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Sample records for power excimer laser

  1. 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.

  2. 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.

  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. Eurolaser. High power excimer laser: Optical crystals

    NASA Astrophysics Data System (ADS)

    Gaenswein, Bernhard

    1987-09-01

    The crystals used in excimer lasers because of their excellent optical properties in the ultra violet spectrum are described. The crystals are fluorides of the alkaline earth metals magnesium, calcium and barium and the alkaline fluorides of lithium and sodium. It is possible to grow optical monocrystals of these compounds up to weights of 15 kg with a diameter of 180 mm. Some problems develop in growing crystals larger than this. To do so greater plants and improved automatic temperature monitoring and regulation are required. Special tools are needed for handling such large and heavy monocrystals. Understanding of the interaction between laser radiation and crystal must be improved upon in order to meet all the requirements to be placed on optical components in the future.

  5. 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.

  6. 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.

  7. Development of over 300-watts average power excimer laser

    NASA Astrophysics Data System (ADS)

    Hirata, Kazuhiro; Kawamura, Joichi; Katou, Hiroyuki; Sajiki, Kazuaki; Okada, Makoto

    2004-05-01

    The high power excimer laser was developed. We have supplied the 240 watts (800 mJ, 300 Hz) average power excimer laser for industrial use, mainly for TFT LCD annealing. We are going to add the 300 watts (1 J, 300 Hz) average power laser for our line-up. This 300 watts new laser is based on the 240 watts laser, but improved some points. The electrodes size is longer and the electrical power circuit is reinforcement. Laser gas recipe is changed to be good for new system. In our test, we could oscillate over 300 watts average power operation. 310 watts servo operation is able to oscillate over 40 million pulses with less than 1.0 per cent for σ output stability. 330 watts servo operation is able to oscillate over 30 million pulses with almost less than 1.0 per cent for σ output stability. Experimental and theoretical studies of various parameters influencing the laser performance will be continued with further investigations and future improvements. We have confidence that it will be possible for this laser to produce higher power with long gas life.

  8. The Development Of Industrial Excimer Lasers

    NASA Astrophysics Data System (ADS)

    Levatter, Jeffrey I.

    1986-11-01

    The first discharge pumped excimer lasers introduced in the 1970's were derivatives of N2 and C02 TEA lasers. They had spatially non-uniform outputs, relatively small output energies, low average powers, short operating lifetimes, and poor reliability. Today, more than a decade later, excimer lasers are just now maturing to the point where they are starting to enter the industrial workplace. This paper will review the transition from CO2/N2 to excimer technology, the engineering hurdles excimer lasers must overcome to make them viable industrial tools, and the current state of the "industrial excimer laser".

  9. 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.

  10. Endoscopic excimer laser surgery

    NASA Astrophysics Data System (ADS)

    Salimbeni, Renzo; Pini, Roberto; Vannini, Matteo; Benaim, George; Mattioli, Stefano

    1994-02-01

    Long pulse excimer laser radiation can be efficiently coupled and transmitted through optical fibers allowing the achievement of both photoablative and photomechanical effects. In this work the investigation has been focussed on the urologic surgery field to demonstrate the effectiveness of an excimer laser system for very different therapeutic tasks: recanalization of urethral stenosis and lithotripsy. The choice of the suitable radiation dosimetry and the technical solutions employed provide to the surgeon a multipurpose laser system with a wide range of utility in comparison with other laser systems.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Progress of excimer laser technologies

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Hakaru

    2000-10-01

    More than 1,000 units of KrF excimer laser steppers were already installed in semiconductor mass-production lines which require design rule of less than 0.15 m. Higher NA lens compatibility, productivity and CoO become critical issues of KrF excimer laser stepper. Advanced 2kHz KrF excimer laser G20K/G21K offers the solutions for these three issues. Next generation excimer laser ArF has already finished the stage of principle demonstration and has moved to a next level of practical demonstration and has moved to next level of practical inspection, such as stability, productivity, and economic efficiency. Gigaphoton 4kHz ArF, G40A, solved all of these issues. Furthermore sub 0.10m design rule region F2 laser has been examined at several organizations. In March, 2000, Komatsu successfully developed 2kHzF2 laser for catadioptric projection optics by the fund of NEDO. Gigaphoton is ready to fabricate G20F, 2kHz F2 laser, based upon the result of NEDO research. ASET started new F2 laser lithography development program at Hiratsuka Research Center with collaboration of Nikon, Canon, Gigaphoton, Komatsu, and Ushio from April 2000, ending March 2002.

  16. Design concept and performance considerations for fast high power semiconductor switching for high repetition rate and high power excimer laser

    NASA Astrophysics Data System (ADS)

    Goto, Tatsumi; Kakizaki, Kouji; Takagi, Shigeyuki; Satoh, Saburoh; Shinohe, Takashi; Ohashi, Hiromichi; Endo, Fumihiko; Okamura, Katsuya; Ishii, Akira; Teranishi, Tsuneharu; Yasuoka, Koichi

    1997-07-01

    A semiconductor switching power supply has been developed, in which a novel structure semiconductor device, metal-oxide-semiconductor assisted gate-triggered thyristor (MAGT) was incorporated with a single stage magnetic pulse compression circuit (MPC). The MAGT was specially designed to directly replace thyratrons in a power supply for a high repetition rate laser. Compared with conventional high power semiconductor switching devices, it was designed to enable a fast switching, retaining a high blocking voltage and to extremely reduce the transient turn-on power losses, enduring a higher peak current. A maximum peak current density of 32 kA/cm2 and a current density risetime rate di/dt of 142 kA/(cm2×μs) were obtained at the chip area with an applied anode voltage of 1.5 kV. A MAGT switching unit connecting 32 MAGTs in series was capable of switching on more than 25 kV-300 A at a repetition rate of 5 kHz, which, coupled with the MPC, was equivalent to the capability of a high power thyratron. A high repetition rate and high power XeCl excimer laser was excited by the power supply. The results confirmed the stable laser operation of a repetition rate of up to 5 kHz, the world record to our knowledge. An average output power of 0.56 kW was obtained at 5 kHz where the shortage of the total discharge current was subjoined by a conventional power supply with seven parallel switching thyratrons, simultaneously working, for the MAGT power supply could not switch a greater current than that switched by one thyratron. It was confirmed by those excitations that the MAGT unit with the MPC could replace a high power commercial thyratron directly for excimer lasers. The switching stability was significantly superior to that of the thyratron in a high repetition rate region, judging from the discharge current wave forms. It should be possible for the MAGT unit, in the future, to directly switch the discharge current within a rise time of 0.1 μs with a magnetic assist.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Observation and stimulation of biological processes using excimer lasers

    NASA Astrophysics Data System (ADS)

    Greulich, Karl-Otto; Wolfrum, Juergen M.

    1990-06-01

    Examples are given for the application o f high power excimer lasers in spectroscopy and processing of biological material. An excimer-laser pumped dye laser serves as light source for a pulsed UV Raman spectrometer which allows resonant Raman studies on nucleic acids. Experiments on the pH induced double helix formation of poly adenylic acid are described. By combining the excimer laser with a distributed feedback dye laser and a streak camera, a picosecond UV fluorescence spectrometer is built up .Tyrosine fluorescence lifetimes of selected tryptophan free peptides with up to 9 amino acids can be explained in a surprisingly simple way: only the directly neighbouring amino acid on the C-terminal side and only a few amino acids on the N-terminal side have an influence on the fluorecscence lifetime of these peptides. Besides spectroscopic applications, the excimer laser serves as light source for processing of biological material. For medical applications , high power UV Laser light has to be transmitted through light guides. A tapered light guide transmitting more than GW/cm2 is described. Microprocessing of biological material with accuracies of a few hundred nanometers can be performed when an excimer pumped dye laser is coupled into a microscope .The resulting UV laser microbeam can be used to introduce foreign genetic material into plant cells, tissues and subcellular organelles such as mitochondria and chioroplasts. Selected pairs of different cells can be fused in the UV laser microbeam under total microscopic control. Finally, one can microdissect human chromosomes and isolate DNA probes for the analysis of human disease.

  3. 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.

  4. 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.

  5. Agreement between clinical history method, Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery.

    PubMed

    Lekhanont, Kaevalin; Nonpassopon, Manachai; Wannarosapark, Khemruetai; Chuckpaiwong, Varintorn

    2015-01-01

    The purpose of this study was to investigate the agreement between the clinical history method (CHM), Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery. Fifty five patients who had myopic LASIK/PRK were recruited into this study. One eye of each patient was randomly selected by a computer-generated process. At 6 months after surgery, postoperative corneal power was calculated from the CHM, Orbscan IIz total optical power at the 3.0 and 4.0 mm zones, and Pentacam equivalent keratometric readings (EKRs) at 3.0, 4.0, and 4.5 mm. Statistical analyses included multilevel models, Pearson's correlation test, and Bland-Altman plots. The Orbscan IIz 3.0-mm and 4.0 mm total optical power, and Pentacam 3.0-mm, 4.0-mm, and 4.5-mm EKR values had strong linear positive correlations with the CHM values (r = 0.90-0.94, P = <0.001, for all comparisons, Pearson's correlation). However, only Pentacam 3.0-mm EKR was not statistically different from CHM (P = 0.17, multilevel models). The mean 3.0- and 4.0-mm total optical powers of the Orbscan IIz were significantly flatter than the values derived from CHM, while the average EKRs of the Pentacam at 4.0 and 4.5 mm were significantly steeper. The mean Orbscan IIz 3.0-mm total optical power was the lowest keratometric reading compared to the other 5 values. Large 95% LoA was observed between each of these values, particularly EKRs, and those obtained with the CHM. The width of the 95% LoA was narrowest for Orbscan IIz 3.0-mm total optical power. In conclusion, the keratometric values extracted from these 3 methods were disparate, either because of a statistically significant difference in the mean values or moderate agreement between them. Therefore, they are not considered equivalent and cannot be used interchangeably.

  6. 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.

  7. Excimer laser surface modification: Process and properties

    SciTech Connect

    Jervis, T.R.; Nastasi, M.; Hirvonen, J.P.

    1992-12-01

    Surface modification can improve materials for structural, tribological, and corrosion applications. Excimer laser light has been shown to provide a rapid means of modifying surfaces through heat treating, surface zone refining, and mixing. Laser pulses at modest power levels can easily melt the surfaces of many materials. Mixing within the molten layer or with the gas ambient may occur, if thermodynamically allowed, followed by rapid solidification. The high temperatures allow the system to overcome kinetic barriers found in some ion mixing experiments. Alternatively, surface zone refinement may result from repeated melting-solidification cycles. Ultraviolet laser light couples energy efficiently to the surface of metallic and ceramic materials. The nature of the modification that follows depends on the properties of the surface and substrate materials. Alloying from both gas and predeposited layer sources has been observed in metals, semiconductors, and ceramics as has surface enrichment of Cr by zone refinement of stainless steel. Rapid solidification after melting often results in the formation of nonequilibrium phases, including amorphous materials. Improved surface properties, including tribology and corrosion resistance, are observed in these materials.

  8. Excimer laser system for atmospheric remote sensing of ozone

    NASA Technical Reports Server (NTRS)

    Tan, K. O.; Ogura, G. T.; Mckee, T. J.; Mcgee, T.

    1987-01-01

    A high-power narrow-linewidth XeCl excimer laser system developed for use by NASA in the remote sensing of atmospheric ozone is described. The laser system is designed for incorporation in a DIAL lidar utilizing stimulated Raman generation for the reference wavelength and sophisticated data averaging techniques. The laser output has a linewidth of 0.002 nm and a beam divergence of 0.15 mrad (FWHM). The laser was operated over a six-hour period with a constant average power of 18 W and a wavelength stable to within + or - 0.0006 nm.

  9. Excimer laser as a manufacturing tool

    NASA Astrophysics Data System (ADS)

    O'Keeffe, Terence R.; Lizotte, Todd E.

    1994-02-01

    In general, laser material processing is carried out using CO2 and YAG systems. This work typically covers welding, cladding and cutting to produce such unlikely products as juice cans and razor blades. Excimer lasers are fast becoming the next most popular processing machine. They are especially suited for the removal of thermally sensitive materials with minimal heat damage and production of micron sized features. Beginning with what can be achieved in various materials this paper will step through the main requirements in developing a fully operational excimer laser process. This should reflect an efficient beam delivery design, high quality aperture masks and specialized part handling equipment. This paper will also address aspects of motion control, vibration isolation and specialized vision systems.

  10. 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.

  11. 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.

  12. Large excimer lasers for fusion

    SciTech Connect

    Jensen, R.J.

    1986-01-01

    Important goals in DOE and DOD programs require multimegajoule laser pulses. For inertial confinement fusion there is also a requirement to deliver the pulse in about 25 nsec with a very particular power vs time profile - all at high overall efficiency and low cost per joule. After exhaustive consideration of various alternatives, our studies have shown that the most cost effective approach to energy scaling is to increase the size of the final amplifiers up to the 200 to 300 kJ level. This conclusion derives largely from the fact that, at a given complexity, costs increase slowly with increasing part size while output energy should increase dramatically. Extrapolations to low cost by drastic cuts in the unit cost of smaller devices through mass production are considered highly risky. At a minimum the requirement to provide, space, optics and mounts for such systems will remain expensive. In recent years there have been dramatic advances in scaling. The Los Alamos LAM has produced over 10 kJ in a single 1/2 nsec pulse. In this paper we explore the issues involved in scaling to higher energy while still maintaining high efficiencies. In the remainder of this paper we will discuss KrF laser scaling for the fusion mission. We will omit most of the discussion of the laser system design, but address only KrF amplifiers.

  13. Automated control of industrial-scale excimer lasers

    NASA Astrophysics Data System (ADS)

    Boardman, Allan D.; Hodgson, Elizabeth M.; Richardson, M. B.; Spence, A. J.; Wilson, A. C.

    1994-08-01

    This paper describes the design, development, and construction of an automated control system for high average power excimer lasers working in an industrial environment. The control system is based on a distributed network of transputers, each dealing with its own area of responsibility. This modular approach was chosen to provide maximum flexibility, allowing the control system to be optimized for particular lasers or special requirements. The development of monitoring and actuating equipment suitable for the unusual demands of an excimer laser is also an essential part of the overall project. Some of the monitoring equipment used is standard, while some has been designed and built at Salford. In particular, a 100 MHz bandwidth optical fiber current sensor has been developed to measure the discharge current. Communications between the sensors and the transputer network are almost entirely optical, with special circuits designed at Salford to convert standard sensor outputs into optical signals. Several different systems are used, according to the response time required.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. 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

  1. Solid sampling with 193-nm excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph

    2007-02-01

    Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires transferring the solid sample into the gas-phase while preserving the sample's stoichiometric composition. Laser ablation in combination with Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a proven powerful technique to meet the requirements for reliable solid sample analysis. The sample is laser ablated in an air-tight cell and the aerosol is carried by an inert gas to a micro-wave induced plasma where its constituents are atomized and ionized prior to mass analysis. The 193 nm excimer laser ablation, in particular, provides athermal sample ablation with very precise lateral ablation and controlled depth profiling. The high photon energy and beam homogeneity of the 193 nm excimer laser system avoids elemental fractionation and permits clean ablation of even transmissive solid materials such as carbonates, fluorites and pure quartz.

  2. A Medical Excimer Laser System For Corneal Surgery And Laser Angioplasty

    NASA Astrophysics Data System (ADS)

    Caro, R. G.; Muller, D. F.

    1987-03-01

    The authors report the design criteria and performance of the ExciMeda UV200 medical excimer laser system. A beam delivery system for controlled photoablative machining of variable power optical lenses in organic material is described. Some of the potential applications of this delivery system in corneal surgery are presented. The uses of the UV200 laser system in other areas of medical research are discussed and, in particular, its application i the field of laser angioplasty is outlined. There has been considerable interest recently in the use of excimer lasers in a variety of fields in medicine. The ultraviolet, high peak power beam emitted by an excimer laser has been shown to be capable of producing very clean and precise cuts in organic material. In particular, cuts can be made in biological material with minimal disturbance of the material adjacent to the cut. For example, tissue can be cut in such a way as to produce negligible charring or vacuolization in adjacent areas of the tissue. This is in marked contrast to the results when organic material is cut by a continuous wave laser such as an Argon ion laser, or c.w. CO2 laser. The potential applications in clinical settings which are suggested by this feature of the interaction of tissue with excimer laser radiation have been largely unrealized outside the laboratory as yet. A primary reason for this is that, until recently, excimer lasers have been available only in a form that was suitable for the scientific laboratory. These lasers required large amounts of space, were not mobile once installed, and required con nection to external sources of water cooling, vacuum exhaust, a high current electrical supply, and a variety of gas bottles including the gases F2 and C12. These systems were not designed with clinical applications in mind, and thus provided unnecessary performance features at the cost of added complexity. They also posed potential electrical and gaseous safety hazards not suitable for a

  3. [Glycosaminoglycans in subepithelial opacity after excimer laser keratectomy].

    PubMed

    Nakayasu, K; Gotoh, T; Ishikawa, T; Kanai, A

    1996-05-01

    We evaluated histochemically the characteristics of glycosaminoglycans and proteoglycans in the corneal subepithelial opacity after excimer laser keratectomy on rabbit corneas. We also performed the same evaluations on the cornea after mechanical keratectomy. Twenty days after the operations, the area immediately subjacent to the epithelium showed strong staining with toluidine blue, alcian blue, and colloidal iron. However, after treatment with chondroitinase ABC or chondroitinase AC, alcian blue staining in this area decreased dramatically. Antilarge proteoglycan antibody also reacted strongly in this area. Histochemical and immunohistochemical examination of the cornea where mechanical keratectomy was done showed basically similar findings with the cornea of excimer laser keratectomy. These results suggest that large-molecula proteoglycans with chondroitine sulfate side chains become localized in the subepithelial area after two different kinds of keratectomies. We presume from histochemical and immunohistochemical observations that the subepithelial opacity observed after excimer laser keratectomy is not a special reaction to excimer laser but simply a corneal scar formed after stromal resection.

  4. Excimer laser: a module of the alopecia areata common protocol.

    PubMed

    McMichael, Amy J

    2013-12-01

    Alopecia areata (AA) is an autoimmune condition characterized by T cell-mediated attack of the hair follicle. The inciting antigenic stimulus is unknown. A dense perbulbar lymphocytic infiltrate and reproducible immunologic abnormalities are hallmark features of the condition. The cellular infiltrate primarily consists of activated T lymphocytes and antigen-presenting Langerhans cells. The xenon chloride excimer laser emits its total energy at the wavelength of 308 nm and therefore is regarded as a "super-narrowband" UVB light source. Excimer laser treatment is highly effective in psoriasis, another T cell-mediated disorder that shares many immunologic features with AA. The excimer laser is superior in inducing T cell apoptosis in vitro compared with narrowband UVB, with paralleled improved clinical efficacy. The excimer laser has been used successfully in patients with AA. In this context, evaluation of the potential benefit of 308-nm excimer laser therapy in the treatment of AA is clinically warranted. Herein, the use of a common treatment protocol with a specifically designed module to study the outcome of excimer laser treatment on moderate-to-severe scalp AA in adults is described.

  5. New 223-nm excimer laser surgical system for photorefractive keratectomy

    NASA Astrophysics Data System (ADS)

    Bagaev, Sergei N.; Razhev, Alexander M.; Zhupikov, Andrey A.

    1999-02-01

    The using of KrCl (223 nm) excimer laser in ophthalmic devices for Photorefractive Keratectomy (PRK) and phototherapeutic Keratectomy (PTK) is offered. The structure and functions of a new surgical UV ophthalmic laser systems Medilex using ArF (193 nm) or KrCl (223 nm) excimer laser for corneal surgery are presented. The systems Medilex with the new optical delivery system is used for photoablative reprofiling of the cornea to correct refraction errors (myopia, hyperopia and astigmatism) and to treat a corneal pathologies. The use of the 223 nanometer laser is proposed to have advantages over the 193 nanometer laser. The results of application of the ophthalmic excimer laser systems Medilex for treatment of myopia are presented.

  6. 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.

  7. Development and clinical application of excimer laser corneal shaping

    NASA Astrophysics Data System (ADS)

    Homolka, Peter; Biowski, R.; Husinsky, Wolfgang; Blaas, C.; Simader, Ch.; Baumgartner, I. Gosch; Kaminski, Stefan; Grabner, G.

    1998-06-01

    Excimer Laser Corneal Shaping using an 193 nm Excimer Laser (ArF) provides a possibility for the fabrication of corneal transplants of various forms for various clinical applications such as (epi-)keratoplasty. Another area of application envisioned is the production of 'living contact lenses' for epikeratophakia. A device for lathing and perforating corneal donor tissue with a scanning laser beam is presented. A new ablation algorithm (Optimized Scanning Laser Ablation) was recently developed and increased the quality of lenticules and donor buttons considerably.

  8. Excimer laser deposition of hydroxyapatite thin films.

    PubMed

    Singh, R K; Qian, F; Nagabushnam, V; Damodaran, R; Moudgil, B M

    1994-06-01

    We have demonstrated a new and simple in situ method to fabricate adherent and dense hydroxyapatite (HA) coatings at relatively low deposition temperatures (500-600 degrees C). Under optimum processing conditions, the HA coatings possess a nominal Ca:P ratio of 1.65 and exhibit a fully crystalline single-phase structure. This deposition technique is based on the application of a pulsed excimer laser (wavelength lambda = 248 nm, pulse duration tau = 25 x 10(-9) s) to ablate a dense stoichiometric HA target. The HA target was prepared by standard ceramic coprecipitation techniques followed by cold pressing and further sintering at 1200 degrees C in air. High substrate temperatures (> or = 600 degrees C) during film deposition led to phosphorus deficient coatings because of re-evaporation of phosphorus during the deposition process. The stabilization of various calcium and phosphorus phases in the film was controlled by a number of process parameters such as substrate temperature, chamber pressure and presence of water vapour in the chamber. This is particularly advantageous for production of HA coatings, since it is known that HA decomposes at high temperatures due to the uncertainty in the starting material stoichiometry. Rutherford backscattering spectrometry, energy dispersive X-ray analysis, transmission electron microscopy, scanning electron microscopy and X-ray diffraction techniques were employed to determine the structure-processing relationships. Qualitative scratch measurements were conducted to determine the adhesion strength of the films.

  9. 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.

  10. Microlens fabrication using an excimer laser and the diaphragm method.

    PubMed

    Chen, Tao; Wang, Tong; Wang, Zhen; Zuo, Tiechuan; Wu, Jian; Liu, Shibing

    2009-06-01

    A new microlens fabrication method using an excimer laser is described in this paper. This method is based on the light vignetting effect. An excimer laser beam was propagated through two groups of fly's-eye lens arrays and separated by the groups, after which divergent beams were formed. When the beams were sectioned by a mask and passed through a circular diaphragm, a vignetting effect was produced relative to an excimer laser mask projection image lens. Then the irradiating intensity at the processing plane varied from the beam center to its margin. This intensity difference in the transverse distribution would result in microlens curvature forming. This diaphragm method has the extinct advantage of short production time, few steps and easy setup construction.

  11. 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.

  12. 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.

  13. 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.

  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. Once upon a time: a hearty glance over the 30-year history of excimer lasers

    NASA Astrophysics Data System (ADS)

    Makarov, Maxime K.

    2005-03-01

    The genesis of excimer lasers is reviewed. Contrary to previous retrospectives, the present analysis is restricted only to physics and technics of discharge pumped Rare-Gas Halides (RGH) excimer lasers. Some side factors like politics or human personality, interfering the development of excimer technology, are also discussed.

  16. 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

  17. 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.

  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. 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.

  1. 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

  2. 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

  3. 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

  4. Evaluation Of An Organosilicon Photoresist For Excimer Laser Lithography

    NASA Astrophysics Data System (ADS)

    McFarland, Janet C.; Orvek, Kevin J.; Ditmer, Gary A.

    1988-01-01

    An organosilicon resist was investigated for use in deep UV laser lithography. The resist was based on 0-trimethylsilyl poly(vinylphenol) resin. It was found to exhibit transparency at 248nm comparable to the transparency of g-line light in conventional novolak resists, making single-layer resist processing possible. The results of single-layer and bi-layer patterning on an excimer laser contact printer are presented. The bi-layer processing uses oxygen reactive ion etching (RIE) for transfer of a top layer pattern into a thick underlying novolak layer.

  5. 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.

  6. Excimer laser with highly coherent radiation

    SciTech Connect

    Atezhev, Vladimir V; Vartapetov, Sergei K; Zhukov, A N; Kurzanov, M A; Obidin, Aleksei Z

    2003-08-31

    Experimental studies aimed at the optimisation of an unstable resonator of an ArF electric-discharge laser are performed. Several optical schemes of an unstable resonator of a single-module laser are proposed and investigated. It is shown that the laser developed on the basis of these schemes is characterised by a high coherence (the spatial coherence length is 1 - 10 mm and the temporal coherence length is 0.5 - 30 mm at a pulse energy of 40 - 290 mJ). (special issue devoted to the memory of academician a m prokhorov)

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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

  13. Spectrocolorimetric control of ancient documents postablation with excimer lasers.

    PubMed

    Soares, O D; Miranda, R M; Costa, J L

    1999-10-20

    The application of excimer lasers in ablation, cleaning, and restoration for the recovery of paper and parchment manuscripts is a recently implemented technique. A report of the use of excimer lasers in a cleaning process by which mud was removed from Islamic papers and parchments is presented. It was found that, because of the close proximity of the binding energies of paper to paper and of paper to mud, it was difficult to maintain control of the ablation process. However, the substrate was not affected. Spectrocolorimetry was used as a technique to detect the effects of ablation on cleaned areas of the manuscripts in terms of change in color appearance and severity of aging postablation. The analysis was performed by comparison of treated and untreated areas. Mathematical modeling was developed to define a representative original color and a color-distribution parameter. Improvements in the measuring method were made to yield the required precision for evaluating differences in color produced by laser ablation and to follow the color evolution after ablation. Results show that the effects of restoration, aging, and the environmental conditions can be individually identified under certain conditions. The method has applications in other domains. PMID:18324157

  14. Spectrocolorimetric Control of Ancient Documents Postablation with Excimer Lasers

    NASA Astrophysics Data System (ADS)

    Soares, Olivério D. D.; Miranda, Rosa M.; Costa, José L. C.

    1999-10-01

    The application of excimer lasers in ablation, cleaning, and restoration for the recovery of paper and parchment manuscripts is a recently implemented technique. A report of the use of excimer lasers in a cleaning process by which mud was removed from Islamic papers and parchments is presented. It was found that, because of the close proximity of the binding energies of paper to paper and of paper to mud, it was difficult to maintain control of the ablation process. However, the substrate was not affected. Spectrocolorimetry was used as a technique to detect the effects of ablation on cleaned areas of the manuscripts in terms of change in color appearance and severity of aging postablation. The analysis was performed by comparison of treated and untreated areas. Mathematical modeling was developed to define a representative original color and a color-distribution parameter. Improvements in the measuring method were made to yield the required precision for evaluating differences in color produced by laser ablation and to follow the color evolution after ablation. Results show that the effects of restoration, aging, and the environmental conditions can be individually identified under certain conditions. The method has applications in other domains.

  15. Spectrocolorimetric control of ancient documents postablation with excimer lasers.

    PubMed

    Soares, O D; Miranda, R M; Costa, J L

    1999-10-20

    The application of excimer lasers in ablation, cleaning, and restoration for the recovery of paper and parchment manuscripts is a recently implemented technique. A report of the use of excimer lasers in a cleaning process by which mud was removed from Islamic papers and parchments is presented. It was found that, because of the close proximity of the binding energies of paper to paper and of paper to mud, it was difficult to maintain control of the ablation process. However, the substrate was not affected. Spectrocolorimetry was used as a technique to detect the effects of ablation on cleaned areas of the manuscripts in terms of change in color appearance and severity of aging postablation. The analysis was performed by comparison of treated and untreated areas. Mathematical modeling was developed to define a representative original color and a color-distribution parameter. Improvements in the measuring method were made to yield the required precision for evaluating differences in color produced by laser ablation and to follow the color evolution after ablation. Results show that the effects of restoration, aging, and the environmental conditions can be individually identified under certain conditions. The method has applications in other domains.

  16. Excimer laser modification of thin AlN films

    NASA Astrophysics Data System (ADS)

    Georgiev, D. G.; Rosenberger, L. W.; Danylyuk, Y. V.; Baird, R. J.; Newaz, G.; Shreve, G.; Auner, G.

    2005-08-01

    The potential of excimer laser micro-processing for surface modification of aluminum nitride (AlN) thin films was studied. Thin films of AlN were deposited by plasma-source molecular beam epitaxy (PSMBE) on silicon and sapphire substrates. These films were then exposed to different fluence levels of KrF ( λ = 248 nm) excimer laser radiation in an ambient air environment, and the changes in the film surface were studied by X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. The results show that there is a narrow range of laser fluences, just above 1.0 J/cm 2, within which mostly photochemical transformations of the film surface take place. These transformations consist of both oxidation and decomposition to metallic Al of the original film within a very thin sub-surface layer with thickness of several tens of nanometers. No changes were observed at fluences below 1.0 J/cm 2. Above a fluence of 1.0 J/cm 2, severe photomechanical damage consisting of film cracking and detachment was found to accompany the photochemical and photothermal changes in the film.

  17. Excimer laser ablation for spatially controlled protein patterns

    NASA Astrophysics Data System (ADS)

    Thissen, Helmut; Hayes, Jason P.; Kingshott, Peter; Johnson, Graham; Harvey, Erol C.; Griesser, Hans J.

    2001-11-01

    Two-dimensional control over the location of proteins on surfaces is desired for a number of applications including diagnostic tests and tissue engineered medical devices. Many of these applications require patterns of specific proteins that allow subsequent two-dimensionally controlled cell attachment. The ideal technique would allow the deposition of specific protein patterns in areas where cell attachment is required, with complete prevention of unspecific protein adsorption in areas where cells are not supposed to attach. In our study, collagen I was used as an example for an extracellular matrix protein known to support the attachment of bovine corneal epithelial cells. An allylamine plasma polymer was deposited on a silicon wafer substrate, followed by grafting of poly(ethylene oxide). Two-dimensional control over the surface chemistry was achieved using a 248 nm excimer laser. Results obtained by XPS and AFM show that the combination of extremely low-fouling surfaces with excimer laser ablation can be used effectively for the production of spatially controlled protein patterns with a resolution of less than 1 micrometers . Furthermore, it was shown that bovine corneal epithelial cell attachment followed exactly the created protein patterns. The presented method is an effective tool for a number of in vitro and in vivo applications.

  18. 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.

  19. Design features of excimer lasers for safe operation in industry and medicine

    NASA Astrophysics Data System (ADS)

    Alvi, Z. M.

    The built-in safety aspects of high-energy excimer lasers designed for use in the aerospace industry are discussed as well as those of low-energy excimer lasers applied in surgery and medicine. High-energy lasers require isolated enclosed facilities such as a properly shielded remote room having a variety of interlocks. Moreover, excimers require the use of dangerous gas mixtures, a preionization subsystem, and a Raman cell for frequency down-shifting. The use of a shielded cone or a collimator would reduce the ionizing radiation exposure within the nominal hazard zone region surrounding the laser head.

  20. Phosphorus diffusion in germanium following implantation and excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Li, Cheng; Huang, Shihao; Lu, Weifang; Yan, Guangming; Zhang, Maotian; Wu, Huanda; Lin, Guangyang; Wei, Jiangbin; Huang, Wei; Lai, Hongkai; Chen, Songyan

    2014-05-01

    We focus our study on phosphorus diffusion in ion-implanted germanium after excimer laser annealing (ELA). An analytical model of laser annealing process is developed to predict the temperature profile and the melted depth in Ge. Based on the heat calculation of ELA, a phosphorus diffusion model has been proposed to predict the dopant profiles in Ge after ELA and fit SIMS profiles perfectly. A comparison between the current-voltage characteristics of Ge n+/p junctions formed by ELA at 250 mJ/cm2 and rapid thermal annealing at 650 °C for 15 s has been made, suggesting that ELA is promising for high performance Ge n+/p junctions.

  1. Corneal topography in the study of astigmatic excimer laser ablation

    NASA Astrophysics Data System (ADS)

    McDonnell, Peter J.

    1992-08-01

    Corneal astigmatism, both naturally occurring and iatrogenically induced, is a commonly encountered problem. Examination of corneal topography with instruments that digitize reflected ring images and calculate corneal geometry suggests that corneal astigmatism often deviates from spherocylindrical optics; the observed topography may be highly asymmetrical about the center of the pupil. Currently used incisional procedures are limited in terms of predictability of surgical outcome. The 193 nm excimer laser can be used to alter anterior corneal curvature and flatten the cornea to correct myopia. For correction of astigmatism, a slit-opening in the laser delivery system can be used to selectively flatten the steep meridian. Early results using this procedure for correction of iatrogenically induced high corneal astigmatism are promising. A nationwide multicenter clinical trial is now underway in the United States to evaluate this technique for the correction of naturally occurring astigmatism and compound myopic astigmatism.

  2. Qualification of diode foil materials for excimer lasers

    NASA Astrophysics Data System (ADS)

    Anderson, R. G.; Shurter, R. P.; Rose, E. A.

    The Aurora facility at Los Alamos National Laboratory uses KrF excimer lasers to produce 248 nm light for inertial confinement fusion applications. Diodes in each amplifier produce relativistic electron beams to pump a Kr-F-Ar gas mixture. A foil is necessary to separate the vacuum diode from the laser gas. High tensile strength, high electron transmission, low ultraviolet reflectivity, and chemical compatibility with fluorine have been identified as requisite foil properties. Several different materials were acquired and tested for use as diode foils. Transmission and fluorine compatibility tests were performed using the Electron Gun Test Facility (EGTF) at Los Alamos. Off-line tests of tensile strength and reflectivity were performed. Titanium foil, which is commonly used as a diode foil, was found to generate solid and gaseous fluoride compounds, some of which are highly reactive in contact with water vapor.

  3. 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.

  4. Initial experience with excimer laser angioplasty for coronary ostial stenoses.

    PubMed Central

    Lawson, C S; Cooper, I C; Webb-Peploe, M M

    1993-01-01

    The excimer laser has several potential advantages over conventional balloon angioplasty in the management of stenoses of the native coronary arteries and of the ostia of saphenous vein grafts. Its use in nine patients, eight of whom were classed as high risk, is described. Four lesions involved the ostia of saphenous vein grafts, three of protected left main stems, and two of native right coronary arteries. Stand alone laser was used in seven cases and laser with additional balloon angioplasty was used in two vein graft stenoses. Acute laser success was achieved in all cases, with a mean reduction of stenosis from 82% to 34% after laser alone and to 28% when balloon angioplasty was used as well. One patient died during laser angioplasty to a non-ostial lesion (procedural success rate 89%) and a second died ten weeks after the procedure. In one patient recurrent angina developed (clinical recurrence rate 25%) and restenosis was confirmed on angiography. Follow up angiography was also performed on the other six surviving patients, all of whom were symptom free and none of whom showed evidence of significant restenosis (restenosis rate 14%). With a mean follow up of 19.7 months the overall success rate was 67%. Images PMID:8461226

  5. 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.

  6. Enhancing the absorption of aluminum alloys by irradiation with an excimer laser

    NASA Astrophysics Data System (ADS)

    Scott, Graeme; Williams, Stewart W.; Morgan, P. C.; Dempster, M.

    1994-09-01

    Aluminum alloys typically have as received reflectivities of 85 - 95% at 10.6 micrometers making many laser processes difficult or impossible. These values have been reduced to as low as 1 - 2% by optimizing the processing parameters of an excimer laser used to modify the surface structure of 8090 and 2024 Al alloys and pure Al prior to their exposure to a CO2 laser. The most significant excimer processing parameters were found to be the scan pattern of the excimer beam, the number of pulses per scan pattern step (dwell time) and the laser fluence. Optimizing these parameters allows the production of a rough oxide rich surface and reflectivities at 10.6 micrometers routinely below 10%. Preliminary results are presented from the practical implementation of the technique to a dual wavelength (CO2/excimer) cutting system. Increases in cutting speeds of between 2 - 4 times are demonstrated with 8090 Al-Li alloy using dual wavelength laser processing.

  7. 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

  8. 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.

  9. Quantitative solid sample analysis by ArF excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph; von Oldershausen, Georg

    2005-06-01

    Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires transferring the solid sample into the gas-phase while preserving the sample's stoichiometric composition. Laser Ablation in combination with inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a proven powerful technique to meet the requirements for reliable solid sample analysis. The sample is laser ablated in an air-tight cell and the aerosol is carried by an inert gas to a micro-wave induced plasma where its constituents are atomized and ionized prior to mass analysis. The 193 nm excimer laser ablation, in particular, provides athermal sample ablation with very precise lateral ablation and controlled depth profiling. The high photon energy and beam homogeneity of the 193 nm excimer laser system avoids elemental fractionation and permits clean ablation of even transmissive solid materials such as carbonates, fluorites and pure quartz.

  10. Excimer laser crystallization of amorphous silicon on metallic substrate

    NASA Astrophysics Data System (ADS)

    Delachat, F.; Antoni, F.; Slaoui, A.; Cayron, C.; Ducros, C.; Lerat, J.-F.; Emeraud, T.; Negru, R.; Huet, K.; Reydet, P.-L.

    2013-06-01

    An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm-2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm-2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites' columnar growth.

  11. Enhancement of adhesion on polyether etherketone (PEEK) by excimer laser treatments

    SciTech Connect

    Sadras, B.; Laurens, P.; Decobert, F.; Arefi, F.; Amouroux, J.

    1996-12-31

    Due to its important chemical stability, polyether-etherketone (PEEK) thermoplastic presents poor adhesive bonding properties. The possibilities of enhancing the PEEK adhesive properties by excimer laser pretreatments are investigated. Surface modifications are characterized, depending on the experimental working conditions, using SEM, profilometry, XPS, wettability and mechanical tests. Lap shear strength values show that excimer laser irradiation improve PEEK adhesion bonding properties for all treatment conditions (energy, atmosphere).

  12. Overview of recent advances in excimer laser technology at Los Alamos

    SciTech Connect

    Bigio, I.J.; Sze, R.C.; Taylor, A.J.; Gibson, R.B.

    1988-01-01

    From among the areas of excimer laser development at Los Alamos two are selected for further discussion: ultra-high brightness excimer laser systems and discharge-pumped XeF(C..-->..A) lasers operating in the blue-green portion of the spectrum. Two different high brightness systems are described. One is based on small-aperture KrF amplifiers, while the other is based on a large-aperture XeCl amplifier. The XeF(C..-->..A) laser is tunable from 435 to 525 nm, and may one day become a viable alternative to pulsed dye lasers for many applications. 14 refs., 4 figs.

  13. COMPONENTS OF LASER SYSTEMS: Pumping of the GARPUN wide-aperture excimer laser by counterpropagating electron beams

    NASA Astrophysics Data System (ADS)

    Arlantsev, S. V.; Grigor'yants, E. A.; Vadkovskii, A. D.; Zvorykin, V. D.; Metreveli, G. E.

    1994-03-01

    The transport of high-current electron beams from vacuum diodes to the laser chamber of the GARPUN wide-aperture excimer laser was investigated experimentally and theoretically. The processes involving the transport of fast electrons in argon and krypton in a longitudinal magnetic field were also studied. Pumping by counter-propagating electron beams resulted in the deposition of up to 2.1 kJ of energy into the active medium of the laser, which corresponded to a specific excitation power of ~0.8 MW cm-3 with an inhomogeneity of less than 20% over a 12 cm × 18 cm aperture. The efficiency of the energy deposition by electron beams was ~60% and the overall efficiency of the laser pumping system was ~16%.

  14. Excimer laser ablation lithography applied to the fabrication of reflective diffractive optics

    NASA Astrophysics Data System (ADS)

    Flury, M.; Benatmane, A.; Gérard, P.; Montgomery, P. C.; Fontaine, J.; Engel, T.; Schunck, J. P.; Fogarassy, E.

    2003-03-01

    We propose a low cost technique for the production of diffractive optical elements (DOE). These elements are devoted to high power lasers beam shaping in the mid-infrared wavelengths. This process called laser ablation lithography (LAL), may seem similar to laser beam writing (LBW) in the way the whole DOE's design is reproduced pixel by pixel on the substrate placed on a computer controlled XY translation stage. A first difference is that the photoresist is not exposed with UV light but is directly ablated with short excimer laser pulses. Furthermore, with LAL technique the size of the smallest pixel ( 5 μm×5 μm) is more than 10 times greater than those produced by LBW. We discuss in details the experimental set-up for LAL and demonstrate that it gives a resolution up to 10 times greater than photolithography with flexible masks. This makes LAL a promising solution for the production of DOE for use with Nd:YAG lasers. New applications of DOEs are finally introduced with high power lasers sources, such as laser marking or multi-point brazing.

  15. Report on the Study of Radiation Damage in Calcium Fluoride and Magnesium Fluoride Crystals for use in Excimer Laser Applications

    SciTech Connect

    None, None

    1999-10-04

    A study was performed to investigate the effects of radiation damage in calcium fluoride and magnesium fluoride crystals caused by gamma rays and UV photons from excimer lasers. The purpose was to study and correlate the damage caused by these two different mechanisms in various types of material used for fabricating optical elements in high power excimer lasers and lens systems of lithography tools. These optical systems are easily damaged by the laser itself, and it is necessary to use only the most radiation resistant materials for certain key elements. It was found that a clear correlation exists between the, radiation induced damage caused by high energy gamma rays and that produced by UV photons from the excimer laser. This correlation allows a simple procedure to be developed to select the most radiation resistant material at the ingot level, which would be later used to fabricate various components of the optical system. This avoids incurring the additional cost of fabricating actual optical elements with material that would later be damaged under prolonged use. The result of this screening procedure can result in a considerable savings in the overall cost of the lens and laser system.

  16. 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.)

  17. 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.

  18. Excimer laser surgery for myopia and myopic astigmatism.

    PubMed

    Hadden, O B; Morris, A T; Ring, C P

    1995-08-01

    Photorefractive keratectomy using the Summit Excimer Laser has been carried out on 1333 eyes with myopia or myopic astigmatism which have been followed up for six months or longer. Of those, 607 have been followed up for one year. Of the eyes with myopia or myopic astigmatism of up to 3 dioptres spherical equivalent, at one year 85.6% had unaided vision of 6/6, 97.2% 6/9 or better, and 99.4% 6/12 or better. Of the eyes between -3.25 and -6.00 dioptres spherical equivalent at one year 72.1% achieved 6/6 vision unaided, 88.8% 6/9 or better, and 94.2% 6/12 or better. Of the eyes between -6.25 and -10.00 dioptres, at one year 49.6% achieved 6/6 vision unaided, 76.1% 6/9 or better and 88.0% 6/12 or better. To achieve these figures, 28% of the patients had astigmatic keratotomy, either two or three weeks before photorefractive keratectomy, or at the same time as photorefractive keratectomy. Photorefractive keratectomy is as predictable as radial keratotomy in eyes of under 6 dioptres myopia, but is more predictable than radial keratotomy in higher myopia. Photorefractive keratectomy has the advantages of leaving an eye which is structurally sound, and without diurnal variation of focusing. PMID:8534441

  19. 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.

  20. 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

  1. 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.

  2. KrF-excimer laser pretreatment and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Weichenhain, R.; Wesner, D. A.; Pfleging, W.; Horn, H.; Kreutz, E. W.

    1997-02-01

    Metal film adhesion to polymers can be improved by pretreatment with UV-laser radiation before metal deposition. Chemical changes associated with irradiation are investigated for polyimide (PI) and polybutylene terephthalate (PBT) surfaces. Irradiated surfaces are coated with aluminum films ≤10 nm in thickness, enabling the effects of irradiation on the metal/polymer interface to be studied. Irradiation is done in air with KrF-excimer laser radiation (λ=248 nm) at fluences per pulse ≤600 mJ/cm2. The threshold fluence εt for material removal is determined by profilometry measurements of etched features, and the chemical properties of the polymer and the metal/polymer interface are studied with X-ray photoelectron spectroscopy (XPS). Aluminum films are thermally evaporated in situ in the XPS spectrometer. Irradiation of PI at fluences near εt (41 mJ/cm2) results in loss of oxygen and opening of the imide ring, resulting in doubly bonded nitrogen species. After evaporation of aluminum the carbonyl (CO) C1s XPS signal is reduced in intensity, and both Al0 and Al3+ are found, the latter being located at the interface. In comparison to unirradiated areas, irradiated areas have more aluminum in total and a higher proportion of interfacial Al3+ species, indicating an increase in the concentration of metal binding sites. Although for PBT the O to C ratio also decreases with irradiation at fluences near εt (38 mJ/cm2), changes in the amounts of Al0 or Al3+ for irradiated areas in comparison to unirradiated areas are much smaller than for PI and consist mainly of a slight enhancement of Al0 for films deposited on irradiated surfaces.

  3. Experimental simulation of radioactive decontamination with Excimer laser

    NASA Astrophysics Data System (ADS)

    Gao, Zhixing; Tang, Xiuzhang; Ma, Meihua; Zhang, Zhentao

    2013-07-01

    Laser ablation is a powerful tool to clean the radioactively contaminated surface in nuclear industry. A prototype was set up to test the decontamination of the radioactively contaminated surface using simulated sample. A laser induced breakdown spectroscopy was used to monitor the progress of the contaminated surface layer removal. More than 80% of the contamination was removed after 100 shots KrF laser irradiation with the intensity of 1J/cm2.

  4. 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.

  5. 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.

  6. 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.

  7. Excimer lasers in cardiovascular surgery: Ablation products and photoacoustic spectrum of the arterial wall

    NASA Astrophysics Data System (ADS)

    Singleton, D. L.; Paraskevopoulos, G.; Jolly, G. S.; Irwin, R. S.; McKenney, D. J.; Nip, W. S.; Farrell, E. M.; Higginson, L. A. J.

    1986-03-01

    Photoacoustic spectra of normal artery wall and of atherosclerotic plaque are reported. Threshold fluences for ablative formation of gaseous products for each excimer laser line were calculated from the photoacoustic spectrum and the measured threshold for the KrF laser.

  8. 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.

  9. 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.

  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. 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.

  12. 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.

  13. Micro-mirror formed using excimer laser processing in a polymer waveguide

    NASA Astrophysics Data System (ADS)

    Shioda, Tsuyoshi

    2005-04-01

    A micro-mirror formed using excimer laser processing for a fluorinated polyimide waveguide film was demonstrated. The tilted excimer laser irradiation to the waveguide core formed a micro-mirror with an angle of 45 +/- 1-degree. The micro-mirror had convex profile and exhibited a lens effect as a concave mirror. The micro-mirror, as formed, exhibited a low reflection loss of approximately 0.6dB at a wavelength of 850nm. This technique applied to flexible optical and electrical circuit board.

  14. Excimer laser debulking for percutaneous coronary intervention in left main coronary artery disease.

    PubMed

    Topaz, On; Polkampally, Pritam R; Mohanty, Pramod K; Rizk, Maged; Bangs, Julie; Bernardo, Nelson L

    2009-11-01

    Excimer laser has been successfully applied to complex atherosclerotic plaques in acute coronary syndromes; however, its role in debulking in left main coronary artery disease has not been fully explored. Details of a series of 20 patients who underwent excimer laser revascularization of a spectrum of left main coronary artery lesions are presented. Twenty symptomatic patients who received excimer laser debulking were examined for procedural outcome and follow up results. The left main coronary artery was characterized as protected, semi-protected, poorly protected, or unprotected, depending on the presence or absence of patent bypass grafts to the left anterior descending (LAD) and circumflex (CX) arteries. A fully protected left main coronary artery (LMCA) was present in only 20% of the patients. The target lesions included 11(55%) distal LMCA stenoses, six (30%) ostial stenoses, and one (5%) mid-portion lesions. Two (10%) patients had in-stent re-stenosis of the entire length of the LMCA. Small (0.7 mm-1.4 mm) excimer laser catheters were mostly used. A relatively high number of laser energy pulses (1,334 +/- 643) were required to achieve adequate debulking. Successful LMCA intervention was performed in 19 (95%) patients, while in-hospital complications occurred in only one (5%) patient. Subacute/late stent thrombosis developed 3 months after the procedure in one patient, and two patients died from non-cardiac causes during follow-up. Lesions in LMCAs can be revascularized in selected patients by laser debulking and adjunct stenting. Inadequate protection by bypass grafts and decreased left ventricular function do not contradict utilization of excimer laser. Small laser catheters and high energy levels are required during laser debulking of stenoses of left main coronary arteries.

  15. Effects of Plasma Formation on the Cesium Diode (DPAL) and Excimer (XPAL) Pumped Alkali Laser

    NASA Astrophysics Data System (ADS)

    Markosyan, Aram H.; Kushner, Mark J.

    2015-09-01

    Diode pumped alkali lasers (DPALs) and excimer pumped alkali lasers (XPALs) are being investigated as a means to convert optical pumps having poor optical quality to laser radiation having high optical quality. DPALs sustained in Cs vapor are pumped on the D2(852.35 nm), Cs(62S1/2) --> Cs(62P3/2) , transition and lase on the D1(894.59 nm) transition, Cs(62P1/2) --> Cs(62S1/2) . Collisional mixing (spin orbit relaxation) of the Cs(62P3/2) and Cs(62P1/2) levels is a key part of this three-level (in fact, a quasi-two-level) laser scheme. In the five-level XPAL pumping scheme, the CsAr(B2Σ1/ 2 +) state is optically pumped by 836.7 nm pulses, which later dissociates and produces Cs(62P3/2) . As in DPAL, a collisional relaxant transfers the population of Cs(62P3/2) to Cs(62P1/2) , which enables lasing on D1 transition. A first principals global computer model has been developed for both systems to investigate the effects of plasma formation on the laser performance. Argon is used as a buffer gas and nitrogen or ethane are used as a collisional relaxant at total pressure of 600 Torr at temperatures of 350-450 K, which produces vapor pressures of Cs of <0.1 Torr. In both systems, a plasma formation in excess of 1014 - 1016cm-3 occurs, which potentially reduces laser output power by electron collisional mixing of upper and lower laser levels. Work supported by DoD High Energy Laser Multidisc, Res. Initiative.

  16. 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

  17. 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.

  18. Corneal aldehyde dehydrogenase and glutathione S-transferase activity after excimer laser keratectomy in guinea pigs

    PubMed Central

    Bilgihan, K.; Bilgihan, A.; Turkozkan, N.

    1998-01-01

    BACKGROUND—The free radical balance of the eye may be changed by excimer laser keratectomy. Previous studies have demonstrated that excimer laser keratectomy increases the corneal temperature, decreases the superoxide dismutase activity of the aqueous, and induces lipid peroxidation in the superficial corneal stroma. Aldehyde dehydrogenase (ALDH) and glutathione S-transferase (GST) are known to play an important role in corneal metabolism, particularly in detoxification of aldehydes, which are generated from free radical reactions.
METHODS—In three groups of guinea pigs mechanical corneal de-epithelialisation was performed in group I, superficial corneal photoablation in group II, and deep corneal photoablation in group III, and the corneal ALDH and GST activities measured after 48 hours.
RESULTS—The mean ALDH and GST activities of group I and II showed no differences compared with the controls (p>0.05). The corneal ALDH activities were found to be significantly decreased (p<0.05) and GST activities increased (p<0.05) in group III.
CONCLUSION—These results suggest that excimer laser treatment of high myopia may change the ALDH and GST activities, metabolism, and free radical balance of the cornea.

 Keywords: excimer laser keratectomy; aldehyde dehydrogenase; glutathione S-transferase PMID:9602629

  19. Excimer Laser Angioplasty: Initial Clinical Results With A Percutaneous Transluminal Procedure In Total Peripheral Artery Occlusion

    NASA Astrophysics Data System (ADS)

    Wollenek, Gregor; Laufer, Guenter; Hohla, Kristian L.; Grabenwoeger, Florian; Klepetko, Walter

    1989-04-01

    Laser energy has the potential to recanalize obstructive atherosclerotic vessels as an alternative or an adjunct to either bypass surgery or balloon angioplasty. But conventional lasers cause thermal side effects which may lead to extensive damage to neighboring layers. In contrast, excimer laser irradiation in the far ultraviolet range has proved to minimize or avoid these injuries to vessel walls. To evaluate the clinical feasibility of excimer laser angioplasty (ELA), we have performed basic investigations including histologic examination by light microscopy, scanning and electron microscopy, and temperature measurements, and later on in vivo animal trials. Using 308 nm irradiation (XeCl) we have treated the first patient ever to undergo ELA, and the procedure was successful: after recanalization of a total occlusion of a superficial femoral artery, dilatation resulted in sufficient blood supply to the periphery.

  20. Extremely long life and low-cost 193nm excimer laser chamber technology for 450mm wafer multipatterning lithography

    NASA Astrophysics Data System (ADS)

    Tsushima, Hiroaki; Katsuumi, Hisakazu; Ikeda, Hiroyuki; Asayama, Takeshi; Kumazaki, Takahito; Kurosu, Akihiko; Ohta, Takeshi; Kakizaki, Kouji; Matsunaga, Takashi; Mizoguchi, Hakaru

    2014-04-01

    193nm ArF excimer lasers are widely used as light sources for the lithography process of semiconductor production. 193nm ArF exicmer lasers are expected to continue to be the main solution in photolithography, since advanced lithography technologies such as multiple patterning and Self-Aligned Double Patterning (SADP) are being developed. In order to apply these technologies to high-volume semiconductor manufacturing, the key is to reduce the total operating cost. To reduce the total operating cost, life extension of consumable part and reduction of power consumption are an important factor. The chamber life time and power consumption are a main factor to decide the total operating cost. Therefore, we have developed the new technology for extension of the chamber life time and low electricity consumption. In this paper, we will report the new technology to extend the life time of the laser chamber and to reduce the electricity consumption.

  1. Finite elements analysis of heteroepitaxial SiGe layers grown by excimer laser

    NASA Astrophysics Data System (ADS)

    Conde, J. C.; González, P.; Lusquiños, F.; Chiussi, S.; Serra, J.; León, B.

    2005-07-01

    In this work, the finite elements analysis using ANSYS ® (8.0) of the heteroepitaxial SiGe alloy formation induced by excimer lasers is presented. The numerical simulation of the temperature distribution induced by KrF excimer laser (energy densities 0.50 < Φ< 0.55 J/cm 2) on thin amorphous Ge films (10 nm thick) deposited on Si<1 0 0> substrates is obtained. An acceptable agreement between the numerical simulations and the experimental results is found. The melting depth is also evaluated and the laser energy density threshold for the partial melting of the Si substrate is estimated. It allows us to determine the optimum conditions to achieve high quality epitaxy. For both the cases, the temperature profile versus time on the top of the Ge film and at the Ge/Si interface are obtained.

  2. 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

  3. The effect of excimer laser annealing on ZnO nanowires and their field effect transistors.

    PubMed

    Maeng, Jongsun; Heo, Sungho; Jo, Gunho; Choe, Minhyeok; Kim, Seonghyun; Hwang, Hyunsang; Lee, Takhee

    2009-03-01

    We have investigated the effect of excimer laser annealing on the chemical bonding, electrical, and optical properties of ZnO nanowires. We demonstrate that after laser annealing on the ZnO nanowire field effect transistors, the on-current increases and the threshold voltage shifts in the negative gate bias direction. These electrical results are attributed to the increase of oxygen vacancies as n-type dopants after laser annealing, consistent with the shifts towards higher binding energies of Zn 2p and O 1s in the x-ray photoelectron spectroscopy analysis of as-grown nanowires and laser-annealed ZnO nanowires.

  4. 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.

  5. [Corneal wound healing after perforating and non-perforating excimer laser keratectomy. An experimental study].

    PubMed

    Koch, J W; Lang, G K; Kolkmeier, J; Naumann, G O

    1990-01-01

    For clinical use of the excimer laser more detailed knowledge of corneal wound healing is necessary. With an ArF excimer laser (193 nm, 750 mJ/cm2, 20 Hz) and a special slit mask system perforating and non-perforating keratectomies were performed in a series of 55 rabbits with a follow-up from one hour to six months post-op. After enucleation the corneas were immediately processed for light microscopy, scanning and transmission electron microscopy and vital staining of the endothelium (trypan blue/alizarin red S). In perforating cuts the endothelial reaction consists of polymegathism, migration, formation of multi-nucleated giant cells, metaplasia-like proliferation and ultimately stable reformation of the cell pattern (1h to 42d). Epithelium fills the anterior wound gap within three days with subsequent regression of the plug. Fibroblastic activity in the adjacent stroma leads to cellular immigration, production of new collageneous lamellae and complete reorganization of the wound cleft (1d to 6m). Nonperforating excisions showed similar healing tendency of stroma and epithelium, but no severe endothelial damage could be detected. Compared with former studies using knife incisions our results do not reveal significant difference regarding epithelial and stromal wound healing events. The encouraging healing tendency of the endothelium--similar to regeneration after ultrasound and Nd:YAG-laser damage--also confirms the applicability of excimer lasers in corneal surgery.

  6. 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.

  7. 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

  8. [Diagnosis of open-angle glaucoma after myopic excimer laser corneal refractive surgery].

    PubMed

    Wu, Ling-ling

    2013-11-01

    Patients with high myopia are at high risk of glaucoma and are difficult to be discovered at early stage in the case of existing glaucoma. Myopic excimer laser corneal refractive surgery changes the structure of the eye, which makes early glaucoma diagnosis more difficult. Furthermore, refractive surgery may aggravate existing condition of glaucoma. To prevent the exacerbation of glaucoma, it is great important to perform the preoperative glaucoma risk assessment. In this paper, we presented the key diagnostic points of glaucoma assessment before and after excimer laser refractive surgery and discussed the postoperative intraocular pressure measurements and its impact on the diagnosis and treatment of glaucoma including characterization of open angle glaucoma and long-term follow up in patients with high myopia.

  9. 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.

  10. 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.

  11. Emission from ionic cesium fluoride excimers excited by a laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Kubodera, S.; Frey, L.; Wisoff, P. J.; Sauerbrey, R.

    1988-06-01

    Fluorescence was observed from the Cs(2+)F(-) state at 185 nm using a laser-produced plasma as the excitation source in a CsF heat pipe. The dependence of the ionic excimer emission on CsF vapor pressure and temporally resolved emission from the Cs(2+)F(-) is analyzed. It is found that the pressure dependence of the fluorescence is influenced by self-absorption in the CsF vapor.

  12. 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.

  13. 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

  14. Application of XeCl308 nm excimer laser radiation to mutagenesis of industrial microorganisms

    NASA Astrophysics Data System (ADS)

    Alifano, P.; Lorusso, A.; Nassisi, V.; Talà, A.; Tredici, S. M.

    (UV) lamps are widely used in mutagenesis-selection protocols. Nevertheless, since the eighties, due to the development of excimer lasers, new frontiers in the study of UV applications have been opened. It has been established that the presence of an intact SOS response system is required for the mutagenic effect of UV254 nm. The exposure to UV254 nm radiation is not mutagenic for Escherichia coli mutants lacking the RecA protein, the regulator of the SOS response. We have recently demonstrated that at variance with the UV254 nm mutagenesis, the UV308 nm mutagenesis by XeCl308 nm excimer laser is RecA-independent. This suggests that the UV308 nm might be mutagenic also in microorganisms naturally lacking the SOS response. In this study, we have developed an innovative mutagenesis protocol based on a homemade XeCl308 nm excimer laser and have demonstrated its efficiency on mutagenesis of Nonomuraea American type culture collection 39727, an industrial strain producing an antibiotic, which is relatively refractory to UV254 nm radiation-induced mutagenesis.

  15. 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

  16. 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.

  17. Evaluation of an opacity lensometer for determining corneal clarity following excimer laser photoablation

    SciTech Connect

    Andrade, H.A.; McDonald, M.B.; Liu, J.C.; Abdelmegeed, M.; Varnell, R.; Sunderland, G. )

    1990-09-01

    The appearance of haze in the central cornea following photoablation with a 193 nm excimer laser is an important factor in the postoperative course of this procedure. Data from 37 human eyes treated with photorefractive keratectomy, 4 eyes treated with phototherapeutic keratectomy, and 5 untreated eyes were used to evaluate the ability of a commercially available opacity lensometer to provide an objective measure of corneal clarity. We found that the opacity lensometer was able to detect light scattered from the cornea but was not sufficiently sensitive to distinguish reliably among excimer-treated eyes with degrees of corneal haze evaluated as clear, trace, or 1+ by slit-lamp microscope examination. In untreated, clear corneas, the values obtained with the opacity lensometer in eyes measured with and without a clear contact lens were within one unit of each other for any given eye, but values from eye to eye varied over a range of six units. In a test simulating different amounts of corneal haze using contact lenses evenly coated with nail polish enamel, the log-transformed opacity lensometer values varied directly with percent light scattering as determined by spectrophotometry. These results suggest that the opacity lensometer measurements are reliable and reproducible, but that in the human cornea something is being measured by the opacity lensometer that is not taken into account in clinical slit-lamp microscope evaluation. Overall, it appears that, in its present form, this instrument is not useful to measure corneal clarity after excimer laser photoablation.

  18. 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.

  19. Corneal surgery by two-dimensional scanning of a low-energy excimer laser beam

    NASA Astrophysics Data System (ADS)

    Unkroth, Angela; Pachomis, Karin; Walther, Jens-Uwe; Zimare, D.

    1994-06-01

    We describe a new multipurpose maskless method of corneal surgery based on the point-by-point scanning of a focused laser beam which allows the application of a low-energy excimer laser. The crucial scanning parameters to achieve a smooth corneal surface have been investigated. A computer program for the simulation and optimization of the point-by-point scanning process has been developed and tested on contact lenses consisting of PMMA. In addition, a method of measuring the eye-movement by means of the computer-assisted interpretation of photographs was proved for its application in an eye-tracking-system.

  20. Excimer laser-induced ablation in corneal surgery by a two-dimensional scanning method

    NASA Astrophysics Data System (ADS)

    Unkroth, Angela; Pachomis, Karin; Welsch, Eberhard; Walther, Jens-Uwe; Zimare, D.; Krause, Ulf

    1994-02-01

    We describe a new multi-purpose maskless method of corneal surgery based on the point-by- point scanning of a focused laser beam which allows the application of a low-energy excimer laser. The crucial scanning parameters (beam diameter, step width, overlap...) to achieve a smooth corneal surface have been investigated. A computer program for the simulation and optimization of the point-by-point scanning process has been developed and tested on contact lenses consisting of PMMA. In addition, a method of measuring the eye-movement by means of the computer-assisted interpretation of photographs was proved for its application in an eye- tracking-system.

  1. Influencing adherence properties of polymers by excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Breuer, J.; Metev, Simeon; Sepold, Gerd; Krueger, G.; Hennemann, O. D.

    1991-09-01

    The paper describes investigations concerning the enhancement of adhesive bonding strength between polypropylen (PP) and adhesive on a resinous basis by UV-laser-induced photochemical reactions. Possible mechanisms of the laser-activated processes are discussed. A preliminary result of the experimental examinations is the bonding strength enhancement of more than 5 X under certain conditions.

  2. Output coupler design of unstable cavities for excimer lasers.

    PubMed

    Giuri, C; Perrone, M R; Piccinno, V

    1997-02-20

    We tested the performance of a XeCl laser with unstable resonators using as an output coupler a phase unifying (PU) mirror, a super-Gaussian mirror, and a hard-edge mirror. The quantitative impact of the output coupler design on the energy extraction efficiency, near-field profile, far-field energy distribution, and spatial coherence time evolution has been investigated. Laser beams of larger brightness have been obtained with the PU unstable cavity. A faster growth of the laser beam spatial coherence has been observed with the PU cavity by time-resolved, far-field measurements. PMID:18250783

  3. Surgical removal of infected pacemaker leads without cardiopulmonary bypass after failed extraction using the Excimer Laser Sheath Extraction System.

    PubMed

    Tokunaga, Chiho; Enomoto, Yoshiharu; Sato, Fujio; Kanemoto, Shinya; Matsushita, Shonosuke; Hiramatsu, Yuji; Aonuma, Kazutaka; Sakakibara, Yuzuru

    2012-03-01

    With the growing number of cardiac pacemakers and internal cardioverter defibrillator implantations, problems with endocardial lead infection have been increasing. The newly developed Excimer Laser Sheath Lead Extraction System has been recognized as being highly useful for removing chronic infected leads. However, serious bleeding complications are a concern when this system is used. Here we report our experience with a 67-year-old man who was diagnosed with pacemaker endocarditis. Initially, lead removal was attempted using the Excimer Laser Sheath Extraction System, though this was abandoned because of severe adhesion of the leads and the junction of the supra vena cava (SVC) with the right atrium. Surgical removal of the leads was performed without using cardiopulmonary bypass and the leads were removed without any complications. During surgery, we found there was a silent perforation of the innominate vein brought about by the Excimer Laser Sheath System. Also, the junction of the SVC with the right atrium was thought to be an area potentially at high risk of perforation, because of a lack of surrounding tissue. It is our opinion that those who carry out procedures with the Excimer Laser Sheath System should understand the potential risk of perforation based on cardiac anatomy and should be prepared for lethal bleeding complications. Also, for emergent situations, we believe that close backup by a cardiovascular surgical team should be considered essential for performing the Excimer Laser Sheath Lead Extraction safely.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    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.

  5. 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.

  6. Low temperature oxidation of crystalline silicon using excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    Nayar, Vishal; Boyd, Ian W.; Goodall, F. N.; Arthur, G.

    In this paper we present a study of ultra-violet laser oxidation of silicon at low temperature (< 650° C), using both 249 and 193 nm radiation. Calculation of the surface temperature rise during the laser pulses suggests that non-thermal oxidation mechanisms are present. In addition to the growth of planar thin oxides over macroscopic areas, a new technique for selectivity oxidising silicon by direct image projection, i.e., direct growth lithography (DGL) is also preliminarily presented.

  7. Diode laser probing of CO2 and CO vibrational excitation produced by collisions with high energy electrons from 193 nm excimer laser photolysis of iodine

    NASA Astrophysics Data System (ADS)

    Hewitt, Scott A.; Zhu, Lei; Flynn, George W.

    1992-11-01

    The vibrational, rotational, and translational excitation of CO2 and CO following excimer laser photolysis of iodine is evaluated by means of time-domain absorption spectroscopy. In spite of the lack of change in the rotational and translational molecular energy, pronounced vibrational excitation is noted. The excimer laser photolysis of the iodine is thought to generate hot electrons that collide with the CO2 leading to vibrationally excited molecules.

  8. Oxygen free radical damage in the cornea after excimer laser therapy

    PubMed Central

    Hayashi, S.; Ishimoto, S.; Wu, G.; Wee, W.; Rao, N.; McDonnell, P.

    1997-01-01

    AIMS/BACKGROUND—To evaluate the extent of oxygen radical damage in the cornea after excimer laser ablation.
METHODS—The 193 nm argon fluoride excimer laser was programmed for an average fluence of 150 mJ/cm2, with a firing rate of 5 Hz and an ablation zone diameter of 6 mm. Phototherapeutic keratectomy was performed to remove 30 µm of epithelium and 50 µm of stroma from the corneas of New Zealand white rabbits. Oxidative tissue damage after laser was determined by measuring oxidised lipids (conjugated dienes and ketodienes) in corneal lipid extracts, and by fast blue B staining to localise the lipid peroxide in the tissue.
RESULTS—Conjugated diene levels were 3.73 (SD 0.56) nmol per hemicornea in ablated corneas and 1.99 (0.33) nmol per hemicornea in normal corneas (p = 0.0044). Ketodiene levels were 2.72 (0.38) nmol per hemicornea in treated corneas and 0.91 (0.12) nmol per hemicornea in normal corneas (p < 0.001). Fast blue B staining disclosed that the tissue damage occurred primarily on the surface of the ablated cornea.
CONCLUSION—The presence of lipid peroxidation in the superficial corneal stroma in excimer laser treated corneas was demonstrated. This lipid peroxidation could be from oxygen free radicals generated by the infiltrating polymorphonuclear cells at the site of tissue damage.

 PMID:9059249

  9. Clinical use of the 193-nm excimer laser in the treatment of corneal scars.

    PubMed

    Sher, N A; Bowers, R A; Zabel, R W; Frantz, J M; Eiferman, R A; Brown, D C; Rowsey, J J; Parker, P; Chen, V; Lindstrom, R L

    1991-04-01

    Phototherapeutic keratectomy using a 193-nm excimer laser was performed at four centers on 33 sighted patients with corneal opacity and/or irregular astigmatism. Pathologic conditions included anterior stromal and superficial scarring from postinfectious and posttraumatic causes, including inactive herpes simplex virus, anterior corneal dystrophies, recurrent erosions, granular dystrophy, and band keratopathy. Most patients received peribulbar anesthesia and underwent removal of the epithelium prior to laser ablation. A majority of patients had a reduction in the amount of corneal scarring and approximately half had improved visual acuity. No intraocular reaction or changes in endothelial counts were seen, and some patients avoided the need for penetrating keratoplasty. Reepithelialization usually occurred within 4 or 5 days and we noted no significant scarring secondary to use of the laser. It was difficult to eliminate preexisting irregular astigmatism despite the use of surface modulators, such as methylcellulose. A hyperopic shift secondary to corneal flattening was encountered in approximately 50% of the patients. A combination of myopic ablation, followed immediately by a secondary hyperopic steepening, may minimize this refractive change. The 193-nm excimer laser is an effective new tool in the treatment of selected patients with superficial corneal opacity from a variety of conditions. PMID:2012547

  10. Excimer laser assisted TiN and WC removal from tools as a novel decoating technology

    NASA Astrophysics Data System (ADS)

    Schubert, Emil; Schutte, K.; Emmel, A.; Bergmann, Hans W.

    1995-03-01

    Hard coatings, e.g. TiN or WC on high quality tools are regenerated several times, due to their high costs. Conventional decoating techniques are of chemical nature and problematically regarding the handling of the chemical residues. In addition to that the lifetime of recoated tools after chemical decoating of the damaged functional layers is drastically reduced compared to new tools. Excimer laser treatment using the so-called `Duplex-Technique' enables a damage-free removal of the hard coatings with much longer lifetime of recoated tools than those of chemically decoated. The handling of the waste material is extremely easy using a laser processing head with an integrated exhaust system, that was designed at ATZ- EVUS. The paper gives a detailed presentation of the developed Duplex-Technique, the influence of the laser parameters and the obtained surface properties. Results of internal stress measurements, roughness values, changes in chemical composition and the surface appearance are described. From the technological point of view the removal rates, the productivity and last not least the superior performance of excimer laser decoated and PVD recoated tools in a lifetime test are demonstrated, compared to newly coated and chemical decoated tools.

  11. Excimer laser angioplasty in acute myocardial infarction (the CARMEL multicenter trial).

    PubMed

    Topaz, On; Ebersole, Douglas; Das, Tony; Alderman, Edwin L; Madyoon, Hooman; Vora, Kishor; Baker, John D; Hilton, David; Dahm, Johannes B

    2004-03-15

    Patients with acute myocardial infarction (AMI) with thrombus-laden lesions constitute a revascularization challenge. Thrombus and atherosclerotic plaque absorb laser energy; thus, we studied the safety and efficacy of excimer laser in AMI. In a multicenter trial, 151 patients with AMI underwent excimer laser angioplasty. Baseline left ventricular ejection fraction was 44 +/- 13%, and 13% of patients were in cardiogenic shock. A saphenous vein graft was the target vessel in 21%. Quantitative coronary angiography and statistical analysis were performed by independent core laboratories. A 95% device success, 97% angiographic success, and 91% overall procedural success rate were recorded. Maximal laser gain was achieved in lesions with extensive thrombus burden (p <0.03 vs small burden). Thrombolysis In Myocardial Infarction (TIMI) trial flow increased significantly by laser: 1.2 +/- 1.1 to 2.8 +/- 0.5 (p <0.001), reaching a final 3.0 +/- 0.2 (p <0.001 vs baseline). Minimal luminal diameter increased by laser from 0.5 +/- 0.5 to 1.6 +/- 0.5 mm (mean +/- SD, p <0.001), followed by 2.7 +/- 0.6 mm after stenting (p <0.001 vs baseline and vs after laser). Laser decreased target stenosis from 83 +/- 17% to 52 +/- 15% (mean +/- SD, p <0.001 vs baseline), followed by 20 +/- 16% after stenting (p <0.001 vs baseline and vs after laser). Six patients (4%) died, each presented with cardiogenic shock. Complications included perforation (0.6%), dissection (5% major, 3% minor), acute closure (0.6%), distal embolization (2%), and bleeding (3%). In a multivariant regression model, absence of cardiogenic shock was a significant factor affecting procedural success. Thus, in the setting of AMI, gaining maximal thrombus dissolution in lesions with extensive thrombus burden, combined with a considerable increase in minimal luminal diameter and restoration of anterograde TIMI flow, support successful debulking by excimer laser. The presence of thrombus does not adversely affect procedural

  12. 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.

  13. Shock wave and material vapour plume propagation during excimer laser ablation of aluminium samples

    NASA Astrophysics Data System (ADS)

    Jeong, S. H.; Greif, R.; Russo, R. E.

    1999-10-01

    A probe beam deflection technique was utilized to measure the propagation of a shock wave and material vapour plume generated during excimer laser ablation of aluminium samples. The measured transit time of the laser-induced shock wave was compared with the prediction based on an ideal blast-wave model, using the Sedov-Taylor solution. The prediction of the incident laser energy converted into the laser-induced gasdynamic flow utilizing this blast-wave model overestimated the efficiency, even under conditions when the measured shock-wave velocity follows the correct model relation. The propagation of material vapour was measured from the deflection of the probe beam at later times. The propagation velocity of material vapour ranged from 20-40 m s-1 with a greater velocity near the target surface.

  14. Surface modification of dental tissues by KrF excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Sivakumar, M.; Oliveira, V.; Vilar, R.

    2007-02-01

    Laser treatment is a promising technique for dental applications such as caries removal, dental hypersensitivity reduction and improvement of the bond strength between dentin and restoration materials. In this study the topographic and morphological changes induced in enamel and dentin surfaces by treating with KrF excimer laser radiation were studied as a function of the number of laser pulses and radiation fluence by scanning electron microscopy and optical profilometry. For enamel, independently of the fluence used, material removal occurs preferentially at the prisms sheaths, leading to the formation of surface pits of a few micrometers. For dentin, a cone-like topography develops when the tubules are approximately parallel to the laser beam direction and the radiation fluence is within the range 0.5 to 1.5 J/cm2. For higher fluences, the treated surfaces are flat and covered with a layer of re-solidified materials.

  15. 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.

  16. Effect of 308-nm excimer laser light on peri-implantitis-associated bacteria: an in vitro investigation.

    PubMed

    Deppe, Herbert; Horch, Hans-Henning; Schrödl, Veit; Haczek, Cornelia; Miethke, Thomas

    2007-11-01

    Dental implants are becoming increasingly important in prosthodontic rehabilitation. Bacterial infections, however, can induce bone loss and jeopardize clinical success. Recent literature has demonstrated that infrared CO(2) laser light is suitable for the decontamination of exposed implant surfaces. The aim of the present study was to investigate the influence of 308-nm excimer laser irradiation on peri-implantitis-associated bacteria in vitro. In this study, a XeCl excimer laser (308 nm) was used (Summit Technology, Boston, USA). Both aerobe (Streptococcus mutans, S. sanguis, Actinomyces naeslundii) and anaerobe microorganisms (A. odontolyticus, Prevotella melaninogenica) were tested. According to previous studies, a constant energy of 0.8 J/cm(2) and a constant frequency of 20 Hz were used for all irradiations. Colony-forming units after laser irradiation were counted. Excimer laser irradiation showed significant influence on the growth of all microorganisms. As compared to S. mutans and S. sanguis, A. naeslundii demonstrated higher sensitivity to laser irradiation. Anaerobe microorganisms, in contrast, demonstrated that a total of 200 pulses were sufficient to reduce the replication of these germs for more than 99.9%. Excimer laser irradiation (lambda = 308 nm) can significantly reduce both aerobe and anaerobe microorganisms. Depending on the parameters chosen, 200 pulses are sufficient for sterilization. New studies are necessary to evaluate if this wavelength is more of value in the treatment of peri-implantitis than other wavelengths or conventional therapies.

  17. 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.

  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. Tailoring immobilization of immunoglobulin by excimer laser for biosensor applications.

    PubMed

    Sima, Felix; Axente, Emanuel; Ristoscu, Carmen; Mihailescu, Ion N; Kononenko, Taras V; Nagovitsin, Ilya A; Chudinova, Galina; Konov, Vitaly I; Socol, Marcela; Enculescu, Ionut; Sima, Livia E; Petrescu, Stefana M

    2011-02-01

    The sheltered transfer and immobilization of rabbit anti-human antiserum immunoglobulin G (IgG) by matrix-assisted pulsed laser evaporation (MAPLE) are reported. The iced targets submitted to laser irradiation consisted of 0.2-2 mg/mL IgG blended or not with lipid (L-α-phosphatidylcholine dipalmitoyl) dissolved in distilled water-based saline buffer. Thin IgG coatings were obtained at room temperature onto glass, fused silica, or silicon substrates. Ten thousand subsequent laser pulses of 0.33, 0.5, or 0.67 J/cm(2) fluence were applied for the synthesis of each sample. Morphology and composition of the thin films were studied by optical, scanning, and atomic force microscopy and Fourier transformed infrared spectrometry. Optical labeling methods such as spectrofluorimetry and fluorescence microscopy were selected to verify the biosensor transduction principle because of their high sensitivity for detecting low amounts of antigen (IgG). Protein immobilization to the substrate surface was demonstrated for all obtained structures after immersion in the donkey anti-rabbit secondary antibody solution. The IgG transfer and immobilization onto substrates were improved by addition of lipid to MAPLE solutions.

  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.

  1. 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.

  2. 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.

  3. Advances in industrial high-power lasers

    NASA Astrophysics Data System (ADS)

    Schlueter, Holger

    2005-03-01

    Four major types of laser sources are used for material processing. Excluding Excimer lasers, this paper focuses on advances in High Power CO2 lasers, Solid State Lasers and Diode Lasers. Because of their unrivaled cost to brightness relationship the fast axial flow CO2 laser remains unrivaled for flat-sheet laser cutting. Adding approximately a kW of output power ever four years, this laser type has been propelling the entire sheet metal fabrication industry for the last two decades. Very robust, diffusion cooled annular discharge CO2 lasers with 2kW output power have enabled robot mounted lasers for 3D applications. Solid State Lasers are chosen mainly because of the option of fiber delivery. Industrial applications still rely on lamp-pumped Nd:YAG lasers with guaranteed output powers of 4.5 kW at the workpiece. The introduction of the diode pumped Thin Disc Laser 4.5 kW laser enables new applications such as the Programmable Focus Optics. Pumping the Thin Disc Laser requires highly reliable High Power Diode Lasers. The necessary reliability can only be achieved in a modern, automated semiconductor manufacturing facility. For Diode Lasers, electro-optical efficiencies above 65% are as important as the passivation of the facets to avoid Burn-In power degradation.

  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. 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.

  6. Characterization of polymers after a surface treatment at low excimer laser fluences

    NASA Astrophysics Data System (ADS)

    Laurens, Patricia; Ould Bouali, M.; Petit, S.; Sadras, Benedicte

    2000-02-01

    The modifications induced by an excimer laser irradiation at 193 nm or 248 nm on organic surfaces, below their ablation threshold, were investigated for different kinds of polymers such as: PEEK (Polyether Etherketone), PC (Polycarbonate), PET (Polyethylene terephtalate). Treatments were carried under argon or air at different laser fluences. Treated surfaces were characterized by XPS (X-rays Photoelectron Spectroscopy) and surface wettability measurements. For, all the studied polymers, the results shows that the surface modifications first depended on the laser wavelength. Surface oxidation occurred at 193 nm, leading to the formation of polar groups (carbonyls, carboxyls, hydroxyls) and inducing an increase of the surface energy. Treatments at 248 nm never induced any oxygen enrichment of the surface. This is due to the loss of oxygen by CO or CO2 desorption at this wavelength.

  7. Effects of XeCl excimer lasers and fluoride application on artificial caries-like lesions

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra B. B.; Phan, T.; Liaw, Lih-Huei L.; Berns, Michael W.

    1994-09-01

    In this study the affects of a pulsed excimer laser emitting at 308 nm (XeCl) on enamel susceptibility to artificial caries-like lesions were investigated. Additional effects of fluoride (F) application were also studied and SEC examinations performed. Sixty-four extracted human molar teeth were coated with acid resistant varnish leaving four windows, then sectioned, leaving one window on each tooth quarter. The windows were treated in one of the following ways: untreated (control), or lased, or exposed to 4 min. APF (1.23% F) before lasing, or exposed to 4 min. APF (1.23% F) after lasing. After lasing, microhardness profiles were obtained and SEM was performed. Caries resistance was generally increased at moderate fluences. F application combined with lasing enhanced caries resistance at some parameters. SEM showed effects ranging from minimal to localized effects to extended glazing. Pulsed excimer laser irradiation, especially combined with topical F application can inhibit development of artificial caries-like lesions.

  8. Treatment of band keratopathy by excimer laser phototherapeutic keratectomy: surgical techniques and long term follow up.

    PubMed Central

    O'Brart, D P; Gartry, D S; Lohmann, C P; Patmore, A L; Kerr Muir, M G; Marshall, J

    1993-01-01

    A series of 122 eyes with band keratopathy was treated by excimer laser phototherapeutic keratectomy (PTK), with a mean follow up of over 12.3 months (range 3 to 60 months). A single photoablation zone was used to remove the opacity over the visual axis in smooth surfaced band deposition. In eyes with reduced vision, an improvement was reported in 88% and in a series of 66 eyes mean Snellen visual acuity increased significantly (p < 0.05, t = 2.27). A reduction in glare was reported in 88% and in a series of 17 patients, visual contrast sensitivity (p < 0.01) and measurements of disability glare (p < 0.01) improved postoperatively. The mean hyperopic shift in 32 eyes at 6 months was 1.4 D (range 0-4.25 D). Multiple overlapping ablation zones, with mechanical debulking of large calcium plaques, were used to smooth the irregular corneal surface in eyes with rough bands. Ocular discomfort was improved in 95%. Band keratopathy recurred in nine eyes (8%) within 2 to 30 months (mean 12 months) of surgery, with silicone oil responsible in five eyes. Reablation was necessary in three eyes and performed successfully in all cases. Excimer laser PTK is a safe and effective outpatient treatment for band keratopathy. Images PMID:8280683

  9. Confocal microscope observations of the cornea after excimer laser refractive surgery

    NASA Astrophysics Data System (ADS)

    Gierek-Lapinska, Ariadna; Gierek-Ciaciura, Stanislawa; Mrukwa, Ewa; Rokita-Wala, Iwona; Sarzynski, Adam

    1998-10-01

    Purpose: The aim of this study was to observe human corneas after Photorefractive keratectomy, in vivo, using the Scanning Slit Confocal Microscope `Confoscan P4' (Tomey). Material and method: The material consists of 80 corneas of 45 patients where in vivo, non-invasive evaluation of the corneal structures was performed with a confocal microscope. The confocal microscopic examination was performed in cases after excimer laser refractive surgery and analyzed together with the type of the procedure (myopia, hyperopia and astigmatism correction), and with the patients' age and sex. The results obtained in the right and left eye of each patient after bilateral procedures were compared. The state of the cornea was analyzed in relation to follow-up time. Results: The observations consist of the structure of corneal epithelium, stromal keratocytes, topography of nerve fibers, appearance of Bowman's and Descemet's membranes and condition of endothelial cells. Conclusion: The confocal microscope allows non-invasive in vivo observations of the corneal structures and is capable of the evaluation of corneal healing after excimer laser refractive procedures.

  10. Endovascular treatment of in-stent restenosis using excimer laser angioplasty and drug eluting balloons.

    PubMed

    Van Den Berg, J C; Pedrotti, M; Canevascini, R; Chimchila Chevili, S; Giovannacci, L; Rosso, R

    2012-04-01

    In-stent restenosis after endovascular treatment of stenotic and occlusive disease of the infrainguinal arteries is still a clinical challenge. In this paper an overview of the current status of drug-eluting balloon technology and results of clinical trials with drug-eluting balloon angioplasty is given. Furthermore a case series of 10 patients with in-stent restenosis that were treated with excimer laser angioplasty and drug eluting balloons is described. In this case series the mean lesion length treated was 115 mm, and the mean time to occurrence of restenosis after initial treatment was 7.2 months. At a mean follow-up (of all patients) of 7.6 months no target vessel revascularization was seen. In 7 patients that had Duplex and/or angiographic control (mean follow-up 7 months) no signs of neointimal hyperplasia were demonstrated. These short-term data compare favorable to results obtained with standard balloon angioplasty and cutting-balloon angioplasty. Long-term follow-up is necessary to define the role of combined excimer laser and drug-eluting balloon angioplasty in the treatment of in-stent restenosis further.

  11. Excimer laser ablation of aluminum: influence of spot size on ablation rate

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2016-11-01

    The dependence of ablation rate of an Al alloy on laser beam spot size (10–150 µm) was investigated using an ArF excimer laser operating at a wavelength of 193 nm and pulse width less than 4 ns. Ablation was conducted in air at a fluence of 11 J cm‑2 and at a repetition rate of 20 Hz. Surface morphology and depth of craters produced by a variable number of laser pulses were characterized using optical and scanning electron microscopy. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used as an additional diagnostic technique to estimate the amount of material ablated from craters produced by a laser beam of different diameters. Laser beam spot size and number of laser pulses applied to the same spot were found to influence crater morphology, ablation rate, shape and amount of particles deposited at or around the crater rim. Ablation rate was found to be less dependent on spot size for craters greater than 85 µm. A four-fold increase in ablation rate was observed with decreasing crater size from 150 µm to 10 µm.

  12. 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.

  13. 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.

  14. Measurements of barium photocathode quantum yields at four excimer laser wavelengths

    SciTech Connect

    Van Loy, M.D.; Young, A.T.; Leung, K.N.

    1992-06-01

    The electron quantum yields from barium cathodes excited by excimer laser radiation at 193, 248, 308, and 351 nm have been determined. Experiments with different cathode surface preparation techniques reveal that deposition of barium film a few microns thick on a clean copper surface under moderate vacuum conditions achieves relatively high quantum efficiencies. Quantum yields measured from surfaces prepared in this manner are 2.3 x 10{sup -3} at 193 nm, 7.6 x 10{sup - 4} at 248 nm, 6.1 x 10{sup -4} at 308 nm, and 4.0 x 10{sup -4} at 351 nm. Other preparation techniques, such as laser cleaning of a solid barium surface, produced quantum yields that were at least an order of magnitude lower than these values.

  15. 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).

  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. PMMA microstructure as KrF excimer-laser LIGA material

    NASA Astrophysics Data System (ADS)

    Yang, Chii-Rong; Chou, Bruce C. S.; Chou, Hsiao-Yu; Lin, Frank H. S.; Kuo, Wen-Kai; Luo, Roger G. S.; Chang, Jer-Wei; Wei, Z. J.

    1998-08-01

    PMMA (polymethyl methacrylate) has been widely used as x-ray LIGA material for its good features of electrical acid plating of all common metals to industrial applications. Unlike the tough characteristics of polyimide in almost all alkaline and acid solutions, PMMA is easily removed in chemical etchants after electroplating process. For this reason, ablation- etching characteristics of PMMA material for 3D microstructures fabrication using a 248 nm KrF excimer laser were investigated. Moreover, the uses of the laminated dry film were also studied in this work. Experimental results show that PMMA microstructures can produce the near-vertical side- wall profile as the laser fluence up to 2.5 J/cm2. PMMA templates with high aspect ratio of around 25 were demonstrated, and the sequential electroplating processes have realized the metallic microstructures. Moreover, the microstructures fabricated in dry film show the perfect side- wall quality, and no residues of debris were found.

  18. 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.

  19. Evaluation of the Efficacy of Excimer Laser Ablation of Cross-Linked Porcine Cornea

    PubMed Central

    Chen, Shihao; Li, Yini; Stojanovic, Aleksander; Zhang, Jia; Wang, Yibo; Wang, Qinmei; Seiler, Theo

    2012-01-01

    Background Combination of riboflavin/UVA cross-linking (CXL) and excimer laser ablation is a promising therapy for treating corneal ectasia. The cornea is strengthened by cross-linking, while the irregular astigmatism is reduced by laser ablation. This study aims to compare the efficacy of excimer laser ablation on porcine corneas with and without cross-linking. Methods and Findings The porcine cornea was de-epithelialized and treated with 0.1% riboflavin solution for 30 minutes. A half of the cornea was exposed to UVA-radiation for another 30 minutes while the controlled half of the cornea was protected from the UVA using a metal shield. Photo therapeutic keratectomy (PTK) was then performed on the central cornea. Corneal thickness of 5 paired locations on the horizontal line, ±0.5, ±1.0, ±1.5, ±2.0, and ±2.5 mm from the central spot, were measured using optical coherence tomography prior to and after PTK. The ablation depth was then determined by the corneal thickness. There was a 9% difference (P<0.001) in the overall ablation depth between the CXL-half corneas (158±22 µm) and the control-half corneas (174±26 µm). The ablation depths of all 5 correspondent locations on the CXL-half were significantly smaller (P<0.001). Conclusion The efficacy of the laser ablation seems to be lower in cross-linked cornea. Current ablation algorithms may need to be modified for cross-linked corneas. PMID:23056269

  20. 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.

  1. Effect of an antioxydant cream versus placebo in patients with vitiligo in association with excimer laser. A pilot randomized, investigator-blinded, and half-side comparison trial.

    PubMed

    Leone, G; Paro Vidolin, A

    2015-08-01

    The aim of this study was to evaluate the combined effect of excimer laser and a topical antioxidant in the treatment for vitiligo. The study was conducted in a single blinded design on 10 vitiligo patients with symmetrical vitiligo lesions treated with the active antioxidant or a placebo that were irradiated with an excimer laser. Results have shown that the lesions treated with the active cream achieved earlier regimentation compared to the placebo. The use of a cream containing antioxidants may improve the results of excimer laser treatment in patients with vitiligo.

  2. Visual outcomes of topography-guided excimer laser surgery for treatment of patients with irregular astigmatism.

    PubMed

    Ghoreishi, Mohammad; Naderi Beni, Afsaneh; Naderi Beni, Zahra

    2014-01-01

    The aim of this study was to evaluate the efficacy, safety, and predictability of topography-guided treatments to enhance refractive status following other corneal surgical procedures. In a prospective case series study, 28 consecutive eyes of 26 patients with irregular astigmatism after radial keratotomy, corneal transplant, small hyperopic and myopic excimer laser optical zones, and corneal scars were operated. Laser-assisted in situ keratomileusis (LASIK) (n = 8) and photorefractive keratectomy (PRK) (n = 20) were performed using the ALLEGRETTO WAVE excimer laser and topography-guided customized ablation treatment software. Preoperative and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest and cycloplegic refraction, and corneal topography with asphericity were analyzed in 12 months follow-up. Uncorrected visual acuity (UCVA) changed from 0.2 ± 0.2 or (20/100 ± 20/100) to 0.51 ± 0.31 or (20/40 ± 20/60) in the LASIK group (P = 0.01) and from 0.34 ± 0.16 or (20/60 ± 20/120) to 0.5 ± 0.23 or (20/40 ± 20/80) in the PRK group (P = 0.01). Refractive cylinder decreased from -3.2 ± 0.84 diopters (D) to -2.06 ± 0.42 D in the LASIK group (P = 0.07) and from -2.25 ± 0.39 D to -1.5 ± 0.23 D in the PRK group (P = 0.008). Best corrected visual acuity did not change significantly in either group. Topography-guided treatment is effective in correcting the irregular astigmatism after refractive surgery. Topography-guided PRK can significantly reduce irregular astigmatism and increase the UCVA and BCVA.

  3. Excimer laser patterning of PEDOT:PSS thin-films on flexible barrier foils: A surface analysis study

    NASA Astrophysics Data System (ADS)

    Naithani, Sanjeev; Schaubroeck, David; Vercammen, Yannick; Mandamparambil, Rajesh; Yakimets, Iryna; Van Vaeck, Luc; Van Steenberge, Geert

    2013-09-01

    Selective laser patterning of thin organic films is an important aspect in the roll-to-roll production of organic electronic devices such as organic light emitting diodes (OLEDs). An excimer laser is well suited for the patterning and structuring of polymer thin films as their UV absorption is significant. Selective removal of a transparent conducting polymer PEDOT:PSS (poly(3,4-ethylene dioxythiophene):polystyrene sulfonate) on a multilayered (inorganic-organic-inorganic) barrier and a flexible PEN (polyethylene napthalate) substrate has been studied using a KrF excimer laser. The ablation craters were characterized with electron microscopy and profilometry. For the first time, chemical surface analysis of the patterned area was performed with Time-Of-Flight Static Secondary Ion Mass Spectrometry (TOF-S-SIMS), providing a detailed insight of the surface composition after laser ablation and plasma post-treatments.

  4. Fluorescence imaging inside an internal combustion engine using tunable excimer lasers.

    PubMed

    Andresen, P; Meijer, G; Schlüter, H; Voges, H; Koch, A; Hentschel, W; Oppermann, W; Rothe, E

    1990-06-01

    Tunable excimer lasers are used to obtain 2-D images of molecular (and some state-specific) density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access. Natural fluorescence (i.e., without a laser) is used for some OH pictures, normal laser-induced fluorescence (LIF) for those of NO and of the isooctane fuel, and laser-induced predissociative fluorescence (LIPF) for other OH pictures and for those of O(2). Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species. LIPF works well at high pressures, is state specific, and is ideally suited to follow turbulent processes. No similar measurements in engines have been previously reported. Pictures are taken in succeeding engine cycles. Their sequence is either at a particular point of the engine's cycle to show cyclic fluctuations, or at succeeding portions of the cycle to illustrate the progress of the gasdynamics or of the combustion.

  5. Topography and raytracing analysis of patients with excellent visual acuity 3 months after excimer laser photorefractive keratectomy for myopia.

    PubMed

    Maguire, L J; Zabel, R W; Parker, P; Lindstrom, R L

    1991-01-01

    We performed topography and raytracing analysis 3 months after surgery on five consecutive eyes of five patients, which had excimer laser photorefractive keratectomy for myopia. Three of the five eyes had uncorrected postoperative visual acuity of 20/20 or better. Two eyes had an uncorrected vision of 20/40. In three of five eyes, the area of excimer ablation was centered within 1.0 mm of the optical axis. Three other eyes showed decentration that ranged from 1.1 to 1.5 mm. The range of surface power seen within 2 mm of the central keratoscope ring was as follows: patient CK = 37.50 to 39.50 diopters; patient CA = 40.50 D to 44.80 D; patient CW = 37.90 D to 42.20 D; patient AC = 35.50 D to 39.00 D; patient DT = 34.50 D to 41.40 D. Topography patterns differed from eye to eye. A raytracing program modeled refraction of 20/80 and 20/20 "E" of 100%, 50%, 25%, 12.5% and 6.25% contrast through all measured points on the central 10 keratoscope rings of the five postoperative corneas. The five computer-derived images were ranked subjectively according to the observed degree of image degradation by three observers. Two eyes showed discernible 20/20 E's even at the 12.5% contrast level. Little to no ghost image was seen. Two eyes showed degraded but discernible 20/20 letters at higher levels of contrast only. These eyes showed moderate ghost images that were most apparent in the high-contrast 20/80 letters. One eye showed poor resolution of the 100% contrast 20/20 letter and moderately severe ghost images.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2043557

  6. 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.

  7. 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.

  8. Gratings in indium oxide film overlayers on ion-exchanged waveguides by excimer laser micromachining

    NASA Astrophysics Data System (ADS)

    Pissadakis, S.; Reekie, L.; Zervas, M. N.; Wilkinson, J. S.; Kiriakidis, G.

    2001-02-01

    Relief Bragg gratings were imprinted by 248 nm interferometric excimer laser ablation on potassium ion-exchanged channel waveguides in BK-7 glass overlaid with a thin high-index InOx film. Using five pulses of energy density 60 mJ/cm2, a spectral transmittance notch of depth 66% and ΔλFWHM<0.1 nm was obtained at 1547 nm in the TE polarization for a waveguide having a nominal width of 8 μm and a 135-nm-thick InOx overlayer. In waveguides coated with 100 nm InOx, with widths increasing from 3 to 8 μm, the reflection wavelength shifted by 0.12 nm/μm and the reflectivity increased monotonically.

  9. Micromachining of polyurethane (PU) polymer using a KrF excimer laser (248 nm)

    NASA Astrophysics Data System (ADS)

    Singh, Sarabpreet; Sharma, Sunil

    2014-12-01

    Polyurethane (PU) polymer, due to its biocompatibility, weather resistance, and favorable physical properties, finds a number of applications in medical implants, protective coatings, and as a prototype material for structural components in MEMS devices. An excimer laser (wavelength = 248 nm, FWHM = 25 ns) is employed for micromachining of polyurethane (PU) polymer. For air environment, the ablation rate is 0.18 μm/pulse and for underwater environment, the ablation rate is 0.07 μm/pulse (with underwater ablation threshold as 0.10 J/cm2), which concluded low taper angles (∼32°) for in air as compared to high taper angles (∼65°) with underwater micromachining. The experimental results for air and under water micromachining demonstrate ablation process as a combination of photo-thermal and photo-chemical mechanism.

  10. Deposition of high quality TiN films by excimer laser ablation in reactive gas

    NASA Astrophysics Data System (ADS)

    Mihailescu, I. N.; Chitica, N.; Nistor, L. C.; Popescu, M.; Teodorescu, V. S.; Ursu, I.; Andrei, A.; Barborica, A.; Luches, A.; De Giorgi, M. Luisa; Perrone, A.; Dubreuil, B.; Hermann, J.

    1993-11-01

    A new laser method is proposed for the deposition of high purity, hard fcc TiN layers of unlimited thickness. The film thickness can be very finely controlled mainly through the intermediary of the number of applied laser pulses as the deposition rate is of only 0.02-0.05 nm/pulse. The ablation is promoted from a Ti target by high intensity multipulse excimer laser irradiation in a low pressure N2 ambient gas while the forming compound is collected on a Si single-crystalline wafer. The best results have been obtained for an ambient pressure of p=10-30 mTorr and a distance between the target and support of d=10 mm. It is shown that the formation of a liquid phase within the irradiated zone, maintained even after the end of a laser pulse, is the most important requisite for TiN formation. TiN is then ablated as a stoichio- metric phase.

  11. 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

  12. Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

    NASA Astrophysics Data System (ADS)

    El hamali, S. O.; Cranton, W. M.; Kalfagiannis, N.; Hou, X.; Ranson, R.; Koutsogeorgis, D. C.

    2016-05-01

    High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10-3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10-4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm2. Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes.

  13. 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.

  14. Microhollow Cathode Discharge Excimer Sources

    NASA Astrophysics Data System (ADS)

    Moselhy, M.; El-Habachi, A.; Shi, W.; Stark, R. H.; Schoenbach, K. H.

    2000-10-01

    Microhollow cathode discharges (MHCDs) are direct current, high-pressure, non-equilibrium gas discharges. When operated in Ar, Xe, ArF and XeCl, these discharges were found to be intense sources of excimer radiation at 130, 172, 193, 308 nm, respectively. Internal conversion efficiencies (from input electrical power to output optical power) of 1% (Ar), 8% (Xe), 2% (ArF) and 3% (XeCl) were achieved [1,2,3]. The spatial distribution of the xenon excimer source was studied by means of an ICCD-MAX intensified CCD camera. The measurements showed that the source expands with current and becomes reduced in size with pressure. The maximum radiant emittance (radiant power per source area) was measured as 2 W/cm^2 at atmospheric pressure and a discharge current of 3 mA. The peak irradiance (radiant power per target area) for a single discharge was calculated to be 3 mW/cm^2 at a distance of 1 cm from the source. Operating multiple discharges in parallel allows us to generate flat panel excimer lamps with an irradiance approaching the value of the radiant emittance (2 W/cm^2). In order to increase the irradiance further MHCDs could be operated in series. First experiments with two discharges in series have shown that the radiant emittance increases linearly with the number of discharges [3]. Besides using systems of MHCDs as lamps, efforts to utilize “stacked discharges” as excimer laser medium are underway. This work is supported by NSF and DARPA. 1. Ahmed El-Habachi and Karl H. Schoenbach, Appl. Phys. Lett. 73, 885 (1998). 2. Wenhui Shi, Ahmed El-Habachi, and Karl H. Schoenbach, Bull. Am. Phys. Soc. 44, 25 (1999). 3. Ahmed El-Habachi et. al., “Series Operation of Direct Current Xenon Chloride Excimer Sources”, to appear in J. Appl. Phys.

  15. Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Luong, G. V.; Wirths, S.; Stefanov, S.; Holländer, B.; Schubert, J.; Conde, J. C.; Stoica, T.; Breuer, U.; Chiussi, S.; Goryll, M.; Buca, D.; Mantl, S.

    2013-05-01

    Excimer Laser Annealing (ELA) with a wavelength of 248 nm is used to study doping of biaxialy compressively strained Si1-xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1 × 1015 As+/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650 Ω/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62 Ω/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods.

  16. 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.

  17. 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

  18. 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

  19. Excimer laser fragmentation fluorescence spectroscopy for real-time monitoring of combustion generated pollutants

    NASA Astrophysics Data System (ADS)

    Damm, Christopher John

    Toxic pollutant emissions from combustion pose a hazard to public and environmental health. Better diagnostic techniques would benefit emissions monitoring programs and aid research aimed at understanding toxic pollutant formation and behavior. Excimer Laser Fragmentation Fluorescence Spectroscopy (ELFFS) provides sensitive, real-time, in situ measurements of several important combustion related pollutants. This thesis demonstrates the capabilities of ELFFS for detecting amines in combustion exhausts and carbonaceous particulate matter from engines. ELFFS photofragments target species using a 193 nm excimer laser to form fluorescent signature species. The NH (A--X) band at 336 nm is used to monitor ammonia, ammonium nitrate and ammonium sulfate. There are no major interferences in this spectral region. The sensitivity is approximately 100 ppb (1 second measurement) for ammonia in post flame gases and 100 ppb (mole fraction) for ammonium nitrate/sulfate in ambient air. Quenching of NH by the major combustion products does not limit the applicability of the detection method. Fluorescence from excited carbon atoms at 248 nm (1P 0 → 1S0) following photofragmentation measures particulate matter in a two-stroke gasoline engine and a four-stroke diesel engine. Fluorescence from CH (A2Delta → X 2pi, 431 nm) C2 (d3pig → a3piu, 468 nm) fragments is also observed. The atomic carbon fluorescence signal is proportional to the mass concentration of particles in the laser interrogation region. The 100-shot (1 second) detection limit for particles in the two-stroke gasoline engine exhaust is 0.5 ppb (volume fraction). The 100-shot detection limit for four-stroke diesel particulate matter is 0.2 ppb. Interferences from carbon monoxide and carbon dioxide are negligible. The ratios of atomic carbon, C2, and CH peaks provide information on the molecular forms of compounds condensed on or contained within the particles measured. The C/C2 signal ratio can be used to distinguish

  20. Thermodynamic measurements in a high pressure hydrogen-oxygen flame using Raman scattering from a broadband excimer laser

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy, Jr.

    1996-01-01

    Raman scattering is an inelastic molecular scattering process in which incident radiation is reemitted at a fixed change in frequency. Raman spectroscopy can be used to measure the number density and temperature of the irradiated species. The strength of the Raman signal is inversely proportional to the wavelength raised to the fourth power. Consequently, high signal to noise ratios are obtained by using ultraviolet (UV) excitation sources. Using UV sources for Raman Spectroscopy in flames is complicated by the fact that some of the primary constituents in hydrogen-oxygen combustion absorb and reemit light in the UV and these fluorescence processes interfere with the Raman signals. This problem has been handled in atmospheric pressure flames in some instances by using a narrowband tunable excimer laser as a source. This allows for detuning from absorption transitions and the elimination of interfering fluorescence signals at the Raman wavelengths. This approach works well in the atmospheric pressure flame; however, it has two important disadvantages. First, injection-locked narrowband tunable excimer lasers are very expensive. More importantly, however, is the fact that at the high pressures characteristic of rocket engine combustion chambers, the absorption transitions are broadened making it difficult to tune to a spectral location at which substantial absorption would not occur. The approach taken in this work is to separate the Raman signal from the fluorescence background by taking advantage of the fact that Raman signal has nonisotropic polarization characteristics while the fluorescence signals are unpolarized. Specifically, for scattering at right angles to the excitation beam path, the Raman signal is completely polarized. The Raman signal is separated from the fluorescence background by collecting both horizontally and vertically polarized signals separately. One of the polarizations has both the Raman signal and the fluorescence background while the

  1. N-type doping of Ge by As implantation and excimer laser annealing

    SciTech Connect

    Milazzo, R.; Napolitani, E. De Salvador, D.; Mastromatteo, M.; Carnera, A.; Impellizzeri, G.; Boninelli, S.; Priolo, F.; Privitera, V.; Fisicaro, G.; Italia, M.; La Magna, A.; Cuscunà, M.; Fortunato, G.

    2014-02-07

    The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 × 10{sup 19} cm{sup −3}) have been studied, both experimentally and theoretically, after excimer laser annealing (λ = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 × 10{sup 20} cm{sup −3}, which represents a new record for the As-doped Ge system.

  2. CAD/CAM interface design of excimer laser micro-processing system

    NASA Astrophysics Data System (ADS)

    Jing, Liang; Chen, Tao; Zuo, Tiechuan

    2005-12-01

    Recently CAD/CAM technology has been gradually used in the field of laser processing. The excimer laser micro-processing system just identified G instruction before CAD/CAM interface was designed. However the course of designing a part with G instruction for users is too hard. The efficiency is low and probability of making errors is high. By secondary development technology of AutoCAD with Visual Basic, an application was developed to pick-up each entity's information in graph and convert them to each entity's processing parameters. Also an additional function was added into former controlling software to identify these processing parameters of each entity and realize continue processing of graphic. Based on the above CAD/CAM interface, Users can design a part in AutoCAD instead of using G instruction. The period of designing a part is sharply shortened. This new way of design greatly guarantees the processing parameters of the part is right and exclusive. The processing of complex novel bio-chip has been realized by this new function.

  3. 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.

  4. Adhesion strength measurements of excimer-laser-treated PTFE surfaces using liquid photoreagents

    NASA Astrophysics Data System (ADS)

    Hopp, Bela; Smausz, Tomi; Kresz, Norbert; Ignacz, Ferenc

    2003-04-01

    The most known feature of polytetrafluoroethylene (PTFE) is its adhesion behavior: it is hydrophobic and oleophobic at the same time. This can cause serious problems and obstacles during the surface treatment and fixing of PTFE objects. During our experiments Teflon films were irradiated by an ArF excimer laser beam in presence of liquid photoreagents containing amine groups (aminoethanol, 1,2-diaminoethane, triethylene-tetramine). In consequence of the treatment the adhesion of the modified surfaces significantly increased, the samples could be glued and moistened. The adhesion strength of the glued surfaces was measured in the function of the applied laser fluence. The adhesion strength increased drastically between 0 - 1 mJ/cm2 and showed saturation above 1 mJ/cm2 at approximately 5 - 9 MPa values depending on the applied photoreagents. On the basis of our experiments it was found that the treatment with triethylene-tetramine was the most effective. The surface chemical modifications of the treated Teflon samples can be due to the incorporation of amine groups into the surface layer.

  5. Direct immobilization of biotin on the micro-patterned PEN foil treated by excimer laser.

    PubMed

    Štofik, Marcel; Semerádtová, Alena; Malý, Jan; Kolská, Zdeňka; Neděla, Oldřich; Wrobel, Dominika; Slepička, Petr

    2015-04-01

    Polymers with functionalized surfaces have attracted a lot of attention in the last few years. Due to the progress in the techniques of polymer micro-patterning, miniaturized bioanalytical assays and biocompatible devices can be developed. In the presented work, we performed surface modification of polyethylene naphthalate (PEN) foil by an excimer laser beam through a photolithographic contact mask. The aim was to fabricate micro-patterned areas with surface functional groups available for localized covalent immobilization of biotin. It was found out that depending on the properties of the laser scans, a polymer surface exhibits different degrees of modification and as a consequence, different degrees of surface biotinylation can be achieved. Several affinity tests with optical detection of fluorescently labeled streptavidin were successfully performed on biotinylated micro-patterns of a PEN foil. The polymer surface properties were also evaluated by electrokinetic analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results have shown that PEN foils can be considered suitable substrates for construction of micro-patterned bioanalytical affinity assays.

  6. Microhollow cathode discharge excimer light sources

    SciTech Connect

    El-Habachi, A.; Moselhy, M.; El-Dakroury, A.; Schoenbach, K.H.

    1999-07-01

    Microhollow Cathode discharges are non-equilibrium, high pressure, direct current discharges. By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values in the sub millimeter range the authors were able to operate discharges in argon and xenon in a direct current mode up to atmospheric pressure. They have shown that these discharges are intense source of xenon and argon excimer radiation peaking at wavelengths of 172 nm and 130 nm, respectively. Spatially resolved measurements of the excimer source in xenon have been performed. The source was found to be cylindrical along the axis of the electrodes. Its radius increases with current and decreases with pressure. Stacking the discharges, operating them in series, holds the promise for the generation of a laser medium with sufficient length to provide the required threshold gain for a dc excimer laser. Experimental studies of the gain of the plasma column in microhollow cathode discharges are underway. Excimer efficiencies, defined as the ratio of optical to electrical power, of 6% to 9% have been achieved. Further increase of the efficiency seems to be possible; according to the modeling results, efficiencies of 30% to 40% may be obtainable. The effect of various parameters such as electrode geometry, gas flow and pulsed versus cw operation on the excimer efficiency is being studied with the goal to optimize the discharge.

  7. Effect of the excimer laser irradiation on sol-gel derived tungsten-titanium dioxide thin films

    NASA Astrophysics Data System (ADS)

    Joya, Yasir F.; Liu, Zhu

    2011-01-01

    A novel technique based on the excimer laser induced crystallization and modification of TiO2 thin films is being reported. W+6 ions loaded TiO2 (WTO) precursor films were prepared by a modified sol-gel method and spin-coated onto microscopic glass slides. Pulsed KrF (248 nm, 13 ns) excimer laser was used to irradiate the WTO amorphous films at various laser parameters. Mesoporous and nanostructured films consisting of anatase and rutile were obtained after laser irradiation at room temperature. The effect of varying W+6 ions concentrations on structural and optical properties the WTO films was analyzed by X-ray diffraction, field-emission scanning electron microscope, UV-Vis spectrophotometer and transmission electron microscope before and after laser treatment. Films irradiated for 10 pulses at 65-75 mJ/cm2 laser fluence, exhibited anatase whereas higher parameters promoted the formation of rutile. XPS results revealed WO3 along with minor proportion of WO2 compounds after laser irradiation. Photo-absorbance of the WTO films was increased with increase in W+6 ions concentration in the film. TEM results exhibited a crystallite size of 15 nm which was confirmed from SEM results as well.

  8. Optical spectroscopy study of pulsed excimer laser generated plasma from CuO

    SciTech Connect

    Adhi, K.P.; Kale, S.; Padhye, Y.; Limaye, A.V.; Ogale, S.B.

    1995-12-15

    Optical emissions from pulsed excimer laser induced plasma emanating from CuO target are studied by an Optical Multichannel Analyzer system in the context of its implications for thin film growth by Pulsed Laser Deposition. The plasma is generated in four different ambients viz. hydrogen, helium, oxygen (pressure of 100 mTorr in each case) and vacuum (2 {times} 10{sup {minus}5} Torr) at different energy densities from 1 to 3.5 J/cm{sup 2}. The plasma constituents and their evolution in the growth space (i.e. at a distance of 1.5 cm from the target) has been studied. Various transitions corresponding to Cu(I), H(I), Cu(II) and O(II) are observed. The observation of strong transitions due to O(II) in the plasma formed in vacuum, hydrogen and helium suggests significant degree of ionization of atoms via molecular splitting and inverse Bremsstrahlung process during early plasma formation. The persistence of ionicity in the plasma can be attributed to long recombination lifetimes for the specific conditions used. In the case of ablation in oxygen ambient a very significant and remarkably selective enhancement of the copper vapor lasing transition at 510.5 nm is observed which brings out the role of oxygen molecules in sustaining the radiation trapping condition. The changes in the concentrations of neutrals and ions are a function of the laser energy density are also examined. It is argued that impingement of ions/atoms in an excited state on the growing surface can potentially lead to localized energy deposition via non-radiative deexcitation resulting into enhancement of film quality and density.

  9. Excimer Laser Phototherapeutic Keratectomy for the Treatment of Clinically Presumed Fungal Keratitis

    PubMed Central

    Li, Liang-Mao; Zhao, Li-Quan; Qu, Ling-Hui; Li, Peng

    2014-01-01

    This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK) for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%). The mean ablation depth was 114.39 ± 45.51 μm and diameter of ablation was 4.06 ± 1.07 mm. The mean time for healing of the epithelial defect was 8.8 ± 5.6 days. Thirty-four eyes (82.9%) showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8%) still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully. PMID:24891945

  10. Ruthenium Grubbs' catalyst nanostructures grown by UV-excimer-laser ablation for self-healing applications

    NASA Astrophysics Data System (ADS)

    Aïssa, B.; Nechache, R.; Haddad, E.; Jamroz, W.; Merle, P. G.; Rosei, F.

    2012-10-01

    A self healing composite material consisting of 5-Ethylidene-2-Norbornene (5E2N) monomer reacted with Ruthenium Grubbs' Catalyst (RGC) was prepared. First, the kinetics of the 5E2N ring opening metathesis polymerization (ROMP) reaction RGC was studied as a function of temperature. We show that the polymerization reaction is still effective in a large temperature range (-15 to 45 °C), occurring at short time scales (less than 1 min at 40 °C). Second, the amount of RGC required for ROMP reaction significantly decreased through its nanostructuration by means of a UV-excimer laser ablation process. RGC nanostructures of few nanometers in size where successfully obtained directly on silicon substrates. The X-ray photoelectron spectroscopy data strongly suggest that the RGC still keep its original stoichiometry after nanostructuration. More importantly, the associated ROMP reaction was successfully achieved at an extreme low RGC concentration equivalent to (11.16 ± 1.28) × 10-4 Vol.%, occurring at very short time reaction. This approach opens new prospects for using healing agent nanocomposite materials for self-repair functionality, thereby obtaining a higher catalytic efficiency per unit mass.

  11. Post-growth annealing of germanium-tin alloys using pulsed excimer laser

    SciTech Connect

    Wang, Lanxiang; Wang, Wei; Zhou, Qian; Yeo, Yee-Chia; Pan, Jisheng; Zhang, Zheng; Tok, Eng Soon

    2015-07-14

    We investigate the impact of pulsed excimer laser anneal on fully strained germanium-tin alloys (Ge{sub 1−x}Sn{sub x}) epitaxially grown on Ge substrate by molecular beam epitaxy. Using atomic force microscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, the morphological and compositional evolution of Ge{sub 1−x}Sn{sub x} with Sn content up to 17% after annealing using various conditions is studied. Ge{sub 0.83}Sn{sub 0.17} samples annealed at 80 mJ/cm{sup 2} or 150 mJ/cm{sup 2} have no observable changes with respect to the as-grown sample. However, Ge{sub 0.83}Sn{sub 0.17} samples annealed at 250 mJ/cm{sup 2} or 300 mJ/cm{sup 2} have Sn-rich islands on the surface, which is due to Sn segregation in the compressively strained epitaxial film. For Ge{sub 0.89}Sn{sub 0.11}, significant Sn redistribution occurs only when annealed at 300 mJ/cm{sup 2}, indicating that it has better thermal stability than Ge{sub 0.83}Sn{sub 0.17}. A mechanism is proposed to explain the formation of Sn-rich islands and Sn-depleted regions.

  12. Multilevel diffractive optical element manufacture by excimer laser ablation and halftone masks

    NASA Astrophysics Data System (ADS)

    Quentel, Francois; Fieret, Jim; Holmes, Andrew S.; Paineau, Sylvain

    2001-06-01

    A novel method is presented to manufacture multilevel diffractive optical elements (DOEs) in polymer by single- step KrF excimer laser ablation using a halftone mask. The DOEs have a typical pixel dimension of 5 micrometers and are up to 512 by 512 pixels in size. The DOEs presented are Fresnel lenses and Fourier computer generated holograms, calculated by means of a conventional iterative Fourier transform algorithm. The halftone mask is built up as an array of 5 micrometers -square pixels, each containing a rectangular or L- shaped window on an opaque background. The mask is imaged onto the polymer with a 5x, 0.13 NA reduction lens. The pixels are not resolved by the lens, so they behave simply as attenuators, allowing spatial variation of the ablation rate via the window size. The advantages of halftone mask technology over other methods, such as pixel-by-pixel ablation and multi-mask overlay, are that it is very fast regardless of DOE size, and that no high-precision motion stages and alignment are required. The challenges are that the halftone mask is specific to the etch curve of the polymer used, that precise calibration of each grey-level is required, and that the halftone mask must be calculated specifically for the imaging lens used. This paper describes the design procedures for multilevel DOEs and halftone masks, the calibration of the various levels, and some preliminary DOE test results.

  13. Tribology and mechanical properties of excimer laser-processed Ti--Si{sub 3}N{sub 4} surfaces

    SciTech Connect

    Jervis, T.R.; Hirvonen, J.; Nastasi, M.; Kung, H.

    1995-08-01

    Titanium films were mixed, using excimer laser radiation, into the surface of bulk Si{sub 3}N{sub 4} materials. The tribological and mechanical properties of these surfaces were then evaluated using pin-on-disk and nanoindenter techniques, respectively. Reduced friction and a change in the wear mechanism that resulted in a more benign failure mode were observed. These results are interpreted as resulting from the establishment of a transfer film, changes in the compliance of the surface which reduces instantaneous stresses in the surface, and toughening of the surface, all results of the laser process.

  14. Results of excimer laser photorefractive keratectomy for the correction of myopia at Cedars-Sinai Medical Center: 1993

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; Nesburn, Anthony B.; Warren, Cathy; Macy, Jonathan I.; Papaioannou, Thanassis; Hofbauer, John; Berlin, Michael S.

    1994-06-01

    This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy (PRK) on 240 eyes of 161 patients. With constant laser emission parameters, nitrogen (N2) flow across the cornea was used on 79 eyes while 161 eyes had no N2 flow. 74 eyes were operated on without fixation with a suction ring. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical Diclofenac or Ketorolac, and a therapeutic soft contact lens in 163 eyes. Follow up ranged from 1 month (206 eyes) to 36 months (10 eyes).

  15. Formation of amorphous Ti alloy layers by excimer laser mixing of Ti on AISI 304 stainless-steel surfaces

    NASA Astrophysics Data System (ADS)

    Jervis, T. R.; Nastasi, M.; Zocco, T. G.; Martin, J. A.

    1988-07-01

    We used excimer laser radiation at 308 nm to mix thin layers of Ti into AISI 304 stainless steel. Different numbers of shots at a fluence about twice the threshold for melting varied the amount of mixing. When mixing is sufficiently complete, an amorphous surface layer is formed with Ti substituting for Fe on a one-to-one basis in the alloy. The laser mixing process, unlike Ti ion implantation, does not result in high incorporation of C in the processed layer, although some C from surface and interface contamination is incorporated into the surface layer.

  16. Computation of time-dependent transition probabilities in excimer molecules induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Petsalakis, Ioannis D.; Mercouris, Theodoros; Nicolaides, Cleanthes A.

    1994-12-01

    We have computed the time-dependent probabilities of exciting and deexciting the bound states of the excimer molecules NeH, ArH and HeF, via the interaction of these systems with femtosecond laser pulses. The method involves the expansion of the time-dependent wavefunction in terms of stationary states with time-dependent coefficients and complex energies, whose imaginary parts represent the lifetimes of the collision complex on the initial repulsive ground state and of the excited states which are coupled by the field. The resulting system of differential equations is solved by a Taylor series expansion method. We have studied the efficiency of laser-induced molecular formation (LIMP) from the ground repulsive surfaces as a function of frequency and intensity, for trapezoidal pulses. Given the shortness of the pulse and the characteristics of the spectra of these molecules, for reasons of economy the bulk of the calculations was carried out in a 'frozen nuclei' approximation. Additional calculations for NeH, using a wavepacket representation of the initial state on the repulsive curve produced similar results as regards the possibility of LIMF. Additional information has been obtained regarding transitions among excited states. For example, starting the photoreaction in HeF from the first excited repulsive state 1 2Π with a pulse frequency of 4 eV allows an experimentally verifiable probability of obtaining bound-continuum emission at about 1320 Å (9.4 eV). For resonance conditions, the probabilities are appreciable during the pulse and go through maxima as a function of intensity of the order of 10 11 W/cm 2-10 14W/cm 2.

  17. Outcomes of excimer laser enhancements in pseudophakic patients with multifocal intraocular lens

    PubMed Central

    Schallhorn, Steven C; Venter, Jan A; Teenan, David; Schallhorn, Julie M; Hettinger, Keith A; Hannan, Stephen J; Pelouskova, Martina

    2016-01-01

    Purpose The aim of this study was to assess visual and refractive outcomes of laser vision correction (LVC) to correct residual refraction after multifocal intraocular lens (IOL) implantation. Patients and methods In this retrospective study, 782 eyes that underwent LVC to correct unintended ametropia after multifocal IOL implantation were evaluated. Of all multifocal lenses implanted during primary procedure, 98.7% were refractive and 1.3% had a diffractive design. All eyes were treated with VISX STAR S4 IR excimer laser using a convectional ablation profile. Refractive outcomes, visual acuities, patient satisfaction, and quality of life were evaluated at the last available visit. Results The mean time between enhancement and last visit was 6.3±4.4 months. Manifest spherical equivalent changed from −0.02±0.83 D (−3.38 D to +2.25 D) pre-enhancement to 0.00±0.34 D (−1.38 D to +1.25 D) post-enhancement. At the last follow-up, the percentage of eyes within 0.50 D and 1.00 D of emmetropia was 90.4% and 99.5%, respectively. Of all eyes, 74.9% achieved monocular uncorrected distance visual acuity 20/20 or better. The mean corrected distance visual acuity remained the same before (−0.04±0.06 logMAR [logarithm of the minimum angle of resolution]) and after LVC procedure (−0.04±0.07 logMAR; P=0.70). There was a slight improvement in visual phenomena (starburst, halo, glare, ghosting/double vision) following the enhancement. No sight-threatening complications related to LVC occurred in this study. Conclusion LVC in pseudophakic patients with multifocal IOL was safe, effective, and predictable in a large cohort of patients. PMID:27175059

  18. Interstitial trapping in Fe-implanted Al after excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Swanson, M. L.; Howe, L. M.; Quenneville, A. F.; Nilson, J. A.

    1983-12-01

    Laser annealing was used to create a supersaturated solution of Fe atoms in Al, in order that channeling measurements of self-interstitial trapping could be made. A single crystal of Al was implanted with 40 keV 56Fe to a fluence of 1.6×10 15 ions cm -2. A 4 mm diameter region of the crystal was annealed in air with a XeCl excimer laser at an energy density of ˜ 6 J cm -2. This treatment produced a relatively perfect crystal; the normalized yield of 1 MeV He + ions from near-surface Al atoms for <110> alignment at 35 K was 0.04. The Fe atoms were ˜ 90% substitutional, corresponding to a solubility of ˜ 0.3 at%, as compared with only ˜ 0.02 at% obtained by a water quench from 873 K. The crystal was then irradiated with 1 MeV He + at 70 K to a fluence of ˜ 5 × 10 15 ions cm -2, in order to create mobile Al self-interstitial atoms which could be trapped by the Fe atoms. A channeling analysis of the resulting displacement of Fe atoms indicated that they trapped self-interstitials strongly, as observed for other small solute atoms in Al. As no flux peaking in the backscattering yield from Fe atoms was observed for a <110> angular scan, the results indicate that the trapping configuration may differ from that observed for Cr, Mn or Cu solute atoms in Al. The trapped interstitials were annihilated by vacancy migration near 200 K.

  19. Nickel-affected silicon crystallization and silicidation on polyimide by multipulse excimer laser annealing

    SciTech Connect

    Alberti, A.; La Magna, A.; Spinella, C.; Privitera, V.; Cuscuna, M.; Fortunato, G.

    2010-12-15

    Nickel enhanced amorphous Si crystallization and silicidation on polyimide were studied during multipulse excimer laser annealing (ELA) from submelting to melting conditions. A {approx}8 nm thick Ni film was deposited on a 100 nm thick {alpha}-Si layer at {approx}70 deg. C in order to promote partial nickel diffusion into silicon. In the submelting regime, Ni atoms distributed during deposition in {alpha}-Si and the thermal gradient due to the presence of the plastic substrate were crucial to induce low fluence ({>=}0.08 J/cm{sup 2}) Si crystallization to a depth which is strictly related to the starting Ni profile. {Alpha}morphous-Si crystallization is not expected on pure Si at those low fluences. Additional pulses at higher fluences do not modify the double poly-Si/{alpha}-Si structure until melting conditions are reached. At a threshold of {approx}0.2 J/cm{sup 2}, melting was induced simultaneously in the polycrystalline layer as well as in the residual {alpha}-Si due to a thermal gradient of {approx}200 deg. C. Further increasing the laser fluence causes the poly-Si layer to be progressively melted to a depth which is proportional to the energy density used. As a consequence of the complete Si melting, columnar poly-Si grains are formed above 0.3 J/cm{sup 2}. For all fluences, a continuous NiSi{sub 2} layer is formed at the surface which fills the large Si grain boundaries, with the beneficial effect of flattening the poly-Si surface. The results would open the perspective of integrating Ni-silicide layers as metallic contacts on Si during {alpha}-Si-crystallization by ELA on plastic substrate.

  20. The effect of microarc oxidation and excimer laser processing on the microstructure and corrosion resistance of Zr-1Nb alloy

    NASA Astrophysics Data System (ADS)

    Yang, Jiaoxi; Wang, Xin; Wen, Qiang; Wang, Xibing; Wang, Rongshan; Zhang, Yanwei; Xue, Wenbin

    2015-12-01

    The main purpose of this research was to investigate the effect of microarc oxidation (MAO) and excimer laser processing on the corrosion resistance of Zr-1Nb alloy in service environment. The pre-oxide film was fabricated on the surface of Zr-1Nb cladding tubes by MAO processing, and then subjected to KrF excimer laser irradiation. The surface morphology of the pre-oxide film was observed using a scanning electron microscope; phase compositions and quantities were determined using an X-ray diffraction; surface roughness was determined using a profilometer; and thermal expansion coefficient was measured using a dilatometer. Autoclave experiments were conducted for 94 days in an aqueous condition of 360 °C under 18.6 MPa in 0.01 mol/L LiOH solutions. The results showed that MAO + laser treatment resulted in a significant increase in the corrosion resistance of Zr-1Nb cladding tubes at high temperatures, because laser melting and etching could lead to a reduction in surface roughness and an increase in compactness of the pre-oxide film, and laser processing could promote the transformation of m-ZrO2 phase to t-ZrO2 phase. The best corrosion resistance was obtained when the pulse energy was 500 mJ, scanning speed was 0.13 mm/s, and pulse number was 2400.

  1. A repetitively pulsed xenon chloride excimer laser with all ferrite magnetic cores (AFMC) based all solid state exciter

    NASA Astrophysics Data System (ADS)

    Benerji, N. S.; Varshnay, N. K.; Ghodke, D. V.; Singh, A.

    2016-10-01

    Performance of repetitively pulsed xenon chloride excimer laser (λ~308 nm) with solid state pulser consisting of magnetic pulse compression circuit (MPC) using all ferrite magnetic cores (AFMC) is reported. Laser system suitable for 100 Hz operation with inbuilt pre-ionizer, compact gas circulation and cooling has been developed and presented. In this configuration, high voltage pulses of ~8 μs duration are compressed to ~100 ns by magnetic pulse compression circuit with overall compression factor of ~80. Pulse energy of ~18 J stored in the primary capacitor is transferred to the laser head with an efficiency of ~85% compared to ~70% that is normally achieved in such configurations using annealed met-glass core. This is a significant improvement of about 21%. Maximum output laser pulse energy of ~100 mJ was achieved at repetition rate of 100 Hz with a typical pulse to pulse energy stability of ±5% and laser pulse energy of 150 mJ was generated at low rep-rate of ~40 Hz. This exciter uses a low current and low voltage solid state switch (SCR) that replaces high voltage and high current switch i. e, thyratron completely. The use of solid state exciter in turn reduces electromagnetic interference (EMI) effects particularly in excimer lasers where high EMI is present due to high di/dt. The laser is focused on a thin copper sheet for generation of micro-hole and the SEM image of the generated micro hole shows the energy stability of the laser at high repetition rate operation. Nearly homogeneous, regular and well developed xenon chloride (XeCl) laser beam spot was achieved using the laser.

  2. Corneal haze induced by excimer laser photoablation in rabbits is reduced by preserved human amniotic membrane graft

    NASA Astrophysics Data System (ADS)

    Wang, Ming X.; Gray, Trevor; Prabhasawat, Pinnita; Ma, Xiong; Culbertson, William; Forster, Richard; Hanna, Khalil; Tseng, Scheffer C. G.

    1998-06-01

    We conducted a study to determine if preserved human amniotic membrane can reduce corneal haze induced by excimer laser photoablation. Excimer photoablation was performed bilaterally on 40 New Zealand white rabbits with a 6 mm ablation zone and 120 micrometer depth (PTK) using the VISX Star. One eye was randomly covered with a preserved human amniotic membrane and secured using four interrupted 10 - 0 nylon sutures; the other eye served as control. The amniotic membranes were removed at one week, and the corneal haze was graded with a slit-lamp biomicroscopy by three masked corneal specialists (WC, KH and RF) biweekly for the ensuing 12 weeks. Histology and in situ TUNEL staining (for fragmented DNA as an index for apoptosis) was performed at days 1, 3 and 7 and at 12 weeks. One week after excimer photoablation, the amniotic membrane-covered corneas showed more anterior stromal edema, which resolved at the second week. A consistent grading of organized reticular corneal haze was noted among the three masked observers. Such corneal haze peaked at the seventh week in both groups. The amniotic membrane-covered group showed statistically significant less corneal haze (0.50 plus or minus 0.15) than the control groups (1.25 plus or minus 0.35) (p less than 0.001). The amniotic membrane-covered corneas had less inflammatory response at days 1 and 3, showing nearly nil DNA fragmentation on keratocytes on the ablated anterior stromal and less stromal fibroblast activation. There is less altered epithelial cell morphology and less epithelial hyperplasia at 1 week in these amniotic membrane-treated eyes. We concluded from this study that amniotic membrane matrix is effective in reducing corneal haze induced by excimer photoablation in rabbits and may have clinical applications.

  3. Surface morphology and subsurface damaged layer of various glasses machined by 193-nm ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Liao, Yunn-shiuan; Chen, Ying-Tung; Chao, Choung-Lii; Liu, Yih-Ming

    2005-01-01

    Owing to the high bonding energy, most of the glasses are removed by photo-thermal rather than photo-chemical effect when they are ablated by the 193 or 248nm excimer lasers. Typically, the machined surface is covered by re-deposited debris and the sub-surface, sometimes surface as well, is scattered with micro-cracks introduced by thermal stress generated during the process. This study aimed to investigate the nature and extent of the surface morphology and sub-surface damaged (SSD) layer induced by the laser ablation. The effects of laser parameters such as fluence, shot number and repetition rate on the morphology and SSD were discussed. An ArF excimer laser (193 nm) was used in the present study to machine glasses such as soda-lime, Zerodur and BK-7. It is found that the melt ejection and debris deposition tend to pile up higher and become denser in structure under a higher energy density, repetition rate and shot number. There are thermal stress induced lateral cracks when the debris covered top layer is etched away. Higher fluence and repetition rate tend to generate more lateral and median cracks which propagate into the substrate. The changes of mechanical properties of the SSD layer were also investigated.

  4. Perspectives of using the 223-nm wavelength of the KrCl excimer laser for refractive surgery and for the treatment of some eye diseases

    NASA Astrophysics Data System (ADS)

    Bagayev, Sergei N.; Chernikh, Valery V.; Razhev, Alexander M.; Zhupikov, Andrey A.

    2000-06-01

    The new surgical UV ophthalmic laser system Medilex based on the KrCl (223 nm) excimer laser for refractive surgery was created. The comparative analysis of using the UV ophthalmic laser systems Medilex based on the ArF (193 nm) and the KrCl (223 nm) excimer lasers for the correction of refractive errors was performed. The system with the radiation wavelength of 223 nanometer of the KrCl excimer laser for refractive surgery was shown to have several medical and technical advantages over the system with the traditionally used radiation wavelength of 193 nanometer of the ArF excimer laser. In addition the use of the wavelength of 223 nanometer extends functional features of the system, allowing to make not only standard for this type systems surgical and therapeutic procedures but also to treat such ocular diseases as the glaucoma and herpetic keratities. For the UV ophthalmic laser systems Medilex three variations of the beam delivery system including special rotating masks and different beam homogenize systems were developed. All created beam delivery systems are able to make the correction of myopia, hyperopia, astigmatism and myopic or hyperopic astigmatism and may be used for therapeutic procedures. The results of the initial treatments of refractive error corrections using the UV ophthalmic laser systems Medilex for both photorefractive keratectomy (PRK) and LASIK procedures are presented.

  5. Near surface chemistry and corrosion behavior of excimer laser surface-melted AISI type 304 stainless steel

    SciTech Connect

    Baer, D.R.; Frydrych, D.J.; Jervis, T.R.

    1988-05-01

    The effects of excimer laser surface melting on the near-surface chemistry, and corrosion behavior of AISI 304 stainless steel have been examined as a function of total energy deposited on the specimen. The surface chemistry resulting from the laser treatments has been examined using Auger electron spectroscopy. Electrochemical methods were used to monitor the corrosion behavior of the specimens in deaerated 0.1 M NaCl. Electron microscopy was used to characterize the extent of local corrosion of the specimens. Laser treatment was observed to increase the chromium concentration of the surface oxide and to reduce the number of pits. Two types of pits were observed on untreated material, but only one type of pit occurred after laser treatment. 7 refs., 5 figs.

  6. Laser satellite power systems

    SciTech Connect

    Walbridge, E.W.

    1980-01-01

    A laser satellite power system (SPS) converts solar power captured by earth-orbiting satellites into electrical power on the earth's surface, the satellite-to-ground transmission of power being effected by laser beam. The laser SPS may be an alternative to the microwave SPS. Microwaves easily penetrate clouds while laser radiation does not. Although there is this major disadvantage to a laser SPS, that system has four important advantages over the microwave alternative: (1) land requirements are much less, (2) radiation levels are low outside the laser ground stations, (3) laser beam sidelobes are not expected to interfere with electromagnetic systems, and (4) the laser system lends itself to small-scale demonstration. After describing lasers and how they work, the report discusses the five lasers that are candidates for application in a laser SPS: electric discharge lasers, direct and indirect solar pumped lasers, free electron lasers, and closed-cycle chemical lasers. The Lockheed laser SPS is examined in some detail. To determine whether a laser SPS will be worthy of future deployment, its capabilities need to be better understood and its attractiveness relative to other electric power options better assessed. First priority should be given to potential program stoppers, e.g., beam attenuation by clouds. If investigation shows these potential program stoppers to be resolvable, further research should investigate lasers that are particularly promising for SPS application.

  7. Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

    SciTech Connect

    Geohegan, D.B.

    1994-09-01

    Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

  8. Excimer laser annealing to fabricate low cost solar cells. Quarterly technical report No. 1, 26 March-30 June 1984

    SciTech Connect

    Not Available

    1984-07-01

    The objective of this research 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 during the first quarter of this program 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 described by JPL. 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. The technical goal of this research is to develop an optimized PELA process compatible with commercial production, and to demonstrate increased cell efficiency with sufficient product for adequate statistical analysis. During the first quarter of this program 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. Preliminary results showed that the PELA processed cells had overall efficiencies comparable to furnace annealed ion implanted controls, and that texture-etched material requires lower fluence for annealing than polished silicon. Process optimization will be carried out in the second quarter.

  9. Determination of flue gas alkali concentrations in fluidized-bed coal combustion by excimer-laser-induced fragmentation fluorescence

    SciTech Connect

    Hartinger, K.T.; Monkhouse, P.B.; Wolfrum, J.; Baumann, H.; Bonn, B.

    1994-12-31

    Gas-phase sodium concentrations were measured for the first time in situ in the flue gas of a fluidized-bed reactor by the excimer-laser-induced fragmentation fluorescence (ELIF) technique. This method involves using ArF-excimer laser light at 193 nm to simultaneously photodissociate the alkali compounds of interest and excite electronically the alkali atoms formed. The resulting fluorescence from Na (3{sup 2}P) atoms can he readily detected at 589 nm. Measured signals were converted to absolute concentrations using a calibration system that monitors alkali compounds under known conditions of temperature, pressure, and composition and rising the same optical setup as at the reactor. Several different coals were investigated under a specific set of reactor conditions at total pressures close to 1 bar. Sodium concentrations ranging from the sub-ppb region to 20 ppb were obtained, and a detection limit for sodium of 0.1 ppb under the present conditions was estimated. Over the course of the reactor program, contrasting concentration histories were observed for the two lignites and the hard coal investigated. In particular, significantly higher sodium concentrations were found for the hard coal, consistent with both the higher chlorine and sodium contents determined in the corresponding coal analysis.

  10. Laser power transmission

    NASA Technical Reports Server (NTRS)

    Conway, Edmund J.

    1992-01-01

    An overview of previous studies related to laser power transmission is presented. Particular attention is given to the use of solar pumped lasers for space power applications. Three general laser mechanisms are addressed: photodissociation lasing driven by sunlight, photoexcitation lasing driven directly by sunlight, and photoexcitation lasing driven by thermal radiation.

  11. Transformation of medical grade silicone rubber under Nd:YAG and excimer laser irradiation: First step towards a new miniaturized nerve electrode fabrication process

    NASA Astrophysics Data System (ADS)

    Dupas-Bruzek, C.; Robbe, O.; Addad, A.; Turrell, S.; Derozier, D.

    2009-08-01

    Medical grade silicone rubber, poly-dimethylsiloxane (PDMS) is a widely used biomaterial. Like for many polymers, its surface can be modified in order to change one or several of its properties which further allow this surface to be functionalized. Laser-induced surface modification of PDMS under ambient conditions is an easy and powerful method for the surface modification of PDMS without altering its bulk properties. In particular, we profit from both UV laser inducing surface modification and of UV laser micromachining to develop a first part of a new process aiming at increasing the number of contacts and tracks within the same electrode surface to improve the nerve selectivity of implantable self sizing spiral cuff electrodes. The second and last part of the process is to further immerse the engraved electrode in an autocatalytic Pt bath leading in a selective Pt metallization of the laser irradiated tracks and contacts and thus to a functionalized PDMS surface. In the present work, we describe the different physical and chemical transformations of a medical grade PDMS as a function of the UV laser and of the irradiation conditions used. We show that the ablation depths, chemical composition, structure and morphology vary with (i) the laser wavelength (using an excimer laser at 248 nm and a frequency-quadrupled Nd:YAG laser at 266 nm), (ii) the conditions of irradiation and (iii) the pulse duration. These different modified properties are expected to have a strong influence on the nucleation and growth rates of platinum which govern the adhesion and the thickness of the Pt layer on the electrodes and thus the DC resistance of tracks.

  12. Focused excimer laser initiated, radio frequency sustained high pressure air plasmas

    SciTech Connect

    Giar, Ryan; Scharer, John

    2011-11-15

    Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 300 mJ, 15 MW high power laser radiation inside a 6 cm diameter helical radio frequency (RF) coil are presented. Quantum resonant multi-photon ionization (REMPI) and collisional cascade laser ionization processes are exploited that have been shown to produce high-density (n{sub e} {approx} 7 x 10{sup 16}/cm{sup 3}) cylindrical seed plasmas at 760 Torr. Air breakdown in lower pressures (from 7-22 Torr), where REMPI is the dominant laser ionization process, is investigated using an UV 18 cm focal length lens, resulting in a laser flux of 5.5 GW/cm{sup 2} at the focal spot. The focused laser power absorption and associated shock wave produce seed plasmas for sustainment by the RF (5 kW incident power, 1.5 s) pulse. Measurements of the helical RF antenna load impedance in the inductive and capacitive coupling regimes are obtained by measuring the loaded antenna reflection coefficient. A 105 GHz interferometer is used to measure the plasma electron density and collision frequency. Spectroscopic measurements of the plasma and comparison with the SPECAIR code are made to determine translational, rotational, and vibrational neutral temperatures and the associated neutral gas temperature. From this and the associated measurement of the gas pressure the electron temperature is obtained. Experiments show that the laser-formed seed plasma allows RF sustainment at higher initial air pressures (up to 22 Torr) than that obtained via RF-only initiation (<18 Torr) by means of a 0.3 J UV laser pulse.

  13. A Comparison of Excimer Laser Microprobe (U-Th)/He and Conventional Laser-Heating (U-Th)/He Thermochronometry

    NASA Astrophysics Data System (ADS)

    Boyce, J. W.; Hodges, K. V.; Olszewski, W. J.; Jercinovic, M. J.; Carpenter, B.; Reiners, P. W.

    2005-12-01

    Recent advances in Excimer laser ablation (U-Th)/He thermochronology (ExLA-(U-Th)/He) of monazite have demonstrated the potential of the technique with regard to generating precise cooling age information while dealing with parent element zoning, inclusions and avoiding the alpha ejection correction and the uncertainty therein [1]. ExLA-(U-Th)/He age determinations consist of three independent measurements: 1) Moles of He, 2) Ablated volume, and 3) Parent element (U, Th, Sm) concentrations. After samples are polished, an Excimer laser is used to drill a 10-250 μm diameter hole in the surface, liberating radiogenic helium which is then quantified by isotope dilution. The volume of the hole is then measured by an ADE-Phase Shift MicroXAM vertical scanning interferometer, allowing us to calculate He concentration. U, Th, and Sm concentrations are obtained (in the case of monazite), by electron microprobe analysis (either before or after helium analysis). While the precision of the technique has been adequately demonstrated on monazites as young as ~700 ka [1,2], the question of accuracy has to this point been unanswered because of the lack of a suitable monazite (U-Th)/He standard amenable to conventional (U-Th)/He analysis for comparison. Typical natural monazites are very small and strongly zoned, resulting in large and poorly constrained alpha-recoil corrections, and therefore conventional (U-Th)/He ages with unacceptably large uncertainties. Eighteen ExLA-(U-Th)/He ages on a polished section of the centimeter-sized, gem-quality Brazilian monazite MOM1 yield an error-weighted mean of 447.4 ± 3.4 Ma (0.75% at two standard errors from the mean or 2SE). Ten additional 25 μm spot analyses on a small fragment of a second crystal (MOM3) result a similar weighted mean age, albeit with more scatter, of 454.6 ± 8.9 Ma (2.0% at 2SE). Taken together, the 28 ExLA-(U-Th)/He analyses on the two crystals can be used to calculate one age of 450.4 ± 3.9 Ma (0.86% at 2SE). The

  14. AFM study of excimer laser patterning of block-copolymer: Creation of ordered hierarchical, hybrid, or recessed structures

    NASA Astrophysics Data System (ADS)

    Švanda, Jan; Siegel, Jakub; Švorčík, Vaclav; Lyutakov, Oleksiy

    2016-05-01

    We report fabrication of the varied range of hierarchical structures by combining bottom-up self-assembly of block copolymer poly(styrene-block-vinylpyridine) (PS-b-P4VP) with top-down excimer laser patterning method. Different procedures were tested, where laser treatment was applied before phase separation and after phase separation or phase separation and surface reconstruction. Laser treatment was performed using either polarized laser light with the aim to create periodical pattern on polymer surface or non-polarized light for preferential removing of polystyrene (PS) part from PS-b-P4VP. Additionally, dye was introduced into one part of block copolymer (P4VP) with the aim to modify its response to laser light. Resulting structures were analyzed by XPS, UV-vis and AFM techniques. Application of polarized laser light leads to creation of structures with hierarchical, recessed or hybrid geometries. Non-polarized laser beam allows pronouncing the block copolymer phase separated structure. Tuning the order of steps or individual step conditions enables the efficient reorientation of block-copolymer domain at large scale, fabrication of hierarchical, hybrid or recessed structures. The obtained structures can find potential applications in nanotechnology, photonics, plasmonics, information storage, optical devices, sensors and smart surfaces.

  15. Improvement of electrical performance of InGaZnO/HfSiO TFTs with 248-nm excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Huang, Hau-Yuan; Wang, Shui-Jinn; Wu, Chien-Hung; Lu, Chien-Yuan

    2014-09-01

    The influence of 248-nm KrF excimer laser annealing (ELA) with energy density between 0 and 400 mJ/cm2 on the electrical behavior of indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) is investigated. The experimental results show that the saturation mobility and subthreshold swing are improved from 12.4 cm2/Vs and 100 mV/dec without ELA to 17.8 cm2/Vs and 75 mV/dec, respectively, by applying a 300 mJ/cm2 laser pulse after the source/drain deposition, while maintaining an almost unchanged turn-off voltage. Such improvements are attributed to the increase in the oxygen vacancies and reduction in the bulk traps in the InGaZnO channel.

  16. Determination of the melting threshold of TiO{sub 2} thin films processed by excimer laser irradiation

    SciTech Connect

    Van Overschelde, O.; Delsate, T.; Snyders, R.

    2012-06-15

    Processing surfaces by laser needs an understanding of the mechanisms generated by irradiation. In this work, to gain understanding of the mechanisms occurring during irradiation of TiO{sub 2} thin films by means of KrF excimer laser, we have performed infrared time resolved reflectivity measurements. This experimental investigation revealed modifications of the heating/cooling cycle as a function of the fluence (F). These modifications start appearing for a fluence value of about {approx}0.25 J/cm{sup 2} which is associated with the melting threshold of the film. Additionally, we have solved numerically the heat equation of the system with specific boundary conditions. From these calculations, we have established the thermal history of the film during the 25 ns irradiation pulse. The data reveal that a part of the medium liquefies around a fluence of 0.23 J/cm{sup 2} in good agreement with the experimental data.

  17. ASE suppression of XeCl excimer laser MOPA system using UV electro-optical switch

    NASA Astrophysics Data System (ADS)

    Hu, Yun; Zhao, Xue-qing; Xue, Quan-xi; Wang, Da-hui; Zheng, Guo-xin; Hua, Heng-qi; Zhang, Yongsheng; Zhu, Yong-xiang; Xiao, Wei-wei; Wang, Li

    2013-05-01

    In high power eximer laser system, amplified spontaneous emission (ASE) decreases the signal contrast ratio severely, leads to waveform broadening and distortion, and impacts on accurate physical experiments. In this article, based on principle of short pulse generation by electro-optical (E-O) switch, a method for ASE suppression of laser amplifiers chain was established. A series of studies on UV electro-optical switches were carried out, and electro-optical (E-O) switches with high extinction ratio were developed. In the waveform clipping experiments of the first pre-amplifier, the extinction ratio of the single and cascaded dual E-O switch reaches 103 and 104 order of magnitude, the laser pulse signal contrast ratio was promoted to 105 and 106 level, respectively. In the experiments of single channel MOPA (Master Oscillator Power Amplifier system), the cascaded dual E-O switch was adopted to suppress ASE of the whole system, and a fine narrow pulse was obtained on the target surface, which gives out one effective solution to the problem of waveform amplification of the high power eximer laser system.

  18. KrF- and ArF-excimer-laser-induced absorption in silica glasses produced by melting synthetic silica powder

    SciTech Connect

    Kuzuu, Nobu; Sasaki, Toshiya; Kojima, Tatsuya; Tanaka, Jun-ichiro; Nakamura, Takayuki; Horikoshi, Hideharu

    2013-07-07

    KrF- and ArF-excimer-laser-induced absorption of silica glasses produced by electric melting and flame fusion of synthetic silica powder were investigated. The growth of KrF-laser-induced absorption was more gradual than that of ArF-laser-induced absorption. Induced absorption spectra exhibited a peak at about 5.8 eV, of which the position and width differed slightly among samples and laser species. Widths of ArF-laser-induced absorption spectra were wider than those of KrF-laser-induced spectra. KrF-laser-induced absorption is reproducible by two Gaussian absorption bands peaking at 5.80 eV with full width at half maximum (FWHM) of 0.62 eV and at 6.50 eV with FWHM of 0.74 eV. For reproduction of ArF-laser-induced absorption, Gaussian bands at 5.41 eV with FWHM of 0.62 eV was necessary in addition to components used for reproducing KrF-laser-induced absorption. Based on the discussion of the change of defect structures evaluated from change of absorption components, we proposed that the precursor of the 5.8-eV band ascribed to E Prime center ({identical_to}Si{center_dot}) is {identical_to}Si-H HO-Si{identical_to} structures formed by the reaction between strained Si-O-Si bonds and interstitial H{sub 2} molecules during the irradiation.

  19. Cataract Surgery combined with excimer laser trabeculotomy to lower intraocular pressure: effectiveness dependent on preoperative IOP

    PubMed Central

    2013-01-01

    Background Cataract surgery combined with excimer laser trabeculotomy (phaco-ELT) can reduce intraocular pressure (IOP). The aim of this study was to evaluate the effect of phaco-ELT on IOP in patients as a function of preoperative IOP. Methods Patients with open-angle glacuoma or ocular hypertension who received phaco-ELT between 01/2008 and 10/2009 were included. Patients were assigned based on preoperative IOP either to the study group (≤21 mmHg) or control group (>21 mmHg) in this IRB-approved, prospective, consecutive case series. Visual Acuity, IOP, and number of anti-glaucoma drugs (AGD) were recorded at baseline and 12 months after phaco-ELT. Any postoperative complications were also recorded. Results 64 eyes of 64 patients (76.5 ± 9.4 years) were included. Baseline IOP was 19.8 ± 5.3 mmHg (AGD 2.4 ± 1.1) for all eyes, 16.5 ± 2.9 mmHg (AGD 2.5 ± 1.0) for the study group, and 25.8 ± 2.9 mmHg (AGD 2.2 ± 1.4) for the control group. Across the two groups, IOP was reduced by 4.5 ± 5.9 mmHg (-23.0%, p < 0.001) and AGD by 0.9 ± 1.5 (-38.9%, p < 0.001). For the study group IOP was reduced by 1.9 ± 4.4 mmHg (-11. 5 %, p = 0.012) and AGD by 1.1 ± 1.4 (-42.9%, p < 0.001), and for the control group by 9.5 ± 5.4 mmHg (-36.6%, p < 0.001) and AGD by 0.7 ± 1.6 (-29.5%, p = 0.085). There were no serious postoperative complications such as endophthalmitis, significant hyphema, or a severe fibrinous reaction of the anterior chamber. Conclusions IOP remained significantly reduced from baseline 12 months after phaco-ELT regardless of preoperative IOP levels, with no major complications. The IOP reduction remained constant over the entire follow-up. Hence, phaco-ELT can be considered in glaucoma and ocular hypertensive patients whenever cataract surgery is performed, in order to further reduce IOP or to reduce the requirement for IOP-reducing medications. PMID:23799932

  20. Raman-shifting an ArF excimer laser to generate new lines for obtaining optical diagnostic based information in flow fields

    NASA Astrophysics Data System (ADS)

    Koker, Edmond B.

    1994-12-01

    The application of tunable excimer lasers in combustion and flow diagnostics is almost routine nowadays. The properties of this laser system that enable density and temperature measurements in supersonic and hypersonic flow fields to be conducted are its high power, high repetition rate, and high spectral brightness. The limitation imposed by this system on these measurements is the paucity of lines in the wavelength region, the vacuum-ultraviolet, where species of interest, such as OH, N2, O2, H2, H2O, CO, NO, etc., are susceptible to electronic excitation to high-lying states. To circumvent this problem one normally resorts to nonlinear optical techniques such as frequency conversion via stimulated Raman scattering (SRS), more commonly known as Raman shifting or Raman mixing, to extend these nonintrusive and nonperturbing techniques to the shorter wavelengths in the VUV region and, for that matter, to longer wavelengths in the infrared region, if the need arises. The theoretical basis of SRS and its application are well documented in the literature. In essence, the Raman shift is a consequence of the inelastic scattering of the incident radiation by the sample. Most of the scattered radiation from the molecules of the sample is unchanged in frequency. However, a small fraction of the incident radiation is changed in frequency. This shift is a result of the fact that some of the incident photons on colliding with the molecules of the sample give up some of their energy and emerge with a lower energy resulting in the lower-frequency Stokes radiation. Other incident photons may increase their energy by colliding with the vibrationally excited molecules of the medium and emerge as higher-frequency antistokes radiation. The generation of the latter is the main objective of this project. The process, however, depends on several factors, including the beam quality of the pump laser, the cross-section of the gaseous medium, the gas pressure, and the ambient temperature

  1. Raman-shifting an ArF excimer laser to generate new lines for obtaining optical diagnostic based information in flow fields

    NASA Technical Reports Server (NTRS)

    Koker, Edmond B.

    1994-01-01

    The application of tunable excimer lasers in combustion and flow diagnostics is almost routine nowadays. The properties of this laser system that enable density and temperature measurements in supersonic and hypersonic flow fields to be conducted are its high power, high repetition rate, and high spectral brightness. The limitation imposed by this system on these measurements is the paucity of lines in the wavelength region, the vacuum-ultraviolet, where species of interest, such as OH, N2, O2, H2, H2O, CO, NO, etc., are susceptible to electronic excitation to high-lying states. To circumvent this problem one normally resorts to nonlinear optical techniques such as frequency conversion via stimulated Raman scattering (SRS), more commonly known as Raman shifting or Raman mixing, to extend these nonintrusive and nonperturbing techniques to the shorter wavelengths in the VUV region and, for that matter, to longer wavelengths in the infrared region, if the need arises. The theoretical basis of SRS and its application are well documented in the literature. In essence, the Raman shift is a consequence of the inelastic scattering of the incident radiation by the sample. Most of the scattered radiation from the molecules of the sample is unchanged in frequency. However, a small fraction of the incident radiation is changed in frequency. This shift is a result of the fact that some of the incident photons on colliding with the molecules of the sample give up some of their energy and emerge with a lower energy resulting in the lower-frequency Stokes radiation. Other incident photons may increase their energy by colliding with the vibrationally excited molecules of the medium and emerge as higher-frequency antistokes radiation. The generation of the latter is the main objective of this project. The process, however, depends on several factors, including the beam quality of the pump laser, the cross-section of the gaseous medium, the gas pressure, and the ambient temperature

  2. [Narrowband UV-B, monochromatic excimer laser, and photodynamic therapy in psoriasis: a consensus statement of the Spanish Psoriasis Group].

    PubMed

    Carrascosa, J M; López-Estebaranz, J L; Carretero, G; Daudén, E; Ferrándiz, C; Vidal, D; Belinchón, I; Sánchez-Regaña, M; Puig, L

    2011-04-01

    Novel treatment strategies and new information concerning the management of moderate to severe psoriasis justify a reassessment of the role of the classic therapies in this setting. This consensus statement evaluates narrowband UV-B therapy, which is currently considered the phototherapy option of choice in psoriasis because of its risk-to-benefit ratio. The role of excimer laser and photodynamic therapies are also discussed. These targeted therapies are still only available in a small number of centers in Spain and are used principally in the treatment of localized and recalcitrant forms of psoriasis. We discuss the efficacy and safety of phototherapy as well as treatment regimens, combination therapy, and clinical considerations relating to the characteristics of the patient or the disease.

  3. A novel approach to pseudopodia proteomics: excimer laser etching, two-dimensional difference gel electrophoresis, and confocal imaging

    PubMed Central

    Mimae, Takahiro; Ito, Akihiko; Hagiyama, Man; Nakanishi, Jun; Hosokawa, Yoichiroh; Okada, Morihito; Murakami, Yoshinori; Kondo, Tadashi

    2014-01-01

    Pseudopodia are actin-rich ventral cellular protrusions shown to facilitate the migration and metastasis of tumor cells. Here, we present a novel approach to perform pseudopodia proteomics. Tumor cells growing on porous membranes extend pseudopodia into the membrane pores. In our method, cell bodies are removed by horizontal ablation at the basal cell surface with the excimer laser while pseudopodia are left in the membrane pores. For protein expression profiling, whole cell and pseudopodia proteins are extracted with a lysis buffer, labeled with highly sensitive fluorescent dyes, and separated by two-dimensional gel electrophoresis. Proteins with unique expression patterns in pseudopodia are identified by mass spectrometry. The effects of the identified proteins on pseudopodia formation are evaluated by measuring the pseudopodia length in cancer cells with genetically modified expression of target proteins using confocal imaging. This protocol allows global identification of pseudopodia proteins and evaluation of their functional significance in pseudopodia formation within one month. PMID:25309719

  4. Ultra-shallow p{sup +}-junction formation in silicon by excimer laser doping -- A heat and mass transfer perspective

    SciTech Connect

    Zhang, X.; Ho, J.R.; Grigoropoulos, C.P.

    1995-12-31

    A new technique is developed to fabricate the ultra-shallow p{sup +}-junctions with the depth from 30 nm to 400 nm. The ultra-shallow p{sup +}-junction is successfully made by the excimer laser doping of crystalline silicon with a solid spin-on-glass (SOG) dopant. High boron concentration of 10{sup 20} atoms/cc and the box-like junction profile are achieved through the nanosecond pulsed laser heating, melting, and boron mass diffusion in the 100 nm thin silicon layer close to the surface. The key mechanism determining the box-like junction shape is found to be the melt-solid interface limited diffusion. The optimal laser fluence condition for SOG doping is found about 0.6--0.8 J/cm{sup 2} by studying the ultra-shallow p{sup +}-junction boron profiles measured by the secondary ion mass spectroscopy (SIMS) versus the laser fluence and the pulse number. Heat and mass transfer are studied at the nanosecond time scale and the nanometer length scale. The ID numerical analysis agrees reasonably with the experiment, within the available physical picture. Possible mechanisms such as boron diffusivity dependence on the dopant concentration in the molten silicon are proposed.

  5. Direct growth of patterned graphene on SiC(0001) surfaces by KrF excimer-laser irradiation

    NASA Astrophysics Data System (ADS)

    Hattori, Masakazu; Furukawa, Kazuaki; Takamura, Makoto; Hibino, Hiroki; Ikenoue, Hiroshi

    2015-03-01

    A novel method of direct growth of patterned graphene on SiC(0001) surfaces using KrF excimer-laser irradiation is proposed. It relies on the local sublimation of Si atoms within the irradiated area to induce graphene growth through a rearrangement of surplus carbon. A laser with a wavelength of 248 nm was pulsed with a duration of 55 ns and a repetition rate of 100 Hz that was used to graphene forming. Following laser irradiation of 1.2 J/cm2 (5000 shots) under an Ar atmosphere (500 Pa), characteristic graphene peaks were observed in the Raman spectra of the irradiated area, thereby confirming the formation of graphene. The ratio between the graphene bands in the Raman spectra was used to estimate the grain size at 61.3 nm. Through high-resolution transmission electron microscopy, it was confirmed that two layers of graphene were indeed formed in the laser irradiated region. Using this knowledge, we also demonstrate that line-and-space (LandS) graphene patterns with a pitch of 8 μm can be directly formed using our method.

  6. Surface studies on benzophenone doped PDMS microstructures fabricated using KrF excimer laser direct write lithography

    NASA Astrophysics Data System (ADS)

    Kant, Madhushree Bute; Shinde, Shashikant D.; Bodas, Dhananjay; Patil, K. R.; Sathe, V. G.; Adhi, K. P.; Gosavi, S. W.

    2014-09-01

    This paper discusses microfabrication process for benzophenone doped polydimethylsiloxane (PDMS) using laser lithography. KrF excimer laser of 248 nm with 20 ns pulse width at repetition rate of 1 Hz was used for microfabrication of undoped and benzophenone doped PDMS. The doped-PDMS shows sensitivity below 365 nm, permitting processing under ambient light. The analysis of etch depth revealed that doped PDMS shows self developable sensitivity at lower fluence of ∼250 mJ/cm2. The unexposed and exposed surface was studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Scanning electron microscopy (SEM). Spectrocopic analysis indicated increase in Csbnd O, Cdbnd O, Sisbnd O3 and Sisbnd O4 bonding at the expense of Sisbnd C and Sisbnd O2 bonds of PDMS. In case of laser exposed doped-PDMS, removal of benzophenone from probe depth of spectroscopy was observed. Whereas the surface morphology of exposed and unexposed doped-PDMS was observed to be same, indicating clean development of PDMS micropatterns. The present study indicates that addition of 3.0 wt.% benzophenone in PDMS enhance self development sensitivity of PDMS. The self developable results on doped-PDMS are quite encouraging for its potential use in point of care Lab-On-Chip applications, for fabricating micropatterns using direct write laser lithography technology.

  7. DNA damage and altered gene expression in cultured human skin fibroblasts exposed to 193-nm excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Samid, Dvorit; Flessate, Denise M.; Miller, Alexandra C.; Rimoldi, Donata

    1990-06-01

    Tissue ablation using 193nm excimer lasers is being considered for a variety of surgical procedures, yet little is known regarding the potential mutagenic risk to human cells. The effects of sublethal doses of radiation on cellular DNA and gene expression have been examined in cultured human skin fibroblasts. Northern blot analysis of mRNA revealed an increase in the levels of the c-f. proto-oncogene, interstitial collagenase, and metallothionein transcripts after laser radiation at either 193nm or 248nm. Similar changes in gene expression have been previously observed in cells treated with different carcinogens, including classical UV light (254nm) and phorbol esters. In contrast to the conventional UV light or laser radiation at 248nm, the 193nm radiation did not cause significant pyrimidine dimer formation, as determined by measurements of unscheduled DNA synthesis. However, both 193nm and 248nm radiation induced micronuclei formation, indicative of chromosome breakage. These data indicate that exposure of actively replicating human skin cells to sublethal doses of 193nm laser radiation may result in molecular changes associated with carcinogenesis.

  8. Responsivity uniformity enhancements for Backside-Illuminated Charge-Coupled Devices (BICCDs) by excimer laser-assisted etching

    NASA Astrophysics Data System (ADS)

    Russell, Stephen D.; Sexton, Douglas A.

    1991-05-01

    BICCDs are solid-state electronic imaging devices which read out image charges from wells in an array of pixels. The substrate below the pixel array is typically thinned by chemically etching (100)-oriented silicon using a potassium hydroxide (KOH) etch. The potassium hydroxide anisotropically etches to the (111) crystallographic plane in silicon, leaving smooth sidewalls at an angle of 54.7 deg to the image plane. This smooth surface acts as a mirror to reflect extraneous light onto the image plane of the BICCD, causing spurious images and reducing the responsivity uniformity (RU) of the devices. We have developed a noncontact excimer laser-assisted process to promote a chemical reaction between a halocarbon ambient and the silicon. The laser-assisted chemical reaction results in a roughened (textured) surface which behaves as a light sink. The use of a nonreactive ambient allows us to texture the sidewalls of prepackaged and pretested devices. The sidewalls of fully functional BICCD die have been textured in a Freon-115 (chloropentafluoroethane) ambient by directing 5000 pulses with laser fluence of about 0.75 J/sq cm upon them. The RU of the devices as well as the background level (fat-zero) are dramatically improved.

  9. Rapid fabrication of rigid biodegradable scaffolds by excimer laser mask projection technique: a comparison between 248 and 308 nm

    NASA Astrophysics Data System (ADS)

    Beke, S.; Anjum, F.; Ceseracciu, L.; Romano, I.; Athanassiou, A.; Diaspro, A.; Brandi, F.

    2013-03-01

    High-resolution photocrosslinking of the biodegradable poly(propylene fumarate) (PPF) and diethyl fumarate (DEF), using pulsed laser light at 248 and 308 nm is presented. The curing depth can be modulated between a few hundreds of nm and a few μm when using 248 nm and ten to a hundred μm when using 308 nm. By adjusting the total fluence (pulse numbers×laser fluence) dose and the weight ratios of PPF, DEF, and the photoinitiator in the photocrosslinkable mixtures, the height of polymerized structures can be precisely tuned. The lateral resolution is evaluated by projecting a pattern of a grid with a specified line width and line spacing. Young’s modulus of the cured parts is measured and found to be several GPa for both wavelengths, high enough to support bone formation. Several 2D and 2.5D microstructures, as well as porous 3D scaffolds fabricated by a layer-by-layer method, are presented. The results demonstrate that excimer laser-based photocuring is suitable for the fabrication of stiff and biocompatible structures with defined patterns of micrometer resolution in all three spatial dimensions.

  10. Effect of KrF Pulsed Excimer Laser Treatment on Surface Microstructure of Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Mahanty, S.; Gouthama

    2016-09-01

    In the present research, the Al-Si alloy surface is treated by KrF excimer pulse laser for different number of laser pulses in ambient condition at energy 4.75 J/cm2. The surface microstructural characterization was done by the optical microscope, in situ video recording during laser pulsing, SEM and TEM. The fretting wear test was undertaken to assess the tribological behavior. In situ video recording showed changes in the surface reflectivity with the number of pulses which is related to progressive changes in the surface compositional homogeneity. After ten pulses, signs of rippled structure were observed. The 15 pulse samples showed star-like morphological feature at the central region. The TEM observations showed high density of stacking faults/twins in Si after first pulse treatment. After 15 pulses, nano-crystalline Si precipitates in the size range <5 nm are seen to be homogeneously distributed. A cellular structure with the cell size <100 nm formed in the matrix. These cell boundaries were decorated with the Si nanocrystals. A positive effect in wear resistance property is observed after the 15 pulses treatment.

  11. Formation of the surface structure of polyethylene-terephtalate (PET) due to ArF excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Csete, M.; Révész, K.; Vinkó, J.; Bor, Zs.

    1996-04-01

    The development process of the surface structure on polyethylene-terephtalate (PET) has been investigated. It was found that the average dimension and shape of its unit cells depend on the excimer laser fluence, the incident angle of the ablating laser beam (the longitudinal dimension is proportional to cons × tan( α) + D formula, where D means the average dimension of the unit cell at α = 0°) and the number of shots (the average dimension and height proportional to the logarithm of the number of shots). A dye laser based arrangement was constructed to investigate the temporal dependence of the scattered probe light intensity from the ablated polymer surface. It was found that the formation of the surface structure takes place in the time range of 5-10 μs. We used a heat diffusion melting model to explain the development of the surface structure. A simple 1D simulation of the heat transfer shows that the lifetime of the liquid phase (˜ 1-7 μs) is comparable with the time scale mentioned above.

  12. Development of a Silicon Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System

    SciTech Connect

    C.A. Gentile; H.M. Fan; J.W. Hartfield; R.J. Hawryluk; F. Hegeler; P.J. Heitzenroeder; C.H. Jun; L.P. Ku; P.H. LaMarche; M.C. Myers; J.J. Parker; R.F. Parsells; M. Payen; S. Raftopoulos; J.D. Sethian

    2002-11-21

    The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, <100>, <110> and <111>) for use as electron-beam transmission windows in a KrF excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). Chosen window geometry must accommodate electron energy transfer greater than 80% (750 keV), while maintaining structural integrity during mechanical load (1.3 to 2.0 atm base pressure differential, approximate 0.5 atm cyclic pressure amplitude, 5 Hz repetition rate) and thermal load across the entire hibachi area (approximate 0.9 W {center_dot} cm superscript ''-2''). In addition, the window must be chemically resistant to attack by fluorine free-radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4 mm square silicon prototype window, coated with 500 nm thin-film silicon nitride (Si{sub 3}N{sub 4}), has been fabricated. The window consists of 81 square panes with a thickness of 0.019 mm {+-} 0.001 mm. Stiffened (orthogonal) sections are 0.065 mm in width and 0.500 mm thick (approximate). Appended drawing (Figure 1) depicts the window configuration. Assessment of silicon (and silicon nitride) material properties and CAD modeling and analysis of the window design suggest that silicon may be a viable solution to inherent parameters and constraints.

  13. Laser remelting of Ti6AL4V using high power diode laser

    NASA Astrophysics Data System (ADS)

    Amaya-Vázquez, M. R.; Sánchez-Amaya, J. M.; Boukha, Z.; El Amrani, K.; Botana, F. J.

    2012-04-01

    Titanium alloys present excellent mechanical and corrosion properties, being widely employed in different industries such as medical, aerospace, automotive, petrochemical, nuclear and power generation, etc. Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with convectional heat treatments and/or with laser processing. Laser remelting (LR) is a technology applied to Ti6Al4V by other authors with excimer and Nd-Yag laser with pure argon shielding gas to prevent risk of oxidation. In the present contribution, laser remelting has been applied for the first time to Ti6Al4V with a high power diode laser (with pure argon as shielding gas). Results showed that remelted samples (with medium energy densities) have higher microhardness and better corrosion resistance than Ti6Al4V base metal.

  14. Powerful copper chloride laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.

    1981-01-01

    Two design innovations give up to thirtyfold increase in power in 300 W laser amplifier. Heat is removed by flowing lasing gas through system, allowing larger lasing volumes. Fast, uniform excitation discharges are obtained with transverse, rather than longitudinal, electrodes.

  15. Infrared diode laser kinetic spectroscopy of the CCO radical in the X-tilde 3Sigma - state generated by the excimer laser photolysis of carbon suboxide

    NASA Astrophysics Data System (ADS)

    Yamada, Chikashi; Kanamori, Hideto; Horiguchi, Hiroyuki; Tsuchiya, Soji; Hirota, Eizi

    1986-03-01

    The ν1 band of the CCO radical in the X˜ 3Σ- ground electronic state has been observed in the gas phase by diode laser kinetic spectroscopy. The CCO radical was generated by the 193 or 248 nm excimer laser photolysis of carbon suboxide. By fixing ground state parameters to the microwave values, the band origin and the vibrational changes of the rotational (αB=B0-B1) and spin-spin interaction (αλ=λ1-λ0) constants have been determined to be 1970.864 34(95), 0.003 075 4(85), and 0.008 3(12) in cm-1 with 2.5 standard errors in parentheses.

  16. Synthesis of nano-scale silicon wires by excimer laser ablation at high temperature

    NASA Astrophysics Data System (ADS)

    Yu, D. P.; Lee, C. S.; Bello, I.; Sun, X. S.; Tang, Y. H.; Zhou, G. W.; Bai, Z. G.; Zhang, Z.; Feng, S. Q.

    1998-02-01

    We report below synthesis of nano-scale silicon wires by using laser ablation at high temperature. By this approach we have been able to produce silicon nano wires (SiNW's) with a very high yield, a uniform diameter distribution and a high purity. The structure, morphology and chemical composition of the SiNWs have been characterized by using high resolution X-ray diffraction (XRD), high resolution electron microscopy (HREM), as well as spectroscopy of energy dispersive X-ray fluorescence (EDAX). Our results should be of great interest to researchers working on mesoscopic physical phenomena, such as quantum confinement effects related to materials of reduced dimensions and should lead to the development of new applications for nano-scale devices, together with providing a powerful method for synthesis of similar one-dimensional conducting and semi-conducting wire.

  17. Chaînes laser intenses à contraste élevé par amplification directe dans un milieu gazeux à excimères*

    NASA Astrophysics Data System (ADS)

    Uteza, O.; Tcheremiskine, V.; Clady, R.; Coustillier, G.; Gastaud, M.; Sentis, M.; Mikheev, L. D.; Chambaret, J. P.

    2006-12-01

    Cet article présente l'intérêt du concept de laser hybride (solide/gaz) et de l'amplification directe de puissance dans un milieu à excimères pour les chaînes laser de puissance ultrabrèves à contraste élevé. L'architecture d'une chaîne laser multiterawatt basée sur l'emploi du milieu amplificateur XeF(C-A) pompé par voie photolytique est ensuite détaillée, ainsi que les perspectives de dimensionnement de cette approche au niveau PWetEW.

  18. Applying low-energy multipulse excimer laser annealing to improve charge retention of Au nanocrystals embedded MOS capacitors

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    The low-energy multipulse excimer laser annealing (LEM-ELA) is proposed to anneal the nanostructure of nanocrystal (NC) embedded in a SiO2 thin film without causing atomic diffusion and damaging the NCs, since the LEM-ELA combining the advantages of laser annealing and UV curing features rapid heating and increasing oxide network connectivity. A Fourier transform infrared spectroscopy (FTIR) characterization of SiO2 thin films annealed using LEM-ELA indicated that the quality was improved through the removal of water-related impurities and the reconstruction of the network Si-O-Si bonds. Then, LEM-ELA was applied to a SiO2 thin film embedded with Au NCs, which were fabricated as MOS capacitors. The charge retention was greatly improved and the percentage of retained charges was about 10% after 3  ×  108 s. To investigate and differentiate the effects of LEM-ELA on charges stored in both oxide traps and in the Au NCs, a double-mechanism charge relaxation analysis was performed. The results indicated that the oxide traps were removed and the confinement ability of Au NCs was enhanced. The separated memory windows contributed from the charges in Au NCs and those in oxide traps were obtained and further confirmed that the LEM-ELA removed oxide traps without damaging the Au NCs.

  19. Cost-effective SU-8 micro-structures by DUV excimer laser lithography for label-free biosensing

    NASA Astrophysics Data System (ADS)

    Sanza, F. J.; Laguna, M. F.; Casquel, R.; Holgado, M.; Barrios, C. A.; Ortega, F. J.; López-Romero, D.; García-Ballesteros, J. J.; Bañuls, M. J.; Maquieira, A.; Puchades, R.

    2011-04-01

    Cost-effective SU-8 micro-structures on a silicon substrate were developed using 248 nm excimer laser KrF projection, studying the influence of the different variables on the final pattern geometry, finding out that the most critical are exposure dose and post-bake condition. Also a novel and cost effective type of photomask based on commercial polyimide Kapton produced by 355 nm DPSS laser microprocessing was developed, studying the influence of the cutting conditions on the photomask. Finally, as a likely application the biosensing capability with a standard BSA/antiBSA immunoassay over a 10 × 10 micro-plates square lattice of around 10 μm in diameter, 15 μm of spacing and 400 nm in height was demonstrated, finding a limit of detection (LOD) of 33.4 ng/ml which is in the order of magnitude of bioapplications such as detection of cortisol hormone or insulin-like growth factor. Low cost fabrication and vertical interrogation characterization techniques lead to a promising future in the biosensing technology field.

  20. A novel microsurgery method for intact plant tissue at the single cell level using ArF excimer laser microprojection.

    PubMed

    Kajiyama, Shin'ichiro; Shoji, Takeshi; Okuda, Shinya; Izumi, Yoshihiro; Fukusaki, Ei-ichiro; Kobayashi, Akio

    2006-02-01

    A novel microsurgery technique for the partial removal of rigid cell-walls in intact plant tissue is established. Using a size-variable slit, an ArF excimer laser was microprojected on the surface of the targeted cell, and this method enabled the area- and depth-controllable processing of the cortical structure of plant cells including the cuticle and cell wall layer. In epidermal cells of all tested plants, viabilities of more than 90% were retained 24 h after irradiation. Scanning electron microscope (SEM) observation revealed that the cuticle layer of the irradiated region was completely ablated, and the cellulose microfibrils of the secondary cell wall were partially removed; furthermore, 4 days after laser treatment, the regeneration of cell wall fibrils was observed. As a model experiment, the transient expression of synthetic green fluorescent protein (sGFP) was performed by the microinjection of cauliflower mosaic virus (CMV) 35S promoter-derived sGFP gene through an "aperture" in the treated cell surface. Moreover, micron-sized fluorescent beads were successfully introduced by the same method into the onion cells indicating that this method can be used to introduce foreign materials as large as organelles. PMID:16193516

  1. Microhollow cathode discharge excimer lamps

    SciTech Connect

    Schoenbach, Karl H.; El-Habachi, Ahmed; Moselhy, Mohamed M.; Shi, Wenhui; Stark, Robert H.

    2000-05-01

    Microhollow cathode discharges are high-pressure, nonequilibrium gas discharges between a hollow cathode and a planar or hollow anode with electrode dimensions in the 100 {mu}m range. The large concentration of high-energy electrons, in combination with the high-gas density favors excimer formation. Excimer emission was observed in xenon and argon, at wavelengths of 128 and 172 nm, respectively, and in argon fluoride and xenon chloride, at 193 and 308 nm. The radiant emittance of the excimer radiation was found to increase monotonically with pressure. However, due to the decrease in source size with pressure, the efficiency (ratio of excimer radiant power to input electrical power), has for xenon and argon fluoride a maximum at {approx}400 Torr. The maximum efficiency is between 6% and 9% for xenon, and {approx}2% for argon fluoride. (c) 2000 American Institute of Physics.

  2. Microhollow cathode discharge excimer lamps

    NASA Astrophysics Data System (ADS)

    Schoenbach, Karl H.; El-Habachi, Ahmed; Moselhy, Mohamed M.; Shi, Wenhui; Stark, Robert H.

    2000-05-01

    Microhollow cathode discharges are high-pressure, nonequilibrium gas discharges between a hollow cathode and a planar or hollow anode with electrode dimensions in the 100 μm range. The large concentration of high-energy electrons, in combination with the high-gas density favors excimer formation. Excimer emission was observed in xenon and argon, at wavelengths of 128 and 172 nm, respectively, and in argon fluoride and xenon chloride, at 193 and 308 nm. The radiant emittance of the excimer radiation was found to increase monotonically with pressure. However, due to the decrease in source size with pressure, the efficiency (ratio of excimer radiant power to input electrical power), has for xenon and argon fluoride a maximum at ˜400 Torr. The maximum efficiency is between 6% and 9% for xenon, and ˜2% for argon fluoride.

  3. X-Ray Radiation Measurements With Photodiodes In Plasmas Generated By 1017 W/Cm2 Intensity Krf Excimer Laser Pulses

    NASA Astrophysics Data System (ADS)

    Rácz, E.; Földes, I. B.; Ryć, L.

    2006-01-01

    Experiments were carried out using a prepulse-free hybrid KrF excimer-dye laser system (700fs pulse duration, 248nm wavelength, 15mJ pulse energy). The intensity of the p-polarized, focused laser beam was 1.5ṡ1017 W/cm2. Vacuum ultraviolet (VUV) and x-rays from solid state laser plasmas were generated in the laser-plasma interaction of subpicosecond laser pulses of nonrelativistic laser intensities. An x-ray sensitive FLM photodiode (ITE, Warsaw) was used to detect x-rays between 1-19 keV in front of the targets. The diode was filtered by a 4μm Al foil. The dependence of the x-ray flux on laser intensity and the angular distribution of x-rays for aluminum and copper targets in the half space of the front side of the targets were investigated.

  4. The advances and characteristics of high-power diode laser materials processing

    NASA Astrophysics Data System (ADS)

    Li, Lin

    2000-10-01

    This paper presents a review of the direct applications of high-power diode lasers for materials processing including soldering, surface modification (hardening, cladding, glazing and wetting modifications), welding, scribing, sheet metal bending, marking, engraving, paint stripping, powder sintering, synthesis, brazing and machining. The specific advantages and disadvantages of diode laser materials processing are compared with CO 2, Nd:YAG and excimer lasers. An effort is made to identify the fundamental differences in their beam/material interaction characteristics and materials behaviour. Also an appraisal of the future prospects of the high-power diode lasers for materials processing is given.

  5. Microswelling-free negative resists for ArF excimer laser lithography utilizing acid-catalyzed intramolecular esterification

    NASA Astrophysics Data System (ADS)

    Hattori, Takashi; Tsuchiya, Yuko; Yokoyama, Yoshiyuki; Oizumi, Hiroaki; Morisawa, Taku; Yamaguchi, Atsuko; Shiraishi, Hiroshi

    1999-06-01

    We have examined alicyclic polymers with a (gamma) -hydroxy acid structure in order to investigate the properties of (gamma) -hydroxy acid and (gamma) -lactone as function groups of ArF negative resist materials. From the viewpoint of transparency and dry-etching resistance, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable for ArF negative resists materials. Surprisingly, the reactivity of the acid-catalyzed reaction of (gamma) -hydroxy acid is affected by the polymer structure. Using ArF excimer laser stepper, 0.20-micrometers line-and-space patterns without micro-swelling distortion were obtained from a negative resist consisting of alicyclic polymer with the (gamma) - hydroxy acid structure and a photoacid generator. Distortion was avoided because the number of carboxyl groups decreased drastically in the exposed area by the acid-catalyzed intramolecular esterification of (gamma) -hydroxy acid to (gamma) -lactone. As a result, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable function groups for ArF negative resist materials.

  6. Substrate effect on excimer laser assisted crystal growth in phosphor Ca 0.997Pr 0.002TiO 3 polycrystalline thin films

    NASA Astrophysics Data System (ADS)

    Nakajima, Tomohiko; Tsuchiya, Tetsuo; Kumagai, Toshiya

    2007-12-01

    Ca 0.997Pr 0.002TiO 3 thin films that show strong red luminescence were successfully prepared by means of an excimer laser assisted metal organic deposition process with a KrF laser at a fluence of 100 mJ/cm 2 at 100 °C. The CPTO films grew on the silica, borosilicate, and indium-tin-oxide coated glasses. The crystallinity of the Ca 0.997Pr 0.002TiO 3 films depended on the substrates; the borosilicate and indium-tin-oxide coated glasses with a large optical absorption of a KrF laser ( λ = 248 nm) were effective for the crystallization for the Ca 0.997Pr 0.002TiO 3. In addition, a high thermal conductivity of the indium-tin-oxide coated glass substrate could also improve the crystallinity due to an enhancement of thermal propagation to the film. Oxygen annealing at 500 °C for 6 h successfully eliminated the oxygen vacancy produced by the laser irradiation, and also remarkably improved the PL emission intensity. Thus, we have shown that substrate properties such as an optical absorbance and a thermal conductivity were quite important factors for the crystal growth and the PL emission for the Ca 0.997Pr 0.002TiO 3 in the excimer laser assisted metal organic deposition process.

  7. High power solid state lasers

    SciTech Connect

    Weber, H.

    1988-01-01

    These proceedings discuss the following subjects: trends in materials processing with laser radiation; slabs and high power systems; glasses and new crystals; solid state lasers at HOYA Corp.; lamps, resonators and transmission; glasses as active materials for high average power solid state lasers; flashlamp pumped GGG-crystals; alexandrite lasers; designing telescope resonators; mode operation of neodymium: YAG lasers; intracavity frequency doubling with KTP crystal and thermal effects in cylinder lasers.

  8. Numerical modeling of short-pulse excimer lasers with negative branch unstable cavities.

    PubMed

    Fang, H; Perrone, M R

    1995-05-20

    A one-dimensional code for the numerical simulation of negative branch unstable resonators with an intracavity aperture that are applied to high-gain, short-pulse XeCl lasers is described. The model predicts near- and far-field performance of the output laser beams. The intracavity aperture size is shown as an important parameter for control of the output beam energy and divergence. A comparison with experimental measurements is presented. PMID:21052408

  9. Direct current planar excimer source

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Takano, N.; Schoenbach, K. H.; Guru, D.; McLaren, J.; Heberlein, J.; May, R.; Cooper, J. R.

    2007-07-01

    Excimer emission at 172 nm was observed from xenon discharges generated between a perforated anode, with opening dimensions in the sub-millimetre range, and a planar cathode. A thin dielectric layer 100-250 µm in thickness, with the same size opening as the anode, is aligned with the anode opening and used to separate the electrodes. Devices with this structure are referred to as cathode boundary layer (CBL) discharge or micro-hollow cathode discharge devices, depending on the surface structure of the cathode. The emission intensity and efficiency of these devices are pressure- and current-dependent. Typical power densities and internal efficiencies (ratio of excimer radiant power to electrical input power) are 0.5-1.5 W cm-2 and 3-5%, respectively. In the current range between normal and abnormal mode operation, the CBL discharge shows regularly arranged filaments (self-organization). Optimum emission of the excimer radiation is observed at the transition from the normal glow mode to self-organization. The resistive current-voltage characteristic in the self-organization region allows the operation of multiple CBL devices in parallel without individual ballast, but with an excimer emission slightly off the maximum value. The measured decrease of the excimer emission to about 10% of its initial value after approximately 250 h of continuous operation seems to be caused by the increasing contamination of xenon, through minor leaks in the discharge chamber and/or the outgassing of chamber components. Refilling the chamber with fresh gas after such an extended operation resulted in full recovery of the discharge with respect to excimer emission. The results suggest the possibility of generating extended lifetime, intense, large area, planar excimer sources using CBL discharges in sealed discharge chambers including getters.

  10. Removal of dust particles from metal-mirror surfaces by excimer-laser radiation

    NASA Astrophysics Data System (ADS)

    Mann, Klaus R.; Wolff-Rottke, B.; Mueller, F.

    1995-07-01

    The effect of particle desorption from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way of cleaning the Al coatings of future very large telescope mirrors. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples, taking particularly into account laser-induced damage and degradation effects of coating and substrate. The particle removal rate increases with increasing laser fluence, being limited however by the damage threshold of the coating. Therefore, parameters influencing the damage threshold of metal coatings like wavelength, pulse width, and number of pulses have been studied in detail. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be reinstalled, in particular when an additional solvent film on the sample surface is applied. Hence, laser desorption seems to be a viable method of cleaning large Al mirrors for telescopes.

  11. Schlieren measurements of the hydrodynamics of excimer laser ablation of polymers in atmospheric pressure gas

    NASA Astrophysics Data System (ADS)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Sell, Jeffrey A.; Heffelfinger, David M.

    1990-08-01

    Pulsed schlieren photography and fast helium-neon laser deflection are used to study the hydrodynamics of laser ablation of polyethyleneterephthalate and polymethylmethacrylate by pulsed KrF (248 nm) radiation in atmospheric air, Ar and N2. Schlieren measurements show the evolution of shock waves, sound waves, and reduced-density, hot gas plumes. A transition from sound to shock at the ablation threshold for both polymers is observed. The shock velocity of PET tends to approach agreement with blast wave theory at fluences higher than 1 J/cm2. Plumes in air are consistently larger than those produced in Ar and N2 (at fluences below 5 J/cm2) suggesting that combustion may occur. Laser deflection measurements for PET at 150 mJ/cm2 indicate a plume density of 0.6 kg/m3 (50% atmospheric density).

  12. Propulsion by laser power

    NASA Astrophysics Data System (ADS)

    Schall, Wolfgang O.

    2005-03-01

    Laser power can be transformed into propulsive power to set into motion various kinds of vehicles and other objects on the surface, in the air and in space. The transformation process can occur indirectly, for instance by producing electricity via photovoltaic cells or thermal power. Another possibility is the generation of impulses by the ablation of matter from a solid body, or by the initiation of a high-pressure plasma breakdown wave in a fluid medium. Applications range from driving remotely powered roving vehicles to various kinds of thrusters for space propulsion. The direct thrust of the laser photon flux can be used for the propulsion of laser sailcrafts. Applications in space range from micropropulsion for satellite attitude control in the near-term to futuristic interstellar travel driven by photon propulsion. Other propulsive applications in space concern the change of orbits of objects like man-made orbital debris as well as of large objects (asteroids, comets) for protection of Earth against disastrous impacts.

  13. Low Specific Contact Resistivity to n-Ge and Well-Behaved Ge n+/p Diode Achieved by Implantation and Excimer Laser Annealing

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Li, Cheng; Huang, Shihao; Lu, Weifang; Yan, Guangming; Lin, Guangyang; Wei, Jiangbin; Huang, Wei; Lai, Hongkai; Chen, Songyan

    2013-10-01

    Excimer laser annealing of phosphorus-implanted p-type germanium substrate with various laser energy densities for n+/p junction were investigated. The effects of laser energy density on the redistribution of dopant, surface morphology, and recrystallization of the amorphous Ge induced by ion implantation were characterized. A low specific contact resistivity of 1.61×10-6 Ω·cm2 was achieved from Al/n-Ge ohmic contact, in which phosphorus-implanted Ge was annealed at a laser energy density of 250 mJ/cm2, tailoring a small phosphorus diffusion length, high activation level, and low dopant loss. A well-behaved Ge n+/p diode with a rectification ratio up to 1.99×105 was demonstrated.

  14. Excimer and Nd:YAG laser-induced SF6 decomposition at the vicinity of amorphous SiO2 glass

    NASA Astrophysics Data System (ADS)

    Dehghanpour, H. R.; Parvin, P.

    2010-11-01

    In this work, the evidence of SF6 gas decomposition at the vicinity of SiO2 glass has been investigated using various laser wavelengths: at 193, 248, 532 and 1064 nm. It was shown that SiF4 gas and S2F10 clusters were simultaneously created during ArF excimer laser irradiation, while no by-products were seen in the irradiation cell using Q-switched Nd:YAG laser. The gas content analysis was carried out using laser breakdown spectroscopy (LIBS) and Fourier transform IR spectroscopy (FTIR). Moreover, the fluorine penetration into the glass surface was studied by energy dispersive X-ray (EDX) microanalysis and wavelength dispersive X-ray (WDX) mapping to support the suggested mechanisms.

  15. Single photon excimer laser photodissociation of highly vibrationally excited polyatomic molecules

    SciTech Connect

    Tiee, J.J.; Wampler, F.B.; Rice, W.W.

    1980-01-01

    The ir + uv photodissociation of SF/sub 6/ has been performed using CO/sub 2/ and ArF lasers. The two-color photolysis significantly enhances the photodissociation process over ArF irradiation alone and is found to preserve the initial isotopic specificity of the ir excitation process.

  16. Photoablation characteristics of novel polyimides synthesized for high-aspect-ratio excimer laser LIGA process

    NASA Astrophysics Data System (ADS)

    Yang, Chii-Rong; Hsieh, Yu-Sheng; Hwang, Guang-Yeu; Lee, Yu-Der

    2004-04-01

    The photoablation properties of two soluble polyimides DMDB/6FDA and OT/6FDA with thicknesses of over 300 µm, synthesized by the polycondensation of a hexafluoropropyl group contained in a dianhydride with two kinds of diamines, are investigated using a 248 nm krypton fluoride (KrF) laser. The incorporation of the hexafluoropropyl group into the chemical structure gives these two polyimides higher etching rates than Kapton (a commercial polyimide film which is difficult to dissolve). The etching rates of synthesized polyimides are about 0.1-0.5 µm/pulse over a fluence range of 0.25-2.25 J cm-2. The photothermal mechanism for DMDB/6FDA contributes about 19% of etching depth at a laser fluence of 0.82 J cm-2. Moreover, the number of laser pulses seriously affects the taper angle of microstructures, especially at low fluence. Near-vertical side-wall structures can be built at high fluence (~2 J cm-2). Fresnel patterns with a thickness of 300 µm and a linewidth of 10 µm were fabricated, with an attainable aspect ratio of around 30. After photoablation, the complementary metallic microstructures were also fabricated by a sequential electroplating procedure. Then, those two new polyimides could be dissolved easily in most common solvents (such as THF, DMSO, NMP and DMF). These results indicate that these two soluble polyimides are highly suitable for use in the KrF laser LIGA process.

  17. Ablation d'un film d'or par laser à excimère

    NASA Astrophysics Data System (ADS)

    Sentis, M.; Hermann, J.; Pereira, A.; Delaporte, Ph.; Marine, W.; Perrière, J.; Bianchi, L.; Galli, R.

    2003-06-01

    Ces travaux de recherche ont été réalisés dans le cadre du projet de développement du Laser MégaJoule (LMJ). Parmi les expériences d'interaction laser - matière à très haut flux, certaines conduiront à un dépôt de particules d'or sur les éléments internes de la chambre d'interaction. Pour nettoyer ce dépôt de particules, la possibilité d'utiliser un procédé automatisé basé sur l'ablation laser a été étudiée. Un modèle numérique simplifié a été développé et une étude expérimentale réalisée sur des échantillons d'acier inoxydable ou de B4C recouverts d'un film d'or d'une épaisseur de ~20 nm déposés par PVD. Ces travaux montrent que plus de 95 % du film d'or peuvent être enlevés avec quelques tirs d'un laser XeCI dès que la densité d'énergie dépasse 3 J/cm^2.

  18. Experimental measurements of multiphoton enhanced air breakdown by a subthreshold intensity excimer laser

    SciTech Connect

    Way, Jesse; Hummelt, Jason; Scharer, John

    2009-10-15

    This work presents density, spectroscopic temperature, and shockwave measurements of laser induced breakdown plasma in atmospheric air by subthreshold intensity (5.5x10{sup 9} W/cm{sup 2}) 193 nm laser radiation. Using molecular spectroscopy and two-wavelength interferometry, it is shown that substantial ionization (>10{sup 16} cm{sup -3}) occurs that is not predicted by collisional cascade (CC) breakdown theory. While the focused laser irradiance is three orders of magnitude below the theoretical collisional breakdown threshold, the substantial photon energy at 193 nm (6.42 eV/photon) compared with the ionization potential of air (15.6 eV) significantly increases the probability of multiphoton ionization effects. By spectroscopically monitoring the intensity of the N{sub 2}{sup +} first negative system (B {sup 2}SIGMA{sub u}{sup +}-X {sup 2}SIGMA{sub g}{sup +}) vibrational bandhead (v{sup '}=0,v{sup ''}=0) at low pressure (20 Torr) where multiphoton effects are dominant, it is shown that two photon excitation, resonant enhanced multiphoton ionization is the primary mechanism for quantized ionization of N{sub 2} to the N{sub 2}{sup +}(B {sup 2}SIGMA{sub u}{sup +}) state. This multiphoton effect then serves to amplify the collisional breakdown process at higher pressures by electron seeding, thereby reducing the threshold intensity from that required via CC processes for breakdown and producing high density laser formed plasmas.

  19. Numerical simulation of the dynamics of phase transitions in CdTe induced by irradiation with nanosecond pulses of an excimer laser

    SciTech Connect

    Zhvavyi, S. P. Zykov, G. L.

    2006-06-15

    Simulation of the effect of KrF nanosecond pulse excimer laser radiation ({lambda} = 248 nm, {tau} = 20 ns) on phase transitions in cadmium telluride was performed taking into account the diffusion of the melt components and their evaporation from the surface. It is shown that the surface region of the melt is enriched with tellurium due to the evaporation and diffusion of the cadmium telluride components. The obtained value 0.05 J/cm{sup 2} of the threshold energy density for melting is in reasonable agreement with the experimental data.

  20. Activities of developing high-power KrF lasers and studying laser plasmas interaction physics at CIAE

    NASA Astrophysics Data System (ADS)

    Wang, Naiyan; Shan, Yusheng; Ma, Weiyi; Yang, Dawei; Kun, Gong; Wang, Xiaojun; Tang, Xiuzhang; Tao, Yezheng; Ma, Jinglong; Jiang, Xingdong

    2002-01-01

    This report reviews the scientific activities on high power laser and laser plasma physics at CIAE. A 6-beam KrF excimer laser system (100 J/23 ns/248 nm/1013 W/cm2, 15 min/shot) has been built, the Raman technologies used to upgrade it to 1014 W/cm2 has been studied. A UV femtosecond Ti:sapphire/KrF hybrid laser (50 mJ/220 fs/248 nm/1017 W/cm2) has been developed also, hot electron generation research has been carried out in the fs laser. In the near future, the fs laser will be amplified in six-beam laser system to produce ultra-high intensity to do fundamental researches on Fast Ignition of ICF.

  1. Some optical and electron microscope comparative studies of excimer laser-assisted and nonassisted molecular-beam epitaxically grown thin GaAs films on Si

    NASA Technical Reports Server (NTRS)

    Lao, Pudong; Tang, Wade C.; Rajkumar, K. C.; Guha, S.; Madhukar, A.; Liu, J. K.; Grunthaner, F. J.

    1990-01-01

    The quality of GaAs thin films grown via MBE under pulsed excimer laser irradiation on Si substrates is examined in both laser-irradiated and nonirradiated areas using Raman scattering, Rayleigh scattering, and by photoluminescence (PL), as a function of temperature, and by TEM. The temperature dependence of the PL and Raman peak positions indicates the presence of compressive stress in the thin GaAs films in both laser-irradiated and nonirradiated areas. This indicates incomplete homogeneous strain relaxation by dislocations at the growth temperature. The residual compressive strain at the growth temperature is large enough such that even with the introduction of tensile strain arising from the difference in thermal expansion coefficients of GaAs and Si, a compressive strain is still present at room temperature for these thin GaAs/Si films.

  2. High-power pulsed lasers

    SciTech Connect

    Holzrichter, J.F.

    1980-04-02

    The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization.

  3. Gas and metal vapor lasers and applications; Proceedings of the Meeting, Los Angeles, CA, Jan. 22, 23, 1991

    NASA Astrophysics Data System (ADS)

    Kim, Jin J.; Tittel, Frank K.

    Various papers on gas and metal vapor lasers and applications are presented. Individual topics addressed include: high-power copper vapor laser development, modified off-axis unstable resonator for copper vapor laser, industrial applications of metal vapor lasers, newly developed excitation circuit for kHz pulsed lasers, copper vapor laser precision processing, development of solid state pulse power supply for copper vapor laser, multiple spectral structure of the 578.2-nm line for copper vapor laser, adsorption of bromine in CuBr laser, processing of polytetrafluoroethylene with high-power VUV laser radiation, characterization of a subpicosecond XeF(C - A) excimer laser, X-ray preionization for high-repetition-rate discharge excimer lasers. Also discussed are: investigation of microwave-pumped excimer and rare-gas laser transitions, influence of gas composition of XeCl laser performance, output power stabilization of a XeCl excimer laser by HCl gas injection, excimer laser machining of optical fiber taps, diagnostics of a compact UV-preionized XeCl laser with BCl3 halogen donor, blackbody-pumped CO32 lasers using Gaussian and waveguide cavities, chemical problems of high-power sealed-off CO lasers, laser action of Xe and Ne pumped by electron beam, process monitoring during CO2 laser cutting, double-pulsed TEA CO2 laser, superhigh-gain gas laser, high-power ns-pulse iodine laser provided with SBS mirror. (No individual items are abstracted in this volume)

  4. Excimer laser deinsulation of Parylene-C on iridium for use in an activated iridium oxide film-coated Utah electrode array

    PubMed Central

    Yoo, Je-Min; Negi, Sandeep; Tathireddy, Prashant; Solzbacher, Florian; Song, Jong-In; Rieth, Loren W.

    2013-01-01

    Implantable microelectrodes provide a measure to electrically stimulate neurons in the brain and spinal cord and record their electrophysiological activity. A material with a high charge capacity such as activated or sputter-deposited iridium oxide film (AIROF or SIROF) is used as an interface. The Utah electrode array (UEA) uses SIROF for its interface material with neural tissue and oxygen plasma etching (OPE) with an aluminium foil mask to expose the active area, where the interface between the electrode and neural tissue is formed. However, deinsulation of Parylene-C using OPE has limitations, including the lack of uniformity in the exposed area and reproducibility. While the deinsulation of Parylene-C using an excimer laser is proven to be an alternative for overcoming the limitations, the iridium oxide (IrOx) suffers from fracture when high laser fluence (>1000 mJ/cm2) is used. Iridium (Ir), which has a much higher fracture resistance than IrOx, can be deposited before excimer laser deinsulation and then the exposed Ir film area can be activated by electrochemical treatment to acquire the AIROF. Characterisation of the laser-ablated Ir film and AIROF by surface analysis (X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscope) and electrochemical analysis (electrochemical impedance spectroscopy, and cyclic voltammetry) shows that the damage on the Ir film induced by laser irradiation is significantly less than that on SIROF, and the AIROF has a high charge storage capacity. The results show the potential of the laser deinsulation technique for use in high performance AIROF-coated UEA fabrication. PMID:23458659

  5. Microhollow Cathode Discharge Excimer Lamps

    NASA Astrophysics Data System (ADS)

    Schoenbach, K. H.

    1999-11-01

    character. Reducing the diameter of the cathode hole in a hollow cathode discharge geometry to values on the order of 100 μm has allowed us to extend the pressure range of stable, direct current hollow cathode gas discharges up to atmospheric pressure. The large concentration of high-energy electrons generated in the cathode fall, in combination with the high neutral gas density favors three-body processes such as excimer formation. Excimer emission in xenon discharges peaking at 172 nm, was observed with efficiencies between 6% and 9% at pressures of several hundred Torr. Typical forward voltages are 200 V at dc currents up to 8 mA. Pulsed operation allowed us to extend the current range to 80 mA with corresponding linear increase in optical power. Spatially resolved measurements showed that the source of the excimer radiation at atmospheric pressure and currents of less than 8 mA is confined to the cathode opening. The radiative emittance at 8 mA and atmospheric pressure is approximately 20 W/cm^2. With reduced pressure and increased current, respectively, the excimer source extends into the area outside the cathode hole. Besides in xenon, excimer emission in argon at a peak wavelength of 128 nm has been recorded. In addition to operating the discharge in rare gases, we have also explored its use as rare gas-halide excimer source. In a gas mixture containing 1% ArF we were able to generate stable dc discharges in flowing gas at pressures ranging from 100 Torr to atmospheric pressure. The spectra of the high-pressure ArF discharges are dominated by excimer radiation peaking at 193 nm. The excimer emission of a single ArF discharge at 700 Torr was measured as 150 mW at an efficiency of 3%. Parallel operation of these discharges by means of a resistive anode, which has recently been demonstrated for argon discharges, offers the possibility to use microhollow cathode discharge arrays as dc-excimer lamps, with estimated power densities exceeding 10 W/cm^2. abstract

  6. Excimer laser produced plasmas in copper wire targets and water droplets

    NASA Technical Reports Server (NTRS)

    Song, Kyo-Dong; Alexander, D. R.

    1994-01-01

    Elastically scattered incident radiation (ESIR) from a copper wire target illuminated by a KrF laser pulse at lambda = 248 nm shows a dinstinct two-peak structure which is dependent on the incident energy. The time required to reach the critical electron density (n(sub c) approximately = 1.8 x 10(exp 22) electrons/cu cm) is estimated at 11 ns based on experimental results. Detailed ESIR characteristics for water have been reported previously by the authors. Initiation of the broadband emission for copper plasma begins at 6.5 +/- 1.45 ns after the arrival of the laser pulse. However, the broadband emission occurs at 11 +/- 0.36 ns for water. For a diatomic substance such as water, the electron energy rapidly dissipates due to dissociation of water molecules, which is absent in a monatomic species such as copper. When the energy falls below the excitation energy of the lowest electron state for water, it becomes a subexcitation electron. Lifetimes of the subexcited electrons to the vibrational states are estimated to be of the order of 10(exp -9) s. In addition, the ionization potential of copper (440-530 nm) is approximately 6 eV, which is about two times smaller than the 13 eV ionization potential reported for water. The higher ionization potential contributes to the longer observed delay time for plasma formation in water. After initiation, a longer time is required for copper plasma to reach its peak value. This time delay in reaching the maximum intensity is attributed to the energy loss during the interband transition in copper.

  7. Fast iterative technique for the calculation of frequency dependent gain in excimer laser amplifiers

    SciTech Connect

    Sze, R.C.

    1991-01-01

    The motivation in initiating these calculations is to allow us to observe the frequency evolution of a laser pulse as it propagates through an amplifier and then through a sequence of amplifiers. The question we seek to answer is what pulse shape do we need to produce out of a front-end oscillator so that after it propagates through the whole Aurora KrF fusion amplifier chain will result in high energy, broad-band laser fields of a given bandwidth that can be focussed onto a fusion target. The propagation of a single frequency source through an amplifier with distributed loss was considered by Rigrod and was significantly expanded by Hunter and Hunter. The latter included amplified spontaneous emission (ASE) considerations both in the direction of and transverse to the coherent field. Analytic solutions that include forward and backward prapagating fields and ASE were derived which were transcendental in nature but allowed for fairly easy computer calculations. Transverse ASE were calculated using the unsaturated gain resulting from longitudinal fields and were used to compare this with the longitudinal field equations. Large computer programs are now available at LANL which include the influence of transverse ASE on the longitudinal fields. However, none of these considerations have worried about the changes in the frequency characteristics of the propagating field or of how each of the frequency field components contributes to the saturation of the gain. The inclusion of full frequency characteristics to the analytic solutions of Hunter and Hunter proved impossible at least for this author and a new calculational technique was developed and is the subject of this talk.

  8. Laser powered interorbital vehicle

    NASA Technical Reports Server (NTRS)

    Clarke, M. T.; Cooper, J. J.; Eggleston, G. P.; Farkas, M. A.; Hunt, D. C.; King, J.; Nguyen, H.; Rahal, G.; Saw, K.; Tipton, R.

    1989-01-01

    A preliminary design of a low-thrust Laser Powered Interorbital Vehicle (LPIV) intended for cargo transportation between an Earth space station and a lunar base is presented. The selected mission utilizes a spiral trajectory, characteristic of a low-thrust spacecraft, requiring eight days for a lunar rendezvous and an additional nine days for return. The ship's configuration consists primarily of an optical train, two hydrogen plasma engines, a 37.1 m box-beam truss, a payload module, and propellant tanks. The total mass of the vehicle, fully loaded, is 63,300 kg. A single plasma, regeneratively cooled engine design is incorporated into the two 500 N engines. These are connected to the spacecraft by turntables that allow the vehicle to thrust tangential to the flight path. Proper collection and transmission of the laser beam to the thrust chambers is provided through the optical train. This system consists of a 23-m-diameter primary mirror, a convex parabolic secondary mirror, a beam splitter, and two concave parabolic tertiary mirrors. The payload bay is capable of carrying 18,000 kg of cargo and is located opposite the primary mirror on the main truss. Fuel tanks carrying a maximum of 35,000 kg of liquid hydrogen are fastened to tracks that allow the tanks to be moved perpendicular to the main truss. This capability is required to prevent the center of mass from moving out of the thrust vector line. The laser beam is located and tracked by means of an acquisition, pointing, and tracking system that can be locked onto the space-based laser station. Correct orientation of the spacecraft with the laser beam is maintained by control moment gyros and reaction control rockets. In addition, an aerobrake configuration was designed to provide the option of using the atmospheric drag in place of propulsion for a return trajectory.

  9. Very high average power solid-state lasers pumped by remotely located nuclear-driven fluorescers

    NASA Astrophysics Data System (ADS)

    Boody, F. P.; Prelas, M. A.

    A total system efficiency of 3 percent is calculated for very high average power active mirror solid-state laser amplifiers of Nd,Cr:GSGG, pumped by remotely generated visible nuclear-driven alkali metal excimer fluorescence. The fluorescence is transported around a radiation shield, separating the fluorescer and the laser, by a large diameter-to-length ratio hollow lightpipe. Parameters are presented for a system producing 1-ms-long 12 MW pulses at 1 Hz, for an average power output of 12 kW.

  10. Simultaneous fluorescence and breakdown spectroscopy of fresh and aging transformer oil immersed in paper using ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Parvin, P.; Shoursheini, S. Z.; Khalilinejad, F.; Bavali, A.; Moshgel Gosha, M.; Mansouri, B.

    2012-11-01

    HV transformers are taken into account as the heart of the power distribution system. The on-line monitoring based on the oil analysis offers a rapid diagnostic technique to detect the probable faults. In fact, the transformer malfunctions can be detected using UV laser spectroscopic methods. Here, a novel technique is presented based on simultaneous laser induced fluorescence (LIF) and laser induced breakdown (LIB) spectroscopy for hyper sensitive identification of the oil degradation. Oil is mainly degraded due to the internal transformer faults such as overheating and partial discharge. The spectroscopic characteristics of oil in paper substrate were obtained due to ArF laser irradiation. It was shown that the amplitude of fluorescence signal increases when the oil suffers aging and degradation. A couple of additional characteristic carbon and Hα emissions appear in the corresponding breakdown spectra too.

  11. Microhollow Cathode Discharge Excimer Lamps

    NASA Astrophysics Data System (ADS)

    Schoenbach, Karl H.

    1999-10-01

    Reducing the diameter of the cathode hole in hollow cathode discharge geometry to values on the order of 100 μm has allowed us to extend the pressure range of stable, direct current hollow cathode discharges up to atmospheric pressure. The large concentration of high-energy electrons in the nonthermal discharge, in combination with the high neutral gas density favors three-body processes such as rare gas excimer formation. Excimer emission in argon and xenon discharges peaking at 130 nm and 172 nm, respectively, was observed with an efficiency for xenon excimer emission between 6% and 9% in a pressure range from 250 Torr and 450 Torr. Typical forward voltages are 200 V at dc currents of up to 8 mA. Pulsed operation allowed us to extend the current range in xenon discharges to 80 mA. At pressures in the hundreds of Torr range the source of the excimer radiation extends over an area of several times the cathode opening. With increasing pressure the source is reduced in size and eventually, at pressures exceeding atmospheric becomes confined to the cathode opening. For a specific pressure the radiative power increases linearly with current at constant radiant emittance. For atmospheric pressure discharges in xenon the radiative emittance is approximately 20 W/cm^2. In addition to operating the discharge in rare gases, we have also explored its use as rare gas-halide excimer source. In a gas mixture containing 1 % ArF we were able to generate stable dc discharges in flowing gas at pressures ranging from 100 Torr to atmospheric pressure. The spectra of the high-pressure ArF discharges are dominated by excimer radiation peaking at 193 nm. The excimer emission of an ArF discharge at 700 Torr was measured as 150 mW. With a discharge voltage of 500 V, and a current of 10 mA the efficiency is 3 %. Parallel operation of the micro-discharges by means of a resistive anode offers the possibility to use microhollow cathode discharge arrays as dc-excimer lamps, with estimated

  12. Laser power conversion system analysis

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Orbit to orbit and orbit to ground laser power conversion systems and power transfer are discussed. A system overview is presented. Pilot program parameters are considered: SLPS assumptions are listed, a laser SPS overview is presented, specifications are listed, and SLPS coats are considered.

  13. Utilization of the excimer laser and a moving piezoelectric mirror to accomplish the customized contact lens ablation to correct high-order aberrations

    NASA Astrophysics Data System (ADS)

    de Matos, Luciana; Yasuoka, Fátima M. M.; Schor, Paulo; de Oliveira, Enos; Bagnato, Vanderlei S.; Carvalho, Luis A. V.

    2014-02-01

    The use of the Hartman-Shack sensor in ophthalmology allowed the identification of higher-order aberrations, which make possible the search for methods to correct them. Customized refractive surgery is one of the most successful methods, although there are patients which cannot be submitted to this surgery due to a variety of abnormal limiting factors such as cornea thickness and quantity of higher-order aberrations. Being this an irreversible process, the alternative is to develop a non-surgical method. This work proposes a method to obtain personalized contact lenses to correct high-order aberrations via the development of a customized ablation system using an excimer laser and a moving piezoelectric mirror. The process to produce such lenses consists of four steps. 1) The map of total aberrations of the patient's eye is measured by using an aberrometer with a Hartman-Shack sensor. 2) The measured aberration map is used to determine the maps for correction and related distribution of laser pulses for the ablation process with the excimer laser. 3) The lens production is performed following the same principle as customized refractive surgery. 4) The quality control of the lens is evaluated by two tests. 4.1) The lens is measured by a non-commercial lensometer, which is assembled specially for this measurement, as the ones commercially available are not capable of measuring asymmetric and irregular surfaces. 4.2) The evaluation of the lens-eye system is made using the aberrometer of the first step in order to verify the residual aberrations. Here, the lenses are ablated with a customized refractive surgery system.

  14. Laser assisted deposition

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1983-01-01

    Applications of laser-based processing techniques to solar cell metallization are discussed. Laser-assisted thermal or photolytic maskless deposition from organometallic vapors or solutions may provide a viable alternative to photovoltaic metallization systems currently in use. High power, defocused excimer lasers may be used in conjunction with masks as an alternative to direct laser writing to provide higher throughput. Repeated pulsing with excimer lasers may eliminate the need for secondary plating techniques for metal film buildup. A comparison between the thermal and photochemical deposition processes is made.

  15. High-reflectivity Bragg gratings fabricated by 248-nm excimer laser holographic ablation in thin Ta2O5 films overlaid on glass waveguides

    NASA Astrophysics Data System (ADS)

    Pissadakis, S.; Zervas, M. N.; Reekie, L.; Wilkinson, J. S.

    We demonstrate strong Bragg grating reflection in Ta2O5 (tantalum pentoxide) thin films overlaid on potassium ion-exchanged channel waveguides in BK-7 glass, inscribed using 248-nm excimer laser holographic ablation. The experimental data presented are divided into two sections: the first section refers to the study of the grating ablation process of thin Ta2O5 films with respect to the exposure conditions, while the second focuses on the implementation of these relief gratings in functional waveguide devices. Firstly, experimental data on grating morphology versus exposure conditions, accomplished with scanning electron microscopy microscans, are presented. In the second section diffraction spectra for waveguide gratings are presented and analysed. Spectral notches in transmission of depth -18 dB for the TM polarisation were obtained from 16-mm-long gratings patterned in waveguides overlaid with a 105-nm-thick Ta2O5 film, using 50 pulses of 60-mJ/cm2 energy density.

  16. An excimer-based FAIMS detector for detection of ultra-low concentration of explosives

    NASA Astrophysics Data System (ADS)

    Chistyakov, Alexander A.; Kotkovskii, Gennadii E.; Sychev, Alexey V.; Perederiy, Anatoly N.; Budovich, V. L.; Budovich, D. V.

    2014-05-01

    A new method of explosives detection based on the field asymmetric ion mobility spectrometry (FAIMS) and ionization by an excimer emitter has been developed jointly with a portable detector. The excimer emitter differs from usual UVionizing lamps by mechanism of emitting, energy and spectral characteristics. The developed and applied Ar2-excimer emitter has the working volume of 1 cm3, consuming power 0.6 W, the energy of photons of about 10 eV (λ=126 nm), the FWHM radiation spectrum of 10 nm and emits more than 1016 photon per second that is two orders of magnitude higher than UV-lamp of the same working volume emits. This also exceeds by an order of magnitude the quantity of photons per second for 10-Hz solid state YAG:Nd3+ - laser of 1mJ pulse energy at λ=266 nm that is also used to ionize the analyte. The Ar2-excimer ionizes explosives by direct ionization mechanism and through ionization of organic impurities. The developed Ar2-excimer-based ion source does not require cooling due to low level discharge current of emitter and is able to work with no repair more than 10000 hrs. The developed excimer-based explosives detector can analyze both vapors and traces of explosives. The FAIMS spectra of the basic types of explosives like trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), dinitrotoluene (DNT), cyclotetramethylenetetranitramine (HMX), nitroglycerine (NG), pentaerythritol tetranitrate (PETN) under Ar2-excimer ionization are presented. The detection limit determined for TNT vapors equals 1x10-14 g/cm3, for TNT traces- 100 pg.

  17. Excimer emission from microhollow cathode argon discharges

    NASA Astrophysics Data System (ADS)

    Moselhy, Mohamed; Petzenhauser, Isfried; Frank, Klaus; Schoenbach, Karl H.

    2003-12-01

    Microhollow cathode discharges (MHCDs) operated in rare gases are sources of intense excimer emission. Of particular interest is argon, because of its relatively low cost and the short wavelength (128 nm) of its excimer emission. The measured internal efficiency, obtained in static argon at atmospheric pressure, was found to be on the order of 1%. Flowing argon through a direct current (DC) MHCD at atmospheric pressure caused the argon excimer internal efficiency to increase to 6%, indicating that the low efficiency in static argon is mainly due to impurities. Applying 10 ns pulses to the DC plasma resulted in an increase in excimer power from 30 mW DC to 180 mW peak power, at an efficiency of 5-6%. The increase in excimer power correlates with an increase in the electron density. For DC operation, electron densities of 1015 cm-3 were measured in atmospheric pressure argon micro-plasmas, which increased to values beyond 1016 cm-3 for nanosecond pulsed operation. This increase in electron density and excimer power is due to pulsed electron heating, an effect that has allowed us to raise the mean electron energy from 1 eV, for DC operation, to 2.25 eV in the pulsed mode.

  18. Fluorine Penetration into Amorphous SiO2 Glass at SF6 Atmosphere Using Q-Switched Nd:YAG and Excimer Laser Irradiations

    NASA Astrophysics Data System (ADS)

    Hamid Reza Dehghanpour,; Parviz Parvin,

    2010-07-01

    At low pressures up to 0.1 mbar, the evidence of simultaneous SF6 gas decomposition and the morphology alteration on amorphous SiO2 glass have been investigated using various laser irradiations at typical wavelengths, i.e., ultraviolet (UV; 193 nm), visible (532 nm), and near infrared (NIR; 1064 nm). The instrumental micro-analysis of the surface were carried out by a number of instruments such as laser breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), Rutherford back scattered spectroscopy (RBS), wavelength dispersive X-ray (WDX) mapping, energy dispersive X-ray (EDX) microanalysis and photo-spectrometry accordingly. It was shown that the excimer laser at shorter wavelengths induces microstructuring on glass mainly due to the surface UV photoablation and the subsequent collisional SF6 decomposition. Conversely, at the longer wavelengths such as the fundamental and second harmonic generation of a Q-switched Nd:YAG laser, the treatment of the target is done based on the micro-plasma induced ablation and the following electron-impact SF6 decomposition.

  19. Direct nuclear-powered lasers

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1983-01-01

    The development of direct nuclear pumped lasers is reviewed. Theoretical and experimental investigations of various methods of converting the energy of nuclear fission fragments to laser power are summarized. The development of direct nuclear pumped lasers was achieved. The basic processes involved in the production of a plasma by nuclear radiation were studied. Significant progress was accomplished in this area and a large amount of basic data on plasma formation and atomic and molecular processes leading to population inversions is available.

  20. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Rob; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This slide presentation reviews the power frequencies for the doubled fiber laser. It includes information on the 780 nm laser, second harmonic generation in one crystal, cascading crystals, the tenability of laser systems, laser cooling, and directions for future work.

  1. Characterization of excimer laser annealed polycrystalline Si1-xGex alloy thin films by x-ray diffraction and spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Yu, Guolin; Krishna, Kalaga Murali; Shao, Chunlin; Umeno, Masayoshi; Soga, Tetsuo; Watanabe, Junji; Jimbo, Takashi

    1998-01-01

    Thin films of Si1-xGex alloys of different compositions x have been deposited, on single-crystal Si (100) surface and glass substrates, by simple ion beam sputtering, at room temperature. Crystallization of these films has been done using excimer laser annealing. Structural and optical properties of as-deposited and annealed Si1-xGex alloy films are characterized by x-ray diffraction (XRD), uv-visible spectrophotometry, spectroscopic ellipsometry (SE), and Auger electron spectroscopy (AES). The as-deposited films, both on Si and glass, have been found to be amorphous by XRD. Polycrystalline nature of laser-annealed samples has been evidenced by both x-ray and SE measurements. The results of x-ray, uv-visible, AES, and SE are compared and discussed. The poly-Si1-xGex films were oriented predominantly to (111) and the grain sizes were determined from half-width of x-ray peaks. The compositions x of Si1-xGex films have been evaluated from the SE dielectric function ɛ(ω) data, using the second-derivative technique, and are found to be 0.23 and 0.36 for two different compositions. A detailed analysis of ɛ(ω) with the effective-medium theory has demonstrated the volume fraction of crystalline Si1-xGex increases with the increasing energy of laser irradiation.

  2. Magnetically induced pulser laser excitation

    SciTech Connect

    Taylor, R.S.; Leopold, K.E.

    1985-02-15

    A novel excitation scheme has been developed for excimer discharge lasers. The technique uses pulse transformer technology to induce a fast, high voltage pulse directly onto a ground potential laser electrode resulting in the breakdown of the laser gas mix. Saturation of the pulse transformer core inductance then permits efficient energy transfer from the main energy storage circuit into the discharge. When this excitation technique was used in a XeCl laser an output energy density of 2.5 J/l and an overall electrical to optical efficiency of 2% were obtained. The technique appears promising for the development of high energy, high average power excimer lasers.

  3. Series operation of direct current xenon chloride excimer sources

    NASA Astrophysics Data System (ADS)

    El-Habachi, Ahmed; Shi, Wenhui; Moselhy, Mohamed; Stark, Robert H.; Schoenbach, Karl H.

    2000-09-01

    Stable, direct current microhollow cathode discharges in mixtures of hydrochloric acid, hydrogen, xenon, and neon have been generated in a pressure range of 200-1150 Torr. The cathode hole diameter was 250 μm. Sustaining voltages range from 180 to 250 V at current levels of up to 5 mA. The discharges are strong sources of xenon chloride excimer emission at a wavelength of 308 nm. Internal efficiencies of approximately 3% have been reached at a pressure of 1050 Torr. The spectral radiant power at this pressure was measured as 5 mW/nm at 308 nm for a 3 mA discharge. By using a sandwich electrode configuration, consisting of five perforated, alternate layers of metal and dielectric, a tandem discharge—two discharges in series—could be generated. For an anode-cathode-anode configuration the excimer irradiance, recorded on the axis of the discharge, was twice as large as that of a single discharge. The extension of this basic tandem electrode structure to a multiple electrode configuration allows the generation of high irradiance excimer sources. Placing such a structure with a string of microhollow cathode discharge into an optical resonator promises to lead to a direct current microexcimer laser.

  4. Effect of excimer laser annealing on a-InGaZnO thin-film transistors passivated by solution-processed hybrid passivation layers

    NASA Astrophysics Data System (ADS)

    Bermundo, Juan Paolo; Ishikawa, Yasuaki; Fujii, Mami N.; Nonaka, Toshiaki; Ishihara, Ryoichi; Ikenoue, Hiroshi; Uraoka, Yukiharu

    2016-01-01

    We demonstrate the use of excimer laser annealing (ELA) as a low temperature annealing alternative to anneal amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) passivated by a solution-processed hybrid passivation layer. Usually, a-IGZO is annealed using thermal annealing at high temperatures of up to 400 °C. As an alternative to high temperature thermal annealing, two types of ELA, XeCl (308 nm) and KrF (248 nm) ELA, are introduced. Both ELA types enhanced the electrical characteristics of a-IGZO TFTs leading to a mobility improvement of ~13 cm2 V-1 s-1 and small threshold voltage which varied from ~0-3 V. Furthermore, two-dimensional heat simulation using COMSOL Multiphysics was used to identify possible degradation sites, analyse laser heat localization, and confirm that the substrate temperature is below 50 °C. The two-dimensional heat simulation showed that the substrate temperature remained at very low temperatures, less than 30 °C, during ELA. This implies that any flexible material can be used as the substrate. These results demonstrate the large potential of ELA as a low temperature annealing alternative for already-passivated a-IGZO TFTs.

  5. Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 nm With a Forced Convection Raman Cell

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey; Herring, G. C.

    2000-01-01

    Tunable radiation, at ultraviolet wavelengths, is produced by Raman shifting a modified 285-mJ ArF excimer laser. Multiple Stokes outputs are observed in H2, CH4, D2, N2, SF6, and CF4 (20, 22, 53, 21, 2.1, and 0.35 percent, respectively). Numbers in parentheses are the first Stokes energy conversion efficiencies. We can access 70 percent of the frequency range 42000-52000 cm (exp -1) (190-240 nm) with Stokes energies that vary from 0.2 microJoule to 58 mJ inside the Raman cell. By using 110 mJ of pump energy and D 2 , the tunable first Stokes energy varies over the 29-58 mJ range as the wavelength is tuned over the 204-206 nm range. Dependence on input energy, gas pressure, He mixture fraction, and circulation of the gas in the forced convection Raman cell is discussed; Stokes conversion is also discussed for laser repetition rates from 1 to 100 Hz. An empirical equation is given to determine whether forced convection can improve outputs for a given repetition rate.

  6. High power gas laser amplifier

    DOEpatents

    Leland, Wallace T.; Stratton, Thomas F.

    1981-01-01

    A high power output CO.sub.2 gas laser amplifier having a number of sections, each comprising a plurality of annular pumping chambers spaced around the circumference of a vacuum chamber containing a cold cathode, gridded electron gun. The electron beam from the electron gun ionizes the gas lasing medium in the sections. An input laser beam is split into a plurality of annular beams, each passing through the sections comprising one pumping chamber.

  7. CONFOCAL MICROSCOPY SYSTEM PERFORMANCE: LASER POWER MEASUREMENTS

    EPA Science Inventory

    Laser power abstract
    The reliability of the confocal laser-scanning microscope (CLSM) to obtain intensity measurements and quantify fluorescence data is dependent on using a correctly aligned machine that contains a stable laser power. The laser power test appears to be one ...

  8. Optics assembly for high power laser tools

    DOEpatents

    Fraze, Jason D.; Faircloth, Brian O.; Zediker, Mark S.

    2016-06-07

    There is provided a high power laser rotational optical assembly for use with, or in high power laser tools for performing high power laser operations. In particular, the optical assembly finds applications in performing high power laser operations on, and in, remote and difficult to access locations. The optical assembly has rotational seals and bearing configurations to avoid contamination of the laser beam path and optics.

  9. Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds.

    PubMed

    Rowthu, Sriharitha; Böhlen, Karl; Bowen, Paul; Hoffmann, Patrik

    2015-11-11

    Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up

  10. Excimer laser in myocardial infarction: a comparison between STEMI patients with established Q-wave versus patients with non-STEMI (non-Q).

    PubMed

    Topaz, On; Ebersole, Douglas; Dahm, Johannes B; Alderman, Edwin L; Madyoon, Hooman; Vora, Kishor; Baker, John D; Hilton, David; Das, Tony

    2008-01-01

    Patients sustaining acute myocardial infarction (AMI) often require urgent percutaneous revascularization within the first 24 h from onset of the infarction due to continuous ischemia and hemodynamic instability. Upon arrival to the cardiac catheterization, the electrocardiogram of AMI patients may exhibit acute ST-elevation (STEMI) with or without accompanying Q-wave or depression of the ST segment (non-STEMI or non-Q-wave infarction). Data comparing acute outcome of device application in patients presenting for urgent revascularization with established Q-wave myocardial infarction (QWMI) versus those with non-STEMI (NQMI) are sparse. Excimer laser is a revascularization modality applied for debulking of atherosclerotic plaque and vaporization of associated thrombus in the setting of AMI. One hundred fifty-one AMI patients with continuous chest pain and ischemia who enrolled into a multicenter study and underwent urgent revascularization were divided for the purpose of a retrospective analysis into two groups. One group presented with established electrocardiographic Q-wave, whereas the other had ST-depression (NQMI). In comparison with the NQMI group, the QWMI patients had a higher incidence of failed thrombolytic therapy (17% vs 3, p = 0.006), cardiogenic shock (20 vs 6%, p = 0.01), left anterior descending as a culprit infarct-related vessel (46 vs 14%, p < 0.0001), a higher incidence of TIMI 0 flow (48 vs 24%, p = 0.04), a heavier thrombus burden (grade 4 TIMI thrombus, 58 vs 23%; p = 0.0001), and higher CPK (1272 +/- 2180 vs 404 +/- 577, p = 0.001) and troponin levels (62 +/- 95 vs 14 +/- 48, p = 0.0003). Both groups underwent laser angioplasty and stenting for relief of continuous chest pain and ischemia within 24 h of infarction onset. Quantitative coronary arteriography in an independent core laboratory measured similar improvement in baseline minimal luminal diameter and percent diameter stenosis by application of laser energy in both groups. Among the

  11. Laser Powered Aircraft Takes Flight

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A team of NASA researchers from Marshall Space Flight Center (MSFC) and Dryden Flight Research center have proven that beamed light can be used to power an aircraft, a first-in-the-world accomplishment to the best of their knowledge. Using an experimental custom built radio-controlled model aircraft, the team has demonstrated a system that beams enough light energy from the ground to power the propeller of an aircraft and sustain it in flight. Special photovoltaic arrays on the plane, similar to solar cells, receive the light energy and convert it to electric current to drive the propeller motor. In a series of indoor flights this week at MSFC, a lightweight custom built laser beam was aimed at the airplane `s solar panels. The laser tracks the plane, maintaining power on its cells until the end of the flight when the laser is turned off and the airplane glides to a landing. The laser source demonstration represents the capability to beam more power to a plane so that it can reach higher altitudes and have a greater flight range without having to carry fuel or batteries, enabling an indefinite flight time. The demonstration was a collaborative effort between the Dryden Center at Edward's, California, where the aircraft was designed and built, and MSFC, where integration and testing of the laser and photovoltaic cells was done. Laser power beaming is a promising technology for consideration in new aircraft design and operation, and supports NASA's goals in the development of revolutionary aerospace technologies. Photographed with their invention are (from left to right): David Bushman and Tony Frackowiak, both of Dryden; and MSFC's Robert Burdine.

  12. Propagation of the shock wave generated from excimer laser heating of aluminum targets in comparison with ideal blast wave theory

    NASA Astrophysics Data System (ADS)

    Jeong, S. H.; Greif, R.; Russo, R. E.

    1998-05-01

    Propagation of the shock wave generated during pulsed laser heating of aluminum targets was measured utilizing a probe beam deflection technique. The transit time of the laser-generated shock wave was compared with that predicted from the Sedov-Taylor solution for an ideal spherical blast wave. It was found that the most important parameters for the laser-generated shock wave to be consistent with the theoretically predicted propagation are the ambient pressure and the laser beam spot size. The prediction for laser energy conversion into the laser-induced vapor flow using the Sedov-Taylor solution overestimated the energy coupling efficiency, indicating a difference between a laser-induced gas-dynamic flow and an ideal blast wave.

  13. Phased laser array for generating a powerful laser beam

    DOEpatents

    Holzrichter, John F.; Ruggiero, Anthony J.

    2004-02-17

    A first injection laser signal and a first part of a reference laser beam are injected into a first laser element. At least one additional injection laser signal and at least one additional part of a reference laser beam are injected into at least one additional laser element. The first part of a reference laser beam and the at least one additional part of a reference laser beam are amplified and phase conjugated producing a first amplified output laser beam emanating from the first laser element and an additional amplified output laser beam emanating from the at least one additional laser element. The first amplified output laser beam and the additional amplified output laser beam are combined into a powerful laser beam.

  14. Nano-crystallization in ZnO-doped In2O3 thin films via excimer laser annealing for thin-film transistors

    NASA Astrophysics Data System (ADS)

    Fujii, Mami N.; Ishikawa, Yasuaki; Ishihara, Ryoichi; van der Cingel, Johan; Mofrad, Mohammad R. T.; Bermundo, Juan Paolo Soria; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Uraoka, Yukiharu

    2016-06-01

    In a previous work, we reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

  15. Intraocular microablation of choroidal tissue by a 308 nm AIDA excimer laser for RPE-transplantation in patients with age-related macular degeneration.

    PubMed

    Holz, F G; Bindewald, A; Schutt, F; Specht, H

    2003-04-01

    Age-related macular degeneration (AMD) is the leading cause of legal blindness in the western nations beyond 50 years of age. The most frequent cause for severe visual loss is the growth of neovascular membrances from the choroid into the subretinal space. This usually results in irreversible degeneration of the overlying retina. Surgical removal of the membrane is feasible, however, usually results in functional loss of apposing retinal photoreceptors since retinal pigment epithelial (RPE) cells are removed concurrently due to their tight adherence to the neovascular complex. Therefore, various attempts have been undertaken to fill the resulting RPE cell defect with either heterologous or autologous RPE cell transplants. So far cell survival, function and subsequent visual function has been disappointing. To minimize trauma and resulting dedifferentiation harvesting in the eye and transplantation in whole sheets and without temporary removal from the eyes would be desirable. This may be achieved by isolating grafts consisting of choroid, Bruch's membrance and RPE cells from the peripheral retina and transplantation of this graft under the neurosensory retina after removal of the choroidal neovascularization. However, the choroidal component of such a graft would be expected to interfere with diffusion of metabolites to and from the retina. Therefore, outcome would be expected to be better if the choroidal tissue would be removed before translocation. In preclinical experiments we used a 308 nm UV AIDA excimer laser to microablate choroidal tissue from such a graft in human donor eyes. PMID:12749285

  16. Preliminary results of tracked photorefractive keratectomy (T-PRK) for mild to moderate myopia with the autonomous technologies excimer laser at Cedars-Sinai Medical Center

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; Nesburn, Anthony B.

    1997-05-01

    Preliminary results of the correction of myopia up to -7.00 D by tracked photorefractive keratectomy (T-PRK) with a scanning and tracking excimer laser by Autonomous Technologies are discussed. 41 eyes participated (20 males). 28 eyes were evaluated one month postop. At epithelization day mean uncorrected vision was 20/45.3. At one month postop, 92.8 of eyes were 20/40 and 46.4% were 20/20. No eye was worse than 20/50. 75% of eyes were within +/- 0.5 D of emmetropia and 82% were within +/- 1.00 D of emmetropia. Eyes corrected for monovision were included. One eye lost 3 lines of best corrected vision, and had more than 1.00 D induced astigmatism due to a central corneal ulcer. Additional complications included symptomatic recurrent corneal erosions which were controlled with topical hypertonic saline. T-PRK appears to allow effective correction of low to moderate myopia. Further study will establish safety and efficacy of the procedure.

  17. The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

    SciTech Connect

    Kahn, E. H.; Langford, S. C.; Dickinson, J. T.; Boatner, Lynn A

    2013-01-01

    We report mass-resolved time-of-flight measurements of neutral particles from the surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

  18. Continuous high-power gas lasers

    NASA Technical Reports Server (NTRS)

    Hertzberg, A.

    1979-01-01

    High power gas laser concepts are discussed with emphasis on the role that fluid mechanics has played in their development. Consideration is given to three types of systems: gasdynamic lasers, HF supersonic diffusion lasers, and electric discharge lasers. Flow effects and aerodynamic windows in such lasers are briefly described. Future directions of research are outlined.

  19. Hybrid high power femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Resan, Bojan

    2016-03-01

    There is a growing demand for ultrafast laser systems with high average power and repetition rate. We present two hybrid master oscillator power amplifier (MOPA) architectures employing variety of available technologies to achieve 100 W average power femtosecond pulses. We achieved 120 W 820 fs pulses using solid-state oscillator and fiber amplifiers and chirped pulse amplification (CPA) technique (10 μJ pulse energy at 10 MHz and 100 μJ at 400 kHz). In the second experiment, we achieved 160 W 800 fs pulses in a compact system without the standard CPA using solidstate oscillator and single crystal fiber amplifiers. As currently every component experiences some limitations, it is a challenge to choose the optimal architecture with associated components to achieve a desired combination of laser output parameters.

  20. Excimer Emission from Argon Microhollow Cathode Discharges

    NASA Astrophysics Data System (ADS)

    Moselhy, Mohamed; Schoenbach, Karl H.

    2002-10-01

    Excimer emission from direct current microhollow cathode discharges had been studied for rare gases and mixtures of rare gases and halides as working gases [1]. In static xenon, the dc efficiency was measured as 6%-9%. In static argon, however, the efficiency is only on the order of 1%. This relatively low value was found to be due to excimer quenching processes caused by impurities. By flowing the argon, rather than operating under static conditions we could increase the efficiency to 6%. Applying a 10 ns pulse of 600 V to the DC discharge in argon resulted in an increased intensity by a factor of six. The decay time for argon excimer emission was found to be 500 ns, indicating that quenching processes even with purging of the discharge chamber are still more effective by a factor of six in depopulating the excimer level than excimer radiation. The major quenching effect is based on resonant energy transfer from the argon excimer to atomic oxygen [2]. The addition of small amounts of oxygen allowed us therefore to convert the argon excimer emission centered at 128 nm into narrowband emission at 130.4 nm (oxygen triplet) with an optical power of up to 13 mW.This material was supported by NSF (CTS-0078618).[1] Karl H. Schoenbach, Ahmed El-Habachi, Mohamed M. Moselhy, Wenhui Shi, and Robert H. Stark, Physics of Plasmas 7, 2186 (2000). [2] M. Moselhy, R.H. Stark, K.H. Schoenbach, and U. Kogelschatz, Appl. Phys. Lett. 78, 880 (2001).

  1. High power laser apparatus and system

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.; Brandhorst, H. W., Jr. (Inventor)

    1975-01-01

    A high-power, continuous-wave laser was designed for use in power transmission and energy-collecting systems, and for producing incoherent light for pumping a laser material. The laser has a high repetitive pulsing rate per unit time, resulting in a high-power density beam. The laser is composed of xenon flash tubes powered by fast-charging capacitors flashed in succession by a high-speed motor connected to an automobile-type distributor.

  2. Potential converter for laser-power beaming

    NASA Technical Reports Server (NTRS)

    Walker, Gilbert H.; Williams, Michael D.; Schuster, Gregory L.; Iles, Peter A.

    1991-01-01

    Future space missions, such as those associated with the Space Exploration Initiative (SEI), will require large amounts of power for operation of bases, rovers, and orbit transfer vehicles. One method for supplying this power is to beam power from a spaced based or Earth based laser power station to a receiver where laser photons can be converted to electricity. Previous research has described such laser power stations orbiting the Moon and beaming power to a receiver on the surface of the Moon by using arrays of diode lasers. Photovoltaic converters that can be efficiently used with these diode lasers are described.

  3. Application of high power lasers to space power and propulsion

    NASA Technical Reports Server (NTRS)

    Nored, D. L.

    1976-01-01

    The transmission of laser power over long distances for applications such as direct conversion to propulsive thrust or electrical power is considered. Factors discussed include: problems inherent in transmitting, propagating, and receiving the laser beam over long ranges; high efficiency, closed-cycle, continuous wave operation; advancement of CO2 laser technology; and compatibility with photovoltaic power conversion devices.

  4. Removal of Metal-Oxide Layers Formed on Stainless and Carbon Steel Surfaces by Excimer Laser Irradiation in Various Atmospheres

    SciTech Connect

    Kameo, Yutaka; Nakashima, Mikio; Hirabayashi, Takakuni

    2002-02-15

    To apply the laser ablation technique for decontamination of metal wastes contaminated with radioactive nuclides, the effect of irradiation atmospheres on removal of oxide layers on steel surfaces by laser ablation was studied. Based on the assumption that the absorption of laser light follows the Lambert-Beer law, ablation parameters, such as absorption length and threshold fluence for ablation, of sintered Fe{sub 2}O{sub 3} and stainless and carbon steels were measured in He, O{sub 2}, Kr, or SF{sub 6} atmospheres. The results indicated that SF{sub 6} was the most effective gas of all irradiation atmospheres studied for the exclusive removal of oxide layers formed on stainless and carbon steel samples in high-temperature pressurized water. Secondary ion mass spectroscopic measurement and scanning electron microscopic observation confirmed that no oxide layer existed on the steel samples after the exclusive removal with laser irradiation.

  5. High Power Free Electron Lasers

    SciTech Connect

    George Neil

    2004-04-12

    FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free Electron Lasers and electron/photon interactions but as a workhorse of scientific research. The characteristics that have driven the development of these sources are the desire for high peak and average power, high pulse energies, wavelength tunability, timing flexibility, and wavelengths that are unavailable from more conventional laser sources. User programs have been performed using such sources encompassing medicine, biology, solid state research, atomic and molecular physics, effects of non-linear fields, surface science, polymer science, pulsed laser vapor deposition, to name just a few. Recently the incorporation of energy recovery systems has permitted extension of the average power capabilities to the kW level and beyond. Development of substantially higher power systems with applications in defense and security is believed feasible with modest R&D efforts applied to a few technology areas. This paper will discuss at a summary level the physics of such devices, survey existing and planned facilities, and touch on the applications that have driven the development of these popular light sources.

  6. Excimer laser activation of ultra-shallow junctions in doped Si: Modeling, experiments and real time process monitoring

    NASA Astrophysics Data System (ADS)

    Semmar, Nadjib; Darif, Mohamed; Millon, Eric; Petit, Agnès; Etienne, Hasnaa; Delaporte, Philippe

    2012-07-01

    This work concerns the ALDIP (Laser Activation of Doping agents Implanted by Plasma immersion) project that was a successful collaboration with Ion Beam Services (IBS) corporation, the "Lasers, Plasmas and Photonic Processes" (LP3) laboratory and the GREMI laboratory. The aim of this work is to control the melted thickness (i.e. junction thickness in the range 10-100 nm) by the Real Time Reflectivity (TRR) monitoring during the Laser Thermal Processing (LTP). The LTP is achieved by using a KrF laser beam (248 nm, 27 ns) with a homogeneous 'Top-Hat' space distribution to induce a selective melting and the resolidification of the doped Si:B samples on few nanometers. This recrystallization is conducted here after the pre-amorphisation process resulting from the ionic implantation of Si (PIII IBS implanter). Thus, all the studied samples are partially amorphized and boron doped. TRR method allows the accurate evaluation of the melting threshold, the duration of the melting phase, and the maximum melted thickness. Obtained results versus laser fluence are shown in the new case of under vacuum treatment. In order to calibrate the TRR method (to determine the intensity and the profile of the TRR signal versus the melting depth), we have used the secondary ion mass spectrometry (TOF-SIMS) analysis. This technique gives the doping agents profile versus the depth before and after LTP and confirms also the melting kinetics from TRR results.

  7. Formation of a photo-oxidized protective thin film with waterproof and high-power laser tolerance properties

    NASA Astrophysics Data System (ADS)

    Murahara, Masataka; Sato, Yuji; Funatsu, Takayuki; Jitsuno, Takahisa; Okamoto, Yoshiaki

    2008-10-01

    The organic silicone oil applied over the surface of a fused silica glass or Kaliumdihydrogenphosphat (KDP) nonlinear optical crystal was changed to an inorganic glass by the photochemical oxidization using a Xe2 excimer lamp in the air. As a result, the thin film acquired a characteristic of high power laser tolerance equivalent to quartz. Dimethylsiloxane silicone oil was spin-coated on the surfaces of a fused silica substrate and KDP to form a film of 100-nm thickness; which were irradiated with the Xe2 excimer lamp light (wavelength 172 nm, power density 10 mW/cm2) for 60 minutes in oxygen atmosphere. The films were further irradiated with the Nd: YAG laser of ω (1.06 μm) or 2ω (0.503 μm), and the laser damage test (J/cm2/10 ns) was conducted. The laser damage threshold of the photo-oxidized 100 nm thick film formed on the fused silica substrate was 72 J/cm2 in ω and 107 J/cm2 in 2ω. On the KDP substrate, the laser damage threshold of the thin film was 32.4J/cm2 in ω and 32.6 J/cm2 in 2ω.

  8. Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

    NASA Astrophysics Data System (ADS)

    Schaubroeck, David; De Smet, Jelle; Willems, Wouter; Cools, Pieter; De Geyter, Nathalie; Morent, Rino; De Smet, Herbert; Van Steenbeerge, Geert

    2016-07-01

    Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110 nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

  9. Formation of epitaxial metastable NiGe{sub 2} thin film on Ge(100) by pulsed excimer laser anneal

    SciTech Connect

    Lim, Phyllis S. Y.; Yeo, Yee-Chia; Chi, Dong Zhi; Lim, Poh Chong; Wang, Xin Cai; Chan, Taw Kuei; Osipowicz, Thomas

    2010-11-01

    Epitaxial nickel digermanide (NiGe{sub 2}), a metastable phase, was formed by laser annealing Ni on (100) germanium-on-silicon substrates. The NiGe{sub 2} formation was investigated using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and first-principles calculations. The formation mechanism of NiGe{sub 2} is discussed and is attributed to both the reduced interfacial energy at the NiGe{sub 2}/Ge(100) interface and the kinetic aspects of the laser annealing reaction associated with phase transformation and film agglomeration.

  10. Laser power conversion system analysis, volume 2

    NASA Technical Reports Server (NTRS)

    Jones, W. S.; Morgan, L. L.; Forsyth, J. B.; Skratt, J. P.

    1979-01-01

    The orbit-to-ground laser power conversion system analysis investigated the feasibility and cost effectiveness of converting solar energy into laser energy in space, and transmitting the laser energy to earth for conversion to electrical energy. The analysis included space laser systems with electrical outputs on the ground ranging from 100 to 10,000 MW. The space laser power system was shown to be feasible and a viable alternate to the microwave solar power satellite. The narrow laser beam provides many options and alternatives not attainable with a microwave beam.

  11. High power laser perforating tools and systems

    SciTech Connect

    Zediker, Mark S; Rinzler, Charles C; Faircloth, Brian O; Koblick, Yeshaya; Moxley, Joel F

    2014-04-22

    ystems devices and methods for the transmission of 1 kW or more of laser energy deep into the earth and for the suppression of associated nonlinear phenomena. Systems, devices and methods for the laser perforation of a borehole in the earth. These systems can deliver high power laser energy down a deep borehole, while maintaining the high power to perforate such boreholes.

  12. Master-Oscillator/Power-Amplifier Laser System

    NASA Technical Reports Server (NTRS)

    Yu, Anthony W.; Krainak, Michael A.; Unger, Glenn L.

    1994-01-01

    Master-oscillator/power-amplifier (MOPA) laser system operates in continuous-wave mode or in amplitude-modulation (e.g., pulse) mode by modulation of oscillator current. Power amplifier is laser-diode-pumped neodymium:yttrium lithium fluoride (Nd:YLF) laser; oscillator is laser diode. Offers relatively high efficiency and power. Because drive current to oscillator modulated, external electro-optical modulator not needed. Potential uses include free-space optical communications, coded laser ranging, and generation of high-power, mode-locked pulses.

  13. Preparation of periodic surface structures on doped poly(methyl metacrylate) films by irradiation with KrF excimer laser

    PubMed Central

    2014-01-01

    In this work, we describe laser modification of poly(methyl methacrylate) films doped with Fast Red ITR, followed by dopant exclusion from the bulk polymer. By this procedure, the polymer can be modified under extremely mild conditions. Creation of surface ordered structure was observed already after application of 15 pulses and 12 mJ cm−2 fluence. Formation of grating begins in the hottest places and tends to form concentric semi-circles around them. The mechanism of surface ordered structure formation is attributed to polymer ablation, which is more pronounced in the place of higher light intensity. The smoothness of the underlying substrate plays a key role in the quality of surface ordered structure. Most regular grating structures were obtained on polymer films deposited on atomically ‘flat’ Si substrates. After laser patterning, the dopant was removed from the polymer by soaking the film in methanol. PMID:25386106

  14. Independent assessment of laser power beaming options

    NASA Technical Reports Server (NTRS)

    Ponikvar, Donald R.

    1992-01-01

    Technical and architectural issues facing a laser power beaming system are discussed. Issues regarding the laser device, optics, beam control, propagation, and lunar site are examined. Environmental and health physics aspects are considered.

  15. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Robert J.; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This viewgraph presentation reports on the development of a high power 780 nm laser suitable for space applications of laser cooling. A possible solution is to use frequency doubling of high power 1560 nm telecom lasers. The presentation shows a diagram of the frequency conversion, and a graph of the second harmonic generation in one crystal, and the use of the cascading crystals. Graphs show the second harmonic power as a function of distance between crystals, second harmonic power vs. pump power, tunability of laser systems.

  16. Photorefractive keratectomy for myopia and myopic astigmatism correction using the WaveLight Allegretto Wave Eye-Q excimer laser system.

    PubMed

    Costa, Esmeralda; Franqueira, Nuno; Rosa, Andreia M; Tavares, Cristina; Quadrado, Maria J; Lobo, Conceição; Murta, Joaquim N

    2014-06-01

    To analyze photorefractive keratectomy (PRK) outcomes in myopia and myopic astigmatism correction using the WaveLight Allegretto Wave Eye-Q(®) excimer laser system (WaveLight Laser Technologie AG, Erlangen, Germany). 222 eyes of 151 patients underwent PRK (mean age 33.5 ± 6.8 years). Pre-operative best spectacle-corrected visual acuity (BSCVA) ranged from 0.4 to -0.1 logMAR (mean -0.03 ± 0.06). Mean spherical equivalent (SE) was -3.29 ± 1.20 D. Efficacy, predictability and safety were evaluated. Minimum follow-up was 3 months. Accountability at 3 and 6 months was 100 and 54 %, respectively (median follow-up 5 months, mean 5.2 ± 2.6 months). At 3 months, mean uncorrected visual acuity (UCVA) was -0.02 ± 0.07 logMAR, BSCVA -0.03 ± 0.05 logMAR, efficacy index 0.98 and safety index 1.02. UCVA was ≥20/16 in 40.1 %, ≥20/20 in 86.5 % and ≥20/25 in 98.2 %. Mean SE was -0.02 ± 0.20 D. Residual refractive error was ± 0.13 D in 81.5 %, ± 0.25 D in 88.7 % and ± 0.50 D in 97.7 %. At 6 months, outcomes were similar: mean UCVA was -0.02 ± 0.07 logMAR, BSCVA -0.03 ± 0.06 logMAR, efficacy index 1.00 and safety index 1.03. UCVA was ≥20/16 in 43.7 %, ≥20/20 in 86.6 % and ≥20/25 in 96.6 %. Mean SE was -0.02 ± 0.17 D. Residual refractive error was ± 0.13 D in 86.6 %, ± 0.25 D in 93.3 % and ± 0.50 D in 98.3 %. Refractive stability was achieved at 3 months. No patient lost more than one line of BSCVA. There were no retreatments. The WaveLight Allegretto Wave Eye-Q is effective, predictable and safe in low-to-moderate myopia and myopic astigmatism PRK correction.

  17. Development and numerical solution of a mechanistic model for corneal tissue ablation with the 193 nm argon fluoride excimer laser

    NASA Astrophysics Data System (ADS)

    Fisher, Brian T.; Hahn, David W.

    2007-02-01

    We detail the development and implementation of a global ablation model that incorporates a dynamically changing tissue absorption coefficient. Detailed spectroscopic measurements rule out plasma-shielding effects during the laser-tissue interaction and thereby support a photochemical mechanism. The model predicts ablation rate behavior that agrees well with a variety of experimental ablation rate data and that substantially deviates from a static Beer-Lambert model. The dynamic model predicts an enhancement in the tissue absorption coefficient of about 25%-50% as compared with the initial, static value. In addition, the model predicts an increase in the tissue ablation rate as corneal hydration increases, which may provide additional insight into variations in refractive surgery outcome.

  18. a Comparison of the Measured and Modelled Effects of Brewster Angle Anisotropies upon Pulsed Xenon Chloride Excimer Laser Output

    NASA Astrophysics Data System (ADS)

    Hahn, John Frederick

    We have demonstrated the effectiveness of stacked, fused-silica, intra-cavity Brewster angle plates in generating highly polarized XeCl^{*} laser output. Output polarization in excess of 95%, with coincident energy degradation of less than 20%, have been observed, data which compare favorably with results obtained with more sophisticated, more expensive intra-cavity laser polarizers (DOB 81). The optimal arrangement of the polarizing plates is shown to be at the rear of the cavity, near the mirror. We have observed the temporal development of the component pulses and the degree of polarization. For the optimal rear polarizer arrangements, the polarization has been shown to be large throughout the entire observable pulse. We have observed the dependence of the polarization upon the gas mixture pressure when weaker anisotropies are in place. We have developed a model to simulate the experimental results. The model is an innovative use of established rate equation techniques and also makes use of the short coherence length of XeCl* emissions to permit decoupling of the p- and s-plane polarization components. We thus avoid the more complicated semi-classical model which makes explicit use of the vector properties of the polarization components. We account for the presence of Brewster angle plates in the cavity as changes in the effective mirror/outcoupler reflectivities in the respective planes of polarization. We successfully simulate the output energy, E, the peak-to -peak polarization, {cal P}_ {o} and the temporally averaged polarization, |{cal P}, for the tested polarizer configurations. We attain only moderate success with our simulations of the temporally resolved polarizations. We use the model also to predict what operating conditions are required to successfully implement the use of Brewster angle end windows in generating highly polarized output.

  19. Super-high-frequency shielding properties of excimer-laser-synthesized-single-wall-carbon-nanotubes/polyurethane nanocomposite films

    SciTech Connect

    Aiessa, B.; Habib, M. A.; Denidni, T. A.; El Khakani, M. A.; Laberge, L. L.; Therriault, D.

    2011-04-15

    Electromagnetic shielding attenuation (ESA) properties of carbon nanotubes/polymer nanocomposite films, in the super high frequency (SHF) X-band (7-12 GHz) domain are studied. The nanocomposite films consisted of thermoset polyurethane (PU) resin blended with single-walled carbon nanotubes (SWCNTs) mats, and deposited on fused quartz substrates. Two different approaches were used to achieve the nanocomposite films, namely (i) through the on-substrate ''all-laser'' growth approach of SWCNTs directly onto substrate, followed by their infiltration by the PU resin, and (ii) by appropriately dispersing the chemically-purified SWCNTs (in the soot form) into the PU matrix and their subsequent deposition onto quartz substrates by means of a solvent casting process. Characterizations of the ESA properties of the developed nanocomposite films show that they exhibit systematically a deep shielding band, centered at around 9.5 GHz, with an attenuation as high as |- 30| dB, recorded for SWCNT loads of 2.5 wt. % and above. A direct correlation is established between the electrical conductivity of the nanocomposite films and their electromagnetic shielding capacity. The SWCNTs/PU nanocomposites developed here are highly promising shielding materials as SHF notch filters, as their ESA capacity largely exceeds the target value of |- 20| dB generally requested for commercial applications.

  20. Industrial application of high power disk lasers

    NASA Astrophysics Data System (ADS)

    Brockmann, Rüdiger; Havrilla, David

    2008-02-01

    Laser welding has become one of the fastest growing areas for industrial laser applications. The increasing cost effectiveness of the laser process is enabled by the development of new highly efficient laser sources, such as the Disk laser, coupled with decreasing cost per Watt. TRUMPF introduced the Disk laser several years ago, and today it has become the most reliable laser tool on the market. The excellent beam quality and output powers of up to 10 kW enable its application in the automotive industry as well as in the range of thick plate welding, such as heavy construction and ship building. This serves as an overview of the most recent developments on the TRUMPF Disk laser and its industrial applications like cutting, welding, remote welding and hybrid welding, too. The future prospects regarding increased power and even further improved productivity and economics are presented.

  1. High power laser beam delivery monitoring for laser safety

    NASA Astrophysics Data System (ADS)

    Corder, D. A.; Evans, D. R.; Tyrer, J. R.; Freeland, C. M.; Myler, J. K.

    1997-07-01

    The output of high power lasers used for material processing presents extreme radiation hazards. In normal operation this hazard is removed by the use of local shielding to prevent accidental exposure and system design to ensure efficient coupling of radiation into the workpiece. Faults in laser beam delivery or utilization can give rise to hazardous levels of laser radiation. A passive hazard control strategy requires that the laser system be enclosed such that the full laser power cannot burn through the housing under fault conditions. Usually this approach is too restrictive. Instead, active control strategies can be used in which a fault condition is detected and the laser cut off. This reduces the requirements for protective housing. In this work a distinction is drawn between reactive and proactive strategies. Reactive strategies rely on detecting the effects of an errant laser beam, whereas proactive strategies can anticipate as well as detect fault conditions. This can avoid the need for a hazardous situation to exist. A proactive strategy in which the laser beam is sampled at the final turning mirror is described in this work. Two control systems have been demonstrated; the first checks that beam power is within preset limits, the second monitors incoming beam power and position, and the radiation reflected back from the cutting head. In addition to their safety functions the accurate monitoring of power provides an additional benefit to the laser user.

  2. Piezoelectric measurement of laser power

    DOEpatents

    Deason, Vance A.; Johnson, John A.; Telschow, Kenneth L.

    1991-01-01

    A method for measuring the energy of individual laser pulses or a series of laser pulses by reading the output of a piezoelectric (PZ) transducer which has received a known fraction of the total laser pulse beam. An apparatus is disclosed that reduces the incident energy on the PZ transducer by means of a beam splitter placed in the beam of the laser pulses.

  3. Potential of laser for SPS power transmission

    NASA Technical Reports Server (NTRS)

    Bain, C. N.

    1978-01-01

    Research on the feasibility of using a laser subsystem as an additional option for the transmission of the satellite power system (STS) power is presented. Current laser work and predictions for future laser performance provide a level of confidence that the development of a laser power transmission system is technologically feasible in the time frame required to develop the SBS. There are significant economic advantages in lower ground distribution costs and a reduction of more than two orders of magnitude in real estate requirements for ground based receiving/conversion sites.

  4. High average power solid state laser power conditioning system

    SciTech Connect

    Steinkraus, R.F.

    1987-03-03

    The power conditioning system for the High Average Power Laser program at Lawrence Livermore National Laboratory (LLNL) is described. The system has been operational for two years. It is high voltage, high power, fault protected, and solid state. The power conditioning system drives flashlamps that pump solid state lasers. Flashlamps are driven by silicon control rectifier (SCR) switched, resonant charged, (LC) discharge pulse forming networks (PFNs). The system uses fiber optics for control and diagnostics. Energy and thermal diagnostics are monitored by computers.

  5. High power diode lasers for solid-state laser pumps

    NASA Technical Reports Server (NTRS)

    Linden, Kurt J.; Mcdonnell, Patrick N.

    1994-01-01

    The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

  6. High power diode lasers for solid-state laser pumps

    NASA Astrophysics Data System (ADS)

    Linden, Kurt J.; McDonnell, Patrick N.

    1994-02-01

    The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

  7. Spectroscopic analysis of electronically excited species in XeCl excimer laser-induced plasmas from the ablated high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/

    SciTech Connect

    Auciello, O.; Athavale, S.; Hankins, O.E.; Sito, M.; Schreiner, A.F.; Biunno, N.

    1988-07-04

    Optical spectroscopic analyses have been performed to study luminescence from plasmas produced by ablation of YBa/sub 2/Cu/sub 3/O/sub 7/ single-phase high T/sub c/ bulk superconductors exposed to XeCl excimer laser (308 nm) pulses. Only excited atomic neutral and single ionized species (CuCu/sup +/, BaBa/sup +/, YY/sup +/) were observed within the experimental resolution of an optical multichannel analyzer detection system, when irradiating the targets in vacuum (approx.10/sup -5/--10/sup -4/ Torr). Conspicuously absent in the spectra (300--800 nm range) are molecular emission bands that would appear if large excited molecules or fragments were present. Implications of the present results are discussed which relate to an early hypothesis about the laser ablation mechanism and their influence on high T/sub c/ film characteristics.

  8. The interaction of 193 nm excimer laser radiation with single-crystal zinc oxide: Generation of long lived highly excited particles with evidence of Zn Rydberg formation

    SciTech Connect

    Khan, Enamul H.; Langford, S. C.; Dickinson, J. T.; Boatner, L. A.

    2014-08-28

    In past studies, we have observed copious emissions of ionic and atomic Zn from single-crystal ZnO accompanying irradiation of single-crystal ZnO with 193-nm excimer laser irradiation at fluences below the onset of optical breakdown. The Zn{sup +} and ground state Zn° are studied using time-of-flight techniques and are mass selected using a quadrupole mass spectrometer. Simultaneously, we have observed emitted particles that are detectable with a Channeltron electron multiplier but cannot be mass selected. It is a reasonable hypothesis that these particles correspond to a neutral atom or molecule in highly excited long lived states. We provide strong evidence that they correspond to high lying Rydberg states of atomic Zn. We propose a production mechanism involving laser excitation via a two photon resonance excitation of Zn°.

  9. Energy coupling and plume dynamics during high power laser heating of metals

    SciTech Connect

    Jeong, S. |

    1997-05-01

    High power laser heating of metals was studied utilizing experimental and numerical methods with an emphasis on the laser energy coupling with a target and on the dynamics of the laser generated vapor flow. Rigorous theoretical modeling of the heating, melting, and evaporation of metals due to laser radiation with a power density below the plasma shielding threshold was carried out. Experimentally, the probe beam deflection technique was utilized to measure the propagation of a laser induced shock wave. The effects of a cylindrical cavity in a metal surface on the laser energy coupling with a solid were investigated utilizing photothermal deflection measurements. A numerical calculation of target temperature and photothermal deflection was performed to compare with the measured results. Reflection of the heating laser beam inside the cavity was found to increase the photothermal deflection amplitude significantly and to enhance the overall energy coupling between a heating laser beam and a solid. Next, unsteady vaporization of metals due to nanosecond pulsed laser heating with an ambient gas at finite pressure was analyzed with a one dimensional thermal evaporation model for target heating and one dimensional compressible flow equations for inviscid fluid for the vapor flow. Lastly, the propagation of a shock wave during excimer laser heating of aluminum was measured with the probe beam deflection technique. The transit time of the shock wave was measured at the elevation of the probe beam above the target surface; these results were compared with the predicted behavior using ideal blast wave theory. The propagation of a gaseous material plume was also observed from the deflection of the probe beam at later times.

  10. High power ultrashort pulse lasers

    SciTech Connect

    Perry, M.D.

    1994-10-07

    Small scale terawatt and soon even petawatt (1000 terawatt) class laser systems are made possible by application of the chirped-pulse amplification technique to solid-state lasers combined with the availability of broad bandwidth materials. These lasers make possible a new class of high gradient accelerators based on the large electric fields associated with intense laser-plasma interactions or from the intense laser field directly. Here, we concentrate on the laser technology to produce these intense pulses. Application of the smallest of these systems to the production of high brightness electron sources is also introduced.

  11. High-power laser chains used for laser isotope separation

    NASA Astrophysics Data System (ADS)

    Lompre, Louis A.

    2000-01-01

    Since 1985, France has chosen to focus on the selective photo-ionization process called SILVA for uranium enrichment. The general SILVA schedule has led to the construction of a pilot facility called ASTER, aimed to a general assessment of SILVA. It utilizes a mid power dye laser chain pumped by copper vapor laser chains. An alternative solution to pump dye laser is under development. It is based on high-power diode-pumped frequency doubled Nd:YAG modules. Performances as high as 150 Watts, at 532 nm, 10 kHz and pulse duration shorter than 75 ns have been obtained. The electrical efficiency overpasses 5 percent. The paper will give a description of the high power laser chains used or proposed for laser isotope separation.

  12. The interaction of 193-nm excimer laser radiation with single-crystal zinc oxide: The generation of atomic Zn line emission at laser fluences below breakdown

    SciTech Connect

    Khan, Enamul H.; Langford, S. C.; Dickinson, J. T.; Boatner, L. A.

    2013-08-28

    The production of gas phase atomic and ionic line spectra accompanying the high laser fluence irradiation of solid surfaces is well known and is most often due to the production and interaction of high densities of atoms, ions, and electrons generated from laser-induced breakdown. The resulting plasma expands and moves rapidly away from the irradiated spot and is accompanied by intense emission of light. This type of “plume” is well studied and is frequently exploited in the technique of chemical analysis known as laser induced breakdown spectroscopy. Here, we describe a similar but weaker emission of light generated in vacuum by the laser irradiation of single crystal ZnO at fluences well below breakdown; this emission consists entirely of optical line emission from excited atomic Zn. We compare the properties of the resulting laser-generated gas-phase light emission (above and below breakdown) and describe a mechanism for the production of the low-fluence optical emission resulting from a fortuitous choice of material and laser wavelength.

  13. Laser power beaming for satellite applications

    SciTech Connect

    Friedman, H.W.

    1993-09-22

    A serious consideration of laser power beaming for satellite applications appears to have grown out of a NASA mission analysis for transmitting power to lunar bases during the two week dark period. System analyses showed that laser power beaming to the moon in conjunction with efficient, large area solar cell collection panels, were an attractive alternative to other schemes such as battery storage and nuclear generators, largely because of the high space transportation costs. The primary difficulty with this scheme is the need for very high average power visible lasers. One system study indicated that lasers in excess of 10 MW at a wavelength of approximately 850 nm were required. Although such lasers systems have received much attention for military applications, their realization is still a long term goal.

  14. Scaling blackbody laser to high powers

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.

    1985-01-01

    Lasers pumped by solar heated blackbody cavities have potential for multimegawatt power beaming in space. There are two basic types of blackbody lasers; cavity pumped and transfer system. The transfer system is judged to be more readily scalable to high power. In this system, either N2 or CO is heated by the blackbody cavity then transferred into the laser cavity where CO2 is injected. The N2-CO2 system was demonstrated, but probably has lower efficiency than the CO-CO system. The characteristics of potential transfer laser systems are outlined.

  15. Solar powered blackbody-pumped lasers

    NASA Astrophysics Data System (ADS)

    Christiansen, Walter H.; Sirota, J. M.

    1991-02-01

    A concept for a solar-powered laser is presented which utilizes an intermediate blackbody cavity to provide a uniform optical pumping environment for the lasant, typically CO or CO2 or possibly a solid state laser medium. High power cw blackbody- pumped lasers with efficiencies on the order of 20 percent or more are feasible. The physical basis of this idea is reviewed. Small scale experiments using a high temperature oven as the optical pump have been carried out with gas laser mixtures. Detailed calculations showing a potential efficiency of 35 percent for blackbody pumped Nd:YAG system are discussed.

  16. ArF Excimer Emission from Microhollow Cathode Discharges

    NASA Astrophysics Data System (ADS)

    Shi, Wenhui; El-Habachi, Ahmed; Schoenbach, Karl H.

    1999-10-01

    Microhollow cathode discharges (MHCD) in Ar and Xe have been shown to emit excimer radiation at 128 nm and 172 nm, respectively, with an efficiency (in case of Xe) of approximately 8range towards longer wavelengths we have studied MHCD in argon fluoride mixtures (1to generate stable dc discharges in flowing gas at pressures ranging from 100 Torr to atmospheric pressure. The discharge voltage was approximately 500 V, the discharge current in these experiments was 10 mA. Whereas the spectrum at 300 Torr was dominated by atomic lines, at 700 Torr only excimer radiation peaking at 193 nm is observed in the spectral range from 120 nm to 300 nm. Absolute measurements of ArF excimer emission provided a value of approximately 3efficiency, or a total optical power of the excimer radiation of 150 mW. The peak power at 193 nm is 17 mW/nm. This is higher by a factor of 2 to 3, compared to xenon excimer emitters, due to the small FWHM of the 193nm ArF line (4 nm) compared to that of the Xe excimer line (24 nm). [1] Karl H. Schenbach, Ahmed El-Habachi, Wenhui Shi, and Marco Ciocca, Plasma Source Science and Technology 6, 468 (1997). [2] Ahmed El-Habachi and Karl H. Schoenbach, Appl.Phys.Lett. 73, 885 (1998). This work was funded by the DOE, Advanced Energy Division, and by the National Science Foundation.

  17. Bulk damage and absorption in fused silica due to high-power laser applications

    NASA Astrophysics Data System (ADS)

    Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

    2015-11-01

    Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and

  18. Excimer laser with fluoropolymer lining

    DOEpatents

    Sze, Robert C.

    1982-01-01

    A cavity formed of Teflon to provide extended static fill lifetimes for gases containing halogens. A double cavity configuration provides structural integrity to the inner Teflon cavity by maintaining an identical multi-atmospheric pressure within the outer structural cavity to minimize tension on the Teflon inner cavity. Use of a quantity of the lasing gas in the outer cavity or a constituent of that gas minimizes contamination of the lasing gas.

  19. Technology and engineering aspects of high power pulsed single longitudinal mode dye lasers

    NASA Astrophysics Data System (ADS)

    Rawat, V. S.; Mukherjee, Jaya; Gantayet, L. M.

    2015-09-01

    Tunable single mode pulsed dye lasers are capable of generating optical radiations in the visible range having very small bandwidths (transform limited), high average power (a few kW) at a high pulse repetition rate (a few tens of kHz), small beam divergence and relatively higher efficiencies. These dye lasers are generally utilized laser dyes dissolved in solvents such as water, heavy water, ethanol, methanol, etc. to provide a rapidly flowing gain medium. The dye laser is a versatile tool, which can lase either in the continuous wave (CW) or in the pulsed mode with pulse duration as small as a few tens of femtoseconds. In this review, we have examined the several cavity designs, various types of gain mediums and numerous types of dye cell geometries for obtaining the single longitudinal mode pulsed dye laser. Different types of cavity configuration, such as very short cavity, short cavity with frequency selective element and relatively longer cavity with multiple frequency selective elements were reviewed. These single mode lasers have been pumped by all kinds of pumping sources such as flash lamps, Excimer, Nitrogen, Ruby, Nd:YAG, Copper Bromide and Copper Vapor Lasers. The single mode dye lasers are either pumped transversely or longitudinally to the resonator axis. The pulse repletion rate of these pump lasers were ranging from a few Hz to a few tens of kHz. Physics technology and engineering aspects of tuning mechanism, mode hop free scanning and dye cell designs are also presented in this review. Tuning of a single mode dye laser with a resolution of a few MHz per step is a technologically challenging task, which is discussed here.

  20. Laser research and development in the Northeast; Proceedings of the Meeting, Cambridge, MA, Sept. 16, 17, 1986

    SciTech Connect

    Trainor, D.W.; Chicklis, E.P.

    1987-01-01

    The development and scaling of excimer lasers with emphasis on both electron-beam and discharge pumpings; a chemical means of generating laser action in the visible region; the use of stimulated Raman techniques to improve the beam quality output of systems employing excimer lasers; the research and development of CO/sub 2/ lasers; a CO/sub 2/ laser amplifier for radar applications; medical laser usage; and laser monitors for trace species in environmental and industrial processes are examined. Consideration is given to high power laser research and development for laser energetics; linear and nonlinear frequency converters; 450 nm laser operation in Tm(3+):YLF; alexandrite lasers and their applications; and the performance limitations of vibronic lasers. Topics discussed include the laser ignition of oil spills; the application of laser rangers to submunitions; the design and application of laser intensity stabilizers; and a 535 nm active atomic line filter that uses the Tl metastable state as an absorbing medium.

  1. Laser power conversion system analysis, volume 1

    NASA Technical Reports Server (NTRS)

    Jones, W. S.; Morgan, L. L.; Forsyth, J. B.; Skratt, J. P.

    1979-01-01

    The orbit-to-orbit laser energy conversion system analysis established a mission model of satellites with various orbital parameters and average electrical power requirements ranging from 1 to 300 kW. The system analysis evaluated various conversion techniques, power system deployment parameters, power system electrical supplies and other critical supplies and other critical subsystems relative to various combinations of the mission model. The analysis show that the laser power system would not be competitive with current satellite power systems from weight, cost and development risk standpoints.

  2. Anti-Reflective and Waterproof Hard Coating for High Power Laser Optical Elements

    NASA Astrophysics Data System (ADS)

    Murahara, Masataka; Yabe, Takashi; Uchida, Shigeaki; Yoshida, Kunio; Okamoto, Yoshiaki

    2006-05-01

    A hard coating method of single crystalline porous silica film is widely used for high power laser optical elements in the air. However, there is no protective hard coating method for the elements to survive high power laser irradiance while in the water. We, thus, developed a new method for a waterproof coating with photo-oxidation of silicone oil. The silicone oil was spin-coated onto the surface of optical elements, and then irradiated with a xenon excimer lamp in the air. In this treatment, a protective coating for plastic lenses, mirrors, and nonlinear optical crystals, which are highly deliquescent, was developed by taking advantage of the phenomenon in which organic silicone oil is transformed to inorganic amorphous glass by a process of photo-oxidation. This technique has enabled an optical thin coating film to transmit ultraviolet rays of wavelengths under 200 nm and possess the characteristics of homogeneity, high density, resistance to environment, anti-reflectiveness, resistance to water, and Mohs' scale of 5, which is comparable to apatite. This allows us to cool a slab laser head and use as a mirror for underwater laser welding.

  3. Diode laser power module for beamed power transmission

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Williams, M. D.; Lee, J. H.; Conway, E. J.

    1991-01-01

    Recent progress with powerful, efficient, and coherent monolithic diode master-oscillator/power-amplifier (M-MOPA) systems is promising for the development of a space-based diode laser power station. A conceptual design of a 50-kW diode laser power module was made for space-based power stations capable of beaming coherent power to the moon, Martian rovers, or other satellites. The laser diode power module consists of a solar photovoltaic array or nuclear power source, diode laser arrays (LDAs), a phase controller, beam-steering optics, a thermal management unit, and a radiator. Thermal load management and other relevant aspects of the system (such as power requirements and system mass) are considered. The 50-kW power module described includes the highest available efficiency of LD M-MOPA system to date. However, the overall efficiency of three amplifier stages, including the coupling efficiency, turns out to be 55.5 percent. Though a chain of PA stages generates a high-power coherent beam, there is a penalty due to the coupling loss between stages. The specific power of the 50-kW module using solar power is 6.58 W/kg.

  4. Deformable mirror for high power laser applications

    NASA Astrophysics Data System (ADS)

    Mrň; a, Libor; Sarbort, Martin; Hola, Miroslava

    2015-01-01

    The modern trend in high power laser applications such as welding, cutting and surface hardening lies in the use of solid-state lasers. The output beam of these lasers is characterized by a Gaussian intensity distribution. However, the laser beams with different intensity distributions, e.g. top-hat, are preferable in various applications. In this paper we present a new type of deformable mirror suitable for the corresponding laser beam shaping. The deformation of the mirror is achieved by an underlying array of actuators and a pressurized coolant that also provides the necessary cooling. We describe the results of the surface shape measurement using a 3D scanner for different settings of actuators. Further, we show the achieved intensity distributions measured by a beam profiler for a low power laser beam reflected from the mirror.

  5. Variable laser attenuator

    DOEpatents

    Foltyn, S.R.

    1987-05-29

    The disclosure relates to low loss, high power variable attenuators comprising one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength. 9 figs.

  6. Variable laser attenuator

    DOEpatents

    Foltyn, Stephen R.

    1988-01-01

    The disclosure relates to low loss, high power variable attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.

  7. Frequency stable high power lasers in space

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.

    1989-01-01

    The concept of a laser heterodyne gravity wave antenna that would operate in solar orbit with a one million kilometer path length is discussed. Laser technology that would be appropriate for operation of this space-based gravity wave detector is also discussed. The rapid progress in diode laser coupled with the energy storage and potentially sub-Hertz linewidths of solid state lasers, and the possibility of efficient frequency conversion by nonlinear optical techniques defines a technology that is appropriate for laser interferometry in space. The present status of diode-laser-pumped, solid state lasers is summarized and future progress is projected in areas of linewidth control, high average power, operating efficiency, and operational lifetimes that are essential for space-based applications.

  8. High power phase conjugated solid state lasers

    SciTech Connect

    Hackel, L.A.; Dane, C.B.; Zapata, L.E.; Hermann, M.R.

    1994-07-01

    Three laser systems that are being developed for use in x-ray generation which incorporate SBS phase conjugate mirrors are described. A 25J/pulse Nd:glass laser is being developed for commercial proximity print x-ray lithography; a 0.5J/pulse, 1.3 kHz pulse repetition frequency laser is being built for soft x-ray projection lithography; and a 1 kJ/pulse laser driver for a table top x-ray laser has been designed. The results of prototypical experimental investigations are presented and the basic design principles for high average power phase conjugated laser systems shared by each of these lasers are discussed.

  9. Early history of high-power lasers

    NASA Astrophysics Data System (ADS)

    Sutton, George W.

    2002-02-01

    This paper gives the history of the invention and development of early high power lasers, to which the author contributed and had personal knowledge. The earliest hint that a high power laser could be built came from the electric CO2-N2-He laser of Javan. It happened that the director of the Avco-Everett Research Laboratory had written his Ph.D. dissertation on the deactivation of the vibrational excitation of N2 in an expanding flow under Edward Teller, then at Columbia Univ. The director then started an in-house project to determine if gain could be achieved in a mixture similar to Javan's by means of a shock tunnel where a shock heated mixture of N2, CO2, and He gas was expanded through a supersonic nozzle into a cavity. This concept was named by the author as the gasdynamic laser (GDL). The paper traces the history of the initial gain measurements, the Mark II laser, the RASTA laser, the Tri-Service laser, its troubles and solutions, the United Technology's XLD gasdynamic laser, and their ALL laser. The history of the coastal Crusader will also be mentioned. Also discussed are the early experiments on a combustion-driven chemical laser, and its subsequent rejection by the director.

  10. Pulsed microhollow cathode discharge excimer sources

    NASA Astrophysics Data System (ADS)

    Moselhy, Mohamed; Shi, Wenhui; Strak, Robert H.; Schoenbach, Karl H.

    2001-10-01

    Microhollow cathode discharges (MHCDs) are non-equilibrium, high-pressure gas discharges between perforated electrodes separated by a dielectric layer. Typical dimensions for the electrode foil thickness and hole diameter are 100 μm. Direct current experiments in xenon, argon, neon, helium, argon fluoride, and xenon chloride [1,2] have been performed. The excimer efficiency varies between 1 % and 9 %. Pulsed operation allowed us to increase the current from 8 mA (dc) to approximately 80 mA (pulsed with a pulse width of 700 μs), limited by the onset of instabilities. The total excimer power was found to increase linearly with current, however, the radiant emittance and efficiency stayed constant. Reducing the pulse duration into the nanosecond range allowed us to increase the current into the ampere range. The maximum measured excimer power was 2.75 W per microdischarge. The maximum radiant emittance was 15 W/cm^2 and the efficiency reached values of 20 %. This effect is assumed to be due to non-equilibrium electron heating in the high-pressure plasma [3]. This work was supported by the National Science Foundation under grant # CTS0078618. 1. Karl H. Schoenbach, Ahmed El-Habachi, Mohamed M. Moselhy, Wenhui Shi, and Robert H. Stark, Physics of Plasmas 7, 2186 (2000). 2. P. Kurunczi, J. Lopez, H. Shah, and K. Becker, Int. J. Mass Spectrom. 205, 277 (2001). 3. Robert H. Stark and Karl H. Schoenbach, J. Appl. Phys. 89, 3568 (2001).

  11. Satellites Would Transmit Power By Laser Beams

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Walker, Gilbert H.; HUMES D. H.; Kwon, J. H.

    1995-01-01

    Arrays of diode lasers concentrate power into narrow beams. Baseline design of system formulated with regard to two particular missions that differ greatly in power requirements, thus showing scalability and attributes of basic system. Satellite system features large-scale array amplifier of high efficiency, injection-locked amplifiers, coherent combination of beams, and use of advanced lithographic technology to fabricate diode lasers in array. Extremely rapid development of applicable technologies make features realizable within decade.

  12. Optical power supply unit utilizing high power laser diode module developed for fiber laser pumping

    NASA Astrophysics Data System (ADS)

    Sakamoto, Akira; Kiyoyama, Wataru; Yamauchi, Ryozo

    2014-05-01

    High power laser diode developed for fiber laser pumping is evaluated as a light source for an optical power supply unit. The output power of the newly developed laser diode module exceeds 15 W with 105 μm core fiber. It is estimated that more than 1600 mW power supply can be achieved with the single emitter laser diode module and a polycrystalline silicon cell over 1 km away from the light source. This unit can be used for sensor nodes in the fiber sensor network.

  13. The Mercury Laser Advances Laser Technology for Power Generation

    SciTech Connect

    Ebbers, C A; Caird, J; Moses, E

    2009-01-21

    The National Ignition Facility (NIF) at Lawrence Livermore Laboratory is on target to demonstrate 'breakeven' - creating as much fusion-energy output as laser-energy input. NIF will compress a tiny sphere of hydrogen isotopes with 1.8 MJ of laser light in a 20-ns pulse, packing the isotopes so tightly that they fuse together, producing helium nuclei and releasing energy in the form of energetic particles. The achievement of breakeven will culminate an enormous effort by thousands of scientists and engineers, not only at Livermore but around the world, during the past several decades. But what about the day after NIF achieves breakeven? NIF is a world-class engineering research facility, but if laser fusion is ever to generate power for civilian consumption, the laser will have to deliver pulses nearly 100,000 times faster than NIF - a rate of perhaps 10 shots per second as opposed to NIF's several shots a day. The Mercury laser (named after the Roman messenger god) is intended to lead the way to a 10-shots-per-second, electrically-efficient, driver laser for commercial laser fusion. While the Mercury laser will generate only a small fraction of the peak power of NIF (1/30,000), Mercury operates at higher average power. The design of Mercury takes full advantage of the technology advances manifest in its behemoth cousin (Table 1). One significant difference is that, unlike the flashlamp-pumped NIF, Mercury is pumped by highly efficient laser diodes. Mercury is a prototype laser capable of scaling in aperture and energy to a NIF-like beamline, with greater electrical efficiency, while still running at a repetition rate 100,000 times greater.

  14. High power diode pumped alkali vapor lasers

    NASA Astrophysics Data System (ADS)

    Zweiback, J.; Krupke, B.

    2008-05-01

    Diode pumped alkali lasers have developed rapidly since their first demonstration. These lasers offer a path to convert highly efficient, but relatively low brightness, laser diodes into a single high power, high brightness beam. General Atomics has been engaged in the development of DPALs with scalable architectures. We have examined different species and pump characteristics. We show that high absorption can be achieved even when the pump source bandwidth is several times the absorption bandwidth. In addition, we present experimental results for both potassium and rubidium systems pumped with a 0.2 nm bandwidth alexandrite laser. These data show slope efficiencies of 67% and 72% respectively.

  15. 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.

  16. Laser beamed power: Satellite demonstration applications

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Westerlund, Larry H.

    1992-01-01

    It is possible to use a ground-based laser to beam light to the solar arrays of orbiting satellites, to a level sufficient to provide all or some of the operating power required. Near-term applications of this technology for providing supplemental power to existing satellites are discussed. Two missions with significant commercial pay-off are supplementing solar power for radiation-degraded arrays and providing satellite power during eclipse for satellites with failed batteries.

  17. Moderate-power cw fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Dianov, Evgenii M

    2004-10-31

    A review of the development and investigation of moderate-power (10{sup -1}-10{sup 2} W) cw fibre lasers is presented. The properties of optical fibres doped with rare-earth ions and methods for fabricating double-clad fibres are considered. The methods for fabrication of fibre Bragg gratings used as selective reflectors are discussed and the grating properties are analysed. The main pump schemes for double-clad fibre lasers are described. The properties of fibre lasers doped with neodymium, ytterbium, erbium, thulium, and holmium ions are also considered. The principles of fabrication of Raman converters of laser radiation based on optical fibres of different compositions are discussed and the main results of their studies are presented. It is concluded that fibre lasers described in the review can produce moderate-power radiation at any wavelength in the spectral range from 0.9 to 2 {mu}m. (review)

  18. Apparatus for advancing a wellbore using high power laser energy

    DOEpatents

    Zediker, Mark S.; Land, Mark S.; Rinzler, Charles C.; Faircloth, Brian O.; Koblick, Yeshaya; Moxley, Joel F.

    2014-09-02

    Delivering high power laser energy to form a borehole deep into the earth using laser energy. Down hole laser tools, laser systems and laser delivery techniques for advancement, workover and completion activities. A laser bottom hole assembly (LBHA) for the delivery of high power laser energy to the surfaces of a borehole, which assembly may have laser optics, a fluid path for debris removal and a mechanical means to remove earth.

  19. Pulsed Power for Solid-State Lasers

    SciTech Connect

    Gagnon, W; Albrecht, G; Trenholme, J; Newton, M

    2007-04-19

    Beginning in the early 1970s, a number of research and development efforts were undertaken at U.S. National Laboratories with a goal of developing high power lasers whose characteristics were suitable for investigating the feasibility of laser-driven fusion. A number of different laser systems were developed and tested at ever larger scale in pursuit of the optimum driver for laser fusion experiments. Each of these systems had associated with it a unique pulsed power option. A considerable amount of original and innovative engineering was carried out in support of these options. Ultimately, the Solid-state Laser approach was selected as the optimum driver for the application. Following this, the Laser Program at the Lawrence Livermore National Laboratory and the University of Rochester undertook aggressive efforts directed at developing the technology. In particular, at Lawrence Livermore National Laboratory, a series of laser systems beginning with the Cyclops laser and culminating in the present with the National Ignition Facility were developed and tested. As a result, a large amount of design information for solid-state laser pulsed power systems has been documented. Some of it is in the form of published papers, but most of it is buried in internal memoranda, engineering reports and LLNL annual reports. One of the goals of this book is to gather this information into a single useable format, such that it is easily accessed and understood by other engineers and physicists for use with future designs. It can also serve as a primer, which when seriously studied, makes the subsequent reading of original work and follow-up references considerably easier. While this book deals only with the solid-state laser pulsed power systems, in the bibliography we have included a representative cross section of papers and references from much of the very fine work carried out at other institutions in support of different laser approaches. Finally, in recent years, there has

  20. Preliminary results of tracked laser-assisted in-situ keratomileusis (T-LASIK) for myopia and hyperopia using the autonomous technologies excimer laser system

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Nesburn, Anthony B.; Salz, James J.

    2000-06-01

    A study was undertaken to assess the safety and efficacy of LASIK with the LADARVision laser by Autonomous Technologies, (Orlando, FL). The study included four subsets: Spherical myopia -- up to -11.00D, spherical hyperopia -- up to +6.00D. Both myopic and hyperopic astigmatism could be corrected, up to 6.00D of astigmatism. A total of 105 patients participated. Sixty-six patients were myopic and 39 were hyperopic. The mean (+/- SD) age was 42.8 +/- 9.3 years for myopia and 53.2 +/- 9.9 years for hyperopia. At 3 months postop. Sixty-one myopic eyes were available for evaluation. Uncorrected visual acuity was 20/20 in 70% of eyes and 20/40 in 92.9% of all eyes. The refractive outcome was within +/- 0.50D in 73.8% of eyes and within +/- 1.00D in 96.7 of eyes. Thirty-eight hyperopic eyes were available. Uncorrected visual acuity was 20/20 in 42.1% of eyes and 20/40 in 88% of all eyes. The refractive outcome was within +/- 0.50D in 57.9% of eyes and within +/- 1.00D in 86.8% of eyes. Complications were not sight threatening and were discussed in detail. Lasik with the LADARVision laser appears to be safe and effective.

  1. The future of high power laser techniques

    NASA Astrophysics Data System (ADS)

    Poprawe, Reinhart; Loosen, Peter; Hoffmann, Hans-Dieter

    2007-05-01

    High Power Lasers have been used for years in corresponding applications. Constantly new areas and new processes have been demonstrated, developed and transferred to fruitful use in industry. With the advent of diode pumped solid state lasers in the multi-kW-power regime at beam qualities not far away from the diffraction limit, a new area of applicability has opened. In welding applications speeds could be increased and systems could be developed with higher efficiently leading also to new perspectives for increased productivity, e.g. in combined processing. Quality control is increasingly demanded by the applying industries, however applications still are rare. Higher resolution of coaxial process control systems in time and space combined with new strategies in signal processing could give rise to new applications. The general approach described in this paper emphasizes the fact, that laser applications can be developed more efficiently, more precisely and with higher quality, if the laser radiation is tailored properly to the corresponding application. In applying laser sources, the parameter ranges applicable are by far wider and more flexible compared to heat, mechanical or even electrical energy. The time frame ranges from several fs to continuous wave and this spans approximately 15 orders of magnitude. Spacewise, the foci range from several µm to cm and the resulting intensities suitable for materials processing span eight orders of magnitude from 10 3 to 10 11 W/cm2. In addition to space (power, intensity) and time (pulse) the wavelength can be chosen as a further parameter of optimization. As a consequence, the resulting new applications are vast and can be utilized in almost every market segment of our global economy (Fig. 1). In the past and only partly today, however, this flexibility of laser technology is not exploited in full in materials processing, basically because in the high power regime the lasers with tailored beam properties are not

  2. High power gas laser - Applications and future developments

    NASA Technical Reports Server (NTRS)

    Hertzberg, A.

    1977-01-01

    Fast flow can be used to create the population inversion required for lasing action, or can be used to improve laser operation, for example by the removal of waste heat. It is pointed out that at the present time all lasers which are capable of continuous high-average power employ flow as an indispensable aspect of operation. High power laser systems are discussed, taking into account the gasdynamic laser, the HF supersonic diffusion laser, and electric discharge lasers. Aerodynamics and high power lasers are considered, giving attention to flow effects in high-power gas lasers, aerodynamic windows and beam manipulation, and the Venus machine. Applications of high-power laser technology reported are related to laser material working, the employment of the laser in controlled fusion machines, laser isotope separation and photochemistry, and laser power transmission.

  3. Systems analysis on laser beamed power

    NASA Technical Reports Server (NTRS)

    Zeiders, Glenn W., Jr.

    1993-01-01

    The NASA SELENE power beaming program is intended to supply cost-effective power to space assets via Earth-based lasers and active optics systems. Key elements of the program are analyzed, the overall effort is reviewed, and recommendations are presented.

  4. Nuclear-induced excimer fluorescence

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Shapiro, A.

    1980-01-01

    A theoretical calculation of a proposed atomic iodine laser system excited by a nuclear-powered photon source is considered. Overall system efficiency of 1.6% is calculated for the KrF fluorescent system and 2.3% for the Ar2F system. Laser power output of about 30 kW is estimated for a laser tube 1.8 cm in diameter and 60 cm long when used with a fast burst reactor. Such systems should easily scale to very high power.

  5. Magnetically switched power supply system for lasers

    NASA Technical Reports Server (NTRS)

    Pacala, Thomas J. (Inventor)

    1987-01-01

    A laser power supply system is described in which separate pulses are utilized to avalanche ionize the gas within the laser and then produce a sustained discharge to cause the gas to emit light energy. A pulsed voltage source is used to charge a storage device such as a distributed capacitance. A transmission line or other suitable electrical conductor connects the storage device to the laser. A saturable inductor switch is coupled in the transmission line for containing the energy within the storage device until the voltage level across the storage device reaches a predetermined level, which level is less than that required to avalanche ionize the gas. An avalanche ionization pulse generating circuit is coupled to the laser for generating a high voltage pulse of sufficient amplitude to avalanche ionize the laser gas. Once the laser gas is avalanche ionized, the energy within the storage device is discharged through the saturable inductor switch into the laser to provide the sustained discharge. The avalanche ionization generating circuit may include a separate voltage source which is connected across the laser or may be in the form of a voltage multiplier circuit connected between the storage device and the laser.

  6. High Power Picosecond Laser Pulse Recirculation

    SciTech Connect

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  7. High-power picosecond laser pulse recirculation.

    PubMed

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P J

    2010-07-01

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  8. High-power picosecond laser pulse recirculation.

    PubMed

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P J

    2010-07-01

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses. PMID:20596201

  9. Development of on-line laser power monitoring system

    NASA Astrophysics Data System (ADS)

    Ding, Chien-Fang; Lee, Meng-Shiou; Li, Kuan-Ming

    2016-03-01

    Since the laser was invented, laser has been applied in many fields such as material processing, communication, measurement, biomedical engineering, defense industries and etc. Laser power is an important parameter in laser material processing, i.e. laser cutting, and laser drilling. However, the laser power is easily affected by the environment temperature, we tend to monitor the laser power status, ensuring there is an effective material processing. Besides, the response time of current laser power meters is too long, they cannot measure laser power accurately in a short time. To be more precisely, we can know the status of laser power and help us to achieve an effective material processing at the same time. To monitor the laser power, this study utilize a CMOS (Complementary metal-oxide-semiconductor) camera to develop an on-line laser power monitoring system. The CMOS camera captures images of incident laser beam after it is split and attenuated by beam splitter and neutral density filter. By comparing the average brightness of the beam spots and measurement results from laser power meter, laser power can be estimated. Under continuous measuring mode, the average measuring error is about 3%, and the response time is at least 3.6 second shorter than thermopile power meters; under trigger measuring mode which enables the CMOS camera to synchronize with intermittent laser output, the average measuring error is less than 3%, and the shortest response time is 20 millisecond.

  10. Transient absorption probe of intermolecular triplet excimer of naphthalene in fluid solutions: Identification of the species based on comparison to the intramolecular triplet excimers of covalently-linked dimers

    SciTech Connect

    Wang, X.; Kofron, W.G.; Kong, S.; Rajesh, C.S.; Modarelli, D.A.; Lim, E.C.

    2000-02-24

    The authors report here the observation of the laser-induced transient absorption spectrum of intermolecular triplet excimers of naphthalene in fluid solution. This assignment is confirmed by comparison to the transient absorption spectra of the intramolecular triplet excimers of covalently linked dimers of naphthalene and quinoxaline.

  11. Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

    NASA Technical Reports Server (NTRS)

    Harris, S. E.; Siegman, A. E.; Kuizenga, D. J.; Kung, A. H.; Young, J. F.; Bekkers, G. W.; Bloom, D. M.; Newton, J. H.; Phillion, D. W.

    1975-01-01

    The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources.

  12. Crystal fibers for high power lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Florea, C.; Gibson, D.; Peele, J.; Askins, C.; Shaw, B.; Bowman, S.; O'Connor, S.; Bayya, S.; Aggarwal, I.; Sanghera, J. S.

    2013-02-01

    In this paper, we present our recent progress in developing single crystal fibers for high power single frequency fiber lasers. The optical, spectral and morphological properties as well as the loss and gain measured from these crystal fibers drawn by Laser Heated Pedestal Growth (LHPG) system are also discussed. Results on application of various cladding materials on the crystal core and the methods of fiber end-face polishing are also presented.

  13. Xenon excimer emission from pulsed microhollow cathode discharges

    NASA Astrophysics Data System (ADS)

    Moselhy, M.; Shi, W.; Stark, R. H.; Schoenbach, K. H.

    2001-08-01

    By applying electrical pulses of 20 ns duration to xenon microplasmas, generated by direct current microhollow cathode discharges, we were able to increase the xenon excimer emission by more than an order of magnitude over direct current discharge excimer emission. For pulsed voltages in excess of 500 V, the optical power at 172 nm was found to increase exponentially with voltage. Largest values obtained were 2.75 W of vacuum-ultraviolet optical power emitted from a single microhollow cathode discharge in 400 Torr xenon with a 750 V pulse applied to a discharge. Highest radiative emittance was 15.2 W/cm2. The efficiency for excimer emission was found to increase linearly with pulsed voltages above 500 V reaching values of 20% at 750 V.

  14. Interaction of wide band gap single crystals with 248 nm excimer laser radiation. XII. The emission of negative atomic ions from alkali halides

    SciTech Connect

    Kimura, Kenichi; Langford, S. C.; Dickinson, J. T.

    2007-12-01

    Many wide band gap materials yield charged and neutral emissions when exposed to sub-band-gap laser radiation at power densities below the threshold for optical breakdown and plume formation. In this work, we report the observation of negative alkali ions from several alkali halides under comparable conditions. We observe no evidence for negative halogen ions, in spite of the high electron affinities of the halogens. Significantly, the positive and negative alkali ions show a high degree of spatial and temporal overlap. A detailed study of all the relevant particle emissions from potassium chloride (KCl) suggests that K{sup -} is formed by the sequential attachment of two electrons to K{sup +}.

  15. Comparison of electrically driven lasers for space power transmission

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.; Lee, J. H.; Williams, M. D.; Schuster, G.; Conway, E. J.

    1988-01-01

    High-power lasers in space could provide power for a variety of future missions such as spacecraft electric power requirements and laser propulsion. This study investigates four electrically pumped laser systems, all scaled to 1-MW laser output, that could provide power to spacecraft. The four laser systems are krypton fluoride, copper vapor, laser diode array, and carbon dioxide. Each system was powered by a large solar photovoltaic array which, in turn, provided power for the appropriate laser power conditioning subsystem. Each system was block-diagrammed, and the power and efficiency were found for each subsystem block component. The copper vapor system had the lowest system efficiency (6 percent). The CO2 laser was found to be the most readily scalable but has the disadvantage of long laser wavelength.

  16. Autokeratomileusis Laser

    NASA Astrophysics Data System (ADS)

    Kern, Seymour P.

    1987-03-01

    Refractive defects such as myopia, hyperopia, and astigmatism may be corrected by laser milling of the cornea. An apparatus combining automatic refraction/keratometry and an excimer type laser for precision reshaping of corneal surfaces has been developed for testing. When electronically linked to a refractometer or keratometer or holographic imaging device, the laser is capable of rapidly milling or ablating corneal surfaces to preselected dioptric power shapes without the surgical errors characteristic of radial keratotomy, cryokeratomileusis or epikeratophakia. The excimer laser simultaneously generates a synthetic Bowman's like layer or corneal condensate which appears to support re-epithelialization of the corneal surface. An electronic feedback arrangement between the measuring instrument and the laser enables real time control of the ablative milling process for precise refractive changes in the low to very high dioptric ranges. One of numerous options is the use of a rotating aperture wheel with reflective portions providing rapid alternate ablation/measurement interfaced to both laser and measurement instrumentation. The need for the eye to be fixated is eliminated or minimized. In addition to reshaping corneal surfaces, the laser milling apparatus may also be used in the process of milling both synthetic and natural corneal inlays for lamellar transplants.

  17. High power, electrically tunable quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Slivken, Steven; Razeghi, Manijeh

    2016-02-01

    Mid-infrared laser sources (3-14 μm wavelengths) which have wide spectral coverage and high output power are attractive for many applications. This spectral range contains unique absorption fingerprints of most molecules, including toxins, explosives, and nerve agents. Infrared spectroscopy can also be used to detect important biomarkers, which can be used for medical diagnostics by means of breath analysis. The challenge is to produce a broadband midinfrared source which is small, lightweight, robust, and inexpensive. We are currently investigating monolithic solutions using quantum cascade lasers. A wide gain bandwidth is not sufficient to make an ideal spectroscopy source. Single mode output with rapid tuning is desirable. For dynamic wavelength selection, our group is developing multi-section laser geometries with wide electrical tuning (hundreds of cm-1). These devices are roughly the same size as a traditional quantum cascade lasers, but tuning is accomplished without any external optical components. When combined with suitable amplifiers, these lasers are capable of multi-Watt single mode output powers. This manuscript will describe our current research efforts and the potential for high performance, broadband electrical tuning with the quantum cascade laser.

  18. Power plant material characterization by lasers

    SciTech Connect

    Not Available

    1993-02-01

    The EPRI Nuclear Division undertook examination of the feasibility of utilizing lasers to perform in situ operations within power plants in 1983. The Nd- Yag laser was of particular interest because flexible fiber optics cabling could be utilized for beam transport; the end effectors could be made small enough to access power plant components remotely. Beam management for welding and metal conditioning in confined spaces; the first issue examined, lead to the application for steam generator repairs that is now in common usage. This report examines the laser beam as a source of information about the material property condition; an application made feasible by advances in fiber and laser technology that were achieved beginning in 1989. This work, examines the prospects for determination of material condition properties within power plants because the laser beam can be utilized for sampling and as a source of optical, thermal, ultrasonic, spectrographic and mensuration data that may be obtained nondestructively. Both application evaluations and feasibility testing is described.

  19. Transmission Of Power Via Combined Laser Beams

    NASA Technical Reports Server (NTRS)

    Kwon, Jin H.; Lee, Ja H.

    1992-01-01

    Laser Diode Array (LDA) appears to be most efficient means of transferring power from Earth to satellites and between satellites, in terms of mass and size, of various laser configurations. To form large-scale-array amplifier (LSAA), element LDA's must generate well-defined diffraction-limited beams. Coherent matching of phases among LDA's enables system to generate good beam pattern in far field over thousands of kilometers. By passing beam from master laser through number of LDA amplifiers simultaneously, one realizes coherence among amplified output beams. LSAA used for transmission of power with efficiency of approximately 80 percent into receiver of moderate size at 5,000 km. Also transmits data at high rates by line-of-sight rather than fiber optics.

  20. Trends in high-power ultrafast lasers

    NASA Astrophysics Data System (ADS)

    Saraceno, Clara; Emaury, Florian; Diebold, Andreas; Graumann, Ivan; Golling, Matthias; Keller, Ursula

    2016-05-01

    Ultrafast laser sources are one of the main achievements of the past decades. Finding new avenues to obtain higher average powers and pulse energies from these sources is currently a topic of important research efforts both for scientific and industrial applications. SESAM modelocked thin-disk lasers are one of the most promising laser technology to reach this goal from table-top systems: recently, average powers of 275 W and pulse energies of 80 μJ were demonstrated directly from a modelocked oscillators without additional external amplification. In this presentation, we will review the current state-of-the art of such table-top systems and present guidelines for future kilowatt-class systems.

  1. Applications of lasers and electro-optics

    NASA Astrophysics Data System (ADS)

    Tan, B. C.; Low, K. S.; Chen, Y. H.; Ahmad, Harith; Tou, T. Y.

    Supported by the IRPA Programme on Laser Technology and Applications, many types of lasers have been designed, constructed and applied in various areas of science, medicine and industries. Amongst these lasers constructed were high power carbon dioxide lasers, rare gas halide excimer lasers, solid state Neodymium-YAG lasers, nitrogen lasers, flashlamp pumped dye lasers and nitrogen and excimer laser pumped dye lasers. These lasers and the associated electro-optics system, some with computer controlled, are designed and developed for the following areas of applications: (1) industrial applications of high power carbon dioxide lasers for making of i.c. components and other materials processing purposes -- prototype operational systems have been developed; (2) Medical applications of lasers for cancer treatment using the technique of photodynamic therapy -- a new and more effective treatment protocol has been proposed; (3) agricultural applications of lasers in palm oil and palm fruit-fluorescence diagnostic studies -- fruit ripeness signature has been developed and palm oil oxidation level were investigated; (4) development of atmospheric pollution monitoring systems using laser lidar techniques -- laboratory scale systems were developed; and (5) other applications of lasers including laser holographic and interferometric methods for the non destructive testing of materials.

  2. Application of Laser Ablation Processing in Electric Power System Industries

    NASA Astrophysics Data System (ADS)

    Konagai, Chikara; Sano, Yuji; Nittoh, Koichi; Kuwako, Akira

    The present status of laser ablation processing applied in electric power system industries is reviewed. High average power LD-pumped Nd:YAG lasers with Q-switch have been developed and currently introduced into various applications. Optical fiber based laser beam delivery systems for Q-switched pulse laser are also being developed these years. Based on such laser and beam delivery technology, laser ablation processes are gradually introduced in maintenance of nuclear power plant, thermal power plant and electrical power distribution system. Cost effectiveness, robustness and reliability of the process is highly required for wide utilization in these fields.

  3. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    SciTech Connect

    Komashko, A

    2003-01-06

    Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for a variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of

  4. High-average-power exciplex laser system

    NASA Astrophysics Data System (ADS)

    Sentis, M.

    The LUX high-average-power high-PRF exciplex laser (EL) system being developed at the Institut de Mecanique des Fluides de Marseille is characterized, and some preliminary results are presented. The fundamental principles and design criteria of ELs are reviewed, and the LUX components are described and illustrated, including a closed-circuit subsonic wind tunnel and a 100-kW-average power 1-kHz-PRF power pulser providing avalanche-discharge preionization by either an electron beam or an X-ray beam. Laser energy of 50 mJ has been obtained at wavelength 308 nm in the electron-beam mode (14.5 kV) using a 5300/190/10 mixture of Ne/Xe/HCl at pressure 1 bar.

  5. High power regenerative laser amplifier

    DOEpatents

    Miller, John L.; Hackel, Lloyd A.; Dane, Clifford B.; Zapata, Luis E.

    1994-01-01

    A regenerative amplifier design capable of operating at high energy per pulse, for instance, from 20-100 Joules, at moderate repetition rates, for instance from 5-20 Hertz is provided. The laser amplifier comprises a gain medium and source of pump energy coupled with the gain medium; a Pockels cell, which rotates an incident beam in response to application of a control signal; an optical relay system defining a first relay plane near the gain medium and a second relay plane near the rotator; and a plurality of reflectors configured to define an optical path through the gain medium, optical relay and Pockels cell, such that each transit of the optical path includes at least one pass through the gain medium and only one pass through the Pockels cell. An input coupler, and an output coupler are provided, implemented by a single polarizer. A control circuit coupled to the Pockels cell generates the control signal in timed relationship with the input pulse so that the input pulse is captured by the input coupler and proceeds through at least one transit of the optical path, and then the control signal is applied to cause rotation of the pulse to a polarization reflected by the polarizer, after which the captured pulse passes through the gain medium at least once more and is reflected out of the optical path by the polarizer before passing through the rotator again to provide an amplified pulse.

  6. High power regenerative laser amplifier

    DOEpatents

    Miller, J.L.; Hackel, L.A.; Dane, C.B.; Zapata, L.E.

    1994-02-08

    A regenerative amplifier design capable of operating at high energy per pulse, for instance, from 20-100 Joules, at moderate repetition rates, for instance from 5-20 Hertz is provided. The laser amplifier comprises a gain medium and source of pump energy coupled with the gain medium; a Pockels cell, which rotates an incident beam in response to application of a control signal; an optical relay system defining a first relay plane near the gain medium and a second relay plane near the rotator; and a plurality of reflectors configured to define an optical path through the gain medium, optical relay and Pockels cell, such that each transit of the optical path includes at least one pass through the gain medium and only one pass through the Pockels cell. An input coupler, and an output coupler are provided, implemented by a single polarizer. A control circuit coupled to the Pockels cell generates the control signal in timed relationship with the input pulse so that the input pulse is captured by the input coupler and proceeds through at least one transit of the optical path, and then the control signal is applied to cause rotation of the pulse to a polarization reflected by the polarizer, after which the captured pulse passes through the gain medium at least once more and is reflected out of the optical path by the polarizer before passing through the rotator again to provide an amplified pulse. 7 figures.

  7. Tapered fiber based high power random laser.

    PubMed

    Zhang, Hanwei; Du, Xueyuan; Zhou, Pu; Wang, Xiaolin; Xu, Xiaojun

    2016-04-18

    We propose a novel high power random fiber laser (RFL) based on tapered fiber. It can overcome the power scaling limitation of RFL while maintaining good beam quality to a certain extent. An output power of 26.5 W has been achieved in a half-open cavity with one kilometer long tapered fiber whose core diameter gradually changes from 8 μm to 20 μm. The steady-state light propagation equations have been modified by taking into account the effective core area to demonstrate the tapered RFL through numerical calculations. The numerical model effectively describes the power characteristics of the tapered fiber based RFL, and both the calculating and experimental results show higher power exporting potential compared with the conventional single mode RFL. PMID:27137338

  8. Methods for determining optical power, for power-normalizing laser measurements, and for stabilizing power of lasers via compliance voltage sensing

    DOEpatents

    Taubman, Matthew S; Phillips, Mark C

    2015-04-07

    A method is disclosed for power normalization of spectroscopic signatures obtained from laser based chemical sensors that employs the compliance voltage across a quantum cascade laser device within an external cavity laser. The method obviates the need for a dedicated optical detector used specifically for power normalization purposes. A method is also disclosed that employs the compliance voltage developed across the laser device within an external cavity semiconductor laser to power-stabilize the laser mode of the semiconductor laser by adjusting drive current to the laser such that the output optical power from the external cavity semiconductor laser remains constant.

  9. High power laser and cathode structure thereof

    SciTech Connect

    Nam, K. H.; Seguin, H. J.; Tulip, J.

    1981-09-08

    A cathode structure for gas lasers is disclosed that is comprised of a flat plate of non-conducting material positioned in the laser in spaced relation to the laser anode to define a discharge region therebetween, a two-dimensional array of metal sub-electrode rods passing through the plate and having their upper ends lying flush with the surface of the plate, a block of dielectric material positioned below the plate and containing a series of transverse channels therein, electric current conductors lying in the channels and adapted for connection to a power supply, the lower ends of the said rods passing through openings in the block into the channels to define a predetermined uniform gap between the ends of the rods and the electrical conductor, and a liquid electrolyte solution filling the channels and electrically connecting the sub-electrode rods and the conductors.

  10. Design investigation of solar powered lasers for space applications

    NASA Technical Reports Server (NTRS)

    Taussig, R.; Bruzzone, C.; Quimby, D.; Nelson, L.; Christiansen, W.; Neice, S.; Cassady, P.; Pindroh, A.

    1979-01-01

    The feasibility of solar powered lasers for continuous operation in space power transmission was investigated. Laser power transmission in space over distances of 10 to 100 thousand kilometers appears possible. A variety of lasers was considered, including solar-powered GDLs and EDLs, and solar-pumped lasers. An indirect solar-pumped laser was investigated which uses a solar-heated black body cavity to pump the lasant. Efficiencies in the range of 10 to 20 percent are projected for these indirect optically pumped lasers.

  11. Flow lasers. [fluid mechanics of high power continuous output operations

    NASA Technical Reports Server (NTRS)

    Christiansen, W. H.; Russell, D. A.; Hertzberg, A.

    1975-01-01

    The present work reviews the fluid-mechanical aspects of high-power continuous-wave (CW) lasers. The flow characteristics of these devices appear as classical fluid-mechanical phenomena recast in a complicated interactive environment. The fundamentals of high-power lasers are reviewed, followed by a discussion of the N2-CO2 gas dynamic laser. Next, the HF/DF supersonic diffusion laser is described, and finally the CO electrical-discharge laser is discussed.

  12. Development Of High Power Solid State Lasers At HOYA Corp.

    NASA Astrophysics Data System (ADS)

    Mochizuki, Takayasu; Unternahrer, Josef R.; Amano, Satoru; Tajima, Hidemi; Nakajima, Sadahiro; Moriyama, M.

    1989-03-01

    Several lasers are, or have been, developed at the HOYA Laser Laboratory: Conventional YAG-rod lasers, glass fiber bundle lasers and moving glass slab lasers. Slab lasers are considered the engineering answer to the demand of higher average power. We obtained 386 W with a moving glass slab laser. Parts of the program are also erbium doped YAG and glass lasers. We developed a stable and reliable 10-W output 3-μm Er:YAG laser. All models have been developed with a specific application in mind,

  13. Adaptive optics for laser power beaming

    NASA Technical Reports Server (NTRS)

    Leland, Robert P.

    1992-01-01

    It has been proposed to use a high energy pulsed laser to beam power into space for satellites or a lunar base. The effects of atmospheric transmission are critical to such a system. Thermal blooming in the atmosphere can cause the beam to spread rapidly. Atmospheric turbulence can cause beam bending or beam spreading, resulting in the loss of transmitted energy that fails to hit the target receiver.

  14. High-power semiconductor separate-confinement double heterostructure lasers

    SciTech Connect

    Tarasov, I S

    2010-10-15

    The review is devoted to high-power semiconductor lasers. Historical reference is presented, physical and technological foundations are considered, and the concept of high-power semiconductor lasers is formulated. Fundamental and technological reasons limiting the optical power of a semiconductor laser are determined. The results of investigations of cw and pulsed high-power semiconductor lasers are presented. Main attention is paid to inspection of the results of experimental studies of single high-power semiconductor lasers. The review is mainly based on the data obtained in the laboratory of semiconductor luminescence and injection emitters at the A.F. Ioffe Physicotechnical Institute. (review)

  15. Satellite Power Systems (SPS) laser studies. Volume 1: Laser environmental impact study

    NASA Technical Reports Server (NTRS)

    Beverly, R. E., III

    1980-01-01

    The environmental impact of space to Earth power transmission using space borne laser subsystems is emphasized. A laser system is defined, estimates of relevant efficiencies for laser power generation and atmospheric transmission are developed, and a comparison is made to a microwave system. Ancillary issues, such as laser beam spreading, safety and security, mass and volume estimates and technology growth are considered.

  16. High-power laser diodes, laser diode modules, and their applications

    NASA Astrophysics Data System (ADS)

    Daiminger, Franz X.; Dorsch, Friedhelm; Lorenzen, Dirk

    1998-12-01

    High power laser diodes and especially high power laser diode modules made enormous progress in the last few years. Different aspects of high power laser diodes are treated starting from general description of high power laser diodes and their mounting techniques, characterizing the electro- optical behavior of single laser bars and finally presenting beamshaping optics for the collimation of large modules. The later technique allows for symmetrical focal spots in the kilowatt range with a beam quality of about 170 mm*mrad. Different aspects of current applications of high power laser diodes are presented.

  17. The lasers for TMLR application

    NASA Astrophysics Data System (ADS)

    Panchenko, Vladislav Y.; Berishvili, I. I.; Vasiltsov, Victor V.; Ulyanov, Valerii A.; Egorov, E. N.; Solovjev, Andrey V.; Semenov, A. N.; Tarasov, M. N.; Roshin, M. A.

    2004-06-01

    The paper presents the analysis of the requirements to the laser systems used to cure the ischemic disease of the heart by the method of transmyocardial laser revascularization (TMLR). Among the medical laser systems under discussion (solid-state Nd:YAG, Er:YAG, Ho:YAG, excimer lasers, etc.) the high-power CO2 laser with pulse energy to 40 J is most suited to produce channels in the heart muscle. The paper provides the description and the technical characteristics of medical laser systems of "Perfocor" series, based on high-power waveguide CO2 lasers with pulse energy to 60 J, developed at ILIT RAS. The methods to determine the time of laser radiation penetration through the myocardium/blood boundary have been briefly discussed. The application of the "Perfocor" system in other laser operations on blood-filled organs has also been discussed.

  18. Solar pumped laser technology options for space power transmission

    NASA Technical Reports Server (NTRS)

    Conway, E. J.

    1986-01-01

    An overview of long-range options for in-space laser power transmission is presented. The focus is on the new technology and research status of solar-pumped lasers and their solar concentration needs. The laser options include gas photodissociation lasers, optically-pumped solid-state lasers, and blackbody-pumped transfer lasers. The paper concludes with a summary of current research thrusts.

  19. Enabling lunar and space missions by laser power transmission

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.; Nealy, J. E.; Humes, D. H.; Meador, W. E.

    1992-01-01

    Applications are proposed for laser power transmission on the Moon. A solar-pumped laser in lunar orbit would beam power to the lunar surface for conversion into either electricity or propulsion needs. For example, lunar rovers could be much more flexible and lighter than rovers using other primary power sources. Also, laser power could be absorbed by lunar soil to create a hard glassy surface for dust-free roadways and launch pads. Laser power could also be used to power small lunar rockets or orbital transfer vehicles, and finally, photovoltaic laser converters could power remote excavation vehicles and human habitats. Laser power transmission is shown to be a highly flexible, enabling primary power source for lunar missions.

  20. Method and apparatus for tuning high power lasers

    DOEpatents

    Hutchinson, Donald P.; Vandersluis, Kenneth L.

    1977-04-19

    This invention relates to high power gas lasers that are adapted to be tuned to a desired lasing wavelength through the use of a gas cell to lower the gain at a natural lasing wavelength and "seeding" the laser with a beam from a low power laser which is lasing at the desired wavelength. This tuning is accomplished with no loss of power and produces a pulse with an altered pulse shape. It is potentially applicable to all gas lasers.

  1. A lunar rover powered by an orbiting laser diode array

    NASA Technical Reports Server (NTRS)

    De Young, R. J.; Williams, M. D.; Walker, G. H.; Schuster, G. L.; Lee, J. H.

    1991-01-01

    A conceptual design of a high-power, long-duration lunar rover powered by a laser beam is proposed. The laser transmitter in lunar orbit consists of an SP-100 nuclear reactor prime power source providing 100 kW of electricity to a laser array that emits 50 kW of laser radiation. The laser radiation is beamed to the lunar surface where it is received by a GaAlAs solid-state, laser-to-electric converter. This converter provides 22 kW of electrical power to the rover vehicle for science, locomotion, and crew needs. The mass of the laser transmitter is approximately 5000 kg, whereas the mass of the rover power supply is 520 kg. The rover power unit is significantly less massive than alternative rover power units.

  2. Hybrid high power femtosecond laser system

    NASA Astrophysics Data System (ADS)

    Trunov, V. I.; Petrov, V. V.; Pestryakov, E. V.; Kirpichnikov, A. V.

    2006-01-01

    Design of a high-power femtosecond laser system based on hybrid chirped pulse amplification (CPA) technique developed by us is presented. The goal of the hybrid principle is the use of the parametric and laser amplification methods in chirped pulse amplifiers. It makes it possible to amplify the low-cycle pulses with a duration of <= fs to terawatt power with a high contrast and high conversion efficiency of the pump radiation. In a created system the Ti:Sapphire laser with 10 fs pulses at 810 nm and output energy about 1-3 nJ will be used like seed source. The oscillator pulses were stretched to duration of about 500 ps by an all-reflective grating stretcher. Then the stretched pulses are injected into a nondegenerate noncollinear optical parametric amplifier (NOPA) on the two BBO crystals. After amplification in NOPA the residual pump was used in a bow-tie four pass amplifier with hybrid active medium (based on Al II0 3:Ti 3+ and BeAl IIO 4:Ti 3+ crystals). The final stage of the amplification system consists of two channels, namely NIR (820 nm) and short-VIS (410 nm). Numerical simulation has shown that the terawatt level of output power can be achieved also in a short-VIS channel at the pumping of the double-crystal BBO NOPA by the radiation of the fourth harmonic of the Nd:YAG laser at 266 nm. Experimentally parametric amplification in BBO crystals of 30-50 fs pulses were investigated and optimized using SPIDER technique and single-shot autocomelator for the realization of shortest duration 40 fs.

  3. High power CO lasers and their application potential

    NASA Astrophysics Data System (ADS)

    Maisenhaelder, F.

    1989-06-01

    Industrial applications of high-power CO lasers are examined. The characteristics specific to CO lasers are briefly reviewed, and applications where the CO laser seems to promise wavelength-related advantages over other lasers are examined. Experimentally demonstrated applications in the drilling and cutting of metals, isotope separation and photochemistry, and laser medicine are addressed, Developments in the high power range in Japan, Soviet Union, and Germany are described, and a comparison is made between high power CO and CO2 gas lasers for civil applications.

  4. High-power, high-intensity laser propagation and interactions

    SciTech Connect

    Sprangle, Phillip; