DOCSLIB.ORG

Lasers, Free-Electron

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lasers, Free-Electron 1 Lasers, Free-Electron Claudio Pellegrini and Sven Reiche • Q1 University of California, Los Angeles, CA 90095-1547, USA e-mail: [email protected]; [email protected] Abstract Free-electron lasers are radiation sources, based on the coherent emission of synchrotron radiation of relativistic electrons within an undulator or wiggler. The resonant radiation wavelength depends on the electron beam energy and can be tuned over the entire spectrum from micrometer to X-ray radiation. The emission level of free-electron lasers is several orders of magnitude larger than the emission level of spontaneous synchrotron radiation, because the interaction between the electron beam and the radiation field modulates the beam current with the periodicity of the resonant radiation wavelength. The high brightness and the spectral range of this kind of radiation source allows studying physical and chemical processes on a femtosecond scale with angstrom resolution. Keywords free-electron laser; undulator; microbunching; SASE FEL; FEL oscillator; FEL amplifier; FEL parameter; gain length. 1 Introduction 2 2 Physical and Technical Principles 5 2.1 Undulator Spontaneous Radiation 6 2.2 The FEL Amplification 7 2.3 The Small-signal Gain Regime 10 2.4 High-gain Regime and Electron Beam Requirement 11 2.5 Three-dimensional Effects 13 OE038 2 Lasers, Free-Electron 2.6 Longitudinal Effects, Starting from Noise 14 2.7 Storage Ring–based FEL Oscillators 16 3 Present Status 17 3.1 Single-pass Free-electron Lasers 17 3.2 Free-electron Laser Oscillators 18 4 Future Development 20 Glossary 21 References 23 Further Reading 24 1 accelerator and can be used to accelerate Introduction the electron beam to higher energies. The energy transfer can take place only A free-electron laser (FEL) [1] transforms if a condition of synchronism between the the kinetic energy of a relativistic electron wave and the beam oscillations is satisfied beam produced by a particle accelerator (Sect. 2.2). This condition gives a relation- like a microtron, storage ring, or radio ship between the radiation wavelength λ, • Q2 frequency (RF) linear accelerator into the electron beam velocity βz along the un- electromagnetic (EM) radiation. The trans- dulator axis (measured in units of the light formation occurs when the beam goes velocity c), and the undulator period λ0: through an alternating magnetic field, pro- λ (1 − β ) duced by a magnet called an undulator [2], λ = 0 z (1) that forces the electrons to move in an βz oscillatory trajectory about the axis of the For relativistic electrons, this condition can system, as shown in Fig. 1. An electromag- alsobewritteninanapproximate,but netic wave propagates together with the more convenient, form using the beam electron beam along the undulator axis, energy γ (measured in the rest energy and interacts with the electrons. units E = mc2γ ): The undulator magnet is a periodic structure in which the field alternates λ λ = 0 (1 + a2 ). (2) between positive and negative values and 2γ 2 w has zero average value. It produces an electron trajectory having a transverse The dimensionless quantity velocity component perpendicular to the eB0λ0 axis and parallel to the electric field of the aw = (3) 2πmc wave, thus allowing an energy exchange between the two to take place. One can is the undulator vector potential normal- either transfer energy from the beam to the ized to the electron rest mass mc2; e is the wave, in which case the device is an FEL, or electron charge and B0 is the undulator from the wave to the beam, in which case it peak magnetic field. (Here, and in the rest is an inverse FEL (IFEL) [3]. In the second ofthepaper,weuseMKSunits.)Thequan- case, the system is acting like a particle tity aw is called the undulator parameter, OE038 Lasers, Free-Electron 3 Undulator Electron Outcoupled beam field Optical cavity mirror Radiation field Partial mirror Fig. 1 Schematic representation of an FEL oscillator, showing its main component: the electron beam, undulator magnet, and optical cavity. The undulator shown is a permanent-magnet planar undulator. The arrows indicate the magnetic field direction. In an FEL amplifier of SASE FEL setup the optical cavity is omitted. The FEL amplifier is seeded by an external radiation field which is the normalized vector potential of fact suggests that high- to average-power the undulator field. The undulator can be FELs can be designed without the problem, of two types: helical and planar (Sect. 2). common in atomic and molecular lasers, Equation 2 is valid for a helical undulator. of heating the lasing medium. In the case of a planar undulator, Eq. 2 The time structure of the laser beam is still valid if we replace the undulator√ mirrors that of the electron beam. De- parameter with its rms value aw/ 2. pending on the accelerator used, one can Because of the dependence of the radi- design systems that are continuous-wave ation wavelength on the undulator period, (cw) or with pulses as short as picoseconds magnetic field, and electron-beam en- or subpicoseconds. ergy – quantities that can be easily and Tunability, high efficiency, and time continuously changed – the FEL is a tun- structure make the FEL a very attractive able device that can be operated over a source of coherent EM power. In some very large frequency range. At present, the wavelength regions, like the X-ray, the range extends from the microwave to the FEL is unique. Its applications range from UV [4]. A new FEL is now under construc- purely scientific research in physics, chem- tion in the United States [5] to reach the istry, and biology to military, medical, and X-ray region, about 0.1 nm. A similar pro- industrial applications. gram is being developed in Germany [6], FELs originate in the work carried out and other FEL to cover the intermediate in the 1950s and 1960s on the generation region between 0.1 nm and the UV [7] are of coherent EM radiation from electron also being considered by several countries. beams in the microwave region [2, 8]. The efficiency of the energy transfer As scientists tried to push power sources from the beam kinetic energy to the EM to shorter and shorter wavelengths, it wave is between 0.1 to a few percent for became apparent that the efficiency of most FELs, but it can be quite large, up to the microwave tubes, and the power about 40%, for specially designed systems. they produced, dropped rapidly in the The beam energy not transferred to the millimeter region. It was then realized that EM wave remains in the beam and can this problem could be overcome by using be easily taken out of the system, to be an undulator magnet to modify the beam disposed of, or recovered elsewhere. This trajectory [1], making it possible for the OE038 4 Lasers, Free-Electron beam to interact with a wave, away from 1. portions of the EM spectrum, like the any metallic boundary. Two pioneering far infrared (FIR), or the soft and experiments at the Stanford University [9, hard X-ray region, where atomic or 10] proved that the FEL is a useful source molecular lasers are not available or of coherent radiation. are limited in power and tunability; The current disadvantage of FELs is the 2. large-average power, high-efficiency greater complexity and cost associated with system. the use of a particle accelerator. For this reason, the use and development of FELs An order-of-magnitude comparison of are mainly oriented to the following: the peak brightness obtained or expected 1035 TESLA SASE FELs 1033 DESY TTF-FEL LCLS (seeded) 1031 Spontaneous spectrum SASE FEL 1 0.1% bandw.)] 29 DESY 2 10 TTF-FEL 30 GeV mm 15 GeV 2 Spontaneous spectrum TESLA SASE FEL 4 spontaneous undulator 1027 SPring8 undulator 25 10 (30m in vacuum) ESRF-undulator TTF-FEL (ID23) spontan 1023 Peak brilliance [Phot./(sec mrad Peak BESSY-II APS U-49 undulator BESSY-II (Typ A) 21 U-125 10 PETRA undulator ALS U5.0 1019 101 102 103 104 105 106 Energy (eV) Fig. 2 Peak brightness of free-electron lasers in the VUV and X-ray regime, compared to 3rd generation light sources [11] OE038 Lasers, Free-Electron 5 for the FEL, compared to other sources of The accelerators used to provide the elec- EM radiation, is given in Fig. 2, pointing tron beam are of many types: electrostatic, out again the interest for FELs in the soft- induction line, radio-frequency (rf) linear to-hard X-ray regions. accelerator, pulsed diode, or storage rings. In Sect. 2 of this article, we discuss Some of their basic characteristics, their the general physical principles of FELs energy ranges, and the FEL wavelengths and the properties and characteristics of for which they are more commonly used their main components, that is, the un- are given in Table 1. dulator magnets, electron beams, and Undulator magnets are of two main optical systems. We also describe the types: helical or planar. In the first case, main properties of the spontaneous ra- the magnetic field vector rotates around diation from an undulator, the process the axis as a function of axial distance; leading to the amplification of radia- in the second case, its direction is fixed, tion, the high-gain and small-signal-gain and its amplitude oscillates along the axis. regimes, diffraction effects, saturation These magnets can be, and have been, effects, the limits on the system effi- built using a wide variety of technologies: ciency, the dependence of gain on beam pulsed or DC electromagnets, permanent parameters. magnets, and superconducting magnets. In Sect.
Load more

Recommended publications
  • 020-101363-04 LIT MAN USER CP42LH.Book
    User Manual 020-101363-04 CP42LH NOTICES COPYRIGHT AND TRADEMARKS Copyright © 2019 Christie Digital Systems USA Inc. All rights reserved. All brand names and product names are trademarks, registered trademarks or trade names of their respective holders. GENERAL Every effort has been made to ensure accuracy, however in some cases changes in the products or availability could occur which may not be reflected in this document. Christie reserves the right to make changes to specifications at any time without notice. Performance specifications are typical, but may vary depending on conditions beyond Christie's control such as maintenance of the product in proper working conditions. Performance specifications are based on information available at the time of printing. Christie makes no warranty of any kind with regard to this material, including, but not limited to, implied warranties of fitness for a particular purpose. Christie will not be liable for errors contained herein or for incidental or consequential damages in connection with the performance or use of this material. Canadian manufacturing facility is ISO 9001 and 14001 certified. WARRANTY Products are warranted under Christie’s standard limited warranty, the complete details of which are available by contacting your Christie dealer or Christie. In addition to the other limitations that may be specified in Christie’s standard limited warranty and, to the extent relevant or applicable to your product, the warranty does not cover: a. Problems or damage occurring during shipment, in either direction. b. Projector lamps (See Christie’s separate lamp program policy). c. Problems or damage caused by use of a projector lamp beyond the recommended lamp life, or use of a lamp other than a Christie lamp supplied by Christie or an authorized distributor of Christie lamps.
    [Show full text]
  • FEL Physics Summary
    VUV and X-Ray Free Electron Lasers: The Technology and Its Scientific Promise William Barletta and Carlo Rizzuto Sections I & III – Motivations & FEL Physics List of symbols fine structure constant dimensionless vector potential aw horizontal Twiss x bunching parameter b mean resolution error of BPMs BPMres position error of BPMs BPMpos remanent field BR undulator magnetic field strength Bw horizontal Twiss x speed of light c mean phase error in undulator penetration depth δp horizontal dispersion Dx derivative of Dx D´x FEL beam diameter on optic Dw energy chirp from CSR E/E beam emittance electron charge e beam energy E peak electric field in gun Eo normalized emittance n energy in the FEL pulse EPulse longitudinal space charge force Fsc angle of incidence j i 1 2 relativistic factor (E/ me c ) optical function in transport H magnetic coercivity HC Alfven current at =1 IAo beam current Ib BBU threshold current IBBU undulator parameter K mean undulator strength Krms undulator spatial frequency kw gain length LG th m harmonic wavelength m plasma wavelength P radiation wavelength r undulator wavelength w root of gain equation harmonic number m electron mass me number of electrons Ne electron density ne number of undulator periods Nu radiation power P input laser power Plaser noise power Pn pole roll angle error BNP (or Pierce) parameter quantum FEL parameter ´ atom density A quality factor Q dipole quality factor Qdipole FEL energy constraint ratio r1 FEL emittance constraint ratio r2 FEL diffraction constraint ratio r3 classical radius of electron re bend angle in undulator bend angle in achromat 2 th phase of i electron i kick relative to each pole error j mean energy spread of electrons e bunch length z relativistic plasma frequency p distance along undulator z mean longitudinal velocity <vz> impedance of free space Zo Rayleigh range ZR 3 I.
    [Show full text]
  • Bilateral NIST-PTB Comparison of Spectral Responsivity in the VUV
    Bilateral NIST-PTB Comparison of Spectral Responsivity in the VUV A Gottwald 1, M Richter 1, P-S Shaw 2, Z Li 2 and U Arp 2 1Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin, Germany 2National Institute for Standards and Technology, 100 Bureau Dr., Gaithersburg, MD 20899-8410, U.S.A. E-mail: [email protected] Abstract. To compare the calibration capabilities for the spectral responsivity in the vacuum-ultraviolet spectral region between 135 nm and 250 nm, PTB and NIST agreed on a bilateral comparison. Calibrations of semiconductor photodiodes as transfer detectors were performed using monochromatized synchrotron radiation and cryogenic electrical substitution radiometers as primary detector standards. Great importance was attached to the selection of suitable transfer detector standards due to their critical issues in that wavelength regime. The uncertainty budgets were evaluated in detail. The comparison showed a reasonable agreement between the participants. However, it got obvious that the uncertainty level for this comparison cannot easily be further reduced due to the lack of sufficiently radiation-hard and long-term stable transfer standard detectors. Keywords: PACS: 07.60.Dq, 07.85.Qe, 85.60.Dw, 06.20.fb Bilateral NIST-PTB Comparison of Spectral Responsivity in the VUV 2 1. Introduction The last decade has seen numerous key comparisons in the field of photometry and radiometry between different national metrology institutes (NMIs) in the context of the Mutual Recognition Arrangement. At first, these comparisons were restricted to wavelengths longer than 200 nm, with just the exception of a recent pilot comparison from 10 nm to 20 nm [1].
    [Show full text]
  • Pulsed/Cw Nuclear Magnetic Resonance
    PULSED/CW NUCLEAR MAGNETIC RESONANCE “The Second Generation of TeachSpin’s Classic” • Explore NMR for both Hydrogen (at 21 MHz) and Fluorine Nuclei • Magnetic Field Stabilized to 1 part in 2 million • Homogenize Magnetic Field with Electronic Shim Coils • Quadrature Phase-Sensitive Detection with 1° Phase Resolution • Direct Measurement of Spin-Spin and Spin-Lattice Relaxation Times • Carr-Purcell and Meiboom-Gill Pulse Sequences • Observe Chemical Shifts in both Hydrogen and Fluorine Liquids • Compare Pulsed and Continuous Wave NMR Detection • Study Pulsed and CW NMR in Solids • Built-in Lock-In Detection and Magnetic Field Sweeps Instruments Designed For Teaching PULSED/CW NUCLEAR MAGNETIC RESONANCE The 21 MHz Digital Synthesizer produces rf power in both INTRODUCTION pulsed and cw formats. There is sufficient rf power to produce Nuclear Magnetic Resonance has been an important research a π/2 pulse in about 2.5 microseconds. It also produces the tool for physics, chemistry, biology, and medicine since its discov- reference signals (in 1° phase steps) for the quadrature detectors. ery simultaneously by E. Purcell and F. Bloch in 1946. In the The Pulse Programmer digitally creates the pulsed sequences of 1970’s, pulsed NMR became the dominant paradigm for reasons various pulse lengths, number of pulses, time between pulses, and your students will discover using the apparatus described in this repetition times. The Lock-In/Field Sweep provides a wide range brochure, TeachSpin’s second generation of our classic PS1-A&B. of magnetic field sweeps, as well as a lock-in detection system for This new unit was designed in response to requests for additional examining weak cw NMR signals from solids.
    [Show full text]
  • Absorption and Wavelength Modulation Spectroscopy of NO2 Using a Tunable, External Cavity Continuous Wave Quantum Cascade Laser
    Absorption and wavelength modulation spectroscopy of NO2 using a tunable, external cavity continuous wave quantum cascade laser Andreas Karpf* and Gottipaty N. Rao Department of Physics, Adelphi University, Garden City, New York 11530, USA *Corresponding author: [email protected] Received 16 September 2008; revised 5 December 2008; accepted 9 December 2008; posted 10 December 2008 (Doc. ID 101685); published 9 January 2009 The absorption spectra and wavelength modulation spectroscopy (WMS) of NO2 using a tunable, external cavity CW quantum cascade laser operating at room temperature in the region of 1625 to 1645 cm−1 are reported. The external cavity quantum cascade laser enabled us to record continuous absorption spectra −1 of low concentrations of NO2 over a broad range (∼16 cm ), demonstrating the potential for simulta- neously recording the complex spectra of multiple species. This capability allows the identification of a particular species of interest with high sensitivity and selectivity. The measured spectra are in excellent agreement with the spectra from the high-resolution transmission molecular absorption database [J. Quant. Spectrosc. Radiat. Transfer 96, 139–204 (2005)]. We also conduct WMS for the first time using an external cavity quantum cascade laser, a technique that enhances the sensitivity of detection. By employing WMS, we could detect low-intensity absorption lines, which are not visible in the simple ab- sorption spectra, and demonstrate a minimum detection limit at the 100 ppb level with a short-path ab- sorption cell. Details of the tunable, external cavity quantum cascade laser system and its performance are discussed. © 2009 Optical Society of America OCIS codes: 000.2170, 010.1120, 120.6200, 280.3420, 300.1030, 300.6340.
    [Show full text]
  • Collimation System for the Bessy Fel∗
    T. Kamps / Proceedings of the 2004 FEL Conference, 381-384 381 COLLIMATION SYSTEM FOR THE BESSY FEL∗ T. Kamps Berliner Elektronenspeicherring-Gesellschaft fur¨ Synchrotronstrahlung BESSY, D-12489 Berlin, Germany Abstract magnet undulators. Each undulator is composed of mod- ules with length ranging from 1.6 m to 3.9 m, the total Beam collimation is an essential element for the success- length of the high energy FEL line is 70 m. A FODO lat- ful running of a linear accelerator based free electron laser. tice is superimposed onto the undulator structure with the The task of the collimation system is to protect the undu- quadrupole magnets located at the intersections between lator modules against mis-steered beam and dark-current. the undulator modules. For the present analysis in total 14 This is achieved by a set of apertures limiting the succeed- undulator modules are taken into account for the simulation ing transverse phase space volume and magnetic dogleg studies. The gap between the undulator poles is 10 mm, the structure for the longitudinal phase space. In the follow- beampipe radius is 4 mm. The undulator magnets are made ing the design of the BESSY FEL collimation system is of NdFeB in order to obtain large undulator K parameters. described together with detailed simulation studies. This material is very sensitive to irradiation, especially to the reduced dose deposited by high-energy electrons (> MOTIVATION 20 MeV). From studies with NdFeB under electron irra- Experiences from linac driven FEL operation (for exam- diation [4] the limit for acceptable beam loss in the undula- ple at TTF1 [1]) indicate that beam collimation is essential tor chamber has been derived.
    [Show full text]
  • The Diamond Light Source
    The Diamond Light Source ... a bright future for UK and World science Richard P. Walker, Technical Director What is Diamond ? • The largest scientific investment in the UK for 30 years • A synchrotron light source producing pinpoint UV and X-ray light beams of exceptional brightness • A ‘super microscope’ for new research opportunities into the structure and properties of matter What is Diamond ? • A Power Converter ! 15 MW of electrical power from the grid … 300-500 kW of X-rays … … but most of which only produces unwanted heat; only a fraction is selected for use in experiments. What is Synchrotron Radiation ? SR is electromagnetic radiation emitted when a high energy beam of charged particles (electrons) is deflected by a magnetic field. What’s so special about Synchrotron Radiation ? SR SR is emitted over a wide range of the electromagnetic spectrum, from Infra-red to hard X-rays Any desired radiation wavelength can be produced - enabling a very wide range of scientific and technological applications What’s so special about Synchrotron Radiation ? SR is very intense, and has extremely high brightness (emitted from a small area, with small angular divergence, determined by the properties of the electron beam) High brightness means: - it can be focused to sub-micron spot sizes: possibility of examining extremely small samples or investigating the structure and properties of objects with very fine spatial resolution - experiments can be carried out much more quickly: high through-put of samples or ability to follow chemical and biological reactions in real-time Diamond is a “third-generation” synchrotron radiation source • 1st generation: machines originally built for other purposes e.g.
    [Show full text]
  • Time-Synchronized Continuous Wave Laser-Induced Fluorescence on An
    Time-synchronized continuous wave laser- induced fluorescence on an oscillatory xenon discharge Cite as: Rev. Sci. Instrum. 83, 113506 (2012); https://doi.org/10.1063/1.4766958 Submitted: 07 August 2012 . Accepted: 26 October 2012 . Published Online: 27 November 2012 N. A. MacDonald, M. A. Cappelli, and W. A. Hargus ARTICLES YOU MAY BE INTERESTED IN Time-resolved laser-induced fluorescence measurement of ion and neutral dynamics in a Hall thruster during ionization oscillations Journal of Applied Physics 118, 233301 (2015); https://doi.org/10.1063/1.4937272 Ion dynamics in an E × B Hall plasma accelerator Applied Physics Letters 106, 044102 (2015); https://doi.org/10.1063/1.4907283 Tutorial: Physics and modeling of Hall thrusters Journal of Applied Physics 121, 011101 (2017); https://doi.org/10.1063/1.4972269 Rev. Sci. Instrum. 83, 113506 (2012); https://doi.org/10.1063/1.4766958 83, 113506 © 2012 American Institute of Physics. REVIEW OF SCIENTIFIC INSTRUMENTS 83, 113506 (2012) Time-synchronized continuous wave laser-induced fluorescence on an oscillatory xenon discharge N. A. MacDonald,1,a) M. A. Cappelli,1 and W. A. Hargus, Jr.2 1Stanford Plasma Physics Laboratory, Stanford University, Stanford, California 94305, USA 2Air Force Research Laboratory, Edwards AFB, California 93524, USA (Received 7 August 2012; accepted 26 October 2012; published online 27 November 2012) A novel approach to time-synchronizing laser-induced fluorescence measurements to an oscillating current in a 60 Hz xenon discharge lamp using a continuous wave laser is presented. A sample-hold circuit is implemented to separate out signals at different phases along a current cycle, and is followed by a lock-in amplifier to pull out the resulting time-synchronized fluorescence trace from the large background signal.
    [Show full text]
  • The Tesla Free Electron Laser J
    THE TESLA FREE ELECTRON LASER J. Rossbach, for the TESLA FEL collaboration DESY, Notkestrasse 85, D22603 Hamburg, Germany Abstract occupied many scientists, a practical solution to this prob- lem has not yet been realized. To be an efficient research The TESLA Free Electron Laser (FEL) makes use of the tool, such a source would have to provide stable intensities high electron beam quality that can be provided by the su- with short pulses and repetition frequencies similar to what perconducting TESLA linac to drive a single pass FEL at is found in optical lasers. Exactly this seems to be possible wavelengths far below the visible. To reach a wavelength by using the so-called self amplified spontaneous emission of 6 nanometers, the TESLA Test Facility (TTF) currently process SASE. under construction at DESY will be extended to 1 GeV The basic principle [1] makes use of the fact that an elec- beam energy. Because there are no mirrors and seed-lasers tron beam of sufficient quality, passing a long undulator in this wavelength regime, the principle of Self-Amplified- magnet, exponentially amplifies an initially existing radi- Spontaneous-Emission (SASE) will be employed. A first ation field, if the photon wavelength λph matches a reso- test of both the principle and technical components is fore- nance condition determined by undulator parameters and seen at a photon wavelength larger than 42 nanometers. the beam energy: With respect to linac technology, the key prerequisite for such single-pass, high-gain FELs is a high intensity, λu 2 λph = (1 + K ) (1) diffraction limited, electron beam to be generated and ac- 2γ2 celerated without degradation.
    [Show full text]
  • Biomaterials
    BIOMATERIALS Research in the Department of Biomaterials The Department of Biomaterials focuses on interdisci- New Methods for Analysis of Biomaterials plinary research in the field of biological and bio- Studying hierarchical biomaterials requires state-of-the-art mimetic materials. The emphasis is on under- experimental equipment, but there is also some need for the standing how the mechanical or other physical development of new approaches. Scanning methods based properties are governed by structure and compo- on the diffraction of synchrotron radiation, as well as the sition (see Fig. 1). Furthermore, research on nat- technique of small-angle x-ray scattering (SAXS) are continu- ural materials (such as bone or wood) has poten- ously developed to improve the characterization of hierarchi- tial applications in many fields. First, design con- cal biomaterials. Further technical improvement is expected cepts for new materials may be improved by from a dedicated scanning set-up which is currently being learning from Nature. Second, the understanding installed at the synchrotron BESSY in Berlin. of basic mechanisms by which the structure of bone or connective tissue is optimised opens the way for Plant Biomechanics Biotemplating studying diseases and, thus, for contributing to diagnosis (Ingo Burgert) (Oskar Paris) and development of treatment strategies. A third option is to use structures grown by Nature and transform them by phys- Mechanobiology Biomimetic Materials ical or chemical treatment into technically relevant materials (Richard Weinkamer) (Peter Fratzl) (biotemplating). Given the complexity of natural materials, new approaches for structural characterisation are needed. Mineralized Tissues Bone Research Some of these are further developed in the Department, in (Himadri S.
    [Show full text]
  • Laser Measurement in Medical Laser Service
    Laser Measurement in Medical Laser Service By Dan Little, Technical Director, Laser Training Institute, Professional Medical Education Association, Inc. The global medical industry incorporates thousands of lasers into its arsenal of treatment tools. Wavelengths from UV to Far-Infrared are used for everything from Lasik eye surgery to cosmetic skin resurfacing. Visible wavelengths are used in dermatology and ophthalmology to target selective complementary color chromophores. Laser powers and energies are delivered through a wide range of fiber diameters, articulated arms, focusing handpieces, scanners, micromanipulators, and more. With all these variables, medical laser service personnel are faced with multiple measurement obstacles. At the Laser Training Institute (http://www.lasertraining.org), with headquarters in Columbus Ohio, we offer a week-long laser service school to medical service personnel. Four times a year, a new class learns the fundamental concepts of power and energy densities, absorption, optics, and, most of all, how lasers work. With a nice sampling of all the major types of medical lasers, the students learn hands-on calibration, alignment, and multiple service skills. Lasers used in the medical field fall under stricter safety regulations than other laser usages. Meeting ANSI compliances are critical to the continued legal operation of all medical and aesthetic facilities. Laser output powers and energies are to be checked on a semi-annual basis according to FDA Regulations and are supported by ANSI recommendations which state regular scheduled intervals. In our service school we exclusively use Ophir-Spiricon laser measurement Instrumentation. We present a graphically enhanced presentation on measurement technologies and the many, varying, critical parameters that are faced with not only each different type of laser but design differences between manufacturers.
    [Show full text]
  • Dynamics of Passively Coupled Continuous-Wave and Mode
    Dynamics of Passively Coupled Continuous-Wave and Mode-Locked Lasers by Sudarshan Sivaramakrishnan A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Electrical Engineering) in The University of Michigan 2017 Doctoral Committee: Professor Herbert G. Winful, Chair Professor Almantas Galvanauskas Professor Peter D. Miller Professor Kim A. Winick Sudarshan Sivaramakrishnan [email protected] ORCID iD: 0000-0002-6224-2094 © Sudarshan Sivaramakrishnan 2017 DEDICATION To my parents and to my younger brother ii ACKNOWLEDGMENTS My PhD journey has been deeply enriching and enlightening, as well as the most challenging endeavor that I have ever undertaken. As such, I am grateful to all involved for the motivation, support, and engagement that made graduate life as fulfilling and fun of an experience as it was. First and foremost, I would like to thank my research advisor, Professor Herbert Winful, for his dedication, patience, and enthusiasm to help me successfully complete my PhD. It has been a privilege to work with and learn from him across a diverse array of fascinating topics, and I am indebted to him for aiding my growth as a researcher and as an individual. From my first meeting with him (an advising appointment when I was an undergraduate freshman declaring my major in Electrical Engineering) to joining his research group in the summer before graduate school to the present, he has been a persistent source of wisdom, encouragement, and equanimity. His thoughtful guidance has enabled me to explore new scientific problems and steer my own path through the research process, while time and again his friendly smiles and ever-positive outlook replenished my belief in the value of my work whenever I lost my way.
    [Show full text]