DOCSLIB.ORG

Excimer Lasers—40 Never Looked Better

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Excimer Lasers—40 Never Looked Better GAS LASERS Excimer lasers—40 never looked better LUDOLF HERBST Despite its middle-aged standing small features at extremely 20 Hz—now, numerous excimer lasers in the laser community, the excimer high precision, based on the support multi-kilohertz repetition rates laser is a high-power source of UV fact that optical resolution (see Fig. 1). Just as important, laser pro- scales down directly with ducers have also substantially improved and DUV light with no equal in wavelength because of dif- the service characteristics and total cost certain critical applications. fraction. High pulse energy of ownership of excimer lasers to keep The first commercial excimer laser was combined with rapid repetition rate en- them competitive with other laser and introduced 40 years ago by Lambda ables high process throughput and re- non-laser technologies. Physik (now Coherent; Santa Clara, duces takt time (the total time it takes CA). Interestingly, its developers— to produce a single unit of a product). Vision correction Bernd Steyer and Dirk Basting—were While solid-state UV laser technolo- Every year, more than a million people both chemists whose main goal was gies have advanced tremendously over worldwide undergo LASIK surgery to to develop a light source for photo- the past 40 years, no new technology achieve perfect vision—dramatically chemistry and dye laser pumping. As has arisen to challenge the excimer la- improving the quality of life for count- soon as excimer lasers entered the mar- ser in delivering this particular combi- less individuals (see Fig. 2). ket, Lambda Physik began to investi- nation of characteristics. Introduced in 1989, LASIK was the gate other possible uses for a powerful From a practical standpoint, excimer first major non-scientific application source of short ultraviolet (UV) light. lasers have expanded their relevance in for excimer lasers and still remains the While most of the original applica- the market because of extensive efforts largest single excimer laser application tions for excimers can largely be relegat- by manufacturers to improve their out- in terms of unit volume. What start- ed to history, many others have evolved. put characteristics and tailor them to the ed with crude experiments on pig eyes It is fair to say that few other laser tech- needs of specific applications. For ex- has now evolved to more than 10,000 nologies have had a greater impact on ample, the first commercial excimer la- high-precision, compact, tabletop la- our daily life than excimers. Laser- ser, the Lambda Physik EMG 500, op- sers deployed worldwide at eye clinics assisted in situ keratomileusis (LASIK), erated at a maximum repetition rate of and LASIK centers. photolithography, and display In the LASIK procedure, ex- production are three primary cimer laser pulses at 193 nm are applications that illustrate the used to ablate material from unique properties of the exci- the human cornea to reshape mer laser that continue to en- it, thus changing its refractive sure its legacy as a key enabling power and allowing correction technology. for short- or long-sightedness and astigmatism. Unique output, To perform LASIK, a thin, unique benefits hinged flap is surgically lifted Excimer lasers offer a unique combination of UV wave- FIGURE 1. The first commercial length output together with excimer laser was the Lambda high pulse energy—attributes Physik EMG 500, which produced a that are key to their expand- pulse energy of 220 mJ at 248 nm, ing use. The short wavelength with a repetition rate up to 20 Hz. enables the production of very 46 November 2017 www.laserfocusworld.com Laser Focus World 1711lfw_46 46 10/25/17 1:22 PM (by a femtosecond laser demands of the chip industry. As a result, or microkeratome) from oscillator/amplifier configurations with the outer surface of the high power (around 100 W) and outstand- cornea. The excimer ing performance characteristics are now laser beam is shaped the standard for this application. and projected using Active spectral narrowing (to much less fast-scanning mirrors, than 1 pm) and sophisticated dose and ablating corneal mate- linewidth control are widely utilized. And rial in the precise pat- while other technologies, such as extreme tern required to correct ultraviolet (EUV) lithography at 13 nm the individual patient’s will complement the excimer laser for the vision. The flap is then most critical layers at 10 nm, the future replaced, sealing and of the excimer laser still looks bright for protecting the front of photolithography applications. the eye. FIGURE 2. The LASIK procedure improves the quality of life for The precision of the more than a million people every single year. Display production 193 nm argon fluoride The two most common flat-panel display (ArF) excimer laser ablation process is (again, because of diffraction)—specifi- types for smartphones and other devic- essential for the predictability and safety cally, excimer lasers. es are active-matrix liquid-crystal dis- of the LASIK procedure. Plus, the short Both 248 and 193 nm lasers are used plays (AMLCDs) and active-matrix or- (nanosecond) pulse width and short wave- for photolithography. In particular, 193 ganic light-emitting diode (AMOLED) length remove corneal material in a rela- nm excimer lasers enable circuit pattern displays. Both of these use a backplane tively cold process called photoablation. features down to 10 nm, which is far be- consisting of a glass substrate on which low the diffraction limit. Achieving this a large number of thin-film transistors Photolithography necessitated the development of highly (TFTs) are patterned to form the actu- Excimer lasers are also essential to the fab- specialized excimers with grating-con- al pixel circuitry. The thin film is made rication of highly miniaturized integrated trolled line narrowing to minimize chro- of silicon (typically 50 nm thick) and ex- circuits (ICs). And, the availability of ev- matic aberrations in the imaging optics. posed using photolithography to yield the er-smaller, more powerful and, economi- A variety of other techniques, including desired circuit structures. cal microprocessors has in turn had a pro- immersion imaging, double or quadru- Large-scale chemical vapor deposi- found impact on modern society. ple exposures, and a range of clever op- tion (CVD) is used to create the amor- An IC itself consists of numerous elec- tical imaging methods, are used to pro- phous silicon (a-Si) layer. Converting this tronic components constructed on a single, duce even finer features. amorphous layer to polycrystalline sili- monolithic semiconductor wafer. The de- Over the last 25 years, companies in- con (poly-Si) improves the electron mo- tailed structure of these devices is built up cluding Cymer (San Diego, CA), an ASML bility, enabling small TFTs with excel- layer by layer in a process called photoli- company, and Gigaphoton (Oyama-shi, lent electrical characteristics that block thography, with the first step being to coat Japan) have made substantial advanc- less of the backlight, leading to brighter a semiconductor wafer with a light-sen- es in excimer technology tailored for li- displays that draw less power—particu- sitive photoresist. A reticle (mask) con- thography to keep pace with the relentless larly critical for small, high-resolution dis- taining the desired circuit pattern is il- plays. Moreover, the transition to OLED luminated with UV laser light and the Excimer laser technology comprised of emissive pixels mask pattern is projected onto the wa- line beam without a backlight sets high demands on fer surface, after which the exposed re- TFT performance. a-Si sist is developed and the wafer is chemi- Poly-Si The a-Si layer is transformed into po- cally etched to physically remove material ly-Si by heating it with the excimer laser from the exposed areas to produce the ac- in a process called excimer laser anneal- tual features. This process is then repeat- ing (ELA; see Fig. 3). Specifically, a pulsed Substrate ed as many as 30 or 40 times to produce excimer laser line beam is scanned over the entire circuit structure. Translation the a-Si film, which efficiently absorbs the The original photolithography light 308 nm excimer output. sources were mercury lamps, but the need FIGURE 3. A diagram shows the basic This high absorption, combined with to produce smaller features drove manu- elements of the excimer laser annealing (ELA) the high pulse energy of the excimer laser, facturers to shorter-wavelength sources process for display substrates. makes it possible to achieve near-complete Laser Focus World www.laserfocusworld.com November 2017 47 1711lfw_47 47 10/25/17 1:22 PM GAS LASERS continued melt of the thin silicon layer with each of the panel. This allows the entire panel pioneer for ELA. The success of this pulse. The high absorption of the sili- to be processed in one (or two, respective- application is based on considerable con also prevents the UV light from pen- ly) passes under the laser beam, which is advances in high-power excimer laser etrating significantly into the substrate, critical to achieving the necessary process technology and the UV optical system avoiding thermal stress and permitting utilization and high throughput. that provides the line beam homogene- the use of economical glass materials for For 20 years, Coherent (and, be- ity required for uniform annealing of the substrate. fore that, Lambda Physik) has been the ever-larger panels (see Fig. 4). Production oc- The processing capabilities of exci- curs on large glass mer lasers, together with ongoing im- panels, such as Gen provements in their performance, reli- 6 (1.5 × 1.8 m), that ability, and cost of ownership, continues are subsequently to make them a critical enabling tech- separated into nu- nology in many other industrial, medi- merous smaller dis- cal, and scientific processes.
