich as a joint exhibitor Institute for Laser Technology ILT, the with the other German competence Fraunhofer Institute for Production networks for optical technologies, the Technologies IPT and the Laboratory major events of 2007 were the Euro- of Machine Tools and Production pean technology platform Photonics21 Engineering WZL of the RWTH Aachen. and the formation of the North Rhine- Aachen-based Photon Aix and eight Westphalian initiative NRW-Photonics. other regional competence networks in the field of optical technologies The objective of the technology plat- made up of more than 400 members form Photonics21 is to further streng- from research and industry are concen- then Europe’s leading role in the field trating their skills with the mutual goal of optical technologies and to coordi- of promoting optical technologies in nate joint research and development their respective regions. activities.

These networks represent the full A study carried out with the European range of »Made in Germany« optical Commission and published in December technologies, from laser-based mate- 2007 forecasts continued success for rials processing and biophotonics to optical technologies in the future. transportation and aerospace applica- Annual revenues generated by optical tions. The competence networks are technologies in Europe, currently at primarily engaged in providing services 49 billion euros, are predicted to grow such as technology management, at an average of 7.6 % per year until start-up consulting, regional techno- 2015. About 250,000 people in Europe logy and industry marketing, quality are already working in the field of op- training and education initiatives, and tical technology today. fostering communications within the network. The regional concentration of expertise leads to practical, real-time problem resolution and an accelerated Contact transfer of research results into market- ready products. PhotonAix e. V. Dipl.-Phys. Christian Hinke Managing director Steinbachstraße 15 52074 Aachen

Phone +49 241 8906-352 Fax +49 241 8906-121 [email protected] www.photonaix.de

Fraunhofer ILT Annual Report 2007 33 Research Results 2007

Some Special Research Results from the Business Areas of Fraunhofer ILT

Laser and Plasma Sources 35 - 60

Laser Material Processing 61 - 106

Laser Plant and System Technology 107 - 118

Laser Measurement and Testing Technology 119 - 139

Note from Institute Director We would like to point out that the publication of the following industry projects has been coordinated with our customers. In principle, industry projects are subject to the strictest obligation to maintain secrecy. We would like to take this time to thank our industrial partners for their willing- ness to have their reports listed published.

34 Fraunhofer ILT Annual Report 2007 Laser and Plasma Sources Business Area Laser and Plasma Sources

This business area encompasses the development of diode laser modules and systems as well as diode-pumped solid-state lasers with different resonator structures (stab,slab,fiber), the design of new diode laser structures, the microassembly of diode lasers and optical components, and the development of plasma systems.

For more than 10 years spinn-offs of the Fraunhofer ILT are set up in the framework of some projects. In cooperation with the Fraunhofer IAF new structures are being designed which permit the manufacture of diode lasers demonstrating higher beam quality. The business area continues to enjoy a unique reputation in the assembly of high-power diode lasers and in particular the installation of automated assembly and test facilities. Work in Automated assembly technology the plasma technology sphere focuses for miniaturized lasers for materials processing. Microslab demonstrator on the development of EUV beam on a ceramic substrate. sources for semiconductor lithography. The main target markets for the business area as a whole are laser machining, medical engineering and metrology, along with the component market for information and communications technology.

36 Fraunhofer ILT Annual Report 2007 Contents

Vaporizing heat sink Energy scaling of pulsed for diode lasers 38 Nd:YGG-based laser beam sources at 935 nm 50 Single-mode fiber-coupling of frequency-stabilized tapered lasers 39 Broadband tunable Ti:sapphire laser with nanosecond pulses 51 Modeling of frequency doubling in periodically poled non-linear Compact frequency converter crystals 40 for tunable laser radiation 52

Superpulsed diode lasers for Q-switched Nd:YAG laser with an laser materials processing 41 average output in the kW range for surface processing 53 Fiber-coupled diode lasers for pumping fiber lasers 42 Linearly polarized fiber lasers with high average output 54 Transformation optics for de-coating metal parts by high-power laser 43 White light interferometer for characterizing optical coatings Automated assembly technology for ultra-short pulse lasers 55 for miniaturized lasers for materials processing 44 Generating sub-ns laser pulses of variable pulse duration with InnoSlab-based amplifier pulse energy in the mJ range 56 for sub-ns laser pulses with an energy of 100 mJ 45 Probe for the analysis of a laser-induced plasma 57 Femtosecond InnoSlab amplifiers of high average output 46 Ray tracing in inhomogeneous media 58 Highly efficient laser pulse source for a space-based LIDAR system 47 Surface analysis with extreme ultraviolet radiation for the Diode-seeded fiber amplifier characterization of thin films 59 for LIDAR applications 48 Data transmission with Integrated frequency-stabilizing low latency 60 electronics for LIDAR-based pulsed lasers in aerospace 49

Fraunhofer ILT Annual Report 2007 37 Vaporizing heat sink for diode lasers

designed on the basis of flow tests. Task The heat sink prototypes are to be accurately examined using a specially Heat management for actively cooled developed test rig that predetermines industrial diode laser systems calls for a the heat flow, registers the tempera- high flow of heat and a low temperature at several positions on the heat ture difference between the cooled sur- sink, and measures the flow rate and face and the cooling medium. It is ad- the temperature of the cooling medium. vantageous to have as small a cooling medium flow rate as possible in order to avoid erosion and corrosion in the heat sink, as these shorten the service Results and Applications life of the heat sink and thus also of the diode laser. These requirements can be Investigations of various prototypes of met by utilizing the vaporization process a vaporizing heat sink and various cool- as a cooling principle, given that the ing media are being carried out using evaporation of a liquid extracts large the purpose-built test rig in order to quantities of heat from its environment verify their influence on the vaporiza- in the right conditions. tion process. In these tests, the consis- tency of the cooled surface and the geometry of the vaporization chamber are varied. The heat sinks are being Method further optimized based on the results of this investigation, and can now In accordance with the requirements, achieve a heat flow of 40 W on a sur- a selection of different cooling media face measuring 2 x 10 mm2 with a is assembled and then further narrowed temperature difference of 20 K bet- down in preliminary tests. The heat ween the cooling medium and the sink prototypes, whose dimensions are cooled surface. It is hoped to achieve similar to those of commercially avai- a cooling capacity of 80 W in a sub- lable microchannel heat sinks, are sequent stage of development.

Test rig for examining different prototypes of a vaporizing heat sink. Contacts

Dipl. Phys. M. Werner, Tel.:-423 [email protected] Dr. K. Boucke, Tel.: -132 [email protected]

38 Fraunhofer ILT Annual Report 2007 Single-mode fiber-coupling of frequency-stabilized tapered lasers

little influence as possible on the effi- Task ciency of the SMF coupling process. The optical fiber-coupling and frequen- Numerous applications require fre- cy-stabilizing elements are mounted quency-stabilized diode laser modules using silica glass and Macor compo- that enable the laser beam to be nents, and fixed with a UV-hardened coupled into a single-mode fiber adhesive once they have been adjusted. (SMF). Some examples of such applications are pump sources for solid-state SMF coupling of a tapered laser requi- lasers, fiber lasers, Raman amplifiers res the use of separate lenses that col- and frequency-doubling (second har- limate the fast and slow axes, as this monic generation) crystals. type of laser is highly astigmatic. The optical system used for SMF coupling Until now, the type of laser most com- therefore consists of three lenses. The monly used in such modules has been SMF is mounted in an FC/APC con- the ridge laser, which can achieve an nector, in which the fiber facet is tilted output of up to 400 mW in an SMF. by 8° to the optical axis to prevent 10 mm Recent improvements in design have back-reflections into the laser. now resulted in new tapered lasers that feature a higher optical output power than that of ridge lasers with only a slight deterioration of the beam Results and Applications quality. The aim is therefore to develop a frequency-stabilized tapered laser As regards frequency stabilization, it has module that can achieve a higher out- been demonstrated that an FBG-stabi- put than the available ridge laser mo- lized tapered amplifier with a line width dules in an SMF. of 0.11 nm has a narrower bandwidth than a VHG-FAC-stabilized tapered laser with a line width of 0.13 - 0.4 nm. With an output of 5 W, however, the tapered Above: Module with a frequen- Method laser is more powerful than the tapered cy-stabilized tapered amplifier. amplifier, which only has an Below: Frequency stabilization The laser’s frequency is stabilized using output of 1.6 W. With respect to SMF by FBG and VHG-FAC. an external resonator. The resonator coupling, the initial interim result has is set up either in front of the tapered been a coupling efficiency of > 50 laser’s front facet with the help of a percent and a fiber-coupled power of volume Bragg grating integrated in ≈ 500 mW. These values, and thus the a micro-lens (VHG-FAC) or on the back performance of available modules on of the tapered amplifier with a fiber the market, are to be exceeded by far Bragg grating (FBG). Stabilization with in the near future by further optimizing a VHG-FAC requires no additional the lens system for tapered lasers. adjustment, whereas rear FBG stabilization requires the same amount of adjustment as SMF coupling. Contacts The module measures 32 x 32 x 62 mm2. The laser heat sink is cooled and its Dip.-Ing. G. Kochem, Tel.: -422 temperature regulated by a Peltier [email protected] element. The materials used in the Dr. K. Boucke, Tel.: -132 module are selected such that their [email protected] inevitable thermal expansion has as

Fraunhofer ILT Annual Report 2007 39 Modeling of frequency doubling in periodically poled non-linear crystals

separate steps: The absorption of the Task radiation as it passes through the crystal is calculated, from this the tempe- Using semiconductor laser diodes it is rature in the crystal is determined by now possible to produce laser radia- means of a finite-element method, and tion of good beam quality in a wide in a further pass the refraction indices, range of frequencies and with outputs which determine phase matching, are of up to several watts (over 100 W calculated with the aid of this location- with inferior beam quality). In the dependent temperature. The proce- green frequency range, however, no dure is repeated until a stationary con- suitable semiconductor materials are dition is reached. available. One possibility for producing green radiation is provided by frequency doubling of infrared radiation. In the project described here, the aim is Results and Applications to convert 1060 nm cw radiation with an output of 5 W into 530 nm radia- LiNbO3, which exhibits a very high tion. As this power is relatively small coupling coefficient, is used in the pro- for efficient non-linear processes, peri- cess. The figure shows the rise in the Rise in the output of the frequency- converted wave (530 nm) along the odically poled crystals will be used for frequency-converted output along the direction of propagation at an irra- phase matching, because this enables direction of propagation given opti- diated output of 5 W large effective coupling coefficients mized values for radius and position (1060 nm). to be utilized. The process will then be of the beam waist. For the blue curve optimized with the assistance of simu- the periodic structure was explicitly relation calculations. flected in the numerical algorithm; for the green curve a homogeneous crystal with 100 per cent phase matching and a correspondingly adapted value Method for the coupling coefficient was as- sumed. At 1060 nm the irradiated Three-wave coupling, of which fre- output amounts to 5 W. The model quency doubling is a special case, is calculations indicate conversion effi- well understood theoretically. Approxi- ciencies of almost 40 percent. mation solutions exist for estimating the conversion efficiency. Such appro- ximation solutions can also be used for periodically poled crystals. However, Ansprechpartner when it comes to examining the influence of the beam profile, temperature Dr. R. Wester, Tel.: -401 effects as a result of absorption etc., [email protected] numerical models have to be applied. Dr. K. Boucke, Tel.: -132 For this purpose, a split-step method [email protected] was implemented in which the wave propagation and the non-linear coupling are calculated alternately in two

40 Fraunhofer ILT Annual Report 2007 Superpulsed diode lasers for laser materials processing

Task Results and Applications

Compared with other laser types diode The short bars employed are operated lasers offer higher efficiency, greater with a pulse current of up to 250 A, compactness and lower system costs. which enables a maximum pulse output Diode lasers have therefore become of 300 W per bar to be attained at a established as radiation sources in pulse length of 100 ns. By imaging the many areas of medical applications exit aperture of the short bar, a spot and materials processing. In applications measuring 400 µm x 5 µm is attained, where high peak pulse outputs are which corresponds to a power density required, however, it has not been of 30 MW/cm2. With the new system, possible to use diode lasers owing to it has been possible to successfully their restricted pulsability. These in- demonstrate various applications, clude marking and the removal of including the removal of paint layers coatings. For such applications the and the marking of plastics. aim is to develop a diode laser system which is operated with short pulses The project was funded by the German (< 500 ns) at about ten times larger Ministry of Economics and Technology electrical current compared to the no- (BMWi) under project number 14508 N/1. minal operation resulting in distinctly higher intensities on the workpiece than conventional diode lasers. Contacts

Dipl.-Ing. M. Traub, Tel.: -342 Method [email protected] Demonstrator of a superpulsed Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 diode laser system. The implemented demonstrator uses [email protected] short bars with an aperture of 800 µm x 1 µm. The diode lasers are operated with a pulse power source which, using adequately short pulses, enables the operation at ten times larger electrical current compared to the nominal operation in CW or long pulse mode. To increase the output further, two bars are superpositioned by means of polarization multiplexing, and to achieve as high a power density as possible on the workpiece, the aperture of the short bar is anamorphotically imaged onto the workpiece.

Fraunhofer ILT Annual Report 2007 41 Fiber-coupled diode lasers for pumping fiber lasers

Task Results and Applications

To pump fiber lasers, brilliant, fiber- The fiber-coupled diode laser pump coupled diode lasers based on con- modules achieve a laser output of duction-cooled heat sinks are required. 43 W from a fiber with a diameter At a pump wavelength of 976 nm for of 105 µm based on two broad stripe Ytterbium fiber lasers, the aim is to emitters, and 60 W based on 10 in- provide 50 W per module from a fiber dividual emitters. The diode lasers with a core diameter of 105 µm. This presented are used as pump sources core diameter is compatible with com- for fiber lasers. The pump wavelengths mercial fiber combiners which are used can be adapted for optical pumping of for power scaling of the pump source. solid-state lasers. Further uses include direct applications like plastics processing and laser medical engineering.

Method

Two concepts for fiber coupling of Contacts conduction-cooled diode lasers are being examined. The first concept Dipl.-Ing. C. Wessling, Tel.: -565 is based on five 90 µm wide single [email protected] emitter diodes, each with a laser out- Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 put of 7 W, which are optically stacked [email protected] and coupled into the fiber with spherical optics. The distributed arrangement

Fiber-coupled diode laser pump of the beam sources ensures efficient modules (fiber diameter 105 µm, heat removal of the power loss and numerical aperture 0.22): thus the high absolute radiant power Above: 60 W module based of 7 W per individual diode. Optical on individual emitter diodes. Below: 43 W module based beam forming facilitates the efficient on broad stripe emitter diodes. coupling of each individual emitter diode by means of one adjustment step. Compared with the state of the art, which is to use one individual emitter, 10 individual emitters are coupled into one fiber by optical stacking and polarization coupling. The second concept is based on 800 µm broad stripe emitters with 28 W of laser power in each case (diode laser array with 4 - 5 emitters and a high fill factor). Two polarization-coupled broad stripe emitters whose beam profile has been symme- trized with a microstep mirror are coupled into the fiber with anamorphotic imaging optics. The concentrated arrangement of the diode lasers permits easy beam forming using individual lenses without microlens arrays at a comparatively high power density.

42 Fraunhofer ILT Annual Report 2007 Transformation optics for de-coating metal parts by high-power laser

Task Results and Applications

De-coating by pulsed laser has a signi- Based on the transformation concept, ficant advantage over conventional an optical processing system for de- cleaning processes in that it enables in- coating was developed and tested suc- dividual layers to be ablated selectively. cessfully. The ablation rate was increa- Contamination of the surrounding area sed by 30 percent compared to con- can be reliably prevented by siphoning ventional scanner optics, achieving a off the solid and gaseous ablation pro- maximum scanning frequency of 200 ducts and by abstaining from the use Hz. The maximum scanning speed rea- of chemicals. Using a 1-D scanner, the ched was 24 m/s, using focusing optics laser beam is deflected perpendicularly with a focal width of 160 mm, which to the feed direction inside special pro- produces a deflection width of up to cessing optics for the removal of surface 60 mm. Such deflection widths are coatings. However, the achievable ab- achieved due to the larger focal width lation rate is limited by the scanner’s of the focusing optics and the reduced maximum deflection frequency, parti- inertia of the mirror compared to con- cularly at laser outputs of more than ventional optical systems. The result is Transformation optical system. one kilowatt average laser power. a significantly increased process speed.

The optical system can achieve an efficiency of 90 percent, and is suitable Method for use in combination with fiber-coupled Nd:YAG lasers with an output of up to The deflection frequency of the scan- 2 kW. ner is limited due to the mass moment of inertia of the applied mirror. A solution is to use transformation optics to achieve a beam aspect ratio of 1:4 Contacts before the laser beam hits the scanner mirror with a symmetrical power density Dipl.-Ing. M. Traub, Tel.: -342 distribution. In this way, it is possible [email protected] to use a mirror with the same surface Dipl.-Phys. C. Johnigk, Tel.: -301 area but only half the width, which re- [email protected] duces its moment of inertia by a factor Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 of four. This, in turn, enables a signifi- [email protected] cantly higher scanning frequency.

Fraunhofer ILT Annual Report 2007 43 Automated assembly technology for miniaturized lasers for materials processing

a static tolerance distribution of indivi- Task dual laser components. The aim is to significantly cut costs through automa- Laser systems for labeling, marking and ted assembly, adapted construction engraving metal, plastics and ceramics techniques and an optimized system are used in a wide variety of applications design. and already occupy a fast increasing share of the global market for labeling systems. Results and Applications Automating the assembly of such lasers opens up the possibility of producing A microslab laser system is being tested and supplying them in large batches at in the laboratory with regard to the competitive prices. In the cluster of excel- required assembly accuracy of the lence ‘Integrative Production Technology components employed. On the basis for High-Wage Countries’, a miniaturized of homogenizing pump optics, the laser slab laser is currently being designed can be assembled in an extremely which meets the requirements of auto- compact arrangement using a micro mated assembly. Suitable strategies lens array for pump beam forming and for robot-based assembly are also being a positively confocal hybrid resonator developed. with an overall length of 150 mm. The laser can achieve an output of 8 W cw with excellent beam quality. Further- more, proof of principle has been Method established that a functioning pump optical system can be assembled in a The InnoSlab laser developed at the planar configuration using automated Fraunhofer ILT enables system compo- joining processes. A semi-automated nents to be arranged in a compact and assembly process using 6-axis parallel planar way, thus making it easier to kinematics is currently in the develop- Above: Microslab demonstrator on a ceramic substrate. use automated assembly technology ment stage. Below: Conventionally assembled to build the microslab laser. In addition, laboratory setup. the use of a ceramic base plate facilitates the hybrid integration of optical and electrical functions via a structured, Contacts electrically and thermally conductive layer. The components are fixed with Dipl.-Ing. J. Dolkemeyer, Tel.: -351 the degree of freedom required for [email protected] later adjustment using joining tech- Dipl.-Ing. M. Funck, Tel.: -351 niques that satisfy the given thermal [email protected] and electric requirements and ensure Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 long-term-stable, accurately positioned [email protected] assembly, without the need for additional adjusting aids. To ensure cost- efficient manufacturing, strategies are being developed to enable the assembly of functioning lasers, even given

44 Fraunhofer ILT Annual Report 2007 InnoSlab-based amplifier for sub-ns laser pulses with an energy of 100 mJ

Task Results and Applications

A collaborative project funded by the The first amplifier stage can achieve BMBF aims to develop a laser plasma a stable peak pulse energy of 65 mJ source for generating EUV radiation in at a pulse repetition rate of 1 kHz. the wavelength range between 2.3 nm No degradation of the optics was and 4.4 nm. This spectral range is observed in a series of fatigue tests called the ‘water window’ and can be lasting several hours. used to examine biological samples, for instance. Plasma generation requires The beam quality and the shape of laser pulses in the sub-ns regime with the seed pulses remain virtually un- a pulse energy of more than 100 mJ at changed. In order to reach 100 mJ, the a pulse repetition rate of 1 kHz. system is currently being extended by two identical InnoSlab amplifier stages. Using an InnoSlab-based amplifier, seed pulses with an energy of 2.5 mJ and a duration of between 500 ps and 1 ns are to be amplified to 100 mJ at Contacts a pulse repetition rate of 1 kHz. This application requires a good beam Dipl.-Phys. D. Esser, Tel.: -437 quality of M2 < 4. [email protected] Dipl.-Phys. M. Höfer, Tel.:128 [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 Method [email protected]

The target parameters can be achieved by means of a three-stage chain comprising an InnoSlab pre-amplifier and two InnoSlab power amplifiers. The pre-amplifier is pumped from one end by eight diodes, and the two power amplifier stages from two ends of the InnoSlab-based slab crystal by sixteen diodes. The am- pre- and power amplifiers. plifier resonator is operated exclusively with planar optics, which reduces the time and cost of development.

Particular attention is given to aspects such as suppressing parasitic oscillations of the amplifier, reducing ASE effects, and keeping below the optical system’s damage thresholds.

Fraunhofer ILT Annual Report 2007 45 Femtosecond InnoSlab amplifiers of high average output

with a total average output of 800 W Task using two sources. Efficiency can be improved by folding the transmitted For many years, the Fraunhofer ILT has pump radiation back in a moderately developed InnoSlab amplifiers based doped laser medium to increase the on neodymium-doped crystals. Now, pump intensity. the institute intends to use also Ytter- bium-doped materials (YAG, KGW, KYW) in a slab geometry in order to amplify pulses with durations of less Results and Applications than 1 ps. The aim is to reach an average output of several 100 W, which In a preliminary test prior to full assem- can be achieved using a seed power bly, a unilaterally pumped InnoSlab of ~1 W at repetition rates of > 10 MHz amplifier was implemented. The without chirped pulse amplification. Yb:YAG crystal, pumped with a power of 400 W, was seeded with a commercial laser oscillator (300 mW, 277 fs, 63 MHz). An average power of 77 W Method has been achieved with a pulse duration of 786 fs and a beam quality of M2 < 1.3. Using high-power diode lasers of the These data correspond exactly to the latest generation, a high-brilliance simulation calculations carried out pre- pump source with an average output viously. In the case of bilaterally pum- of 400 W was developed. This provides ped amplifiers, the numerical simulations the high pump power densities required predict average outputs of > 300 W. for efficient amplification in Ytterbium This opens up new applications for doped crystals. A slab crystal of 10 x ultra-short pulsed lasers in the field of 10 x 1 mm3 can be pumped bilaterally high-rate materials processing, plasma generation, and efficient production of short-wave radiation through non-linear Bilaterally pumped processes. fs InnoSlab amplifier.

Contacts

Dr. P. Rußbüldt, Tel.: -303 [email protected] Dipl.-Phys. T. Mans, Tel.: -379 [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 [email protected]

46 Fraunhofer ILT Annual Report 2007 Highly efficient laser pulse source for a space-based LIDAR system

Task Results and Applications

Spatially resolved measurements of Using a flexible laboratory setup, concentrations of molecules (such as 1064-nm laser pulses with more than water vapor or carbon dioxide) or aero- 80 mJ of energy were generated and sols in the atmosphere using LIDAR then converted to pulses of more than (Light Detection and Ranging) require 30 mJ and 355 nm by means of non- highly stable, narrowband, short laser linear crystals. The system’s optical- pulses of high energy. The key criteria optical efficiency exceeds the require- when selecting a suitable laser source ments by far. In order to demonstrate for satellite-based operation are that the laser’s specific suitability for use in the system is reliable and efficient, and a satellite, the first step was to trans- of a compact and light design. late the frequency-stabilized oscillator into a compact design with a base area In this project, a laser source is requi- of 400 x 200 mm2. The cascaded slab red which generates laser pulses with amplifier stages featured in the design an energy of at least 70 mJ and a wave- provide an excellent means of scaling length of 1064 nm at a repetition to higher pulse energies such as those rate of 100 Hz. These laser pulses are required, for example, in LIDAR systems then tripled in frequency to at least used for molecule detection. 21 mJ and 355 nm outside the resonator with the help of nonlinear crystals. Above: Preliminary design of The system should be capable of ope- the satellite-based laser source (exploded diagram). rating in space continuously for at least Contacts Below: Compact design of 3 years. the frequency-stabilized laser Dipl.-Phys. J. Luttmann, Tel.: -128 oscillator. [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 Method [email protected]

A Q-switched resonator with a diode- pumped Nd:YAG rod serves as the laser oscillator. Pulse generation is frequency-stabilized with the help of a seed laser. This enables laser pulses to be generated in excellent spatial and temporal quality.

Downstream of this is a diode-pumped Nd:YAG amplifier operating on the InnoSlab principle, which amplifies the energy of the laser pulses without sa- crificing quality, thus largely determining the efficiency of the overall system. The special geometry of the Inno- Slab laser provides the ideal basis for a highly efficient amplification process, and also renders the system insensitive to degradation of the pump diodes and temperature fluctuations.

Fraunhofer ILT Annual Report 2007 47 Diode-seeded fiber amplifier for LIDAR applications

Fiber amplifiers with fully fiber-integra- Task ted structures have several advantages over conventional laser-rod amplifiers: Pulsed LIDAR systems emit short laser • They do not require adjustment. pulses and can determine the distance • The beam parameters are not to diffusely scattering objects by measur- influenced by the power setting. ing the signals’ time delay. The perfor- • A high amplification and efficiency mance potential depends directly on the can be achieved. laser system itself. The repetition rate (approx. 0.5 to 2 MHz) is defined by the number of measuring points required in a given time period. The maximum Results and Applications range of the measuring instrument is predetermined by the pulse peak output The prototype presented here is passively (greater than 1 kW) in connection with cooled and equipped with control the beam quality (M2 < 1.5). Temporal electronics that monitor the laser’s properties such as pulse duration and functions. Internally, they monitor such jitter determine the achievable accuracy. factors as the temperatures of the laser diodes, while externally they ensure As part of an internal Fraunhofer pro- the laser is not damaged by missing ject, the ILT is currently collaborating trigger signal, for example. with the Fraunhofer IPM to develop a fiber laser system for scanner-based dis- Other possible areas of application tance measurement. for this laser system are measurement technologies with temporally shaped laser pulses, micro-materials processing, life sciences or precision laser drilling. Method

In order to meet the high demands on Above: Prototype of a pulsed fiber amplifier for LIDAR timing, i.e. externally triggerable pulses Contacts applications. with durations in the sub-ns range and Below: Laboratory setup of low pulse jitter combined with the ne- Dipl.-Phys. J. Geiger, Tel.: -123 the fiber amplifier. cessary pulse peak outputs in the kilo- [email protected] watt range and average outputs of se- Dipl.-Ing. H.-D.Hoffmann, Tel.: -206 veral watts, the laser must be designed [email protected] in an oscillator-amplifier configuration. The temporal and spectral properties of the laser pulse are determined by a pulsed laser diode, whose signal runs through a two-stage fiber amplifier arrangement. This concept offers maximum variability with regard to the temporal parameters, such as free triggerability within a time window of 2 µs and variable repetition rates.

48 Fraunhofer ILT Annual Report 2007 Integrated frequency-stabilizing electronics for LIDAR-based pulsed lasers in aerospace

as pulse energy stability. By varying the Task parameters, it is possible to set operating points in such a way that all these High-resolution measurements of wind operational characteristics are fulfilled speeds or the concentration of gases simultaneously. The types of sensors, such as water vapor, methane and CO2 actuators and control techniques em- in the atmosphere using LIDAR (Light ployed vary according to the specific Detection And Ranging) require highly application. stable narrowband laser pulses with bandwidth-limited pulse durations in the range of 10 - 100 ns. These are usually generated by seeding a Results and Applications Q-switched laser with a highly stable low-power narrowband laser source In the experiments carried out at the while actively stabilizing the resonator Fraunhofer ILT, a pulse bandwidth of length. The systems required for aero- less than 8 MHz (pulse repetition rate space applications typically have a pulse 100 Hz, pulse duration 30 ns, pulse repetition rate in the 100 Hz range. In energy 12 mJ, M2 < 1.1) and an excep- some applications, it is advantageous tionally high frequency stability were Integrated frequency-stabilizing to generate pulse trains with as small achieved even under the influence of electronics. a pulse distance as possible. Frequency- major disturbances to the resonator stable operation must also be ensured length. When generating double- and under the influence of strong vibrations. triple-pulse trains, it was possible to reduce fluctuations of the pulse energy to just a few percent, at a pulse distance of 100 µs. At present, the re- Method searchers are investigating ways of increasing the pulse repetition rate in The methods selected to adjust the re- order to create resolution advantages sonator length are based on measure- for helicopter-borne LIDAR instruments. ments of the seed signal and enable the suppression of mechanical oscillations up to the multi-kilohertz range. In addition, the ‘Ramp-Delay-Fire’ pro- Contacts cess developed and patented by the Fraunhofer ILT enables a dynamically Dipl.-Ing. V. Morasch, Tel.: -224 optimized prediction of the pulse emis- [email protected] sion time accurately to within a few Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 tens of nanoseconds. The control unit [email protected] takes the form of electronics integrated in SMD technology. The use of FPGA- and microcontroller-based sub- processes combines a strict program sequence determined down to the nanosecond range with the flexibility required for the dynamic decision- making process. By cascading several control circuits and using dynamic value tables, it is possible to achieve not only frequency stability, but also other operational characteristics such

Fraunhofer ILT Annual Report 2007 49 Energy scaling of pulsed Nd:YGG-based laser beam sources at 935 nm

Task Method

The task is to evaluate the duration- A numerical model for simulating the dependent absorption of narrow-band amplification processes, taking re- laser pulses for satellite-based measure- absorption effects of the quasi-3-level ment of climate-relevant water vapor system as well as ASE and thermal lens distributions with the DIAL process. effects into account, was implemented This requires the availability of specific to identify and interpret system-rele- wavelengths in the range of suitable vant parameters. Extensive parameter water vapor absorption lines around studies enabled to identify promising 935 nm. pump geometries and amplifier configurations. Innovative mixed-garnet crystals offer the possibility of using direct diode- pumped systems in this wavelength range, which in turn makes it possible Results and Applications to achieve the high efficiency and low complexity necessary for space missions Pulse energies in the 40 mJ range are as compared with established titanium predicted with an Innoslab amplifier sapphire lasers or optical parametric pumped by both ends. Experimental oscillators. A cooperative project implementation is currently being in- between Hamburg University and the vestigated. Crystal Research Institute FEE has produced the first Nd:YGG crystals with As water vapor significantly determines Above: Slab-based amplifier. the mechanical and optical quality the energy balance of the atmosphere, Below: Nd:YGG boules by Hamburg University (left) and needed for Q-switching. Pulse energies the use of robust LIDAR systems with the FEE (right). of around 4 mJ and 100 Hz have been emission at a wavelength of 935 nm demonstrated with an efficiency of on mobile platforms such as airplanes 9 percent (absorbed pump light to and satellites, as well as of ground- laser light). The researchers are cur- based LIDAR systems, can be expected. rently investigating InnoSlab-based In principle it has been shown that amplifiers for energy scaling in the tailor-made laser crystals and adapted multi-10-mJ range. laser designs render feasible the direct and efficient generation of application- specific wavelengths for metrology and materials processing.

Contacts

Dipl.-Phys. J. Loehring, Tel.: -414 [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 [email protected]

50 Fraunhofer ILT Annual Report 2007 Broadband tunable Ti:sapphire laser with nanosecond pulses

Task Results and Applications

Owing to their great spectral bandwidth At a burst frequency of 1 kHz, pulse and high amplification, Ti:sapphire lasers energies of more than 3 mJ, pulse are the workhorses among tunable durations of around 10 ns and a beam solid-state lasers in science and engi- quality of M2 < 1.2 are achieved. When neering. Their fundamental tuning range the system is continuously tuned covers wavelengths between about across a selected wavelength range, 670 nm and 1100 nm. The special the line width is about 300 GHz. Dur- feature of the solution presented is ing operation with a freely chosen that a wavelength range of more than fixed wavelength, the user can switch 300 nm and an optical finesse of more between line widths of about 300 GHz than 10,000 are achieved with a single or less than 10 GHz. set of lenses - without replacing any components. The mechanical design Because of its high pulse output and of the demonstrator is distinguished excellent beam quality, the laser is emi- by its ease of assembly and ease of nently suitable for frequency conversion. maintenance, and supports long term It can, for example, form the basis of stable alignment-free operation. a solid-state laser system that can be tuned from 210 nm to 1000 nm.

Areas of application for this system are Method high-throughput investigations in the semiconductor industry, bioanalysis An industrial frequency-doubled Q- and materials science. The system has switched laser is used as pump source an automated wavelength adjustment for the Ti:sapphire laser. Nanosecond mechanism which was also used to pulses are generated by gain switching, record the curves requiring no further optical switch. In the demonstrator, the optical resonator Above: Demonstrator with is mechanically separated from the robust, easy-to-assemble and easy-to-maintain mechanical water and electricity connections and Contacts design. hermetically encapsulated. The wave- Below: Excellent performance length is adjusted using high-precision Dipl.-Phys. B.Jungbluth, Tel.: -414 and wide tuning range without piezo-based alignment mechanisms [email protected] replacing optical components made by Steinmeyer FMD Dresden Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 GmbH. The laser control supports [email protected] two operating modes: setting a freely chosen fixed wavelength, or continuous tuning across a selected wavelength range.

Fraunhofer ILT Annual Report 2007 51 Compact frequency converter for tunable laser radiation

Task Results and Applications

The tuning range of today’s Ti:sapphire Given an adequate tuning range of lasers covers more than 300 nm in the the fundamental laser, the converter red and near-infrared spectral range. covers a wavelength range between By means of non-linear frequency con- 210 nm and 510 nm without any version, this output spectrum can be gaps. Using the described arrange- transformed into shorter wavelengths ment, outputs of 1100 mW were de- ranging into the ultraviolet. To generate monstrated with frequency doubling, a frequency-shifted output spectrum 500 mW with frequency tripling and between 210 nm and 500 nm, at least 200 mW with frequency quadrupling. three different conversion processes are This corresponds to conversion effi- needed - frequency doubling as well as ciencies of 50 percent, 20 percent and trebling and quadrupling of the funda- 10 percent. mental laser radiation. The solution presented combines these conversion The converter presented here serves as processes in a single compact and a module for a solid-state laser system alignment-insensitive module. with a tuning range of 210 nm to 1000 nm. The system permits automatic switching between different wavelength ranges and computer-controlled Method adjustment of the desired wavelength with an accuracy of better than 5 pm. In the module the two-stage conversion processes, in this case frequency tripl- Applications of the system include

Compact module for generating ing and quadrupling, are realized by high-throughput investigations in the frequency-converted radiation combining positively birefringent BIBO semiconductor industry, bioanalysis from UV to VIS. crystals with negatively birefringent and the materials sciences. BBO crystals. By selecting a suitable type of interaction, the two crystals can be arranged directly behind each other, without any optics in between. As a re- Contacts sult, the beams in the second converter crystal are always optimally aligned to Dipl.-Phys. B. Jungbluth, Tel.: -414 one another. For tuning to the adjacent [email protected] input wavelength, both crystals are Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 turned in the same spatial plane. This [email protected] makes it possible to stack all the conversion stages on the same mechanical platform, producing an extremely compact configuration.

52 Fraunhofer ILT Annual Report 2007 Q-switched Nd:YAG laser with an average output in the kW range for surface processing

Task Results and Applications

To increase the efficiency of polishing, Using a 400 µm fiber for beam delivery, coating-removal and structuring on the Q-switched laser achieves pulse large surface areas, high-power beam outputs of 500 kW and a pulse duration sources are needed. The object of this of about 100 ns at 35-kHz repetition project was to develop a fiber-coupled frequency. This represents an average Q-switched solid-state laser with pulse power of 1700 W at the fiber output. durations in the 100 ns range and an The average power has thus been more average output distinctly higher than than doubled. Owing to the improved the 850 W currently provided by com- beam quality, optionally a four times mercially available beam sources. increased power density on the work piece or a two times larger working distance is available. The system’s high performance capability means that Method large surface areas can now be cost- efficiently processed. Based on a pulsed Nd:YAG laser deve- Laser housing. loped at the Fraunhofer ILT with an output of 800 W from a fiber with 600 µm core diameter, a compact, Contacts mobile laser system for industrial use was designed by coupling two laser Dipl.-Ing. R. Meyer, Tel.: -197 modules based on a diode-pumped [email protected] rod laser. Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 [email protected]

Fraunhofer ILT Annual Report 2007 53 Linearly polarized fiber lasers with high average output

The investigated concept makes it Task possible to implement fully fiber-integrated laser resonators with fiber The cw output of fiber lasers has risen Bragg gratings and a pump based rapidly during recent years. However, the on fused combiners. currently available high-output systems operate with random polarization. In addition to material processing, The task was therefore to demonstrate where precise control of polarization whether linearly polarized laser radiation can lead to better and more reprodu- can also be generated with fiber lasers cible results, another potential field on a stable basis with an output in kilo- of application is that of frequency con- watts. version. Furthermore, polarized laser beams can simply be overlapped with a polarization coupler, for example in order to scale the output, to combine Method time-modulated and unmodulated laser beams, or to generate a custo- Comparative tests of generating linear- mized intensity distribution in the focus. ly polarized laser radiation with fiber lasers were carried out. Both graded- index and microstructured fibers were empirically examined in various confi- Contacts gurations. Dipl.-Phys. J. Geiger, Tel.: -123 During this work, fiber laser resonators [email protected] with and without a polarizer inside Dipl.-Ing. H.-D.Hoffmann, Tel.: -206 the resonator were compared with one [email protected] another, and the polarization degree of the laser radiation was measured at various winding radii. Above: Microstructured fibers for generating linearly polarized laser radiation. Below: Test set-up for an output of 850 W. Results and Applications

A polarization degree of over 97 percent was achieved with both fiber laser resonators and fiber amplifiers. The output was 850 W, limited by the available pump output. The polarization status was very stable, making it safe to assume that the polarized output can be increased into the range exceeding 1 kW.

The experiments coincided very closely with the results of the digital simulation obtained using a numerical simulation tool developed at the Fraunhofer ILT.

54 Fraunhofer ILT Annual Report 2007 White light interferometer for characterizing optical coatings for ultra-short pulse lasers

This measuring principle was improved Task vis-à-vis previous configurations in such a way that the luminosity of the When passing through optical systems set-up was increased by several orders or reflected by dielectric mirrors, femto- of magnitude. A compact easy-to-ope- second laser pulses are influenced rate mechanical set-up (lower figure) by differences in the group delay dis- and a computer-assisted automatic persion (GDD) between the individual measuring process including evaluation spectral elements. For example, the were implemented. pulse duration in dielectrics is leng- thened by a positive GDD, which frequently has to be offset by optical elements with a defined negative GDD. Results and Applications A particularly elegant solution is to use chirped mirrors, where it is possible An easy-to-operate device for measuring to achieve any desired GDD by varying the GDD of flat mirrors was developed. the thicknesses of the dielectric coat- Thanks to a quick-change device for the ings. In theory, chirped mirrors make test objects, exposure times in the ms it possible to achieve any desired range and an automated measuring spectral GDD. In practice, however, process, the dispersion of mirrors can be minor fluctuations in thickness, of the determined rapidly (~1 min) and repro- magnitude of a single atom, occur in ducibly. the coatings. These alter the GDD so significantly that it becomes necessary So far, measuring devices in the wave- to measure the GDD for many appli- length ranges of 900 - 1100 nm, cations. This measuring process must 500 - 950 nm and 250 - 800 nm for be such that it can be routinely perfor- use in industrial quality control have med by the manufacturer with a high been delivered. degree of accuracy as well as being reproducible. Above Interference pattern of a dielectric mirror. Contacts Below: White light interferometer for 900 - 1100 nm. Method Dr. P. Russbueldt, Tel.: -303 [email protected] The GDD is determined by measuring Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 the spectral phase displacement occurr- [email protected] ing on reflection from a flat mirror, using a Michelson white-light interferometer. A white light interference pattern occurs when using the same arm length and an identical optical beam path. Tilting one of the mirrors produces a pattern of stripes that is equidistant in flat mirrors. A cross-section through this interference pattern (gap) is spectrally split (upper figure). If dispersive mirrors are incorporated in one arm of the interferometer, a wavelength- dependent displacement of the interference stripes can be observed. This forms the basis on which the GDD is calculated.

Fraunhofer ILT Annual Report 2007 55 Generating sub-ns laser pulses of variable pulse duration with pulse energy in the mJ range

Task Results and Applications

As part of a joint project funded by the Pulse energies up to 2.7 mJ at a pulse BMBF, a laser plasma source for gene- repetition rate of 1 kHz and diffraction- rating XUV radiation in the wavelength limited beam quality are achieved with range between 2.3 nm and 4.4 nm the Nd:YAG based regenerative ampli- is to be developed. This spectral range fier. The pulse duration can be adjusted is known as the »water window«, and between 300 ps and 1.5 ns. The diode- permits applications such as the exami- seeded regenerative amplifier opens nation of biological samples. To create up a multitude of further potential the plasma, laser pulses in the sub-ns applications in the field of microma- regime with an energy of more than chining. The present goal is to extend 100 mJ at a pulse repetition rate of the system to 2 kHz at the identical 1 kHz are needed. pulse energy and to move the lower limit of the pulse duration range to This report presents the generation below 100 ps. and pre-amplification of the laser pulses to a pulse energy of approximately Electrically pulsed laser diode with beam shaping optics. 2.5 mJ. The pulse duration is to be adjustable between about 500 ps and Contacts 1 ns. Dipl.-Phys. D. Esser, Tel.: -437 [email protected] Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 Method [email protected]

A laser-diode-based optical pulse generator with a regenerative amplifier appears to be the best solution for the planned range of parameters. The pulse duration, shape and energy of the seed diode emission can be varied by means of gain switching and bias current and by a modulator incorporated in the chip using an electric circuit of the size of a credit card. The laser pulses thus generated are amplified to the required pulse energy by means of the regenerative amplifier. Faraday isolators protect the laser diode from back-reflected radiation. The pulse repetition rate can be freely selected between 0 and 10 kHz.

56 Fraunhofer ILT Annual Report 2007 Probe for the analysis of a laser-induced plasma

Task Results and Applications

To understand the physical processes The new probe was used to investigate in the targeted applications, it is indis- ablation plasmas. The density develop- pensable to investigate the parameters ment of plasmas generated by a ps of a laser-induced plasma. When using laser with burst lengths ranging from various materials in combination with 0.5 to 100 µs was investigated for low pulse energies and consequently various materials. Fluctuations in the low emitted luminosity values, an ana- density were identified that can be lysis using optical methods is time-con- attributed to shielding phenomena. suming and expensive. Direct analysis Thanks to the fast and direct measuring of the plasma flow can reveal facts method, any dependencies of the plas- about the propagation rate, the tem- ma parameters on the laser parameters poral development of the density of can be efficiently investigated. The the ablated material, and the plasma probe concept is flexible in terms of its temperature. physical size and temporal resolution, enabling it to be adapted to meet the specific requirements. The robust Above: Probe in the structure of the probe permits its use laboratory setup. Method under extreme conditions such as in Below: CAD drawing, a vacuum or in corrosive plasmas. cross-section of the probe. A robust probe with a simple operating Because of its compact design, the principle was developed to enable time- probe can easily be integrated in resolved examinations of the plasma. existing facilities. Density measurements are performed directly in the ion flow, which is measured using a Faraday capacitor with a negative bias against the housing. Contacts The probe is positioned directly in the plasma flow, with the plasma entering Dipl.-Phys. M. Strotkamp, Tel.: -379 through a specified opening in the [email protected] housing. The electrons are diverted to Dipl.-Ing. H.-D. Hoffmann, Tel.: -206 the housing, while the ions impinge [email protected] on the Faraday capacitor where they trigger a current signal. This signal is locally amplified in a vacuum to minimize interference during transmission. It can be measured directly using an oscilloscope. The propagation rate is directly determined from the signals and subsequently incorporated in the calculation of plasma density.

Fraunhofer ILT Annual Report 2007 57 Ray tracing in inhomogeneous media

Task Results and Applications

The ray tracer already developed at the The results of a model assignment for Fraunhofer ILT is to be expanded to co- ray tracing in inhomogeneous media ver ray propagation in inhomogeneous illustrate how the beam is refracted media with a spatially dispersed index in spatially isotropic dispersion of the of refraction. refractive index (figure). The results of ray tracing in inhomogeneous media The beam-forming property of the ma- show that the light rays and wave- terial vapor or plasma, or of an ultra- fronts are changed by density altera- sonic flow of the working gas, are to tions in the ultrasonic flow of the cutt- be more closely examined. ing gas.

This greater understanding of the effect of refraction in the gas phase Method on the beam shape at the absorption Light rays and wavefronts shining through front is applied in the design of beam- spherical dispersion of the refractive index. To calculate the geometrical and opti- shaping optics. cal propagation of laser beams, the ei- konal equation is solved with spatially The project presented was sponsored varying dispersion of the refractive in- by the German Research Foundation dex. The light rays in inhomogeneous DFG as part of the Cluster of Excellen- media are not straight lines, but non- ce »Integrative Production Technology linear curves. Because wavefronts pass- for High-Wage Countries«. ing through an area with inhomogeneous dispersion of the refractive index cannot be clearly displayed or may overlap one another, the dispersion of Contacts the power output in the diffracted laser beam is projected onto a Cartesian Dipl.-Phys. U. Eppelt, Tel.: -163 grid in the background and recorded. [email protected] The ray tracing algorithm also covers Prof. Dr. W. Schulz, Tel.: -204 methods of interpolating dispersions [email protected] of the refractive index that have been entered point by point, as well as an adaptive refinement of the grid (see figure).

58 Fraunhofer ILT Annual Report 2007 Surface analysis with extreme ultraviolet radiation for the characterization of thin films

culated in the spectral range from 0.01 Task to 40 nm. Experiment-specific parameters, such as detector resolution capa- Grazing-incidence reflectometry with city and beam divergence, can also be extreme ultraviolet radiation (EUV) in included. Typical film systems for EUV the wavelength range from 1 to 50 nm applications consisting of Si, SiO2, Zn, makes it possible to characterize thin C, Mo, Ag etc. were simulated. films on the nanometer scale. The composition, thickness and surface roughness of a film system can be determined indirectly from its reflectivity Results and Applications curve, through the combination of non-linear regression techniques and It was shown that noise has a direct in- the transfer matrix formalism. The re- fluence on the precision of the fitting flectivity can be determined either as a algorithm. In a single-layer thin-film function of the incident wavelength at system (< 10 nm thickness), for exam- a fixed angle of incidence or vice versa. ple, with sub-nm roughness values and It is even possible to determine an an absolute reflectivity measurement effective roughness of concealed films accuracy of +/- 0.5 percent, the film within the system. This method repre- thickness can be determined very well, sents an alternative to existing tech- with a deviation of 0.2 percent. The niques and is intended in particular to roughness of the revealed film can be establish the use of EUV radiation in determined with a precision of < 10 metrology. Before now, such measure- percent, and that of the concealed film ments were only possible on synchro- around 20 percent. The material com- tron-based radiation sources. The se- position can be determined from the miconductor industry in particular will reflectivity curve on the basis of the benefit from the use of the EUV mea- element-specific absorption edges. The surement technique, which is intended sequence of the elements in the film for widespread use ranging from de- system can be derived from the peak Above: Wavelength-dependent fect detection on wafers through to heights. An EUV reflectometer was de- reflectivity curve of an Al/Ag/Si characterization of optical components signed and is already being produced. film system. in the shortwave spectral range. Below: 3-D model of the EUV reflectometer for measuring thin films.

Contacts Method M. Banyay M.E., Tel.: -313 To evaluate the reflectivity curves, nu- [email protected] merous computer simulations were Dr. L. Juschkin, Tel.: -313 performed and a MATLAB-based tool [email protected] was developed for modeling thin films. Prof. Dr. P. Loosen, Tel.: -162 This enables the reflectivity curves of [email protected] virtually any thin film system to be cal-

Fraunhofer ILT Annual Report 2007 59 Data transmission with low latency

Task Results and Applications

A low-latency data transmission system It was shown in a prototype that the for real-time control of a plasma device physical transmission layer operates is to be developed. It must permit the faultlessly and enables a signal transit transmission of measured charges in time delay of 100 ns per bus user. In a the nC range and be capable of driving preliminary stage of the protocol still spatially distributed power semicon- to be implemented, analog measured ductors with a timing accuracy < 10 ns. values were transmitted via a point-to- The data transmission system must be point connection. resistant to electromagnetic interference and bridge potential differences Thanks to its modular structure, its >10 kV at voltage transients >100 kV/µs. high electromagnetic immunity and It should have a modular structure to low latency, this data transmission sys- permit expansion, and should feature tem is eminently suitable for imple- self-diagnosis functions and a redun- menting fast control loops in wide- dant architecture. Asynchronous events area systems. This system also lends should reach their drain within one µs, itself to the safe driving of switching as should the data. elements at high potential - such as Above: The system’s double- static inverter stations for high-voltage ring topology. direct current transmission lines. Below: Data transmission in the physical layer. Method

Based on low-cost, readily available Gi- Contacts gabit-Ethernet components, a double ring of glass fiber is put in place whose Dipl.-Ing. S. Probst, Tel.: -314 logical function is that of a determinis- [email protected] tic, centrally controlled bus. The lean Dr. W. Neff, Tel.: -142 protocol is implemented in programm- [email protected] able logic. To ensure the exact measurement and generation of times, all bus users are equipped with synchronized clocks whose pulse is derived from the synchronous data transmission. Depending on the glass fiber components selected, distances of up to several kilometers between the participants are possible provided that the additional delay of 5 µs/km due to the finite speed of light is acceptable.

60 Fraunhofer ILT Annual Report 2007 Laser Material Processing Business Area Laser Material Processing

Production processes addressed by this business area include cutting and joining techniques applying micro- and macro-technology, as well as surface engineering. The services provided extend from process development for the manufacture of sector-specific products and the integration of these processes in production lines, through simulation services for laser applications, to the production of samples in support of series production start-up. The strength of the business area is rooted in its extensive process know-how, which is tailored to specific customer requirements in each case. In addition to process development, the business area offers complete system solutions which utilize selected technology networks. Customers are offered laser- specific solutions that encompass design engineering, material specification, Cutting adhesive seals product design, production equipment for microtiter plates. and quality assurance. In addition to the target market of material processing, the business area also addresses customers in the medical engineering, biotechnology and chemical sectors.

62 Fraunhofer ILT Annual Report 2007 Contents

Überschrift

Computer-aided robust design New applications for high-strength High-precision nozzle drill holes as exemplified by laser cutting 64 steel sheets through local heat in Inconel® 690 nickel-based super treatment 79 alloys 95 Welding thick steel plates by disc laser 65 Laser polishing of glass molds 80 Influence of process gas on percussion drilling 96 Zero-gap lap welding Dual gloss effect created by of ZE-Mg sheets 66 laser polishing 81 Plasma diagnosis during laser drilling 97

Strength testing of CO2 laser Laser beam microwelding Drilling with efficient melt expulsion 98 MAG hybrid welds 67 of 2-D optical waveguide arrays 82 Micro-perforation Physical model for root formation Laser beam-assisted bonding of balloon catheters 99 and gap-bridging ability during of silicon and glass for wafer level laser welding 68 packaging, MEMS packaging and Diagnosis of ultra-fast, laser-induced display packaging 83 melt dynamics of metals 100 Simulating the welding process 69 Laser beam-assisted bonding Improved solid-state laser Distortion caused by welding: struc- of silicon-silicon for wafer level chip microablation processes with tural stability of reduced models 70 packaging and MEMS packaging 84 tailored pulse trains 101

Modeling the absorption of laser Femtosecond laser welding Synthetic microhairs for sensory radiation on metallic surfaces 71 of glass-glass and glass-silicon 85 applications 102

Direct simulation of Maxwell Laser beam soldering of glass Creating periodic nanostructures equations 72 components using glass solder 86 by three-beam interference 103

Micro-laser dispersing of X-ray Lap welding of transparent 3-dimensional micro- and nano- visible markers on stents 73 PE films with CO2 laser radiation 87 structures inside sapphire produced by selective, laser-induced etching 104 Process-engineering technique TWIST - new process for the laser cladding of brittle for microwelding plastics 88 Changing the refractive index of intermetallic compounds 74 glass materials using a double-pulse Laser-assisted joining femtosecond laser 105 Laser cladding of mesh structures of plastics with metal and on High Pressure Turbine parts 75 ceramic components 89 Laser-induced forward transfer of proteins, cells and active agents 106 Additive manufacturing of aluminum Cutting adhesive seals components for volume production for microtiter plates 90 by selective laser melting 76 Fine cutting 91 Increasing the build-up rate of selective laser melting (SLM) Fine cutting of silicon 92 processes 77 Precision-drilling of shaped holes Modeling of laser treatment of films in steel 93 produced by nano-dispersion 78 In-situ determination of drilling depth during percussion drilling 94

Fraunhofer ILT Annual Report 2007 63 Computer-aided robust design as exemplified by laser cutting

Task Results and Applications

The existing high demands on the qua- The first systematically recorded lity and reliability of products and manu- measurement data are now available, facturing techniques call for the use of and are being used to create meta- robust processes. Processes must be models and model reduction methods. made suitably robust as early as during They also serve as a basis for the the design phase, which involves mo- necessary further development of dels and simulations, and in which mathematical techniques enabling production tolerances and inevitable faster calculation or the characteriza- scattering have to be taken into account. tion of scatter. This is to be demonstrated using laser cutting as one example. The measurement technology employed to record the dynamic behavior of the laser and the system delivers important additional information over and above Method the set objectives, which can help to develop laser cutting processes involv- In order to develop efficient modeling ing high-brilliance beam sources. and simulation techniques that can measure the effects of varying parame- This work is being supported by the ters, experimental results of the cutting Fraunhofer-Gesellschaft in the context process are needed for validation pur- of its MAVO project ‘CAROD – Com- poses and as a complementary data- puter Aided Robust Design’, which is base. These results can be obtained by being coordinated by the Fraunhofer

System and process diagnosis carrying out a full diagnosis of the pro- SCAI. for laser cutting. cess, its determining factors and the outcome. In a series of cutting tests, the lateral movements of the cutting head, the nozzle distance, the laser ra- Contacts diation, the thermal process emissions and the kerf characteristics are re- Dr. F. Schneider, Tel.: -426 corded simultaneously at high tem- [email protected] poral resolution. By means of statistical Dr. M. Niessen, Tel.: -307 analysis, it is then possible to establish [email protected] correlations between these variables Dr. D. Petring, Tel.: -210 and resulting factors such as the [email protected] roughness of the cutting edges and the kerf geometry.

64 Fraunhofer ILT Annual Report 2007 Welding thick steel plates by disc laser

Task Results and Applications

A series of welding tests were carried Weld depths were measured at diffe- out on steel materials with a wall thick- rent welding speeds and with focus ness of up to 10 mm using a disc laser positions ranging from + 2 mm to (TruDisk 8002) with a maximum out- - 7 mm. Due to the high brilliance of put of 8 kW provided by Trumpf Laser- the laser, it was possible to produce technik. very narrow weld seams similar to those created during electron beam welding. At focus positions of 0 mm and below, smooth and even seam Method surfaces were produced, while positive focus positions > 0 mm resulted in The laser beam was fed into the colli- eruptions and irregularities on the seam mation and focusing optics via a 20- surfaces of both materials, particularly meter optical fiber with a diameter of when using the off-axis nozzle. When 200 µm. The optics each had a focal applying the coaxial gas nozzle, a length of f = 200 mm so that, by greater weld depth was achieved with imaging the fiber on a scale of 1:1, the same gas flow rate. The seam qua- a focus diameter of 200 µm was lity and the quality reliability of the produced. Welds were also performed welding process also improved. with a focal length of f = 300 mm and a resulting focus diameter of 300 µm. Welding curves were produced in 10-mm-thick sheets of structural and Contacts stainless steel with a maximum laser output of 8 kW at the workpiece. The V. Nazery Goneghany, Tel.:-159 inert, protective gas argon was fed to [email protected] the welding zone through either an Dipl.-Ing. N. Wolf, Tel.: -448 off-axis or a coaxial nozzle selectively. [email protected] Dr. D. Petring, Tel.: -210 [email protected]

Welds in stainless steel 10 mm, laser output 8 kW. Above: Full penetration weld, feed rate 3 m/min. Below: Partial penetration weld, feed rate 10 m/min, depth 5.6 mm.

Fraunhofer ILT Annual Report 2007 65 Zero-gap lap welding of ZE-Mg sheets

Task Results and Applications

Electrolytically galvanized sheet steel In general, it can be said that the thin- is a widely used material in the car ner the Zn coating, the smaller the size manufacturing industry. By adding a and number of pores. It was shown vapor-deposited magnesium coating, that, as a function of the laser output which is thermally alloyed into the without changing the feed rate, the zinc, it is possible to reduce the zinc increased melt volume (Zn vapor) coating while retaining the material’s generated at 6 kW tends to produce good corrosion properties. The new a greater number of pores. Given a sheets were tested for their welding coating thickness of 3.5 µm, a laser suitability by means of laser beam lap output of 4 kW and a feed rate of welding. 5 m/min, the resulting pores constitute around 3.8 percent of the overall joint surface. This increases to 6.4 percent at 6 kW. The pores are located mainly Method in the transition area between the two join partners. They can be reduced by The tests were carried out using an adapting the laser output and the feed 8 kW disc laser (TruDisk 8002) built by rate. The welds produced on the ZE- Trumpf. The laser beam was guided to Mg sheets have a much better appear- the processing station via a 20-meter- ance and are of a far higher quality long optical fiber with a diameter of than those on the reference material, 200 µm and focused by means of 1:1 which tended towards strong melt imaging. The 0.77-mm-thick sheets, ejections and a large number of pores equipped with Zn coatings of 2.3 µm, across almost the entire range of 2.5 µm, 3.1 µm and 3.5 µm, and a the test due to its thicker Zn coating. 0.3-µm-thick Mg coating, were welded The seam surfaces and roots of all without a gap by means of a square full penetration welds created at feed weld on the lap joint, with the »go-side« rates of up to 10 m/min on the ZE-Mg (Mg coating) on the inside.The sheets, sheets have a high-quality appearance. which were welded with outputs ranging from 4 kW to 6 kW at a feed rate The test sheets were made available of up to 10 m/min, were then analyzed to the Fraunhofer ILT courtesy of DOC to determine their porosity compared Dortmunder Oberflächen Centrum, a to one another and to a reference ma- surface engineering center belonging to terial with a 7.5-µm-thick Zn coating. ThyssenKrupp Steel, which developed 0,5 mm the new coating for these sheets.

Lap weld in ZE-Mg sheets (Zn coating thickness 2.5 µm), laser output: 6 kW, feed rate: 10 m/min. Contacts Above: Seam surface (left) and root (right). Dipl.-Ing. N. Wolf, Tel.: -448 Below: Cross section of the seam. [email protected] Dr. D. Petring, Tel.: -210 [email protected]

66 Fraunhofer ILT Annual Report 2007 Strength testing of CO2 laser MAG hybrid welds

Task Results and Applications

Laser MAG hybrid welding is already For all wall thicknesses up to 25 mm, successfully employed in many areas. the tests resulted in excellent fatigue However, there is a great need to fur- strength values according to Eurocode ther refine the technique so that it can 3, all of them lying in the region above also be used for metal plates thicker FAT Class 100 and extending as far as than 15 mm. In the context of HYBLAS, FAT Class 250. Due to this high seam a European project funded by the quality and other significant advance- RFCS, process methods for laser hybrid ments regarding welding speed and welding of steels with yield strengths the ability to bridge gaps in a single of up to 690 MPA were further deve- pass, which in turn lead to high pro- loped and tested for their suitability ductivity and minimum warping, the by means of comprehensive mecha- laser MAG hybrid welding technique nical-technological investigations. is now also a viable option for highly stressed welds in thick material. Poss- ible areas of application include heavy- duty vehicle construction (e.g. excavat- Method ing machines), shipbuilding, pipeline construction, off-shore engineering For the purpose of the tests, metal pla- and special-machine construction. tes with thicknesses of 12 to 25 mm made of the materials EH 36 and RQT The work described here was carried 701 and prepared for V- or Y-shaped out as part of the EU project »Econo- welding joints were butt-welded in a mical and Safe Laser Hybrid Welding of Fatigue strength diagram for single pass using the laser MAG hybrid Structural Steel« (HYBLAS), which was various plate thicknesses. technique. This was done using a 20-kW sponsored by the Research Fund of

CO2 laser built by Trumpf, a programm- Coal and Steel (RFCS). able welding power source by Fronius and the hybrid welding head developed by the Fraunhofer ILT, the nozzle of which integrates both the laser beam Contacts and the MAG process. The welding patterns used were produced after success- Dipl.-Ing. N. Wolf, Tel.: -448 fully optimizing the process - a necessary [email protected] step particularly for thick-walled plates. Dr. D. Petring, Tel.: -210 The dynamic strength tests were carried [email protected] out in the form of four-point bending tests and tensile tests at the IEHK institute at RWTH Aachen University and at the CORUS company in Rotherham, UK - both of which are partners of the HYBLAS project.

Fraunhofer ILT Annual Report 2007 67 Physical model for root formation and gap-bridging ability during laser welding

Task Results and Applications

Until now, the maximum ability to The maximum bridgeable gap width bridge gaps during laser welding has depends on the thickness of the ma- been determined in purely empirical terial, the surface tension in the root test runs. In future, a physical model area, and the density and downward is to enable the sound assessment and flow rate of the melt, which is a gauge optimization of achievable process of the process dynamics. limits in terms of gap-bridging ability. The developed model explains the quantitative dependency of the gap- bridging ability on the process dyna- Method mics (flow rate), root oxidation and sheet thickness. The effect of measures The energy and mass balance in the such as root shielding gas and horizon- welding joint can be optimized by tal welding position, too, can now be carefully selecting the laser output, the quantitatively assessed. Comparisons Pressure balance of the root area. focusing parameters and the wire feed between theoretical and experimental rate of the filler material. What limits results based on the example of laser the ability to bridge gaps is the diffi- MAG hybrid welding of high-strength culty of retaining the required melt steels 15 mm thick confirm the con- volume in the weld gap. This depends clusive nature of the developed forma- largely on the pressure balance in the lism. root area of the seam. This balance determines the characteristics of the In principle, the model can also incor- root, which can vary between two porate the arc pressure, even though extremes - a convexity to the extent this factor has proven negligible in the that material drops through, or a con- parameter range examined so far. The cavity with the associated notching ef- model is also transferable to numerous fect. The main factors contributing to other welding processes involving root the pressure balance when welding formation, thus helping to design and thick sheets of steel are the gravita- optimize them with greater reliability. tional forces acting on the melt, the dynamic pressure of the melt flow, and the capillary pressure supporting the melt as a result of the surface tension Contacts of the root. Dipl.-Ing. N. Wolf, Tel.: -448 [email protected] Dr. D. Petring, Tel.: -210 [email protected]

68 Fraunhofer ILT Annual Report 2007 Simulating the welding process

Task Results and Applications

The properties of the product after The existing process model for welding welding reflect the prehistory of the describes the form of the capillaries material and the transformations and the temperature field in the sur- during production. The task consists rounding material during surface and of incorporating the change in the full penetration welding. As a free sur- material from a microstructure forma- face or the absorption and reflection tion model into the simulation of the front for the laser radiation the capillary welding process. The additional pro- is part of the solution and is not given. perties of the larger model resulting Multiple reflections of the laser radiation from this combination are to be closely in the capillary are calculated with the studied. Multi-scale thermophysical existing ray tracer. The connection of modeling enables relevant phenomena the laser and welding parameters with with a bearing on material properties the occurrence of multiple reflections to be taken into account at any point is determined as the result (top figure). in the process chain. The spatially distributed temperature in the solid material is determined by analytical solutions of the 2-D heat conduction in the area of the steep ca- Method pillary walls and 3-D heat conduction at the foot of the capillaries. In order to reach a new quality in the combined model, a deeper understand- The work presented was funded by ing of the interaction between tempe- the German Research Foundation DFG rature and stress during solidification in the Excellence Cluster »Integrative and microstructure formation is deve- Production Technology for High-Wage loped. The interaction takes place on Countries«. different scales of time and space, which are determined by the microstructure formation on the scale of nu- cleation and by models of welding on Contacts the scale of the thermal penetration. The dynamic model of welding and the Dipl.-Phys. S. Pfeiffer, Tel.: -153 thermomechanical model of the stres- [email protected] ses are first examined to ascertain the Prof. Dr. W. Schulz, Tel.: -204 sensitive dependence of the resulting [email protected] values on spatially varying material properties and stresses from the prehistory. A partial aspect consists in identifying the areas of qualitatively different solution characteristics (process domains) of the partial models with regard to their combination. The welding model is expanded to include Above: Reflection in the multiple reflection in the capillary and capillary: small feed. spatially three-dimensional properties. Below: Reflection in the capillary: large feed.

Fraunhofer ILT Annual Report 2007 69 Distortion caused by welding: structural stability of reduced models

Task Results and Applications

Computer simulation of distortion The existing simulation of the process caused by welding is not standard model for welding is analyzed in order industrial practice because the quality to be able to describe more precisely of the results is inadequate. To reduce the properties of the heat source for the calculation time, for instance, coupling the process model to the simplified versions of the models are thermomechanical calculation. The applied although their actual proper- transition from heat-conduction weld- ties have not been adequately inves- ing to penetration welding, the tran- tigated. A systematic examination of sition from penetration welding to the structural stability is intended to deep welding, and the transition from highlight the sensitive dependence deep welding to full penetration weld- of the numerical solution on a model ing are identified as process domains. structure which has been reduced in The analysis starts in particular with stages. the question whether the suitable selection of a heat source for the thermomechanical calculation depends Capillary form, temperature field and molten bath iso- on the existing process domains or can therms from the reduced pro- Method be derived solely from the geometrical cess model for surface welding. shape of the weld seam. The examination focuses on three industry-relevant components (gear The work presented is funded by the wheel, microcomponent, car body Research Association Steel Application component) and three steel materials. FOSTA. The numerical and analytical solutions for distortion and internal stresses are initially compared on components of reduced geometrical complexity. The Contacts sensitivity of the simulation results to the boundary conditions and structure Dipl.-Phys. S. Pfeiffer, Tel.: -153 of the model is examined. To gain a [email protected] heat source for the FEM welding dis- Prof. Dr. W. Schulz, Tel.: -204 tortion simulations, an efficient simula- [email protected] tion of the reduced process model for surface and full penetration welding is developed.

70 Fraunhofer ILT Annual Report 2007 Modeling the absorption of laser radiation on metallic surfaces

in y direction. The wave equation for Task the Ey component describes the case of vertical polarization, the wave equation The absorption of laser radiation on for the Hy component describes the metallic surfaces depends not only on parallel polarization. The two other field the optical properties of the metal, but components differing from zero in each also, and very sensitively, on the angle case can then be calculated from the of the Poynting vector relative to the Maxwell equations. metal surface. This is important in particular in the context of cutting and welding using laser radiation, because here angles of incidence are reached Results and Applications which correspond to the Brewster angle. A big difference in absorption The graphic shows the absorption occurs as a function of the radiation along a metallic surface calculated by polarization. The Fresnel formulas are means of the Fresnel formulas, using normally used for calculating the ab- the Poyting vector to determine the 10 µm sorption, but strictly speaking these are angle of incidence and the absorption only valid for plane waves and flat sur- as provided by the BPM method. The faces. To determine the validity limits mean angle of incidence is 87°. There Absorption along a metallic sur- of the Fresnel formulas and possible are only slight differences between the face of p-polarized radiation. The mean angle of incidence is deviations for the case of Gaussian Fresnel formulas and the BPM solution. 87°, the wavelength 1.06 µm. beams, the wave equation for the pro- The complex refraction index is pagation of a radiation field is solved 20-i20. with the Gaussian profile. Contacts

Dr. R. Wester, Tel.: -401 Method [email protected] Prof. Dr. W. Schulz, Tel.: -204 A time-independent two-dimensional [email protected] wide-angle beam-propagation method (BPM) is used for solving the Maxwell equations. In this method, wave propagation is separated in the main direction of propagation by applying an SVE of a higher order, so that local resolution of the numerical process can be distinctly reduced. In the main direction of propagation z all material properties are constant, as are also all the field variables

Fraunhofer ILT Annual Report 2007 71 Direct simulation of Maxwell equations

Task Results and Applications

On the absorption front, such as the The reflection, transmission and absorp- drill-hole wall, the surface of the cation of a plane wave on a flat boundary pillaries in welding or the cutting front, layer can be stated analytically. The the laser radiation is reflected, ab- accuracy of the numerical solution is sorbed and diffracted. Reflection, checked by reproducing the Fresnel absorption and diffraction change the formulas (top figure). For the rigorous direction and amount of the Poynting solution of the Maxwell equation, a vector and thus the laser beam tool. nested grid is inserted for discretization, on which electric (E) and magnetic (H) The beam-forming effect of the ab- field components are laid. The discreti- sorption front on the laser radiation is zation of the evolution equation for the examined closely, taking into account electric and magnetic field is shown in the wave properties and the boundary the lower figure. The field amplitude of conditions of strongly absorbing media. the electric field is the solution of the model task under consideration (middle figure). By comparing solutions from the FDTD method with boundary ele- Method ment methods (BEM) and methods which take into account higher orders For the rigorous solution of Maxwell of the slow varying envelope (SVE) ap- equations, the finite difference time proximation, the solution characteristics domain (FDTD) method is applied. of the tasks are stated and the effect of The material equations of Drude and the absorption front on the beam form Lorentz are used to describe the op- are determined. The result is a beam tical properties of the material. For the forming process for the incident laser conditions on the outer edge of the radiation with which the quality charac- calculation area, absorbing boundary teristics of drilling, welding or cutting conditions of the PML type (perfectly are obtained. matching layer) and periodic boundary conditions are selected. The work presented is funded by the German Research Foundation DFG in the Excellence Cluster »Integrative Production Technology for High-Wage Countries«.

Contacts

Dipl.-Phys. U. Eppelt, Tel.: -163 [email protected] Prof. Dr. W. Schulz, Tel.: -204 Above: Degree of reflection [email protected] over the angle of incidence. Middle: Field amplitude of the electric field. Below: FDTD pattern of the numerical calculation.

72 Fraunhofer ILT Annual Report 2007 Micro-laser dispersing of X-ray visible markers on stents

Task Results and Applications

After implantation of a stent in the Using fiber lasers with a high beam human body, a check is performed to quality, controlled melt depths can be ensure that the blood vessel is not ob- achieved on nitinol substrates with a structed and that the implanted stent thickness of 200 µm. Due to the diffe- has been positioned exactly in the rence between the melting tempera- human vascular system. However, if tures of the two materials (nitinol: the stent is made of nitinol (a shape 1310 °C, tantalum 3017 °C), the tan- memory alloy), the low density of the talum particles are not melted and material makes the stent structure al- evenly distributed throughout the mol- most or completely indistinguishable ten substrate material. When the melt from surrounding tissue and bone solidifies, the tantalum particles form when the final X-ray examination is a layer that is impenetrable by X-rays, performed. This problem can be reme- thus significantly increasing X-ray vi- died by creating X-ray visible markers sibility by contrast with the substrate 2 mm made of tantalum, niobium or plati- material (bottom picture). By precisely num on defined parts of the stent. controlling the applied laser energy and ensuring a precise and even input of the filler material, highly reproducible results can be obtained using Method this process. In a final fabrication stage, the laser dispersed areas are The first step in producing the X-ray vi- finished by electropolishing. sible markers is to cut areas, measuring 1 x 2 mm, out of the nitinol tube, pro- jecting from the ends of the stent structure (spoons, top picture). X-ray Contacts Above: Stent with cut spoons. Below: X-ray image of a stent visible markers made of tantalum are with tantalum spoons created then created on the spoons by means Dipl.-Ing. T. Jambor, Tel.: -193 by laser dispersing. of micro-laser dispersing. In this me- [email protected] thod, the laser radiation creates a melt Dr. K. Wissenbach, Tel.: -147 pool on the surface of the substrate, [email protected] into which the powdered tantalum filler material is added.

Fraunhofer ILT Annual Report 2007 73 Process-engineering technique for the laser cladding of brittle intermetallic compounds

Task Results and Applications

Materials based on intermetallic com- A heating stage (100 x 150 mm2, top pounds such as Ti-Al, Ni-Al or Fe-Al are picture) assembled of ceramic heating renowned for their excellent mecha- elements, to which modular units can nical and chemical properties at high be added to extend the heated surface temperatures. In conjunction with their area, is used for preheating. The inert- low density, this predestines them for gas hood covers a surface area of use in aerospace or engine applications 400 x 600 mm (top picture). The laser as a substitute for conventional high- optics and powder feeding nozzle are temperature materials based on nickel integrated in the hood. The underside and cobalt. They nevertheless present is sealed with metallic brush strips. one drawback: their elevated brittle- Welding tests at temperatures of up ness at room temperature, which to 950 °C were performed using this causes problems when they are pro- experimental setup (middle picture). cessed or machined. To avoid the ge- Crack-free results were obtained when neration of cracks, forming processes joining or coating titanium aluminides and certain coating and joining proces- at preheating temperatures in excess ses have to be carried out within nar- of 800 °C. The middle illustration rowly defined process windows. The shows a wear-resistant coating made Fraunhofer ILT is developing a process- of a TiAl alloy enriched with 40 per-

engineering technique that will enable cent by volume of TiB2 particles. Gra- intermetallic compounds to be joined dual, controlled cooling after the laser or coated without risk of cracking in a cladding operation reduces the risk reduced oxygen atmosphere. of crack formation during the cooling phase. The use of an inert-gas hood significantly reduces oxidation of the sample. Potential applications envi- Method saged for this process-engineering technique include applying wear-resis- To avoid the generation of cracks dur- tant coatings to engine valves and the ing laser cladding, a preheating device repair of turbine blades (regeneration is being designed that will allow of worn-down volume or welding-on temperatures of up to 1000 °C to be of blade segments). reached. A mobile inert-gas hood is also being designed and built to reduce oxidation of the workpiece during processing. Experimental trials are being Contacts conducted on the titanium aluminide group of materials. Identical-type alloys Dr. A. Weisheit, Tel.: -403

with and without additions of TiB2 are [email protected] used as the filler material. Dr. K. Wissenbach, Tel.: -147 [email protected]

Above: Heating stage with inert- gas hood. Middle: Heated sample (950 °C). Below: Micrograph of a laser-

clad coating of TiAl + TiB2. 0,05 mm

74 Fraunhofer ILT Annual Report 2007 Laser cladding of mesh structures on High Pressure Turbine parts

Task Results and Applications

The aim is to apply mesh structures By selecting suitable processing para- made of the nickel base super alloy meters, mesh structures with a track Inconel® 625 on the surfaces of High width of 340 µm and a maximum Pressure Turbine (HPT) parts of aircraft height of 500 µm at their intersections engines made of the single-crystalline can be successfully deposited on HPT solidified alloy CMSX-4 by means of liner 1 parts. The system can also pro- laser cladding. The mesh structures duce structures of down to 60 µm in increase the bonding and shearing width if necessary. TBCs are currently strength of the Thermal Barrier Coa- being applied to the first mesh-clad ting (TBC), which is subsequently parts by Atmospheric Plasma Spraying applied by Atmospheric Plasma Spray- at the Jülich research center. The coating (APS). The defined mesh structures ings are then being tested for increased feature a cross-sectional width of bonding and shearing strength by the 340 µm and a maximum height of customer. 10 mm 500 µm at their intersections. This work is being carried out in collaboration with Rolls-Royce and forms part of the publicly funded project Method »Engine 3E«.

The laser cladding process is performed using an ytterbium fiber laser (IPG YLR- 200) with an emitted wavelength Contacts of λ = 1080 µm and a maximum output power of PL = 250 W. The decoupled Dipl.-Ing. B. Burbaum, Tel.: -535 10 mm laser light is guided by optical fibers [email protected] from the laser beam source to the Dipl.-Ing. (FH) P. Albus, Tel.: -479 Above: CAD model of HPT handling system and through a fo- [email protected] liner 1 with NC tool paths. cusing lens to the processing location. Dr. I. Kelbassa, Tel.: -356 Below: Deposited mesh struc- The beam diameter in the focus is [email protected] tures on HPT liner 1 part. df = 60 µm. In order to obtain the required track width, the laser beam is defocused to a diameter of 280 µm. Powder made of the nickel base super alloy Inconel® 625 is used as additive material. The NC tool paths stringently required for laser cladding are created on the basis of a CAD model of the HPT liner 1 using the CAD/CAM system DCAM 5. The 3-axis Varilas plant built by Schuler Held is used as the handling system.

Fraunhofer ILT Annual Report 2007 75 Additive manufacturing of aluminum components for volume production by selective laser melting

Task Results and Applications

The additive process of selective laser The high reflectivity and thermal con- melting (SLM) is used in the direct in- ductivity of aluminum by comparison dustrial manufacturing of metallic with steel permits component densities functional components. Industry’s ac- approaching 100 percent to be achieved ceptance of the process and the extent with a laser output of 150 W or higher to which it is employed depends partly and a scanning velocity of 100 mm/s. on the range of materials that can be At a laser output of 250 W, the scann- processed and the availability of knowing velocity can be increased to ledge on the mechanical properties of 500 mm/s. At a lower scanning velo- the components. The Fraunhofer ILT is city of 50 mm/s or at a higher preheat- currently qualifying SLM for the alumi- ing temperature of 300 °C, a more num die-casting alloy AlSi10Mg as part ductile microstructure is produced, of the BMBF’s »Alugenerativ« project. expressed as lower hardness, lower Additive manufacturing by SLM repre- strength and higher breaking elonga- sents an economical alternative to the tion. The results of tension and fatigue various types of mold casting, such tests demonstrate that the mechanical as die casting, when producing series- properties are at least equivalent to identical functional prototypes, one-off the strength parameters of series-pro- parts and short-run batches. The use duced components made of die-cast of additive techniques to manufacture AlSi10Mg according to EN 1706 speci- such parts on an industrial scale is sub- fications (see top figure). This finding ject to the fundamental requirement is of major importance to future indus- that their mechanical properties should trial applications of the technology. at minimum match those of conven- In the next stage of the project, we tionally manufactured components. intend to investigate the correlation between process parameters and heat treatment, microstructure and mechanical properties in more detail, and de- Method termine the effect of subsequent heat treatment on the mechanical proper- The primary objective when qualifying ties. Other aluminum alloys will also a material for SLM is to obtain a com- be qualified for industrial use. The first ponent density approaching 100 per- demonstrator components (see lower cent without any cracks or fusion de- figure) are being manufactured. fects. This involves evaluating the process parameters, especially scanning velocity and laser output power, required to produce components with a Above: Tensile strength R m density approaching 100 percent. To Contacts of SLM samples made from AlSi10Mg as a function of scann- assess the effect of scanning velocity ing velocity, preheating tem- and preheating on tensile strength, Dipl.-Ing. D. Buchbinder, Tel.: -488 perature, and the direction in yield strength, breaking elongation, [email protected] which the component is built up. Middle and below: High vol- hardness and fatigue limit, test geo- Dr. K. Wissenbach, Tel.: -147 ume-production AlSi10Mg valve metries are then manufactured at [email protected] manufactured using SLM (in different scanning velocities with and cooperation with Festo AG & without preheating, and the resulting Co. KG). mechanical properties are compared.

76 Fraunhofer ILT Annual Report 2007 Increasing the build-up rate of selective laser melting (SLM) processes

a whole. To avoid this, the beam dia- Task meter has to be modified. Experimen- tal investigations were performed in The Cluster of Excellence »Integrative which the process parameters scann- Production Technology for High-Wage ing velocity, layer thickness and scan Countries«, of which the Fraunhofer line spacing were adapted to a higher ILT is a member, is pursuing the long- laser output power and beam diameter. term objective of increasing the com- Process windows defined by suitable petitiveness of German production sets of parameter values can be identi- technology. One of the key research fied on the basis of the smoothness issues concerns solving the dilemma of the generated layers, which permit that opposes economies of scale and an even deposition of powder and scope, through the creation of new the build-up of test structures with a added value structures that permit density approaching 100 percent. low-volume manufacturing at costs of mass production while retaining the ability to satisfy the market demand for individualized products at the same Results and Applications time. From a technological point of view, additive manufacturing tech- For the first time, experiments using niques with their almost infinite geo- high-alloy steel (1.4404) demonstrated metrical variability represent one of that it is possible to build up test the areas of greatest potential. A major structures with a density approaching cost factor in the SLM process deve- 100 percent by widening the beam loped by the Fraunhofer ILT for the diameter from 0.2 mm to 0.8 mm and processing of metallic materials is the 1.2 mm respectively and increasing the manufacturing cycle time, which most- laser output from 250 W to 650 W. ly depends on the volume of material The highest build-up rate achieved was that has to be built up to produce the 6.5 mm3/s, which represents a greater components. For economic reasons, than fivefold increase with respect to Above: Selective laser melting greater cost-efficiency needs to be the present state of the art (approx. of a powder film. achieved by increasing the build-up rate. 1.2 mm3/s). The next stage of the pro- Below: Typical application: ject involves constructing a prototype Mold insert with contoured plant with a laser output of 1 kW that cooling channels manufactured using SLM. will be used to adapt the results of the Method fundamental research to the manufacture of real-life components, such The experiments conducted to date in- as mold and die inserts. This will make dicate that there is only limited scope the additive manufacturing technique to increase the build-up rate on the by means of selective laser melting a basis of higher laser output power and more economical and hence attractive a corresponding increase in the scann- option for many users. ing velocity at a constant beam diameter. Increasing the laser output power while maintaining a constant beam diameter has the effect of in- Contacts creasing the light intensity at the point of processing. This in turn leads to a Dipl.-Ing. H. Schleifenbaum, Tel.: -126 higher incidence of spattering, which [email protected] has a negative effect on the process as Dr. K. Wissenbach, Tel.: -147 [email protected]

Fraunhofer ILT Annual Report 2007 77 Modeling of laser treatment of films produced by nano-dispersion

commonly used laser wavelengths. Task This heat input was then used in a 3-D heat transfer equation for composite Films produced by nano-dispersion of- materials consisting of a nanofilm dis- ten require subsequent heat treatment persed on a glass or polymer substrate in order to obtain the desired functio- to calculate the resulting temperature nality (e.g. electrical conductivity, abra- time cycles and the heat penetration sion resistance). The heat treatment depth. processes conventionally used for the functionalization of nanoparticle films present the drawback of overlong process cycles in excess of 1 hour (limiting Results and Applications the possibility for inline monitoring) and an extremely high thermal load. A process window defined in terms of In many cases, these processes necessi- process temperature and holding time tate temperatures that lie above the was determined by assigning the ex- decomposition temperature of certain perimentally established functional substrate materials such as glass and properties to the calculated tempera- polymers. ture cycles (upper figure). The process parameters were mathematically opti- Above: 3-D temperature field. A laser process is therefore being deve- mized with respect to processing rate Blow: Temperature-depth pro- loped for the thermal post-treatment per unit area and heat penetration files as a function of laser out- of films produced by nano-dispersion depth (lower figure) on the basis of put power, beam diameter and scanning velocity. on glass and polymer substrates. this process window, for the purpose of generating functional films by means of laser treatment.

Method

There are no references in current lite- Contacts rature providing guidance on the extent to which furnace processes can Dr. N. Pirch, Tel.: -403 be replaced by high-speed thermal [email protected] processes such as those implicit in laser Dr. K. Wissenbach, Tel.: -147 treatment. A series of experiments [email protected] therefore had to be planned to obtain statistical data by systematically varying the process temperature and the holding time, in order to define a process window. These plans were accompa- nied by a process model that was used to determine the requisite process parameter settings at each selected test point. The process model was based on calculations of the proportion of laser light absorbed by the nanoparticle film, taking into account the variation in optical properties as a function of the wavelength, and the effect of multiple reflection at the interfaces as a function of the film’s thickness for

78 Fraunhofer ILT Annual Report 2007 New applications for high-strength steel sheets through local heat treatment

Task Results and Applications

The automotive industry is increasingly The upper figure shows a car bumper producing body or chassis parts from made of martensitic steel with a tensile sheets of high-strength steels (e.g. strength of 1400 MPa. Local softening dual-phase or martensitic steel) in or- of the steel made it possible to form der to save weight and improve vehicle the critical area of the bend without safety. These steels are generally cold- producing any cracks. Crash tests have formed in the high-strength state in shown that the bumper’s high per- which they are delivered. However, formance has been maintained, while their high strength limits the degree its geometrical design possibilities have to which they can be formed and thus been significantly increased. also the range of components for which they can be used. If the local The softening of steel can also be used formability of such steels were im- for applications outside the automotive proved by softening them through industry, such as for the steel caps of heat treatment, their range of applica- safety shoes. These are conventionally tions could be significantly expanded, made of hardenable steels, which are thus opening up new design possibilities. initially formed in their soft state and subsequently tempered. The bottom picture shows shoe caps made of a

dual-phase steel (Rm = 1000 MPa). The Method critical area of the 90° bending angle was successfully formed by locally sof- Suitable process parameters for locally tening the plates. The subsequent crash softening high-strength steels have test showed that they had the same ab- already been determined in a basic sorbent properties as caps made of con- research project. They are now being ventional steels (bottom picture, left). tested in practice on selected sample components. An FEM simulation of the forming process is carried out to determine which sections of the plate will Contacts be deformed to a critical degree and need to be treated. These are then Dipl.-Ing. D. Maischner, Tel.: -361 heat-treated using Nd:YAG laser radia- [email protected] tion with temperature control. Dr. A. Weisheit, Tel.: -403 [email protected] Dr. K. Wissenbach, Tel.: -147 [email protected]

Above and Middle: Reshaped bumper made of martensitic steel with a softened zone in the bending radius (sheet thickness 1.6 mm); Source: Wagon Auto- motive. Below: Locally softened shoe caps (left: after crash test) made of dual-phase steel (sheet thickness 1.6 mm); Source: ISCO.

Fraunhofer ILT Annual Report 2007 79 Laser polishing of glass molds

Task Method

Laser polishing is a new, automated First of all, the process parameters production technique for polishing such as scanning speed, laser output metal surfaces, in which the material power and trace offset were adapted is smoothed by remelting a thin surface to the material 1.2782, which is fre- layer (< 100 µm). The aim was to de- quently used for glass molds. The monstrate the basic suitability of this overall surface area of the mold was process for tool and mold construction divided into subareas for processing. A using the example of a glass mold. The special »border strategy« was applied machine tool required to do this was to ensure that the borders between developed in a project called »Polar«. the subareas were not visible, or only It comprises a milling center built by faintly. A software system specially Hermle, which was adapted for laser developed for path generation helped polishing by integrating a beam source to program the routings more quickly. including optics with a beam expander and a 3-D scanner, plus a process chamber. Results and Applications

After setting and programming the system, the polishing process was carried out fully automatically. By adapting the process parameters, it was possible to achieve a roughness of Ra = 0.15 - 0.2 µm on coarsely Laser-polished glass mold (front right), ground glass mold (front left), cast stem ground glass molds by laser polishing. of a wine glass (background). No manual finishing was required after the laser process, which meant that each half of the mold was completely polished in just 20 minutes. The laser- polished molds were subsequently tested in production, and demonstrated a surface quality suitable for standard wine glasses.

Contacts

Dipl.-Ing. T. Kiedrowski, Tel.: -282 [email protected] Dr. K. Wissenbach, Tel.: -147 [email protected]

80 Fraunhofer ILT Annual Report 2007 Dual gloss effect created by laser polishing

Task Results and Applications

A structured or grained effect is often By modulating the process parameters required when manufacturing plastic laser power and scanning velocity, components such as automobile in- it was possible to set locally defined strument panels. The tools used to values for roughness and hence for produce these components therefore degree of gloss. The range of gloss have to be structured accordingly. The could be varied from the original mat method most commonly used is photo- roughness to high brilliance by select- chemical etching. The structures are ing the appropriate laser power and often designed to imitate natural ma- scanning velocity. Resolution and pro- terials such as leather or to provide a cessing speed are significantly depen- technical function. They also have to dent on the time constant of the laser fulfil demanding requirements in terms beam source, i.e. the time required by of touch and appearance. The aim of the beam source to change the laser this project is to create variable optical power. The lower the time constant, 2 cm effects using the new manufacturing the greater the processing speed and technique of laser polishing by selec- resolution. Tool inserts with an etched tively finishing defined areas of the tool surface imitating the grained structure structure, e.g. only the indentations. of leather were polished to an edge When the component is removed from definition of < 20 µm and subsequent- the mold, only the raised sections of ly used to produce plastic components the structure are brilliantly smooth. exhibiting a dual gloss effect. The pre- The new method enables surfaces to sently obtainable processing speed is be produced that were not possible 3 min/cm2 at a resolution of 100 dpi. before, or required considerable time and effort. In the further course of the project, 50 µm it is planned to transfer these results to three-dimensional components, e.g. automobile instrument panels, and to Method reduce the processing time.

Experimental investigations of selective, locally resolved laser polishing were performed on tool inserts made of the Contacts material 1.2343 with rough-grained and fine-grained surfaces. The process in- Dipl.-Phys. A. Temmler, Tel.: -299 volved scanning the surface in meander- [email protected] 50 µm ing loops, while the laser power and the Dr. K. Wissenbach, Tel.: -147 scanning velocity in the processing path [email protected] were modulated as a function of the existing structure (only the indentations are polished). Above: Section of a tool insert with photochemically etched leather-grain structure (mat and laser-polished). Middle: Edge definition between the etched zone and the laser-polished zone. Blow: Surface of a plastic component with a dual gloss effect 2 cm created by laser polishing.

Fraunhofer ILT Annual Report 2007 81 Laser beam microwelding of 2-D optical waveguide arrays

Task Results and Applications

Optical waveguide arrays are needed To optimize quality, a new approach for the parallelization of optical trans- based on a fiber laser and scanner mission routes. To assemble these ar- optics is adopted. The stability of the rays, support systems of the highest molten bath is distinctly improved by precision in the sub-micrometer range an oscillation movement (wobbling) are required. A new approach involves imparted to the feed. A non-reprodu- joining together ultra-precisely struc- cible transition from keyhole welding tured carrier plates for optical fibers to heat-conduction welding is not ob- to form an array. These carrier plates servable. The roughness of the surface feature parallel grooves spaced 250 µm is also reduced. By means of white apart which serve as passive adjust- light interferometry, it is possible to ment structures for alignment of the demonstrate a reduction in the Ra optical waveguides. For this purpose, values from 4 - 5 µm without wobbl- the carrier plates are butt-welded onto ing to 2 - 2.5 µm with an imparted os- ribs (width 75 µm). cillation movement. If the parameters are suitably selected, there is no observ- able melting of the 75-µm-wide ribs.

Method Such arrays can be used as optical waveguide plugs for parallel transmis- The alloy CuNi18Zn20 used for the sion or as a redundant system for the assembly component comprises 62 % transmission of large volumes of data. copper, 20 % zinc and 18 % nickel The regular arrangement of the optical (German silver). Due to its alloy ele- waveguides at a distance of 250 µm ments and surface properties, German from each other means that they can silver is comparable with brass when be coupled onto VCSEL arrays. used for laser beam welding. The high Above: Welded 2-D optical waveguide array. reflectance of both metals makes it Below: Detailed image of a weld difficult to couple the laser radiation. seam at the rib and base transition Moreover, metals with a high proportion of two carrier plates. of zinc represent a particular challenge Contacts for welding applications because the evaporation temperature of the zinc at Dipl.-Ing. F. Schmitt, Tel.: -322 around 900 °C is below the melt point [email protected] of the other alloy elements. During the Dr. A. Gillner, Tel.: -148 welding process the zinc evaporates [email protected] and suddenly escapes from the weld volume, taking liquid melt with it. This causes pores in the seam, uncontroll- able welding splashes and an irregular upper bead.

82 Fraunhofer ILT Annual Report 2007 Laser beam-assisted bonding of silicon and glass for wafer level packaging, MEMS packaging and display packaging

Task Results and Applications

In hybrid microsystem technology, the To increase flexibility and process relia- semiconductor industry and micro- bility, a fiber laser with a wavelength electromechanical systems (MEMS), fra- of λ = 1090 nm was deployed in com- gile microelectronic components such bination with a rapid galvanometer as uncased silicon chips are encapsu- scanner, as an alternative to localized lated at wafer level (wafer level packag- contour joining with a focused laser ing). The encapsulation usually takes beam. Laser beam place by means of large-area joining techniques such as wafer fusion bond- By imparting an oscillation motion ing or anodic bonding. These processes during the feed, scanners enable the exert a high thermal loading on the requisite flexibility to be achieved with sensitive components and exhibit low regard to bond seam width and geo- flexibility with regard to the joint geometry. In addition, this »wobble func- metry. As an alternative and additio- tion« has a positive impact on the heat Circular nally to wafer bonding, the laser en- influence zone during joining, with the oscillation ables the heat influence zone and the result that no melting occurs on the distortion it causes to be minimized joining front. through exact control of the energy deposition. The bonding results achieved generally show that fiber lasers combined with scanners can be used for bonding silicon and glass. In addition, it is possible Method to produce melt- and crack-free bonded connections at feed speeds of up to The principle of the laser beam bond- 10 mm/s without the need for thermal 1 mm ing technique is based on transmission process control. As a result, the tech- joining, in which one of the parts nique is also suitable for the assembly Above: Feed movement with being joined is transparent for the laser of micro-optical components on semi- imparted circular oscillation radiation applied (e.g. glass) and the conductor-based lighting elements using scanners. other is absorbent (silicon). The main such as LEDs. Below: Coaxial illumination of part of the energy in the laser beam is bonded silicon/glass samples using a scanner. implemented as heat at the interface of the parts being joined and the contact point is specifically, locally and Contacts selectively heated. After appropriate preparation of the surface, the intro- Dipl.-Ing. F. Sarı, Tel.: -358 duction of heat creates a high-strength [email protected] oxygen bridge between the two join- Dr. A. Gillner, Tel.: -148 ing partners. [email protected]

Fraunhofer ILT Annual Report 2007 83 Laser beam-assisted bonding of silicon-silicon for wafer level chip packaging and MEMS packaging

Task Results and Applications

Microelectromechanical systems In cooperation with the Fraunhofer (MEMS) such as acceleration sensors, Institutes IZM and IWM, it was shown silicon-based pressure sensors and rate- that transmission joining with laser of-rotation sensors combine sensitive radiation of wavelength λ = 2 µm and electrical, mechanical, thermal and also a laser spot of 50 µm can be applied to chemical functions. As these systems produce high-strength silicon-on-silicon are particularly prevalent in the auto connections without melt formation. industry, they must be encapsulated to Examinations of the joint zones show ensure long-term stability. The encap- a melt-free connection which shows a sulation is usually provided by large- high strength of the joining area exceed- area joining techniques such as silicon ing the strength of the base material. wafer bonding. Along with wafer-to- wafer bonding, chip-to-wafer bonding, The new selective joining technique 200 µm in which individual chips are positioned provides a process with which thermally and bonded on pre-processed silicon and mechanically sensitive silicon com- wafers, has recently come to the fore. ponents can be joined at high speed The joining techniques used up to now and with high precision. can exert considerable thermal and mechanical loadings on sensitive circuits and especially on micromechanical components such as sensors. As an alterna- Contacts tive and a supplement to wafer bonding, the laser enables the heat influence Dipl.-Ing. F. Sarı, Tel.: -358 zone and the distortion it causes to be [email protected]

100 µm minimized through exact control of the Dr. A. Gillner, Tel.: -148 energy deposition. [email protected]

Above: IR transmission image of a spiral-shaped bond between two silicon substrates. Below: Fractured silicon surface Method after micro-chevron testing. The principle of laser bonding is based on transmission joining, in which the laser radiation penetrates the parts being joined and is absorbed at the connection point by applying suitable measures. The energy in the laser beam is transformed into heat at the interface of the join partners.

For the material pairing of silicon and silicon, a new type of fiber laser beam source with a wavelength of 2 µm is used along with absorbing intermediate layers, which act as functional conductive layers on the chip.

84 Fraunhofer ILT Annual Report 2007 Femtosecond laser welding of glass-glass and glass-silicon

types of glass, and of glass and silicon, Task with ultra-short pulsed laser light. A process control system for fs joining is Ultra-fast engineering is becoming an also being devised by monitoring the established discipline in the engineer- laser process. ing domain. The present demand for highly precise, customized products calls for the development of new ultra- precise manufacturing techniques, Results and Applications such as in microengineering. In the current trend towards miniaturization Bonds were achieved when joining of optical components and systems technical glass materials (D263 and (such as micro and nano optics, AF45 Schott) to substrates of silicon or OLEDs1, VCSELs2), the joining of glass- dissimilar glass using ultra-short pulsed glass and glass-silicon with bonding laser light. By selecting suitable para- zones in the µm range represents a meters, it was possible to produce significant challenge which until now crack-free weld seams 20 µm wide 20 µm has only been mastered to a limited and 30 µm deep in glass-glass bonding extent. The innovative OLED light (see upper and middle figures). The source requires a higher-quality joining bonding strength is extremely high, seam, as it needs to be gas-tight as demonstrated by the fact that glass Glass (impermeable to oxygen and water residues can be detected on the silicon vapor). when test samples of a glass-silicon bond are separated (lower figure).

One of the purposes of joining glass Silicon Method materials and glass semiconductors is to seal housings, such as those of Welding with ultra-short pulsed laser OLEDs1 in the lighting industry or light (pulse duration t < 1 ps) is being MEMSs3 and MOEMSs4 in the semi- tested as a novel method of joining conductor industry. similar and dissimilar classes of material, such as glass-glass and glass- Silicon silicon. Through multi-photon proces- 1 OLED: Organic Light-Emitting Diode 2 VCSEL: Vertical-Cavity Surface-Emitting Laser ses, the laser light is absorbed exclu- Glass sively in the focus at sufficiently large 3 MEMS: Micro-Electro-Mechanical System intensities of > 1010 W/cm2, and the 4 MOEMS: Micro-Opto-Electromechanical System glass is melted locally in the focus 3 (approx. 1 - 100 µm ). The short im- 20 µm pact time of the pulses means that heat does not penetrate very deeply, Contacts causing less thermal stress than longer Above: Micrograph of a glass-glass weld seam pulse durations. This makes it possible Dr. A. Horn, Tel.: -205 (microscope image). to micro-weld inside the volume of [email protected] Middle: Micrograph of glass materials with a weld seam in Dr. I. Kelbassa, Tel.: -356 a glass-silicon weld seam (SEM, etched). the µm range. The overall objective of [email protected] Below: Surface of a silicon these tests is to establish material- and substrate after separation of process-based principles for qualifying the glass-silicon bond (SEM). the joining of similar and dissimilar

Fraunhofer ILT Annual Report 2007 85 Laser beam soldering of glass components using glass solder

Task Results and Applications

Glass solders, which are typically pro- By applying a thermally optimized cessed at temperatures above 500 °C, process strategy, overheating of the are now widely used for hermetically component can be avoided. An even sealing glass components and in appli- level of heating, melting and connec- cations where electrical insulation is tion-formation of the glass solder in required. As the durability and mecha- the joining zone is also achieved. High nical loadability of a glass solder con- temperature gradients are avoided nection depend on the stresses arising, in this approach, which results in most joining processes are subject to a homogeneous, crack- and bubble-free temperature-time profile, which means soldering. a high temperature loading for the entire assembly. For many applications, Possible applications of this technique e.g. the encapsulation of microsensors include sealing microsensors and micro- and microactuators, these necessary actuators, encapsulating organic process temperatures are too high, and lighting devices and producing liquid as a result individual components are crystal displays. View of a laser-soldered soda-lime glass sample. damaged by diffusion processes. The need for a low-temperature joining technique or a joining method where the introduction of energy is locally Contacts limited is therefore apparent. Dipl.-Ing. H. Kind, Tel.: -135 [email protected] Dr. A. Gillner, Tel.: -148 Method [email protected]

Laser beam soldering using glass solder makes it possible to concentrate the energy needed for making the connection so that it is spatially limited to the joining zone and thus to minimize the total increase in heat of the components being joined. The energy necessary for melting, wetting and connecting the parts being joined is based on the absorption of the laser radiation applied in the glass solder. The local introduction of energy must be adjusted in terms of time and geometry in such a way that the viscosity needed for adequate flowing and wetting is achieved in the glass solder and the evaporation of glass solder constituents is avoided.

86 Fraunhofer ILT Annual Report 2007 Lap welding of transparent PE films with CO2 laser radiation

Task Results and Applications

Polymer films can be lap welded with- At an average laser power of P = 28 W out contact by means of Nd:YAG, and a feed speed of v = 100 mm/s, the diode or fiber laser radiation (wave- laser beam is moved over the films by length in each case around 1000 nm) galvanometer scanner in the horizontal if the upper film is transparent and the x-y plane, and with a defocused beam, lower film is absorbent. If both joining a seam of 1.5 mm width is produced. partners are transparent, the lower The two films are pressed together by film can be provided with suitable being stretched over a crowned sur- absorbers, but this often destroys the face. This is all it takes to form the clo- transparent appearance of the weld. sure needed for welding. The cooling Alternatively, lasers are available with problems that exist for the tool and wavelengths for which both films environment in the hot wire welding possess adequately high absorption process currently used are avoided by capability. Within a feasibility study the laser method. The cost-efficiency the aim was to examine whether trans- of both processes is currently being parent 150-µm PE films can be welded compared. by means of CO2 laser radiation.

Contacts Method Dipl.-Phys. G. Otto, Tel.: -165 Although nearly all plastics exhibit very [email protected] high absorption in the infrared spectral Dr. A. Gillner, Tel.: -148 range, thin polyethylene (PE) possesses [email protected] optical properties which are well adapted to lap welding at 10.6 µm, the wavelength of the CO2 laser. LDPE film with a thickness of 73 µm, for example, 150-µm transparent PE films welded using CO2 laser radiation. has a reflectance of R = 5 %, a trans- Seam width 1.5 mm, feed mittance of T = 85 % and an absorp- 100 mm/s, laser power 28 W, tance of only A = 10 %. This results circle diameter 17 mm. in a penetration depth of 656 µm. The upper film is therefore sufficiently transparent for the lower joining partner to melt.

Fraunhofer ILT Annual Report 2007 87 TWIST - new process for microwelding plastics

Task Results and Applications

Laser beam welding of plastics has A reduced heat influence zone with been the subject of applied research flexible adjustment of the weld seam since the early 1990s and has mean- width between 130 µm and 500 µm as while crossed the threshold to industrial well as the fundamental characteristic application. The scope of this process that the components are invisibly extends from the production of welds welded with little distortion are the for microengineering components to outstanding features of the TWIST the reproducible and process-reliable technique. In particular current deve- joining of large components with highly lopments in microfluidic components loadable welds. As a result of new call for innovative joining techniques, developments in medical and biotech- as channel structures with a width of nological microsystems, the joining 50 µm have to be sealed. The heat technique is having to meet higher influence zone produced by conven- requirements with regard to miniaturi- tional contour welding is too big and zation. By combining a fiber laser and the channels can be blocked by melt, an innovative, highly dynamic irradiation preventing the component from per- strategy a new technique - Transmission forming its function. The TWIST tech- Welding by an Incremental Scanning nique can also be used for welding thin Technique (TWIST) was developed for plastic films (100-µm polypropylene). this purpose. With such advantages, the new technique expands the applications of plastics welding by laser, while providing greater process flexi-bility and higher Method precision in the micro to macro range.

The new approach incorporated in TWIST combines the incremental method of contour welding with the high Contacts dynamics and associated effects of quasi-simultaneous welding. Such Dipl.-Ing. A. Boglea, Tel.: -217 complex, precise and rapid movements [email protected] of the laser beam can only be realized Dr. A. Gillner, Tel.: -148 with the components of high-speed [email protected] scanning technology such as galvano- Above: Various irradiation strategies meters, polygon scanners and reso- for the TWIST technique. nance scanners. There are several ways Below: Seal welding of membranes of producing such welds. The various with variable seam widths. movement elements such as circles, sinusoidal movements and Bernoulli lemniscates can be combined to create seam geometries of complex shape. If the laser beam is moved at a very high path speed of up to 4 m/s in such an element and this element is moved at the same time along the desired seam contour at the desired feed speed, high-quality welds with joint geometries < 100 µm can be produced.

88 Fraunhofer ILT Annual Report 2007 Laser-assisted joining of plastics with metal and ceramic components

and good temperature stability which Task are at the same time light in weight and amenable to variable shaping. If Plastic is becoming increasingly im- plastics with different melting points portant as a construction material for are used, it is possible to join two plas- numerous products in the technical en- tics with each other, or to bond plastic vironment, and in this context plastic with wood. components frequently have to be connected with other components made of metal or ceramics. Results and Applications

Fundamentally, the technique can be Method deployed wherever it is useful to combine the properties of plastic and metal With a newly developed laser-based or ceramics. For example, it can be joining technique, high-strength con- used on spectacles to form a better nections can be very rapidly produced bond between the frame and the plas- between plastics and other materials. tic lenses, producing a stronger joint which is less liable to loosen and also The LIFTEC technique (patent pending) opening up new scope for design crea- is based on the fact that all thermo- tivity. The same approach can be ap- plastic polymers are transparent or at plied for joining PVC windows or wall least translucent in the unpigmented panels to metal frames to form a stable, state. At the beginning of the process impermeable unit. the non-plastic component or a part of it is heated by laser radiation which passes through the plastic joining partner. Under mechanical pressure the Contacts component is pressed onto the plastic part. As this happens the plastic is hea- Dipl.-Ing. J. Holtkamp, Tel.: -273 ted by thermal conduction to a tempe- [email protected] rature above its melting point and the Dr. A. Gillner, Tel.: -148 component or part of it penetrates into [email protected] the plastic. Given the selection of a suitable component geometry, a solid, positive bond is formed after cooling. Above: Metal screw thread Compared with other heating con- in plastic. cepts already in use, heating by means Below: Plastic-ceramic of laser radiation takes place more or composite. less independently of the thermal and electrical conductivity of the material being pressed into the plastic. This means that, in addition to metals, other materials including ceramics can be bonded with plastics. In the process, the properties of both materials can be combined to create hybrid components of high mechanical strength (hardness), wear resistance

Fraunhofer ILT Annual Report 2007 89 Cutting adhesive seals for microtiter plates

well and so a CO2 laser with a wave- Task length of 10.6 µm is used for this task. During preliminary tests the parameters For a special application in bioprocess feed speed v, laser power P, nozzle engineering, commercially available pressure and distance, which are im- 96-well microtiter plates are modified portant for cutting, were initially deter- in such a way that in each case two mined so as to cause mini-mal damage adjacent cavities are connected with a to the adhesive layer. In the next step, small channel in the cover. The cavities a contour-adapted film support was and channels are sealed by means of built with which average quantities an adhesive film which for this purpose of approx. 100 units at a time can be has to be provided with 8 x 12 = 96 reproducibly cut. circular recesses.

Results and Applications Method

With an x-y axis system, a CO2 laser The adhesive film with a material thick- and a cutting head containing a lens ness of 0.25 mm is placed on a plastic with a focal length of f = 63.5 mm, carrier film with a thickness of 0.15 mm the combination of adhesive film and and has to be cut in this combination. carrier film was cut without any smoke After cutting, the carrier film is removed residue at v = 80 mm/s and P = 25 W. and the adhesive film is applied to the The film support is highly suitable for microtiter plate. Plastics absorb radia- reproducibly cutting smallish quanti- tion in the infrared spectral range very ties. For an intended reduction of the Laser-cut combination of cycle time it will be necessary to auto- adhesive film and carrier film, thickness 0.4 mm, hole diameter mate the present manual system. 6.5 mm, perforated grid for 8 x 12 microtiter plate.

Contacts

Dipl.-Phys. G. Otto, Tel.: -165 [email protected] Dr. A. Gillner, Tel.: -148 [email protected]

90 Fraunhofer ILT Annual Report 2007 Fine cutting

Task Results and Applications

The effect of the ultrasonic flow and The results show that the effect of the its interaction with the fast flowing stagnation point flow on the nozzle metal vapor are particularly important flow is an important phenomenon in for the quality of fine cutting. Our fine cutting. The driving forces (pres- understanding of the connection bet- sure gradient, shear stress) along the ween cutting parameters and quality cutting edge exhibit strong depen- features, the potential for improve- dence on the nozzle parameters (top ment and the limits of the process figure), from which the process do- were analyzed. mains are identified with qualitatively differing solution behavior. The individual process domains are differentiated by means of the dominant ap- Method pearance of different physical phenomena: effect of the gas flow into the The flow of a cutting gas in conical, gas nozzle, inflow of metal vapor into conical-cylindrical and Laval nozzles is the gas nozzle (bottom figure), detach- calculated. A study of the eight nozzle ment of the gas flow from the top parameters shows their connection edge of the cut, acceleration of the with three result parameters which melt in the opposite direction to the are important for cutting: mass flow gas flow and detachment of melt in the cutting joint, gas pressure and drops on the top edge of the cut. gas speed along the cutting front. The coupling of the gas flow with the The determination of a suitable nozzle movement of the melt front, melt and type and the nozzle parameters is indi- vapor are then examined. cated and the sensitivity of the parameters to the solution is shown.

Above: The Mach number The work presented was funded by of a cylindrical-conical nozzle. the German Research Foundation DFG Below: The pressure from under reference number SCHU1506/1-1 evaporation and flow of gas and is being continued in the Excellence and vapor. Cluster »Integrative Production Tech- nology for High-Wage Countries«.

Contacts

U. Jansen, Tel.: -163 [email protected] Prof. Dr. W. Schulz, Tel.: -204 [email protected]

Fraunhofer ILT Annual Report 2007 91 Fine cutting of silicon

Task Results and Applications

Crack-free cutting of silicon is an The mechanical loads caused by the example of the work involved in cutt- gas flow, evaporation (top figure) and ing very thin but relatively wide com- the thermomechanical effect (bottom ponents made of brittle-hard materials. figure) as variables distributed in time To improve the breaking strength of and space are stated as the result. Si wafers, the edge zone, which is degraded by cracks, is expensively The thermomechanical load cycle removed in an acid bath. causes crack formation with a characteristic spatial structure (bottom A better understanding of what hap- figure). The dynamic stress condition pens when brittle-hard materials are in the material produces crack pro- cut is intended to indicate unexploited pagation vertically to the cutting edge potential and the limits of fine cutting. which is deflected by the stress field in azimuthal direction. The change in the direction of propagation takes place at a distance reflecting the magnitude Method of the thermal penetration depth. The thermal energy deposited in the ma- Above: Distribution of The flow of the cutting gas and in par- terial and the penetration depth of the the pressure caused by ticular its mechanical effect on the thin heat are closely connected with the an ultrasonic flow of gas. Below: Crack formation, wafer are examined as a function of appearance and length of the crack. temperature (black), the nozzle parameters. In addition to radial stress (blue), the gas flow, the material is mechani- The work presented was funded by the azimuthal stress (red). cally loaded when the recoil pressure German Research Foundation DFG under of the evaporating material acquires reference number SCHU1506/1-1. high values at the beginning of the pulse. The heating effect of cutting produces radial and azimuthal stresses in the environment of the cutting front Contacts which are compared with the breaking stress. Dr. M. Niessen, Tel.: -307 [email protected] To calculate the ultrasonic flow of the Prof. Dr. W. Schulz, Tel.: -204 cutting gas, the existing simulation of [email protected] the friction-free Euler equations is expanded by including the interaction with the evaporating silicon.

92 Fraunhofer ILT Annual Report 2007 Precision-drilling of shaped holes in steel

for spiral drilling, the laser radiation Task rotates on itself additionally to the rotational movement in relation to the There is high demand in industry for workpiece. Through this additional precision-drilled holes of defined shape rotation spirally drilled holes can be in the diameter range of less than made down to a diameter range which 100 µm with a high aspect ratio. These matches percussion drilling. include, for example, drill holes for Entrance 65 - 70 µm nozzles (injection nozzles, spinning nozzles) and air-cushioned bearings, as well as lubrication and ventilation Results and Applications drill holes. In particular, shaped holes with a positive taper ratio, i.e. with a By means of spiral drilling in which the larger hole exit than entry, are required. radiation rotates on itself, shaped holes Such holes cannot be produced by can be produced with a taper ratio conventional laser drilling methods from the entry diameter to the exit 65 µm 85 µm 120 µm 160 µm 200 µm such as percussion drilling, and the diameter of 1:3 for 1 mm component Exit necessary small diameters cannot be thickness to 1:4 for 2 mm thickness. achieved by trepanning. Another pro- The roughness of the hole wall is in blem is that the precision with regard the range Ra < 1 µm. By changing the to the roughness of the drill hole wall setting angle of the laser radiation and is not high enough. The stated require- the hole diameter during the drilling ments are, however, fulfilled by the process, countersunk holes or holes most recent of the laser beam drilling with defined tapering can be produced. techniques - spiral drilling.

Contacts Method Dipl.-Ing. W. Wawers, Tel.: -311 In spiral drilling the rotating laser [email protected] radiation removes the material by means Dr. A. Gillner, Tel.: -148 of numerous short high-energy laser [email protected] pulses, while the laser radiation moves into the depth of the material. The continuous rotational movement along the wall of the drill hole produces a smooth, homogeneous surface. The different taper ratios are achieved by varying the setting angle of the laser radiation on the workpiece. The laser Above: Examples of various taper ratios. radiation then rotates along the lateral X5 CrNi 18 - 10, d = 1 mm. surface of a cone, whose opening angle Below: SEM image of the is proportional to the taper angle of wall of a spirally drilled hole in X5 CrNi 18 - 10. the drill hole. A variant of the spiral drilling method makes it possible to produce small holes. In an optical system developed at the Fraunhofer ILT

Fraunhofer ILT Annual Report 2007 93 In-situ determination of drilling depth during percussion drilling

tential overexposure due to optical Task emissions (melt, plasma etc.) produced by laser radiation. To evaluate the re- The hole geometries obtained by laser sults, the resolution (µm/pixel) of the drilling, including factors such as the photograph is determined, and the hole depth, are currently analyzed by length of the deformation is measured means of destructive testing methods based on the number of pixels in the such as the longitudinal grinding of photo. drill holes followed by a microscopic examination. In order to replace these destructive methods and reduce the time and cost involved, a new tech- Results and Applications nique is being applied which enables the hole depth to be determined in- Destructive testing methods are being situ during the percussion drilling. replaced by in-situ determination of the hole depth during the percussion drilling. The depth of laser drill holes is being measured with a temporal reso- Method lution of 50 ms. The spatial resolution is 29 µm/pixel and is dependent on the The hole is drilled at a defined distance magnification of the camera lens and (approx. 100 µm) from the polished side the size and pixel number of the camera wall of the stainless steel workpiece. sensor. As the material heats up during impact of the laser pulses and cools down in The determined drill hole depths are the interval between two consecutive used to investigate the maximum pulses, plastic deformations are induced depths that can be achieved using in the workpiece’s side wall. These de- different parameters (lower figures). formations are photographed from the side with a high-speed camera (Motion Xtra HG-100K by Redlake), which is synchronized with the laser beam source Contacts (upper figure). The photographs are taken between pulses to avoid po- Dipl.-Ing. J. Dietrich, Tel.: -479 [email protected] Dr. I. Kelbassa, Tel.: -356 [email protected]

Above: Photographs of the surface deformations produced during percussion drilling. Below: Measured drill hole depths versus laser pulses as achieved using the process gases oxygen, argon and helium without changing the process parameters.

94 Fraunhofer ILT Annual Report 2007 High-precision nozzle drill holes in Inconel® 690 nickel-based super alloys

Suitable process windows are deter- Task mined for each of the two steps by systematically varying such parameters as: In nuclear power plants, precision • Focus position during trepanning nozzle drill holes with a diameter of • Feed rate 350 µm and a depth of 2 mm are re- • Number of passes quired. Due to the immense thermomechanical stresses encountered in The drilling results are analyzed and this environment, components are evaluated in terms of their geometrical 500 µm made of the nickel-based super alloy and metallurgical features on the basis Inconel® 690. This austenitic alloy has of longitudinal sections. very high strain-hardening properties, is very tough, and has low heat conductivity. This causes major stress and wear in tools during machining proces- Results and Applications ses, particularly mechanical drilling. By trepanning with laser radiation, drill • Drill holes with a diameter of 350 holes with the required precision of µm can be produced in 2-mm-thick ± 25 µm can be produced with little Inconel® 690 with a standard devia- effort compared to alternative proces- tion of 6 µm. ses such as electro-discharge machin- • The diameter tolerance of ± 25 µm ing (EDM) or electro-chemical machin- specified by the customer is achieved ing (ECM). for all drill holes. • The diameters of the drill holes are determined by means of a 100-percent final inspection by transmitted Method light microscopy, and are measured and recorded with the help of Trepanning involves two process steps: image processing software. 1. A through-hole is pierced by percussion drilling (several pulses on Above: Cross-section of a ® the same area of the workpiece). drill hole in Inconel 690. Below: Bar chart showing 2. The hole is then given its final dia- Contacts the evaluation of 93 drill hole meter by trepanning (laser cutting). diameters. Dipl.-Ing. K. Walther, Tel.: -409 [email protected] Dr. I. Kelbassa, Tel.: -356 [email protected]

Fraunhofer ILT Annual Report 2007 95 Influence of process gas on percussion drilling

Significant differences are observed Task between the effects of the two process gases argon and oxygen at a total Drilling by laser radiation can be done pressure of 5 bar. In the case of argon, using various different techniques, the drilling channels are interspersed such as single-pulse or percussion drill- with inclusions, while in the case of ing or trepanning. In order to achieve oxygen, the drill holes only have inclu- a specified drill hole geometry, it is sions at the base of the drilling chan- necessary to know exactly which pro- nel. When using oxygen, the melt that cess parameters to select (intensity still fills nearly the entire drilling chan- distribution of the laser light, focus nel after the first pulse is driven out as position, process gas) and what the the number of pulses increases. Drill properties of the material are. The type holes made using the process gas ar- and pressure of the process gas em- gon feature an irregular distribution of ployed play an important role in terms inclusions and have no clear tendency of productivity (drilling speed) and with in terms of the hole depth. regard to the quality of the drill hole (geometry and reproducibility).

Results and Applications

Method The tests show that the process gas parameters have a strong influence on In a series of tests, percussion drill the drilling result. This means that, in holes are produced with an increasing addition to the laser parameters, it is 1 2 3 5 10 20 number of pulses using different pro- also important to set the process gas cess gas settings (type and pressure). suitably for each application and each The holes are metallographically pre- set of drill hole specifications (e.g. pro- pared and metallurgically analyzed by cess duration, diameter tolerance or means of longitudinal sections. The permissible thickness of the oxide layer). penetration depths (maximum depth By dynamically regulating the pressure to which material has been melted) in line with the hole depth, it is poss- and the free hole depths (depth down ible to pierce a through-hole more to the first closure of the drill hole) are quickly and with smaller fluctuations in determined. The two figures show the the process duration. resulting penetration depths (lower dotted line) and the free hole depths (upper line) in progression for each number of pulses. Contacts

Dipl.-Ing. K. Walther, Tel.: -409 [email protected] Dr. I. Kelbassa, Tel.: -356 1 2 3 5 10 20 [email protected]

Above: Argon 5 bar, as a function of the pulse number. Below: Oxygen 5 bar, as a function of the pulse number.

96 Fraunhofer ILT Annual Report 2007 Plasma diagnosis during laser drilling

setup, the intensity and broadening Task of spectral lines is measured by spectroscopy, and from that, it is possible Diagnosis during laser drilling generally to determine electron densities and includes the lateral observation of gas temperatures in the plasma. These and plasma dynamics above the drill factors can be used to calculate the hole, the coaxial observation of optical space- and time-resolved absorption radiation emitted from the drill hole coefficient in the plasma, and the plas- (in-situ) or a metallurgical analysis by ma frequency in the drill hole. From means of light or electron microscopy. the results, it is then possible to derive Due to the limited optical accessibility information on optical properties of of the drill hole, only the processes the plasma (absorption and refraction), taking place near the surface can be which can be used to adapt the subse- observed (expansion of plasma in the quent pulses in order to optimize the half-space), which provides insufficient quality (e.g. thickness of the melt film) information about the vapor and plas- and productivity (e.g. drilling speed) of ma dynamics. Alternative approaches, the drilling process. such as drilling in transparent material to enable optical observation of the process, provide only a limited indica- tion of what the process would look Results and Applications like in metal, due to the differing physical properties of the materials. • Time- and space-resolved diagnosis Non-destructive techniques, such as of the optical emissions of spatially imaging the drill holes with X-rays, are confined plasma in the drill hole not suitable for resolving the process • Spatial resolution 1 µm, temporal Above: Temporal expansion ≥ of the plasma inside prepared dynamics due to the small temporal resolution ≥ 1 ns blind drill holes, including the and spatial resolution achieved. • Expansion and expansion rate times at which the images were of plasma and shock front taken relative to the start of the pulse in ns. • Electron and ion temperatures and Below: Test setup. densities inside drill holes Method

Blind drill holes are prepared in metal foils of various thicknesses (30 -100 Contacts µm) by making cuts in the foils. The width of the cut gaps corresponds to Dipl.-Phys. M. Brajdic, Tel.: -205 the diameter of the drill holes. Opti- [email protected] cally transparent materials are placed Dr. I. Kelbassa, Tel.: -356 on either side of the metal foils as win- [email protected] dows. The drilling process is continued at the prepared drill holes, and is observed laterally through the windows by means of high-speed photography (lower figure). The dynamics of the plasma, or the shock front, are then determined in temporal and 2-D spatial resolution (upper figure). The measurements include the spread and the expansion rate of the plasma and the shock front. Using a comparable test

Fraunhofer ILT Annual Report 2007 97 Drilling with efficient melt expulsion

Task Results and Applications

A spatially resolved drilling model The formation of a drill hole by expul- which is able to describe the time-de- sion of a molten phase is performed pendent formation of the drill hole is a by accelerating the melt arising at the key element in understanding the phy- base of the drill hole and decelerating sical mechanisms at work when drilling the melt along the wall of the hole. using laser radiation. As far as the user The formation of recast on the wall of is concerned, the main issue is to find the hole results from the flow equili- ways of avoiding the formation of brium, which depends on the heating recast on the wall of the drill hole. of the melt surface, the transport of heat in the flowing melt and cooling in the surrounding material. The results of an initial model task for the spatially Method resolved drilling model can be seen in the figure. The hole bottom face, the The predecessor model describes the temperature in the solid and in the drilling process with a spatially inte- melt, the flow speed of the melt, the grated representation of the hole bot- melt film thickness and the recast tom face. The physical phenomena of thickness on the wall of the hole are heat conduction, flow of the melt and parts of the time-dependent solution. evaporation are taken into account. The model is expanded with the in- By taking the local events at the hole clusion of spatial resolution at the hole bottom face into account it is possible bottom face. The geometrical shape of for the first time to simulate and ana- the evolving drill hole is calculated and lyze in detail the model for the forma- is part of the solution. By analyzing the tion of the drill hole as well as for drilling model for the process variant structuring and material removal. of percussion drilling, the cooling of the outflowing melt is examined dur- The work presented was funded by ing drilling. the German Research Foundation DFG in the Excellence Cluster »Integrative Simulation of the spatially resolved Production Technology for High-Wage model. Countries«.

Contacts

Dipl.-Phys. U. Eppelt, Tel.: -163 [email protected] Prof. W. Schulz, Tel.: -204 [email protected]

98 Fraunhofer ILT Annual Report 2007 Micro-perforation of balloon catheters

Task Results and Applications

The systemic delivery of drugs to treat Excimer lasers enable holes to be drilled local vascular diseases has the disad- into the balloon casing without any vantage that large volumes of the active visible degradation. The risk of particles ingredient have to be introduced into being released during insertion is low, the bloodstream. Under these condi- as any particles present in the area are tions, it is impossible to accurately dose carried away by the rinsing fluid. the concentration of the drug at the target site. The dose could be regulated At diameters of 20 µm and above, more efficiently if the drug seeped the liquid flows through the holes at a out through small pores in a balloon steady rate with an upstream pressure catheter placed directly adjacent to of 5 bar. Holes with a diameter of the vessel wall. 30 µm typically result in a flow rate of 30 µl/min. In this case, the upstream pressure can be varied between 1.5 and 6 bar to control the flow. The drug Method can be dosed by adjusting the number and size of the pores. Balloon catheters are used in medical applications where vessels need to be This project was carried out in coope- widened or probes need to be tempo- ration with PD Dr. G. A. Krombach rarily fixed in place. The balloon casing of the Department of Diagnostic Ra- is initially wrapped tightly around a diology at RWTH Aachen University guiding catheter during insertion, and Hospital. is then expanded at the target site by filling it with a physiological saline solution. The drug, together with the saline solution, can then seep out Contacts Above: Balloon catheter through small openings drilled into the with a partially inflated balloon catheter’s balloon casing with an ArF Dr. M. Wehner, Tel.: -202 at its tip. excimer laser. The appropriate size [email protected] Below: Array of 50-µm holes and number of holes is determined Dr. A. Gillner, Tel.: -148 in the balloon casing. through preliminary tests in a water [email protected] bath.

Fraunhofer ILT Annual Report 2007 99 Diagnosis of ultra-fast, laser-induced melt dynamics of metals

Task Results and Applications

The physical processes and process The dynamics of the laser-induced melt limits involved in materials processing formation and material ablation ob- with ultra-short pulsed laser radiation served in aluminum can be divided into

(pulse duration tp < 1 ps) have not yet several characteristic time regimes. As been sufficiently examined. The known a function of the process parameters, advantages of femtosecond lasers, expulsion of the heated evaporated such as melt-free ablation and a low material (τ < 200 ns), explosive melt- thermal load on the material, are often free ablation (200 ns < τ < 700 ns) and restricted to small fluences. The use of the formation of melt films (τ > 700 ns) high-energy (F > 10 Jcm-2), ultra-short are observed. Assuming rotational pulsed laser radiation produces ther- symmetry, the volumes of the ablated mal and non-thermal melt formation material particles are measured in and significantly influences the ma- temporal resolution. The dynamics of terials processing results. the ejected material featured qualitative and quantitative differences de- The aim of these tests is to visualize pending on the number of pulses the dynamics of plasma, material va- used. At τ > 700 ns, for example, melt por, melt formation and melt solidifica- formation increases with increasing tion in metals and to define process pulse energy and number, whereas the limits. formation of material vapor diminishes.

The experience gained by this temporally resolved diagnosis can be used Method to control microstructuring processes carried out with ultra-short pulsed 5 µm A novel optical pump&probe measur- laser radiation, and to model laser- ing technique for temporally and spa- induced phase transitions. Above: Melt expulsion in Al (τ = 1.67 µs), left: shadow image, tially resolved visualization and analysis right: calculated phase image. of ultra-fast phenomena is used. This Below: Surface modification with involves Transient Quantitative Phase melt deposits after 8 laser pulses. microscopy (TQPm) for determining Contacts the quantitative optical phase, changes in the transient indexes of refraction, Dipl.-Phys. I. Mingareev, Tel.: -535 and melt volumes, at a temporal reso- [email protected] lution of 100 fs and a spatial resolution Dr. I. Kelbassa, Tel.: -356 of 1 µm. The melt dynamics of metals [email protected] are examined at up to τ = 2 µs after irradiation with n = 1 to 8 laser pulses.

100 Fraunhofer ILT Annual Report 2007 Improved solid-state laser microablation processes with tailored pulse trains

The plasmas generated during micro- Task ablation are detected using space- and time-resolved measurements. The diag- The aim is to improve the efficiency of nosis of characteristic plasma dynamics laser beam microablation by increasing (temperature and density of electrons, the ablation rate, while at the same expansion of the plasma) is to help in time keeping surface roughness suffi- developing an online monitoring sys- ciently low by reducing the portion tem that measures the current ablation of liquid material during the process. efficiency of the laser pulse.

A model-based analysis of the dynamics of the melt during the ablation Method process, the behavior of the plasma after the laser pulse hits the sample, By using tailored, time-modulated laser and the spectral emission of the plas- pulse trains, the project goal is to ma- ma are carried out as a function of time. ximize material ablation and improve The detected spectra can be simulated the diagnosability of the plasma dyna- using a model for calculating spectral mics without increasing laser energy. plasma emissions, which incorporates One approach involves dividing the material properties as well as spatially energy of a discrete laser pulse into resolved and spatially integrated plas- pulse bursts with interpulse separa- ma dynamics (electron temperature tions in the nanosecond or micro- and density, plasma expansion) and second range. Laser-induced break- their temporal characteristics (see down spectroscopy is used to investi- middle figure). The absorption of gate the induced plasma signal for radiation energy and thus also the possible correlation with the volume of transport of radiation to the workpiece material removed. By analyzing and is described on the basis of a fluid modeling the plasma dynamics, control dynamic simulation of the plasma and rules are to be derived which aim at vapor (see lower figure). maximizing the ablation rate.

Contacts Results and Applications Dipl.-Phys. C. Gehlen, Tel.: -127 During laser microstructuring with pico- [email protected] second multipulses, the processing re- Dipl.-Ing. (FH) C. Hartmann, Tel.: -207 sult can be widely varied by altering [email protected] Above: Ablation with pico- the burst parameters. The use of pico- Dipl.-Phys. U. Eppelt, Tel.: -163 second triple pulses. second dual or triple pulses improves [email protected] Middle: Comparison between the ablation rate by up to 90 percent a spectrum produced by means for each layer. This can be achieved ex- of a plasma model and the detected spectrum of a C75 clusively by temporal variation of the sample. intensity without changing the overall Below: Results of the plasma energy input. By carefully selecting simulation. the process parameters, an ablation volume of 1 µm per layer with a surface roughness of Ra ≤ 0.6 µm can be achieved using picosecond triple pulses (see upper figure).

Fraunhofer ILT Annual Report 2007 101 Synthetic microhairs for sensory applications

Task Results and Applications

Tiny hairs acting as flow sensors are Following initial studies on the ablation often found in the natural environ- behavior of wax and a comprehensive ment. Spiders, for example, have small parameter study on the drilling of cast- hairs in their joints that provide infor- ing molds, the first microhair arrays are mation on their angular position. Fish now available and have already been have what is known as a ‘sideline sys- tested in combination with piezoelectric tem’, which helps them to map their sensor elements. The signal sequence fluidic environment. To transfer these generated by pressure on the micro- principles to manmade systems, it is hairs is clearly recognizable and can necessary to produce synthetic micro- be matched to the different microhair hairs of different geometries with lengths. The hairs produce much diameters of 20 to 200 µm and lengths weaker signals when they are bent of up to 1 mm. than when they are impressed, the ratio being approx. 1:10. It is therefore possible to match individual signals to the corresponding microhairs and Above: Signal sequence under normal loading conditions Method given loading conditions (shearing, (Source: IMFD Freiberg). folding, bending) on the basis of their Below: Array of microhairs. Microhairs with diameters in the micro- sequence and strength. meter range are produced using a ‘lost mold’ (lost wax or investment casting) In addition, such microhairs can be technique. The advantage of this tech- used to measure flow mechanics even nique is that it enables force-free de- without an added sensor element. This molding of the filigree structures by involves analyzing the deflection of simply melting the surrounding matrix. microhairs in the shear field of the Microhairs produced in this way can be flow near the wall. The simulation of made to have virtually any dimensions biological structures, such as the sen- and geometries. Combined with pie- sory hair cells in the inner ear, can zoelectric elements, they can be used help in analyzing the flow-mechanical to develop sensors for medical applica- events taking place during the hearing tions. By grading the lengths of the mi- process. crohairs on such a sensor element and passing it through a stenosis, for Cooperation partners: Prof. C. Brücker, example, it is possible to draw accurate Institute of Mechanics and Fluid Dyna- conclusions as to the geometry of the mics, Freiberg University of Mining and stenosis. To this end, the signals of the Technology. piezoelectric element must be analyzed with regard to both their strength and temporal sequence. Contacts

Dipl.-Chem. P. Jacobs, Tel.: -135 [email protected] Dr. A. Gillner, Tel.: -148 [email protected]

102 Fraunhofer ILT Annual Report 2007 Creating periodic nanostructures by three-beam interference

Task Results and Applications

Nanostructures offer great potential The developed structuring system was for imparting new functions to surfaces. used to produce nanostructures in thin As an example, nanostructuring can polymer films by photochemical ablation. produce superhydrophobic properties By varying the angle of exposure, it on polymers and other materials. is possible to produce structures of Furthermore, nanostructures can be 200 nm, for example, with a period used to generate optical effects and of approximately 1 µm (see figure). functions. By stringing together nano- Smaller structures under 100 nm can structures of differing periodicities, also be created by altering the irradia- for example, it is possible to form an tion conditions. The resulting stripe individual color code that can be used patterns serve to analyze cell growth to distinctly label products. The color properties on synthetic surfaces. Even code is only visible when illuminated very complex patterns can be created from a specific direction. with this system by rotating the component and by dual and multiple structuring. In this way, the wettability Periodic nanostructures of a surface can be selectively altered in photoresist, period 1 µm, Method in certain places to give it superhydro- feature width 250 nm. phobic properties (lotus effect). In order to produce nanostructures in the 100-nm range, a three-beam interference system was set up which merges three coherent beamlets to Contacts create periodic structures. The period of these structures depends on the Dipl.-Phys. S. Beckemper, Tel.: -325 wavelength of the laser and the set [email protected] merging angle. The intensity profile Dr. A. Gillner, Tel.: -148 created by superposition of these three [email protected] beamlets enables a higher contrast to be achieved than with a classic two-beam interference system. A frequency-tripled Nd:YAG laser with λ = 355 nm and a sufficient coherence length was used as the beam source.

Fraunhofer ILT Annual Report 2007 103 3-dimensional micro- and nanostructures inside sapphire produced by selective, laser-induced etching

more than one millimeter. Periodic Method nanostructures (nano planes) can be formed in the irradiated area as a By focusing femtosecond laser light in- function of the focusing parameters side the volume of transparent dielec- and the average laser power. The nano trics (sapphire, glass), it is possible to planes are always oriented perpendi- achieve local changes in microstructure cularly to the polarization of the laser and thus also in etchability. This makes radiation. Their orientation is not influ- it possible to produce 3-dimensional enced by changes in the traversing di-

modified channel micro- and nanostructures by sub- rection. By selectively etching the nano sequent etching with hydrofluoric acid. planes, it is possible to produce nanos- copic cavities measuring approximately 100 nm x 10 µm x 1 mm at writing speeds of 1 mm/s. Potential areas of Results and Applications use include microfluidic systems for

etched microchannel biological and chemical applications, It is possible in sapphire to achieve and photonic crystals for integrated differences in etchability of up to optical elements. 10.000:1 between modified and un- modified areas. This enables the manufacture of µ-channels with diameters between 1 and 10 µm at lengths of Contacts 1 µm Dipl.-Phys. D. Wortmann, Tel.: -276 [email protected] Dipl.-Ing. (FH) H. Horn-Solle, Tel.: -475 Above: Transmitted light micros- [email protected] cope image of a partially etched Dr. J. Gottmann, Tel.: -406 2 µm µ-channel. [email protected] Middle: SEM images of cross- sections of the etched areas to a depth of 500 µm; above: nano cavities, below: microchannel. Below: Schematic outline of the laser-induced volume modification.

Scan direction

104 Fraunhofer ILT Annual Report 2007 Changing the refractive index of glass materials using a double-pulse femtosecond laser

The results obtained in this project Method are among the world’s highest values achieved so far for silica glass, and By focusing femtosecond laser radia- open up the prospect of producing tion inside the volume of glass ma- waveguides with numerical apertures terials, their refractive index can be of the same magnitude as those of locally increased. The use of double diode lasers. The results can be ex- pulses with time intervals in the sub- plained by the active influence of the nanosecond range produces a signifi- second pulse on the relaxation chan- cantly greater change in the refractive nels of intermediate electronic states, index than the use of single pulses. and the microstructural changes resulting from this. Areas of application include wave-guiding or beam-shaping elements of integrated optics, such Results and Applications as beam splitters, coupling structures for diode lasers or waveguide lasers. When pure silica glass is irradiated using fs double pulses with time intervals of between 400 and 800 ps, it is possible to increase changes in the Contacts Above: Changes in the refractive index versus the timing interval refractive index by a factor of 1.5 to 2 of the double pulses, at a fixed compared to the use of single pulses Dipl.-Phys. D. Wortmann, Tel.: -276 pulse-energy ratio of 50 %. with the same total energy. This in- [email protected] Below: Photograph of the far- creased difference in the refractive in- Dr. J. Gottmann, Tel.: -406 field distribution of a waveguide fabricated in silica glass using fs dex between modified and untreated [email protected] double pulses. material results in an increase by the same factor in the numerical aperture of the waveguide fabricated using this process.

Fraunhofer ILT Annual Report 2007 105 Laser-induced forward transfer of proteins, cells and active agents

Task Results and Applications

To improve the acceptance of surgical Protein arrays can be produced at the implants by the body, a surface has high speed of approx. 1,000 spots per to be created on them which matches second. With the present setup, the the biological surroundings as closely spot sizes can be varied from 20 µm as possible. This biofunctionalization to 200 µm. Lines and tracks of proteins requires a technique with which sam- can also be written. In a next step the ples of proteins, cells or active agents intention is to produce complex samples can be selectively deposited on surfaces. of various proteins in order to study In this way, the aim is to produce sys- the reaction of cells to them. It has Target support layer tems modeled on nature which, for also been shown that cells and cell example, facilitate the ingrowth of networks can be transferred. Given artificial implants in the body or make suitable selection of the laser parame- it possible to conduct chip-based in ters, no loss of vitality was observed. Substrate vitro testing. The cells adhere to the substrate surface and proliferate, which means that constructs of different cell types can be developed and cultivated. In a further Method step nanoparticles can be transferred by LIFT to precisely targeted locations For this task, a process and machine on surfaces which are charged with technology for the selected transfer active agents, thus making it possible of biologically active substances is to create innovative bioactive coatings developed which can be integrated in on different moldings. existing systems, e.g. for protein spott- ing. The aim is to create products with This project is being funded under the new properties, in particular in bioana- InnoNet program (16-IN 0490) and lysis, medical engineering and regene- conducted in cooperation with the Above: Schematic of the LIFT process. rative medicine. The basis for the inno- companies Arthro Kinetics, Aurentum, Below: Protein array with vative process is provided by a laser- BioCat, Boston Scientific TZ, CryLaS, spot sizes of 60 µm (fluorescence based transfer system known as LIFT GeSim and the Institute for Interfacial image) produced using LIFT. (Laser Induced Forward Transfer). In Engineering of Stuttgart University. this process, a substance located on a film as a transfer medium is transported by laser ablation onto a substrate. Transfer takes place via a laser-active Contacts absorber layer carrying the proteins or cells which evaporates under laser Dr. E. Bremus-Köbberling, Tel.: -396 irradiation. The resultant pressure wave [email protected] transports the proteins and cells over Dr. A. Gillner, Tel.: -148 short distances to the substrate. [email protected]

106 Fraunhofer ILT Annual Report 2007 Laser Plan and System Technology Business Area Laser Plant and System Technology

This business area focuses on the development of prototype equipment for laser and plasma-technology applications, as well as on laser systems engineering, particularly in the fields of automation and quality assurance. Areas of application embrace welding, cutting, hardening, repair coating, drilling and micro-joining. The system technology offered provides complete solutions for process monitoring, components and control systems for precision machining, laser-specific CAD/CAM technology modules, as well as software for measurement, open- and closed-loop control and testing. For its work in process monitoring in particular the business area can draw on extensive and, where required, patent- protected know-how. In this sector numerous systems have already been licensed for companies. Target markets Development of cladding heads include laser equipment and compo- for laser cladding. nent manufacture as well as all sectors of production industry which deploy lasers in their manufacturing activity or intend to do so.

108 Fraunhofer ILT Annual Report 2007 Contents

Development of a multifunctional production cell with integrated combi-head 110

Development of a boroscopically guided processing optic for Laser Metal Deposition 111

Welding of shock absorber valves: development, qualification and knowledge transfer 112

In-situ measurement of laser systems 113

Robust autonomous joint tracking for quality assurance in laser welding 114

Strategies for process monitoring in plastics welding using laser radiation 115

False friends 116

Analysis and application of methods and algorithms to ensure constant product quality 117

Computational steering system for parallelized simulation calculations 118

Fraunhofer ILT Annual Report 2007 109 Development of a multifunctional production cell with integrated combi-head

the head serves the purpose of distance Task control. The ability to rapidly change the focusing optics and a protective Combined processing, in which the glass cover increase operating conve- process change between laser cutting nience. and welding can be made rapidly without having to retool, facilitates very flexible and highly productive use of laser systems. The benefits are especially Results and Applications strong if the entire system including handling and clamping equipment is Components of the head such as the optimally matched to the efficient pro- capacitive distance control and the cess chain and the high accuracy of nozzle assembly have already been combined processing. This applies, in successfully tested. The head will be particular, to high-speed applications integrated in the beam guidance of on highly dynamic systems and to 3-D the portal system in January 2008. This applications. means that, in addition to the combi- head with direct fiber coupling, a co- In systematic parameter variations axial variant is also available for testing with the combi-head, cutting speeds the multifunctional production of of 38 m/min, for example, were de- sheet metal assemblies comprising termined on 1 mm thick steel sheets tailored blanks through to three-dimen- using a fiber with a diameter of 150 µm, sional vehicle components. and 135 m/min with a diameter of 50 µm. At these speeds it is not the The work is being funded by the Ger- process but the machine which is the man Federal Ministry of Economics and

Combi-head with coaxial connection limiting factor for 2-D and much more Technology (BMWi) as well as by the for 5-axis systems and robot with markedly for 3-D applications. companies Reis Robotics, Laserfact and integrated beam guidance (graphic: LBBZ under the InnoNet project »Flexible Laserfact). Production Cell for Combined Laser Processing with Adaptive Gripper Tech- Method nology (koLas)«.

In cooperation with the companies Reis Robotics as the machine manufacturer and Laserfact as the manufacturer of Contacts the combi-head, a combi-head with a connection flange arranged coaxially Dr. F. Schneider, Tel.: -426 to the optical machine axis and with a [email protected] compact additional axis is being deve- Dr. D. Petring, Tel.: -210 loped which can be optimally integrated [email protected] in the mirror beam guidance of a robot portal system. The beam guidance running internally in the robot arm makes it possible to move in three rotary axes without any movement of the fiber. This reduces the strain on the fiber and considerably increases the permissible dynamics during rapid reorientations of the head and high accelerations. The dynamic additional axis integrated in

110 Fraunhofer ILT Annual Report 2007 Development of a boroscopically guided processing optic for Laser Metal Deposition

The processing optic (top figure) is de- Task signed as a modular system comprising a coating head, a collimation and fo- Within a project with Rolls-Royce cusing module, an optical fiber and Deutschland, a boroscopically guided process media transfer unit, and a processing optic for Laser Metal Depo- guide tube support. Along with the sition is being conceived, designed and supply lines for powder and inert gas, manufactured. Its aim is to conduct two water-cooling circuits are integrated. on-wing repairs to aircraft engine The laser radiation is collimated and compressor blades which have been focused, exiting coaxially from the pro- damaged, for instance by Foreign Ob- cessing optic. jects Damage (FOD).

Conventionally, Rolls-Royce Deutsch- land already blends small, usually Results and Applications sharp-edged defects on damaged blades by means of boroscopically Three modules of the processing optic guided milling in the engine, so that are made of copper and then chrome- the notch effect under load (in opera- plated. The module supporting the tion) caused by this defect is distinctly guide tube is made of steel (bottom reduced. figure).

A combination of boroscopic blending A diode laser system with a maximum with an additive manufacturing pro- output power of 1 kW is used as the cess such as LMD is intended to facili- laser beam source. The laser radiation tate the repair of more major defects. is coupled into the processing optic by means of a specially produced optical fiber with a maximum outer diameter of 8 mm. The optical fiber is guided Method by the guide tube, on whose movable Above: Exploded drawing tip the processing optic is assemblied of the processing optic with In the concept phase, the requirements by means of Bowden cables. coating head, collimation and in terms of size - limited by accessibility focusing module, optical fiber and processing conditions -, required After assembly of the optical system and process media transfer unit, optical fibers, support and process media and design aspects are and connection to the guide tube and guide tube (from left to right). determined. The beam path is calculated optical fibers, general functional tests Below: Fully assembled pro- on the basis of the technical specifica- are successfully conducted. Initial cessing optic. tions issued by laser and optical fiber coating tests on flat substrate plates manufacturers, and the optical compo- have been successful. The next step nents are designed accordingly. will be to implement the process on blade-like samples.

Contacts

Dipl.-Ing. (FH) P. Albus, Tel.: -479 [email protected] Dr. I. Kelbassa, Tel.: -356 [email protected]

Fraunhofer ILT Annual Report 2007 111 Welding of shock absorber valves: development, qualification and knowledge transfer

Task Results and Applications

The task is to develop and qualify laser Pre-series testing of the process was welding for shock absorber valves with carried out with a preloading device defined preload forces. The product installed on a laser unit at the Fraun- and the process are to be scaled up hofer ILT. It achieved cycle times of ap- for cost-effective full-scale production. prox. 30 seconds per part and welded The aim is to develop a capable pro- a significant number of shock absorber

cess with an index of cp > 1.33. Later it valves. In the preloading device, the is intended to build a production facility parts were tensioned with defined forces. with a capacity of > 2 million parts per The relative movement between the la- annum. ser beam and the workpiece is achieved by rotating the parts. This induces disruptions which increase the scatter of the damper characteristics and thus Method adversely affect control of the production process. The capability index is The customer is a manufacturer of less than 1 and so the device is being shock absorbers and other products incrementally improved. In addition which it supplies to the auto industry to solving the production-engineering and is seeking to increase the precision task, the success of the project deci- of damper production. To this end sively depends on an effective transfer a laser welding technique has been of the knowledge gained. It is there- developed and laboratory-tested which fore planned to build and operate the makes it possible to precisely adjust production facility initially at the Fraun- the speed-power characteristic of hofer ILT. During its operation at the shock absorbers. The strength index Fraunhofer ILT, employees of the cus-

is cp > 1.33. tomer will be trained and familiarized with laser technology. Only then will the unit be integrated in a production line on the customer’s premises.

Detailed view of a shock absorber valve being welded. Contacts

Dipl.-Ing. M. Dahmen, Tel.: -307 [email protected] Dr. S. Kaierle, Tel.: -212 [email protected]

112 Fraunhofer ILT Annual Report 2007 In-situ measurement of laser systems

from the sequence of images. This Task can then be used to calculate the kinematic variables of acceleration Process input parameters on the work- and feed speed as well as the tool piece can only be checked – if at all – interaction point. sporadically during maintenance work on production units. What’s more, the check is in most cases restricted to measuring the focus position and Results and Applications power of the laser beam. Owing to the principles involved and because no This process enables the true kinematic suitable instruments exist, it is not pos- variables of a laser system to be direct- sible to measure the decisive kinematic ly determined during operation. As characteristics of machining systems, a result it is possible to systematically which means that the positioning ac- identify and remedy problems caused curacy, feed speed and acceleration by deviations from process parameters. cannot be checked during machining. This is particularly true of the scanner In future the technique will be particu- optics which are frequently used in larly useful for avoiding process faults high-brilliance laser systems. In this in the deployment of new, highly focus- case, it is only possible to control the able laser beam sources in the multi- axes of motion by means of positioners kilowatt range. Exploiting the techno- on the scanner mirrors. All this means logical advantages of these systems, that there is only limited scope for con- e. g. to maximize process speed and trolling the path of the beam on the thereby reducing the available process workpiece. window, entails a risk of undesired and unnoticed fluctuations in the process input parameters. Such fluctuations can be reliably identified and avoided Method by using this technique. Above: Measured contour of a laser cutting process with The coaxial process control (CPC) sys- rounded edges and other faults tem developed at the Fraunhofer ILT in the cut contour. observes the interaction zone through Contacts Below: Starting sequence of a large laser welding unit with the beam path with a digital high- undesired transient events in speed camera. The process zone and Dipl.-Ing. P. Abels, Tel.: -428 the processing speed. the surrounding area are illuminated [email protected] by an integrated secondary light source Dr. S. Kaierle, Tel.: -212 which almost completely outshines the [email protected] light emitted in laser machining. The images of the process are interpreted by a computer in real time. The surface structure of the workpiece is analyzed, especially in areas outside the interaction point. By calculating the two- dimensional correlation, the motion vector of the workpiece is determined

Fraunhofer ILT Annual Report 2007 113 Robust autonomous joint tracking for quality assurance in laser welding

Task Results and Applications

The integration of a joint tracking sys- The autonomous joint tracking system tem with coaxial process control for is different from conventional seam the butt welding of D36 shipbuilding tracking systems in that it performs an steel is to be tested. This application additional measurement of the relative uses a hybrid welding process with a speed between the sensor and work- double-focus laser beam followed by piece. This offers the advantage that MIG welding. the number of measured signals recorded can be kept to a minimum. More- The aim is to examine the improve- over, this method is not affected by ment of a system for joint tracking twisting and lateral movement of the with integrated optical speed measure- welding head as positional errors are ment in comparison with a conven- avoided by direct measurement of tional forerun sensor. In addition, the the relative shift. By taking positional scope for process observation with errors into account, it is also no longer the object of quality assurance simul- necessary to calibrate the sensor after taneously with processing is to be a tool change or after changing the investigated. robot path or feed speed. The process observation system in welding appli-

cations with CO2 laser radiation is currently being further developed, prima- Method rily with a view to detecting welding errors. The camera-based system for coaxial process control (CPC) with external illumination developed at the Fraunhofer ILT is used as the sensor system. The Contacts CPC system is integrated in the beam Above: Measured speed components in feed direction relative to path of the processing laser by means Dipl.-Ing. W. Fiedler, Tel.: -390 the observation camera. of a dichroitic mirror. [email protected] Below: Camera image of a structural Dr. S. Kaierle, Tel.: -212 steel plate butt-welded at v = 2.4 S The wavelength and power of the laser [email protected] m/min, s = 6 mm. radiation used (CO2 laser up to 8 kW beam power) makes the set-up particularly challenging. The coaxially arranged camera permits visualization of the molten bath by recording the reflected radiation from the processing area.

114 Fraunhofer ILT Annual Report 2007 Strategies for process monitoring in plastics welding using laser radiation

Task Results and Applications

Industrial laser welding of plastics To conduct the fundamental tests, an should be as robust as possible with experimental arrangement using suit- regard to batch fluctuations of the able modules and specially adapted material, permissible production tole- optical elements was built. In this ar- rances of the individual parts and rangement the processing laser radiation assembly tolerances, but unavoidable and the radiation emitted or reflected fluctuations in the parameter range by the workpiece are transported in a can nevertheless occur. The resultant common beam path. To this end, the processing faults have to be reliably optical and spectral beam paths were detected, even at high production vo- calculated and all the optical compo- lumes. The aim is to make it possible nents were provided with correspond- to use optical process monitoring in an ing coatings. For observations using industrial context to detect problems a CMOS camera, which is sensitive in that can occur in plastics welding. the visible wavelength range between 400 nm and 900 nm, the suitability of various illumination strategies was Camera image: welding of PC, examined. During the investigations it 2 mm + 2 mm, 19 W, 3 m/min, Method was found that the seam width, joint 500 Hz. defects, scratches and decomposition The work is carried out jointly with the can be detected on the materials poly- industrial partners Amtron GmbH, Huf carbonate (PC), polypropylene (PP) and Tools GmbH and LIMO-Lissotschenko polyamide (PA) when using locally re- Mikrooptik GmbH under a project solved observation under bright field funded by the ‘Stiftung Industriefor- illumination. schung’ industrial research foundation. A key aspect of the research is to examine the specific informative capabilities of coaxial locally integrated and Contacts locally resolving process observation. Methods for measuring the secondary Dipl.-Ing. S. Mann, Tel.: -321 radiation and observing with external [email protected] illumination are also compared. A pro- Dr. S. Kaierle, Tel.: -212 cessing head using a modular optical [email protected] system developed at the Fraunhofer ILT was designed and built for this purpose, making it possible to perform simultaneous observation with the various strategies.

Fraunhofer ILT Annual Report 2007 115 False friends

in the molten bath length and width Task during processing were observed and documented using a specially deve- False friends are not exactly popular - loped image processing algorithm either in private life or in welding. for the CPC system. Given that the When metal sheets are lap-welded by dynamics of the molten bath are used means of laser radiation, a false friend to detect any faults, individual images may be created if there is too wide a do not provide an adequate basis for gap between the parts to be joined, monitoring. This special challenge was even though the root of the weld is successfully overcome by analyzing visible. A dreaded process fault has oc- image sequences. curred, and the sheets are not welded together. It is the job of coaxial process control (CPC) to detect the defect. Results and Applications

The correlation of the molten bath Method length with the gap in the lap weld was shown for the described application. The CPC system developed at the Bridgeable gaps result in a reduced Fraunhofer ILT is located directly in width of the melt. Defective joints the beam path of the laser processing which cannot be detected either from system. Observation is conducted with the top or bottom of the seam result the beam. The secondary radiation in a longer molten bath, whereas the emitted during the process is decoupled width does not change. The CPC sys- from the beam path by means of spe- tem with the analysis algorithm deve- cial optical components and observed loped determines the length and width with high-speed cameras. The recor- of the molten bath and thus enables ded process images are interpreted by the false friend to be detected. a computer in real time. The integration of external illumination provides inno- The field of application for this moni- vative options. The processing operation toring method covers a broad range of is illuminated by a light source which sectors in which lap welds produced by almost completely outshines the light laser radiation are required. Particularly emitted during welding. This makes it in the auto industry, many interesting possible to distinguish between molten possibilities exist for its application, and solid material. The tests show that especially in the welding of car body on a sheet combination of stainless parts. steel, the defective joint in the lap weld correlates with the length and width of the melt zone at the interaction point. The characteristic changes Contacts

Dipl.-Ing. P. Abels, Tel.: -428 [email protected] Dr. S. Kaierle, Tel.: -212 Image sequence for analyzing the [email protected] externally illuminated process zone. Intermediate stages of image analysis through to automatic approxi- mation of the interaction zone by means of a rectangle (from top to bottom).

116 Fraunhofer ILT Annual Report 2007 Analysis and application of methods and algorithms to ensure constant product quality

Task Results and Applications

The introduction of new process se- The applicability of generally valid, quences and their monitoring and con- reduced models to the production trol represents a great challenge both process is being examined at the for the machine manufacturer and the Fraunhofer ILT using laser cutting as user of the production facilities. In par- an example. To this end, the requisite ticular the difficulty involved in plann- sensor systems are being designed and ing for the possible occurrence of verified. The work includes developing faults or disruptions calls for new ap- new methods for signal generation proaches which enable the functioning (see figures) and analysis. and performance of automated production processes to be assured at an In addition, all the machine, product, early stage through monitoring and process and sensor data are being active control. classified in detail and systematically recorded.

The goal is to achieve a deeper under- Method standing of the process by determining and dealing with measurement un- In the Cluster of Excellence »Integrative certainties in the sensor system on Production Technology for High-Wage the one hand and uncertain model Countries«, greater insights into pro- parameters on the other. cess models, signal analysis methods and systems for quality monitoring and This forms the basis for the integration measurement uncertainty detection of self-optimizing setup, monitoring are being gained. A key area is the and control systems into the production development of process-overarching process. approaches based on the mutual inter- Camera image of a laser-cutting disciplinary exchange of experience process without external illu- and knowledge among individual mination (above), with external specialist areas. Contacts illumination (below).

The work at the Fraunhofer ILT focuses Dipl.-Ing. S. Mann, Tel.: -321 on the development of methods and [email protected] algorithms for the automated setting- Dr. S. Kaierle, Tel.: -212 up, monitoring and control of laser [email protected] cutting processes.

Fraunhofer ILT Annual Report 2007 117 Computational steering system for parallelized simulation calculations

The CS system and numerical tools use Task a client-server architecture, with communication via the message passing The use of computer simulation in interface (MPI). A command line inter- laser production technology sets high face permits the initialization of batch requirements for the coupling of models. operation for parameter studies. The analysis of solution characteristics is considerably improved by a means of controlling the simulation procedure during computation. The task consists Results and Applications in preparing an environment (framework) for the rapid and flexible deve- The basic functionality of the numerical lopment of parallelized simulation toolbox has been completed. Initial simu- calculations in a modular system. The lation programs have been produced framework contains: as a modular system and tested in appli- • Computational steering system (CSS) cation projects. Examples of CS system • Visualization / analysis applications include welding (upper fi- • Data structures for coupling gure), cutting (lower figure) and super- • Numerical methods sonic gas flow.

The work presented is funded by the German Research Foundation DFG Method in the Excellence Cluster »Integrative Production Technology for High-Wage The computational steering system Countries«. (CSS) is expanded by adding a numerical toolbox and lays down a uniform interface/program structure for simulation codes. The required flexibility is Contacts achieved by using the programming Above: CSS welding. Below: CSS cutting. language C++, a uniform data struc- Ulrich Jansen, Tel.: -163 ture and algorithms from the Standard [email protected] Template Library (STL). Abstract data Prof. Dr. W. Schulz, Tel.: -204 structures and basic template classes [email protected] are defined for numerical tools, and initial variants of numerical tools are implemented in the following areas: • Grid generation • Parallelization • Solution of linear equation systems • FEM, FVM methods • Automatic differentiation

118 Fraunhofer ILT Annual Report 2007 Laser Measurement and Testing Technology Business Area Laser Measurement and Testing Technology

The services provided by this business area include the development of measurement and testing processes and related equipment for material analysis and for geometric testing and surface inspection. The requisite measurement and testing software is tailored to customer-specific problem areas. Material analysis is based on the deployment of laser-spectroscopic processes, focusing on the analysis of metallic and oxidic materials, identification testing of high- alloy steels, rapid recognition of materials for recycling tasks and analysis of gases and dust. Special electronic components are developed for the parallel processing of detector signals of high bandwidth.

In biophotonics joint projects are carried out in the field of highly sensitive fluorecence detection for protein chips Laser-induced plasmas ignited and laser scattered light measurements on rock samples during the single particle analysis for the in sub-µl test volumes for protein separation of minerals. crystallization. As part of the area’s work on geometric testing and surface inspection components, devices and equipment are being developed for obtaining 1 to 3D information about the geometry or surface properties of workpieces. These include processes and special systems for testing the stability of bar and strip products and devices for the 1D to 3D scanning of unit goods. Target markets include the production and the recycling industry which conduct measurement and testing fast and close to the process.

120 Fraunhofer ILT Annual Report 2007 Contents

Blue lasers for ultra-high precision Optical stand-off detection triangulation - BLU 122 of explosives and improvised explosive devices - OFDEX 131 Identification testing of pipeline components using laser Marker-free Raman screening 132 spectroscopy - LIAS 123 Quantitative polarized Element-specific characterization light microscopy 133 of steel scrap streams 124 Laser coagulation system Rapid identification with integrated real-time of light metal alloys for monitoring of vascular occlusion 134 automated sorting - SILAS 125 Integrated microfluidic diagnostic Single particle analysis for systems - IMIKRID 135 the separation of minerals during the extraction of primary raw Endoscope for »cold« laser materials - EIGER 126 neurosurgery 136

Imaging laser analysis Optical coherence tomography of element distribution (OCT) in endoscopy 137 in construction materials 127 Optical coherence tomography Online analysis of minerals (OCT) for layer thickness at the extraction site 128 measurement of loose goods 138

Rapid laser-assisted analysis White-light Mach-Zehnder of metallic and non-metallic interference microscopy in inclusions in steel - REAL 129 transmission 139

Characterization of ultrafine particulate matter in industrial process emissions 130

Fraunhofer ILT Annual Report 2007 121 Blue lasers for ultra-high precision triangulation - BLU

At the same time, construction materials Task are systematically conducted with the aim of producing more stable There is a need for new concepts and lightweight sensors. These, in to meet the increased requirements conjunction with time and space mo- of modern manufacturing lines with dulation of the laser beam, will form automated process and quality control. the basis for a new generation of trian- This includes new concepts of laser gulation sensors. triangulation sensors. More compact, lighter, faster, more precise and more stable are just a few of the features demanded by industrial users, such as Results and Applications rolling mills and automotive industry. As part of the BLU collaborative re- Today’s commercially available laser search project, which is financed by diodes operating in the blue-violet wave- the German ministry of economics and length range do not meet the high a number of small and medium-sized beam-quality specifications required enterprises, novel technologies are for precision triangulation. A highly being tested together with industrial stable device for coupling the beam partners for use in triangulation sensors. into a single-mode fiber that is suitable for industrial applications is therefore being developed together with one of the project partners. The improved Method beam quality enables measurements to be performed to an accuracy that can One aspect of the project involves in- only be achieved with HeNe-lasers at vestigating the use of new shorter-wave- present. In parallel to the development length laser beam sources in triangu- on the sensor, trials of optical measur- lation sensors. The use of such sources ing systems employing new stabilization and a coupling into single-mode optical methods are being tested on products fibers is expected to yield a higher with a metallic bright surface at a cold- spatial resolution and accuracy than rolling mill. Furthermore, investigations is possible with the sensors that are are being carried out on new methods Laboratory setup using blue-violet commercially available at present. for measuring the contours of high- laser for triangulation. precision components with a high surface quality.

Contacts

Dipl.-Ing. (FH) A. Lamott, Tel.: -133, [email protected] Dr. R. Noll, Tel.: -138, [email protected]

122 Fraunhofer ILT Annual Report 2007 Identification testing of pipeline components using laser spectroscopy - LIAS

Task Method

Industrial pipeline systems are com- A scanner equipped with movable mir- monly found in chemical engineering rors directs the laser beam onto freely plants, at oil and gas extraction sites, definable areas of the workpiece. A and in thermal and nuclear power spectral analysis of the resulting plasma plants, as well as being used in the glow is performed to identify the ma- food processing industry, including terial on the basis of the concentration bottling plants, and by manufacturers of alloy elements it contains. The sur- of liquid gas products. To ensure the face does not need to be prepared safety and reliability of the piping fitt- beforehand. Foreign matter on the sur- ings, the appropriate materials for the face, e.g. oils, oxides or scale, is either application must be employed - both locally ablated or penetrated by the in terms of resistance to corrosion and laser. LIAS has integrated reference their compatibility with one another. samples that it uses for automatic self-testing, thus complying with the Manufacturers of pipeline components requirements of ISO 9001 with respect (fittings, pass-over offsets, and runs) to the control of measuring and test must therefore guarantee that the equipment. material composition of their products conforms to specifications. When integrated in an automated manufacturing line, LIAS verifies the identity of each Results and Applications manufactured product without slowing down the production flow. The results The test pieces in this instance are are output at the same rate as the pipeline components of different geo- production process and are fully do- metries and dimensions. The system is cumented. Non-conforming products designed for industrial application and can be rejected automatically. is capable of performing fully automated material identification tests on up to 4 million test pieces per year.

Contacts

Dipl.-Ing. (FH) R. Fleige, Tel.: -133 [email protected] Dr. R. Noll, Tel.: -138 [email protected]

Above: Measuring head containing the laser beam source and scanner. Below: Use of flexibly directed laser beam for identification testing. Several freely definable points on the test pieces can be verified. Duration of test < 0.5 sec/test point, tested volume (HxWxD) 100 x 400 x 400 mm3.

Fraunhofer ILT Annual Report 2007 123 Element-specific characterization of steel scrap streams

Task Results and Applications

As well as responding to environmental In the first phase of the project, laser concerns, the recycling of steel scrap for analysis experiments were performed reuse in steel production has taken on on samples of steel scrap in order to a new, economic, significance due to find laser parameters that permit the the rising cost of raw materials and the laser to penetrate coatings or layers growing scarcity of natural resources. of dirt. The design of the demonstrator The better we are able to characterize setup for on-site testing was completed the chemical composition of steel and construction started. scrap, the greater the value of the re- covered fraction. Conventional frac- The work is being supported financially tionation processes (magnet extraction, by the European Community’s Re- density analysis, etc.) only cover a limi- search Fund for Coal and Steel (RFCS) ted number of characteristics, and are and the Fraunhofer-Gesellschaft. generally not sufficiently selective with respect to the elements that can play a critical role in recycling. The defined task is to develop and verify the suita- Contacts bility of a process for the on-site characterization of steel scrap streams on Dipl.-Ing. D. Eilers, Tel.: -308 conveyor belts. [email protected] Dr. V. Sturm, Tel.: -154 [email protected] Dr. R. Noll, Tel.: -138 Method [email protected]

Laser-induced breakdown spectroscopy (LIBS) was chosen as the method for Typical example of material entering (above) and leaving (below) a shredder element-selective characterization. plant. Further development of this method was required to enable a reliable average element concentration to be obtained. A demonstration setup will be installed in a shredder plant and on the premises of an arc furnace for the purposes of on-site testing.

124 Fraunhofer ILT Annual Report 2007 Rapid identification of light metal alloys for automated sorting - SILAS

Task Results and Applications

Preliminary sorting of shredded alumi- In cooperation with a laser manu- num scrap is a necessary stage in the facturer, a laser system was developed secondary production of the light me- that is capable of emitting time- and tal. As well as being separated into space-modulated laser light from a two main categories, cast and wrought single oscillator. The first part of this alloys, the latter category of material laser beam penetrates surface coat- is further subdivided into the so-called ings or contamination. Subsequent 1000-groups. Conventional separating analysis pulses in the same pulse train and preparation methods are not sui- then interact with the material lying table for this task. As a result, a signi- underneath the surface. The scanner ficant proportion of aluminum pro- system is repositioned during the duction still takes place using energy- emission of this laser beam. Experi- intensive primary production methods. mental results show that it is possible The most challenging aspect of the to achieve crater depths of 300 µm preliminary sorting of scrap is the fact and more in aluminum materials using that a chemical analysis has to be per- this laser beam, depending on the formed in a fraction of a second on beam orientation. This approach has discrete moving objects on the con- made it possible for the first time to veyor belt. Especially in the case of old successfully demonstrate the separation aluminum scrap, surface contamination of mixed scrap consisting of cast and or coating material has to be removed wrought alloys. In this application, the within the allotted measuring time in identification accuracy was over 90% order to generate a representative, ob- at a yield of 100%. At present, the ject-specific test result. improved analysis method is being used to validate the performance of a demonstration sorting machine as part of an industrial study on subcategories Above: Snapshot of a laser- Method of wrought alloys. Development work induced plasma on a moving on a prototype is projected to start in piece of aluminum scrap Aluminum workpieces are scattered on January 2008. (v = 3 m/s). a conveyor belt (v = 3 m/s) and passed Below: Image of craters in a ground aluminum surface. a detection unit. A set of coordinates On the left: Mark left by the from the object surface, selected on analysis pulse of a spark-source the basis of optical and geometrical Contacts spectrometer (crater depth < 10 µm); on the right: 4 craters characteristics, is transmitted to a laser produced by a time- and space- measuring instrument. A pulsed laser Dipl.-Phys. Ü. Aydin, Tel.: -431 modulated laser beam beam is focused on this selected zone [email protected] (crater depths > 150 µm). by means of scanner mirrors. The laser- Dr. R. Noll, Tel.: -138 These craters were produced while the sample was traveling induced plasma is detected antiparallel [email protected] at a velocity of v = 3 m/s relative to the beam propagation direction and Dr. J. Makowe, Tel.: -327 to the laser measuring system. analyzed by a spectrometer in real time. [email protected] The time/space-modulated laser beam was repositioned accor- This multi-element analysis serves as dingly. the basis for ejecting the workpieces into different fractions at the end of the conveyor belt.

Fraunhofer ILT Annual Report 2007 125 Single particle analysis for the separation of minerals during the extraction of primary raw materials - EIGER

Task Results and Applications

Before processing extracted primary The first stage of the project involved raw materials, such as limestone or conducting fundamental spectroscopic other minerals and ores, the mineral analyses as a means of assessing the of economic value has to be separated various influential factors. In the se- from inferior inter-grown accessory cond stage of the project, an initial se- rock. Owing to the comparatively low ries of tests was carried out on moving price at which these raw materials are rock samples (limestone/dolomite) with sold, the separation must take place in a known chemical composition. The the immediate vicinity of the extraction main difference between these sam- site, transportation of the extracted ples was their relative MgO/CaO con- material being uneconomical in many tent. The threshold values of the Mg cases. At present, there is no cost-effi- detector channels were therefore sub- cient automated process capable of jected to closer examination in respect sorting primary raw materials online on of their suitability as sorting criteria. In the basis of single particles. A collabo- each examined class of materials, the rative research project was therefore identification correctness exceeded launched to develop a laser-assisted 90% at a recovery of 100%. sorting process for the separation of limestone and dolomite. Its scope may In order to carry out these tests, a new conceivably be widened to include Paschen-Runge spectrometer with de- other ores and minerals. tector channels adapted to the above- mentioned application was bought, and a special housing designed for it in compliance with the IP standard for Method use in an industrial environment. Once this spectrometer system has been in- After reducing and separating the raw tegrated in the demonstration sorting Above: Laser-induced plasmas ignited on rock samples. material, it is fed to the measuring plant, it is planned to conduct endu- Below: Paschen-Runge spec- system in the form of single particles rance tests using a high volume of ma- trometer system enclosed in a and/or rock fragments. These samples terials (> 1 t). The flexible design of the vibration-proof double-walled are individually analyzed by laser spec- sorting system makes further validation housing. The spring-suspension base of the spectrometer and troscopy in the moving stream of mate- tests using different material streams its housing designed to EMC rial and ejected as separate fractions in conceivable. The online separation of specifications allow the system accordance with the measurement re- metals offers interesting prospects as a to be deployed in a real-life industrial environment or an out- sult. One of the foremost objectives of supplementary application to the sepa- door location. the project is to implement a demon- ration of minerals and ores. strator and prove its ruggedness under real-life industrial operating conditions.

Contacts

Dipl.-Phys. Ü. Aydin, Tel.: -431 [email protected] Dr. R. Noll, Tel.: -138 [email protected]

126 Fraunhofer ILT Annual Report 2007 Imaging laser analysis of element distribution in construction materials

Task Results and Applications

Corrosive changes can be provoked in As part of the project, a demonstrator concrete structures and buildings, such was designed and built that enables as bridges and multistory car parks, by the creation of automated 2-dimen- various environmental factors (vehicle sional element maps. The range of wave- exhaust fumes, road salt, etc.). The lengths used to detect the plasma soundness of the structure can be per- emissions was broadened to allow manently damaged by the infiltration parameters to be set for different am- of elements such as nitrogen, sulfur bient gases and pressures when per- and most particularly chlorine. To opti- forming measurements in a controlled- mize the cost of remedial maintenance, environment test chamber. This makes the concentration and depth of pene- it possible to detect spectral lines at tration of these elements must be de- wavelengths ranging from 130 nm to termined as accurately as possible. An 920 nm. A detection limit for elemen- analysis system is being developed that tal concentrations of chlorine of below will enable engineers to determine the 1 percent is targeted by the use of content of these elements in building spectral lines in the VUV and IR ranges. materials on-site, allowing them to assess damage on the basis of »ele- The project is being conducted with ment maps« and repair the structure the financial support of the German in an appropriate manner as a function ministry of economics, various indus- of the degree to which the structure trial partners, and the Fraunhofer- has been damaged. Gesellschaft.

Method Contacts

Above: View through the Laser-induced breakdown spectroscopy Dipl.-Phys. C. Gehlen, Tel.:-127 observation window into the is a non-contact method used to analyze [email protected] test chamber. A laser-induced the chemical composition of solids, Dr. R. Noll, Tel.:-138 plasma is ignited on the surface liquids and gases. It allows the con- [email protected] of the sample, and its emissions are fed to a spectrometer via centration of different elements to be a direct light channel. established simultaneously very rapidly. Below: ILCOM demonstrator. Drilling cores extracted from the structure are split, and the fractured surface is scanned using a focused Nd:YAG laser beam. At the points where the laser pulses hit the surface, minute quantities of the drilled core are vaporized and ionized, creating a plasma. The element-specific line emissions from the plasma enable the elemental composition of the material at this point to be determined.

Fraunhofer ILT Annual Report 2007 127 Online analysis of minerals at the extraction site

The use of the analysis module in under- Task ground workings imposes special demands with respect to vibration, dust In underground mining, the machines and water resistance. used to extract minerals are still controlled manually. The inevitable presence of surrounding rock lowers the quality of the extracted mineral and Results and Applications increases the quantity of material that has to be transported to the surface. Initial results suggest that laser-induced One of the objectives of the project is breakdown spectroscopy is a viable to develop an analysis module for use means of distinguishing between the in underground workings that enables material to be exploited and associated the relative proportion of surrounding surrounding rock. In the case of hard rock to be determined in real time. coal, for instance, the presence of high levels of silicon and other elements In surface mining, prospect holes are and a rapidly decreasing carbon con- drilled to investigate mineral deposits. tent indicate that the extracted material A real-time analysis module for these contains a high ratio of surrounding borings is being developed that can take rock. the place of the presently employed laboratory analysis. On-site analysis The project is being conducted with will make it possible to adapt the hole the financial support of the German matrix dynamically to the prevailing ministry of economics, various small geological conditions and consequently and medium-sized enterprises and in- produce a more accurate geological dustrial partners, and the Fraunhofer- model using fewer resources. Gesellschaft.

Above: Samples of limestone and hard coal as well as surround- Method Contacts ing rock. Below: Eickhoff shearer loader. The rock dust produced during ex- Dipl.-Phys. T. Kuhlen, Tel.: -308 traction is drawn off and a chemical [email protected] analysis is performed by laser-induced Dr. P. Jander, Tel.: -440 breakdown spectroscopy directly in the [email protected] air-stream. The online analysis process Dr. R. Noll, Tel.: -138 is capable of distinguishing between [email protected] the mineral of economic value and surrounding rock.

In the case of underground mining, the project focuses on differentiating between hard coal and clay slate. In the case of surface mining, the analysis system is initially intended for use in limestone quarries. The same technique is nevertheless transferable to other types of exploitable mineral and associated surrounding rock.

128 Fraunhofer ILT Annual Report 2007 Rapid laser-assisted analysis of metallic and non-metallic inclusions in steel - REAL

Task Results and Applications

The number, distribution and compo- A number of steel samples were sition of metallic and non-metallic in- examined for their distribution of clusions are important quality criteria metallic and non-metallic inclusions. in steel manufacturing. These inclusions, A particular focus of this series of tests which typically range in size from was to investigate the behavior of 0.1 µm to 100 µm, affect the proper- double analysis pulses by comparison ties of the material, reducing its fatigue with the previously employed single strength and even leading to fracture. pulses. Different algorithms for pro- Inclusions frequently consist of a com- cessing the element maps and filtering bination of different elements, for out the inclusions from the bulk mate- instance MnS or TiN. A means of de- rial were tested and evaluated. tecting the presence of so-called light elements such as C, N, O, P and S is The work is being supported finan- therefore required. As far as possible, cially by the Research Fund for Coal the analysis is to be performed without and Steel (RFCS) and the Fraunhofer- the need for elaborate preparation of Gesellschaft. the sample.

Element map showing MnS inclusions, S (red) Mn (blue). Contacts Method Dipl.-Ing. (FH) M. Höhne, Tel.: -160 A ground or milled sample is all that [email protected] is needed to analyze the purity of the Dr. R. Noll, Tel.: -138 steel. The sample is placed in a measur- [email protected] ing chamber filled with a shielding gas, where its surface is scanned by the beam of a focused diode-pumped solid- state laser. A small quantity of the sample material is vaporized at the focal point of the laser beam to form a plasma. The emissions from the plasma are resolved spectrally, converted into electrical signals, and analyzed. The high measuring frequency of 1 kHz employed in this method enables a sample surface area of 10 mm x 10 mm to be analyzed in 10 minutes. During this time, element maps for up to 48 different chemical elements are produced simultaneously, with a resolution of 20 µm.

Fraunhofer ILT Annual Report 2007 129 Characterization of ultrafine particulate matter in industrial process emissions

Task Results and Applications

Air pollution with fine and ultrafine Results of analyse conducted on emis- particulate matter has recently become sions from steel factories indicate, for recognized as one of the main public example, an elevated content of lead, health risks. Significant sources of cadmium and copper in particulates anthropogenic particles are vehicular of about 200 nm in diameter, whereas traffic and industry. higher concentrations of other metals are found in larger particulates. The Extremely small nanoscale particulates chemical composition of the particu- represent an elevated health risk be- lates varies widely as a function of cause their size allows them to pene- their size, and is characteristic of the trate deep into the human organism. specific process giving rise to their At the same time, these aerosol parti- emission. This finding permits process culates are the most difficult to detect »fingerprints« to be established, which and make a high demand on the mea- in turn permit a classification of the suring instrument, hence there is a sources of emissions. The correlation pressing need for further research. between particulate size and compo- This project concerns the development sition also allows a better estimation of a method for determining the com- of the health risk associated with the position of particulates, with particular different types of emission. Measure- emphasis on the concentration of ments based on particulate size can heavy metals. also be obtained when analyzing particulates directly in the air stream. The short time required for such measurements allows them to be used directly Method for process control. The results of the project will be used to develop emission- Two methods of measurement are reduction strategies for the industrial being developed on the basis of laser- plants under study. The method can induced breakdown spectroscopy for also be employed universally in other the chemical analysis of the particulates. branches of industry, engine develop- In the first method, the particulates are ment and nanotechnology. collected, classified by size, on filters and then analyzed in the laboratory. The project receives financial support In the second method, single particles from the European Union’s Research are analyzed directly in the air stream. Fund for Coal and Steel (RFCS) and the This latter method additionally permits Fraunhofer-Gesellschaft. rapid online characterization. To obtain Above: Laser spectroscopy reliable measurement results, it is ne- methods can be used to analyze cessary to produce samples and aero- both particulates collected on sols that enable instruments to be Contacts filters and airborne particulates. Below: Lead content of fine calibrated for all relevant elements dust particulates ranging in size over a range of concentrations cover- Dr. C. Fricke-Begemann, Tel.: -196 from 40 nm to 4 µm emitted ing several orders of magnitude. [email protected] by two different production Dipl.-Phys. N. Strauß, Tel.: -196 processes. [email protected] Dr. R. Noll, Tel.: -138 [email protected]

130 Fraunhofer ILT Annual Report 2007 Optical stand-off detection of explosives and improvised explosive devices - OFDEX

of false alarms when searching for Task explosive materials. On the basis of experience gained by the Fraunhofer ILT Terrorist attacks have been on the rise in laser analysis over distances of up for the past several years, particularly to 12 meters, the researchers are deve- in the form of car and suitcase bombs. loping methods and data analysis algo- So far, there is no system available that rithms that will allow them to detect can detect such »improvised explosive the slightest traces of explosives even devices« (IEDs) from a safe distance. over distances of up to 50 meters.

Furthermore, there is a great demand in the civil and environmental protection sector for systems capable of remote Results and Applications chemical analysis. These could help to monitor emissions or provide assistance Tests carried out on ammonium nitrate, when dealing with accidents involving one of the main components of ANFO hazardous chemicals, for example in explosives, show that laser-induced the petrochemical industry. breakdown spectroscopy can help to detect small amounts of nitrogen- Raman spectral lines of a containing compounds over a distance fingerprint containing traces of 5 meters, even in the presence of of ammonium nitrate. atmospheric nitrogen. The sensitivity Method of Raman spectroscopy has meanwhile been improved to such an extent that Four Fraunhofer Institutes have joined the presence of traces of ammonium forces to develop a system for the nitrate in a fingerprint corresponding stand-off detection of hazardous and to a density of 160 µg/cm2 can be un- explosive materials, based on several mistakably identified. optical methods that complement one another. The project is being implemented with the financial support of the Fraunhofer- The Fraunhofer ILT, for its part, is inves- Gesellschaft. tigating the use of both laser-induced breakdown spectroscopy and Raman spectroscopy. Laser-induced breakdown spectroscopy is a technique Contacts which enables high measurement frequencies and allows the elemental Dr. P. Jander, Tel.: -440 composition of a material to be deter- [email protected] mined precisely even over a distance Dr. R. Noll, Tel.: -138 of several meters. Raman spectroscopy [email protected] enables substances with similar atomic compositions to be differentiated on the basis of frequency measurements of the molecules’ characteristic natural vibration. The two techniques thus deliver complementary information on the sample under test. Combining the two techniques increases the probabi- lity of detection and reduces the rate

Fraunhofer ILT Annual Report 2007 131 Marker-free Raman screening

Task Results and Applications

The analysis of biochemical interactions, Initial recordings of the Raman spectra especially specific interactions between of proteins with a good signal-to-noise proteins and their binding partners, ratio were obtained using a laboratory is one of the basic tasks performed in setup consisting of a highly sensitive pharmacological laboratories as part Czerny-Turner spectrometer with a of the drug discovery process. In expe- cooled CCD detector. To separate the rimental screening, fluorescent dyes excitation light from the Raman signals, are used as marker molecules when a compact module was designed and searching through extensive libraries built to accommodate a narrow-band- of compounds for potential active drug width dichroic mirror, a laser line filter ingredients that possess a specific affi- and a band-pass filter. The spectrometer nity to biologically relevant target pro- was connected to this arrangement via teins (e.g. enzymes or signal transmit- a tunable fiber coupler. The fiber acts ters). In a scientific project together as a pinhole aperture, resulting in a set- with partners from industry and re- up that functions similarly to a confocal search, we have been investigating the lens system with three-dimensional use of Raman spectroscopy as a means spatial resolution. The setup is capable of detecting biochemical interactions of measuring minimal-volume samples without employing fluorescent mar- and is designed to face upwards, allow- kers, and we are building a demons- ing fluids in glass-bottomed microtiter Compact module for face-up confocal Raman microscopy. trator for experimental screening. plates to be analyzed.

The project is being conducted with the financial support of the German Method ministry of economics, various small and medium-sized enterprises, and the Using Raman difference spectroscopy, Fraunhofer-Gesellschaft. it is possible to analyze binding events between proteins and their ligands. A specific ligand binding event alters the vibrational spectrum of the inves- Contacts tigated protein. By computing the difference between the spectra of the Dr. C. Janzen, Tel.: -124 bound and the free proteins, the band [email protected] shifts can be obtained in a sensitive Dr. R. Noll, Tel.: -138 way. To prevent the Raman signals [email protected] from being submerged under a strongly fluorescent background, the project employs a special background reduction technique. A narrow-bandwidth external cavity diode laser allows images of two mutually offset Raman spectra to be obtained by slightly shifting the excitation wavelength. Since only the Raman signals present this offset, while the fluorescent background does not, it is then possible to remove the effect of the fluorescent background.

132 Fraunhofer ILT Annual Report 2007 Quantitative polarized light microscopy

Task Results and Applications

Polarized light microscopy between A polarized light microscope for the crossed polars is the standard technique described quantitative analysis was for viewing birefringent structures integrated in a demonstrator for auto- (crystals, polymers or glass under com- mated, rationalized protein crystallo- pressive or tensile stress). However, the graphy. The polarized light microscope quality of the images obtained is highly is capable of analyzing the difficult- dependent on the orientation of the to-characterize precipitates that often sample relative to the direction in form during crystallization experiments. which the applied light is polarized. An important aspect is the ability to A novel type of quantitative polarized distinguish between amorphous, non- light microscopy makes it possible to birefringent and microcrystalline, bire- generate false-color images that are fringent precipitates. It is also possible unaffected by the position of the sam- to clearly differentiate between bacte- ple and reproduce the transmission, rial growth or image distortions caused amplitude and orientation of its bire- by interfacial artifacts and the crystalline fringence. Such images can be used, structures themselves. And finally, a for instance, to determine the quality qualitative characterization of the crys- of single crystals being grown to inves- tals is also possible, since only single tigate protein structure. crystals exhibit a uniformly oriented optical axis. The demonstrator and its polarized light microscope are currently being evaluated in the applications la- Method boratory of a partner institute, where various aspects of polarized light mi- The key components of a quantitative croscopy are being tested. polarized light microscope are a mono- chrome light source, a rotating polari- The project is being conducted with zer, and a circular analyzer consisting the financial support of the German of a λ/4 plate and a polarization analy- ministry of economics, various small zer. These components are integrated and medium-sized enterprises, and the in a transmission microscope with a Fraunhofer-Gesellschaft. lens and a CCD camera for recording the images. The quantitative birefringence analysis is performed by taking a series of images with the polarizer set Contacts to different angles each time. By mathematical transformation, it is possible Dr. C. Janzen, Tel.: -124 to calculate the transmission, amplitude [email protected] and orientation of the birefringence at Dr. R. Noll, Tel.: -138 any point on the sample on the basis [email protected] of the individual frames.

Above: Demonstrator for protein crystallization with integrated quantitative polarized light microscope. Below: Characterization of the quality of protein crystals. The images show the transmission (above), amplitude (middle) and orientation (below) of the birefringence. Fraunhofer ILT Annual Report 2007 133 Laser coagulation system with integrated real-time monitoring of vascular occlusion

pixel represents a scanning depth of Task 4 µm. The imaging parameters such as frame repetition rate, frame size, pixel Minimally invasive laser surgery in size, and the A-scan can be adapted to blood-carrying tissue requires an en- the process being examined. doscopic coagulation technique to occlude transected blood vessels. By tissue coagulation high-power cw laser sources are suitable for this purpose, Results and Applications because they can be coupled into an endoscopic laser surgery system via the An extensive series of coagulation ex- optical channel. An optical coherence periments were conducted ex vivo on tomography system capable of provid- over 700 blood vessels of the cardio- ing three-dimensional images of blood vascular network of pigs’ hearts, using vessels has been developed in order to varying settings for output power and observe the coagulation process and power density and varying the size of m

m define suitable coagulation parameters. the irradiated area and the duration of 1 exposure. As a result, a process window could be identified in which laser coagulation resulted in reliable occlu- Method sion of vessels with diameters ranging from 150 µm to 1000 µm. In a second The endoscope developed for the laser stage of the project, coagulation ex- coagulation application focuses a laser periments were conducted using con- beam (Nd:YAG, λ = 1064 nm, P = 25 W) stant irradiation parameters and the through a micro-optical channel onto time dynamics were observed with the the blood vessel requiring occlusion in- aid of the OCT system. For the first side the surgical cavity. Changes occurr- time, we were able to visualize the dy- ing in the blood vessel during coagu- namic processes that take place during Above: Series of sections through a blood vessel (Ø 200 lation are observed using optical cohe- coagulation in a blood vessel and µm) during coagulation. The rence tomography (OCT). A galvanome- could determine the average duration duration of irradiation increases tric scanner mirror moves a measuring of exposure required for cauterization. from left to right. There is an beam transversally to the diameter of On average, the coagulation process interval of 100 ms between each of the consecutive images. the blood vessel being coagulated. Dur- took about 2 s to cauterize a blood The sequence starts when the ing the transverse scan, the OCT system vessel. The software package developed coagulation laser is switched records image data in the vertical plane for the laser coagulation system permits on; the time to coagulation is approx. 0.6 s. perpendicular to the movement of the the coagulation process to be viewed Below: This diagram plots the measuring beam, to a depth of approxi- dynamically as a series of sections change in the distance between mately 1.5 mm below the surface of (photo above) and as a diagram plott- the upper and lower walls of the tissue. A new depth scan (A-scan) is ing distance against time (photo below). the blood vessel (Ø 900 µm) during the coagulation process started every 50 µm to obtain images of as a function of time, starting a 1-mm cross-section of the vessel. The from the instant at which the A-scan is performed at a frequency of laser is switched on. The time to occlusion by coagulation is 200 Hz, and a cross-sectional image Contacts 3.5 s. consists of 20 A-scans with a lateral displacement of 50 µm. These image Dr. A. Lenenbach, Tel.: -124 capture settings enable a 1-mm cross- [email protected] section of the vessel to be imaged at Dr. R. Noll, Tel.: -138 a frame repetition rate of 10 Hz. One [email protected]

134 Fraunhofer ILT Annual Report 2007 Integrated microfluidic diagnostic systems - IMIKRID

using the confocal single-molecule de- Task tector. The use of single nanoparticles as reactive sensor surfaces in the fluid The aim of the IMIKRID project is to stream of a microfluidic system mini- develop a technology platform for mizes surface effects such as the non- point-of-care diagnostics providing specific adsorption of proteins, which a highly sensitive means of detecting limit the sensitivity of any diagnostic molecular marker proteins in blood system. The combination of optical serum and sweat. tweezers and single-molecule detection is expected to provide a highly sensitive diagnostic tool for detection of marker concentrations in the single-molecule Method range down to below 10-12 mol/l.

IMIKRID refers to a diagnostic chip integrated in a microfluidic cell together with four independent single-molecule- Results and Applications sensitive sensor components that convert a biological response into an The ability to detect serum proteins optical or electronic signal. The surfaces on the basis of their specific binding of the sensors extend into the fluidic to nanoparticles will permit preventive channel and are coated with multi- early diagnosis of cardiovascular di- functional nanoparticles that bind spe- seases and cancer. This is not possible cifically with the analyte molecule of at present, due to the detection limit interest in the blood serum. In the case of 1 ng/ml (10-11 mol/l) in state-of-the- of the electronic sensor (seFET = sen- art, antibody-based serological tests. sitivity enhanced FET), the biological IMIKRID offers a means of implement- interaction is detected without the use ing large-scale integrated sensors with of marker molecules by means of single-molecule sensitivity for applica- charge transfer in the sensor. The sig- tions at the point of care. The R&D Above: Branching of the micro- nal transducer function of the optical activities of the IMIKRID project are fluidic channels in an integrated sensor is based on the marking of the supported by the BMBF and are being sensor chip. Source: Fraunhofer bound analyte molecule with a fluores- implemented together with partner in- Institute for Applied Information cent label, which provides an optical s-titutes of the Fraunhofer-Gesellschaft Technology FIT, Biomolecular Optical Systems department. signal of the specific binding of the and the Institute for Micro Sensors in Below: Optical tweezers system analyte when excited with light of a Erfurt. for integration in a confocal suitable wavelength. The Fraunhofer detection system for single-molecule diagnostics. ILT is developing a tool to test and calibrate the IMIKRID sensors at single- molecule level. This device consists of Contacts a confocal single molecule detector with integrated optical tweezers. The Dr. A. Lenenbach, Tel.: -124 optical tweezers permit the controlled [email protected] transport of a nanoparticle to the sen- Dr. R. Noll, Tel.: -138 sor surface of the transducer to trigger [email protected] a reproducible single-molecule response. The optical tweezers can also be used to position a nanoparticle in the fluidic stream as a specific capture probe, enabling direct detection of the binding of the analyte molecule of interest

Fraunhofer ILT Annual Report 2007 135 Endoscope for »cold« laser neurosurgery

and suction system. Ablation experi- Task ments were performed in the laboratory on tissue samples of pigs’ hearts and The resection of intracranial tumors brains in order to determine the laser involves opening a hole in the cranium parameters providing the greatest ab- of the same size as the tumor to be lation efficiency. During these experi- rejected. Endoscopic removal of brain ments, the samples were placed in tumors by means of keyhole surgery a flow cell through which water was would represent a significant improve- pumped at flow velocities varying from ment in neurosurgical practice since 0.2 l/min to 2 l/min. This water washed it would reduce the »patient trauma«. ablated fragments of tissue out of the With this objective in mind, the Fraun- ablation zone to prevent laser light hofer ILT and partners in industrial and from being absorbed by debris in the research fields are developing an en- path of the ablation laser beam. The doscope for use in plasma-induced flow rate was regulated to produce the »cold« laser neurosurgery. maximum ablation efficiency at a constant pulse repetition rate.

Above: Endoscope for »cold« laser ablation with a stereotactical Method frame. Source: MRC-Systems Results and Applications GmbH, Heidelberg. The main component of the surgical Middle: Cross-section through a square-shaped ablation crater in intervention system is an endoscope The ablation experiments on pig’s heart the muscle tissue of a pig’s heart. measuring 5.5 mm in outer diameter tissue enabled an energy threshold Below: The sharp edges of the ab- housing a micro-optical channel of value of Ep = 30 µJ to be established lation geometry are clearly visible 2.8 mm in width. The endoscope’s for plasma-induced laser ablation. The in the plan view. micro-optics guide the laser beam into diameter of the ablation crater at a the surgical cavity and focus it onto pulse energy of 200 µJ lay between the tissue to be ablated. The tip of the 50 µm and 100 µm. The edges of the endoscope is fitted with a tilted mirror ablation craters were sharply defined 1 mm to decouple the ablation laser at a per- and exhibited no thermal effects of pendicular angle to the endoscope’s the laser light on the adjacent tissue. axis of symmetry. The laser employed

for ablation is a Nd:YVO4 picosecond The development of the endoscope laser connected in series with an INNO- is supported by the BMWI and is being SLAB amplifier having the following carried out together with partners specifications: output power P = 10 W, from industry and clinical research.

pulse energy Ep = 1 mJ, pulse duration

tp = 25 ps, wavelength λ = 532 nm. The pulse repetition rate can be varied between f = 1 kHz and 10 kHz. The Contacts 1 mm ablation process is automated, and the laser focus can be set to scan any geo- Dr. A. Lenenbach, Tel.: -124 metry within a cylindrical volume mea- [email protected] suring 5 cm in diameter and 12 cm in Dr. R. Noll, Tel.: -138 height by rotating the tilted mirror, [email protected] displacing the focusing lens, and altering the depth of the endoscope. The ablated tissue is removed from the surgical cavity by an integrated rinsing

136 Fraunhofer ILT Annual Report 2007 Optical coherence tomography (OCT) in endoscopy

optical distance of a reference beam Task on which the measuring beam is super- imposed. This interferometric measure- Therapeutic techniques involving en- ment (A-scan) is performed at a fre- doscopy call for new diagnostic me- quency of 200 Hz and a digital resolu- thods that provide surgeons with in- tion of 1.6 µm per pixel. The resulting formation on intraoperative events. As image data can be processed to obtain an alternative to white-light and fluo- a 3-D image. rescence endoscopy, optical coherence 1 mm tomography (OCT) is a high-resolution, interferometric measuring technique with which it is possible to obtain Results and Applications image data of tissue morphologies without the use of marker molecules. The endoscopic OCT diagnostic has an The main medical application envisaged axial resolution of approx. 25 µm at a for OCT is the online monitoring of laser lateral resolution of 20 µm. In a series surgery processes. The Fraunhofer ILT of validation experiments, cross-section is developing an OCT module for the images were taken of vessels ex vivo in endoscopic detection and measure- the vascular system of a porcine heart. ment of blood vessels. Its purpose is The images were recorded with the to monitor the cauterization of blood probe in a static position while the en- vessels by laser coagulation using doscope mirror was rotated to move Above: OCT cross-section image of two blood vessels high-energy laser light during keyhole the measuring beam across the cross- downstream of a bifurcation, surgery. section of the vessel. A clear contrast measured using the endoscope. could be observed between the vessels The vessels have a diameter of 420 µm and 440 µm respectively. and the tissue surrounding them. Middle: A horizontal section With the help of a software program through the three-dimensional Method specially developed for OCT diagnosis, OCT dataset showing the bifur- the measurement data can be displayed cation point. To obtain the maximum possible pene- as 2-D sections. Image sequences can tration depth into the tissue of approx. be used to evaluate changes in the 5 mm 2 mm, a beam source with a center vessels' position and geometry, for A wavelength in the region of 1300 nm example after thermal interaction due is employed. Light is introduced into to irradiation with laser light. the surgical cavity via an optical fiber B and a rigid endoscope. The parallel measuring beam is decoupled by a deflection mirror mounted on the tip Contacts of the endoscope at 90° to its longitu- C dinal axis and focused on the tissue to Dipl.-Phys. S. Hölters, Tel.: -436 be examined by means of a microlens. [email protected] The surface of a three-dimensional tar- Dr. R. Noll, Tel.: -138 Below: Endoscope for use with OCT, consisting of: get volume can be scanned point by [email protected] A micro-optical channel and point through this lens by sliding the B rotating mirror tube. endoscope along its own axis, rotating C Assembled endoscope. The micro-optical channel and the deflection mirror and adjusting the mirror tube are assembled in focusing lens. A scan performed using a coaxial arrangement and each the OCT system delivers depth cues can be moved with respect extending from the surface into the to the other. Diameter of the micro-optical channel 3.0 mm; tissue at each measuring point. This is diameter of the assembled achieved by periodically varying the system 5.5 mm.

Fraunhofer ILT Annual Report 2007 137 Optical coherence tomography (OCT) for layer thickness measurement of loose goods

ments, a pair of scanner mirrors has to Task be used to move the OCT measuring beam across the surface of interest in During production, variations can order to measure the surface or layer occur in the wall thickness of loose geometries. goods made of plastic, such as translucent bottles or the preforms from which they are manufactured. To prevent these variations from exceeding Results and Applications the defined tolerance range, random samples are taken from the production The existing OCT system has an axial line at hourly intervals, sawn apart, measuring range in air of 9 mm at a and examined under a light microscope. scanning frequency of 200 Hz and a For greater process reliability and in resolution of approx. 25 µm. Unlike order to improve product quality, an absorptive measuring techniques, OCT automated system for measuring wall permits the use of an epitaxial mea- thickness is required that will provide a surement setup in which the source 100-percent monitoring capability. The and receiver are located in the external envisaged system involves the use of environment of the measured object. optical coherence tomography (OCT), This measurement setup was used to an imaging technique based on inter- determine the position and thickness ferometric measurements that produ- of multilayer preforms and bottles with ces high-resolution 3-D tomographic a minimum layer thickness of approx. images. By recording reflected and 50 µm. The project team is currently scattered light signals, this technique working on the design of special op- permits the non-contact measurement tical systems to compensate for the of the layer thickness of plastic bottles differences in the path length of the and preforms during the production measuring light that occur when using process. The same technique can also OCT to take measurements at two be used to determine the thickness of different sites on the path described by Above: Preforms employed in the manufacture of PET bottles. individual layers of laminate composite a moving object. Optical path length Below: Recording of the materials to a resolution of approxima- compensation is a necessary prerequi- cross-section of a multilayer tely 25 µm. site for the use of OCT techniques to PET preform made using the measure moving samples, because the OCT measuring system. Overall wall thickness approx. measurements are based on the diffe- 4.3 mm; thickness of the inter- rence between optical distances. The facial layer at the midpoint Method OCT measuring system is being vali- approx. 410 µm. dated in the laboratory on moving pre- Data obtained by measuring selected forms guided around a circular path on subsets of the geometry of symmetri- a turntable, to simulate their transport cally round plastic bottles or preforms, on a centrifugal conveyor in the pro- such as the longitudinal profile or duction plant. cross-section, can be extrapolated to provide the distribution of layer thickness over the entire geometry. At a cycle rate of up to 10,000 bottles per Contacts hour, it is possible to provide 100-percent online monitoring of wall thick- Dipl.-Phys. S. Hölters, Tel.: -436 ness and individual layer thicknesses [email protected] during the production process. Because Dr. R. Noll, Tel.: -138 OCT is based on single-point measure- [email protected]

138 Fraunhofer ILT Annual Report 2007 White-light Mach-Zehnder interference microscopy in transmission

Task Results and Applications

Measurements of the refractive index Various experimental approaches were can provide a variety of important piloted in partnership with collaborat- information about the structure and ing cell biologists, pathologists, envi- material properties of microscopic ob- ronmental scientists and crystallogra- jects. In materials research, micro-op- phers. The cell movement of living tical or crystal-optical components can cells and the associated mass transport be qualified using measurements of processes were observed and recorded the refractive index and dispersion. over several hours. Measurements of One of the main difficulties encountered the dry mass of cells were successfully when examining thin, transparent ob- employed to identify tumor cells as dis- jects under a light microscope is that tinct from healthy cells in streak cultures of generating image contrast. When and microscopic sections. This method observing living cells in a dye-free me- will serve as the basis for new applica- dium, optical techniques alone are cations in tumor diagnostics, where real pable of quantifying cells on the basis physical measurements will help to of their refractive index and translating provide a more reliable diagnosis. this into contrast. This measurement Measurements of the dry mass of cells permits the dry mass of the cells to were also employed to determine the be determined, thereby opening the carbon content of various types of door to new applications in biology algae, for subsequent use in environ- and medical diagnostics. mental model calculations. The results showed a significant deviation from the tabulated values currently in use.

Method The aim of the project is to develop a commercial version of an interference The Horn design of the Mach-Zehnder microscope offering not only a unique interference microscope offers the best means of performing high-precision phase resolution for measurements measurements but also featuring ex- of the refractive index coupled with ceptional user-friendliness. maximum enlargement of the light microscope images. This is achieved by integrating two complete microscope optics with identical wavelength cha- Contacts racteristics in the interferometer arms. Modern optomechanical concepts Dipl.-Phys. D. Mahlmann, Tel.: -172 derived from laser technology can be [email protected] used to automate the highly sensitive Prof. Dr. P. Loosen, Tel.: -162 system and make it more user-friendly. [email protected] Above: Combined arrangement of Mach-Zehnder interferometer and matching microscope optics. Middle: Interference contrast image of neurons. Unstained cells can be observed in detailed contrast and quantified. Below: Interference fringe pattern of an optical waveguide. The refractive index profile can be measured to sub-nanometer accuracy as a function of the cur- vature of the interference fringes.

Fraunhofer ILT Annual Report 2007 139 Patents

Patents Germany Patents Europe Patent Applications Patent Applications National International DE 197 80 124 B4 EP 1 399 287 B1 Anordnung zur Formung des Verfahren zum Schneiden von 10 2007 002 888.3 PCT/DE2007/001856 geometrischen Querschnitts zu fügenden Bauteilen mit Laser- Anordnung mit einem fest- Verfahren und Vorrichtung zur mehrerer Festkörper- und/oder strahlung stehenden Festkörpermedium Feinpositionierung eines Werkzeugs Halbleiterlaser mit einer Handhabungseinrichtung 10 2007 002 821.2 DE 101 06 474 B4 Verfahren und Anordnung zur PCT/EP2007/009094 Verfahren sowie Vorrichtung Patents USA Freqenzkonvertierung kohärenter Anordnung mit einem fest- zum Aufbringen einer Korrosions- optischer Strahlung stehenden Festkörpermedium schutzschicht auf Kantenflächen US 7,176,408 B2 von Blechen Method for laser-cutting structural 10 2007 003 759.9 PCT/DE2007/000341 components to be joined Verfahren zur Frequenzstabilisierung Vorrichtung und Verfahren DE 10 2005 026 968 B4 gütegeschalteter Laser zum Fügen von wenigstens zwei Einbringen von Mustern in matte aus thermoplastischem Material Oberflächen durch moduliertes 10 2007 014 665.7 bestehenden Fügepartnern mittels Laserstrahlpolieren Patents Australia Verfahren zur Herstellung laser- Laserstrahlung aktiver Wellenleiterschichten DE 10 2005 010 381 B4 2003249876 Verfahren zur Vermessung von 10 2007 018 400.1 Method and device for carrying Phasengrenzen eines Werkstoffes Optisches System für einen Trademark Applications out emission spectroscopy bei der Bearbeitung mit einem Lasermaterialbearbeitungskopf Bearbeitungsstrahl sowie zuge- 307 58 327.9/42 hörige Vorrichtung 10 2007 024 701.1 TWIST Verfahren zur Materialabtragung Patents China DE 10 2005 022 095 B4 sowie Vorrichtung zur Durch- 307 61 417.4/42 Verfahren und Vorrichtung führung des Verfahrens LIFTEC zur Bestimmung einer lateralen ZL02807825.X Relativbewegung zwischen einem Verfahren und Vorrichtung zum 10 2007 024 700.3 Bearbeitungskopf und einem Erzeugen von extrem ultravioletter Verfahren zur Materialbearbeitung Werkstück Strahlung und weicher Röntgen- mit Laserstrahlung sowie Vor- strahlung richtung zur Durchführung des DE 10 2005 000 840 B4 Verfahrens Verfahren und Vorrichtung zur Elementanalyse mittels 10 2007 029 052.9 Laser-Emissionsspektrometrie Verfahren und Vorrichtung zum Herstellen eines Bauteils auf drei- dimensionalen Daten des Bauteils

10 2007 028 789.7 Verfahren zum Fügen von Hybrid- bauteilen

10 2007 031 244.1 Vorrichtung und Verfahren zur Durchführung statischer und dynamischer Streulichtmessungen in kleinen Volumina

10 2007 038 502.3 Verfahren zum Fügen von mindestens zwei Bauteilen mittels Laserstrahlung

10 2007 039 035.3 Verfahren zur Herstellung eines Bauteils sowie Verwendung des nach dem Verfahren hergestellten Bauteils

10 2007 041 939.4 Vorrichtung und Verfahren für die XUV-Mikroskopie

140 Fraunhofer ILT Annual Report 2008 Dissertations Diploma Theses

Fuhrmann, C. - 19.03.2007 Baatzsch, Andreas Groebner, Mario Roth, Peter Laser-Lichtbogen-Hybridschweißen Untersuchung zur Stirnflächen- Laseranalyse von Einschlüssen in Spektroskopische Analyse laser- bis zu Blechdicken von 25 mm kopplung von Large-Mode-Area- Metallen induzierter Plasmen beim Mikro- Fasern Materialabtrag mit ns-Pulsgruppen Scholz, C. - 23.05.2007 Hamad, Eyad Themal and Mechanical Optimisation Beck, Matthias Messung der Temperatur in Schleifenbaum, Henrich of Diode Laser Bar Packaging Untersuchungen zur Schweiß- biologischem Gewebe während Erhöhung der Aufbaurate beim barkeit des Chrom-Nickel-Stahls der Laserkoagulation SLM Trippe, L. - 03.09.2007 1.4305 am Beispiel der Faser- Reduzieren erstarrter Schmelze in rohrspitze eines endoskopischen Hammer, Philipp Soeryanto, Denny der Bohrung beim Einzelpuls- und Instrumentes Temperaturabhängigkeit der Erarbeitung von Verfahrensgrund- Perkussionsbohren mit Nd:YAG- optischen Eigenschaften von lagen zur Reparatur von einkristallinen Laserstrahlung Biermann, Tim Thermoplasten Shroud-Segmenten eines Flugzeug- Laserstrahlschweißen und -schneiden triebwerks durch Laserstrahl-Auf- mit dem Kombikopf: Verfahrens- Hauck, Sebastian tragschweißen und Systemoptimierung Möglichkeiten und Grenzen bild- rotatorischer Lichtstrahldrehung Temmler, André Binder, Markus Physikalische Ursachen und Grenzen Versuchsumgebung und Grundlagen Hoerstmann-Jungemann, des Strukturierens metallischer zur Ultrapräzisionstriangulation mit Maren Christine Oberflächen durch Umschmelzen blauen Lasern Weißlichtinterferometer zur mit Laserstrahlung Bestimmung der Dispersion der Bock, Mario Gruppenlaufzeit dielektrischer Volkmer, Niels-Christian Untersuchung der elektrischen Spiegel im sichtbaren und ultra- Mikrostanzen mit lokal angepasster und optischen Eigenschaften kurz- violetten Spektralbereich Bauteiltemperatur gepulster Diodenlaser Jedrzejczyk, Daniel Weitenberg, Johannes Buchbinder, Damien Simulation und Experimente zur Ytterbiumdotierte Kristalle bei Konzeption und Erprobung eines nichtlinear optischen Frequenz- hohen Pumpleistungsdichten Pulverdosiersystems zur definiert konversion in periodisch gepoltem ortsaufgelösten Deposition unter- MgO:LiNbO3 Kristall mit Wellenleiter schiedlicher Pulverwerkstoffe für das Selective Laser Melting Kochem, Gerd Konstruktion und Aufbau eines Dietrich, Jens singlemodefasergekoppelten Untersuchung der Effizienzsteige- Trapezlaser-Moduls rung beim Bohren mit zeitlich und räumlich überlagerter Laserstrahlung Küpper, Felix durch Hochgeschwindigkeitsfoto- Erzeugung weicher Röntgen- grafie strahlung in einer gepulsten Gasentladung für den Einsatz in Fitzau, Oliver einem Laborröntgenmikroskop Vergleichende Untersuchungen zur Erzeugung polarisierter Laser- Kuhlen, Tobias strahlung mit Faserlasen Analyse von Feinstaub auf Filter- substraten mittels Laser-Emissions- Funck, Max Christian spektrometrie Auslegung einer miniaturisierten Bearbeitungsoptik für das Laser- Langer, Torsten strahl-Mikrofügen Thermische Auslegung einer Fasereinkopplung für Hochleistungs- Geffers, Christoph diodenlaser Untersuchung zur Ausweitung von Laseranwendungen in der Lu, Xin industriellen Produktion Laserstrahl-Auftragschweißen auf Titanaluminiden mit artähnlichen Goldner, Andreas Werkstoffen Konstruktion eines optischen Sensormoduls für die lasergestützte Ostholt, Roman Schichtdickenmessung Auslegung und Konstruktion eines optischen Systems für eine SLM-Anlage zur variablen Einstellung des Fokusdurchmessers

Fraunhofer ILT Annual Report 2008 141 Scientific Publications

S. Kaierle, W. Fiedler, B. Regaard, B. Jungbluth, M. Vierkoetter, B. Zintzen, T. Langer, J. Geiger, M. Wehner, P. Jacobs, D. Esser, M. Dahmen M. Hoefer, J. Loehring, D. Ober- D. Hoffmann, P. Loosen H. Schinkel, S. Schillberg Anwendung brillianter Dioden- beckmann, D. Hoffmann Heat transport in solid and air- Laser-mediated perforation laser beim Schweißen von Alu- Design and characterization of clad fibers for high-power fiber of plant cells minium-Dünnblechen a rugged and compact setup for lasers Proc. SPIE 6632, 9 S., 2007 Laser Technik Journal 2, 35-38, 2007 widely tunable harmonic gene- Opt. Expr. 15, 16787-16793, 2007 ration in the ultraviolet M. Wehner, T. Mans, W. Meiners, S.Kaierle, M. Dahmen, S. Mann, Proc. SPIE 6455, 1-10, 2007 E. W. Kreutz, K. Walther, A. Lenenbach, C. Wessling, R. R. Poprawe R. Poprawe, S. Angel, E. Ratte, Poprawe Autonomous Production Cell J. Loehring, K. Nicklaus, N. Kujath, W. Bleck, K. Bobzin, E. Lugscheider, Lasertechnik für die Zahnmedizin for Laser Beam Welding D. Hoffmann R. Nickel, K. Richardt, N. Bagcivan Laserzahnheilkunde 3, 191-198, Proc. Int. Conf. on Competitive Diode pumped Nd:YGG laser High-temperature turbine 2007 Manufacturing »COMA 07«, for direct generation of pulsed applications using open porous Stellenbosch, Südafrika 935 nm radiation for water metallic foams with thermal R. Noll 6 S., 2007 vapour measurements barrier coatings and cooling Lasertriangulation Proc. SPIE 6451, in print, 2007 hole arrays In: Handbuch zur Industriellen R. Noll, M. Krauhausen ISCORMA-4, Calgary/Alberta, Bildverarbeitung. Hrsg.: N. Bauer Autoteile unter Laseraugen B. Zintzen, A. Emmerich, J. Geiger, Canada, August 27-31, 2007 Stuttgart: Fraunhofer IRB Verl. Laser + Photonik 2, 30-33, 2007 D. Hoffmann, P. Loosen 11 S., 2007 56-60, 2007 Effective cooling for high-power C. Johnigk fiber lasers K. Walther, M. Brajdic, I. Kelbassa R. Noll, M. Krauhausen Berührungslos - präzise - Proc. of the 4th Int. WLT-Conf. on Increase of drilling velocity by Lasertriangulation für die steuerbar Lasers in Manufacturing, Munich, use of superposed laser radiation Online-Messung geometrischer MO Metalloberfläche 61, 24-27, June 2007 Proc. of the 4th Int. WLT-Conf. on Größen in der Produktion 2007 5 S., 2007 Lasers in Manufacturing, Munich, In: Handbuch zur Industriellen June 2007 Bildverarbeitung. Hrsg.: N. Bauer J. Geiger, B. Erben, D. Hoffmann, B. Regaard, W. Fiedler, S. Kaierle 4 S., 2007 Stuttgart: Fraunhofer IRB. Verl S. Altmeyer Error detection in lap welding 260-275, 2007 Characterization of high power applications using on-line melt H. Schinkel, P. Jacobs, S. Schillberg, multimode combiners pool contour analysis by coaxial M. Wehner I. Miyamoto, A. Horn, J. Gottmann CLEO Europe 2007, Munich, process monitoring with exter- Infrared picosecond laser for Local Melting of Glass Material Germany, June 18-21 nal illumination perforation of single plant cells and Its Application to Direct 1 S., 2007 Proc. of the 4th Int. WLT Conf. on Biotechnol. Bioeng. 99, 244-248, Fusion Welding by Ps-laser Pulses Lasers in Manufacturing, Munich, 2007 J. Lasermicro/Nanoeng. 2, 7-14, C. Franz, S. Mann, S. Kaierle June 2007 2007 Comparison of process moni- 5 S., 2007 D. Petring toring strategies for laser Integriertes Laserstrahlschneiden J. Gottmann, D. Wortmann, transmission welding of plastics M. Haverkamp, K. Wieching, und -schweißen: Reduzierung I. Vasilief, L. Moiseev, D. Ganser Proc. of ICALEO October 29 - M. Traub, K. Boucke von Nebenzeiten und System- Manufacturing of Nd:Gd3Ga5O12 November 1, 2007, Orlando, Fl. Fiber-coupled diode laser mo- aufwand ridge waveguide lasers by pulsed 602-606, 2007 dules with wavelengths around EALA 2007, Bad Nauheim laser deposition and ultrafast 2 µm 15 S., 2007 laser micromachining M. Dahmen, W. Fiedler, B. Regaard, Proc. SPIE 6456, 9 S., 2007 Appl. Surf. Sci. 254, 1105-1110, S. Kaierle P. Albus, B. Burbaum, I. Kelbassa 2007 Continuous process control C. Wessling, M. Traub, D. Hoffmann Laser cladding of mesh structures during laser beam welding of Fiber coupled diode laser of on HPT liner and NGV parts L. Peter, R. Noll small section aluminium sheet high spectral and spatial beam Proc. of the 4th Int. WLT-Conf. on Material ablation and plasma Proc. of the 4th Int. WLT Conf. on quality with kW class output Lasers in Manufacturing, Munich, state for single and collinear Lasers in Manufacturing, Munich, power June 2007 double pulses interacting with June 2007 Proc. SPIE 6456, 1-7, 2007 3 S., 2007 iron samples at ambient gas 5 S., 2007 pressures below 1 bar I. Miyamoto, A. Horn, J. Gottmann, J. Gottmann, L. Moiseev, D. Wort- Appl. Phys. B 86, 159-167, 2007 R. Noll, M. Krauhausen D. Wortmann, F. Yoshino mann, I. Vasilief, L. Starovoytova, Den Bewegungszustand des Fusion Welding of Glass Using D. Ganser, R. Wagner T. Jambor, K. Wissenbach Blechs einfrieren Femtosecond Laser Pulses with Laser deposition and laser Micro laser cladding with high QZ Qualität und Zuverlässigkeit 52, High-repetition Rates structuring of laser active quality fibre lasers 36-40, 2007 J. Laser Micro/Nanoeng. 2, 57-63, planar waveguides of Er:ZBLAN, Proc. 4th Int. WLT-Conf. on Lasers 2007 Nd:YAG and Nd:GGG for in Manufacturing, Munich, June integrated waveguide lasers 2007 Proc. SPIE 6459, 10 S., 2007 193-197, 2007

142 Fraunhofer ILT Annual Report 2008 Scientific Publications

R. Schmitt, B.E. Damm, L. Juschkin V. Sturm, A. Brysch, R. Noll D. Petring, C. Fuhrmann, N. Wolf, D. Wortmann, L. Moiseev, Mit weicher Röntgenstrahlung Online Multielement Analysis R. Poprawe I. Vasilief, D. Ganser, L. Starovoytova, hochgenau messen of the Top Gas of a Blast Furnace Progress in Laser-MAG hybrid J. Gottmann In: Optische Messung technischer by Laser-induced Breakdown welding of high-strength steels Waveguide lasers of Er:ZBLAN Oberflächen in der Praxis Spectroscopy (LIBS) up to 30 mm thickness and Nd:GGG by pulsed laser Düsseldorf: VDI-Verl. Berg- und Hüttenmännische Proc. of ICALEO, October 29 - deposition and fs-laser micro- VDI-Berichte. 1996 Monatsh. 1, 28-32, 2007 November 1, 2007, Orlando, Fl. structuring 329-337, 2007 300-307, 2007 Proc. 4th Int. WLT-Conf. on Lasers R. Noll, M. Krauhausen in Manufacturing 2007, Munich, M. Hoefer, M. Traub, R. Klein- Online-Lasermesstechnik J. Wilkes, K. Wissenbach June 2007 dienst, H. Sipma, H.-D. Hoffmann, für Walzprodukte Rapid Manufacturing of ceramic 821-826, 2007 P. Wessels, P. Burdack stahl und eisen 127, 99-105, 2007 components by selective laser Multi ten-watt, ultra-stable, melting C. Schnitzler, S. Hambuecker, and tuneable Innoslab-based S. Angel, E. Ratte, W. Bleck, Proc. of the 4th Int. WLT-Conf. on O. Ruebenach, V. Sinhoff, single frequency MOPA K. Bobzin, E. Lugscheider, Lasers in Manufacturing, Munich, G. Steckman, L. West, C. Wessling, Proc. SPIE 6451, 7 S., 2007 R. Nickel, K. Richardt, N. Bagcivan, June 2007 D. Hoffmann K. Walther, E.W. Kreutz, I. Kelbassa, 207-211, 2007 Wavelength stabilization of D. Petring, H. Dickler R. Poprawe HPDL array: fast-axis collimation Multifunktionaler Laser- Open porous metallic foams D. Buchbinder, W. Meiners, optic with integrated VHG bearbeitungskopf with thermal barrier coating K. Wissenbach, K. Müller-Lohmeier, Proc. SPIE 6456, 1-7, 2007 MM Maschinenmarkt 22, and cooling hole array for high E. Brandl 34-36, 2007 temperature turbine applications Rapid manufacturing von W. Meiners, A. Weisheit High Temp. Mat. Proc. 11, Aluminiumbauteilen für die Werkstoff-Kompromisse passé? D. Petring, H. Dickler 321-344, 2007 Serienproduktion durch Selec- Form + Werkzeug 5, 78-81, 2007 Nebenzeiten senken und tive Laser Melting (SLM) Flexibilität steigern V. Sturm Euro-uRapid2007, Frankfurt/M., M. Haverkamp, G. Kochem, K. Technica 56, 72-74, 2007 Optical micro-lens array for December 3-4, 2007 Boucke, E. Schulze, H. Roehle laser plasma generation in 6 S., 2007 1.1 W Four-wavelength P. Albus, A. Boglea, B. Burbaum, spectrochemical analysis Raman pump using BH lasers J. Holtkamp, I. Kelbassa, V. Nazery- J. Anal. Atom. Spectr. 22, D. Wortmann, M. Ramme, Optical Fiber Communication and Goneghany, A. Olowinsky, 1495-1500, 2007 J. Gottmann the National Fiber Optic Engineers D. Petring, M. Poggel, F. Schmitt, Refractive index modification Conf. OFC/NFOEC 2007 F. Schneider, N. Wolf, R. Poprawe E. Willenborg using fs-laser double pulses 1-3, 2007 Neue Schweißtechnologien Polieren mit Laserstrahlung Opt. Expr. 15, 10149-10153, 2007 mit neuen Lasern Kunststoffe 97, 63-66, 2007 Proc. of the 10th Int. Aachen S. Höges, W. Meiners Welding Conf. iASTK'07 I. Kelbassa, K. Walther, L. Trippe, Selective Laser Melting 229-242, 2007 W. Meiners, C. Over Proc. 41. Jahrestagung Dt. Ges. Potentials of manufacture and f. Biomed. Technik im VDE, Aachen, M. Leers, C. Scholz, K. Boucke, repair of nickel base turbine Germany, September 2007 M. Oudart components used in aero 2 S., 2007 Next generation heat sinks engines and power plants by for high-power diode laser bars laser metal deposition and M. Traub, H.-D. Plum, H.-D. Hoff- Semiconductor Thermal laser drilling mann, T. Schwander Measurement and Management J. Aerospace Power 22, 739-748, Spaceborne fiber coupled Symposium, 2007 2007 diode laser pump modules for SEMI-THERM 2007, 23. Annual IEEE intersatellite communications 105-111, 2007 W. Fiedler, M. Dahmen, S. Kaierle Proc. SPIE 6736, in print, 2007 Process control of laser beam M. Leers, K. Boucke, C. Scholz, welded small section aluminum R. Wagner, J. Gottmann T. Westphalen sheets Sub-wavelength ripple formation Next generation of cooling Proc. of ICALEO, October 29 - on various materials induced approaches for diode laser bars November 1, 2007, Orlando, Fl. by tightly focused femtosecond Proc. SPIE 6456, 10 S., 2007 271-276, 2007 laser radiation 8th Int. Conf. on Laser Ablation M. Traub, M. Bock, H.-D. Hoffmann, E.W. Kreutz, L. Trippe, K. Walther, J. Phys.: Conference Series 59, M. Bartram R. Poprawe 333-337, 2007 Novel high peak current pulsed Process development and con- diode laser sources for direct trol of laser drilled and shaped material processing holes in turbine components Proc. SPIE 6456, in print, 2007 J. Lasermicro/Nanoeng. 2, 123-127, 2007

Fraunhofer ILT Annual Report 2008 143 Lectures

20.01.2007 - M. Hoefer 23.01.2007 - K. Wieching 06.03.2007 - M. Poggel 07.03.2007 - A. Gillner Multi ten-watt, ultra-stable and Fiber-coupled diode laser Laser und Kunststoff - eine feste Aktuelle Entwicklungen zu tuneable INNOSLAB-based single modules with wavelengths Verbindung neuen Laserstrahlquellen für frequency MOPA around 2 µm Aachener Laserseminar die Mikroverbindungstechnik Photonics West 2007, San Jose, Photonics West 2007, San Jose, »Laserschweißen von Kunststoffen«, Aachener Laserseminar »Mikrover- CA, USA CA, USA Fraunhofer ILT, Aachen bindungstechnik«, Fraunhofer ILT, Aachen 20.01.2007 - M. Traub 24.01.2007 - K. Nicklaus 06.03.2007 - M. Poggel Novel high-peak current pulsed Frequency stabilization of Transparent und Artungleich 07.03.2007 - A. Olowinsky diode laser sources for direct q-switched Nd:YAG oscillators Aachener Laserseminar »Laser- Mikroschweißen mit Laserstrah- material processing for airborne and spaceborne schweißen von Kunststoffen«, lung - Neue Verfahrenskonzepte Photonics West 2007, San Jose, LIDAR systems Fraunhofer ILT, Aachen mit optimiertem Energieeintrag CA, USA Photonics West 2007, San Jose, Aachener Laserseminar »Mikrover- CA, USA 06.03.2007 - A. Gasser bindungstechnik«, Fraunhofer ILT, 21.01.2007 - J. Gottmann Anlagen- und Systemtechnik für Aachen Laser deposition and laser 30.01.2007 - D. Petring die Laseroberflächentechnik structuring of laser active Integriertes Laserstrahlschneiden Aachener Laserseminar »Vorsprung 07.03.2007 - F. Sari planar waveguides of Er:ZBLAN, und -schweißen: Reduzierung durch Laser-Oberflächentechnik«, Lasermikrofügen von Halbleitern Nd:YAG and Nd:GGG for von Nebenkosten und System- Fraunhofer ILT, Aachen und Keramiken integrated waveguide lasers aufwand Aachener Laserseminar »Mikrover- Photonics West 2007, San Jose, 8th EALA »Automotive Circle 06.03.2007 - C. Johnigk bindungstechnik«, Fraunhofer ILT, CA, USA International« Conference, Bad Reinigen mit Laserstrahlung Aachen Nauheim Aachener Laserseminar »Vorsprung 21.01.2007 - M. Leers durch Laser-Oberflächentechnik«, 08.03.2007 - A. Gillner Next generation of cooling 02.02.2007 - S. Kaierle Fraunhofer ILT, Aachen Aktuelle Entwicklungen zu approaches for diode laser bars Autonomous production cell neuen Laserstrahlquellen für Photonics West 2007, San Jose, for laser beam welding 06.03.2007 - G. Vitr das Mikrobohren CA, USA COMA 2007, Stellenbosch, Südafrika Randschichthärten und Aachener Laserseminar »Mikroboh- Wärmebehandeln von Stählen ren mit Laser«, Fraunhofer ILT, 22.01.2007 - H.-D. Hoffmann 04.02.2007 - A. Horn mit Laserstrahlung Aachen The INNOSLAB laser, extending Orts- und zeitaufgelöste Diagnose Aachener Laserseminar »Vorsprung the parameter range for indu- von Prozessen induziert durch durch Laser-Oberflächentechnik«, 08.03.2007 - C. A. Hartmann strial and scientific applications ultrakurz gepulste Laserstrahlung Fraunhofer ILT, Aachen Hochgeschwindigkeits- Photonics West 2007, San Jose, Seminarvortrag, Universität Kassel, mikrobohren CA, USA Kassel 06.03.2007 - A. Weisheit Aachener Laserseminar »Mikroboh- Laserstrahl-Auftragschweißen ren mit Laser«, Fraunhofer ILT, 22.01.2007 - J. Löhring 13.02.2007 - A. Gillner von Funktionsschichten für den Aachen Diode pumped Nd:YGG laser Lasers and photonics for Verschleiß- und Korrosionsschutz for direct generation of pulsed industrial manufacturing Aachener Laserseminar »Vorsprung 08.03.2007 - S. Kaierle 935 nm radiation for water Photonics 2007, Eindhoven, durch Laser-Oberflächentechnik«, Prozessüberwachung beim vapour measurements Niederlande Fraunhofer ILT, Aachen Laserstrahlbohren Photonics West 2007, San Jose, Aachener Laserseminar »Mikroboh- CA, USA 13.02.2007 - R. Noll 06.03.2007 - E. Willenborg ren mit Laser«, Fraunhofer ILT, Laser scanning methods for Polieren und Strukturieren mit Aachen 22.01.2007 - M. Wehner verification tasks Laserstrahlung Rapid prototyping of micro- IAEA, Wien, Österreich Aachener Laserseminar »Vorsprung 08.03.2007 - W. Wawers fluidic components by laser durch Laser-Oberflächentechnik«, Mikrobohren mit Laserstrahlung beam processing 23.02.07 - W. Schulz, Fraunhofer ILT, Aachen Aachener Laserseminar »Mikroboh- Photonics West 2007, San Jose, Schneiden mit Laserstrahlung ren mit Laser«, Fraunhofer ILT, CA, USA Kolloquium Fraunhofer SCAI, 06.03.2007 - K. Wissenbach Aachen Birlinghofen Lasereinsatz in der Oberflächen- 23.01.2007 - B. Jungbluth technik - Ein Überblick 19.03.2007 - M. Benk Design and characterization 06.03.2007 - A. L. Boglea, Aachener Laserseminar »Vorsprung Pinchplasma für den Spektral- of a rugged and compact setup Mikro-Kunststoffschweißen mit durch Laser-Oberflächentechnik«, bereich des Wasserfensters for widely tunable harmonic Laserstrahlung - Schweißen im Fraunhofer ILT, Aachen Frühjahrstagung der Deutschen generation in the ultraviolet Sekundentakt bei Geometrien Physikalischen Gesellschaft, Düssel- Photonics West 2007, San Jose, < 100 µm 07.03.2007 - A. L. Boglea dorf CA, USA Aachener Laserseminar Mikroschweißen von Kunststoffen »Laserschweißen von Kunststoffen«, - mit hoher Geschwindigkeit in 19.03.2007 - M. Hermans 23.01.2007 - C. Wessling Fraunhofer ILT, Aachen Mikrodimensionen Entwicklung einer Methode zur Fiber coupled diode laser of Aachener Laserseminar »Mikrover- Beobachtung der Dampf- und high spectral and spatial beam 06.03.2007 - A. Gillner bindungstechnik«, Fraunhofer ILT, Plasmadynamik innerhalb der quality with kW class output Laserstrahlquellen zum Aachen Bohrung beim Laserstrahlbohren power Kunststoffschweißen Frühjahrstagung der Deutschen Photonics West 2007, San Jose, Aachener Laserseminar Physikalischen Gesellschaft, CA, USA »Laserschweißen von Kunststoffen«, Düsseldorf Fraunhofer ILT, Aachen

144 Fraunhofer ILT Annual Report 2008 Lectures

19.03.2007 - A. Mader 27.03.2007 - A. Gillner 05.05.2007 - D. Wortmann 18.06.2007 - R. Poprawe Time-resolved EUV images of Laser structuring of metals and Waveguide lasers of Er:ZBLAN Societal demands determine a tin vapour discharge plasma hard materials and Nd:GGG by pulsed laser the industrial innovation and for future lithography Tagung Mikrobearbeitung, Leuven, deposition and fs-laser the future of laser materials Frühjahrstagung der Deutschen Belgien microstructuring processing Physikalischen Gesellschaft, CLEO / PHAST 2007, Baltimore, Lasers in Manufacturing - LIM Düsseldorf 16.04.2007 - G. Backes MD, USA 2007, München Laserbearbeitung im Triebwerk- 19.03.2007 - I. Mingareev bau 28.05.2007 - A. L. Boglea 18.06.2007 - D. Wortmann Untersuchungen zur Schmelz- Seminarvortrag »Laserbearbeitung Fiber laser welding for Waveguide lasers of Er:ZBLAN dynamik bei der Materialbear- im Triebwerkbau«, Berlin packaging of disposable and Nd:GGG by pulsed laser beitung mit ultrakurzen Laser- polymeric microfluidic-biochips deposition and fs-laser micro- pulsen 18.04.2007 - R. Poprawe EMRS 2007 Spring Meeting, structuring Frühjahrstagung der Deutschen The consequences of societal Strasbourg, Frankreich Lasers in Manufacturing - LIM Physikalischen Gesellschaft, demands for industrial inno- 2007, München Düsseldorf vation and the future of laser 31.05.2007 - J. Gottmann materials processing Manufacturing of Er:ZBLAN 19.06.2007 - M. Brajdic 19.03.2007 - A. Werth ALAW 2007, Orlando, FL, USA ridge waveguides by pulsed Increase of drilling velocitiy by Glasschweißen mit ultrakurz laser deposition and ultrafast use of superposed laser radiation gepulster Laserstrahlung 23.04.2007 - A. Horn laser micromachining for green Lasers in Manufacturing - LIM Frühjahrstagung der Deutschen Investigations on melting and integrated lasers 2007, München Physikalischen Gesellschaft, welding of glass by ultra-short EMRS 2007 Spring Meeting, Düsseldorf pulsed laser radiation Strasbourg, Frankreich 19.06.2007 - J. Geiger LPM 2007, Wien, Östereich Characterization of high power 20.03.2007 - S. Meyer 31.05.2007 - J. Gottmann multimode combiners Zeitaufgelöste Plasmabeob- 23.04.2007 - F. Sari Manufacturing of Nd:Gd3Ga5O12 CLEO Europe / Laser 2007, München achtung bei der Mikrostruk- Laser transmission bonding ridge waveguide lasers by turierung von Metallen mit and welding - Introduction and pulsed laser deposition and 19.06.2007 - M. Wehner ps-Doppelpulsen experimental results ultrafast laser micromachining Laser processing of medical and Frühjahrstagung der Deutschen LPM 2007, Wien, Östereich EMRS 2007 Spring Meeting, bio-analytical devices Physikalischen Gesellschaft, Strasbourg, Frankreich Industry Workshop - Medical device Düsseldorf 25.04.2007 - D. Ganser manufacturing, Laser 2007, Fabrication of NdGGG planar 31.05.2007 - R. Poprawe München 20.03.2007 - M. Leers waveguide laser by pulsed laser Tailored Light - Neue Laser für Next generation heat sinks for deposition neue Anwendungen 19.06.2007 - M. Wehner high power diode laser bars LPM 2007, Wien, Östereich Bundesanstalt für Materialforschung Laser-mediated perforation SEMI-THERM 2007, San Jose, CA, und -prüfung, Berlin of plant cells USA 26.04.2007 - C. Johnigk European Conference on Biomedical Cleaning of technical surfaces 01.06.2007 - W. Schulz Optics - ECBO 2007, München 21.03.2007 - E. Bremus-Koebber- with laser radiation Nichtlineare Dynamik der ling IDC 2007, Düsseldorf Laser-Fertigungsverfahren 20.06.2007 - H.-D Hoffmann Neurite growth on micro- Kolloquium BAM, Berlin Recent developments and patterned polymer surfaces 02.05.2007 - A. Olowinsky perspectives of high-brightness with complex topographies Advances in polymer laser micro 06.06.2007 - S. Kaierle slab-, fiber- and diodelasers (Posterpräsentation) welding Basics for common laser Industrial Workshop »Advanced Biomedica, Aachen SPIE Microtechnologies for the New applications Solid State Lasers«, Laser 2007, Millennium, Maspalomas, Spanien University of Technology, Peking, München 22.03.2007 - C. D. Gehlen China Zeit- und ortsaufgelöste 05.05.2007 - H.-D. Hoffmann 20.06.2007 - P. Albus Untersuchung laserinduzierter High power solid state lasers for 12.06.2007 - J. Gottmann Laser cladding of mesh structures Plasmen beim präzisen Mikro- LPP EUV Pulsed Laser Deposition und on HPT liner and NGV parts Materialabtrag mit Pulsgruppen Sematech »Source Workshop«, fs-Laser Strukturierung für Lasers in Manufacturing - LIM (Posterpräsentation) Baltimore, MD, USA Wellenleiterlaser 2007, München Frühjahrstagung der Deutschen Seminar TU Braunschweig Physikalischen Gesellschaft, 05.05.2007 - H.-D. Hoffmann 20.06.2007 - T. Jambor Düsseldorf Rod-slab-disc-fiber, design and 13.06.2007 - S. Pfeiffer Micro laser cladding with high performance comparison of high Prozesssimulation für das quality fibre lasers 23.03.07 - M. Nießen power laser architectures Laserstrahltiefschweißen Lasers in Manufacturing - LIM Charakterisierung von Verfahrens- CLEO / PHAST 2007, Baltimore, FOSTA Forschungsvereinigung 2007, München parametern beim Schneiden MD, USA Stahlanwendungen, Arbeitskreissit- Kolloquium Fraunhofer SCAI, zung P708: Untersuchung der 20.06.2007 - M. Poggel Birlinghofen 05.05.2007 - D. Wortmann strukturellen Stabilität von Model- Welding of transparent Highspeed production of len zur Schweißverzugssimulation thermoplastics with fibre lasers 23.03.2007 - M. Haverkamp periodical nanostructures using bei Stahlwerkstoffen, Düsseldorf Lasers in Manufacturing - LIM 1.1 W four wavelength Raman femtosecond laser radiation 2007, München pump using BH-lasers CLEO / PHAST 2007, Baltimore, OFC / NFOEC 2007, Anaheim, CA, MD, USA USA

Fraunhofer ILT Annual Report 2008 145 Lectures

20.06.2007 - J. Wilkes 22.06.2007 - K. Walther 07.09.2007 - M. Wehner 11.09.2007 - V. Sturm Rapid manufacturing of ceramic Manufacture of shaped holes Multimodal laser sources for Fast vacuum slag analysis in components by selective laser in multilayer systems by laser surgery and device fabrication a steel works by laser-induced melting drilling and laser structuring: Photonics 21 Workshop »Life breakdown spectroscopy Lasers in Manufacturing - LIM From theory to application Science and Health«, Jena (Posterpräsentation) 2007, München Seminar »Laser application in turbo EMSLIBS 2007, Paris, Frankreich machinery«, München 11.09.2007 - K. Wissenbach 20.06.2007 - S. Kaierle DMD and SLM activities at ILT 11.09.2007 - Q. Wang Process basics and their 22.06.2007 - W. Meiners 4. European Summer School »Rapid Comparison of NIR and UV influence on process stability Technological basics and eco- Manufacturing for Competitiveness«, excitation of LIBS plasma for and diagnostics nomical advantages of additive St. Etienne, Frankreich the detection of explosives LASER INDUSTRY WORKSHOP, manufacture and repair by Laser (Posterpräsentation) München Metal Deposition 11.09.2007 - C. Fricke-Begemann EMSLIBS 2007, Paris, Frankreich Seminar »Laser application in turbo Laser-based measurement 21.06.2007 - B. Zintzen machinery«, München systems for size-dependent 12.09.2007 - R. Noll Effective cooling for high-power particle composition LIBS - from research to industry, fiber lasers 27.06.2007 - J. Holtkamp EAC 2007, Salzburg, Österreich new frontiers for process control Lasers in Manufacturing - LIM Laser assisted micro sheet forming EMSLIBS 2007, Paris, Frankreich 2007, München FLAMN 2007, St. Petersburg, 11.09.2007 - C. D. Gehlen Russland Time and spatially resolved 12.09.2007 - J. Vrenegor 21.06.2007 - A. Gillner investigations of laser-induced Testing of a LIBS machine in Laser micro and nano structuring 27.06.2007 - L. Starovoytova plasmas produced by ns- and a steel works laboratory for for functional surfaces on poly- Fabrication of Nd:Gd3Ga5O12 ps-bursts in the milli- and sub- process control mer parts planar waveguide laser by millijoule regime EMSLIBS 2007, Paris, Frankreich Lasers in Manufacturing - LIM pulsed laser deposition (Posterpräsentation) 2007, München FLAMN 2007, St. Petersburg, EMSLIBS 2007, Paris, Frankreich 20.09.2007 - M. Traub Russland Spaceborne fiber coupled 21.06.2007 - A. Olowinsky 11.09.2007 - Ü. Aydin diode laser pump modules for Laser beam micro joining - new 19.07.2007 - R. Noll Analysis of limestone and dolo- intersatellite communications processes and applications Laserspektroskopische Verfahren mite samples by laser-induced Security and Defense 2007, Florenz, Lasers in Manufacturing - LIM für Sicherheitsanwendungen breakdown spectroscopy for Italien 2007, München Workshop »Optische Mikrosysteme mineral processing für Sicherheitsanwendungen«, (Posterpräsentation) 23.09.2007 - D. Ganser, 21.06.2007 - A. L. Boglea Goslar EMSLIBS 2007, Paris, Frankreich Laser deposition of laser Microwelding of polymeric active planar waveguides for materials with fibre lasers 08.08.2007 - R. Poprawe 11.09.2007 - Ü. Aydin integrated waveguide lasers Lasers in Manufacturing - LIM Frontiers of advanced laser LIBS identification of moving COLA 2007, Teneriffa, Spanien 2007, München manufacturing technology aluminium scrap particles by for 2015 cleaning contamination layers 24.09.2007 - A. Horn 21.06.2007 - W. Schulz National Natural Science Foun- with new tailored laser system Time-resolved investigations on Diagnosis and simulation of dation of China, Peking, China (Posterpräsentation) ultra-fast welding of glass-glass high speed drilling EMSLIBS 2007, Paris, Frankreich and glass-silicon non-interfero- Lasers in Manufacturing - LIM 28.08.2007 - E. W. Kreutz metric time-resolved quantitive 2007, München High temperature turbine appli- 11.09.2007 - M. Höhne phase microscopy for ultrafast cations using open parvus me- Determination of metals and engineering 22.06.2007 - D. Wortmann tallic foams with thermal barrier non-metallic inclusions by rapid COLA 2007, Teneriffa, Spanien Highspeed production of coatings and cooling hole arrays LIBS analysis in steel samples periodical nanostructures using ISCORMA 2007, Calgary, Kanada (Posterpräsentation) 24.09.2007 - D. Wortmann fs-laser radiation EMSLIBS 2007, Paris, Frankreich FS-laser structuring of ridge Lasers in Manufacturing - LIM 05.09.2007 - J. Gottmann waveguides 2007, München Diode pumped ridge waveguide 11.09.2007 - A. Lamott COLA 2007, Teneriffa, Spanien laser by pulsed laser deposition Readout electronics for spec- 22.06.2007 - M. Dahmen and ulftrafast laser microma- trometers used in laser-induced 24.09.2007 - D. Wortmann Repair of blade integrated chining breakdown spectroscopy Waveguidelasers by pulsed disks by laser beam welding - Advanced Laser Technologies, Levi, (Posterpräsentation) laser deposition and fs-laser weldability aspects and approach Finland EMSLIBS 2007, Paris, Frankreich structuring Seminar »Laser application in turbo COLA 2007, Teneriffa, Spanien machinery«, München 05.09.2007 - J. Gottmann 11.09.2007 - N. Strauss Manufacturing of periodical LIBS-based measurement 24.09.2007 - R. Poprawe 22.06.2007 - K. Kowalick nanostructures by fs-laser direct system for size-dependent High speed precision laser Quality assurance for laser writing particle composition ablation applications in turbo machinery Advanced Laser Technologies, Levi, (Posterpräsentation) COLA 2007, Teneriffa, Spanien Seminar »Laser application in turbo Finland EMSLIBS 2007, Paris, Frankreich machinery«, München 26.09.2007 - M. Dahmen Hybrid laser beam welding of structural parts 13th IIW WG Shipbuilding Meeting, Odense C., Dänemark

146 Fraunhofer ILT Annual Report 2008 Lectures

26.09.2007 - M. Dahmen 30.10.2007 - C. A. Hartmann 20.11.2007 - A. Gillner 21.11.2007 - R. Noll Autonomous joint tracking and Investigation on laser micro Neue Laserstrahlquellen für Grundlagen und Methoden applications to robot control ablation of steel using ps-IR die Präzisionsbearbeitung von der Lasermesstechnik - Stand 13th IIW WG Shipbuilding Meeting, pulse bursts Medizinprodukten - Eigenschaften der Technik und neue Entwick- Odense C., Dänemark ICALEO® 2007, Orlando, FL, USA und Potentiale von Kurzpuls- lungen lasern, UV-Lasern bis zu Faser- Aachener Laserseminar »Lasermess- 26.09.2007 - S. Hoeges 30.10.2007 - D. Petring lasern technik für die metallverarbeitende SLM-Generative Fertigung von Progress in laser-MAG hybrid Aachener Laserseminar »Laser- Industrie«, Fraunhofer ILT, Aachen individuellen Knochenersatz- welding of high-strength steels verfahren in der Medizintechnik«, implantaten up to 30 mm thickness Fraunhofer ILT, Aachen 21.11.2007 - F. Schmitt 41. DGBMT-Jahrestagung BMT ICALEO® 2007, Orlando, FL, USA Entwicklung und Einsatz 2007, Aachen 20.11.2007 - S. Hoeges miniaturisierter Scanner für 31.10.2007 - A. L. Boglea Patientenspezifische Fertigung das Laserstrahl-Mikrofügen 27.09.2007 - R. Poprawe TWIST - A new method for the medizinischer Implantate durch Kolloquium Mikroproduktion, Aka- Festvortrag micro-welding of polymers with Selective Laser Melting demie-Hotel Karlsruhe, Karlsruhe 41. DGBMT-Jahrestagung BMT fibre lasers Aachener Laserseminar »Laser- 2007, Aachen ICALEO® 2007, Orlando, FL, USA verfahren in der Medizintechnik«, 22.11.2007 - F. Sari Fraunhofer ILT, Aachen Anwendungsmöglichkeiten von 05.10.2007 - E. W. Kreutz 31.10.2007 - C. Chaminade Laserdurchstrahlverfahren für Evolution of laser sources Laser-based glass soldering for 20.11.2007 - M. Poggel das Fügen von Mikrobauteilen LASERAP 2007, Saint Léger MEMS packaging Laserstrahlfügen medizintech- Kolloquium Mikroproduktion, Aka- Beuvray, Frankreich ICALEO® 2007, Orlando, FL, USA nischer Kunststoffbauteile - von demie-Hotel Karlsruhe, Karlsruhe transparent über flexibel bis zu 06.10.2007 - R. Noll 31.10.2007 - S. Kaierle ultrafein 28.11.2007 - S. Pfeiffer LIBS - R&D projects at Comparison of process moni- Aachener Laserseminar »Laser- Prozesssimulation zur Nutzung Fraunhofer ILT toring strategies for laser trans- verfahren in der Medizintechnik«, als Wärmequelle in FEM-Simu- NASLIBS 2007, New Orleans, LA, mission welding of plastics Fraunhofer ILT, Aachen lationen des Verzugs beim USA ICALEO® 2007, Orlando, FL, USA Schweißen 20.11.2007 - S. Kaierle FOSTA Forschunsvereinigung Stahl- 08.10.2007 - C. Hinke 01.11.2007 - S. Kaierle Moderne Systemtechnik für die anwendungen, Arbeitskreissitzung Individualized serial production Process control of laser beam sichere und effiziente Material- P708: Untersuchung der struktu- for mass customization and welded small section aluminum bearbeitung mit Laserstrahlung rellen Stabilität von Modellen zur open innovation sheet Aachener Laserseminar »System- Schweißverzugssimulation bei MCPC 2007, Boston, DC, USA ICALEO® 2007, Orlando, FL, USA technik«, Fraunhofer ILT, Aachen Stahlwerkstoffen, Düsseldorf

17.10.2007 - R. Poprawe 08.11.2007 - W. Schulz 20.11.2007 - S. Kaierle 01.12.2007 - D. Petring Future high power lasers Modelling and simulation Autonomes Laserstrahlschweißen Present status and future research and new applications of laser processing durch optische Geschwindig- and development of laser ma- Massachusetts Institute of Seminar Graduiertenschule AICES - keitsmessung und Nahtfolge terial processing on sheet metal Technology, Boston, USA Cluster of Excellence, RWTH Aachener Laserseminar »System- in Europe Aachen University technik«, Fraunhofer ILT, Aachen 20th Anniversary of Amada Foun- 24.10.2007 - R. Poprawe dation for Metal Work Technology, New welding technologies 15.11.2007 - H.-D. Hoffmann 21.11.2007 - S. Kaierle Isehara, Japan by new lasers Designaspekte robuster und Prozessüberwachung und Qua- 10. Internationales Aachener kompakter Faserlaser mit Aus- litätssicherung für die Material- 03.12.2007 - D. Buchbinder Schweißtechnik Kolloquium, gangsleistung im kW- Bereich bearbeitung mit Laserstrahlung Rapid Manufacturing von Aachen IWS Faserlaser Workshop, Dresden Aachener Laserseminar »System- Aluminiumbauteilen für die technik«, Fraunhofer ILT, Aachen Serienproduktion durch 24.10.2007 - J. Geiger 15.11.2007 - E. Wagenaars Selective Laser Melting (SLM) Tutorial on fiber laser pumping A tin-based plasma source for 21.11.2007 - S. Mann Euro-uRapid 2007, Frankfurt/Main BRIGHTER-Treffen, Madrid, Spanien extreme ultraviolet lithography Prozessüberwachung mit WELTPP-10, Kerkrade, Niederlande koaxialer Fremdbeleuchtung 04.12.2007 - A. Gillner 29.10.2007 - R. Poprawe Aachener Laserseminar »System- Functional surfaces on polymers Photonics in the 21st century - 20.11.2007 - E. Bremus-Koebberling technik«, Fraunhofer ILT, Aachen for medical products and micro The European Technology Selektive Laser-Oberflächen- optics by laser based embossing Platform Photonics 21 funktionalisierung medizin- 21.11.2007 - A. Lamott and micro structured tools ICALEO® 2007, Orlando, FL, USA technischer Kunststoffbauteile Online Überwachung von Euro-uRapid 2007, Frankfurt/Main Aachener Laserseminar »Laserver- Schweißprozessen mit Emissions- 29.10.2007 - S. Kaierle fahren in der Medizintechnik«, spektrometrie 10.12.2007 - F. Sari From flexible to adaptive manu- Fraunhofer ILT, Aachen Aachener Laserseminar »Lasermess- Laser assisted transmission facturing: an approach for laser technik für die metallverarbeitende bonding materials processing 20.11.2007 - A. Gillner Industrie«, Fraunhofer ILT, Aachen International Conference on (plenary talk) Lasersysteme und Laserverfahren »Wafer Bonding for MEMS Techno- ICALEO® 2007, Orlando, FL, USA in der Medizintechnik - Etabliert logies and Wafer Level Integration«, und trotzdem nicht abgehakt, Halle Ideen für die Zukunft Aachener Laserseminar »Laserver- fahren in der Medizintechnik«, Fraunhofer ILT, Aachen Fraunhofer ILT Annual Report 2008 147 Conventions and Conferences

11.01.2007 07.03.2007, Aachen 14.06.2007 Chair for Laser Technology LLT Aachen Laser Seminar Chair for Laser Technology LLT at RWTH Aachen »Micro bonding by laser« at RWTH Aachen Lecture in association with Seminar organized by Carl Hanser Lecture in association with the the RWTH Colloquium on Laser Publishers, Munich in association RWTH Colloquium on Laser Technology with the Fraunhofer Institute for Technology Prof. Alan H. Epstein, Laser Technology ILT, Aachen. Dr. Holger Schlüter, Trumpf Massachusetts Institute of Additional information: Photonics Inc., Cranbury, NJ, USA Technology, Cambridge, MA www.aachenerlaserseminare.de. »Scheibenlaser in Produktion und »Chip-based gas turbine generators, Entwicklung« rocket engines and chemical lasers« 08.03.2007, Aachen Aachen Laser Seminar »Micro 14.06.2007, Aachen 25.01.2007 drilling by laser - from basic re- Unihits for Kids Chair for Laser Technology LLT search to industrial application« Forum organized by the Chair at RWTH Aachen Seminar organized by Carl Hanser for Laser Technology LLT and the Lecture in association with Publishers, Munich in association Fraunhofer ILT to give advice on the RWTH Colloquium on Laser with the Fraunhofer Institute for scientific careers to students at the Technology Laser Technology ILT, Aachen. Inda Gymnasium in Aachen. Dr. Joseph Pankert, Philips Lighting Additional information: B.V., Eindhoven, NL www.aachenerlaserseminare.de. 20.06.2007, Munich »EUV Lithographie für die Herstel- 28th seminar of the »Aix-Laser- lung hochintegrierter Halbleiter- 23.03.2007, Aachen People« Chips« 27th seminar of the »Aix-Laser- Alumni club meeting of the Fraun- People« hofer ILT and the Chair for Laser 13.02.2007, Aachen Alumni club meeting of the Fraun- Technology LLT with a stage debate Unihits for Kids hofer ILT and the Chair for Laser on the topic of »Living and working Forum organized by the Chair Technology LLT at the laser process- as entrepreneur«. Participants in the for Laser Technology LLT and the ing and consulting center LBBZ debate: Fraunhofer ILT to give advice on GmbH in Geilenkirchen, featuring • Dipl.-Ing. Ulrich Berners, manag- scientific careers to students at the a lecture by Dipl.-Ing. Ulrich Berners ing director, Laser Bearbeitungs- Geschwister-Scholl-Gymnasium in on »Laser processing à la carte - the und Beratungszentrum GmbH, Pulheim. challenges faced by laser contrac- Geilenkirchen tors, as exemplified by LBBZ • Dr. Keming Du, managing director, 06.03.2007, Aachen GmbH«, a tour of the LBBZ GmbH EdgeWave GmbH, Aachen Aachen Laser Seminar »Advance facilities in Geilenkirchen, and a pre- • Dipl.-Ing. Jürgen Jannsen, manag- by laser surface engineering sentation of the Neumann & Esser ing director, RJ Lasertechnik GmbH, - deposition welding, repairs, Group with a subsequent tour of Übach-Palenberg cleaning and polishing« the company in Übach Palenberg. • Dr. Reinhard Kramer, managing Seminar organized by Carl Hanser director, PRIMES GmbH, Pfung- Publishers, Munich in association 03.05.2007 stadt with the Fraunhofer Institute for Chair for Laser Technology LLT • Dipl.-Phys. Axel Bauer, Arbeits- Laser Technology ILT, Aachen. at RWTH Aachen kreis Lasertechnik e.V., Aachen Above: Meeting of the Alumni club »Aix-Laser-People« on March 23, Additional information: Lecture in association with the (who chaired the debate). 2007. www.aachenerlaserseminare.de. RWTH Colloquium on Laser Middle: Aachen Laser Seminar. Technology 22.06.2007, Munich Below: LASER 2007 - Seminar »Laser application in turbo machinery« on 06.03.2007, Aachen Dr. Thomas Riedl, TU Carolo- LASER 2007 - Seminar »Laser June 22, 2007. Aachen Laser Seminar »Laser Wilhelmina, Braunschweig application in turbo machinery« welding of plastics - precision »Organic semiconductor lasers - Immediately following LASER 2007, and flexibility in the micro to from the visible to the UV« a seminar on »Laser application in macro range« turbo machinery« was held in the Seminar organized by Carl Hanser 24.05.2007 NH Hotel at the new Munich trade Publishers, Munich in association Chair for Laser Technology LLT fair center on June 22, 2007. The with the Fraunhofer Institute for at RWTH Aachen seminar was organized by the Laser Technology ILT, Aachen. Lecture in association with Fraunhofer ILT and the Chair for Additional information: the RWTH Colloquium on Laser Laser Technology LLT. Led by Akad. www.aachenerlaserseminare.de. Technology Rat Dr.-Ing. Ingomar Kelbassa, the Dr. Götz Erbert, Ferdinand-Braun- seminar was aimed primarily at Institut für Höchstfrequenztechnik, systems manufacturers, suppliers Berlin and service providers in the engine »Hochleistungslaser - Schlüsselbau- construction sector. It was attended elemente moderner Lasertechnologie« by approximately 40 people, who came to learn about the latest developments in component repair for aircraft engines.

148 Fraunhofer ILT Annual Report 2007 Conventions and Conferences

18.07.2007 25.10.2007 29.11.2007 Chair for Laser Technology LLT Chair for Laser Technology LLT Chair for Laser Technology LLT at RWTH Aachen at RWTH Aachen at RWTH Aachen Lecture in association with Lecture in association with Lecture in association with the RWTH Colloquium on Laser the RWTH Colloquium on Laser the RWTH Colloquium on Laser Technology Technology Technology Prof. Dr. Karl Leo, Institut für Prof. Dr. Karl-Friedrich Klein, V. K. Tikhomirov, Chemistry Angewandte Photophysik (IAPP), Fachhochschule Gießen-Friedberg, Department, Catholic University Dresden Friedberg Leuven, Belgium »Organische Halbleiter: Physik und »Mikrostrukturierte Faser für neue »Rare-earth doped nano-crystals in Bauelementanwendungen« Anwendungen« transparent glass-ceramics and their applications« 16.08.2007, Aachen 08.11.2007 Unihits for Kids Chair for Laser Technology LLT 20.12.2007, Aachen Forum organized by the Chair at RWTH Aachen 30th seminar of the »Aix Laser for Laser Technology LLT and the Lecture in association with People« Fraunhofer ILT to give advice on the RWTH Colloquium on Laser Alumni club meeting of the Fraun- scientific careers to students at the Technology hofer ILT and the Chair for Laser St. Ursula Gymnasium in Aachen. Prof. Dr. T. Baumert, Universität Technology LLT, featuring lectures Kassel, Institut für Experimental- by Dr. Jochen Stollenwerk on »New 27. - 28.09.2007, Thun, physik, Kassel developments in surface engineer- Switzerland »Ultraschnelle Laserkontrolle« ing at the Fraunhofer ILT«, and 29th seminar of the »Aix Laser Dipl.-Ing. Volker Cremer of People« 20.11.2007, Aachen engineering service provider Alumni club meeting of the Fraun- Aachen Laser Seminar Bertrandt Ingenieurbüro GmbH in hofer ILT and the Chair for Laser »Lasers in the field of medical Cologne on »Project management Technology LLT, featuring a tour of technology« at Bertrandt - Tier 1 partner to the the Birr plant of Alstom AG in Swit- Seminar organized by Carl Hanser automotive industry«. The lectures zerland on September 27, 2007. Publishers, Munich in association were followed by a tour of the A presentation on Alstom Power, with the Fraunhofer Institute for industrial research association GIF one of the world’s leading providers Laser Technology ILT, Aachen. Gesellschaft für Industrieforschung of comprehensive power generation Additional information: mbH at the industry and business Meeting of the Alumni club »Aix-Laser-People« on September solutions, was given by Dr.-Ing. www.aachenerlaserseminare.de. park IGA in Alsdorf. 27 and 28, 2007 in Thun, Markus Oehl, process development Switzerland. manager in the hot gas parts 20. - 21.11.2007, Aachen department. The tour of the plant Aachen Laser Seminar included a visit to the production »Laser systems engineering - line for generators and rotors used quality assurance and process in gas and steam turbines. On monitoring, beam sources and September 28, 2007, the seminar handling systems« continued with a trip to laser Seminar organized by Carl Hanser manufacturer LASAG AG in Thun, Publishers, Munich in association Switzerland, including a presen- with the Fraunhofer Institute for tation by Managing Director Dr. Laser Technology ILT, Aachen. Dietmar Wagner and Dr. Ulrich Dürr. Additional information: www.aachenerlaserseminare.de. 18.10.2007 Chair for Laser Technology LLT 21.11.2007, Aachen at RWTH Aachen Aachen Laser Seminar Lecture in association with »Laser measuring technologies the RWTH Colloquium on Laser for the metalworking industry« Technology Seminar organized by Carl Hanser Dipl.-Ing. Stefan Irrgang, IPG Laser Publishers, Munich in association GmbH, Burbach with the Fraunhofer Institute for »Faserlaser für die industrielle Laser Technology ILT, Aachen. Anwendung« Additional information: www.aachenerlaserseminare.de.

Fraunhofer ILT Annual Report 2007 149 Trade Fairs

23.01. - 25.01.2007 08.05. - 11.05.2007 18.06. - 24.06.2007 San Jose, USA Sinsheim Le Bourget, France Photonics West 2007 Control Salon International de l’Aéro- International trade fair for optics International trade fair for quality nautique et de l’Espace and photonics assurance International Paris Air Show Participation by the departments Participation by the department for Participation by the CLFA at the for laser components and for solid- laser measurement and testing exhibition in Hall 4. state and diode lasers of the Fraun- technology of the Fraunhofer ILT CLFA topics: rapid manufacturing hofer ILT and the Chair for Laser at the joint stand hosted together and repair by laser cladding. Technology LLT at the German with LSA - Laser Analytical Systems pavilion. + Automation GmbH in Hall 4. 24.10. - 31.10.2007 ILT/LLT topics: assembly of diode ILT topics: laser measuring products Düsseldorf lasers, characterization of diode and systems for process monitoring K 2007 laser bars, laser systems based on and quality assurance, including a International trade fair for plastics laser bars, high-energy diode laser compact laser measuring device for and rubber modules for space-based applica- spectral element analysis, a system Participation by the micro techno- tions, and solid state lasers. for rapid, locally resolved element logy department of the Fraunhofer analysis, and non-contact laser ILT at the joint Fraunhofer stand in 16.04. - 20.04.2007 measuring systems for chemical Hall 3. Hannover analysis and for determining the ILT topic: welding of plastics. Hannover Messe 2007 dimensional accuracy and geometry International industry fair of products. 29.10. - 01.11.2007 Participation by the micro techno- Orlando, Florida logy department of the Fraunhofer 18.06. - 21.06.2007 ICALEO ILT at the IVAM joint stand. Munich 26th International Congress on ILT topic: Lasers in micro engineer- LASER 2007 Applications of Lasers & Electro- ing, Highlights: micro drilling at LASER 2007 World of Photonics Optics high drilling rates and micro weld- and World of Photonics Congress Participation by the Fraunhofer ing of plastics. 2007 ILT in the lecture sessions and the Participation by the Fraunhofer ILT ICALEO Vendor Program. The Ven- at the joint Fraunhofer stand in dor Program involved 86 exhibitors Above: Joint Fraunhofer stand at Hall B3. from nine countries, including the the EuroMold 2007 in Frankfurt. Middle and below: Joint Fraun- ILT topics: component repair for Fraunhofer ILT in collaboration with hofer stand at the LASER 2007 in aircraft engines by laser cladding; the Fraunhofer CLT, Plymouth, USA. Munich. development of customized diode, fiber and YAG lasers for medical 13.11. - 16.11.2007 engineering, materials processing Munich and satellite communications; rapid Productronica 2007 manufacturing of aircraft, tool and International trade fair for medical components by selective electronics production laser melting (SLM); modeling and Participation by the micro techno- simulation software for optimizing logy department of the Fraunhofer precision drilling processes; micro ILT at the joint Fraunhofer stand in drilling of silicon components for Hall B5. the production of solar cells; micro ILT topic: flexible manufacturing structuring and micro generation; cell for laser micro processing. joining of transparent plastic parts; integrated laser-beam welding and 05.12. - 08.12.2007 cutting without retooling, using a Frankfurt combi-head; coaxial process control EuroMold (CPC) system for online monitoring World fair for moldmaking and of welding and cutting processes; tooling, design and application laser-beam cutting at outputs over development 5 kW using a robust mirror cutting Participation by the surface treat- head. ment department of the Fraunhofer ILT at the joint Fraunhofer stand »Innovations in toolmaking« in Hall 8. ILT topic: High-performance mold inserts for tool construction.

150 Fraunhofer ILT Annual Report 2007 Publications

»Your partner for innovation« Proceedings of the Technology (German/English) Business day TBT’06 This brochure provides a concise over- The proceedings of the Technology view of the Fraunhofer ILT. In addition Business Day, which took place on to presenting a summary of European 03.05.2006 in Aachen with a panel R&D projects conducted by the ILT, the of 13 experts in financial services, brochure also contains a short profile technology marketing, law, sales and of the institute as well as a list of refe- business consulting, are addressed pri- rence customers. marily toward managers of expanding high-tech firms and newly established »Services and Contacts« small companies. The publication pro- (German/English) vides a succinct overview of the emerg- This brochure gives an overview of ing trends and opportunities offered by current services offered and contacts laser technology, mechanical and auto- within the Institute. It also introduces motive engineering. At the same time, focal points of each division of the it also sheds light on many financial, Fraunhofer ILT. legal and marketing questions confront- ing businesses at various stages of their Annual Report 2007 evolution. (German/English) The annual report presents a compre- Technical Brochure: hensive look at the R&D activities of »High-Power Diode Lasers« the Fraunhofer ILT for the respective This technical brochure outlines the business year. Lists of scientific publi- various development activities of the cations and lectures as well as patents, Fraunhofer ILT in the area of high- dissertations, conferences and trade power diode lasers. Included are fairs are also included. The English ver- developments such as the design of sion can only be found on our website special components for laser cooling, at: www.ilt.fraunhofer.de. diode laser bar packaging, diode laser burn-in characterization and the optical Proceedings of the Aachen Collo- design and development of complete quium for Laser Technology AKL’06 diode laser modules. The technical proceedings of the Aachen Colloquium for Laser Techno- Technical Brochure: »Laser Tech- logy AKL’06 (May 3 - 5, 2006) contains nology for Surface Modification TAGUNGSBAND reports from 34 laser manufacturers and Forming« and users outlining the latest develop- This technical brochure provides an ments and technology trends in in- overview of how lasers are employed dustries such as optics, automobile, in the area of surface modification and metal production, tool and die making forming. Included are processes such as well as electrical and electronic as deburring, melting and forming, engineering. Practical case studies polishing, roughening, structuring and highlight various laser processes such activation, re-crystallization, annealing as laser beam welding and cutting, and fine pearlitizing. laser surface technology as well as 03.- 05. MAI 2006 laser micro engineering.

EUROGRESS AACHEN

ILT

Fraunhofer Institut Lasertechnik

Fraunhofer ILT Annual Report 2007 151 Publications

Technical Brochure: »Laser Technical Brochure: »Systems Technology for Wear and Corrosion and Equipment for Laser Materials Protection« Processing« Wear and corrosion protection can be This technical brochure highlights the created by various laser processes. This systems engineering solutions available technical brochure provides insights to Fraunhofer ILT customers. They into processes such as martenistic sur- encompass the planning, development face hardening, remelting, deposition and installation of complete laser welding, alloying and dispersion. facilities and process monitoring and control systems, complemented by fea- Technical Brochure: »Laser Beam sibility studies, training and education Deposition Welding« seminars and consulting services. This technical brochure provides an introduction to the processes and Technical Brochure: »Quality Assu- systems used in laser beam deposition rance in Laser Materials Processing« welding. It also elucidates the differen- This technical brochure explains the Laser in der Kunststoff- und Papiertechnik ces between conventional powder potential for process monitoring and feed nozzles and those used in laser control in laser materials processing. It beam deposition welding. also outlines the services available from the Fraunhofer ILT for the development Technical Brochure: »Rapid Proto- of such monitoring systems. typing and Rapid Manufacturing« This brochure describes the selective Technical Brochure: laser melting process developed at the »Lasers in Mounting and Connecting Fraunhofer ILT which enables complex Techniques« metal parts to be manufactured directly This technical brochure gives an over- from 3D CAD data. It also provides view of the use of laser technology in examples of applications of the laser mounting and connecting techniques. beam generation technique. Micro joining processes such as laser beam bonding and laser beam solder- Technical Brochure: ing are demonstrated. »Lasers in Microstructuring« This technical brochure describes Technical Brochure: »Lasers processes such as laser ablation, in Plastics and Paper Processing« precision cutting, drilling and laser- This technical brochure describes the assisted microforming. use of lasers in the processing of plastics, composite materials, paper and glass. Technical Brochure: »Laser Ablation, Cleaning and Marking« Technical Brochure: This technical brochure outlines »Lasers in Life Science« the advantages of the different laser This technical brochure deals with Laser in Life Science processes and the wealth of potential applications of laser technology in applications. medical engineering. It also describes the use of lasers as tools in microreac- tion processes and biotechnology.

152 Fraunhofer ILT Annual Report 2007 Publications

Technical Brochure: Information Brochure: »Modeling and Simulation« »Optical Technology Courses Written by experts, this brochure pro- at RWTH Aachen« vides an overview of the activities and This brochure summarizes the laser core competencies of the project technology courses available at RWTH group on modeling and simulation. ILT Aachen and is designed specifically for specialists and researchers at the Chair students of mechanical and electrical for Laser Technology LLT of RWTH engineering as well as physics. The Aachen University devise models to brochure details the courses and lectures simulate resonator design concepts on laser technology available to students Studieninfo and beam-guiding and focusing within their major field of study that are Optische Technologien systems, and a variety of machining taught by the individual RWTH chairs an der RWTH Aachen processes including cutting, welding under the auspices of the Fraunhofer ILT. and drilling. Information Brochure: Technical Brochure: »Networks of Competence« »Laser Microscopy« »Networks of Competence« was set A brochure offering insights into up on the initiative of the BMBF and advanced techniques of laser scanning serves as an international marketing microscopy developed at the Fraun- instrument and presentation showcase hofer ILT. for the most highly skilled networks of competence in Germany. Its Internet Technical Brochure: portal, at: www.kompetenznetze.de, »Polishing with Laser Radiation« with its efficient search engine and ILT This technical brochure describes many useful links, provides an ideal the process of laser polishing and its information source and communica- possible applications. tion platform for individuals and organizations in Germany and elsewhere Technical Brochure: »Heat Treat- looking for information and potential ment with Laser Radiation« working partners. This brochure provides an insight into laser-assisted hardening, softening, Information Brochure: annealing and forming. »European Laser Institute ELI« This brochure provides information on Technical Brochure: »Material the European network of recognized Analysis and Process Monitoring centers of R&D in laser technology with Laser« coordinated by the Fraunhofer ILT. This technical brochure provides an The members of this network have set overview of materials analysis systems themselves the goal of making existing and their possible applications. laser know-how in Europe accessible to all interested parties in industry Technical Brochure: »Design and science. The project is sponsored of Diode Laser Heat Sinks« by the European Commission. Further This brochure describes the structure information can also be found at: of diode laser heat sinks, illustrated www.europeanlaserinstitute.org. by prototypes. Product and Project Data Technical Brochure: »Customized Descriptions of projects from the Services for Diode Lasers« Fraunhofer ILT annual reports and This technical brochure provides an specific product information can be insight into research and development downloaded from our website at: activities and customer-specific solu- www.ilt.fraunhofer.de. tions in the field of high-power diode lasers. Fraunhofer ILT Annual Report 2007 153 CD-ROM »Laser Technology«

The program runs using Acrobat Reader CD-ROM »Laser Technology« 5.0 on computers with Microsoft (German only) Windows 95 OSR 2.0, Windows 98 SE, Windows Millenium Edition, Windows This CD-ROM is a collection of graphics, NT 4.0 with Service Pack, Windows pictures and videos from the lectures 2000, Windows XP and MacOSX Laser Technology I and II by Prof. (64 MB Ram (random access memory) Dr. rer. nat. Reinhart Poprawe M.A. as well as 30 MB free fixed-disk storage). and a new revised version was produced in 2003. The printing and use of unaltered graphics and pictures is only allowed It was produced by the Department for educational purposes. for Laser Technology LLT in the machine faculty at the RWTH Aachen University Further information and order forms in close cooperation with the Fraun- for the CD-ROM »Laser Technology« hofer Institute for Laser Technology ILT. are available through the laser technology association AKL e.V., It contains the basics of laser technology Steinbachstraße 15, 52074 Aachen. as well as physical and technical processes for modern manufacturing pro- Contact cesses. Furthermore, the current state Diana Heinrichs of economic use of laser and industrial Phone +49 241 8906-122 applications is demonstrated in nume- Fax +49 241 8906-112 rous examples. [email protected]

154 Fraunhofer ILT Annual Report 2007 Technical Book »Laser Technology for Manufacturing«

Contents »Laser Technology for Manu- Introduction, behavior of electromag- facturing« by Reinhart Poprawe netic radiation at interfaces, absorption of laser radiation, energy transfer and Principles, prospects and examples thermal conduction, thermomechanics, for the innovative engineer. phase transformation, melting pool flows, laser-induced ablation, plasma Applied laser technology is too wide- physics, laser radiation sources, surface ranging a topic to be covered in a technologies, forming, rapid prototyp- single volume. For this reason, the ing, rapid tooling, joining, ablation and book places special emphasis on laser drilling, cutting, systems engineering, technology as used in manufacturing laser measuring technologies. applications, particularly present-day Appendices: A: optics, B: continuum machining processes used in produc- mechanics, C: laser-induced ablation, tion technology. The phenomena D: plasma physics, E: explanation occurring in laser-based materials proof symbols and constants, F: color cessing are quantified by formulae and images, index illustrated with corresponding models that are readily understood by the 2005. XVII, 526 pages, 353 illustrations trained engineer or physicist. These (VDI publication), ISBN 3-540-21406-2 basic principles enable the different types of machining operations to be The book can be ordered from: systematically characterized, permitting Springer Kundenservice the various applications to be illustra- Haberstraße 7 ted using a common scientific basis. 69126 Heidelberg Of more practical significance are the Telefon +49 6221 345-0 processes described for various machin- Fax +49 6221 345-4229 ing operations, which explain in simple [email protected] terms the basic principles and key www.springer.de quantitative interrelationships between the process parameters. The numerous examples are intended to spark the reader’s creativity and help to inspire new applications.

Fraunhofer ILT Annual Report 2007 155 Information Service

Sender If you would like more information Technical Brochure: »High-Power about the research and development Diode Lasers« at the Fraunhofer Institute for Laser German ______Technology please go to our website English Last Name, First Name at www.ilt.fraunhofer.de. Information ______can also be ordered using this form. Technical Brochure: »Lasertechnik Company für die Oberflächenmodifikation und das Umformen« (Laser Tech- ______Division Brochure: »Your partner nology for Surface Modification for innovation« and Forming) (only German) ______German Address English Technical Brochure: »Lasertechnik ______für den Verschleiß- und Korrosions- City/ZIP Brochure: »Services schutz« (Laser Technology for and Contacts« Wear and Corrosion Protection) ______Phone (German/English) (only German)

______Annual Report 2007 Technical Brochure: Fax (English version only available »Laserstrahlauftragschweißen« ______online at www.ilt.fraunhofer.de) (Laser Beam Deposition Welding) E-mail (only German) Annual Report 2006 (English version only available Technical Brochure: Please fax to: online at www.ilt.fraunhofer.de) »Rapid Prototyping and Rapid Fraunhofer ILT Manufacturing« Stefanie Flock Annual Report 2005 German Fax +49 241 8906-121 (English version only available English online at www.ilt.fraunhofer.de) Technical Brochure: Annual Report 2004 »Lasers in Microstructuring« (English version only available German online at www.ilt.fraunhofer.de) English

Proceedings of the Aachen Technical Brochure: Colloquium for Laser Technology »Abtragen, Reinigen und AKL’06 (only German) Markieren mit Laserstrahlung« (Laser Ablation, Cleaning and Proceedings of the Technology Marking) (only German) Business Day TBT’06 (only German) Technical Brochure: »Systems and Plant for Laser Materials Proceedings of the International Processing« (only German) Laser Technology Congress AKL’08 (only English) Technical Brochure: »Quality Assurance in Laser Materials Processing« German English

156 Fraunhofer ILT Annual Report 2007 Information Service

Technical Brochure: »Lasers Information Brochure: »Optische in Mounting and Connecting Technologien an der RWTH Techniques« Aachen« (Optical Technology German Courses at RWTH Aachen) English (only German)

Technical Brochure: »Lasers in Information Brochure: Polymer and Paper Technology« »Networks of Competence« German (German/English) English Information Brochure: Technical Brochure: »European Laser Institute ELI« »Lasers in Life Science« (only English) German English CD-Rom »Lasertechnik« (Laser Technology) (only German) Technical Brochure: »Modellie- rung und Simulation« (Modeling Technical Book »Lasertechnik für and Simulation) (only German) die Fertigung« (Laser Technology for Manufacturing) (only German) Technical Brochure: »Laser- mikroskopie« (Laser Microscopy) (only German)

Technical Brochure: »Polieren mit Laserstrahlung« (Polishing with Laser Radiation) (only German)

Technical Brochure: »Wärme- behandlung mit Laserstrahlung« (Heat Treatment with Laser Radiation) (only German)

Technical Brochure: »Material Analysis and Process Monitoring with Laser« German English

Technical Brochure: »Design of Diode Laser Heat Sinks« (only English)

Technical Brochure: »Customized Services for Diode Lasers« (only English)

Fraunhofer ILT Annual Report 2007 157 Imprint

Editorial staff Fraunhofer-Institut Dipl.-Phys. Axel Bauer (responsible) für Lasertechnik ILT Stefanie Flock Steinbachstraße 15 Design and Production 52074 Aachen Dipl.-Des. Andrea Croll Phone +49 241 8906-0 Fax +49 241 8906-121 Print Druckspektrum [email protected] Hirche-Kurth GbR, Aachen www.ilt.fraunhofer.de

Paper This Annual Report was printed on environment-friendly, unchlorinated and acid-free bleached paper.

Contact Dipl.-Phys. Axel Bauer Telephone +49 241 8906-194 Fax +49 241 8906-121 [email protected]

Subject to alterations in specifications and other technical information.