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Sample records for 157-nm excimer laser

  1. Behavior of 157 nm excimer-laser-induced refractive index changes in silica

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.

    2006-09-15

    This study describes the observation of large induced refractive index changes produced by 157 nm excimer laser exposure in high-purity synthetic silica glasses. With 157 nm exposure, large induced changes are observed within a few hundred thousand pulses of exposure. Similar to 193 nm exposures, exposure with polarized 157 nm light yields polarization-induced birefringence (PIB). However, the 157 nm exposure also exhibits a behavior not observed with 193 nm exposures; namely, the initial response of the glass is a decrease in refractive index, followed by an increase with continued exposure. An explanation of the behaviors for both wavelength results is proposed where the induced refractive index is considered to arise from two different concurrent phenomena. One produces a decreased refractive index and also accounts for the PIB. The other, which accounts for the increased refractive index, is associated with an isotropic laser-induced volume change.

  2. Precision drilling of fused silica with 157-nm excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

    2003-07-01

    μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

  3. F 2 excimer laser (157 nm) radiation modification and surface ablation of PHEMA hydrogels and the effects on bioactivity: Surface attachment and proliferation of human corneal epithelial cells

    NASA Astrophysics Data System (ADS)

    Zainuddin; Chirila, Traian V.; Barnard, Zeke; Watson, Gregory S.; Toh, Chiong; Blakey, Idriss; Whittaker, Andrew K.; Hill, David J. T.

    2011-02-01

    Physical and chemical changes at the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified by ablation with an F 2 excimer laser were investigated experimentally. An important observation was that only the outer exposed surface layers of the hydrogel were affected by the exposure to 157 nm radiation. The effect of the surface changes on the tendency of cells to adhere to the PHEMA was also investigated. A 0.5 cm 2 area of the hydrogel surfaces was exposed to laser irradiation at 157 nm to fluences of 0.8 and 4 J cm -2. The changes in surface topography were analysed by light microscopy and atomic force microscopy, while the surface chemistry was characterized by attenuated total reflection infrared and X-ray photoelectron spectroscopies. Cell-interfacial interactions were examined based on the proliferation of human corneal limbal epithelial (HLE) cells cultured on the laser-modified hydrogels, and on the unexposed hydrogels and tissue culture plastic for comparison. It was observed that the surface topography of laser-exposed hydrogels showed rippled patterns with a surface roughness increasing at the higher exposure dose. The changes in surface chemistry were affected not only by an indirect effect of hydrogen and hydroxyl radicals, formed by water photolysis, on the PHEMA, but also by the direct action of laser radiation on PHEMA if the surface layers of the gel become depleted of water. The laser treatment led to a change in the surface characteristics, with a lower concentration of ester side-chains and the formation of new oxygenated species at the surface. The surface also became more hydrophobic. Most importantly, the surface chemistry and the newly created surface topographical features were able to improve the attachment, spreading and growth of HLE cells.

  4. Absolute measurement of F2-laser power at 157 nm

    SciTech Connect

    Kueck, Stefan; Brandt, Friedhelm; Kremling, Hans-Albert; Gottwald, Alexander; Hoehl, Arne; Richter, Mathias

    2006-05-10

    We report a comparison of laser power measurements at the F2-laser wavelength oaf nm made at two facilities of the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute. At the PTB laboratory at the electron storage ring BESSY II in Berlin, the scale for laser power was directly traced to a cryogenic radiometer operating at 157 nm, whereas at the PTB laser radiometry facility in Braunschweig the calibration of transfer detectors was performed with a newly developed standard for laser power at 157 nm, which is traceable in several steps to a cryogenic radiometer operating at 633 nm. The comparison was performed under vacuum conditions with laser pulse energies of?10 {mu}J, however with different average powers because different primary standard radiometers were used. The relative deviation for the responsivity of the transfer detector was 4.8% and thus within the combined standard uncertainty.

  5. Excimer lasers

    NASA Technical Reports Server (NTRS)

    Palmer, A. J.; Hess, L. D.; Stephens, R. R.

    1976-01-01

    A theoretical and experimental investigation into the possibility of achieving CW discharge pumped excimer laser oscillation is reported. Detailed theoretical modeling of capillary discharge pumping of the XeF and KXe and K2 excimer systems was carried out which predicted the required discharge parameters for reaching laser threshold on these systems. Capillary discharge pumping of the XeF excimer system was investigated experimentally. The experiments revealed a lower excimer level population density than predicted theoretically by about an order of magnitude. The experiments also revealed a fluorine consumption problem in the discharge in agreement with theory.

  6. Formation of Micro and Nano Structures Using VUV 157 nm Laser Radiation

    SciTech Connect

    Walton, C. D.; Cockcroft, S.

    2010-10-08

    We report on laser ablation experiments on micro and nano size composite structures. The surface of CR-39 and polycarbonate has been intentionally seeded with silicon carbide and silver nanowires and subsequently laser irradiated at a wavelength of 157 nm. We show scanning electron micrograph images of prismatic and conical structures produced by laser ablation and discuss a shape transformation from a prismatic to a conical structure.

  7. Excimer lasers

    NASA Technical Reports Server (NTRS)

    Palmer, A. J.; Hess, L. D.; Stephens, R. R.; Pepper, D. M.

    1977-01-01

    The results of a two-year investigation into the possibility of developing continuous wave excimer lasers are reported. The program included the evaluation and selection of candidate molecular systems and discharge pumping techniques. The K Ar/K2 excimer dimer molecules and the xenon fluoride excimer molecule were selected for study; each used a transverse and capillary discharges pumping technique. Experimental and theoretical studies of each of the two discharge techniques applied to each of the two molecular systems are reported. Discharge stability and fluorine consumption were found to be the principle impediments to extending the XeF excimer laser into the continuous wave regime. Potassium vapor handling problems were the principal difficulty in achieving laser action on the K Ar/K2 system. Of the four molecular systems and pumping techniques explored, the capillary discharge pumped K Ar/K2 system appears to be the most likely candidate for demonstrating continuous wave excimer laser action primarily because of its predicted lower pumping threshold and a demonstrated discharge stability advantage.

  8. Surface modification of polyhedral oligomeric silsesquioxane block copolymer films by 157 nm laser light

    NASA Astrophysics Data System (ADS)

    Sarantopoulou, Evangelia; Kollia, Zoe; Cefalas, Alkiviadis Constantinos; Siokou, Ageliki Elina; Argitis, Panagiotis; Bellas, Vassilios; Kobe, Spomenka

    2009-06-01

    Thin films of ethyl polyhedral oligomeric silsesquioxane (ethyl-POSS) containing polymers at different compositions were chemically modified using laser irradiation at 157 nm. The irradiation caused photodissociation of C-O and C-H bonds followed by the formation of new chemical bonds. The content of Si-O and C-O bonds increased, as did the surface hardness. Vacuum ultraviolet (VUV) absorption, mass spectrometry, x-ray photoelectron spectroscopy, and atomic force microscopy imaging and indentation were used to evaluate the effects of the 157 nm irradiation. The chemical modification was restricted to a thin surface layer. The layer depth was determined by the penetration depth of the 157 nm VUV photons inside the thin copolymer layer. With prolonged VUV irradiation, the absorbance of the polymers increased, eventually becoming saturated. The chemical changes were accompanied by surface hardening, as evidenced by the increase in the Young's modulus from 4 to 24 GPa due to glassification of the irradiated parts. The chemically modified layer acts as a shield against photodissociation and degradation of the deeper portion of the POSS polymer by VUV radiation. Applications include the protection of solar cells on low orbit satellites from solar VUV photons.

  9. 157 nm F2-laser writing of silica optical waveguides in silicone rubber

    NASA Astrophysics Data System (ADS)

    Okoshi, Masayuki; Li, Jianzhao; Herman, Peter R.

    2005-10-01

    Silica (SiO2) optical waveguides have been fabricated on the surface of silicone [(SiO(CH3)2)n] rubber by photochemical modification of silicone rubber into silica with 157 nmF2-laser radiation. The 2 mm thick silicone was exposed through a thin (˜0.2 mm) air layer to generate oxygen radicals that chemically assisted in the silica transformation. Silica waveguides were defined in 8-16 µm wide exposure strips by a proximity Cr-on-CaF2 photomask. Optimum laser processing conditions are presented for generating crack-free waveguides with good optical transparency at red (635 nm) and infrared (1550 nm) wavelengths. A propagation loss of ˜6 dB/cm is reported at the 1550 nm wavelength.

  10. 157 nm F2-laser writing of silica optical waveguides in silicone rubber.

    PubMed

    Okoshi, Masayuki; Li, Jianzhao; Herman, Peter R

    2005-10-15

    Silica (SiO2) optical waveguides have been fabricated on the surface of silicone [(SiO(CH3)2)n] rubber by photochemical modification of silicone rubber into silica with 157 nm F2-laser radiation. The 2 mm thick silicone was exposed through a thin (approximately 0.2 mm) air layer to generate oxygen radicals that chemically assisted in the silica transformation. Silica waveguides were defined in 8-16 microm wide exposure strips by a proximity Cr-on-CaF2 photomask. Optimum laser processing conditions are presented for generating crack-free waveguides with good optical transparency at red (635 nm) and infrared (1550 nm) wavelengths. A propagation loss of approximately 6 dB/cm is reported at the 1550 nm wavelength. PMID:16252756

  11. VUV 157nm laser ablation of spherical particles and modelling of whispering gallery mode optical antenna structures

    SciTech Connect

    Walton, C. D.; Cockcroft, S.; Metheringham, W. J.

    2012-07-30

    We report on VUV 157nm F{sub 2} laser irradiation of CR-39 polymer substrates that have been intentionally seeded with spherical glass particles. We discuss the importance of adhesive forces for realizing spherical cavity structures by laser ablation. Strong optical absorption at 157nm in CR-39 enables precise control of pedestal height by controlling the laser fluence and the number of laser pulses. Resonant modes for free-standing spherical cavities have been calculated and we discuss briefly the potential applications for use as optical sources on-board lab-on-chip devices.

  12. Miniature in-line photonic crystal fiber etalon fabricated by 157 nm laser micromachining.

    PubMed

    Ran, Z L; Rao, Y J; Deng, H Y; Liao, X

    2007-11-01

    A miniature in-line fiber-optic Fabry-Perot etalon is fabricated on a photonic crystal fiber (PCF) by using 157 nm laser micromachining for the first time to our knowledge. Experimental results show that such a PCF-based etalon has an excellent fringe visibility of up to approximately 26 dB due to the mirror-finish quality of the two cavity surfaces inside the PCF. This etalon can be used as an ideal sensor for precise strain measurement under high temperature of up to 800 degrees C. It can also offer some other outstanding advantages, such as fast and easy fabrication, high reproducibility, capacity of mass production, low cost, low temperature-strain cross-sensitivity, and high signal-to-noise ratio. PMID:17975600

  13. Excimer Laser Etching

    SciTech Connect

    Boatner, Lynn A; Longmire, Hu Foster; Rouleau, Christopher M; Gray, Allison S

    2008-04-01

    Excimer laser radiation at a wavelength of = 248 nm represents a new etching method for the preparation of metallographic specimens. The method is shown to be particularly effective for enhancing the contrast between different phases in a multiphase metallographic specimen.

  14. Excimer Lasers In Medicine

    NASA Astrophysics Data System (ADS)

    Tittel, Frank K.; Saidi, Iyad S.; Pettit, George H.; Wisoff, P. J.; Sauerbrey, Roland A.

    1989-06-01

    Excimer lasers emit light energy, short optical pulses at ultraviolet wavelengths, that results in a unique laser tissue interaction. This has led to an increasing number of studies into medical applications of these lasers in fields such as ophthalmology, urology, cardiology and neurology.

  15. Excimer laser system Profile-500

    NASA Astrophysics Data System (ADS)

    Atejev, V. V.; Bukreyev, V. S.; Vartapetov, Serge K.; Semenov, A. D.; Sugrobov, V. A.; Turin, V. S.; Fedorov, Sergei N.

    1999-07-01

    The description of ophthalmological excimer laser system 'PROFILE-500' for photorefractive and physiotherapeutic keratectomy is presented. Excimer Laser Systems 'PROFILE- 500' are optical system that use ArF excimer lasers to perform photorefractive keratectomy or LASIK; surgical procedures used to correct myopia, hyperopia and astigmatism.

  16. Production of microstructures in wide-band-gap and organic materials using pulsed laser ablation at 157 nm wavelength

    NASA Astrophysics Data System (ADS)

    Haehnel, Falk; Bertram, Rene; Reisse, Guenter; Boettcher, Rene; Weissmantel, Steffen

    2010-11-01

    New results on three-dimensional microstructuring of fused silica, sapphire, calcium fluoride, magnesium fluoride, and PTFE using pulsed laser ablation at 157 nm wavelength are presented. A largely automated high-precision fluorine laser micromachining station was used for the investigations. In some fundamental investigations, threshold fluences of 0.9 J/cm2 for fused silica, 0.6 J/cm2 for sapphire, 1.7 J/cm2 for calcium fluoride, and of 0.05 J/cm2 for PTFE have been determined. The ablation rates at 3 J/cm2 fluence were 60 to 100 nm/pulse for the inorganic insulators and 450 nm/pulse for PTFE. In the second part of the paper, it is shown that on the basis of the knowledge of the ablation rates and the laser beam parameters, bores of a few µm size and complex 3D microstructures with a variety of geometries can be produced in the surface of these materials. Thereby, no cracking occurs if proper parameters are used.

  17. Photodissociation of the hydroxyl radical (OH) at 157 nm

    NASA Technical Reports Server (NTRS)

    Cody, R. J.; Moralejo, C.; Allen, J. E., Jr.

    1991-01-01

    The photodissociation of the OH radical was studied at 157 nm via the detection of the product H atoms with the resonance fluorescence technique. OH radicals were produced in a fast-flow cell from the reaction between H and NO2 and subsequently photodissociated by an excimer laser operating on the F2 emission. The quantum yield for photodissociation of OH was measured to be 1.10 + or - 0.28. The photodissociation cross section was calculated to be 6.6 x 10 to the -18th sq cm (+ or - 25 percent).

  18. Excimer laser photoresist stripping

    NASA Astrophysics Data System (ADS)

    Genut, Menachem; Tehar-Zahav, Ofer; Iskevitch, Eli; Livshits, Boris

    1996-06-01

    A new method for stripping the most challenging photoresists on deep sub-micron technology semiconductor wafers has been developed. The method uses a combination of UV excimer laser ablation and reactive chemistry to strip the photoresist in a single dry process, eliminating the wet acids or solvents often used following ashing of high dose implantation (HDI) and reactive ion etching (RIE). The stripping process combines new removal mechanisms: chemical assisted UV excimer laser ablation/etching, laser induced chemical etching of side walls and residues, and enhanced combustion. During the laser pulses photolysis of the process gas occurs, UV laser radiation breaks the photoresist polymer chain bonds, and the photoresist (including foreign materials imbedded in it) is ablated. The combustion is ignited by the ablative impact of laser radiation and enhanced by the radicals formed during photo-thermal decomposition of the process gases. Following this process, the volatilized products and gases are evacuated. The optimum laser stripping conditions were developed to provide a wide process window for the most challenging stripping conditions, such as after HDI and RIE (metal, polysilicon), without causing damage to the wafer devices. A photoresist stripping system based on the described technology was designed and built. The system has been designated as the L-StripperTM and provides stripping time of 0.15 s/(micrometer cm2).

  19. Viability of Cladosporium herbarum spores under 157 nm laser and vacuum ultraviolet irradiation, low temperature (10 K) and vacuum

    NASA Astrophysics Data System (ADS)

    Sarantopoulou, E.; Stefi, A.; Kollia, Z.; Palles, D.; Petrou, P. S.; Bourkoula, A.; Koukouvinos, G.; Velentzas, A. D.; Kakabakos, S.; Cefalas, A. C.

    2014-09-01

    Ultraviolet photons can damage microorganisms, which rarely survive prolonged irradiation. In addition to the need for intact DNA, cell viability is directly linked to the functionality of the cell wall and membrane. In this work, Cladosporium herbarum spore monolayers exhibit high viability (7%) when exposed to 157 nm laser irradiation (412 kJm-2) or vacuum-ultraviolet irradiation (110-180 nm) under standard pressure and temperature in a nitrogen atmosphere. Spore viability can be determined by atomic-force microscopy, nano-indentation, mass, μ-Raman and attenuated reflectance Fourier-transform far-infrared spectroscopies and DNA electrophoresis. Vacuum ultraviolet photons cause molecular damage to the cell wall, but radiation resistance in spores arises from the activation of a photon-triggered signaling reaction, expressed via the exudation of intracellular substances, which, in combination with the low penetration depth of vacuum-ultraviolet photons, shields DNA from radiation. Resistance to phototoxicity under standard conditions was assessed, as was resistance to additional environmental stresses, including exposure in a vacuum, under different rates of change of pressure during pumping time and low (10 K) temperatures. Vacuum conditions were far more destructive to spores than vacuum-ultraviolet irradiation, and UV-B photons were two orders of magnitude more damaging than vacuum-ultraviolet photons. The viability of irradiated spores was also enhanced at 10 K. This work, in addition to contributing to the photonic control of the viability of microorganisms exposed under extreme conditions, including decontamination of biological warfare agents, outlines the basis for identifying bio-signaling in vivo using physical methodologies.

  20. Viability of Cladosporium herbarum spores under 157 nm laser and vacuum ultraviolet irradiation, low temperature (10 K) and vacuum

    SciTech Connect

    Sarantopoulou, E. Stefi, A.; Kollia, Z.; Palles, D.; Cefalas, A. C.; Petrou, P. S.; Bourkoula, A.; Koukouvinos, G.; Kakabakos, S.; Velentzas, A. D.

    2014-09-14

    Ultraviolet photons can damage microorganisms, which rarely survive prolonged irradiation. In addition to the need for intact DNA, cell viability is directly linked to the functionality of the cell wall and membrane. In this work, Cladosporium herbarum spore monolayers exhibit high viability (7%) when exposed to 157 nm laser irradiation (412 kJm⁻²) or vacuum-ultraviolet irradiation (110–180 nm) under standard pressure and temperature in a nitrogen atmosphere. Spore viability can be determined by atomic-force microscopy, nano-indentation, mass, μ-Raman and attenuated reflectance Fourier-transform far-infrared spectroscopies and DNA electrophoresis. Vacuum ultraviolet photons cause molecular damage to the cell wall, but radiation resistance in spores arises from the activation of a photon-triggered signaling reaction, expressed via the exudation of intracellular substances, which, in combination with the low penetration depth of vacuum-ultraviolet photons, shields DNA from radiation. Resistance to phototoxicity under standard conditions was assessed, as was resistance to additional environmental stresses, including exposure in a vacuum, under different rates of change of pressure during pumping time and low (10 K) temperatures. Vacuum conditions were far more destructive to spores than vacuum-ultraviolet irradiation, and UV-B photons were two orders of magnitude more damaging than vacuum-ultraviolet photons. The viability of irradiated spores was also enhanced at 10 K. This work, in addition to contributing to the photonic control of the viability of microorganisms exposed under extreme conditions, including decontamination of biological warfare agents, outlines the basis for identifying bio-signaling in vivo using physical methodologies.

  1. Production excimer laser equipment overview

    NASA Astrophysics Data System (ADS)

    Sercel, Jeffrey P.

    1993-04-01

    Excimer lasers were commercialized in the late 1970's. The laser community thought that by the early 1980's these UV lasers would enjoy a fruitful industrial market position. CO2 and solid state lasers required almost two decades to be fully accepted as industrial machine while the excimer laser was expected to be a fast learner benefiting from the learning curve of its big brothers. In retrospect, early excimer lasers had a bad reputation for being complicated, expensive and frequently out of commission. By the late 1980's a few excimer laser manufacturers had engineered the problems to acceptable levels for successful pilot lines and small scale manufacturing to begin. At this time, the real industrial learning curves began as engineers worked to refine many subsystems and support technologies. Today, excimer lasers are being used as true industrial lasers. They have a bright future with numerous and diverse market opportunities. This paper is an overview of the technologies proven to be successful in adapting modern excimer lasers to successful full production situations.

  2. High power excimer laser micromachining

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Paetzel, Rainer

    2006-02-01

    Today's excimer lasers are well-established UV laser sources for a wide variety of micromachining applications. The excimer's high pulse energy and average power at short UV wavelengths make them ideal for ablation of various materials, e. g., polyimide, PMMA, copper, and diamond. Excimer micromachining technology, driven by the ever-shrinking feature sizes of micro-mechanical and micro-electronic devices, is used for making semiconductor packaging microvias, ink jet nozzle arrays, and medical devices. High-power excimer laser systems are capable of processing large areas with resolution down to several microns without using wet chemical processes. For instance, drilling precise tapered holes and reel-to-reel manufacturing of disposable sensors have proven to be very cost-effective manufacturing techniques for volume production. Specifically, the new industrial excimer laser-the LAMBDA SX 315C-easily meets the high demands of cost-effective production. The stabilized output power of 315 watts at 300 Hz (308 nm) and its outstanding long-term stability make this laser ideal for high-duty-cycle, high-throughput micromachining. In this paper, high-power excimer laser technology, products, applications, and beam delivery systems will be discussed.

  3. Wavelength conversion with excimer lasers

    SciTech Connect

    Booker, J.; Eichner, L.; Storz, R.H.; Bucksbaum, P.H.; Freeman, R.R.

    1983-01-01

    Harmonic generation was studied using a high powered, ultrashort pulse KrF excimer laser. Third, fifth, and seventh harmonic outputs were observed at 82.8 nm, 49.7 nm, and 35.5 nm. The nonlinear interaction took place at the intersection of the laser focus with a pulsed, supersonic gas jet expansion.

  4. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, Roger P.

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  5. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  6. Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm

    NASA Astrophysics Data System (ADS)

    Skordoulis, C.; Sarantopoulou, E.; Spyrou, S. M.; Kosmidis, C.; Cefalas, A. C.

    1991-06-01

    Laser induced fluorescence of the mercury clusters Hg2 and Hg3 in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr2 at 7.88 eV (157.5 nm) with an F2 molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters.

  7. Semiconductor processing with excimer lasers

    SciTech Connect

    Young, R.T.; Narayan, J.; Christie, W.H.; van der Leeden, G.A.; Rothe, D.E.; Cheng, L.J.

    1983-01-01

    The advantages of pulsed excimer lasers for semiconductor processing are reviewed. Extensive comparisons of the quality of annealing of ion-implanted Si obtained with XeCl and ruby lasers have been made. The results indicate that irrespective of the large differences in the optical properties of Si at uv and visible wavelengths, the efficiency of usage of the incident energy for annealing is comparable for the two lasers. However, because of the excellent optical beam quality, the XeCl laser can provide superior control of the surface melting and the resulting junction depth. Furthermore, the concentrations of electrically active point defects in the XeCl laser annealed region are 2 to 3 orders of magnitude lower than that obtained from ruby or Nd:YAG lasers. All these results seem to suggest that XeCl lasers should be suitable for fabricating not only solar cells but also the more advanced device structures required for VLSI or VHSIC applications.

  8. Excimer laser in arthroscopic surgery

    NASA Astrophysics Data System (ADS)

    Koort, Hans J.

    1991-05-01

    The development of efficient high-power lasersystems for use in surgery, especially in arthroscopic fields, leads to a new push for all endoscopic techniques. Both techniques, laser and endoscope, complete each other in an ideal way and allow applications which could not be reached with conventional techniques. One of the newer laser types is the excimer laser, which will be a good choice for surface treatment because of its very considerate interaction with tissue. One example is the ablation or smoothing of articular cartilage and meniscal shaving in orthopaedics. On the other hand, the power of this laser system is high enough to cut tissue, for instance in the lateral release, and offers therefore an alternative to the mechanical and electrical instruments. All lasers can only work fine with effective delivery systems. Sometimes there is only a single fiber, which becomes very stiff at diameters of more than 800 micrometers . This fiber often allows only the tangential treatment of tissue, most of the laser power is lost in the background. New fiber systems with many, sometimes hundreds of very thin single fibers, could offer a solution. Special handpieces and fibersystems offer distinct advantages in small joint arthroscopy, especially those for use with excimer lasers will be discussed.

  9. Excimer laser chemical problems

    SciTech Connect

    Tennant, R.; Peterson, N.

    1982-01-01

    Techniques need to be developed to maintain XeF and XeCl laser performance over long periods of time without degradation resulting from chemical processes occurring within the laser. The dominant chemical issues include optical damage, corrosions of laser materials, gas contamination, and control of halogen concentration. Each of these issues are discussed and summarized. The methods of minimizing or controlling the chemical processes involved are presented.

  10. Excimer laser ablation of ferrites

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    1991-02-01

    Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

  11. Excimer lasers drive large-area microprocessing

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph; Tapié, Jean-Luc

    2012-09-01

    Excimer lasers emitting in the UV to far UV region are by nature the laser sources enabling the highest optical resolution and strongest material-photon interaction. At the same time, excimer lasers deliver unmatched UV pulse energies and output powers up to the kilowatt range. Thus, they are the key to fast and effective large area processing of smallest structures with micron precision. As a consequence, excimer lasers are the UV technology of choice when it comes to high-performance microstructuring with unsurpassed quality and process repeatability in applications such as drilling advanced ink jet nozzles or patterning biomedical sensor structures.

  12. Granuloma Annulare Treated with Excimer Laser

    PubMed Central

    Ragi, Jennifer; Milgraum, Sandy

    2012-01-01

    Objective: To review the current therapy for granuloma annulare and report a case of refractory generalized granuloma annulare successfully treated with excimer laser. A discussion about the characteristics of excimer laser and the mechanism of its effectiveness is presented. Design: Patient case report and literature review. Setting: Outpatient dermatology practice. Participants: A 73-year-old woman suffering from generalized granuloma annulare for more than 40 years. Measurements: Change in clinical appearance of lesions. Results: Use of excimer laser therapy resulted in prompt and complete resolution in treated areas with no residual skin changes or side effects. Conclusion: Excimer laser therapy is a powerful treatment modality with minimal side effects for patients with granuloma annulare. Further study is necessary to elucidate optimal dosing, long-term efficacy, and safety profile. PMID:23198013

  13. 308nm excimer laser in dermatology.

    PubMed

    Mehraban, Shadi; Feily, Amir

    2014-01-01

    308nm xenon-chloride excimer laser, a novel mode of phototherapy, is an ultraviolet B radiation system consisting of a noble gas and halide. The aim of this systematic review was to investigate the literature and summarize all the experiments, clinical trials and case reports on 308-nm excimer laser in dermatological disorders. 308-nm excimer laser has currently a verified efficacy in treating skin conditions such as vitiligo, psoriasis, atopic dermatitis, alopecia areata, allergic rhinitis, folliculitis, granuloma annulare, lichen planus, mycosis fungoides, palmoplantar pustulosis, pityriasis alba, CD30+ lympho proliferative disorder, leukoderma, prurigo nodularis, localized scleroderma and genital lichen sclerosus. Although the 308-nm excimer laser appears to act as a promising treatment modality in dermatology, further large-scale studies should be undertaken in order to fully affirm its safety profile considering the potential risk, however minimal, of malignancy, it may impose. PMID:25606333

  14. Effect of excimer laser on microbiological organisms

    SciTech Connect

    Keates, R.H.; Drago, P.C.; Rothchild, E.J.

    1988-10-01

    The effect of radiation emitted from an excimer laser filled with argon fluoride gas at 193 nm on Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus faecalis, Hemophilus influenzae, Candida albicans, and Aspergillus niger (collectively labeled the microorganisms) was examined. Colonies were subjected to a variable number of radiation pulses from the excimer laser applied after a 36-hour period of incubation at 37 degrees C, at which time the colonies were fully grown and showed no viability. The lack of viability was confirmed with a subculture from each area that received radiation; all subcultures were negative. The characteristics of the radiation paralleled those used by Serdavic, Darrell, Krueger, et al in 1985. This radiation treatment is believed to be within a therapeutic range, which suggests that the excimer laser, pending further investigation, may be useful in the treatment of corneal infections.

  15. 308-nm excimer laser in endodontics

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim

    1992-06-01

    Root canal preparation was performed on 20 extracted human teeth. After opening the coronal pulp, the root canals were prepared by 308 nm excimer laser only. All root canals were investigated under SEM after separation in the axial direction. By sagittal separation of the mandibles of freshly slaughtered cows, it was possible to get access to the tissues and irradiate under optical control. Under irradiation of excimer laser light, tissue starts to fluoresce. It was possible to demonstrate that each tissue (dentin, enamel, bone, pulpal, and connective tissue) has a characteristic spectral pattern. The SEM analyses showed that it is well possible to prepare root canals safely. All organic soft tissue has been removed by excimer laser irradiation. There was no case of via falsa. The simultaneous spectroscopic identification of the irradiated tissue provides a safe protection from overinstrumentation. First clinical trials on 20 patients suffering of chronical apical parodontitis have been carried out successfully.

  16. Excimer laser photorefractive surgery of the cornea

    NASA Astrophysics Data System (ADS)

    Gaster, Ronald N.

    1998-09-01

    The 193 nm argon fluoride (ArF) excimer laser can effectively be used to change the radius of curvature of the cornea and thus alter the refractive state of the eye. This change allows myopic (nearsighted) patients to see well with less dependence on glasses or contact lenses. The two major techniques of laser refractive surgery currently in effect in the United States are photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). This paper will discuss these refractive cornea surgical techniques.

  17. Corneal topography of excimer laser photorefractive keratectomy.

    PubMed

    Klyce, S D; Smolek, M K

    1993-01-01

    The application of the 193 nm excimer laser for keratorefractive surgery promises to deliver a higher degree of precision and predictability than traditional procedures such as radial keratotomy. The development and evaluation of keratorefractive surgery have benefited from the parallel advances made in the field of corneal topography analysis. We used the Computed Anatomy Topography Modeling System (TMS-1) to analyze a Louisiana State University (LSU) Eye Center series of patients who had photorefractive keratectomy for the treatment of myopia with the VISX Twenty/Twenty excimer laser system. The excimer ablations were characterized by a relatively uniform distribution of surface powers within the treated zone. In the few cases that exhibited marked refractive regression, corneal topography analysis showed correlative changes. With topographical analysis, centration of the ablations relative to the center of the pupil could be evaluated. Marked improvement in centration occurred in the patients of LSU Series IIB in which the procedure to locate the point on the cornea directly over the pupil's center during surgery was refined. Corneal topographical analysis provides objective measures of keratorefractive surgical results and is able to measure the precise tissue removal effect of excimer laser ablation without the uncertainties caused by measuring visual acuity alone. Our observations forecast the need for improved aids to center the laser ablations and for the development of a course of treatment to prevent post-ablation stromal remodeling. PMID:8450433

  18. Percutaneous angioscopy after excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Nakamura, Fumitaka; Kvasnicka, Jan; Geschwind, Herbert J.; Uchida, Yasumi

    1992-08-01

    Angioscopy has proved to provide more detailed information on lesion morphology before and after interventional procedures than angiography. Therefore, to evaluate the effects of laser angioplasty, angioscopy was performed in five patients with peripheral or coronary vascular disease who underwent excimer laser angioplasty. The excimer laser was operated at 308 nm, 135 nsec, 25 Hz, and 40 - 60 mJ/mm2 and was coupled into multifiber wire-guided catheters of 1.4 to 2.0 mm diameter for coronary lesions and 2.2 mm for peripheral lesions. There were three coronary (one left anterior descending, one circumflex, one right coronary artery) and two peripheral (one common iliac artery, one superficial femoral artery) lesions. Angioscopy was successfully performed before and after laser ablation without any complications in all five lesions. The characteristics of angioscopic findings after excimer laser angioplasty consisted of flaps, fractures of plaques, and abundant tissue remnants. There was no apparent thermal injury. Recanalized channels were small and irregular. These results indicate that (1) angioscopy is effective and safe for evaluation of lesion morphology after laser angioplasty, (2) laser ablation does not result in thermal injury, and (3) irregular channels after recanalization and abundant tissue remnants may explain the suboptimal results after laser angioplasty.

  19. Excimer Laser Application For Cataract Surgery

    NASA Astrophysics Data System (ADS)

    Bath, Patricia E.; Mueller, Gerhard; Apple, David J.; Stolzenburg, Norbert M.

    1988-06-01

    The ablation threshold of bovine lenses was determined for excimer laser radiatiF at 308 nanreters. The ablation th5eshold for bovine lenses was approximately 0.6J/cm +/-0.1J/cm , for cortex and 1J/cm for nucleus. The threshold for bovine nucleus was higher than the threshold for cortex and difference was statistically significant at the 0.05 level. The relatively low ablation threshold for bovine lenses demonstrates the potential effectiveness of excimer laser radiation at 308 nm for cataract surgery. An experimental prototype has been developed and results of its application demonstrated. Further experiments to demonstrate safety for the retina and adjacent ocular structures are necessary because of the well known hazards of ultraviolet radiation. The potential of theleymir laser for keratorefractive surgery is currently under intensive investigation. In preliminary studies the ablation behavior of bovine lenses was investigated. The objective of this study was to quantify ablation rates as the first step in determining the specification for a laser system which would be practical in the clinical setting. Although excimer laser systems are available at 193 nm (ArF), 248 (KrF) and 351 (xeF) we selected 308 nm because of the availability of fiberoptics for the transmission of 308 nm as well as the known absorbance of human lenses in the 280 nm region.

  20. Human excimer laser corneal surgery: preliminary report.

    PubMed Central

    L'Esperance, F A; Taylor, D M; Del Pero, R A; Roberts, A; Gigstad, J; Stokes, M T; Warner, J W; Telfair, W B; Martin, C A; Yoder, P R

    1988-01-01

    The first human trial utilizing the argon fluoride excimer laser at 193 nm to produce a superficial keratectomy in ten human eyes has been described with the histopathological evaluation of four eyes and the longer gross appearance of six eyes at intervals extending to 10 months post-excimer laser treatment. The process of laser superficial keratectomy has proved to be one of the promising areas of surgical intervention for reconstructive or refractive keratoplasty in the future. Intensive investigations need to be undertaken on the corneal wound healing process following laser ablation as well as the nature, and long-term stability of the corneal excisions or induced refractive corrections. It is essential that the optimal laser parameters be established for the various refractive corrections and other corneal surgical techniques, and that pathophysiologic and histopathologic changes that have been induced by the excimer laser-corneal tissue interaction in animals and humans be critically and extensively analyzed. Images FIGURE 1 FIGURE 19 A FIGURE 19 B FIGURE 20 A FIGURE 20 B FIGURE 21 A FIGURE 21 B FIGURE 22 A FIGURE 22 B FIGURE 23 FIGURE 24 FIGURE 25 FIGURE 26 FIGURE 27 FIGURE 28 FIGURE 29 A FIGURE 29 B FIGURE 29 C FIGURE 29 D FIGURE 30 A FIGURE 30 B FIGURE 31 A FIGURE 31 B FIGURE 32 FIGURE 33 FIGURE 34 FIGURE 35 FIGURE 36 FIGURE 37 A FIGURE 37 B FIGURE 37 C FIGURE 38 A FIGURE 38 B FIGURE 39 A FIGURE 39 B FIGURE 39 C FIGURE 40 A FIGURE 40 B PMID:2979049

  1. Progress in discharge-pumped excimer lasers

    NASA Astrophysics Data System (ADS)

    Pike, Charles T.

    1993-04-01

    This paper describes recent results achieved in the development of discharge pumped excimer lasers at the Textron Defense Systems organization (formerly the Avco Research Laboratory). Included is a description of a KrF laser with more than one Joule output at 2.4% efficiency, a 200 mJ XeCl laser operating with a 500 nsec wide pulse, and a several Joule, discharge pumped, KrCl laser operating at 222 nm. All of these devices are switched using thyratrons and are therefore capable of repetitive performance. The KrF and XeCl experiments were conducted with the same laser device operating with a conventional capacitor transfer excitation circuit for the KrF experiments but modified to operate with a pulser-sustainer discharge circuit using magnetic switching for the XeCl tests. The KrCl device is a 40 liter volume system built by Northrop and also operates with a magnetically switched discharge.

  2. Excimer laser machining of optical fiber taps

    NASA Astrophysics Data System (ADS)

    Coyle, Richard J.; Serafino, Anthony J.; Grimes, Gary J.; Bortolini, James R.

    1991-05-01

    Precision openings for construction of an optical backplane have been machined in an optical fiber using an excimer laser operating at a wavelength of 193 nm. The openings were made by imaging the laser beam onto the polymer fiber cladding with a telescope, then ablating the cladding with a sufficient number of pulses to expose the core. Circular openings measuring 250 and 625 microns and elliptical openings measuring 650 X 350 microns have been made in the cladding of a 1 mm polymer-clad silica fiber. Examination by scanning electron microscopy reveals that the best quality openings are obtained with either the smaller circular geometry or the elliptical geometry. For various reasons, elliptical openings, with the major axis oriented along the longitudinal axis of the fiber, appear more suitable for tap construction. Individual optical fiber taps have been constructed by attaching a tap fiber to a laser machined opening in a central fiber using an ultraviolet-curable acralate. Individual tap measurements were made on the elliptical and the 250 micron circular openings. In addition, a triple tap assembly was made using elliptical tap openings. These results indicate that the excimer laser machining technique may be applicable to the construction of a linear tapped bus for optical backplanes.

  3. Research of the quenched dye lasers pumped by excimer lasers

    SciTech Connect

    Xue Shaolin; Lou Qihong

    1996-12-31

    In this paper, the quenched dye lasers pumped by XeCl and KrF excimer lasers were investigated theoretically and experimentally. Dye laser pulses with duration of 0.8 ns for XeCl laser pumping and 2 ns for KrF laser pumping were obtained. The dye Rhodamine 6G dissolved in methyl was used as the active medium in the quenched dye laser. When the pump laser was KrF and the active medium was Coumarin 498 the quenched dye laser emitted pulse with duration of about 2 ns. The characteristics of the quenched dye laser was also investigated in detail.

  4. Excimer laser irradiation of metal surfaces

    NASA Astrophysics Data System (ADS)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  5. Optical Pattern Generator Using Excimer Laser

    NASA Astrophysics Data System (ADS)

    Hafner, Bernhard F.

    1988-01-01

    Reticles (masks on enlarged scale) are needed for optical pattern transfer in the production of integrated semiconductor circuits. In order to meet present requirements for 5X reticles only a direct writing technique is feasible. This means direct exposing of photoresist either with light or an electron beam. Many of todays highly dense reticles require some 10 5 to 10 6 discrete exposures when generated with an optical pattern generator. Optical pattern generators normally use mercury arc lamps to expose positive photoresist, which in turn need 200 milliseconds for each of these discrete exposures, thus requiring to stop the table at every exposure position ("stop and go" mode). This results in running times of several days per reticle. Therefore most reticles are nowadays being manufactured with very expensive e-beam machines. In the early 80's we started the first experiments to expose photoresist with an excimer laser. In order to obtain the maximum gain in speed, the goal was to operate with only one excimer laser pulse per exposure, so that a fast "flash on the fly" operation with an optical pattern generator became true. Equipping a conventional optical pattern generator with an excimer laser as the light source, it has become possible to expose substrates coated with standard photoresist in the "flash on the fly" mode with only 13 nanoseconds per flash. So the thruput could be increased up to 25 times in comparison to a pattern generator equipped with a mercury lamp. A comparison of both operation modes will show that an immense increase of speed is possible, even when a ten years old M3600 pattern generator is used. This system is in function now with very high reliability since more than three years in our IC development line.

  6. Fluorinated dissolution inhibitors for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Hamad, Alyssandrea H.; Bae, Young C.; Liu, Xiang-Qian; Ober, Christopher K.; Houlihan, Francis M.; Dabbagh, Gary; Novembre, Anthony E.

    2002-07-01

    Fluorinated dissolution inhibitors (DIs) for 157 nm lithography were designed and synthesized as part of an ongoing study on the structure/property relationships of photoresist additives. The problem of volatilization of small DI candidates was observed from matrices such as poly(methyl methacrylate) (PMMA) and poly(hexafluorohydroxy-isopropyl styrene) (PHFHIPS) during post-apply bake cycles using Fourier Transform Infrared Spectroscopy (FT-IR). To avoid this problem, low volatility fluorinated inhibitors were designed and synthesized. Three fluorinated DIs, perfluorosuberic acid bis-(2,2,2,-trifluoro-1-phenyl-1-trifluoromethyl-ethyl) ester (PFSE1), perfluorosuberic acid bis-[1-(4-trifluoromethyl-phenyl)-ethyl] ester (PFSE2) and a fluorinated phenylmethanediol diester (FPMD1), largely remained in a PHFHIPS film during the post-apply bake. The dissolution behavior of the two fluorinated diesters was studied and found to slow down the dissolution rate of PHFHIPS with inhibition factors of 1.9 and 1.6, respectively. The absorbance of PHFHIPS films containing 10 wt% of the diester inhibitors is 3.6 AU/micron compared with an absorbance of 3.3 AU/micron for the polymer itself. The absorbance of 10% FPMD1 in PHFHIPS was measured as 3.5 AU/micron compared with an absorbance of 3.4 AU/micron for the polymer itself. Thus, the non-volatility and transparency of the fluorinated inhibitors at 157 nm as well as their ability to reduce the development rate of fluorinated polymers make them suitable for use in a 157 nm resist system.

  7. Excimer laser annealing for low-voltage power MOSFET

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Okada, Tatsuya; Noguchi, Takashi; Mazzamuto, Fulvio; Huet, Karim

    2016-08-01

    Excimer laser annealing of lumped beam was performed to form the P-base junction for high-performance low-voltage-power MOSFET. An equivalent shallow-junction structure for the P-base junction with a uniform impurity distribution is realized by adopting excimer laser annealing (ELA). The impurity distribution in the P-base junction can be controlled precisely by the irradiated pulse energy density and the number of shots of excimer laser. High impurity activation for the shallow junction has been confirmed in the melted phase. The application of the laser annealing technology in the fabrication process of a practical low-voltage trench gate MOSFET was also examined.

  8. Excimer laser induced nanostructuring of silicon surfaces.

    PubMed

    Kumar, Prashant; Krishna, Mamidipudi Ghanashyam; Bhattacharya, Ashok

    2009-05-01

    The effect of KrF excimer laser energy density (below and above the ablation threshold), number of shots and angle of laser incidence on the morphological reconstruction, structure and specular reflectance of Si[311] surfaces is reported. At low energy densities (0.1 to 0.3 J/cm2) laser irradiation results in a variety of nanostructures, depending on laser energy density and number of shots, such as nanopores (40-60 nm dia) and nanoparticles (40-80 nm dia). At energies greater than the laser ablation threshold (2 to 5 J/cm2) the formation of nanowires (200 nm dia, 6-8 microm length), and closely spaced silicon nanograins (100-150 nm dia) is observed. Experiments to study the effect of laser irradiation in the proximity of a fixed shape such as a linear step edge in the form of a stainless steel blade and a cylindrical cross-section Cu wire were also carried out. In both cases, linearly organized nanoparticles (150-200 nm diameter) and nanowires (60-80 nm diameter) formed close to the edge. There is a systematic degradation of long-range order with the number of shots and laser energy density as evidenced from X-ray diffraction studies. At an energy density of 2 J/cm2, and 100 shots the [311] oriented silicon surface made a transition to a randomly oriented nanocrystalline state. PMID:19452995

  9. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1987-08-01

    The authors have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reactions cell. Spark schlieren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect.

  10. Excimer laser ablation of ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    We study the ablation of Ni-Zn or Mn-7n ferrites by 248-nm KrF excimer laser irradiation for high-resolution patterning. A transfer lens system is used to project the image of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluente for ablation of the ferrite surface is about 0.3 J/cm2. A typical fluente of 1 J/cm2 is used to produce good-quality patterning. Scanning electron microscopy of the ablated area shows a "glassy" skin with extensive microcracks and solidified droplets being ejected that is frozen in action. This skin can be removed by ultrasonic cleaning.

  11. XeCl excimer laser excited by longitudinal discharge

    SciTech Connect

    Zhou, Z.; Zeng, Y.; Qiu, M.

    1983-08-15

    XeCl excimer laser excited by longitudinal gas discharge is reported. The main characteristics of the laser output and the laser energy in dependence of the operating parameters were measured. The laser pulse duration was 35 ns and the maximum laser energy 317 ..mu..J with improvement by preionization.

  12. The excimer laser: science fiction fantasy or practical tool?

    PubMed

    Biamino, Giancarlo

    2004-12-01

    Nearly 20 years ago, in vitro experiments left no doubt about the fact that laser light can ablate atherosclerotic plaque. The initial enthusiastic results with the technology, particularly in coronary arteries, were followed by reports showing unacceptably high restenosis and complication rates. These poor results were due to the premature application of an underdeveloped technology, a lack of understanding of laser/tissue interaction, and the use of incorrect lasing techniques. Consequently, and without discrimination, all lasers were banned from the catheterization laboratories for nearly a decade. Technological enhancements of the excimer laser, combined with refined catheter lasing techniques, resulted in greater debulking of atherosclerotic material in long superficial femoral artery occlusions. These results triggered the application of the excimer laser technique as an atherectomy tool in more complex lesions below the knee. The multicenter Laser Atherectomy for Critical Ischemia study clearly demonstrated that the excimer laser technology resulted in limb salvage rates >90% in patients with critical limb ischemia (CLI). Furthermore, new clinical results indicate that the excimer laser is very effective in dissolving thrombotic obstructions, redirecting this technology to the coronary field. The results of the excimer laser in CLI validate the role of the cool laser in treating complex peripheral vascular disease. The results suggest a larger indication for this technology and support a more aggressive use of these interventional techniques in the treatment of this large patient cohort. However, all lasers are not equally effective in debulking atherosclerotic material. Only the athermic process associated with the excimer laser produces a safe and effective endovascular ablation of obstructive atherosclerotic and/or thrombotic material. The appropriate and safe utilization of the equipment and lasing techniques, combined with correct indications and

  13. Excimer laser ceramic and metal surface alloying applications

    NASA Astrophysics Data System (ADS)

    Hontzopoulos, E.; Zervaki, A.; Zergioti, Y.; Hourdakis, G.; Raptakis, E.; Giannacopoulos, A.; Fotakis, C.

    1991-02-01

    Recent excimer laser based deposition and surface modification techniques for ceramic and metallurgical engineering applications are reported. These include the improvement of the anti-corrosion and erosion properties and wear resistance of metal alloys and the formation of surface conducting patterns on ceramic materials. Excimer laser chemical vapour deposition (LCVD) applications B, AI and Hf or multielement combinations are discussed together with studies which aim at a better understanding of the fundamental processes governing the deposition process.

  14. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

  15. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1986-10-01

    We have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reaction cell. Spark schileren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect. Modelling studies of the ignition process aid in the interpretation of the experimental results, and show that the ignition we observe is not due solely to thermal effects, but is strongly dependent on the number and type of radicals present initially after photolysis. Ignition using other hydocarbons as fuels was also demonstrated. 30 refs., 9 figs. 2 tabs.

  16. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1986-01-01

    The authors have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reaction cell. Spark schlieren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect. Modelling studies of the igniton process aid in the interpretation of the experimental results, and show that the ignition is not due solely to thermal effects, but is strongly dependent on the number and type of radicals present initially after photolysis. Ignition using other hydrocarbons as fuels was also demonstrated.

  17. Excimer laser ablation of the lens.

    PubMed

    Nanevicz, T M; Prince, M R; Gawande, A A; Puliafito, C A

    1986-12-01

    Ablation of the bovine crystalline lens was studied using radiation from an excimer laser at four ultraviolet wave lengths as follows: 193 nm (argon fluoride), 248 nm (krypton fluoride), 308 nm (xenon chloride), and 351 nm (xenon fluoride). The ablation process was quantitated by measuring mass ablated with an electronic balance, and characterized by examining ablation craters with scanning electron microscopy. The highest ablation rate was observed at 248 nm with lower rates at 193 and 308 nm. No ablation was observed at 351 nm. Scanning electron microscopy revealed the smoothest craters at 193 nm while at 248 nm there was vacuolization in the crater walls and greater disruption of surrounding tissue. The craters made at 308 nm did not have as smooth a contour as the 193-nm lesions. The spectral absorbance of the bovine lens was calculated at the wavelengths used for ablation and correlated with ablation rates and thresholds. High peak-power, pulsed ultraviolet laser radiation may have a role in surgical removal of the lens. PMID:3789982

  18. Matrix metalloproteinase expression in excimer laser wounded rabbit corneas

    NASA Astrophysics Data System (ADS)

    Hahn, Taewon; Chamon, Wallace; Akova, Yonja; Stark, Walter J.; Stetler-Stevenson, William G.; Azar, Dimitri T.

    1994-06-01

    This study was performed to obtain information about matrix metalloproteinase (MMP) expression in excimer-wounded corneas and to determine whether MMPs expression correlates with the depth of the ablation. 6-mm excimer keratectomy (60 or 180 micrometers ) was performed using the 193-mm ArF excimer laser on 12 NZW rabbits. Corneas treated with mechanical epithelial debridement and untreated corneas served as controls. Rabbits were killed at 20 and 30 hr after laser ablation. Zymography after SDS extraction was performed on regenerated central epithelium and the central stroma to determine MMPs expression. We observed enzymatic activity of a 92 KDa band in the epithelium of excimer-ablated corneas but not in that following debridement wounds and untreated controls. The expression of the 92 KDa MMP was most pronounced with the deeper excimer ablation. A 72 KDa band of enzymatic activity present in the stroma of all treated and control eyes was also seen in the epithelium of excimer-ablated corneas. These proteolytic enzymes may play an important role in wound healing and remodelling after excimer keratectomy.

  19. The Excimer Laser: Its Impact on Science and Industry

    NASA Astrophysics Data System (ADS)

    Basting, Dirk

    2010-03-01

    After the laser was demonstrated in 1960, 15 years were required to develop a practical method for extending laser emission into the UV: the Excimer laser. This historical review will describe the challenges with the new medium and provide an insight into the technological achievements. In the transition from Science to Industry it will be shown how start-ups successfully commercialized laboratory prototypes. The pioneers in this rapidly expanding field will be identified and the influence of government-funded research as well as the role of venture capital will be discussed. In scientific applications, the fields of photochemistry and material research were particularly stimulated by the advent of a reliable UV light source. Numerous industrial applications and worldwide research in novel applications were fueled In the early and mid 80's by progress in excimer laser performance and technology. The discovery of ablative photocomposition of polymer materials by Srinivasan at IBM opened the door to a multitude of important excimer applications. Micromachining with extreme precision with an excimer laser enabled the success of the inkjet printer business. Biological materials such as the human cornea can also be ``machined'' at 193nm, as proposed in 1983 by Trokel and Srinivasan. This provided the foundation of a new medical technology and an industry relying on the excimer laser to perform refractive surgery to correct vision Today, by far the largest use of the excimer laser is in photolithography to manufacture semiconductor chips, an application discovered by Jain at IBM in the early 80's. Moore's law of shrinking the size of the structure to multiply the number of transistors on a chip could not have held true for so long without the deep UV excimer laser as a light source. The presentation will conclude with comments on the most recent applications and latest market trends.

  20. Excimer Laser Surface Treatment Of Non-Ferrous Alloys

    NASA Astrophysics Data System (ADS)

    Georgiopoulos, Michael; Hontzopoulos, Elias I.; Fotakis, Costas; Tsipas, D. N.; Floros, T.

    1989-04-01

    Excimer laser (KrF, ArF) radiation has been used for the surface modification of Al - Si and Ni alloys with the aim to improve their corrosion-errosion and hardness properties. A variety of experimental techniques including direct laser surface treatment and laser assisted chemical vapour deposition (CVD) have been employed and the parameters for process optimization have been determined.

  1. Surface treatment of metals with excimer and CO2 lasers

    NASA Astrophysics Data System (ADS)

    Haidemenopoulos, G. N.; Zervaki, A.; Papadimitriou, K.; Tsipas, D. N.; McIntosh, J.; Zergioti, G.; Manousaki, G.; Hontzopoulos, Elias I.

    1993-05-01

    The availability of a variety of lasers including the high-power cw CO2 lasers, the pulsed- mode infrared Nd-YAG, and the pulsed-mode ultraviolet excimer laser has led to the development of many interesting applications of laser technology to materials processing. Among them the surface modification of metallic alloys appears to be one of the most important and very close to implementation in various industries. Specifically the applications of excimer lasers have been discussed in a recent workshop in the framework of the Eureka EU 205 program. The major topics concerned with surface modifications that were discussed in this workshop were surface smoothing and roughening, surface cleaning of Ti and Cu, mixing and interdiffusion of predeposited layers, surface irradiation of Cu-alloys to improve the corrosion resistance, surface remelting of Al-alloys for grain refinement through rapid solidification, and surface remelting of Ni-P electroless coatings on Al alloys for the improvement of corrosion resistance. Laser alloying of Ni-base superalloys has also been discussed. Applications discussed here include the surface treatment of Ni-base superalloys with high-power CO2 laser, the surface treatment of aluminum alloys with excimer lasers, the laser assisted chemical vapor deposition (LCVD) of wear and corrosion resistant layers of Ti, TiC, and TiN on tool steels, and the fracture surface sulphur printing with excimer lasers.

  2. Development status of a 157-nm full-field scanner

    NASA Astrophysics Data System (ADS)

    Nakano, Hitoshi; Hata, Hideo; Nogawa, Hideki; Deguchi, Nobuyoshi; Kohno, Michio; Chiba, Yuji

    2003-06-01

    157 nm lithography has made further progress over the past year, steadily advancing towards the realization of the 65 nm era. In particular, exposure tools have moved on to the assembly phase, with new functions and performance now under evaluation. This paper presents our technical progress in our 157nm full field exposure tool, focusing on two key technologies: projection optics and environmental control with highly purified gasses. The high NA projection optics were designed to meet accelerating demands for smaller geometries. A catadioptric system with a line-selected laser was chosen to solve the problem of chromatic aberrations. The birefringence effect caused by CaF2 has been reduced to acceptable levels by clocking and combining <111> and <100> oriented crystals. Polishing and optical coatings consisting of glass materials were completed at targeted accuracy. At the present time, assembly and tuning of the projection optics is being performed. A simulation based on the inspection data from each production step predicts that the desired image performance will be attained. The total efficiency of the exposure system is expected to be higher than previously announced, due to the improvement of both CaF2 transmittance and AR/HR coatings. One of two keys issues in environmental control is to purge the projection optics which are permanently sealed. Purging performance was tested using a mockup of the projection optics. The second issue is to purge the areas around reticles and wafers which are continually carried into and out of the exposure system. Using the actual platform, the wafer and reticle purging performance was evaluated. It has been demonstrated that both of our purging systems are effective in keeping the environment at minimum contamination levels. This contributes to the increase of throughput.

  3. Overview on the high power excimer laser technology

    NASA Astrophysics Data System (ADS)

    Liu, Jingru

    2013-05-01

    High power excimer laser has essential applications in the fields of high energy density physics, inertial fusion energy and industry owing to its advantages such as short wavelength, high gain, wide bandwidth, energy scalable and repetition operating ability. This overview is aimed at an introduction and evaluation of enormous endeavor of the international high power excimer laser community in the last 30 years. The main technologies of high power excimer laser are reviewed, which include the pumping source technology, angular multiplexing and pulse compressing, beam-smoothing and homogenous irradiation, high efficiency and repetitive operation et al. A high power XeCl laser system developed in NINT of China is described in detail.

  4. Numbers Of Merit In Excimer Laser Reliability Analysis

    NASA Astrophysics Data System (ADS)

    Austin, Lindsay; Basting, Dirk; Kahlert, Hans-Jurgen; Rebhan, Ulrich; Muckenheim, Wolfgang

    1989-04-01

    Recent results confirm new advances in XeC1 excimer laser discharge design have achieved major milestones in reliability - 1010 pulses without replacing the thyratron, electrodes, capacitors or power supply. Other data on standard KrF excimer lasers allow statistical analysis of numbers of merit, including MTBF and maintenance intervals. Projections are made of operating costs and maintenance for both continuous operation and low duty cycle of two different size lasers with all major gases: XeCl, KrF and ArF.

  5. Excimer laser interaction with dentin of the human tooth

    NASA Technical Reports Server (NTRS)

    Hammond, Ernest C., Jr.; Gilliam, Ruth L.; Baker, George R.

    1989-01-01

    The use an excimer laser produced many unusual conical structures within the dentin of the inner part of the human tooth. By varying the frequency of the laser one can disperse the energy and cause more bleeding in laser surgery, but not destroy the cells associated with the incision. Therefore, the healing process will virtually be without scarring. Whereas, using the infrared laser the blood loss would be less, but the healing process would tend to be longer because cells are being destroyed due to the cauterization effect of the laser. The question is, are these structures produced as an interaction with the laser or are they an intrinsic part of the structure. The effects of the laser interaction upon dentin was studied, and in using electron microscopy the interaction of the excimer laser upon the tooth dentin and other various biological tissue is more clearly understood.

  6. Excimer laser processing of backside-illuminated CCDS

    NASA Technical Reports Server (NTRS)

    Russell, S. D.

    1993-01-01

    An excimer laser is used to activate previously implanted dopants on the backside of a backside-illuminated CCD. The controlled ion implantation of the backside and subsequent thin layer heating and recrystallization by the short wavelength pulsed excimer laser simultaneously activates the dopant and anneals out implant damage. This improves the dark current response, repairs defective pixels and improves spectral response. This process heats a very thin layer of the material to high temperatures on a nanosecond time scale while the bulk of the delicate CCD substrate remains at low temperature. Excimer laser processing backside-illuminated CCD's enables salvage and utilization of otherwise nonfunctional components by bringing their dark current response to within an acceptable range. This process is particularly useful for solid state imaging detectors used in commercial, scientific and government applications requiring a wide spectral response and low light level detection.

  7. Cleaning of large area by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Sentis, Marc L.; Delaporte, Philippe C.; Marine, Wladimir I.; Uteza, Olivier P.

    2000-01-01

    Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser, beam deliver, particle collection cell, real time control of cleaning processes. Results concerning surface laser interaction and substrate modifications are presented.

  8. Pulsed excimer laser processing for cost-effective solar cells

    NASA Technical Reports Server (NTRS)

    Wong, David C.

    1985-01-01

    The application of excimer laser in the fabrication of photovoltaic devices was investigated extensively. Processes included junction formation, laser assisted chemical vapor deposition metallization, and laser assisted chemical vapor deposition surface passivation. Results demonstrated that implementation of junction formation by laser annealing in production is feasible because of excellent control in junction depth and quality. Both metallization and surface passivation, however, were found impractical to be considered for manufacturing at this stage.

  9. Advances in 193 nm excimer lasers for mass spectrometry applications

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph; Esser, Hans-Gerd; Bonati, Guido

    2016-03-01

    Ongoing progress in mass analysis applications such as laser ablation inductively coupled mass spectrometry of solid samples and ultraviolet photoionization mediated sequencing of peptides and proteins is to a large extent driven by ultrashort wavelength excimer lasers at 193 nm. This paper will introduce the latest improvements achieved in the development of compact high repetition rate excimer lasers and elaborate on the impact on mass spectrometry instrumentation. Various performance and lifetime measurements obtained in a long-term endurance test over the course of 18 months will be shown and discussed in view of the laser source requirements of different mass spectrometry tasks. These sampling type applications are served by excimer lasers delivering pulsed 193 nm output of several mJ as well as fast repetition rates which are already approaching one Kilohertz. In order to open up the pathway from the laboratory to broader market industrial use, sufficient component lifetimes and long-term stable performance behavior have to be ensured. The obtained long-term results which will be presented are based on diverse 193 nm excimer laser tube improvements aiming at e.g. optimizing the gas flow dynamics and have extended the operational life the laser tube for the first time over several billion pulses even under high duty-cycle conditions.

  10. Analytical Characterization of CFRP Laser Treated by Excimer Laser Radiation

    NASA Astrophysics Data System (ADS)

    Kreling, S.; Fischer, F.; Delmdahl, R.; Gäbler, F.; Dilger, K.

    Due to the increasing interest in lightweight structures, carbon-fiber reinforced plastics are increasingly applied, especially in the transportation industry. An interesting technology for joining these materials is adhesive bonding due to numerous advantages compared to conventional techniques like riveting. However, to achieve a strong and durable bond, surface pre-treatment is necessary to remove residues of release agents that are transferred to the surface during manufacturing. This paper describes analytical experiments, namely SEM and XPS, performed on CFRP surfaces pre-treated with 308 nm excimer laser radiation.

  11. Improved corrosion resistance of excimer laser treated stainless steel

    NASA Astrophysics Data System (ADS)

    Emmel, A.; Schubert, Emil; Barnikel, J.; Stiele, H. J.; Bergmann, Hans W.

    1994-09-01

    Excimer laser surface processing is well-known for material ablation, cleaning, deoxidation, smoothing or roughening. A typical industrial application is the polymer ablation for electronic components, however, the treatment of metals is only on the threshold of industrial use. A novel application reported here, may be an excimer treatment in air leading to oxide and nitrogen dissolution, resulting in an improved corrosion resistance. It is known from literature that corrosion resistance can be enhanced by laser surface alloying e.g. gas nitriding of Ti using CO2-lasers. However, all these techniques have the disadvantage of producing inhomogeneous layers. The aim of this study was to use the reactions during excimer laser irradiation of steel in air to produce layers in the thickness range of 0,1 to 2 micrometers with novel properties. Using the Siemens XP2020 excimer laser it was possible to scan technologically reasonable surface areas with energy densities in the range of 20 to 80 mJ/mm2 and several pulses per area. Steel sheets of 1.4541 (DIN) were irradiated in air and subsequently analyzed by XRD, SEM, TEM, AES and Mossbauer spectroscopy. The corrosion behavior was tested potentio-dynamically in 0,5 N H2SO4 and by gravimetric measurements of the weight loss. The XRD results showed, that the remaining delta-ferrite was eliminated. Both Mossbauer and Auger spectroscopy indicated a strong N- dissolution, hereby stabilizing the austenite. The TEM-investigations revealed fine dispersed oxides (chromites) and an increased dislocation density, resulting in pre-cellular arrangements after relaxation. Corrosion tests suggested the reduction of the material removal rates by a factor of 10 compared to untreated samples. The U(i) curves showed that after the excimer treatment less Cr is presented due to oxide formation in the surface layer. These Cr-oxides are the main reason for the improved corrosion resistance of excimer laser treated stainless steel.

  12. Generation of strongly coupled plasmas by high power excimer laser

    NASA Astrophysics Data System (ADS)

    Zhu, Yongxiang; Liu, Jingru; Zhang, Yongsheng; Hu, Yun; Zhang, Jiyan; Zheng, Zhijian; Ye, Xisheng

    2013-05-01

    (ultraviolet). To generate strongly coupled plasmas (SCP) by high power excimer laser, an Au-CH-Al-CH target is used to make the Al sample reach the state of SCP, in which the Au layer transforms laser energy to X-ray that heating the sample by volume and the CH layers provides necessary constraints. With aid of the MULTI-1D code, we calculate the state of the Al sample and its relationship with peak intensity, width and wavelength of laser pulses. The calculated results suggest that an excimer laser with peak intensity of the magnitude of 1013W/cm2 and pulse width being 5ns - 10ns is suitable to generate SCP with the temperature being tens of eV and the density of electron being of the order of 1022/cm-3. Lasers with shorter wavelength, such as KrF laser, are preferable.

  13. Laser plume dynamics during excimer laser nitriding of iron

    NASA Astrophysics Data System (ADS)

    Han, M.; Carpene, E.; Lieb, K. P.; Schaaf, Peter

    2003-11-01

    Laser nitriding of iron is an interesting phenomenon both in physics and industry. On the time scale of hundreds nanoseconds, high intensity (~108 W/cm2) pulsed excimer laser irradiation on iron in nitrogen atmosphere produced a thin iron nitride layer (thickness > 400 nm) with a mean nitrogen concentration exceeding 10 at which greatly improves the iron surface mechanical properties and the corrosion or erosion resistance. Laser plasma/plume plays a crucial role in the complicated interplay of the laser-plasma-metal system. Since the nitrogen pressure is one of the most important parameters determining the laser plume dynamics, a nitrogen pressure series ranging from 0.05 bar to 10 bar is conducted. The characteristic parameters of the nitrogen depth profile are extracted and their pressure dependence is qualitatively discussed. By isotopic experiments in 15N and natural nitrogen environment, the evolution of the nitrogen depth profile during laser nitriding process is successfully traced. Both of the experimental results suggested that a 1D laser supported combustion wave model is reasonable to describe the lasers plume dynamics.

  14. Novel technique for high-quality microstructuring with excimer lasers

    NASA Astrophysics Data System (ADS)

    Roth, Stephan; Geiger, Manfred

    2000-06-01

    Laser micromachining has become increasingly established in many microsystem applications during the past years. These new fields occasion higher demands on the quality of micromachiend devices combined with high resolution and working velocity. Due to the disadvantages of conventional excimer laser processing, a novel technique is required to meet these demands. The main problems of conventional excimer laser machining are the redeposition of ablated material on the irradiated work piece and the formation of a strong melting phase especially for metals. These difficulties greatly reduce the applicability of excimer laser material processing for manufacturing microsystems technology components. By applying a thin water film to the substrate surface, the redeposition of ablated material can be completely avoided, which results in a better quality of the microstructures. Usage of a water film, however, has proved to lead to a marked reduction of the ablation rate for the examined materials - ceramics and stainless steel. Therefore, one of the objectives of future research will be to raise the ablation rate in order to render excimer laser processing more interesting economically. Adding alcoholic additives, among others, has improved the wetting of the liquid films on the surface. The effect of the modified chemical composition of the liquid on ablation rate and structure quality for various materials is presented here.

  15. Excimer laser ablation of polymer-clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Chang, I.-Ta

    The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this work. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration. The excimer laser induced surface micro/nano structure formation and modification of PS-Clay Nanocomposites at various OMMT concentrations were also investigated. Scanning electron microscopy, atomic force microscopy and Fourier Transform Infrared (FTIR) spectroscopy with attenuated total reflectance accessory were utilized to analyze the ablated surface. Results show that, in general, better dispersion of OMMT leads to less continuous surface structures and more pronounced carbonyl regions on FTIR spectra. Clay nanoparticles are exposed on ablated surfaces and affect surface structure formation after irradiation by laser. A mechanism for the formation of excimer laser induced surface structures on injection molded parts is thus proposed.

  16. Boron trichloride purification with a KrF excimer laser

    SciTech Connect

    Hyer, R.C.; Hartford, A. Jr.; Atencio, J.H.

    1980-01-01

    Selective ultraviolet photolysis using a KrF excimer laser has been used to substantially reduce the phosgene impurity in a binary mixture of boron trichloride and phosgene. Infrared spectroscopic analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this technique.

  17. Analysis of glycosaminoglycans in rabbit cornea after excimer laser keratectomy

    PubMed Central

    Kato, T.; Nakayasu, K.; Ikegami, K.; Obara, T.; Kanayama, T.; Kanai, A.

    1999-01-01

    BACKGROUND/AIMS—The biochemical basis for the development of subepithelial opacity of the cornea after excimer laser keratectomy has yet to be fully defined. The aim of this study was to evaluate the alterations of glycosaminoglycans (GAGs) after excimer laser keratectomy.
METHODS—Rabbit corneas were harvested on days 5, 10, 20, and 30 after excimer laser photoablation. The amount of main disaccharide units was determined by high performance liquid chromatography (HPLC). In addition, immunohistochemical studies were performed on corneal sections 20 days after the ablation.
RESULTS—The concentrations of ΔDi-0S at 5 and 10 days were significantly lower than before the ablation. ΔDi-6S showed a significant increase 5 days after the ablation but ΔDi-4S did not show any significant change. There was a significant increase in ΔDi-HA at 20 and 30 days after ablation. In immunohistochemistry, the positive staining for ΔDi-6S and hyaluronic acid was observed in the subepithelial region. These immunohistochemical results were well correlated with the HPLC findings.
CONCLUSIONS—The increase in chondroitin-6 sulphate and hyaluronic acid may be related to corneal subepithelial opacity after excimer laser keratectomy.

 PMID:10216064

  18. Excimer laser lead extraction catheter with increased laser parameters

    NASA Astrophysics Data System (ADS)

    Coe, M. Sean; Taylor, Kevin D.; Lippincott, Rebecca A.; Sorokoumov, Oleg; Papaioannou, Thanassis

    2001-05-01

    A fiber optic catheter connected to a pulsed excimer laser (308 nm) is currently used to extract chronically implanted pacemaker and defibrillator leads at Fluence of 60 mJ/mm2 and repetition rate of 40 Hz. The object of this study was to determine the effect of higher repetition rates (80 Hz) in the catheter's cutting performance. The penetration rate (micrometers /sec), and the associated mechanical and thermal effects were measured in soft (porcine myocardium) and hard tissue (bovine tendon) at 60 mJ/mm2-80 Hz, and were compared to the corresponding values at commercially available laser parameters (60 mJ/mm2-40 Hz). Ablation rates were measured with perforation experiments and the extent of thermal and mechanical damage was measured under polarized light microscopy. For hard (soft) tissue, the laser catheter demonstrated penetration speed of 106 +/- 32 (302 +/- 101) micrometers /sec at 40 Hz and 343 +/- 120 (830 +/- 364) micrometers /sec at 80 Hz. Maximum extent of thermal effects at 40 Hz and 80 Hz was 114 +/- 35 micrometers (72 +/- 18) and 233 +/- 63 micrometers (71 +/- 16) respectively. Maximum extent of mechanical effects at 40 Hz and 80 Hz was 188 +/- 63 micrometers (590 +/- 237) and 386 +/- 100 micrometers (767 +/- 160) respectively. In vitro testing of the laser catheter with 80 Hz laser parameters has demonstrated increased penetration speed in both soft and hard fibrous tissue, while maintaining associated thermal and mechanical effects within limited ranges.

  19. Excimer laser ophthalmic surgery: evaluation of a new technology.

    PubMed Central

    Infeld, D. A.; O'Shea, J. G.

    1998-01-01

    The aim of this article is to provide information and an overview of the potential risks and benefits of excimer laser surgery, a new and promising technique in ophthalmic surgery. Although this review concentrates on the use of the laser for refractive purposes, novel therapeutic techniques are also discussed. It is hoped that this will enable general practitioners, optometrists and physicians to provide appropriate advice and counselling for patients. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:10211324

  20. Excimer Laser Ablation of Egg Tempera Paints and Varnishes

    NASA Astrophysics Data System (ADS)

    Morais, P. J.; Bordalo, R.; Santos, L. dos; Marques, S. F.; Salgueiredo, E.; Gouveia, H.

    In this work a series of egg tempera paint and varnish systems have been prepared, artificially aged and irradiated with KrF excimer laser at a wavelength of 248 nm. The samples were prepared with pure pigments and selected mixtures. It was found that, for some pigments, the colour changed upon laser irradiation even at low energy densities, below the ablation threshold while for other inorganic pigmented egg temperas the degree of discoloration is very small at moderate fluence of ˜0.30 J cm?2. The varnish systems did not present signs of discoloration. The thickness, superficial roughness and magnitude of the colour changes of the samples were measured. X-ray diffraction, Raman spectroscopy and UV/visible spectroscopy were used in order to investigate the changes induced by the KrF excimer laser radiation.

  1. Excimer laser coronary angioplasty: relative risk analysis of clinical results

    NASA Astrophysics Data System (ADS)

    Bittl, John A.

    1992-08-01

    Reports of successful use of excimer laser coronary angioplasty for complex coronary artery disease abound, yet firm indications for its use have not been defined. We attempted to treat 858 coronary stenoses in 764 consecutive patients (mean age 61 years; range 32 - 91 years; 75% men; 76% with Class III or IV angina) with excimer laser angioplasty at 308 nm. Successful treatment was achieved in 86% of patients, as indicated by excimer laser angioplasty, we used relative risk analysis. This showed that certain angiographic features, such as lesions at a vessel bifurcation (odds ratio, OR equals 0.46; 95% confidence interval 0.23, 0.88; P equals 0.017;) or in a tortuous segment (OR equals 0.54; 95% CI equals 0.34, 0.88; P equals 0.041), have decreased likelihood of clinical success. On the other hand, ostial stenoses (OR equals 1.06; 95% CI equals 0.44, 2.56, P equals 0.903) and saphenous vein graft lesions (OR equals 2.17; 95% CI equals 0.98, 4.82; P equals 0.051) have acceptable success rates. Diffuse disease (> 20 mm), total occlusions and calcified lesions were treated as successfully as all other lesion types. Successful treatment with excimer laser coronary angioplasty was also achieved in almost all patients (15/16) who had a prior unsuccessful attempt at balloon angioplasty in the lesion was crossed with a guidewire yet resists either balloon catheter passage or full dilatation. Follow-up angiography was obtained in 70% of eligible patients. Angiographic restenosis, defined by > 50% stenosis, was seen in 60% of patients. Relative risk analysis showed an increased risk of restenosis when adjunctive balloon angioplasty was not used (OR equals 1.68; 95% CI equals 1.02, 2.28; P equals 0.039). Other variables known to affect the outcome of balloon angioplasty, such as lesion length or stenosis in degenerated saphenous vein bypass graft, did not influence the

  2. Triggering Excimer Lasers by Photoionization from Corona Discharges

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  3. Nebulae at keratoconus--the result after excimer laser removal.

    PubMed

    Fagerholm, P; Fitzsimmons, T; Ohman, L; Orndahl, M

    1993-12-01

    Ten patients underwent excimer laser ablation due to nebula formation at keratoconus. The nebulae interfered significantly with contact lens fit or wearing time. The mean follow-up time in these patients was 16.5 months. Following surgery all patients could be successfully fitted with a contact lens and thereby obtain good visual acuity. Furthermore, contact lens wearing time was 8 hours or more in all cases. In 2 patients the nebulae recurred but were successfully retreated. PMID:8154261

  4. 308-nm Excimer laser treatment of palmoplantar psoriasis.

    PubMed

    Goldberg, David J; Chwalek, Jennifer; Hussain, Mussarrat

    2011-04-01

    Psoriasis is a chronic inflammatory condition affecting 1-3% of the population. The incidence of palmoplantar involvement has been estimated to be between 2.8% and 40.9%. Significant psychosocial distress and difficulty performing activities of daily living can result. Treatment is often challenging. Traditional treatments include topical steroids, anthralin, calcipotriene, PUVA, methotrexate, cyclosporine, retinoids and biologics. In this case series, we report our success with the 308-nm excimer laser in the treatment of palmoplantar psoriasis. PMID:21401376

  5. Assessment of the Suitability of Excimer Lasers in Treating Onychomycosis

    NASA Astrophysics Data System (ADS)

    Kymplová, Jaroslava; Jelínek, Miroslav; Urzová, Jana; Mikšovský, Jan; Dušek, Karel; Bauerová, Lenka

    2014-04-01

    Since it is known that UV-C radiation kills fungus, we wanted to verify the hypothesis that the use of excimer laser could be an alternative method for treating onychomycosis - nail fungus. The aim of the first stage of this work was to determine the transmission, reflection and absorption of nails. In the following stage we focused on irradiation of fungi. Our final task is to assess whether it is possible to determine the parameters of radiation (a total dose,a dose per pulse frequency, a repetition rate, a number of pulses) for which the elimination of fungi would be the most effective but without damaging the nail and soft tissue underneath it. The results so far have showed that UV-C radiation does not pass through a fingernail to such an extent that it could damage the soft tissue beneath it. Fungi are destroyed by the application of only small doses of radiation using the excimer laser. Additional measurements will be required to determine the modulation parameters of the excimer laser radiation for the treatment of onychomycosis.

  6. Automatic alignment of double optical paths in excimer laser amplifier

    NASA Astrophysics Data System (ADS)

    Wang, Dahui; Zhao, Xueqing; Hua, Hengqi; Zhang, Yongsheng; Hu, Yun; Yi, Aiping; Zhao, Jun

    2013-05-01

    A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63μrad and the beam maximum restoration error is 13.75μm. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.

  7. Surface Structuring of CFRP by using Modern Excimer Laser Sources

    NASA Astrophysics Data System (ADS)

    Fischer, F.; Kreling, S.; Dilger, K.

    High demands for lightweight construction can be attained by the use of carbon fiber-reinforced plastics (CFRP) including one major challenge: the joining technology. Adhesive bonding may allow an increased utilization of the lightweight potential of CFRP. But this technology requires a surface pre-treatment because of residues of release agents. This paper describes surface pre-treatment of CFRP specimens by using modern excimer laser and the mechanical tests that compare the achieved strength to manually abraded ones. The laser process is suitable for achieving cohesive failure within the adhesive and bond strengths in the magnitude of the abraded specimen.

  8. Chemical surface modification of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1996-04-01

    Surface of poly(tetrafluoroethylene) [PTFE] film was modified chemically by an ArF excimer laser-induced reaction in a hydrazine gas atmosphere. The polymer surface modified upon the irradiation of 1000 pulses at 27 mJ cm -2, which was a fairly lower fluence than the ablation threshold for usual polymer films, showed hydrophilicity (contact angle for water: 30°) enough to be metallized by chemical plating. The mechanism for chemical surface modification was investigated by FTIR, XPS, and SIMS analyses. The laser-treated PTFE film was metallized by a chemical plating process. These processes will be used to fabricate printed wiring boards for high frequency electronics.

  9. Pixel diamond detectors for excimer laser beam diagnostics

    NASA Astrophysics Data System (ADS)

    Girolami, M.; Allegrini, P.; Conte, G.; Salvatori, S.

    2011-05-01

    Laser beam profiling technology in the UV spectrum of light is evolving with the increase of excimer lasers and lamps applications, that span from lithography for VLSI circuits to eye surgery. The development of a beam-profiler, able to capture the excimer laser single pulse and process the acquired pixel current signals in the time period between each pulse, is mandatory for such applications. 1D and 2D array detectors have been realized on polycrystalline CVD diamond specimens. The fast diamond photoresponse, in the ns time regime, suggests the suitability of such devices for fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV beam diagnostics, also under high intensity background illumination. Offering unique properties in terms of thermal conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of high-power UV laser emission. The relatively high resistivity of diamond in the dark has allowed the fabrication of photoconductive vertical pixel-detectors. A semitransparent light-receiving back-side contact has been used for detector biasing. Each pixel signal has been conditioned by a multi-channel read-out electronics made up of a high-sensitive integrator and a Σ-Δ A/D converter. The 500 μs conversion time has allowed a data acquisition rate up to 2 kSPS (Sample Per Second).

  10. Histological study of excimer laser on carotid artery

    NASA Astrophysics Data System (ADS)

    Chavantes, Maria C.; Pasqualucci, C. A.; Zamorano, Lucia J.

    1992-06-01

    The employment of photoablative effect on coronary artery angioplasty has been a new exciting field as a treatment option. Guided by good results in the literature, our group decided to study the laser/tissue interaction on carotid arteries with the intent of a less invasive treatment of intracranial and extracranial obstructed disease in vascular neurosurgery. We studied human cartoid arteries from ten male autopsy specimens with an average age of 53 years (34 - 37 years old) which a total of 22 laser applications were performed. Using the same repetition rate and energy, 20 Hz and 30 mJ, we compared the effect of the laser energy on 'normal' and 'pathologic' areas of the carotid arteries. The pathologic specimens, presenting calcified and non-calcified plaques, the same as the macroscopical 'normal' specimens, were submitted to the energy of the Excimer Laser with 308 nm wavelength. The laser beam was delivered perpendicularly through continuous flushing of saline on the targeted artery wall varying from 200 to 400 pulses. Histological studies were done and statistical analysis was performed. The results showed that the depth of penetration varied from 113 micrometers to 1200 micrometers , with a width of the lesion ranging from 150 micrometers - 1500 micrometers . In our study we found that the range between non-effective and destructive effect caused by the laser was around 400 pulses. We encountered minimal degree of carbonization while lasering on calcified plaques. We concluded that Excimer laser is a feasible and secure tool to prevent thermical complications of laser treatment, which will allow neurosurgeons in the future athermic laser angioplasty. Progress in this field must rely on further in vitro and in vivo research, before it can be clinically applied as well as improvements in delivery systems.

  11. Three years of clinical experiences on excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Viligiardi, Riccardo; Galiberti, Sandra; Pini, Roberto; Salimbeni, Renzo

    1992-03-01

    We report here the experience of our multidisciplinary group that has been working since 1986 on excimer laser angioplasty. After having selected the excimer laser between the available sources because of the negligible lesions left on the residual tissue, we had the purpose to develop a suitable laser and catheter system. Neglecting here all the preliminary studies, we outline only a typical phenomenon related to the energy delivery and useful for the comprehension of the recanalization process. The energy emitted by every single fiber determines, under a certain threshold, independent recanalized channels in the plaque with residual flaps. At a higher energy level the overposition of the lobes, due to the intrinsic divergence, up to the recanalization in a single large channel. In our opinion this condition is crucial in the design of the catheters to obtain an optical instead of a mechanical recanalization. The biological experimentation conducted during the preliminary tests on human hearts obtained from transplants or cadavers, convinced us that the correct goal to pursue was unique laser angioplasty without the need for further balloon dilation.

  12. Applications of the 308-nm excimer laser in dermatology

    NASA Astrophysics Data System (ADS)

    Farkas, A.; Kemeny, L.

    2006-05-01

    Excimer lasers contain a mixture of a noble inert gas and a halogen, which form excited dimers only in the activated state. High-energy current is used to produce these dimers, which have a very short lifetime, and after their fast dissociation they release the excitation energy through ultraviolet photons. The application of these lasers proved to be successful in medicine, including the field of ophthalmology, cardiology, angiology, dentistry, orthopaedics, and, in recent years, dermatology. For medical purposes, the 193-nm argon fluoride, the 248-nm krypton fluoride, the 351-nm xenon fluoride, and the 308-nm xenon chloride lasers are used. Recently, the 308-nm xenon chloride laser has gained much attention as a very effective treatment modality in dermatological disorders. It was successfully utilized in psoriasis; later, it proved to be useful in handling other lightsensitive skin disorders and even in the treatment of allergic rhinitis. This review summarizes the possible applications of this promising tool in dermatology.

  13. Excimer laser superficial keratectomy for proud nebulae in keratoconus.

    PubMed

    Moodaley, L; Liu, C; Woodward, E G; O'Brart, D; Muir, M K; Buckley, R

    1994-06-01

    Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided. PMID:8060928

  14. Excimer laser photorefractive keratectomy with different ablation zones.

    PubMed

    Hassan, Z; Lampé, Z; Békési, L; Berta, A

    1997-01-01

    In this study we would like to introduce the excimer laser, and to demonstrate our results and complications by using different ablation zones during photorefractive keratectomy (PRK) in the correction of myopia and astigmatismus. In 1996 we performed photorefractive keratectomy on 100 myopic eyes of 52 patients (28 females, 24 males). Mean age was 26.21 years (ranged from 19 to 54 years). The preoperative refraction ranged from -1.0 D to -18.0 Diopters. The diameter of the ablation zones were between 5 and 6.5 mm. We evaluated the results and the complications of the surgeries of 100 eyes which were performed with Schwind keratom F excimer laser. After 2 days, 1 week, 1 month, 3 months, and 6 months postoperatively we tested the best uncorrected and corrected visual acuities, and performed intraocular pressure measurement, slit lamp examination as well as corneal topography. The postoperative refractions were between +/- 0.5 to +/- 1.0 Diopters. After six months postoperatively the slit lamp examination showed that 80% of the patients had no corneal haze while 20% had stage I (Hanna) corneal haze. The smaller the diameter of the ablation zone was, the more pronounced the corneal haze and the night-glare were. The photorefractive excimer laser keratectomy is judged to be a safe method, although it might have some side-effects. The different ablation zones of this treatment means an important modification, that not only allows the method to meet the individual requirements, but reduces the chance of the complications as well. Based on the authors' experiences PRK for moderate myopia with large diameter ablation zones appears more predictable than than with smaller ablation zone diameters. PMID:9408312

  15. Excimer laser superficial keratectomy for proud nebulae in keratoconus.

    PubMed Central

    Moodaley, L; Liu, C; Woodward, E G; O'Brart, D; Muir, M K; Buckley, R

    1994-01-01

    Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided. Images PMID:8060928

  16. Blunt atrial transseptal puncture using excimer laser in swine

    PubMed Central

    Elagha, Abdalla A.; Kim, Ann H.; Kocaturk, Ozgur; Lederman, Robert J.

    2009-01-01

    Objectives We describe a new approach that may enhance safety of atrial transseptal puncture, using a commercially available laser catheter that is capable of perforation only when energized. We test this approach in swine. Background Despite wide application, conventional needle transseptal puncture continues to risk inadvertent non-target perforation and its consequences. Methods We used a commercial excimer laser catheter (0.9mm Clirpath, Spectranetics). Perforation force was compared in vitro with a conventional Brockenbrough needle. Eight swine underwent laser transseptal puncture under X-ray fluoroscopy steered using a variety of delivery catheters. Results The 0.9mm laser catheter traversed in vitro targets with reduced force compared with a Brockenbrough needle. In vitro, the laser catheter created holes that were 25–30% larger than the Brockenbrough needle. Laser puncture of the atrial septum was successful and accurate in all animals, evidenced by oximetry, pressure, angiography, and necropsy. The laser catheter was steered effectively using a modified Mullins introducer sheath and using two different deflectable guiding catheters. The mean procedure time was 15 ± 6 minutes, with an average 3.0 ± 0.8 seconds of laser activation. There were no adverse sequelae after prolonged observation. Necropsy revealed discrete 0.9mm holes in all septae. Conclusion Laser puncture of the interatrial septum is feasible and safe in swine, using a blunt laser catheter that perforates tissues in a controlled fashion. PMID:17896413

  17. Multifiber excimer laser catheter design strategies for various medical applications

    NASA Astrophysics Data System (ADS)

    Verdaasdonck, Rudolf M.; van Swol, Christiaan F. P.; van Leeuwen, Ton G. J. M.; Tulleken, Cees A. F.; Boon, Tom A.

    1994-07-01

    For the XeCl Excimer laser (308 nm, 115 ns), special design multifiber laser catheters were developed and theoretically as well as experimentally evaluated. Monte Carlo simulations showed that the penetration depth of 308 nm XeCl excimer light varied from 50 to 200 micrometers for fiber diameters from 50 to 550 micrometers and larger. Tissue ablation is expected to be restricted to this irradiated area. In order to ablate larger tissue areas, a flexible bundle of fibers is used introducing gaps in the irradiance distribution due to dead space in between the individual fibers. Multifiber catheters were developed for a unique neurosurgery bypass procedure and for urethra stricture surgery. Real-time, close-up, high speed video imaging showed that tissue ablation mechanism of these catheters is predominately governed by explosive short-life vapor bubbles fragmenting the tissue to small particles. In order to temper the ablation process, laser energy was delivered in 8 pulses divided over 8 sectors of a multifiber catheter (multiplexing), keeping the same fluence instead of one pulse addressing all the fibers at once.

  18. Laser dentistry: A new application of excimer laser in root canal therapy

    SciTech Connect

    Pini, R.; Salimbeni, R.; Vannini, M.; Barone, R.; Clauser, C.

    1989-01-01

    We report the first study of the application of excimer lasers in dentistry for the treatment of dental root canals. High-energy ultraviolet (UV) radiation emitted by an XeCl excimer laser (308 nm) and delivered through suitable optical fibers can be used to remove residual organic tissue from the canals. To this aim, UV ablation thresholds of dental tissues have been measured, showing a preferential etching of infiltrated dentin in respect to healthy dentin, at laser fluences of 0.5-1.5 J/cm{sup 2}. This technique has been tested on extracted tooth samples, simulating a clinical procedure. Fibers of decreasing core diameters have been used to treat different sections of the root canal down to its apical portion, resulting in an effective, easy, and fast cleaning action. Possible advantages of excimer laser clinical applications in respect to usual procedures are also discussed.

  19. Excimer laser annealing to fabricate low cost solar cells

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The objective is to show whether or not pulsed excimer laser annealing (PELA) of ion-implanted junctions is a cost effective replacement for diffused junctions in fabricating crystalline silicon solar cells. The preliminary economic analysis completed shows that the use of PELA to fabricate both the front junction and back surface field (BSF) would cost approximately 35 cents per peak watt (Wp), compared to a cost of 15 cents/Wp for diffusion, aluminum BSF and an extra cleaning step in the baseline process. The cost advantage of the PELA process depends on improving the average cell efficiency from 14% to 16%, which would lower the overall cost of the module by about 15 cents/Wp. An optimized PELA process compatible with commercial production is to be developed, and increased cell efficiency with sufficient product for adequate statistical analysis demonstrated. An excimer laser annealing station was set-up and made operational. The first experiment used 248 nm radiation to anneal phosphorus implants in polished and texture-etched silicon.

  20. Excimer Laser Beam Analyzer Based on CVD Diamond

    NASA Astrophysics Data System (ADS)

    Girolami, Marco; Salvatori, Stefano; Conte, Gennaro

    2010-11-01

    1-D and 2-D detector arrays have been realized on CVD-diamond. The relatively high resistivity of diamond in the dark allowed the fabrication of photoconductive "sandwich" strip (1D) or pixel (2D) detectors: a semitransparent light-receiving back-side contact was used for detector biasing. Cross-talk between pixels was limited by using intermediate guard contacts connected at the same ground potential of the pixels. Each pixel photocurrent was conditioned by a read-out electronics composed by a high sensitive integrator and a Σ-Δ ADC converter. The overall 500 μs conversion time allowed a data acquisition rate up to 2 kSPS. The measured fast photoresponse of the samples in the ns time regime suggests to use the proposed devices for fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV beam diagnostics also under high intensity background illumination. Offering unique properties in terms of thermal conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of high-power UV laser emission. The technology of laser beam profiling is evolving with the increase of excimer lasers applications that span from laser-cutting to VLSI and MEMS technologies. Indeed, to improve emission performances, fine tuning of the laser cavity is required. In such a view, the development of a beam-profiler, able to work in real-time between each laser pulse, is mandatory.

  1. Boron distribution in silicon after multiple pulse excimer laser annealing

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-08-22

    We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10{sup 14} and 1x10{sup 15} cm{sup -2}. ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 deg. C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up.

  2. Laser excited fluorescence in the cesium-xenon excimer and the cesium dimer

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Snow, W. L.; Hillard, M. E.

    1978-01-01

    Argon ion laser lines are used to excite fluorescence in a mixture of cesium and xenon. Excimer band fluorescence is observed at higher pressures (about 1 atm) while at lower pressures (several torr) a diffuse fluorescence due to the cesium dimer is observed whose character changes with exciting wavelength. The excimer fluorescence is shown to be directly related to the location of the exciting wavelength within previously measured Cs/Xe line shapes. This fact suggests that the excimer systems may be efficiently pumped through these line shapes. Qualitative energy-level schemes are proposed to explain the observations in both the excimer and dimer systems.

  3. Nd:YAG laser cleaning of ablation debris from excimer-laser-ablated polyimide

    NASA Astrophysics Data System (ADS)

    Gu, Jianhui; Low, Jason; Lim, Puay K.; Lim, Pean

    2001-10-01

    In the processing of excimer laser ablation of nozzles on polyimide in air, both gases like CO2, CO and HCN and solid debris including C2 approximately C12 are produced in laser ablation area. In this paper, we reported for the first time a Nd:YAG laser cleaning of ablation debris generated in excimer laser ablation of polyimide. It demonstrated effective cleaning with the advantages of shortening cleaning cycle time and simplifying cleaning process. The laser used for the cleaning was a Q-switched and frequency doubled Nd:YAG laser with wavelength of 532 nm and repetition rate of 10 Hz. The laser cleaning effect was compared with conventional plasma ashing. AFM measurement showed that the Nd:YAG laser cleaning had no damage to the substrate. XPS results indicated that the polyimide surface cleaned with laser beam had a lower oxygen/carbon ratio than that of plasma ashing. The study shows that frequency doubled Nd:YAG laser cleaning is effective in ablation debris removal from excimer laser ablated polyimide.

  4. Encapsulated inorganic resist technology applied to 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Fedynyshyn, Theodore H.; Sinta, Roger F.; Sworin, Michael; Goodman, Russell B.; Doran, Scott P.; Sondi, I.; Matijevic, Egon

    2001-08-01

    In order to increase plasma etch selectivity in traditional single layer organic resists SiO2 nanoparticles have been added to typical 248nm resist formulations. Formulation modifications are necessary due to the dissolution acceleration effect of the particles. Surface functionalization of the nanoparticle surfaces with organic groups lessens this effect and allows the inclusion of acid labile groups. This allows for a wider formulation window and limits unexposed film thickness losses (UFTL). Both t- butyl ester groups and poly(t-butyl acrylate) have been used to achieve this effect. Encapsulated inorganic resist technology (EIRT) can be used as a single layer hard mask compatible with existing resist processing steps and replace complex and costly multilevel resist approaches. Lithogrpahic evaluations have been performed with electron beam, and with 248nm and 157nm projection systems. Greater transparency at 157nm is achieved by the addition of these materials, thus enabling the use of thicker films. High resolution imaging is demonstrated at these wavelengths.

  5. Evaluation of fluorinated dissolution inhibitors for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Hamad, Alyssandrea H.; Houlihan, Francis M.; Seger, Larry; Chang, Chun; Ober, Christopher K.

    2003-06-01

    Fluorinated diesters were synthesized and evaluated as dissolution inhibitors (DIs) for 157 nm lithography. The results of dissolution rate measurements, exposure studies, and etching experiments on blends of fluorinated polymers containing these dissolution inhibitors are reported. It was shown that the DIs effectively slow the dissolution rate of the matrix polymer, poly(hexafluorohydroxyisopropyl styrene) (PHFHIPS). Etching studies show that they enhance the plasma etch resistance of poly(methyl methacrylate) using tetrafluoromethane plasma. Addition of the best performing dissolution inhibitor, cyclohexane-1,4-dicarboxylic acid bis-(1-cyclohexyl-2,2,2-trifluoro-1-methyl-ethyl) ester) (FCDE1) to candidate 157 nm photoresist polymers, Duvcor and poly(hexafluorohydroxyisopropyl styrene)-co-poly(t-butyl methacrylate) [pPHFHIPS-co-pt-BMA], improves the imaging behavior of these polymers. Our attempts to elucidate the mechanism of dissolution inhibition for this series of compounds will be discussed. Fourier Transform Infrared (FTIR) studies in conjunction with dissolution rate measurements performed on a series of DI analogues suggest a mechanism based on hydrogen bonding.

  6. Fabrication of Fresnel microlens with excimer laser contour ablation

    NASA Astrophysics Data System (ADS)

    Wójcik, Michał R.; Antończak, Arkadiusz J.; Kozioł, Paweł E.; Łazarek, Łukasz K.; Stepak, Bogusz D.; Abramski, Krzysztof M.

    2014-08-01

    Laser micromachining systems based on excimer lasers are usually oriented to work with mask projection regime because of the low pulse repetition rate as well as large beam aperture of the laser source. In case of fabricating of the complex 3D structures, this approach introduces a number of limitations. Alternative solution might be usage of direct writing laser mode. Some examples of the so called contour ablation approach for fabricating microlenses with an absolutely monotonically changing cross-sectional profile are presented in the literature. Based on this idea and introducing new variables like automatic mask selection as well as optimizing process algorithms led us to obtain more versatile method for shape approximation. Hence, there were fabricated structures with cross-sectional profiles described as functions that are monotonic on specified intervals such as Fresnel microlenses. In this paper we describe approximation of process parameters for obtaining desired cross-sectional profiles and finally fabrication of few exemplary microlenses. All structures were characterized by a digital optical microscopy and compared to the given profiles. The accuracy of reproduction of the desired structures at the level of single microns was achieved.

  7. Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

    PubMed

    Dressel, M; Jahn, R; Neu, W; Jungbluth, K H

    1991-01-01

    Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable. PMID:1661360

  8. Excimer-laser-assisted deposition of diamondlike carbon hard coatings

    NASA Astrophysics Data System (ADS)

    Wei, Mao-Kuo; Popp, Angelika; Lang, Adolf; Schutte, Karsten; Bergmann, Hans W.

    1997-08-01

    Diamond-like carbon (DLC) films were deposited using the excimer laser assisted physical vapor deposition at room temperature. The films deposited at high vacuum (10-5 mbar) revealed more diamond-like character than under other atmospheres of argon and hydrogen. DLC- films can be deposited with a thickness more than 1 micrometers with the help of either an additional Ti-buffer layer or an in-situ laser treatment during the deposition. The adhesion of the films was qualitatively determined by using the indentation and bending tests. Additionally, the adhesion was found to be dependent on the power densities for the target ablation (IT) and for the in-situ laser treatment (IS), as well as, on the applied buffer layer. The roughness was found to be proportional to the film thickness at various surface morphologies of the substrate. The friction coefficient of DLC-films against steel (100Cr6) was found to be approximately 0.1 and the wear loss of the films was dependent on the properties of substrate material.

  9. Ion and neutral particle emission from polytetrafluoroethyene under 157-nm irradiation

    NASA Astrophysics Data System (ADS)

    Langford, Stephen; John, Sharon; Dickinson, Thomas

    2006-03-01

    Polytetrafluoroethylene (PFTE) is an important electronic material. Interactions with 157-nm laser radiation are of interest in the deposition and patterning of thin films of PTFE and similar materials. We have characterized the desorption of neutral and charged species from PTFE surfaces during 157-nm irradiation by time-resolved quadrupole mass spectroscopy. The principal neutral species are (CF2)x units. The neutral time-of-flight signals have a fast component with kinetic energies on the order of an eV, consistent with direct photochemical emission. These energetic neutrals are presumably created by scission of the C-C backbone by UV excitation. Slower neutral emissions are consistent with thermal emission from the surface at temperatures of several hundred kelvin above ambient. Much of the slower emission is attributed to thermally activated unzipping of the polymer backbone after photoelectronic scission. The principal positive and negative ions are C^+ and F^-. A large number of positive and negative charges are electrostatically coupled and travel together until separated by the electric fields of the mass filter.

  10. Advanced excimer laser technologies enable green semiconductor manufacturing

    NASA Astrophysics Data System (ADS)

    Fukuda, Hitomi; Yoo, Youngsun; Minegishi, Yuji; Hisanaga, Naoto; Enami, Tatsuo

    2014-03-01

    "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%. This means that the efficiency of lasers can be improve by up to 4 times in 450mm wafer production environments. Other future innovations include the introduction of totally Heliumfree Excimer lasers that utilize Nitrogen gas as its replacement for optical module purging. This paper discusses these and other innovations by Gigaphoton to enable green manufacturing.

  11. Microencapsulation of silicon cavities using a pulsed excimer laser

    NASA Astrophysics Data System (ADS)

    Sedky, S.; Tawfik, H.; Ashour, M.; Graham, A. B.; Provine, J.; Wang, Q.; Zhang, X. X.; Howe, R. T.

    2012-07-01

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100 °C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24 ns), focused onto an area of 23 mm2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm-2 to 800 mJ cm-2, the pulse rate from 1 Hz to 50 Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible.

  12. A survey of advanced excimer optical imaging and lithography

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Suwa, Kyoichi

    1998-11-01

    The first item discussed in this paper is to estimate the future trend regarding minimum geometry and the optical parameters, such as NA and wavelength. Simulations based on aerial images are performed for the estimation. The resolution limit is defined as a minimum feature size which retains practical depth of focus (DOF). Pattern geometry is classified into two categories, which are dense lines and isolated lines. Available wavelengths are assumed to be KrF excimer laser (λ=248 nm), ArF excimer laser (λ=193 nm) and F2 excimer laser (λ=157 nm). Based upon the simulation results, the resolution limit is estimated for each geometry and each wavelength. The second item is to survey ArF optics. At present, the ArF excimer laser is regarded as one of the most promising candidates as a next-generation light source. Discussions are ranging over some critical issues. The lifetime of ArF optics supposedly limited by the radiation compaction of silica glass is estimated in comparison with KrF optics. Availability of calcium fluoride (CaF2) is also discussed. As a designing issue, a comparative study is made about the optical configuration, dioptric or catadioptric. In the end, our resist-based performance is shown.

  13. Average power scaling of UV excimer lasers drives flat panel display and lidar applications

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

    2012-03-01

    Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.

  14. Theoretical Modeling of the Discharge-Pumped Xenon - Excimer Laser.

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-Bai

    The present dissertation is dedicated to a theoretical study of the discharge pumped XeCl excimer laser. For a better description of our system, Two modelings which supplement each other from different angles have been successfully developed. The first one, a comprehensive kinetics model which can be applied to the detailed simulations of the temporal behavior of the discharge characteristics and laser performance, is constructed by a set of coupled first -order differential equations, such as the rate equations, the Boltzmann equation, the external electric circuit equations, the energy balance equation, and the equations of optical resonator. The starting and termination of the discharge are taken into deliberation for the first time, especially for the Blumlein case. Some 70 kinetic processes and 23 chemical species are included. Such a problem can only be numerically solved by means of an elaborate computer code. Another model, on the other hand, pays attention to the quasi-steady-state to facilitate parametric study. A group of rate coefficients for the kinetic processes involving free electrons are approximated by analytic expressions using numerical results compiled from computer code calculations. Explicit expressions of the number densities for all relevant chemical species are obtained. Among them, HCI(O), H, and Cl can never reach steady-state population. Time history of the concentrations for these species are computed instead. With the discussions about the effect of vibrational relaxation and state-to-state transfer in the upper energy level, and the discussions about the rotational structure, collisional broadening, and dissociation of the diatomic ground state, we have extensively investigated the spontaneous emission spectra, the small-signal gain, the non-saturable absorption, the steady-state laser output power, and various efficiencies. Saturation effects in laser oscillators and laser amplifiers are discussed as well. These topics relate to the

  15. Excimer lasers. (Latest citations from the US Patent Bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1996-01-01

    The bibliography contains citations of selected patents concerning the design and development of excimer laser devices, apparatus, and systems for use in industrial and medical applications. Citations discuss ablation and lithography technology, compact excimer lasers, laser gas purification and recycling, microwave and discharge excited lasers, and rare gas halides. Applications are considered, including metallization and patterning, manufacturing of ophthalmic lenses, profiling of optical surfaces, treatment of engine parts, prosthetic surgery, and corneal ablation. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  16. Ablation algorithms and corneal asphericity in myopic correction with excimer lasers

    NASA Astrophysics Data System (ADS)

    Iroshnikov, Nikita G.; Larichev, Andrey V.; Yablokov, Michail G.

    2007-06-01

    The purpose of this work is studying a corneal asphericity change after a myopic refractive correction by mean of excimer lasers. As the ablation profile shape plays a key role in the post-op corneal asphericity, ablation profiles of recent lasers should be studied. The other task of this research was to analyze operation (LASIK) outcomes of one of the lasers with generic spherical ablation profile and to compare an asphericity change with theoretical predictions. The several correction methods, like custom generated aspherical profiles, may be utilized for mitigation of unwanted effects of asphericity change. Here we also present preliminary results of such correction for one of the excimer lasers.

  17. Excimer lasers. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-01-01

    The bibliography contains citations of selected patents concerning the design and development of excimer laser devices, apparatus, and systems for use in industrial and medical applications. Citations discuss ablation and lithography technology, compact excimer lasers, laser gas purification and recycling, microwave and discharge excited lasers, and rare gas halides. Applications are considered, including metallization and patterning, manufacturing of ophthalmic lenses, profiling of optical surfaces, treatment of engine parts, prosthetic surgery, and corneal ablation. (Contains a minimum of 106 citations and includes a subject term index and title list.)

  18. First results from AIMS beta tool for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Teuber, Silvio; Higashikawa, Iwao; Urbach, Jan-Peter; Schilz, Christof M.; Koehle, Roderick; Zibold, Axel M.

    2004-05-01

    In modern mask manufacturing, a successful defect mitigation strategy has been become crucial to achieve defect free masks for high-end lithography. The basic steps of such a strategy include inspection, repair, and subsequent post-repair qualification of repair sites. For the latter task, actinic aerial image measurements have been proven to be the technique of choice to assess the printability of a repaired site. In the last three years, International SEMATECH in cooperation with Infineon/AMTC-Dresden and SELETE, funded a joint development project at Carl Zeiss to develop an AIMS tool operating at the 157nm wavelength. The three beta tools were shipped in 2003 to the three beta customer sites. In this paper are presented the first results obtained with these beta tools, including measurements on binary as well as alternating phase shift masks. The technical properties of the tool were discussed with regards to the capability of the tool for defect qualification on photomasks. Additionally, preliminary results of the evaluation of alternating phase shift masks will be discussed, including measurements performed on dense lines-and-spaces structures with various pitch sizes.

  19. Effectiveness of a 308-nm excimer laser in treatment of vitiligo: a review.

    PubMed

    Alhowaish, Alauldin Khalef; Dietrich, Nathalie; Onder, Meltem; Fritz, Klaus

    2013-05-01

    Vitiligo is a relatively common acquired disorder, characterized by progressive loss of melanocytes from the epidermis and the epidermal appendages. The disease is associated with considerable morbidity because of a major impact on the quality of life. The treatment for vitiligo is generally unsatisfactory and challenging. There are a variety of therapeutic possibilities including topical corticosteroids, topical calcineurin inhibitors, as well as phototherapy with Psoralen plus UVA (PUVA), narrow-band UVB, and a 308-nm excimer laser and/or lamps. Furthermore, surgical methods encompass grafting and transplantation while depigmentation treatments and psychological support may also be considered. The objective is to assess the effect of the 380-nm excimer laser in the treatment of vitiligo based on the available studies and case series. We searched the relevant literature about vitiligo and excimer laser published between 1990 and 2012 using the MEDLINE database. We reviewed all relevant articles about 308-nm excimer laser and light sources assessing their efficacy in the management of vitiligo as well as their side effects. The value of combination treatment methods was also analyzed. The available studies provide strong evidence that the excimer laser represents the most effective approach to treat vitiligo compared to ordinary phototherapy. Excimer laser is relatively safe and effective for localized disease. UV-sensitive areas respond best as well as a short duration of the disease. More frequent treatments achieve better results. Compared to other treatment modalities, the excimer laser most likely constitutes the treatment of choice for localized vitiligo. Its efficacy can be further improved in combination with other therapies such as corticosteroids, pimecrolimus, or tacrolimus. PMID:22892613

  20. A Decade Of Excimer Laser Research And Development At Avco Research Laboratory

    NASA Astrophysics Data System (ADS)

    Boness, M. J. W.

    1987-01-01

    This paper presents a brief overview of excimer laser research and development performed at the Avco Research Laboratory during the past decade from 1975 to the present day. Progress and highlights are depicted against a backdrop of parallel developmental paths connecting the original search and discovery activities of the mid-seventies to the development of high power repetitively-pulsed Raman shifted excimer devices in progress today.

  1. Breakdown voltages for discharges initiated from plasma pulses produced by high-frequency excimer lasers

    SciTech Connect

    Yamaura, Michiteru

    2006-06-19

    The triggering ability under the different electric field was investigated using a KrF excimer laser with a high repetition rate of kilohertz order. Measurements were made of the magnitude of impulse voltages that were required to initiate a discharge from plasmas produced by a high-frequency excimer laser. Breakdown voltages were found to be reduced by 50% through the production of plasmas in the discharge gap by a high-frequency excimer laser. However, under direct-current electric field, triggering ability decreased drastically due to low plasma density. It is considered that such laser operation applied for laser-triggered lightning due to the produced location of plasma channel is formed under the impulse electric field since an electric field of the location drastically reduces temporary when the downward leader from thunderclouds propagates to the plasma channel.

  2. New high repetition rate, high energy 308 nm excimer laser for material processing

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Klaft, Ingo; Schmidt, Kai; Bragin, Igor; Albrecht, Hans-Stephan

    2007-02-01

    High power excimer lasers are well established as work horses for various kinds of micro material processing. The applications are ranging from drilling holes, trench formation, thin film ablation to the crystallization of amorphous-Si into polycrystalline-Si. All applications use the high photon energy and large pulse power of the excimer technology. The increasing demand for micro scale products has let to the demand for UV lasers which support high throughput production. We report the performance parameters of a newly developed XeCl excimer laser with doubled repetition rate compared to available lasers. The developed laser system delivers up to 900 mJ stabilized pulse energy at 600 Hz repetition rate. The low jitter UV light source operates with excellent energy stability. The outstanding energy stability was reached by using a proprietary solid-state pulser discharge design.

  3. KrF excimer laser precision machining of hard and brittle ceramic biomaterials.

    PubMed

    Huang, Yao-Xiong; Lu, Jian-Yi; Huang, Jin-Xia

    2014-06-01

    KrF excimer laser precision machining of porous hard-brittle ceramic biomaterials was studied to find a suitable way of machining the materials into various desired shapes and sizes without distorting their intrinsic structure and porosity. Calcium phosphate glass ceramics (CPGs) and hydroxyapatite (HA) were chosen for the study. It was found that KrF excimer laser can cut both CPGs and HA with high efficiency and precision. The ablation rates of CPGs and HA are respectively 0.081 µm/(pulse J cm(-2)) and 0.048 µm/(pulse  J cm(-2)), while their threshold fluences are individually 0.72 and 1.5 J cm(-2). The cutting quality (smoothness of the cut surface) is a function of laser repetition rate and cutting speed. The higher the repetition rate and lower the cutting speed, the better the cutting quality. A comparison between the cross sections of CPGs and HA cut using the excimer laser and using a conventional diamond cutting blade indicates that those cut by the excimer laser could retain their intrinsic porosity and geometry without distortion. In contrast, those cut by conventional machining had distorted geometry and most of their surface porosities were lost. Therefore, when cutting hard-brittle ceramic biomaterials to prepare scaffold and implant or when sectioning them for porosity evaluation, it is better to choose KrF excimer laser machining. PMID:24784833

  4. Excimer laser debridement of necrotic erosions of skin without collateral damage

    NASA Astrophysics Data System (ADS)

    Wynne, James J.; Felsenstein, Jerome M.; Trzcinski, Robert; Zupanski-Nielsen, Donna; Connors, Daniel P.

    2011-07-01

    Pulsed ArF excimer laser radiation at 6.4 eV, at fluence exceeding the ablation threshold, will debride burn eschar and other dry necrotic erosions of the skin. Debridement will cease when sufficiently moist viable tissue is exposed, due to absorption by aqueous chloride ions (Cl-) through the non-thermal process of electron photodetachment, thereby inhibiting collateral damage to the viable tissue. ArF excimer laser radiation debrides/ablates ~1 micron of tissue with each pulse. While this provides great precision in controlling the depth of debridement, the process is relatively time-consuming. In contrast, XeCl excimer laser radiation debrides ~8 microns of tissue with each pulse. However the 4.0 eV photon energy of the XeCl excimer laser is insufficient to photodetach an electron from a Cl- ion, so blood or saline will not inhibit debridement. Consequently, a practical laser debridement system should incorporate both lasers, used in sequence. First, the XeCl excimer laser would be used for accelerated debridement. When the necrotic tissue is thinned to a predetermined thickness, the ArF excimer laser would be used for very precise and well-controlled debridement, removing ultra-thin layers of material with each pulse. Clearly, the use of the ArF laser is very desirable when debriding very close to the interface between necrotic tissue and viable tissue, where the overall speed of debridement need not be so rapid and collateral damage to viable tissue is undesirable. Such tissue will be sterile and ready for further treatment, such as a wound dressing and/or a skin graft.

  5. Initial experience in the extraction of chronically implanted pacemaker leads using the Excimer laser sheath

    PubMed Central

    Levy, T; Walker, S; Paul, V

    1999-01-01

    OBJECTIVE—To assess the safety and efficiency of the Excimer laser sheath in extracting chronically implanted pacemaker leads.
PATIENTS—Eight patients were studied (one female, mean age 62 years, range 34 to 77) with 17 pacemaker leads (five atrial, 10 ventricular, two implantable defibrillator). The mean implantation time was 65 months (range 23 to 188). The indications for lead extraction were chronic infection (7), superior vena cava obstruction (4), lead malfunction (4), and pain (2).
METHODS—A prospective analysis of the use of the Excimer laser sheath in extracting chronically implanted pacemaker leads. Laser sheath extraction was undertaken if conventional extraction techniques with simple traction or traction with a locking stylet had failed. If laser sheath extraction was unsuccessful, basket retrieval of the lead from the groin was performed.
RESULTS—Complete lead removal was achieved in 16 leads (94%). In one case the electrode tip was left behind without complication. Extraction was achieved with the laser sheath alone in 16 leads. Basket retrieval was required in one case after laser failure. There were no complications.
CONCLUSIONS—The Excimer laser sheath appears to be an effective and safe technique for extracting chronically implanted pacemaker leads. It can be used in combination with the currently available techniques for successful lead extraction.


Keywords: Excimer laser sheath; lead extraction; pacing PMID:10377320

  6. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo; Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  7. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    SciTech Connect

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  8. Excimer laser annealing: A gold process for CZ silicon junction formation

    NASA Technical Reports Server (NTRS)

    Wong, David C.; Bottenberg, William R.; Byron, Stanley; Alexander, Paul

    1987-01-01

    A cold process using an excimer laser for junction formation in silicon has been evaluated as a way to avoid problems associated with thermal diffusion. Conventional thermal diffusion can cause bulk precipitation of SiOx and SiC or fail to completely activate the dopant, leaving a degenerate layer at the surface. Experiments were conducted to determine the feasibility of fabricating high quality p-n junctions using a pulsed excimer laser for junction formation at remelt temperature with ion-implanted surfaces. Solar-cell efficiency exceeding 16 percent was obtained using Czochralski single-crystal silicon without benefit of back surface field or surface passivation. Characterization shows that the formation of uniform, shallow junctions (approximately 0.25 micron) by excimer laser scanning preserves the minority carrier lifetime that leads to high current collection. However, the process is sensitive to initial surface conditions and handling parameters that drive the cost up.

  9. A comparison of excimer laser, thermal probe, and mechanical devices for recanalizing occluded human arteries.

    PubMed

    Moriuchi, M; Tobis, J M; Mcrae, M; Mallery, J A; Macleay, L; Moussabeck, O; Berns, M; Henry, W L

    1991-06-01

    To evaluate the mechanism of excimer laser recanalization and compare the results with those of laser-assisted thermal probe recanalization and mechanical recanalization, a total of 42 human atherosclerotic totally occluded arterial segments (2-15 cm long) were recanalized by excimer laser with a 400-800 micron quartz fiber pulsed at 20 Hz with 50 mJ/mm2 of energy (n = 21), an Argon heated thermal probe at 10-12 watts (n = 11), a guidewire directed through a 6 Fr multipurpose catheter, or an angioplasty balloon catheter (n = 10). On histologic examination, the excimer laster created a single round lumen or multiple lumens ("Swiss-cheese" like appearance) with no evidence of thermal injury at the perimeter of the lumen. The incidence of perforation in vitro was less with an excimer laser catherter (8/21 or 38%) than with the thermal prove (10/11 or 91%) (p less than 0.01). However, serial histologic cross-sectional examination showed that the pathway of the devices were essentially the same in all recanalization procedures. The pathway of the device was located outside the atheroma but proximal to the internal elastic membrane in 13 arteries with the excimer laser (62%), in 10 arteries with the thermal probe (91%), and 8 arteries with mechanical devices (80%). These results indicate that although the eximer laser could recanalize human atherosclerotic arteries without thermal injury, the fiber frequently deflected around firm atherosclerotic plaque and advanced in a dissection plane between the plaque and media. A similar course was noted for the thermal probe or during mechanical recanalization with a guidewire and catheter. To insure the safety of an excimer fiber or a thermal probe to reopen complete occlusions, better guidance systems must be developed. PMID:1875527

  10. Early and late healing responses of normal canine artery to excimer laser irradiation.

    PubMed

    Prevosti, L G; Leon, M B; Smith, P D; Dodd, J T; Bonner, R F; Robinowitz, M; Clark, R E; Virmani, R

    1988-07-01

    Acute in vitro histologic studies have shown that the pulsed xenon chloride excimer laser causes precise microablation without the surrounding thermal tissue injury associated with frequently used continuous-wave lasers such as the argon, carbon dioxide, and neodymium:yttrium aluminum garnet lasers. However, the in vivo healing response of artery wall to excimer laser injury is not known. Accordingly, a xenon chloride excimer laser (308 nm, 40 nsec pulse width, 39 mJ/mm2/pulse) was transmitted via a 600 micron fused silica fiber to create 420 craters of varying depths (30 to 270 micron) in 21 normal canine femoral and carotid arteries. At 2 hours, 2 days, 10 days, and 42 days after excimer laser ablation, the artery segments were perfusion fixed in situ and analyzed by light, scanning, and transmission electron microscopy. At 2 hours, craters were covered by a carpet of platelets and entrapped red blood cells. Fibrin and exposed collagen fibers were seen at the crater base. There was a sharp demarcation of the crater-artery wall interface without lateral laser tissue injury. At 2 days, adherent platelets persisted with thrombus covering the base of the craters. Early healing responses were present, consisting of polymorphonucleated leukocytes and new endothelial cells, which extended over the crater rims. At 10 days, no thrombi were seen, and healing continued with almost complete reendothelialization. Macrophages, fibroblasts, fibrin, and entrapped red blood cells were present below the reendothelialized surface. At 42 days, healing was complete with obliteration of the craters by fibrointimal ingrowth. The surface was completely covered by a smooth monolayer of axially aligned endothelial cells. There were no aneurysms or surface hyperplastic responses. These favorable healing responses in normal canine arteries suggest that pulsed lasers with high tissue absorption coefficients, such as the xenon chloride excimer laser, may be suitable energy sources for

  11. CO2 laser cleaning of black deposits formed during the excimer laser etching of polyimide in air

    NASA Astrophysics Data System (ADS)

    Koren, G.; Donelon, J. J.

    1988-01-01

    Pulsed CO2 laser cleaning of black debris formed during the excimer laser ablation of polyimide in air is demonstrated. The 10.6 μm CO2 laser radiation is strongly absorbed in the debris but only weakly absorbed in polyimide thus enabling the clean removal of the debris without damaging the polyimide.

  12. [PKP for Keratoconus - From Hand/Motor Trephine to Excimer Laser and Back to Femtosecond Laser].

    PubMed

    Seitz, B; Szentmáry, N; Langenbucher, A; Hager, T; Viestenz, A; Janunts, E; El-Husseiny, M

    2016-06-01

    For patients with keratoconus, rigid gas-permeable contact lenses are the first line correction method and allow good visual acuity for quite some time. In severe stages of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no longer tolerated. If there are contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis. In patients with advanced keratoconus - especially after corneal hydrops due to rupture of Descemet's membrane - penetrating keratoplasty (PKP) is still the first line surgical method. Non-contact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and for patients with repeat grafts due to "keratoconus recurrences" due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually, depending on corneal size ("as large as possible - as small as necessary"). Limbal centration is preferred intraoperatively, due to optical displacement of the pupil. During the last 10 years, femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach. Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces "vertical tilt" and "horizontal torsion" of the graft in the recipient bed, and thus results in significantly less "all-sutures-out" keratometric astigmatism (2.8 vs. 5.7 D), more regular topography (surface regularity index [SRI] 0.80 vs. 1.0) and better visual acuity (0.80 vs. 0.60), in comparison to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. However, the refractive outcome of femtosecond laser keratoplasty resembles that with

  13. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  14. The mechanism of the surface morphology transformation for the carbon nanotube thin film irradiated via excimer laser

    SciTech Connect

    Chien, Yun-Shan; Lee, I-Che; Yang, Po-Yu; Wang, Chao-Lung; Tsai, Wan-Lin; Wang, Kuang-Yu; Chou, Chia-Hsin; Cheng, Huang-Chung

    2013-05-06

    In this paper, the surface morphology transformation of the sprayed carbon nanotube (CNT) thin film irradiated with the excimer laser has been systematically investigated. Under the excimer-laser irradiation, two phenomena, including the annealing and ablation effects, were found to be dependent on the incident laser energy and overlapping ratios. Moreover, the extremely high protrusions would be produced in the interface between the annealing and ablation regions. The mechanism of the CNT thin film under the excimer laser irradiation was, therefore, proposed to derive the surface morphology modifications and the further reinforced crystallinity with proper laser energy densities and overlapping ratios.

  15. Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions

    NASA Astrophysics Data System (ADS)

    Yan, Zijie

    2011-12-01

    Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been

  16. Primary success and one-year followup of percutaneous peripheral excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Visona, Adriana; Liessi, Guido; Miserocchi, Luigi; Bonanome, Andrea; Lusiani, Luigi; Breggion, Giovanni; Pagnan, Antonio

    1992-08-01

    Excimer laser angioplasty was performed in 59 patients (44 males and 17 females, mean age 63 +/- 9 years, range 39 - 77) affected by peripheral vascular disease. Fifty patients had a total occlusion of the superficial femoral artery, three of the iliac artery, and one of the popliteal artery; seven patients showed a subocclusive stenosis of the superficial femoral artery. A commercial excimer laser (Technolas Max-10) was used at the Xenon-Chloride wavelength of 308 nm. The laser operated at 120 ns pulse length and at 20 Hz repetition rate. Applied energy fluence was 20 mJ/pulse. The energy was delivered through a multifiber catheter, which combines 12 (7F) or 18 (9F) fibers (260 micron diameter each), concentrically arranged. Balloon dilatation was associated in 51 patients. Successful recanalization was obtained in 59 out of 61 patients (97%). Failure to recanalize the occluded arteries occurred in two cases, and was due to dissection. Early thrombosis and reocclusion (within 48 hours) was observed in five patients. The cumulative patency rate was 56% at one year. On the basis of these results, excimer laser assisted angioplasty seems a feasible and safe procedure. However, this technique did not solve the restenosis problem. A wide application of excimer laser as a stand alone approach can be foreseen for treatment of peripheral vascular disease.

  17. A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser.

    PubMed Central

    Marshall, J; Trokel, S; Rothery, S; Krueger, R R

    1986-01-01

    This paper reviews the potential role of excimer lasers in corneal surgery. The morphology of incisions induced by two wavelengths of excimer laser radiation, 193 nm and 248 nm, are compared with the morphology of incisions produced by diamond and steel knives. Analysis suggests that ablation induced by excimer laser results from highly localised photochemical reactions and that 193 nm is the optimal wavelength for surgery. The only significant complication of laser surgery is loss of endothelial cells when incisions are within 40 micron of Descemet's membrane. Images PMID:3013283

  18. Formation of short high-power laser radiation pulses in excimer mediums

    NASA Astrophysics Data System (ADS)

    Losev, V. F., Sr.; Ivanov, N. G.; Panchenko, Yu. N.

    2007-06-01

    Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >>, Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe IICl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe II* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.

  19. Successful use of the excimer laser for generalized psoriasis in an ustekinumab non-responder.

    PubMed

    Malakouti, Mona; Brown, Gabrielle Elena; Sorenson, Eric; Leon, Argentina; Koo, John; Levin, Ethan Charles

    2015-03-01

    Effective treatments for moderate to severe psoriasis are phototherapy and biologics. These treatments are similar in that they both decrease cutaneous immune system hyperactivity yet do so via different mechanisms. Our patient, a 63 year old Asian male had a rapid response to treatment with the high dose excimer laser, having previously failed treatment with 28 weeks of ustekinumab therapy. A pre-treatment biopsy of a psoriatic plaque was found to contain relatively low levels of IFN-γ (Th1) and IL-17 (Th17) secreting T cells. Following treatment with the excimer laser, the patient had a quick improvement in PASI that was reflected by a 3-fold reduction in the number of live T cells found in the post-treatment biopsy. Although ustekinumab and the excimer laser both result in decreased levels of these cytokines, the excimer laser directly causes apoptosis of T cells and induces DNA damage in antigen presenting cells. Thus, the broader effects of phototherapy on immune cells compared to the targeted inhibition of IL-12 and IL-23 by ustekinumab likely account for the superior response observed. PMID:25780961

  20. Temperature sensitivity of an atmospheric Raman lidar system based on a XeF excimer laser

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Murphy, William F.; Walsh, Nita W.; Evans, Keith D.

    1993-01-01

    The temperature sensitivity of Raman backscattering from atmospheric nitrogen, oxygen, and water vapor is considered over the range of temperatures expected in the troposphere. These results are applied to the Raman spectrum induced by a XeF excimer laser, which produces three line groups centered at approximately 349, 351, and 353 nm. Bandpass filter characteristics are determined for this case.

  1. Excimer v. Nd:YAG: comparative analysis of initial ultrastructural alterations produced by two distinct lasers

    NASA Astrophysics Data System (ADS)

    Nevorotin, Alexey J.

    1990-09-01

    Fine structural alteratious produced iediate1y after irradiation with either XeC1 excimer or Nd:Y.AG laser have been studied in rat liver samples processed histochemically for glucose-6-phosphatase (GP) activity, a marker enzyme for the endoplasmic reticulum (ER) of hepatocytes. General vesiculation of ER along with moderate inactivation of GP was apparent following excimer lazing which contrasted with better structural but poorer enzymatic preservation of ER in the hepatocytes irradiated with Nd:YAG laser. c'i the basis of this and our recent study. (A. Nevorotin, M. Kul 1 . 1989. Arch. Pathol . v. 51, N 7, pp. 63'TO ) a conclus ion is drawn on a potential surgical advantage of excimer laser over its Nd:YAG counterpart due presumably to lesser extent of cellular and macromolecular damage implicative in the process of healing of laser-inflicted lesions. A mechanism of ER vesiculation is considered in the iignt of probable dynamic impact transferred to the ER membranes by excimer irradiation by analogy with other nign energy mechanical forces (e.g. nign gravitation or ultrasonication) known to interfere with membrane structural organization.

  2. [Percutaneous coronary Excimer laser angioplasty in patients with coronary heart disease].

    PubMed

    Karsch, K R; Haase, K K; Mauser, M; Ickrath, O; Voelker, W; Baumbach, A; Seipel, L

    1990-07-01

    To verify the efficacy and safety of percutaneous coronary excimer laser angioplasty in patients with coronary artery disease a prospective study was conducted in 60 patients. The application of laser light was possible in 55 of the 60 patients. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter, each arranged concentrically around a central lumen suitable for an 0.014-inch flexible guide wire was used. The light source was a commercial excimer laser emitting energy at a wavelength of 308 nm, with a pulse duration of 60 ns. The laser was operated at 20 Hz; mean energy transmission was 30 +/- 5 mJ/mm2. In 23 of the 55 patients treated with excimer laser energy the qualitative angiographic results were sufficient. In 32 patients additional balloon angioplasty was necessary, either because of an insufficient result or due to vessel closure after laser ablation. In 47 of the 55 patients control angiography was performed within the 6-month follow-up period. Rate of restenosis was higher in patients treated with laser ablation and subsequent balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (6 of 19). Results of the 6-month observation period suggest that 1) coronary excimer laser angioplasty in combination with subsequent balloon angioplasty results in a considerable increase of the restenosis rate; 2) the exclusive use of laser ablation also results in a restenosis rate comparable to balloon angioplasty alone; and 3) the impact of this new method using improved application systems and higher energy transmission has to be determined in further studies. PMID:2399764

  3. Excimer-pumped alkali vapor lasers: a new class of photoassociation lasers

    NASA Astrophysics Data System (ADS)

    Readle, J. D.; Wagner, C. J.; Verdeyen, J. T.; Spinka, T. M.; Carroll, D. L.; Eden, J. G.

    2010-02-01

    Excimer-pumped alkali vapor lasers (XPALs) are a new class of photoassociation lasers which take advantage of the spectrally broad absorption profiles of alkali-rare gas collision pairs. In these systems, transient alkali-rare gas molecules are photopumped from the thermal continuum to a dissociative X2Σ+ 1/2 interaction potential, subsequently populating the n2P3/2 state of the alkali. The absorption profiles >=5 nm and quantum efficiencies >98% have been observed in oscillator experiments, indicating XPAL compatibility with conventional high power laser diode arrays. An alternative technique for populating the n2P3/2 state is direct photoexcitation on the n2P3/2<--n2S1/2 atomic transition. However, because the XPAL scheme employs an off-resonant optical pump, the strengths of resonantly-enhanced nonlinear processes are minimized. Additionally, the absorption coefficient may be adjusted by altering the number densities of the lasing species and/or perturbers, a valuable asset in the design of large volume, high power lasers. We present an overview of XPAL lasers and their operation, including the characteristics of recently demonstrated systems photopumped with a pulsed dye laser. Lasing has been observed in Cs at both 894 nm and 852 nm by pumping CsAr or CsKr pairs as well as in Rb at 795 nm by pumping RbKr. These results highlight the important role of the perturbing species in determining the strength and position of the excimer absorption profile. It is expected that similar results may be obtained in other gas mixtures as similar collision pair characteristics have historically been observed in a wide variety of transient diatomic species.

  4. Preparation and disinfection of root canals by 308-nm excimer laser light

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim; Folwaczny, Matthias; Lehn, Norbert

    1994-09-01

    Conventional root canal treatments often fail due to insufficient removal of root canal contents and due to ineffective reduction of bacterial growth. In vitro investigations on the 308 nm excimer laser root canal preparation showed excellent results concerning the preparation quality. The aim of the present study was to investigate the influence of 308 nm excimer laserlight on the growth of bacteria. Bacterial suspensions of Staph. aureus, E. coli, and Enterococcus faec. were irradiated with various energy densities and different time duration. In order to exclude thermal side effects the temperature rise inside the suspensions was registered during irradiation. It was able to demonstrate that 308 nm excimer laserlight effects a log reduction of germ concentration at energy densities of 0.5 - 2.4 J/cm2. Laserlight effects germ reduction even without tissue removal. The effectiveness is dependent on the type of bacteria, the energy density, and the time of irradiation. The antimicrobial effect is independent from temperature.

  5. Mechanism of injurious effect of excimer (308 nm) laser on the cell

    NASA Astrophysics Data System (ADS)

    Nevorotin, Alexey J.; Kallikorm, A. P.; Zeltzer, Gregory L.; Kull, Mart M.; Mihkelsoo, Virgo T.

    1991-06-01

    A Lameta 22710 excimer laser operating at 70 mJ/mm2 per pulse, with pulse duration of 70 nsec, and pulse repetition rate of 10 Hz, equipped with a quartz filament as energy conductor was used to make incisions on rat liver. 2 to 5 sec after irradiation the specimens were fixed and further processed for electron microscopy and histochemical visualization of the endoplasmic reticulum (ER) marker enzyme glucose-6- phosphatase at the ultrastructural level. The additional series were: fixation before irradiation-(A); lasing with Nd:YAG laser (1064 nm, continuous wave mode, 40 J/mm2)-(B); incision with a white-hot steel needle-(C); and incision with an Esto-Rex ultrasound scalpel (66 kHz, 6 Wt, vibration amplitude of 15 micrometers )-(D). The results showed that unlike Series C and B, in which high temperature caused severe damage to all cellular organellae, the excimer action was much more specific. It caused vesiculation of ER without significant injuries to other cellular structures. The analogous effect was noted after US scalpel cutting, thereby allowing a conclusion that a kind of dynamic rather than thermal factor is responsible for the observed phenomenon of vesiculation. The time schedule of vesicle formation and molecular background of membrane transformation is considered in the light of the data of Series A and D, and also on the basis of available information of membrane behavior. Photoablative effect of pulsed excimer laser is thought to be based on chemical decomposition of organic molecules and their ejection from the tissue to the action of high energy photons. Pressure waves (either acoustic or shock) are presumably generated powerful enough to cause tissue and cell damage beyond the site of ablation. Some thermal and fluorescence events are also implicative in biological targets irradiated with excimer lasers. In our previous studies electron histochemistry was employed for the analysis of cellular alterations caused with a continuous wave mode

  6. Comparison of KrF and ArF excimer laser treatment of biopolymer surface

    NASA Astrophysics Data System (ADS)

    Michaljaničová, I.; Slepička, P.; Heitz, J.; Barb, R. A.; Sajdl, P.; Švorčík, V.

    2015-06-01

    The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  7. Spectrally narrowed lasing of a self-injection KrF excimer laser

    NASA Astrophysics Data System (ADS)

    Shimada, Yasuhiro; Wani, Koichi; Miki, Tadaaki; Kawahara, Hidehito; Mimasu, Mutsumi; Ogata, Yoshiro

    1990-08-01

    Spectrally nantwed lasing of a KrF excimer laser has teen ahieved by a self-injection technique using abeam splitter for power extraction aixi intravity etalons for spectral-narrowing. The laser cavity is divithi into an amplifying branch aix! a spectralnarrowing branch. The spectral bandwidth was narrowed to <3pm FWHM with air-sed etalons placed in the spectral-narrowing branch. A laser propagation model was intrOdUced for describing the laser intensity traveling in the laser cavity. The calculated intensityincident onthe intracavityetalons wassmaller thanthat in theconventional Fabry-Perotcavity withplane-parallel mirrors.

  8. Excimer laser photochemistry of silane-ammonia mixtures at 193 nm

    SciTech Connect

    Beach, D.B.; Jasinski, J.M. )

    1990-04-05

    The ArF excimer laser induced photochemistry of silane-ammonia mixtures has been studied with molecular beam sampling mass spectrometry. The observed products include disilane, trisilane, and all possible aminosilanes, SiH{sub x}(NH{sub 2}){sub 4-x}, x = 0-3. These products are formed under steady-state photolysis conditions and under single-laser-pulse conditions. A mechanism for the formation of these species is proposed and quantitatively evaluated.

  9. Bioactive glass surface for fiber reinforced composite implants via surface etching by Excimer laser.

    PubMed

    Kulkova, Julia; Moritz, Niko; Huhtinen, Hannu; Mattila, Riina; Donati, Ivan; Marsich, Eleonora; Paoletti, Sergio; Vallittu, Pekka K

    2016-07-01

    Biostable fiber-reinforced composites (FRC) prepared from bisphenol-A-glycidyldimethacrylate (BisGMA)-based thermosets reinforced with E-glass fibers are promising alternatives to metallic implants due to the excellent fatigue resistance and the mechanical properties matching those of bone. Bioactive glass (BG) granules can be incorporated within the polymer matrix to improve the osteointegration of the FRC implants. However, the creation of a viable surface layer using BG granules is technically challenging. In this study, we investigated the potential of Excimer laser ablation to achieve the selective removal of the matrix to expose the surface of BG granules. A UV-vis spectroscopic study was carried out to investigate the differences in the penetration of light in the thermoset matrix and BG. Thereafter, optimal Excimer laser ablation parameters were established. The formation of a calcium phosphate (CaP) layer on the surface of the laser-ablated specimens was verified in simulated body fluid (SBF). In addition, the proliferation of MG63 cells on the surfaces of the laser-ablated specimens was investigated. For the laser-ablated specimens, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V). We concluded that Excimer laser ablation has potential for the creation of a bioactive surface on FRC-implants. PMID:27134152

  10. Excimer laser absorption on PMMA plate and on cornea: a practical approach using volume luminance

    NASA Astrophysics Data System (ADS)

    Digulescu, Petre P.; Carstocea, Benone D.; Sterian, Livia

    2001-04-01

    Excimer laser refractive surgery used in Ophthalmology in order to treat the human eye refraction problems has been performed over 10 years around the world. However a systematic approach of the physical phenomena and especially of the absorption on the cornea during the laser treatment is missing in the literature and the doctors are usually using empiric nomograms in order to achieve good results. The theoretical approach is difficult because of the complexity of the phenomena interconnected each to the others. The UV excimer laser beam used to controllably ablate the cornea is highly absorbed in the air and also is supplementary absorbed in the plume generated almost instantaneous as consequence of the ablation on the cornea. Because of this non-linear proces the energy of the laser beam delivered to the eye must be calibrated before each intervention on a patient. The purpose of the present work is to develop a mathematical model of the excimer laser absorption on PMMA and on human cornea based on a new physical notion, the Volume Luminance. The Volume Luminance is defined as volume density of the intensity of laser radiation. A brief theory of the Volume Luminance is also presented.

  11. 300 W XeCl excimer laser annealing and sequential lateral solidification in low temperature poly silicon technology

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Kahlert, Hans-Juergen; Fechner, Burkhard; Rebhan, Ulrich; Osmanow, Rustem

    2003-05-01

    Industrial production of low temperature p-Si back plates for LCDs by high power excimer laser annealing was introduced several years ago. Regarding the economy of the process, one of the major advantages of excimer laser annealing is the opportunity to make use of low cost glass substrates due to the low temperature of the annealing process. The Lambda Physik high power excimer laser series are operated with the MicroLas 370 mm line beam optics, integrated by Japan Steel Works into industrial systems. The MicroLas line beam optics for conventional excimer laser annealing (ELA) process converts the raw laser beam profile into a stable and homogeneous rectangular illumination field with high aspect ratio. The excimer laser light source, the LAMBDA STEEL 1000, delivers stabilized pulse energies up to 1 Joule at repetition rates up to 300Hz. The crystallization using excimer lasers allows to produce films with electron mobility of 100-150 cm2/Vsec with the Line beam technique. The new SLS-method, which is currently under industrial investigation, even allows to obtain electron mobility between 200-400 cm2/Vsec.

  12. Microsurgery of the retina with a needle-guided 193-nm excimer laser.

    PubMed

    Lewis, A; Palanker, D; Hemo, I; Pe'er, J; Zauberman, H

    1992-07-01

    This article presents a method used to guide the beam from an argon fluoride excimer laser to make it suitable for microsurgical purposes and confine it to areas that can be varied in dimension from 1 micron to tens or hundreds of microns. This approach guides the excimer laser beam with an articulated mechanical arm and confines it with variable-diameter tapered tubes, possibly allowing the use of this laser in in vitro retinal surgery with endolaser techniques. Currently, because of the lack of a delivery and focusing system for the 193-nm argon fluoride beam and its absorption by biologic liquids, this laser is used exclusively in ophthalmology for topical applications, such as corneal sculpting. This new method resolves these problems in a unique way with impressive results. Specifically, it was shown that, with this needle-guided excimer laser, it is possible to remove retinal tissue accurately without detectable damage to surrounding cells. Applications of this new technique in retinal surgery are discussed. PMID:1634334

  13. 193 nm excimer laser sclerostomy in pseudophakic patients with advanced open angle glaucoma.

    PubMed Central

    Allan, B D; van Saarloos, P P; Cooper, R L; Constable, I J

    1994-01-01

    A modified open mask system incorporating an en face air jet to dry the target area during ablation and a conjunctival plication mechanism, which allows ab externo delivery of the 193 nm excimer laser without prior conjunctival dissection, has been developed to form small bore sclerostomies accurately and atraumatically. Full thickness sclerostomies, and sclerostomies guarded by a smaller internal ostium can be created. A pilot therapeutic trial was conducted in pseudophakic patients with advanced open angle glaucoma. Six full thickness sclerostomies (200 microns and 400 microns diameter) and three guarded sclerostomies were created in nine patients by 193 nm excimer laser ablation (fluence per pulse 400 mJ/cm2, pulse rate 16 Hz, air jet pressure intraocular pressure +25 mm Hg). After 6 months' follow up, intraocular pressure was controlled (< or = 16 mm Hg) in eight of the nine patients (6/9 without medication). Early postoperative complications included hyphaema (trace--2.5 mm) (6/9), temporary fibrinous sclerostomy occlusion (4/9), profound early hypotony (all patients without fibrinous occlusion), and suprachoroidal haemorrhage in one case. Conjunctival laser wounds were self sealing. Small bore laser sclerostomy procedures are functionally equivalent to conventional full thickness procedures, producing early postoperative hypotony, with an increased risk of suprachoroidal haemorrhage in association with this. Further research is required to improve control over internal guarding in excimer laser sclerostomy before clinical trials of this technique can safely proceed. Images PMID:8148335

  14. New polymer for 157-nm single-layer resist based on fluorine-containing acryl copolymer

    NASA Astrophysics Data System (ADS)

    Ogata, Toshiyuki; Endo, Koutaro; Komano, Hiroshi; Nakayama, Toshimasa

    2001-08-01

    We are reporting on the development of acryl polymer based on novel methacrylate and acrylate monomers with various trifluoromethyl groups for the application to 157nm chemically amplified positive-tone resists. The (alpha) - trifluoromethylation of the alkyl ester in methacrylate or acrylate could employ the reduction of acrylpolymer absorbance at 157nm by spectra analysis with the VUV-200 spectrophotometer by JASCO. Although the trifluoromethyl groups could employ the reduction of base polymer absorbance at 157nm, the homopolymers have issued weak etch resistance as a photoresist base polymer. To take account of this issue, we have developed a novel monomer, trifluoromethyl- iso-adamantylmethacrylate (TFIAdMA) and a new co-polymer system with the combination of fluorinated methacrylate derivatives and substituted p-hydroxystyrene. The absorption coefficient of poly(p-tert-butoxystyren-co- hexafluoro-tert-butyl methacrylate-co-methacrylic acid) incicated to be less than 3 micrometers -1 at 157nm. Patterning results were obtained with a 157nm contact exposure system of VUVES-4500 by LTJ. One of the experimental resists, based on a particular polymer ratio and photo acid generator, has clearly achieved 180nm line and space pattern resolution. At 140nm resist film thickness, the sensitivity was 31 mJ/cm2 when using 0,26N tetrametylammonium hydroxide surfactant type developer.

  15. Simulation of excimer laser micromachined 3D surface using a CAD solid modeling package

    NASA Astrophysics Data System (ADS)

    Hume, Richard G.; Iovenitti, Pio G.; Hayes, Jason P.; Harvey, Erol C.

    2002-11-01

    This paper describes the research on the development of a visualisation tool to generate 3D solid models of structures produced by micromachining using an excimer laser system. Currently, the development of part programs to achieve a desired microstructure is by a trial and error approach. This simulation tool assists designers and excimer machine programmers to produce microstructures using the excimer laser. Users can develop their microstructures and part programs with the assistance of digital prototypes rather than designing products using expensive laser micromachining equipment. The methods to simulate micromachining using the solid modelling package, SolidWorks, are described, and simulation and actual machined examples are reported. A basic knowledge of the solid modelling package is required to develop the simulations, and complex models take time to prepare, however, the development time can be minimised by working from previous simulations. The models developed can be parameterised so that families of designs can be investigated for little additional effort to optimise the design before committing to laser micromachining.

  16. Application of optical tweezers and excimer laser to study protoplast fusion

    NASA Astrophysics Data System (ADS)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

  17. Valacyclovir for the prevention of recurrent herpes simplex virus eye disease after excimer laser photokeratectomy.

    PubMed Central

    Asbell, P A

    2000-01-01

    PURPOSE: A variety of factors have been reported as inducing the reactivation of latent herpes simplex virus (HSV), among them stress, trauma, and UV radiation. Excimer laser photorefractive keratectomy (PRK) is a surgical procedure utilizing a 193 nm ultraviolet light to alter the curvature of the cornea and hence correct vision. Reactivation of ocular herpes simplex keratitis following such excimer laser PRK has been reported. All published cases of HSV reactivation following excimer laser treatment in humans are reviewed. The present study evaluates whether stress, trauma of the corneal de-epithelialization prior to the laser, or the excimer laser treatment itself to the stromal bed induces this ocular reactivation of the latent HSV, and whether a systemic antiviral agent, valacyclovir, would prevent such laser PRK-induced reactivation of the HSV. METHODS: Forty-three normal 1.5- to 2.5-kg New Zealand white rabbits were infected on the surface of the cornea with HSV-1, strain RE. The animals were monitored until resolution, and then all animals were divided into 5 treatment groups: (1) de-epithelialization only, intraperitoneal (i.p.) saline for 14 days; (2) de-epithelialization plus laser, i.p. saline for 14 days; (3) de-epithelialization plus laser, valacyclovir 50 mg/kg per day i.p. for 14 days; (4) de-epithelialization plus laser, valacyclovir 100 mg/kg per day i.p. for 14 days; (5) de-epithelialization plus laser, valacyclovir 150 mg/kg per day i.p. for 14 days. Animals were evaluated in a masked fashion by clinical examination biweekly and viral cultures biweekly through day 28. RESULTS: The reactivation rates were as follows: group 1, 0%; group 2, 67%; group 3, 50%; group 4, 17%; and group 5, 0%. Viral titers were negative in animals that had no reactivation but persistently positive in those that had reactivation (day 6 through day 28). CONCLUSIONS: Excimer laser (193 nm) treatment can trigger reactivation of ocular herpes disease (67%) and viral

  18. Excimer laser sclerostomy: the in vitro development of a modified open mask delivery system.

    PubMed

    Allan, B D; van Saarloos, P P; Russo, A V; Cooper, R L; Constable, I J

    1993-01-01

    The argon fluoride (ArF) excimer laser at 193 nm ablates the ocular tissues with a new order of precision and virtually no adjacent damage. A glaucoma filtration operation has been designed in which small-bore sclerostomies are created using the ArF excimer laser delivered through an open mask. The mask plicates the conjunctiva at the limbus prior to ablation. Removing the mask at the end of the procedure allows the conjunctiva to relax back to its original position, separating the conjunctival and scleral wounds. Formal conjunctival dissection is thus avoided. Feasibility studies in cadaver pig eyes, using a fluence per pulse of 400 mJ/cm2 and a pulse repetition rate of 20 Hz, indicate that sclerostomies of 300 microns diameter can be reliably formed if an en-face air jet is built into the mask to raise the pressure in the target area, preventing aqueous flooding. PMID:8325423

  19. Detection of lead in soil with excimer laser fragmentation fluorescence spectroscopy (ELFFS)

    SciTech Connect

    Choi, J.H.; Damm, C.J.; O'Donovan, N.J.; Sawyer, R.F.; Koshland, C.P.; Lucas, D.

    2004-03-01

    Excimer laser fragmentation fluorescence spectroscopy (ELFFS) is used to monitor lead in soil sample and investigate laser-solid interactions. Pure lead nitrate salt and soil doped with lead nitrate are photolyzed with 193 nm light from an ArF excimer at fluences from 0.4 to 4 J/cm{sup 2}. Lead emission is observed at 357.2, 364.0, 368.3, 373.9 and 405.8 nm. Time-resolved data show the decay time of the lead emission at 405.8 nm grows with increasing fluence, and a plasma is formed above fluences of 2 J/cm{sup 2}, where a strong continuum emission interferes with the analyte signal. Fluences below this threshold allow us to achieve a detection limit of approximately 200 ppm in soil.

  20. Measurement and evaluation methods for beam characterization of commercial excimer lasers

    NASA Astrophysics Data System (ADS)

    Albrecht, Hans Stephen; Rebhan, Ulrich; Mann, Klaus R.; Ohlenbusch, J.

    1996-11-01

    This paper describes the specific requirements for measurement of excimer laser beam profiles for standardized characterization 'of commercial excimer lasers. A corresponding measurement system is presented which allows a simultaneous characterization of energy density distribution in the near field as well as in the focal plane of a lens (far field). Specially adapted UV-cameras make possible sings pulse diagnostic. Beam widths are calculated from the digitized camera data by different methods corresponding to the proposals of ISO 11146 (second moment, moving knife edge, and moving slit) and the results are compared. In particular, the influence of background signals as well as the typical shape of energy density distribution in the near field to the determined beam widths are analyzed.

  1. Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation

    SciTech Connect

    Ikeda, Akihiro; Nishi, Koji; Ikenoue, Hiroshi; Asano, Tanemasa

    2013-02-04

    Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 10{sup 20}/cm{sup 3} without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated.

  2. Improved model for the angular dependence of excimer laser ablation rates in polymer materials

    SciTech Connect

    Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

    2009-10-26

    Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

  3. Narrow bandwidth tuning of rhodamine 6G dye pumped by a XeCl excimer laser

    SciTech Connect

    Shangguan Cheng; Ling Ying-yi; Wang Yi-man; Dou Ai-rong; Huang Dan-hong

    1986-03-01

    In this paper the experimental study for narrow bandwidth tuning of ethylene glycol solution of rhodamine 6G pumped by a XeCl excimer laser is reported. The tunable range from 572.7 nm to 612.9 nm with linewidth of 0.004 nm has been obtained. The conversion efficiency is 16.0%. The experimental results of seven other dyes are also presented.

  4. Holographic Generation Of Gratings With Periodicities Below 150 nm With An Excimer Laser

    NASA Astrophysics Data System (ADS)

    Ahlhorn, T.; Pohlmann, Hauke; Kotthaus, Jorg P.

    1989-04-01

    Holographic generation of gratings with periodicities down to 140nm in thin polymethyl methacrylate (PMMA) layers on Si-substrates using a narrow band KrF-excimer laser (λ=248 nm) is reported. At low single pulse energy densities (<3OmJ/cm2) the gratings are prepared by conventional photolithography. At higher single pulse energy densities (>70mJ/cm2) we directly write gratings in the PMMA by photoetching (ablation).

  5. Pulsed laser deposition of polyhydroxybutyrate biodegradable polymer thin films using ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Kecskemeti, G.; Smausz, T.; Kresz, N.; Tóth, Zs.; Hopp, B.; Chrisey, D.; Berkesi, O.

    2006-11-01

    We demonstrated the pulsed laser deposition (PLD) of high quality films of a biodegradable polymer, the polyhydroxybutyrate (PHB). Thin films of PHB were deposited on KBr substrates and fused silica plates using an ArF ( λ = 193 nm, FWHM = 30 ns) excimer laser with fluences between 0.05 and 1.5 J cm -2. FTIR spectroscopic measurements proved that at the appropriate fluence (0.05, 0.09 and 0.12 J cm -2), the films exhibited similar functional groups with no significant laser-produced modifications present. Optical microscopic images showed that the layers were contiguous with embedded micrometer-sized grains. Ellipsometric results determined the wavelength dependence ( λ ˜ 245-1000 nm) of the refractive index and absorption coefficient which were new information about the material and were not published in the scientific literature. We believe that our deposited PHB thin films would have more possible applications. For example to our supposal the thin layers would be applicable in laser induced forward transfer (LIFT) of biological materials using them as absorbing thin films.

  6. Vessel wall perforation mechanism of the excimer laser-assisted non-occlusive anastomosis technique.

    PubMed

    Bremmer, Jochem; van Doormaal, Tristan P C; Verweij, Bon H; van der Zwan, Albert; Tulleken, Cornelius A F; Verdaasdonk, Rudolf

    2016-08-01

    The excimer laser assisted non-occlusive anastomosis (ELANA) technique is used to make anastomoses on intracerebral arteries. This end-to-side anastomosis is created without temporary occlusion of the recipient artery using a 308-nm excimer laser with a ring-shaped multi-fiber catheter to punch an opening in the arterial wall. Over 500 patients have received an ELANA bypass. However, the vessel wall perforation mechanism of the laser catheter is not known exactly and not 100 % successful. In this study, we aimed to understand the mechanism of ELANA vessel perforation using specialized imaging techniques to ultimately improve its effectiveness. High-speed imaging, high-contrast imaging, and high-sensitivity thermal imaging were used to study the laser wall perforation mechanism and reveal the mechanical and thermal effects involved. In vitro, rabbit arteries were exposed with the special designed laser catheter in a setup representative for the clinical setting, in which blood was replaced with a transparent UV absorbing liquid for visualization. We observed that laser vessel wall perforation was caused by explosive vapor bubbles tearing through the vessel wall, mostly within the first 20 of the total 200 pulses. Thermal effects were minimal. Unsymmetrical tension in the vessel wall inducing migration of the flap during laser exposure was observed in case of unsuccessful wall perforations. The laser wall perforation mechanism in the ELANA technique is primarily mechanical. Symmetric tension in the recipient vessel wall is essential and should be trained by neurosurgeons. PMID:27220531

  7. Elaboration of excimer lasers dosimetry for bone and meniscus cutting and drilling using optical fibers

    NASA Astrophysics Data System (ADS)

    Jahn, Renate; Dressel, Martin; Neu, Walter; Jungbluth, Karl-Heinz

    1991-05-01

    In order to optimize bone and cartilage ablation, various excimer laser systems at 308 nm wavelength (pulse width 28 ns, 60 ns, 300 ns) and tapered fibers (core diameter 400 micrometers , 600 micrometers , 1000 micrometers ) were combined. By varying the major parameters such as fluence, pulselength, repetition rate, fiber diameter, medium, manner of application (drilling, cutting); analysis was made of the interaction of the excimer laser beam with different organic material (meniscus, bone tissue). More than 300 cuts and drillings have been realized with different parameters. The ablation rate mainly depends on fluence, repetition rate and pulse duration. The achieved ablation rate was 3 micrometers /pulse in bone. The drilling speed of the meniscus was 6 mm/s. The samples showed no carbonization at all, when being cut or drilled in liquid medium. This might be a breakthrough in fiber guided excimer laser surgery. From these and further experiments the authors obtained the dosimetry, which will be the basis for the elaboration of necessary operation guidelines for accident surgery.

  8. Practical resolution enhancement effect by new complete antireflective layer in KrF excimer laser lithography

    NASA Astrophysics Data System (ADS)

    Ogawa, Tohru; Kimura, Mitsumori; Gocho, Tetsuo; Tomo, Yoichi; Tsumori, Toshiro

    1993-08-01

    A new complete anti-reflective layer (ARL) for KrF excimer laser lithography, which becomes an excimer laser lithography to a practical mass production tool beyond 0.35 micrometers rule devices, is developed. This new ARL, whose material is a type of hydro silicon oxynitride film (SiOxNy:H), can be applied to tungsten silicide (W-Si) and even to aluminum silicon (Al- Si) substrates by controlling deposition conditions in plasma enhanced chemical vapor deposition systems. Using this SiOxNy:H film with 30 nm and 25 nm thicknesses on W-Si and Al-Si substrates respectively, critical dimension variations for both substrates are drastically reduced to within 0.02 micrometers for 0.30 micrometers imaging. On actual device structures, with these SiOxNy:H film as an ARL, notching effects by halation are completely reduced. Moreover, these SiOxNy:H film can not only be deposited with topographical uniformity but also etched with conventional SiO2 etching conditions. Another advantage with ARL is a depth of focus enhancement effect. With a SiOxNy:H film depth of focus for the critical dimension is enlarged more than 23% for 0.35 micrometers line and space patterns. Accordingly, practical resolution is enhanced. From the above effect, the limitations of KrF excimer laser lithography for ideal substrate conditions are considered from the point of view of optimal projection lens NA for various feature sizes.

  9. Expression of Epidermal c-Kit+ of Vitiligo Lesions Is Related to Responses to Excimer Laser

    PubMed Central

    Park, Oun Jae; Han, Ji Su; Lee, Sang Hyung; Park, Chan-Sik; Won, Chong Hyun; Lee, Mi Woo; Choi, Jee Ho

    2016-01-01

    Background The survival and growth of melanocytes are controlled by the binding of stem cell factor to its cell surface receptor c-kit+ (CD117). We have observed that c-kit+ melanocytes existed in some lesions of vitiligo, while Melan A+ cells were absent. Objective To verify possible relation between c-kit+ expression and treatment response in non-segmental vitiligo lesions Methods Skin biopsies were done from the center of the 47 lesions from the 47 patients with non-segmental vitiligo. Expression of c-kit+ and Melan A, and amounts of melanin in the epidermis were assessed in each lesion, and treatment responses to excimer laser were evaluated. Results Thirty-five of the 47 lesions (74.5%) had c-kit+ phenotypes. There was significant difference of c-kit staining value between good responders in 3 months of excimer laser treatment (average of 24 sessions) and the others. Conclusion c-Kit expression in vitiliginous epidermis may be related to better treatment responses to excimer laser. PMID:27489428

  10. Photoacoustic injury and bone healing following 193nm excimer laser ablation.

    PubMed

    Lustmann, J; Ulmansky, M; Fuxbrunner, A; Lewis, A

    1992-01-01

    The argon-fluoride excimer laser was investigated as a cutting-ablating tool for bone surgery. A total of 52 rats were divided into two experimental groups and two control groups. In one experimental group cortical bone defects were made; in another experimental group defects penetrating into the medullary space were performed. In the two control groups similar defects were achieved using water-cooled carbide burs. The rats were sacrificed on each of the 3, 7, 10, 20, 30, and 40 postoperative day. The cortical bone, the medullary space, and the extrabony tissue were examined by means of light microscopy. In both experimental groups, bone damage, represented by osteocyte destruction, extended to 1,050-1,450 microns ahead from the irradiated site, and bone healing was very much impaired. In the control groups no histological changes could be identified and bone healing appeared to be within normal limits. We believe this extensive bone damage, following 193 nm irradiation, to be a result of photoacoustic waves propagating in the bone following each pulse. In view of our results we feel that excimer lasers presently in use are not suitable for bone surgery. This problem of photoacoustic damage can be overcome in one of two ways: by designing a CW excimer laser or by reducing the pulse width to the picosecond regime. PMID:1495367

  11. A study of structure formation on PET, PBT, and PS surfaces by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Kim, Jongdae

    Usually polymer surface treatment is performed to modify surface layers by inserting some functional group and/or by inducing roughness on surfaces to improve their wettability, printability, and adhesion to other polymers or metals. In this work, different polymer surfaces were treated using an excimer laser (LPX 240i, Lambda Physik). Polystyrene, polyethylene terephtalate, and polybutylene terephtalate were chosen as model materials for this study. Films were made by cast film processing and stretched with biaxial stretching machine. With excimer laser treatment on polymer surfaces, it was found that we could produce 1--2 micron size structures depending on material properties and film processing conditions. Materials with lower UV absorption coefficient produced double digit micron size structures, while those with higher UV absorption coefficients produced single digit micron size structures. In all these cases the structures formed only on stretched films. In addition to those microstructure developments, the determination of ablation threshold fluence was of interest mainly for understanding fundamentals of ablation behavior and technical applications. In this study, ablation thresholds were measured by various methods including ablation depth, ablation weight, and ablation sound level measurements. Among these methods, we confirmed that the measurement by ablation sound level gives the most reliable results, because this method is based on single pulse ablation. To understand the ablation phenomenon, and how microstructures can be developed during ablation, different material processing and excimer laser conditions were chosen for experimentation. During our experiments, we observed incubation phenomenon during laser ablation and showed that this incubation was significant for materials with low UV absorption coefficients. Based on UV absorption value change after excimer laser irradiation, we proposed a mechanism to explain the ablation of PS films. From

  12. Composition of the excimer laser-induced plume produced during LASIK refractive surgery

    NASA Astrophysics Data System (ADS)

    Glickman, Randolph D.; Liu, Yun; Mayo, George L.; Baribeau, Alan D.; Starck, Tomy; Bankhead, Tom

    2003-07-01

    Because of concerns about potential hazards to surgical personnel of the plume associated with laser refractive surgery, this study was performed to characterize the composition of such plumes. Filter elements were removed from the smoke evacuator of a VISX S3 excimer laser (filter pore size ~0.3 microns) and from a Mastel Clean Room ( filter pore size ~0.2 microns) used with a LADARVISION excimer laser. The filters from both laser systems captured the laser-induced plumes from multiple, routine, LASIK patient procedures. Some filters were processed for scanning electron microscopy, while others were extracted with methanol and chloroform for biochemical analysis. Both the VISX "Final Air" filter and the Mastel "Clean Room" filter captured material that was not observed in filters that had clean operating room air only passed through them. In the VISX system, air flows through the filter unit parallel to the filter matrix. SEM analysis showed these filters captured discrete particles of 0.3 to 3.0 microns in size. In the Mastel Clean Room unit, air flows orthogonally through the filter, and the filter matrix was heavily layered with captured debris so that individual particles were not readily distinguished. Amino acid analysis and gel electrophoresis of extracted material revealed proteinaceous molecules as large as 5000 molecular weight. Such large molecules in the laser plume are not predicted by the existing theory of photochemical ablation. The presence of relatively large biomolecules may constitute a risk of allergenic reactions in personnel exposed to the plume, and also calls into question the precise mechanism of excimer laser photochemical ablation. Supported by the RMG Research Endowment, and Research to Prevent Blindness

  13. Custom specific fabrication of integrated optical devices by excimer laser ablation of polymers

    NASA Astrophysics Data System (ADS)

    Klotzbuecher, Thomas; Popp, Martin; Braune, Torsten; Haase, Jens; Gaudron, Anne; Smaglinski, Ingo; Paatzsch, Thomas; Bauer, Hans-Dieter; Ehrfeld, Wolfgang

    2000-06-01

    Excimer laser ablation was used for direct writing of multimode waveguide structures with passive fiber alignment grooves in polymers. First, integrated optical multimode components were simulated by the method of beam propagation to optimize the optical performance of the design. Then the CNC codes for laser machining were created directly from the corresponding CAD data. ArF Excimer laser radiation of wavelength (lambda) equals 193 nm was used for ablation of adjacent grooves with a cross sectional area of 50 X 50 micrometers 2 and lengths in the order of several mm. The laser-written grooves were filled with a liquid pre-polymer which after UV-curing served as the waveguiding structures. The smoothest surfaces during laser ablation were achieved by applying several ablation scans with reduced material removal rates but higher feedrates. Debris formation, also influencing the surface roughness, was suppressed or minimized by making use of capable polymers. With the method of laser ablation linear waveguides of length 1 equals 10 mm with insertion losses Li in the rang of 1.3 to 1.9 dB have been realized for (lambda) equals 1310 nm, depending on the polymer used. By means of 1 X 2-splitters, 4 X 4 as well as 4 X 16 starcouplers it was shown that laser ablation is a well suited tool for rapid prototyping of integrated optical multimode elements.

  14. The development and progress of XeCl Excimer laser system

    NASA Astrophysics Data System (ADS)

    Zhang, Yongsheng; Ma, Lianying; Wang, Dahui; Zhao, Xueqing; Zhu, Yongxiang; Hu, Yun; Qian, Hang; Shao, Bibo; Yi, Aiping; Liu, Jingru

    2015-05-01

    A large angularly multiplexed XeCl Excimer laser system is under development at the Northwest Institute of Nuclear Technology (NINT). It is designed to explore the technical issues of uniform and controllable target illumination. Short wavelength, uniform and controllable target illumination is the fundamental requirement of high energy density physics research using large laser facility. With broadband, extended light source and multi-beam overlapping techniques, rare gas halide Excimer laser facility will provide uniform target illumination theoretically. Angular multiplexing and image relay techniques are briefly reviewed and some of the limitations are examined to put it more practical. The system consists of a commercial oscillator front end, three gas discharge amplifiers, two electron beam pumped amplifiers and the optics required to relay, encode and decode the laser beam. An 18 lens array targeting optics direct and focus the laser in the vacuum target chamber. The system is operational and currently undergoing tests. The total 18 beams output energy is more than 100J and the pulse width is 7ns (FWHM), the intensities on the target will exceed 1013W/cm2. The aberration of off-axis imaging optics at main amplifier should be minimized to improve the final image quality at the target. Automatic computer controlled alignment of the whole system is vital to efficiency and stability of the laser system, an array of automatic alignment model is under test and will be incorporated in the system soon.

  15. Photochemical and thermal changes in tissue autofluorescence during excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    McAuliffe, Daniel J., Sr.; Jacques, Steven L.; Hayes, Amy S.

    1990-06-01

    A striking consequence of 248-nm excimer laser irradiation of skin is a stable vivid blue fluorescence easily visualized under UVA illumination. Its spectral properties (excitation maximum at "335 nm; emission maximum at ''43O nm) are somewhat similar to those of the fluorescent pigments associated with aging of tissue and peroxidation of lipids, and the fluorescent pigments formed during exposure to high temperatures. This study explores the spectral properties, magnitude, dose response, and laser pulse intensity dependence of this phenomenon in both isolated stratum corneum and epidermal cell suspensions from human skin.

  16. Excimer laser phototherapy for the dissolution of vascular obstruction

    DOEpatents

    Gruen, D.M.; Young, C.E.; Pellin, M.J.

    1984-01-09

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290 to 400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. 2 figures.

  17. Excimer laser phototherapy for the dissolution of abnormal growth

    DOEpatents

    Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

    1987-01-01

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290-400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area.

  18. Excimer laser phototherapy for the dissolution of abnormal growth

    DOEpatents

    Gruen, D.M.; Young, C.E.; Pellin, M.J.

    1985-02-19

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290 to 400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area. 6 figs.

  19. Beam pen lithography based on focused laser diode beam with single microlens fabricated by excimer laser.

    PubMed

    Hasan, Md Nazmul; Lee, Yung-Chun

    2015-02-23

    A method is proposed to minimize the focused spot size of an elliptically-diverging laser diode beam by means of a circular aperture and a single plano-convex aspherical microlens. The proposed microlens is fabricated using an excimer laser dragging method and has two different profiles in the x- and y-axis directions. The focused spot size of the beam is examined both numerically and experimentally. The feasibility of the proposed approach for beam pen lithography applications is demonstrated by patterning dotted, straight-line and spiral features on a photo resist layer followed by thin gold layer deposition and metal lift-off. The minimum feature size for dotted pattern is around 2.57 μm, while the minimum line-widths for straight-line and spiral pattern are 3.05 μm and 4.35 μm, respectively. Thus, the technique can be applied to write any arbitrary pattern for high-resolution lithography. PMID:25836486

  20. Formation of a narrow beam from an excimer laser pumped by gamma rays

    SciTech Connect

    Lazhintsev, B V; Nor-Arevyan, V A

    2002-06-30

    A laser pumped by a travelling gamma-radiation wave and consisting of a cylindrical part forming spontaneous superradiation and a conical amplifier is considered. The energy parameters of an excimer conical KrF amplifier are investigated. The factors influencing the divergence of induced radiation at the output of the conical amplifier are analysed for various durations of a pump pulse. It is shown that the divergence of radiation emitted by the laser with an active medium length of 10 m may be as high as 10{sup -4} rad. The scheme of laser-beam focusing on the target for the purposes of laser-induced fusion is considered. (control of laser radiation parameters)

  1. Surface modification of polytetrafluoroethylene by excimer-laser radiation

    SciTech Connect

    Nishii, M.; Sugimoto, S.; Shimizu, Y.; Suzuki, N.; Kewanishi, S.; Nagese, T.; Endo, M.; Eguchi, Y.

    1993-12-31

    The adhesive strength of polytetrafluoroethylene (PTFE) films was enhanced remarkably by KrF-laser irradiation in air when a small amount of aromatic polymers such as aromatic polyester, polyetheretherketone and polyimide were blended with PTFE. From the surface analysis of the laser-irradiated PTFE by an X-ray photoelectron spectroscopy and a scanning electron microscopy, it was found that the enhancement in the adhesive properties was attributable to both the chemical effect owing to the formation of the polar groups such as carbonyl group and ethylene linkage and the physical one owing to the formation of the uneveness by the KrF-laser irradiation.

  2. Finite element simulation for ultraviolet excimer laser processing of patterned Si/SiGe/Si(100) heterostructures

    SciTech Connect

    Conde, J. C.; Chiussi, S.; Gontad, F.; Gonzalez, P.; Martin, E.; Serra, C.

    2010-07-05

    Ultraviolet (UV) Excimer laser assisted processing is an alternative strategy for producing patterned silicon germanium heterostructures. We numerically analyzed the effects caused by pulsed 193 Excimer laser radiation impinging on patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bilayers deposited on a crystalline silicon substrate [Si(100)]. The proposed two dimensional axisymmetric numerical model allowed us to estimate the temperature and concentration gradients caused by the laser induced rapid melting and solidification processes. Energy density dependence of maximum melting depth and melting time evolution as well as three dimensional temperature and element distribution have been simulated and compared with experimentally obtained results.

  3. XeCl excimer laser with new prism resonator configurations and its performance characteristics

    SciTech Connect

    Benerji, N. S. E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra E-mail: bsingh@rrcat.gov.in

    2015-07-15

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

  4. XeCl excimer laser with new prism resonator configurations and its performance characteristics.

    PubMed

    Benerji, N S; Singh, A; Varshnay, N; Singh, Bijendra

    2015-07-01

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications. PMID:26233361

  5. Excimer laser coronary angioplasty: experience with a prototype multifibre catheter in patients with stable angina pectoris.

    PubMed

    Kochs, M; Haerer, W; Eggeling, T; Hoeher, M; Schmidt, A; Hombach, V

    1992-03-01

    Percutaneous excimer laser coronary angioplasty (ELCA) was performed in a first group of 20 patients with stable angina pectoris caused by significant coronary stenosis, and long-term follow-up was evaluated. Prototype 4 to 5.5 French multifibre catheters with 18-20 quartz fibres of 100 microns diameter, concentrically arranged around a central lumen for taking up a guide wire, were coupled to a commercial XeCl excimer laser. Energy was delivered at a wavelength of 308 nm with a pulse duration of 60 or 120 ns. Operating at a repetition rate of 20 Hz, mean energy transmission was 13.4 +/- 6.8 mJ per pulse. In all but one patient the lesion could be passed by the catheter. Percent diameter stenosis decreased from 77.1 +/- 10.8% to 53.1 +/- 11.8% after ELCA. Complications were frequently observed, intracoronary thrombus formation in eight instances, dissection in six patients and spasm in five cases, causing total vessel occlusion in five procedures. All complications could be managed efficaciously by thrombolytic and vasodilating drugs and/or balloon angioplasty. Subsequent PTCA was performed in case of complication or insufficient stenosis reduction after ELCA in 18 patients with adequate results (residual stenosis, 28.5 +/- 10.2%). Long-term follow-up angiography, which could be performed in 16 of 19 laser treatments, demonstrated significant restenosis in only three patients. Our preliminary results suggest that, using ELCA, ablation of atherosclerotic lesions is feasible in most cases. However, compared with PTCA, stenosis reduction is significantly less, and the acute complication rate is much higher. Thus, further improvements of the catheter system are necessary in order to realize the advantages of excimer laser ablation, which can be demonstrated by experimental studies. PMID:1597220

  6. Random noise can help to improve synchronization of excimer laser pulses

    PubMed Central

    Mingesz, Róbert; Barna, Angéla; Mellár, János

    2016-01-01

    Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications. PMID:26998325

  7. Random noise can help to improve synchronization of excimer laser pulses.

    PubMed

    Mingesz, Róbert; Barna, Angéla; Gingl, Zoltán; Mellár, János

    2016-02-01

    Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications. PMID:26998325

  8. Effects of xenon gas on generation and propagation of shock waves in the cavity of excimer laser

    NASA Astrophysics Data System (ADS)

    Kosugi, Shinichiroh; Maeno, Kazuo; Honma, Hiroki

    1993-05-01

    High repetition rate excimer lasers are expected for wide industrial application. The power of excimer laser, however, decreases rapidly in a higher repetition rate operation. Shock or acoustic waves, which are caused by the periodic pulse discharge, may limit the repetition rate of an excimer laser up to 2.5 kHz. Such waves cause inhomogeneity of gas density in the discharge region of the excimer laser. In high repetition rate operation this inhomogeneity remains at the next discharge. Arcing may be generated by this inhomogeneity and the homogeneous excitation of the laser gas is obstructed. Although these phenomena have been reported, the research for the effects of shock waves has remained insufficient. And the relation between these shock waves and discharge phenomena has not been clarified. To resolve this problem, we developed a scaling model chamber of a UV preionized excimer laser cavity with windows for flow visualization. We report the first result by using this model and Schlieren technique in a pure helium gas case. In our experiment three types of shock waves are found in the discharge cavity. Those shock waves are generated from the boundary of the main discharge area, from sparking pin gaps, and from the main electrode surfaces. In this study we focus on the effect of xenon gas on the generation and the propagation of shock waves. Components of the Xe-Cl excimer laser gas are helium, xenon, and hydrogen chloride. In those gases xenon has the largest molecular weight of 131.29. So we conclude xenon plays an important role in the shock wave propagation and in discharge phenomenon.

  9. AlGaAs growth by OMCVD using an excimer laser

    SciTech Connect

    Warner, J.D.; Wilt, D.M.; Pouch, J.J.; Aron, P.R.

    1986-12-01

    AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H/sub 2/, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.

  10. AlGaAs growth by OMCVD using an excimer laser

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Wilt, David M.; Pouch, John J.; Aron, Paul R.

    1986-01-01

    AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H2, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.

  11. Coloring linens with excimer lasers to simulate the body image of the Turin Shroud.

    PubMed

    Baldacchini, Giuseppe; Di Lazzaro, Paolo; Murra, Daniele; Fanti, Giulio

    2008-03-20

    The body image of the Turin Shroud has not yet been explained by traditional science; so a great interest in a possible mechanism of image formation still exists. We present preliminary results of excimer laser irradiation (wavelength of 308 nm) of a raw linen fabric and of a linen cloth. The permanent coloration of both linens is a threshold effect of the laser beam intensity, and it can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the pulse width and time sequence of laser shots. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after laser irradiation that at first did not generate a clear image. The results are compared with the characteristics of the Turin Shroud, reflecting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image. PMID:18709075

  12. Multi-level diffractive optical elements produced by excimer laser ablation of sol-gel.

    PubMed

    Neiss, Estelle; Flury, Manuel; Mager, Loïc; Rehspringer, Jean-Luc; Fort, Alain; Montgomery, Paul; Gérard, Philippe; Fontaine, Joël; Robert, Stéphane

    2008-09-01

    Material ablation by excimer laser micromachining is a promising approach for structuring sol-gel materials as we demonstrate in the present study. Using the well-known direct etching technique, the behaviour of different hybrid organic/inorganic self-made sol-gel materials is examined with a KrF* laser. Ablated depths ranging from 0.1 to 1.5 microm are obtained with a few laser pulses at low fluence (< 1 J/cm(2)). The aim is to rapidly transfer surface relief multi-level diffractive patterns in such a substrate, without intermediate steps. The combination with the 3D profilometry technique of coherence probe microscopy permits to analyse the etching process with the aim of producing multi-level Diffractive Optical Elements (DOE). Examples of four-level DOEs with 10 microm square elementary cells are presented, as well as their laser reconstructions in the infrared. PMID:18773015

  13. Coloring linens with excimer lasers to simulate the body image of the Turin Shroud

    NASA Astrophysics Data System (ADS)

    Baldacchini, Giuseppe; di Lazzaro, Paolo; Murra, Daniele; Fanti, Giulio

    2008-03-01

    The body image of the Turin Shroud has not yet been explained by traditional science; so a great interest in a possible mechanism of image formation still exists. We present preliminary results of excimer laser irradiation (wavelength of 308 nm) of a raw linen fabric and of a linen cloth. The permanent coloration of both linens is a threshold effect of the laser beam intensity, and it can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the pulse width and time sequence of laser shots. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after laser irradiation that at first did not generate a clear image. The results are compared with the characteristics of the Turin Shroud, reflecting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  14. Combination Of Narrow Bandwidth Excimer Laser And Monochromatic Reduction Projection Lens

    NASA Astrophysics Data System (ADS)

    Kajiyama, K.; Saito, K.; Moro, N.; Maeda, Y.; Natsuaki, H.

    1988-01-01

    This paper will discuss the problems associated with excimer laser photo-lithography -the combination of a KrF narrow band width excimer laser (non-injection locked type) with a large field fused silica monochromatic reduction lens. An excimer laser with a KrF narrow bandwidth, in combination with a large field monochromatic lens which is appropriate for use with such laser, have been developed and tested. The system's resolution capability has been confirmed at 0.4 um L/S with MP2400 resist. The laser has been designed so as to be installed and maintained in a clean room environment as well as to have a very narrow spectrum line. A very narrow band-width beam, down to 0.003nm, has been attained through a stable resonator with more than 20mJ pulse energy. The ultra-compact laser head (300mm x 545mm x 1100mm) contains a small laser discharge unit (182mm x 156mm x 584mm), and no amplifier because the oscillator is highly efficient in spite of the narrow line emission. Maintenance is much easier in the clean room environment. Users can replace the discharge unit as easily as they would change Hg-lamp, only taking twenty minutes, and while they clean the window and check the electrodes of the removed unit, the laser can be operated with the easily installed replacement -already passivated discharge unit. The laser head unit is separated from a gas circulating unit and trigger pulse circuit - vibration, heat, EMI noise and particle generation. Therefore, it can be installed even in the thermal clean chamber of a stepper. The N.A. (numerical aperture) of the monochromatic lens is 0.36 and the field size is 15mm x 15mm. In fact, three kinds of lenses with N.A.s of 0.4, 0.35 and 0.3 respectively, were designed and individually evaluated for their OTF's and defocus's dependence on the light source's spectral width, and also their co-relationship. In parallel, simulations on the relationship between each lens' chromatic aberration and laser spectral width were completed and

  15. Sample temperature profile during the excimer laser annealing of silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Caninenberg, M.; Verheyen, E.; Kiesler, D.; Stoib, B.; Brandt, M. S.; Benson, N.; Schmechel, R.

    2015-11-01

    Based on the heat diffusion equation we describe the temperature profile of a silicon nanoparticle thin film on silicon during excimer laser annealing using COMSOL Multiphysics. For this purpose system specific material parameters are determined such as the silicon nanoparticle melting point at 1683 K, the surface reflectivity at 248 nm of 20% and the nanoparticle thermal conductivity between 0.3 and 1.2 W/m K. To validate our model, the simulation results are compared to experimental data obtained by Raman spectroscopy, SEM microscopy and electrochemical capacitance-voltage measurements (ECV). The experimental data are in good agreement with our theoretical findings and support the validity of the model.

  16. Sub-500-nm patterning of glass by nanosecond KrF excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Bekesi, J.; Meinertz, J.; Simon, P.; Ihlemann, J.

    2013-01-01

    The surface of flint glass of type F2 is patterned by nanosecond KrF excimer laser ablation. Strong UV absorption provides a comparatively low ablation threshold and precise ablation contours. By using a two-grating interferometer, periodic surface patterns with 330 nm period and 100 nm modulation depth are obtained. This method enables the fabrication of 7 mm×13 mm wide grating areas with perfectly aligned grooves without the need of high-precision sample positioning. By double exposure, crossed gratings with adjustable depths in the two orthogonal directions can be generated.

  17. Surface modification and metallization of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1993-12-01

    The surface chemical modification of poly(tetrafluoroethylene) and poly(tetrafluoroethylene- co-hexafluoropropylene) films was carried out in hydrazine gas photolyzed with ArF excimer laser irradiation. The contact angle of the modified surfaces with water changed from 130° to 30° due to the reaction with hydrazine. Nitrogen on the surface was detected with x-ray photoelectron spectroscopy, suggesting that amino groups were introduced onto the surface. In addition, on the basis of hydrophilic behavior, we succeeded in selective-area electroless plating of nickel metal on the chemically modified surface.

  18. Pulsed Excimer Laser Processing for Cost-Effective Solar Cells

    NASA Technical Reports Server (NTRS)

    Wong, D.

    1985-01-01

    Residual lattice damage by 5 keV ion implantation and surface flaws induced by wafer cleaning are proven to affect the V sub oc more adversely for laser annealed cells than conventional thermal diffusion. However, an alternative, molecular implantation of molecular species holds potential. The first experimental results are encouraging. The lack of a commercially available mass analyzed implantation with low energy, high fluence ions is constraining.

  19. New excimer laser technique for the correction of strabismus and diplopia

    NASA Astrophysics Data System (ADS)

    Azar, Dimitri T.

    1994-06-01

    We used the ArF excimer laser to determine the feasibility of performing prismatic photoablations in model eyes (plastic spheres simulating the eye), and in rabbit corneas. This would correct diplopia and small angles of deviation, and result in minimal refractive alterations. We modified excimer laser delivery system that achieved the desired corneal contour of prismatic ablations. 193-nm argon fluoride laser was used at fluence of 160 mJ/cm2 and ablation rate 5 Hz. 5.0-mm diameter, 40 um corneal epithelial ablation were followed by 5.0- mm diameter, prismatic photokeratectomy (PPK). We were able to achieve prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic effect. In rabbits re-epithelialization of the 5-mm ablations was complete by day 3, and corneal haze was not observed by gross examination. Epithelial hyperplasia and subepithelial scarring were noted at the deep edges. PPK holds important therapeutic potential for fine-tuning results of conventional strabismus surgery, and for patients with stable diplopia following nerve palsy and ocular surgery.

  20. Towards excimer-laser-based stereolithography: a rapid process to fabricate rigid biodegradable photopolymer scaffolds.

    PubMed

    Beke, S; Anjum, F; Tsushima, H; Ceseracciu, L; Chieregatti, E; Diaspro, A; Athanassiou, A; Brandi, F

    2012-11-01

    We demonstrate high-resolution photocross-linking of biodegradable poly(propylene fumarate) (PPF) and diethyl fumarate (DEF) using UV excimer laser photocuring at 308 nm. The curing depth can be tuned in a micrometre range by adjusting the total energy dose (total fluence). Young's moduli of the scaffolds are found to be a few gigapascal, high enough to support bone formation. The results presented here demonstrate that the proposed technique is an excellent tool for the fabrication of stiff and biocompatible structures on a micrometre scale with defined patterns of high resolution in all three spatial dimensions. Using UV laser photocuring at 308 nm will significantly improve the speed of rapid prototyping of biocompatible and biodegradable polymer scaffolds and enables its production in a few seconds, providing high lateral and horizontal resolution. This short timescale is indeed a tremendous asset that will enable a more efficient translation of technology to clinical applications. Preliminary cell tests proved that PPF : DEF scaffolds produced by excimer laser photocuring are biocompatible and, therefore, are promising candidates to be applied in tissue engineering and regenerative medicine. PMID:22696484

  1. Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Kushner, Mark J.

    2011-10-01

    Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

  2. Ablation of bone and polymethylmethacrylate by an XeCl (308 nm) excimer laser

    SciTech Connect

    Yow, L.; Nelson, J.S.; Berns, M.W.

    1989-01-01

    One of the main problems in orthopaedics is the surgical removal of hard substances, such as bone and polymethylmethacrylate (PMMA). Such materials are often very difficult to remove without mechanical trauma to the remaining tissue. This study investigated the feasibility of the ultraviolet 308 nm excimer laser in the ablation of these materials. The beam was delivered through a 1 mm-diameter fiber optic at 40 Hz with energy densities at the target surface of 20-80 J/cm2 per pulse. The goal of the study was to establish the ideal dosimetry for removing bone and PMMA with minimum trauma to the adjacent tissue. Histology revealed that the 308 nm laser effectively removed bone leaving a thermal damage zone of only 2-3 microns in the remaining tissue. Increasing the energy per pulse gave correspondingly larger and deeper cuts with increasing zones of thermal damage. The excimer laser was also effective in the ablation of PMMA, creating craters in the substrate with a thermal damage zone of 10-40 microns. The debris from both substrates was evaluated.

  3. 193 nm Excimer laser processing of Si/Ge/Si(100) micropatterns

    NASA Astrophysics Data System (ADS)

    Gontad, F.; Conde, J. C.; Chiussi, S.; Serra, C.; González, P.

    2016-01-01

    193 nm Excimer laser assisted growth and crystallization of amorphous Si/Ge bilayer patterns with circular structures of 3 μm diameter and around 25 nm total thickness, is presented. Amorphous patterns were grown by Laser induced Chemical Vapor Deposition, using nanostencils as shadow masks and then irradiated with the same laser to induce structural and compositional modifications for producing crystalline SiGe alloys through fast melting/solidification cycles. Compositional and structural analyses demonstrated that pulses of 240 mJ/cm2 lead to graded SiGe alloys with Si rich discs of 2 μm diameter on top, a buried Ge layer, and Ge rich SiGe rings surrounding each feature, as predicted by previous numerical simulation.

  4. Colouring fabrics with excimer lasers to simulate encoded images: the case of the Shroud of Turin

    NASA Astrophysics Data System (ADS)

    Di Lazzaro, P.; Baldacchini, G.; Fanti, G.; Murra, D.; Santoni, A.

    2008-10-01

    The faint body image embedded into the Turin Shroud has not yet explained by traditional science. We present experimental results of excimer laser irradiation (wavelengths 308 nm and 193 nm) of a raw linen fabric and of a linen cloth, seeking for a possible mechanism of image formation. The permanent coloration of both linens is a threshold effect on the laser beam intensity and it can be achieved only in a surprisingly narrow range of irradiation parameters: the shorter the wavelength, the narrower the range. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after a laser irradiation that at first did not generate a clear image. The results are compared to the characteristics of the Turin Shroud, commenting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  5. Tribology and hardness of excimer-laser-processed titanium layers on cubic zirconia

    SciTech Connect

    Zaleski, M.A.; Jervis, T.R. . Dept. of Materials Science and Engineering Los Alamos National Lab., NM ); Mayer, J.W. . Dept. of Materials Science and Engineering)

    1993-02-01

    The authors have examined the wear and friction and surface hardness of excimer-laser-processed Ti layers on cubic zirconia substrates. The film exhibits a complex array of cracking following processing that is related to the crystallographic orientation of the substrate. The friction between the laser-processed layers and both steel and ruby pins is reduced by approximately one-third relative to that of untreated zirconia. In the untreated case, wear is characterized by pin wear and debris, whereas the laser-processed layer wears by film transfer to the pin. The surface hardness of the processed layer is lower than that of both the untreated zirconia and the deposited Ti film. Indentation tests indicate that the surface is brittle following processing.

  6. Formation of nickel silicides by excimer laser CVD of Ni(CO)4

    NASA Astrophysics Data System (ADS)

    Borsella, E.; Kompa, Karl L.; Reiner, H.; Schroeder, Hartmut

    1990-08-01

    Nickel silicides have been grown on single crystal silicon sub- strates. A XeCl excimer laser was used for all process steps: substrate cleaning, nickel deposition , silicide formation and annealing. The nickel films were grown by photodecoxnposition of Ni(CO)4 adsorbate layers with an excess of CO to prevent homogeneous nucleation and hence the formation of dust. The samples were analysed by X-ray fluorescence, SIMS and RBS. The results indicate that epitaxial silicide layers with a thickness of 50 ma can be obtained after careful choice of laser fluence and Ni film thickness. In an alternative approach we used a molecular beam of Ni(CO)4, part of which is laser excited prior to impinging on the substrate. This allows the combination of CVD and conventional MBE techniques. In this experiment we also investigate the interaction of photofragments with substrate surfaces and other processes responsible for material deposition.

  7. Laser mass spectrometric detection of AlH molecules as collision-free excimer laser photoproducts from aluminum alkyls

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Stuke, M.

    1988-08-01

    Aluminum hydride molecules AlH are detected and identified by tunable dye-laser mass spectroscopy as collision-free UV excimer laser photoproducts of the Al alkyls TEA (triethylaluminum (C 2H 5) 3Al) and TIBA (triisobutylaluminum ( i-C 4H 9) 3Al) at 248 and 193 nm. An internal energy distribution analysis of the photoproducts shows only minor vibrational excitation of ν″ = 1 and a Boltzmann-type rotational energy distribution with a temperature of about 0.03 eV, compared to the incoming photon energy of 5.0 or 6.42 eV.

  8. Excimer laser channel creation in polyethersulfone hollow fibers for compartmentalized in vitro neuronal cell culture scaffolds.

    PubMed

    Brayfield, Candace A; Marra, Kacey G; Leonard, John P; Tracy Cui, X; Gerlach, Jörg C

    2008-03-01

    Hollow fiber scaffolds that compartmentalize axonal processes from their cell bodies can enable neuronal cultures with directed neurite outgrowth within a three-dimensional (3-D) space for controlling neuronal cell networking in vitro. Controllable 3-D neuronal networks in vitro could provide tools for studying neurobiological events. In order to create such a scaffold, polyethersulfone (PES) microporous hollow fibers were ablated with a KrF excimer laser to generate specifically designed channels for directing neurite outgrowth into the luminal compartments of the fibers. Excimer laser modification is demonstrated as a reproducible method to generate 5microm diameter channels within PES hollow fiber walls that allow compartmentalization of neuronal cell bodies from their axons. Laser modification of counterpart flat sheet PES membranes with peak surface fluences of 1.2Jcm(-2) results in increased hydrophobicity and laminin adsorption on the surface compared with the unmodified PES surface. This is correlated to enhanced PC12 cell adhesion with increasing fluence onto laser-modified PES membrane surfaces coated with laminin when compared with unmodified surfaces. Adult rat neural progenitor cells differentiated on PES fibers with laser-created channels resulted in spontaneous cell process growth into the channels of the scaffold wall while preventing entrance of cell bodies. Therefore, laser-modified PES fibers serve as scaffolds with channels conducive to directing neuronal cell process growth. These hollow fiber scaffolds can potentially be used in combination with perfusion and oxygenation hollow fiber membrane sets to construct a hollow fiber-based 3-D bioreactor for controlling and studying in vitro neuronal networking in three dimensions between compartmentalized cultures. PMID:18060849

  9. Characterization of excimer laser ablation generated pepsin particles using multi-wavelength photoacoustic instrument

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Kecskeméti, G.; Smausz, T.; Ajtai, T.; Filep, A.; Utry, N.; Kohut, A.; Bozóki, Z.; Szabó, G.

    2012-05-01

    Preparation of organic thin layers on various special substrates using the pulsed laser deposition (PLD) technique is an important task from the point of view of bioengineering and biosensor technologies. Earlier studies demonstrated that particle ejection starts during the ablating laser pulse resulting in significant shielding effects which can influence the real fluence on the target surface and consequently the efficiency of layer preparation. In this study, we introduce a photoacoustic absorption measurement technique for in-situ characterization of ablated particles during PLD experiments. A KrF excimer laser beam ( λ=248 nm, FWHM=18 ns) was focused onto pepsin targets in a PLD chamber; the applied laser fluences were 440 and 660 mJ/cm2. We determined the wavelength dependence of optical absorption and mass specific absorption coefficient of laser ablation generated pepsin aerosols in the UV-VIS-NIR range. On the basis of our measurements, we calculated the absorbance at the ablating laser wavelength, too. We demonstrated that when the laser ablation generated pepsin aerosols spread through the whole PLD chamber the effect of absorptivity is negligible for the subsequent pulses. However, the interaction of the laser pulse and the just formed particle cloud generated by the same pulse is more significant.

  10. Raman scattering measurements in flames using a tunable KrF excimer laser.

    PubMed

    Wehrmeyer, J A; Cheng, T S; Pitz, R W

    1992-04-01

    Using a narrow-band tunable KrF excimer laser as a spontaneous vibrational Raman scattering source, we demonstrate that single-pulse concentration and temperature measurements, with only minimal fluorescence interference, are possible for all major species (O(2), N(2), H(2)O, and H(2)) at all stoichiometries (fuel-lean to fuel-rich) of H(2)-air flames. Photon-statistics-limited precisions in these instantaneous and spatially resolved single-pulse measurements are typically 5%, which are based on the relative standard deviations of single-pulse probability distributions. Optimal tuning of the narrow-band KrF excimer laser (248.623 nm) for the minimization of OH A(2)Sigma-X(2)II and O(2)B(3)Sigma(u)(-)-X(3)Sigma(g)(-) fluorescence interference is determined from fluorescence excitation spectra. In addition to the single-pulse N(2) Stokes/anti-Stokes ratio temperature measurement technique, a time-averaged temperature measurement technique ispresented that matches the N(2) Stokes Raman spectrum to theoretical spectra by using a single intermediate sta frequency to account for near-resonance enhancement. Raman flame spectra in CH(4)-air flames are presented that have good signal-to-noise characteristics and show promise for single-pulse UV Raman measurements in hydrocarbon flames. PMID:20720783

  11. Percutaneous peripheral excimer laser angioplasty: immediate success rate and short-term outcome

    NASA Astrophysics Data System (ADS)

    Visona, Adriana; Liessi, Guido; Bonanome, Andrea; Lusiani, Luigi; Miserocchi, Luigi; Pagnan, Antonio

    1991-05-01

    Excimer Laser Angioplasty was attempted in 47 patients (36 males, 11 females, mean age 62+/- 7 years, range 39-77 years), affected by peripheral vascular disease. Thirty-seven patients had a total occlusion of the superficial femoral artery, 3 of the iliac artery and 1 of the popliteal artery; 6 patients showed a subocclusive stenosis of the superficial femoral artery. Occlusions and subocclusive stenoses were classified by length: < 10 cm (28 cases), > 10 cm (19 cases). A commercial excimer laser (Technolas Max-10) was used at the Xenon- Chloride wavelength of 308 nm. The laser operated at 60 ns pulse length and at 20-40 Hz repetition rate. Applied energy fluence was 20 mJ/pulse. The energy was delivered through a multifiber catheter, which combines 12 (7F) or 18 (9F) fibers (260 micron diameter each), concentrically arranged. Balloon dilatation was associated to complete the procedure in 38 cases. The treated arteries were successfully recanalized in 41 out of 47 patients (87%). Hemodynamic improvement was confirmed by a significant increase of ankle/brachial systolic pressure index (from 0.60+/- 0.17 to 0.79+/- 0.20, p < 0.005). Failure to recanalize arterial occlusion occurred in 6 cases, and was due to dissection in 3 patients and inability to cross the final segment of a long occlusion in 3 patients. The success rate was higher for lesions < 10 cm in length. Early reocclusion was observed in 7 patients and was associated with poor run-off. The cumulative patency rate at 1 month was 90.7%. Preliminary results are encouraging. More suitable catheters and better selection of patients should improve the efficacy of laser angioplasty and should allow to perform laser procedures without combining balloon angioplasty.

  12. The investigation of selective pre-pattern free self-assembled Ge nano-dot formed by excimer laser annealing

    PubMed Central

    2012-01-01

    Localized Ge nano-dot formation by laser treatment was investigated and discussed in terms of strain distribution. The advantage of this technique is patterning localization of nano-dots without selective epitaxial growth, reducing costs and improving throughput. Self-assembled Ge nano-dots produced by excimer laser annealing statistically distributed dot density and size dependent on laser energy. Improvement in the crystallization quality of the dots was also studied, and a strain analysis was undertaken. PMID:22709630

  13. Application Of The Excimer Laser To Area Recontouring Of The Cornea

    NASA Astrophysics Data System (ADS)

    Yoder, Paul R.; Telfair, William B.; Warner, John W.; Martin, Clifford A.; L'Esperance, Francis A.

    1989-04-01

    Excimer lasers operating at 193 nm are being used experimentally in a special type of materials processing wherein the central portion of the anterior surface of the human cornea is selectively ablated so as to change its refractive power and, hopefully, improve impaired vision. Research to date has demonstrated recontouring as a potential means for reducing myopia and hyperopia of cadaver eyes while studies of ablations on the corneas of living monkeys and of blind human volunteers show promise of prompt and successful healing. The procedure has also shown merit in removing superficial scars from the corneal surface. In this paper, we describe the electro-optical system used to deliver the UV laser beam in these experiments and report some preliminary results of the ablation studies.

  14. Automated generation of NC part programs for excimer laser ablation micromachining from known 3D surfaces

    NASA Astrophysics Data System (ADS)

    Mutapcic, Emir; Iovenitti, Pio G.; Hayes, Jason P.

    2002-11-01

    The purpose of this research project is to improve the capability of the laser micromachinning process, so that any desired 3D surface can be produced by taking the 3D information from a CAD system and automatically generating the NC part programs. In addition, surface quality should be able to be controlled by specifying optimised parameters. This paper presents the algorithms and a software system, which processes 3D geometry in an STL file format from a CAD system and produces the NC part program to mill the surface using the Excimer laser ablation process. Simple structures are used to demonstrate the prototype system's part programming capabilities, and an actual surface is machined.

  15. White-Light Emission from Silicone Rubber Modified by 193 nm ArF Excimer Laser

    NASA Astrophysics Data System (ADS)

    Okoshi, Masayuki; Sekine, Daisuke; Inoue, Narumi; Yamashita, Tsugito

    2007-04-01

    The photochemical surface modification of silicone ([SiO(CH3)2]n) rubber has been successfully demonstrated using a 193 nm ArF excimer laser, and white light of strong intensity was emitted upon exposure to a 325 nm He-Cd laser. The photoluminescence spectra of the modified silicone showed broad peaks centered at 410, 550, and 750 nm wavelengths. The modified surface was carbon-free silicon oxide, and the chemical composition ratio of O/Si was approximately 2. However, the surface was not silica glass (SiO2), as clarified by IR spectroscopy. Instead, nanometer-size particles of silicon oxide were formed on the surface of the modified silicone rubber.

  16. Excimer laser texturing of natural composite polymer surfaces for studying cell-to-substrate specific response

    NASA Astrophysics Data System (ADS)

    Dinca, V.; Alloncle, P.; Delaporte, P.; Ion, V.; Rusen, L.; Filipescu, M.; Mustaciosu, C.; Luculescu, C.; Dinescu, M.

    2015-10-01

    Surface modifications of biocompatible materials are among the main factors used for enhancing and promoting specific cellular activities (e.g. spreading, adhesion, migration, and differentiation) for various types of medical applications such as implants, microfluidic devices, or tissue engineering scaffolds. In this work an excimer laser at 193 nm was used to fabricate chitosan-collagen roughness gradients. The roughness gradients were obtained in one step by applying single laser pulses and sample tilting. Fourier transform infrared spectroscopy measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectro-ellipsometry (SE) were used for sample characterization. The goal is to determine the optimal morpho-chemical characteristics of these structures for in vitro tailoring of protein adsorption and cell behavior. The response induced by the roughness gradient onto various cell lines (i.e. L 929 fibroblasts, HEP G2 hepatocytes, OLN 93 oligodendrocytes, M63 osteoblasts) and bovine serum albumin (BSA) protein absorption was investigated.

  17. Modulation of corneal wound healing after excimer laser keratomileusis using topical mitomycin C and steroids

    SciTech Connect

    Talamo, J.H.; Gollamudi, S.; Green, W.R.; De La Cruz, Z.; Filatov, V.; Stark, W.J. )

    1991-08-01

    A 193-nm excimer laser system was used to create deep stromal ablations in seven New Zealand white rabbits and shallow ablations in three. Eyes were randomized for treatment with topical mitomycin C, steroids, and erythromycin; topical steroids and erythromycin; or topical erythromycin only. All treatment regimens were instituted twice daily for 14 days. All eyes reepithelialized normally within 3 to 5 days. During 10 weeks of follow-up, all eyes developed moderate reticular subepithelial haze without significant differences among treatment groups. Results of light, fluorescence, and electron microscopic examination showed anterior stromal scarring and markedly reduced new subepithelial collagen formation in the group treated with mitomycin C, corticosteroids, and erythromycin. Focal abnormalities of Descemet's membrane and endothelial abnormalities were present in all treatment groups. Combination therapy with topical steroids, mitomycin C, and erythromycin to control the corneal wound healing response after refractive laser surgery appears promising and warrants further study.

  18. Photo-fragmentation of selenium powder by Excimer laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Van Overschelde, O.; Guisbiers, G.

    2015-10-01

    Laser ablation in liquids is especially adapted to produce nanoparticles free of any contamination as suited for biological and medical applications. A KrF Excimer laser delivering an UV light at 248 nm and operating at low fluence (F~0.5 J/cm2) was used to irradiate a micro-sized powder of selenium dispersed into a de-ionized water solution. To avoid any agglomeration of the selenium nanoparticles during the irradiation, surfactants (SDS and CTAB) were added to the solution and their efficiency was compared. The concentration of surfactants had to be chosen around the critical micellar concentration to produce small selenium nanoparticles (<60 nm). Moreover, SDS shows better mono-disperse size distribution compared to CTAB. Finally, photo-fragmentation is found to be more efficient than bulk thermal ablation to produce very small selenium nanoparticles (less than 10 nm).

  19. Blue satellites of absorption spectrum study of sodium based excimer-pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Hu, Shu; Gai, Baodong; Guo, Jingwei; Tan, Yannan; Liu, Jinbo; Li, Hui; Cai, Xianglong; Shi, Zhe; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Sodium based excimer-pump alkali laser (Na-XPAL) is expected to be an efficient method to generate sodium beacon light, but the information about the spectroscopic characters of Na-XPAL remains sparse so far. In this work, we utilized the relative fluorescence intensity to study the absorption spectrum of blue satellites of complexes of sodium with different collision partners. The yellow fluorescence of Na D1 and D2 line was clearly visible. After processing the fluorescence intensity and the input pumping laser relative intensity, we obtained the Na-CH4 system's blue satellites was from 553nm to 556nm. Meanwhile, we experimentally demonstrated the Na-Ar and Na-Xe system's wavelength range of blue satellites. Also, it was observed that the Na-Xe system's absorption was stronger than the other two systems.

  20. Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

    NASA Astrophysics Data System (ADS)

    Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

    2007-09-01

    The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m 2 was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

  1. [Is there a future for the Excimer laser in refractive surgery?].

    PubMed

    Pouliquen, Y; Hanna, K; Waring, G; Savoldelli, M

    1990-02-01

    The refractive surgery concerns all the surgical procedures implicated in the refractive power change of the cornea. Its clinical results are just known, and a new physical procedure is becoming capable to replace surgery: the Excimer laser. Without any instrumental contact with the corneal surface, the laser beam is able to remodel the corneal tissue, and to treat astigmatism, myopia, hypermetropia. Millions of people could be treated by such a laser, and could leave their glasses. Biological effects on rabbit and monkeys are presented. An argon fluoride excimer laser (193 nm) with a moving slit delivery system was used to perform anterior myopic keratomileusis in both eyes of 37 rabbits and 15 monkeys. Histological analysis of the corneas was made after ablation and at intervals up to 20 months. By slit examination at the longer follow up time, 60% of treated rabbits and 40% of treated monkeys keep a clear cornea, but the others had central spotty subepithelial haze. Light and electron microscopy documented corneal healing. In the clear corneas a good reconstitution of the epithelium, its basal lamina was observed, and anterior stromal corneas contained few active fibrocytes with a good preservation of the connective lamellar structure. On the contrary, in the cornea with opacification focal areas of 20 microns thick subepithelial scarring were present and the interface between epithelial cells and anterior stroma remained disturbed by incomplete, disrupted or duplicated basal lamina. Differences between the responses of monkeys, rabbits corneas to the same photoablation procedure remain unclear.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2115392

  2. Update on laser vision correction using wavefront analysis with the CustomCornea system and LADARVision 193-nm excimer laser

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; McDonald, Marguerite B.; Pettit, George H.; Papaioannou, Thanassis; Grundfest, Warren S.

    2002-06-01

    A study was undertaken to assess whether results of laser vision correction with the LADARVISION 193-nm excimer laser (Alcon-Autonomous technologies) can be improved with the use of wavefront analysis generated by a proprietary system including a Hartman-Schack sensor and expressed using Zernicke polynomials. A total of 82 eyes underwent LASIK in several centers with an improved algorithm, using the CustomCornea system. A subgroup of 48 eyes of 24 patients was randomized so that one eye undergoes conventional treatment and one eye undergoes treatment based on wavefront analysis. Treatment parameters were equal for each type of refractive error. 83% of all eyes had uncorrected vision of 20/20 or better and 95% were 20/25 or better. In all groups, uncorrected visual acuities did not improve significantly in eyes treated with wavefront analysis compared to conventional treatments. Higher order aberrations were consistently better corrected in eyes undergoing treatment based on wavefront analysis for LASIK at 6 months postop. In addition, the number of eyes with reduced RMS was significantly higher in the subset of eyes treated with a wavefront algorithm (38% vs. 5%). Wavefront technology may improve the outcomes of laser vision correction with the LADARVISION excimer laser. Further refinements of the technology and clinical trials will contribute to this goal.

  3. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing.

    PubMed

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-24

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm(-2), the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm(-1) at 300.7 cm(-1), which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities. PMID:25815515

  4. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-01

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm-2, the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm-1 at 300.7 cm-1, which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities.

  5. Glare sensitivity and visual acuity after excimer laser photorefractive keratectomy for myopia

    PubMed Central

    Niesen, U.; Businger, U.; Hartmann, P.; Senn, P.; Schipper, I.

    1997-01-01

    BACKGROUND—Following excimer laser photorefractive keratectomy (PRK), an increase in glare sensitivity and a reduction in contrast sensitivity can occur owing to changes in the cornea (structure and topography). In this study, an attempt was made to quantify and document objectively a change in those subjective perceptual factors.
METHODS—Snellen visual acuity and disability glare were measured with the Berkeley glare test preoperatively as well as 1, 3, 6, 9, and 12 months postoperatively, after excimer laser photorefractive keratectomy (PRK) on 32 myopic patients (46 eyes). During the postoperative progress checks, haze was graded and contrast sensitivity was measured with the Vistech chart. All the data were statistically analysed by multiple regression.
RESULTS—One year after PRK, a reduction in visual acuity (VA) measured with the low acuity contrast chart (10%) with and without glare could still be found, despite the fact that acuity measurements with a high contrast Snellen chart showed the same VA 6 months postoperatively as well as before the treatment. The lowest VA could be measured 1 month postoperatively; thereafter, the acuity increased despite the increase in haze that occurred during the first 3 months.
CONCLUSION—Disability glare and a reduction in contrast sensitivity could be observed in most patients after PRK treatment with the Meditec laser system with its scanning slit. The future will show if new technology and a broader flattening area of 6 to 7 mm can minimise these postoperative complications.

 PMID:9059248

  6. Self-control study of combination treatment of 308 nm excimer laser and calcipotriene ointment on stable psoriasis vulgaris

    PubMed Central

    Tang, Ya-Juan; Xu, Wan-Wen; Liu, Xiao-Ming; Zhang, Ru-Zhi; Xu, Chun-Xing; Xu, Bin; Cheng, Sai; Liu, Qi

    2014-01-01

    Objective: This study aims to compare the differences of clinical efficacy and safety of treatment of stable psoriasis vulgaris with calcipotriene ointment in combination with 308 nm excimer laser to 308 nm excimer laser alone. Methods: Randomized, open and self-control trial was conducted in 36 selected patients. The skin lesions from these patients with stable psoriasis vulgaris were divided into two sides along the midline of torso, one side was treated with 308 nm excimer laser, 2 times/week, at meantime Calcipotriene was applied externally, 2 times/day (treatment group); the other side was given 308 nm excimer laser alone, 2 times/week, the treatment period was 6 weeks (control group). Skin lesion area, PASI scores and cumulative doses of 308 nm excimer laser in patients with psoriasis were assessed before treatment and on weeks 2, 4 and 6 after treatment. Results: 32 of 36 patients with stable psoriasis vulgaris completed study, effective rates in two groups were better on week 6 (84.37%, 56.25%) than on week 4 (53.12%, 37.5%) and on week 2 (31.25%, 18.75%) (P < 0.05). Effective rate on week 6 in control group (56.25%) was lower than treatment group (84.37%) (P < 0.05). The two groups showed that PASI scores on weeks 2 and 4 after treatment were significantly lower than before treatments (P < 0.05), and PASI scores on week 6 in treatment group was significantly lower than control group (P < 0.05). The average cumulative laser doses in treatment group at the end of trial was 4.69 (2.03) J/cm2, which was significantly lower than in control group 8.41 (2.42) J/cm (P < 0.05). Treatment efficacies in the head, folds, back, abdomen and limbs were similar and no serious adverse effects, however the number of treatment and irradiation doses in the head and folds were significantly less than in back, abdomen and limbs (P < 0.05). Conclusions: Treatment of psoriasis vulgaris with 308 nm excimer laser in combination with external application of Calcipotriene ointment

  7. High-performance thin-film transistors fabricated using excimer laser processing and grain engineering

    SciTech Connect

    Giust, G.K.; Sigmon, T.W.

    1998-04-01

    High-performance polysilicon thin-film transistors (TFT`s) are fabricated using an excimer laser to recrystallize the undoped channel and dope the source-drain regions. Using a technique the authors call grain engineering they are able to control grain microstructure using laser parameters. Resulting polysilicon films are obtained with average grain sizes of {approximately}4--9 {micro}m in sub-100 nm thick polysilicon films without substrate heating during the laser recrystallization process. Using a simple four-mask self-aligned aluminum top-gate structure, they fabricate TFT`s in these films. By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFT`s are fabricated with electron mobilities up to 260 cm{sup 2}/Vs and on/off current ratios greater than 10{sup 7} To their knowledge, these devices represent the highest performance laser-processed TFT`s reported to date fabricated without substrate heating or hydrogenation.

  8. Excimer laser crystallization of amorphous silicon carbide produced by ion implantation

    NASA Astrophysics Data System (ADS)

    Hedler, A.; Urban, S.; Falk, F.; Hobert, H.; Wesch, W.

    2003-01-01

    4H-SiC was implanted with 100-250 keV Ge + and Xe + ions and doses of 1×10 14 to 1×10 16 cm -2 at room temperature in order to produce 40-200 nm thick amorphous surface layers. The samples were irradiated with 1-50,000 pulses of a KrF excimer laser (248 nm wavelength, 30 ns pulse duration) using fluences of 150-900 mJ/cm 2 to investigate the crystallization process as a function of the laser parameters. Crystallization as well as redistribution of the impurity atoms were analyzed by Rutherford backscattering spectrometry and infrared reflection measurements. Phase transitions occurring during the irradiation were studied by means of time-resolved reflectivity measurements. In order to explain the observed phase transitions numerical analysis was performed by solving the inhomogeneous heat flow equation using the parameters of the corresponding phases. In this work, we give a consistent description of the experimental results by the numerical simulations for the given laser setup. Depending on the amorphous layer thickness, melting, solidification, and crystallization of the amorphous phase can be effectively controlled by both the laser fluence and the number of laser pulses.

  9. Irradiation planning for automated treatment of psoriasis with a high-power excimer laser

    NASA Astrophysics Data System (ADS)

    Klämpfl, Florian; Schmidt, Michael; Hagenah, Hinnerk; Görtler, Andreas; Wolfsgruber, Frank; Lampalzer, Ralf; Kaudewitz, Peter

    2006-02-01

    American and European statistics have shown that 1-2 per cent of the human population is affected by the skin disease psoriasis. Recent research reports promising treatment results when irradiating skin areas affected by psoriasis with high powered excimer lasers with a wavelength of 308 nm. In order to apply the necessary high energy dose without hurting healthy parts of the skin new approaches regarding the system technology must be considered. The aim of the current research project is the development of a sensor-based, automated laser treatment system for psoriasis. In this paper we present the algorithms used to cope with the diffculties of irradiating irregularly shaped areas on curved surfaces with a predefined energy level using a pulsed laser. Patients prefer the treatment to take as little time as possible. This also helps to reduce costs. Thus the distribution of laser pulses on the surface to achieve the given energy level on every point of the surface has to be calculated within a limited time frame. The remainder of the paper will describe in detail an efficient method to plan and optimize the laser pulse distribution. Towards the end, some first results will be presented.

  10. Effect of ambient environment on excimer laser induced micro and nano-structuring of stainless steel

    NASA Astrophysics Data System (ADS)

    Umm-i-Kalsoom; Bashir, Shazia; Ali, Nisar; Akram, Mahreen; Mahmood, Khaliq; Ahmad, Riaz

    2012-11-01

    The effect of laser fluence and an ambient environment on the formation and development of the micro and nano-structures on the laser irradiated stainless steel (AISI-304) targets have been investigated. For this purpose KrF excimer laser (λ = 248 nm, t = 20 ns, repetition rate 20 Hz) has been used. The targets are exposed for various laser fluences ranging from 0.72 J cm-2 to 1.27 J cm-2 under the vacuum condition and in the oxygen environment at a pressure of 133 mbar. Various features of treated targets, such as surface morphology, chemical composition and crystalline structure are analyzed by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction techniques, respectively. Scanning electron microscope analysis reveals the formation of laser-induced periodic surface structures (LIPSS), cavities, hillocks in both ambient environments (vacuum, oxygen). Cone-formation on the top of wave like ridges is observed under vacuum condition. In case of oxygen only redeposition is observed. Energy dispersive X-ray spectroscopy analysis exhibits that there is variation in chemical composition in both environments. When the target is treated in oxygen environment enhancement of the surface oxygen content is observed. X-ray diffraction exhibits that no new phases are formed under vacuum condition but a phase change in oxygen ambient is observed. For various fluences the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

  11. Photon-controlled fabrication of amorphous superlattice structures using ArF (193 nm) excimer laser photolysis

    SciTech Connect

    Lowndes, D.H.; Geohegan, D.B.; Eres, D.; Pennycook, S.J.; Mashburn, D.N.; Jellison G.E. Jr.

    1988-05-30

    Pulsed ArF (193 nm) excimer laser photolysis of disilane, germane, and disilane-ammonia mixtures has been used to deposit amorphous superlattices containing silicon, germanium, and silicon nitride layers. Transmission electron microscope cross-section views demonstrate that structures having thin (5--25 nm) layers and sharp interlayer boundaries can be deposited at substrate temperatures below the pyrolytic threshold, entirely under laser photolytic control.

  12. Interaction of 308-nm excimer laser light with temporomandibular joint related structures

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim; Funk, Armin

    1994-02-01

    Arthroscopy of TMJ has become a clinically important and more and more accepted method for diagnosis and treatment of TMJ alteration. This minimal invasive method is clearly limited by the anatomical dimensions of the TMJ. A 308 nm excimer laserlight has already found clinical applications in angioplasty, ophthalmology, and dentistry. The aim of the presented study was to find out if it is possible to ablate TMJ related structures under arthroscopic conditions. It also aims to evaluate the energy-threshold for ablation and the maximal possible rate of ablation. Contrary to other laser systems it offers a unique combination of minimal tissue alteration, precise tissue ablation guidability through optical fibers, and a good transmission through water.

  13. Studies of Preionization Processes of High Pressure Gases for Excimer Laser Discharges

    NASA Astrophysics Data System (ADS)

    Kataoka, N.; Uchino, K.; Muraoka, K.; Okada, T.; Maeda, M.; Sunaka, E.; Enami, T.; Mizoguchi, H.

    1998-10-01

    The aim of this research is to understand and control the preionization process in high pressure discharges used for excimer lasers. For this purpose, a test chamber with a spark light source was designed and fabricated, to achieve ultra high vacuum and to control the base pressure. Photocharge signals produced by the spark light source were collected by pairs of plate electrodes placed inside the test chamber. In order to study the effect of gaseous impurities on the preionization process, measurements were performed for different base pressure conditions. The results showed that the photocharge signal was linearly correlated with the base pressure. Also, the possibility of actively controlling the preionization by adding small amount of Xe gas to the gas mixture was examined. The maximum signal at the Xe partial pressure of 0.1 Torr was 10 times higher than the signal for the Ne and Kr mixture without Xe, suggesting that active control may be possible.

  14. Microlens Array Fabricated by Excimer Laser Micromachining with Gray-tone Photolithography

    NASA Astrophysics Data System (ADS)

    Tien, Chung-Hao; Chien, Yeh-En; Chiu, Yi; Shieh, Han-Ping D.

    2003-03-01

    We demonstrate the fabrication of a refractive microlens array by using 248 nm excimer laser micromachining with coded gray-tone mask photolithography. With pre-corrections to the nonlinear exposure process, the maximum deviation from the designed shape was below 5%. The fabricated hemispherical lens of 30 μm radius was used as a solid immersion lens (SIL) and combined with a 0.54 numerical aperture (NA) objective to achieve a 0.87 effective NA through the knife-edge scanning test. The experimental results agreed with those of the simulation. Unlike the methods such as the thermal melting process, this one-step optical exposure method with a coded mask provides a relatively fast and cost-effective way to realize a microlens array in optical data storage, information processing, and optical interconnection applications.

  15. An electrically triggered 200 kV rail-gap switch for wide aperture excimer lasers

    NASA Astrophysics Data System (ADS)

    Endoh, A.; Watanabe, S.; Watanabe, M.

    1984-03-01

    A wide aperture (7 x 7 sq cm), high output energy (5 J in KrF and 13.8 J in XeCl), UV preionized excimer laser is described. A self-breakdown rail gap was employed as an output switch with the maximum voltage and current up to 230 kV and 300 kA, respectively. To solve the switching jitter problem associated with the self-breakdown, an electrical triggering was investigated. The measured minimum switching time delay and gap closing time were 40 and 10 ns, respectively. The number of channels up to 50 was observed with a uniform distribution over the 80-cm electrode length. The triggering jitter was measured to be less than a nanosecond. The maximum operation voltage of the triggered rail gap was 200 kV. The successful trigger operation was obtained in the range 30-98 percent of the self-breakdown voltage.

  16. The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-11-07

    We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of {approx}4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.

  17. Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

    NASA Astrophysics Data System (ADS)

    Mosquera, Samuel Arba; Verma, Shwetabh

    2015-07-01

    The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r2=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r2=0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

  18. Excimer versus Femtosecond Laser Assisted Penetrating Keratoplasty in Keratoconus and Fuchs Dystrophy: Intraoperative Pitfalls

    PubMed Central

    El-Husseiny, Moatasem; Seitz, Berthold; Langenbucher, Achim; Akhmedova, Elena; Szentmary, Nora; Hager, Tobias; Tsintarakis, Themistoklis; Janunts, Edgar

    2015-01-01

    Purpose. To assess the intraoperative results comparing two non-mechanical laser assisted penetrating keratoplasty approaches in keratoconus and Fuchs dystrophy. Patients and Methods. 68 patients (age 18 to 87 years) with keratoconus or Fuchs dystrophy were randomly distributed to 4 groups. 35 eyes with keratoconus and 33 eyes with Fuchs dystrophy were treated with either excimer laser ([Exc] groups I and II) or femtosecond laser-assisted ([FLAK] groups III and IV) penetrating keratoplasty. Main intraoperative outcome measures included intraoperative decentration, need for additional interrupted sutures, alignment of orientation markers, and intraocular positive pressure (vis a tergo). Results. Intraoperative recipient decentration occurred in 4 eyes of groups III/IV but in none of groups I/II. Additional interrupted sutures were not necessary in groups I/II but in 5 eyes of groups III/IV. Orientation markers were all aligned in groups I/II but were partly misaligned in 8 eyes of groups III/IV. Intraocular positive pressure grade was recognized in 12 eyes of groups I/II and in 19 eyes of groups III/IV. In particular, in group III, severe vis a tergo occurred in 8 eyes. Conclusions. Intraoperative decentration, misalignment of the donor in the recipient bed, and need for additional interrupted sutures as well as high percentage of severe intraocular positive pressure were predominantly present in the femtosecond laser in keratoconus eyes. PMID:26483974

  19. Experimental investigation of fabrication process-, transportation-, storage, and handling-induced contamination of 157-nm reticles and vacuum UV cleaning

    NASA Astrophysics Data System (ADS)

    Okoroanyanwu, Uzodinma; Stepanenko, Nickolay; Vereecke, Guy; Eliat, Astrid; Kocsis, Michael K.; Kang, Young-Seog; Jonckheere, Rik M.; Conard, Thierry; Ronse, Kurt G.

    2004-05-01

    Mask fabrication process, transportation, storage, and handling contribute to contamination of 157nm reticles and modified fused silica substrates, resulting in transmission loss. A stable VUV cleaning procedure for contaminated binary, alternating, and attenuated phase shift reticles has been developed. This cleaning procedure was verified by lithographic imaging on the 157nm ASML MS-VII exposure scanner. A point-to-point steady state dose transmission uniformity range across a batch of 25 wafers (the exposure conditions of which were equivalent to that of a 300 mm wafer, 26mm×33mm fields, 50mJ/cm2) that were exposed with a modified fused silica substrate, was found to be <0.24% for a reticle that was cleaned prior to exposure using this VUV cleaning process. In-situ laser cleaning of contaminated mask substrates during exposure in the MS-VII resulted in 1% change in transmission at doses of up to 20 J/cm2, above which transmission remains stable (<0.24% variation). The cleaning procedure involves exposing the contaminated reticle in the UVO Reticle Cleaning Station for 30 minutes, using a cleaning gas mixture of N2/O2=99%/1%. Transmission loss due to contamination within the clean room is limited to 1 - 2 % and is reversible upon VUV cleaning. Flare levels of 3% were measured on contaminated reticle relative to a clean state of the same reticle. VUV cleaning is not only good for improving and maintaining stable mask transmission, but it is also good for preventing reticle contamination-induced flare. Contamination rate and contaminant type appear to be dependent on the storage environment of mask substrates and reticles. Typical contaminants included molecular acids (halogens, sulfur, sulfates), molecular bases (ammonia, amines), molecular condensables (hydrocarbons, alcohols, ketones, fatty acids, siloxanes, phthalate), molecular dopant (boron) and molecular metals (Ca, Mg, Al, Cu). Contamination of mask substrates appears to be through a competitive adsorption

  20. [Analysis of images in the prophylaxis and treatment of complications after kerato-refractive excimer laser surgeries].

    PubMed

    Makarov, I A

    2003-01-01

    A total of 236 eyes of patients with myopia and hypermetropia of different severity degrees after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) were observed. The densitometry and planimetry analysis of corneal images, obtained through storing them in the computer memory, was used to evaluate postoperatively the corneal condition. Planimetry was used to forecast the time of epithelization and to assess the efficiency of drug therapy. The optic density was found to increase, after excimer-laser surgeries, in all patients and it depended on a type of refraction and its degree. The optic-density dynamics of corneal images also depended on a degree and type of refraction as well as on a type of drug therapy. Hence, densitometry and planimetry, as objective methods used to follow up the patients after keratorefractive excimer-laser surgeries, make it possible to diagnose early enough the presence of complications related with disorders in transparency and healing of the cornea. PMID:12698885

  1. Enhanced efficiency of the dye-sensitized solar cells by excimer laser irradiated carbon nanotube network counter electrode

    SciTech Connect

    Chien, Yun-San Fu, Wei-En; Yang, Po-Yu; Lee, I-Che; Chu, Chih-Chieh; Chou, Chia-Hsin; Cheng, Huang-Chung

    2014-02-03

    The carbon nanotube network decorated with Pt nanoparticles (PtCNT) irradiated by excimer laser as counter electrode (CE) of dye-sensitized solar cells (DSSCs) has been systematically demonstrated. The conversion efficiency would be improved from 7.12% to 9.28% with respect to conventional Pt-film one. It was attributed to the enhanced catalytic surface from Pt nanoparticles and the improved conductivity due to the adjoining phenomenon of PtCNTs irradiated by laser. Moreover, the laser annealing could also promote the interface contact between CE and conductive glass. Therefore, such a simple laser-irradiated PtCNT network is promising for the future flexible DSSCs applications.

  2. Focused excimer laser initiated and radio frequency sustained plasma formation in high pressure air

    NASA Astrophysics Data System (ADS)

    Giar, Ryan

    A doctoral thesis project was performed to experimentally investigate the feasibility of focused excimer laser initiation of air plasmas for radio frequency sustainment. A 193 nm, 15 MW, 300 mJ laser was focused with a 18 cm focal length lens to form a small, high density (ne ~ 10 14 cm--3) seed plasma. These laser plasmas were produced inside a borosilicate glass tube around which was wrapped a 5 turn helical antenna. This antenna was powered with 5 kW of 13.56 MHz of radiation for 1.5 s. This was accomplished at a pressure of 22 Torr, resulting in a large volume (300 cm3) air plasma. Diagnostic measurements of this air plasma determined an electron density of 5E10 cm-3 and an electron temperature 1.3 eV with a neutral temperature of 3500 K. The collision frequency was measured to be 9E10 Hz which resulted in a plasma-loaded antenna resistance of 6 O with a voltage reflection coefficient of 0.7.

  3. The Role of Crystalline Water in the Interaction of Excimer Laser Light with Brushite

    NASA Astrophysics Data System (ADS)

    Dawes, M. L.; Langford, S. C.; Dickinson, J. T.

    1998-03-01

    A number of minerals of environmental interest contain waters of hydration, sometimes called crystalline water. Hydrated crystals often show dramatic changes in optical properties as well as mechanical properties, both influencing the response of the material to radiation. From an analytic point of view, very little is known about the influence of hydration regarding laser desorption and ablation phenomena. We explore the interaction of excimer laser light (KrF 248 nm) with single crystal brushite (CaHPO_4.2H_2O), a model biomineral phosphate containing H_2O. We first show that defects dominate the interactions as revealed by high sensitivity detection of Ca^+ at low fluences and that this ion emission predicts ablation thresholds. The most probable ion energy, which occurs at 11 eV, is much higher than the incident photon energy of 5 eV. The ion intensities also display a highly nonlinear fluence dependence, typically 6-8th order, entirely consistent with ion emission models we have recently presented. We show that laser coupling can be enhanced several orders of magnitude by generation of defects, i.e., by mechanical treatment, heating, or exposure to electron beams and that the consequences of crystalline H_2O and HPO_4^2- decomposition play major and related roles in this defect production.

  4. Glass etching initiated by excimer laser photolysis of CF/sub 2/Br/sub 2/

    SciTech Connect

    Brannon, J.H.

    1986-04-24

    KrF and ArF excimer laser irradiation of glass surfaces immersed in gaseous CF/sub 2/Br/sub 2/ is found to induce etching. The etch mechanism is considered to be nonthermal on the basis of the small value of the glass absorption coefficent and wavelength variable etching experiments. The etch rate dependence on surface fluence is presented for three pressures. SEM photos reveal a rough surface morphology in the etched region that apparently is not a chemical effect but results solely from the laser irradiation. Photochemical and spectroscopic analysis of the irradiated gas provides evidence for CF/sub 2/ and CF/sub 2/Br as being major photolysis products. C/sub 2/F/sub 4/ was also found to cause etching at 248 and 193 nm. This is evidence that CF/sub 2/, resulting from C/sub 2/F/sub 4/ photolysis, is alone capable of initiating glass etching in the presence of laser light. The paper concludes by discussing the observed inability of the CF/sub 3/ releasing parent gases CF/sub 3/Br and CF/sub 3/I to significantly etch glass when irradiated in their appropriate absorption bands. 31 references, 9 figures, 1 table.

  5. High Spatial Resolution Analysis of Carbonates by In Situ Excimer Laser Ablation MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Shuttleworth, S.; Lloyd, N.; Douthitt, C.

    2012-12-01

    Speleothems are important climate archives. The time resolution of the paleochlimate proxies depends on the growth rates and the precision limitation of the analytical instrumentation [1]. As a consequence, for speleothems, better analytical precision combined with better spatial resolution will always be the goal, driven by a need to probe the timing and duration of climate events [1]. The Thermo Scientific NEPTUNE Plus with Jet Interface option offers unparalleled MC-ICP-MS sensitivity for heavy elements. An ion yield of >3 % has previously been reported for uranium solutions introduced by desolvating nebulizer[2]. For laser ablation Hf, the Jet Interface with N2 addition significantly improved sensitivity, which allowed precise and accurate 176Hf/177Hf ratios to be calculated using a spot size of just 25 μm diameter [3]. A Thermo Scientific NEPTUNE Plus with Jet Interface option was coupled with a Photon Machines excimer laser ablation system. This system features a short pulse width (4ns) 193 nm excimer laser and the HELEX 2 volume sample cell. The 193nm wavelength has been shown to reduce the particle size distribution of the aerosol produced by the laser ablation process [4] and this in turn has been shown to help minimize the effects of fractionation by ensuring that particles are in a size range so as to avoid incomplete vaporization and ionization in the plasma [5]. In this work we investigate U-Th dating of carbonates. Accurate LA U-Th isotope measurements on carbonates with U concentrations smaller than 1 μg/g are difficult due to small ion beams [1]. Hoffman et. al. [1] noted individual LA U-Th ratio precisions of about 2% (2 sigma) on a 134 ka sample with 134 μg/g U concentration. In this work we apply a combination of the high sampling efficiency two volume cell plus mixed gas plasmas to further enhance the capability. [1] Hoffman, D.L., et al. (2009). Chemical Geology. 259 253-261 [2] Bouman, C., et al. (2009). Geochim. Cosmochim. Acta. 73

  6. UV excimer laser and low temperature plasma treatments of polyamide materials

    NASA Astrophysics Data System (ADS)

    Yip, Yiu Wan Joanne

    Polyamides have found widespread application in various industrial sectors, for example, they are used in apparel, home furnishings and similar uses. However, the requirements for high quality performance products are continually increasing and these promote a variety of surface treatments for polymer modification. UV excimer laser and low temperature plasma treatments are ideally suited for polyamide modification because they can change the physical and chemical properties of the material without affecting its bulk features. This project aimed to study the modification of polyamides by UV excimer laser irradiation and low temperature plasma treatment. The morphological changes in the resulting samples were analysed by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (TM-AFM). The chemical modifications were studied by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and chemical force microscopy (CFM). Change in degree of crystallinity was examined by differential scanning calorimetry (DSC). After high-fluence laser irradiation, topographical results showed that ripples of micrometer size form on the fibre surface. By contrast, sub-micrometer size structures form on the polyamide surface when the applied laser energy is well below its ablation threshold. After high-fluence laser irradiation, chemical studies showed that the surface oxygen content of polyamide is reduced. A reverse result is obtained with low-fluence treatment. The DSC result showed no significant change in degree of crystallinity in either high-fluence or low-fluence treated samples. The same modifications in polyamide surfaces were studied after low temperature plasma treatment with oxygen, argon or tetrafluoromethane gas. The most significant result was that the surface oxygen content of polyamide increased after oxygen and argon plasma treatments. Both treatments induced many hydroxyl (-OH) and carboxylic acid (-COOH

  7. Factors Affecting the Production of Aromatic Immonium Ions in MALDI 157 nm Photodissociation Studies

    NASA Astrophysics Data System (ADS)

    DeGraan-Weber, Nick; Ashley, Daniel C.; Keijzer, Karlijn; Baik, Mu-Hyun; Reilly, James P.

    2016-05-01

    Immonium ions are commonly observed in the high energy fragmentation of peptide ions. In a MALDI-TOF/TOF mass spectrometer, singly charged peptides photofragmented with 157 nm VUV light yield a copious abundance of immonium ions, especially those from aromatic residues. However, their intensities may vary from one peptide to another. In this work, the effect of varying amino acid position, peptide length, and peptide composition on immonium ion yield is investigated. Internal immonium ions are found to have the strongest intensity, whereas immonium ions arising from C-terminal residues are the weakest. Peptide length and competition among residues also strongly influence the immonium ion production. Quantum calculations provide insights about immonium ion structures and the fragment ion conformations that promote or inhibit immonium ion formation.

  8. The effect on the ultrastructure of dental enamel of excimer-dye, argon-ion and CO2 lasers.

    PubMed

    Palamara, J; Phakey, P P; Orams, H J; Rachinger, W A

    1992-12-01

    This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise. PMID:1295076

  9. The Effect of Excimer Laser Treatment on the Surface Roughness and Fracture Strength of Alumina Substrates

    SciTech Connect

    Smoot, J.E.

    1998-05-13

    The microelectronics industry requires alumina substrates with exceptionally smooth surfaces and few surface defects to allow successful deposition of metallic films for reliable electronic performance. Irradiation by a 248-nm wavelength excimer laser beam (KrF) at a fluence of 125 mJ/mm{sup 2} and at various angles of incidence is shown to significantly reduce the surface roughness of alumina substrates. However, irradiation also creates a fine particulate deposit of alumina that only partially adheres to the substrate and impedes deposition of metal films. Annealing in air between 1350 C and 1450 C was found to remove the particles by sintering. As-received material showed surface roughness average (R{sub a}) mean values of 457 nm, which was reduced to 60 nm (mean) following irradiation and 71 nm (mean) following irradiation and annealing at 1350 C. Irradiation also produced a decrease in the number and severity of surface defects. The flexural strength and Weibull modulus were both increased by laser irradiation and thermal treatment. Flexural strength went from an as-received value of 450 MPa to 560 MPa following irradiation/sintering, measured at 10% probability of failure. The Weibull modulus was increased from the as-received value of about 9, to about 13 following irradiation/sintering. It was concluded that irradiation at an angle of incidence of 60{degree} from perpendicular was most effective in producing a low surface roughness.

  10. Surface properties modifications obtained on ceramics and metals resulting from excimer laser processing technique

    NASA Astrophysics Data System (ADS)

    Nicolas, Gines; Autric, Michel L.; Ocana, Jose L.

    1998-09-01

    The unique properties of a UV laser beam (high energy, short pulse duration) allow to transform the surface of ultrahard materials such as ceramics. In this way, a KrF excimer laser was used in this study in order to modify in selected zones, the surface of metals (aluminum alloy, titanium alloy and stainless steel) and oxides (Al2O3, ZrO2), carbide (SiC) and nitride (AlN). These ceramics possess good mechanical and thermal properties but exhibit a brittle behavior due to the granular structure. In a suitable range where the irradiated zone is melted and defects are removed, initial properties are modified (roughness, porosity, hardness, chemical composition). A cleaned and smoothed surface can be obtained without pores and cracks. These sites where corrosion attack starts are minimized and can lead to improve functions in potential industrial applications. The results presented in this work have been obtained by different analysis techniques such as scanning electron microscopy (SEM) to examine morphology, Auger spectroscopy (AES) to give chemical composition and depths profiles, mechanical tests to show roughness and hardness, grazing X-ray diffraction (XRD) to find structure.