Load more

Recommended publications
  • Advanced Excimer Laser Technologies Enable Green Semiconductor Manufacturing
    PROCEEDINGS OF SPIE SPIEDigitalLibrary.org/conference-proceedings-of-spie Advanced excimer laser technologies enable green semiconductor manufacturing Hitomi Fukuda, Youngsun Yoo, Yuji Minegishi, Naoto Hisanaga, Tatsuo Enami Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 10/25/2017 Terms of Use: https://spiedigitallibrary.spie.org/ss/TermsOfUse.aspx Advanced Excimer Laser Technologies Enable Green Semiconductor Manufacturing Hitomi Fukuda*, Youngsun Yoo, Yuji Minegishi, Naoto Hisanaga and Tatsuo Enami Gigaphoton Inc., 400 Yokokura-Shinden, Oyama-shi, Tochigi, JAPAN 323-8558 ABSTRACT "Green" has fast become an important and pervasive topic throughout many industries worldwide. Many companies, especially in the manufacturing industries, have taken steps to integrate green initiatives into their high-level corporate strategies. Governments have also been active in implementing various initiatives designed to increase corporate responsibility and accountability towards environmental issues. In the semiconductor manufacturing industry, there are growing concerns over future environmental impact as enormous fabs expand and new generation of equipments become larger and more powerful. To address these concerns, Gigaphoton has implemented various green initiatives for many years under the EcoPhoton™ program. The objective of this program is to drive innovations in technology and services that enable manufacturers to significantly reduce both the financial and environmental “green cost” of laser operations in high-volume manufacturing environment (HVM) – primarily focusing on electricity, gas and heat management costs. One example of such innovation is Gigaphoton’s Injection-Lock system, which reduces electricity and gas utilization costs of the laser by up to 50%. Furthermore, to support the industry’s transition from 300mm to the next generation 450mm wafers, technologies are being developed to create lasers that offer double the output power from 60W to 120W, but reducing electricity and gas consumption by another 50%.
    [Show full text]
  • I. Excimer Fluorescence, II. Heavy-Atom Spin-Orbital Coupling Effect and Iii. the Electronic Spectra of Ferrocene." (1965)
    Louisiana State University LSU Digital Commons LSU Historical Dissertations and Theses Graduate School 1965 Studies in Molecular Spectroscopy; I. Excimer Fluorescence, II. Heavy-Atom Spin-Orbital Coupling Effect and IIi. The lecE tronic Spectra of Ferrocene. Fred Jewel Smith Louisiana State University and Agricultural & Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses Recommended Citation Smith, Fred Jewel, "Studies in Molecular Spectroscopy; I. Excimer Fluorescence, II. Heavy-Atom Spin-Orbital Coupling Effect and IIi. The Electronic Spectra of Ferrocene." (1965). LSU Historical Dissertations and Theses. 1092. https://digitalcommons.lsu.edu/gradschool_disstheses/1092 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. This dissertation has bssn microfilmed exactly as received 6 6 -7 4 8 SMITH, Fred Jewel, 1939- STUDIES IN MOLECULAR SPECTROSCOPY} I. EXCIMER FLUORESCENCE, II. HEAVY- ATOM SPIN-ORBITAL COUPLING EFFECT AND HI. THE ELECTRONIC SPECTRA OF FERROCENE. Louisiana State University, Ph.D., 1965 Chemistry, physical University Microfilms, Inc., Ann Arbor, Michigan STUDIES IN MOLECULAR SPECTROSCOPY; I. EXCIMER FLUORESCENCE, II. HEAVY-ATOM SPIN-ORBITAL COUPLING EFFECT AND III . THE ELECTRONIC SPECTRA OF FERROCENE A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Chemistry by Fred Jewel Smith B.A., University of Southern Mississippi, 1960 August, 1965 ACKNOWLEDGMENT The author wishes to express his sincere appreciation to Dr.
    [Show full text]
  • 6 5 • Vacuum Ultraviolet Ar Excimer Emission Initiated by High Intensity Laser Produced Electrons
    JP0050803 JAERI-Cont" 2000-006 6 5 • Vacuum Ultraviolet Ar Excimer Emission Initiated by High Intensity Laser Produced Electrons Shoichi Kubodera and Wataru Sasaki Department of Electrical and Electronic Engineering and Photon Science Center, Miyazaki University Gakuen Kibanadai Nishi 1-1, Miyazaki, 889-2192 Japan We have observed Ar2* emission using a tabletop femtosecond high intensity laser as an excitation source. High intensity laser produced electrons via an optical field induced ionization (OFI) process initiated the Ar2* production kinetics, which made themselves analogous to those produced in an electron beam produced plasma. A fast conductive cooling of the OFI plasma was found to be appropriate to initiate the excimer formation kinetics more efficiently. Keywords: Vacuum ultraviolet, Excimer molecule, Short pulse laser, Conductive cooling There have been considerable demands for the development of compact short wavelength lasers in the vacuum ultraviolet (VUV) spectral region. Such compact short wavelength lasers would be applicable to various scientific and industrial fields, such as photochemistry, biological science, and new types of materials processing. Currently available practical compact VUV lasers are the ArF excimer laser at 193 tun and the F2 laser at 157 run, both of which are excited by a compact discharge device. Recently more attention is paid to short wavelength lasers in the VUV in the future optical lithography industry. Rare gas excimers have long been one of the very few laser media in the VUV spectral region [1]. The emission wavelength of Ar2* is 126 run which is long enough to use transmission optical elements such as MgF2 and LiF. The Kr2* laser has an even longer emission wavelength centered at 147 mn which relaxes the conditions for optics and would become a competitor to the F2 laser at 157 run.
    [Show full text]
  • Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: a Review of Methods and Results
    Sensors 2010, 10, 7434-7468; doi:10.3390/s100807434 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Review Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results Rosalba Gaudiuso 1,*, Marcella Dell’Aglio 2, Olga De Pascale 2, Giorgio S. Senesi 2 and Alessandro De Giacomo 1,2 1 Department of Chemistry, University of Bari, via Orabona 4, 79126, Bari, Italy; E-Mail: [email protected] 2 IMIP-CNR sec. Bari, via Amendola 122/D, 70126, Bari, Italy; E-Mails: [email protected] (M.D.A.); [email protected] (O.P.); [email protected] (G.S.S.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +39-080-5929522; +39-080-5929513; Fax: +39-080-5929520. Received: 7 April 2010; in revised form: 24 May 2010 / Accepted: 22 June 2010 / Published: 9 August 2010 Abstract: Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds.
    [Show full text]
  • Krf Laser Development A
    L+ (j@ fw” 2675-V* / 03 Los Alamos National bboratoq is operated by the University of CaI~ornia for the United States Department of Energy under contract W-7405 -ENG-36 Lowwmm Acknowledgements Technical Review: David C. Cartwnght Joseph F. Figuena Thomas E. McDonald Publication Support: Pa[ncia A. Hinnebusch, C/tiefEdi[or Susrut H. Kinzer, Edi(ou Florence M. Butler, Reference Librarian Lucy P. Maestas, Production A4anagcmen( Mildred E. Valdez, Special Assistant Elizabeth Courtney, Word Processing, Graphics Susan L. Carlson, Graphic Design Support AnnMarie Dyson, llluwations Donna L. Duran, Illustration Support Wendy M. Burditt, Word ProcessinglComposition Joyce A. Martinez, Word ProccssinglComposition Jody Shepard, Assistant Dorothy Hatch, Word Processing Printing Coordination Guadalupe D. Archuleta This document was produced on a Macintosh IITM.LaserWriter Plusw, Varityper VT600Pm, and CanonTM Scanner using Microsoft Wordw v 3.01 and 4.0, Expressionist,w and Adobe Illustratorm. The work reported here was supported by the Office of Inertial Confinement Fusion, Department of Energy — Defense Programs. Front Cover Interior of A URORA target chamber looking directly through the center of the target chamber ton’ard the lens cone. The array of ~’bite circles containing rectangular red stripes in the center of this photograph is a portion of the lens pla(e, some three meters behind the target chamber n’hichfocuses the 48 laser beatns onto the target. The small yellon’ sphere in the center of the chamber is an optical reference target used for optical aiignntent of the laser beants. The ycllom tube entering the chumberfiom (he upper left is part of the x-ray diagnostics system.
    [Show full text]
  • Excimer Laser Pure Mixtures
    Excimer Laser Pure Mixtures Excimer laser cavities are charged with an optional mixture of a halogen donor, typically fluorine or hydrogen chloride, a rare gas buffer and an inert gas diluent, usually helium. Sometimes a small amount of hydrogen is added as a lifetime extension additive. The use of Matheson Tri-Gas pure gas components with halogen mixtures permits the optimal charging of the laser cavity to provide stable pulsed laser output, enhanced shot to shot amplitude stability, increased gas fill time and reduced system contamination. Argon Cylinder Contents Major Component Concentration Size* US Metric Valve Outlet In Helium Certified or Unanalyzed 1 - 25% 300 269 ft3 7.07 m3 CGA 580 200 200 ft3 5.26 m3 In Neon Certified or Unanalyzed 1 - 25% 300 265 ft3 6.97 m3 CGA 580 200 199 ft3 5.23 m3 Shipping Information: DOT Name: . .Rare Gases Mixtures Hazard Class: . 2.2 ID No.: . .UN 1979 DOT Label: . Nonflammable Gas *Other sizes available on request. Hydrogen Cylinder Contents Major Component Concentration Size* US Metric Valve Outlet In Helium Certified or Unanalyzed 0.02 - 0.1% 300 269 ft3 7.07 m3 CGA 350 200 200 ft3 5.26 m3 In Neon Certified or Unanalyzed 0.02 - 0.1% 300 265 ft3 6.97 m3 CGA 580 200 199 ft3 5.23 m3 Shipping Information: DOT Name: . Compressed Gases, N.O.S. Hazard Class: . 2.2 ID No.: . .UN 1956 DOT Label: . Nonflammable Gas *Other sizes available on request. Excimer Laser Pure Mixtures Hydrogen Chloride Cylinder Contents Major Component Concentration Size* US Metric Valve Outlet In Helium Certified or Unanalyzed 0.2 - 10% 300 269 ft3 7.07 m3 CGA 330 200 200 ft3 5.26 m3 In Neon Certified or Unanalyzed 0.2 - 10% 300 265 ft3 6.97 m3 CGA 330 200 199 ft3 5.23 m3 Shipping Information: (Must list two components in parentheses in association with the proper shipping name.) DOT Name: .
    [Show full text]
  • Excimer and Free-Electron Lasers
    I I £ S" 00 ?^ I RT/TIB/84/39 T. LETARDt, A. RENIERI THE LIGHT FOR THE FUTURE: EXCIMER AND FREE-ELECTRON LASERS COMITATO NAZIONALE PER LA RICERCA E PER LO SVILUPPO DELL'ENERGIA NUCLEARE E DELLE ENERGIE ALTERNATIVE COMITATO NAZIONALE PER LA RICERCA E PER LO SVILUPPO DELL'ENERGIA NUCLEARE E DELLE ENERGIE ALTERNATIVE THE LIGHT FOR THE FUTURE: =><* AND FREE-ELECTRON LASERS T. LETARDI, A. REHIERI Dipartimento TIB, Divisioue Fisica Applicata, C.R.E. Frascati g^CA;-. mYTIB/84/39 Testo pervenuto in dicembre 1984 This report has been prepared by: Servizio Studi e Docuaientazione • ENEA, Centro Ricerrhe Energia Fraacati, C.P. 65 - 00044 Frascati, Hone, Italy. Thia Office vili be glad to aend further copiea of thia report on requeat. The technical and scientific contents of theae reporta expreaa the opinioni o.' the authora but not necessarily "lose of ENEA Sjhmittrd to New Technologies in Neurosurgery ABSTRACT The status of art of two interesting kind of coherent radia­ tion sources (excimer and free-electron lasers) is described. The working principles of exciser lasers is analyzed together with the most relevant characteristics (active media, operating wave­ length, average and peak power, spectrum and time structure). As to the free-electron laser, whose development is at the very first stage, theoretical and experimental aspects are described and perspectives for the future are discussed. RIASSUNTO Viene descritto lo stato dell'arte di due tipi di sorgente laser che grande interesse hanno sollevato in questi ultimi anni, il laser ad eccimeri ed il laser ad ad elettroni liberi. Per il laser ad eccimeri, assieme a principi di funzionamento, vengono descritte le più importanti caratteristiche (mezzi attivi, lun­ ghezze d'onda di emissione, potenza media e di picco, caratteri­ stiche spettrali e temporali).
    [Show full text]
  • High-Performance Resist Materials for Arf Excimer Laser and Electron Beam Lithography
    High-Performance Resist Materials for ArF Excimer Laser and Electron Beam Lithography vKoji Nozaki vEi Yano (Manuscript received November 29, 2001) High-performance resist materials for ArF (argon fluoride) excimer laser ( = 193 nm) and electron beam (EB) lithography for fabricating 100 nm-level and beyond ULSIs have been developed. For the base polymers of the ArF resists, a novel methacrylate was employed as a base polymer whose ester groups have chromophores with a low extinction coefficient at 193 nm. A polycyclic hydrocarbon substituent, called adamantyl, and lactone substituents were introduced for acid-labile ester groups in the methacrylate polymer. The alicyclic group provides superior sensitivity, resolu- tion, and dry-etch resistance, while the lactone groups afford compatibility with a stan- dard TMAH (tetramethylammonium hydroxide) developer, good resolution, and adhesion to Si substrates. For the base polymer of the EB resist, the above-mentioned adaman- tyl methacrylate unit was applied in a vinylphenol copolymer. By optimizing the com- positions of these resists and the process conditions, we achieved a 100 nm line and space pattern by ArF excimer laser lithography and a 59 nm hole pattern by EB lithog- raphy. 1. Introduction erate solubility in an alkali developer as well as a Increasing demands for devices with higher good dry-etch resistance.2) Phenolic resists can- circuit densities have led to the use of shorter- not be used in ArF lithography, however, because wavelength light sources in optical lithography. they are completely opaque at 193 nm. In con- KrF (krypton fluoride) excimer laser lithography trast, it is well known that aliphatic polymers such (λ = 248 nm) has been used for the production of as methacrylates have low absorption at 193 nm, devices having design rules ranging from 250 to but they also have a poor dry-etch resistance.3),4) 130 nm.
    [Show full text]
  • The Argon Fluoride Laser As an Enabler for Low Cost Inertial Fusion Energy
    The Argon Fluoride laser as an enabler for low cost inertial fusion energy ARPA-E FUSION Workshop August 13-14, 2019 San Francisco Airport Marriott Waterfront Presented by Stephen Obenschain Laser Plasma Branch Plasma Physics Division Why an ArF laser driver could enable lower cost modest size laser IFE power plants The superior laser target coupling with ArF’s deep UV light (193 nm) could enable the high target gains needed for the energy application at much lower laser energies than previously thought feasible. The combination of deep UV light and broad native bandwidth (>5 THz) suppresses laser-plasma instabilities that limit the laser intensity and ablation pressures of current 351 nm frequency-tripled glass lasers which are the traditional laser drivers for fusion. ArF is a potentially disruptive technology for laser fusion that shares several advantageous technologies with the krypton fluoride (KrF) laser technology (λ=248 nm) used on the Nike laser system located at the Naval Research Laboratory (NRL). The ArF laser would utilize similar electron-beam pumping to that used for large KrF amplifiers. It would also be able to use the beam smoothing technology demonstrated on Nike that enables very uniform illumination of directly driven targets and provides the capability to “zoom” the focal profile to follow an imploding target. The KrF technology was chosen for the Nike facility because of numerous advantages for achieving laser fusion. ArF laser light in turn would be superior to KrF. For the IFE application, kinetics simulations indicate that ArF would have as much as 1.6x higher intrinsic efficiency than KrF.
    [Show full text]
  • Observation of Helium Excimer Clusters Generated Via Neutron-3He Absorption Reaction Department of Physics, Nagoya University Taku Matsushita
    Observation of Helium Excimer Clusters Generated via Neutron-3He Absorption Reaction Department of Physics, Nagoya University Taku Matsushita 1. Introduction Turbulence is one of subjects which is scientifically and industrially important but whose detail remains unsolved by its complexity. Therefore, quantum turbulence, where vortices are quantized, has been expected to be a key to solve the physics of turbulence, in addition to scientific interests on the nature specific of quantized vortices. To study quantum turbulence existing in superfluid 4He, recently flow visualization using triplet metastable 4He molecules (excimers) He2* as a tracer was emerged to be a new method which provides us information on normal-component flow individually [Marakov et al., Phys. Rev. B (2015)]. However, complete observation of the velocity fields in turbulent superfluid 4He requires localized small clouds of He2* excimers, clusters, of which generation method has not been established so far. Thus, to realize such excimer clusters, we proposed the use of the neutron absorption reaction 3He(n,p)3H of 3He impurities contained in liquid 4He, where 1H and 3H resulted by the reaction have sufficient energy to excite 4He atoms for excimer generation. And, we started the proof-of-principle experiments using the neutron beam of J-PARC/MLF. As the first step, in previous experiment (Project No. 2016B0111), we found that the application of neutron beam increases the signal suggesting He2* excimer generation, but the reproducibility and stability were not sufficient for detailed analyses. Therefore, we improved the detection system as shown in the next section. Thus, this experiment was conducted to obtain the proof of excimer generation via neutron-3He absorption reaction by quantitative analyses of improved experimental data.
    [Show full text]
  • Two-Wavelength Dye Laser Pumped by Excimer Laser
    Optica Applicata, Vol. XXII, No. 2, 1992 Two-wavelength dye laser pumped by excimer laser L. Pokora, Z. P uzewicz, Z. U jda Institute of Quantum Electronics, ul. S. Kaliskiego 6, 01—489 Warszawa, Poland. A photodynamic cancer diagnosis and treatment system has been developed, using an excimer-dye laser as a light source. The diagnosis and treatment laser beams were alternately generated by one dye laser having two-cell dye cuvette. In initial laboratory testing being presently performed, the system is yielding encouraging results. 1. Introduction One of the more interesting applications of dye lasers is their use in medicine — in the photodynamic method of tumor treatment (PDT). In the initial phase of research, simple light bulbs, xenon lamps and others with high illumination intensity were used. Only the introduction of lasers, producing narrow beams of light which could be led through a flexible optical cable and introduced via the arm of an endoscope into internal organs had created the possibility of using the photodynamic method for treatment of almost all internal organs. The laser set appropriate for both the PDT method and hematoporphyrin type preparations is the one which generates radiation of about 405 nm wavelength for suitable diagnostic purposes and 630 nm for tumor therapy. The 405 nm radiation is optimal for the first absorption peak of porphyrines. As a result of light absorption at this wavelength the region becomes strongly fluorescent in the red light band. The laser light wavelength of 630 nm fits into the weaker peak of absorption, but assures greater penetration of the light into human tissue.
    [Show full text]
  • Excimer Lasers • Currently Best UV Laser Sources • Consist Two Atom
    Excimer Lasers • Currently best UV laser sources • Consist two atom types which repel each other • eg nobel gas and halide or oxide which normally do not bond • But when excited/ionized these atoms attract • Bound together separated by short distance • Call this Excited state Dimer: Excimer • Argon, Xenon, Krypton in excited states • Oxygen or halids (Fluorine or Chlorine) • ArF, XeF, KrF, XeCl, KrCl • Deep UV operation: 195 - 350 nm • Oxide excimers at 558 nm yellow green oxygen glow Excimer Lasers • Mixture of gases below 5 atm • 90% - 99% buffer gas (He, Ne) for energy transfer • 1% - 9% dimer, 0.1-0.2% halide • Super-radiant lasers; 4% output mirror, reflective back • Quartz optics for XeCl • Fluorine would etch Quartz • Hence F lasers use magnesium fluoride or calcium fluoride • Cavity's under 1 m • To stabilize beam use injection locking with a Master Oscillator Power Amplifier (MOPA) Excimer dielectric mirrors Excimer Lasers • Excimer state short lived: pulses about 10 nsec • Repetition rate 100 - 300 Hz • Efficiency about 2% for KrF • Pulses highly unstable • 0.3 nm spectral width • Highly unstable modes: 2500 measured • Used for photoablation: wavelength so short destroys organics • KrF & ArF Main source for microelectronics exposure systems • Wavelength 249, 195 nm Vacuum UV: air absorbs Excimer Lasers • Excimer Lasers expensive to set up • Beam quality very poor • Emission area very large (eg 12x30 mm) • Bearly a laser • Need considerable support devices • Laser is heavy ~ 200-400 kg • Must have gas bottle cabinets (eg Xe & Cl) & ventilation system • Gas cabinets needed to catch leaks – deadly • Need a beam shaper to get good quality beam shapes wavefront so it can be focused ~ 10x • Costs high – laser $100K, but optics, gas cabinets another $100K Typical Excimer Lasers Chemical Laser • Chemical reaction to create laser action • Proposed by J.C.
    [Show full text]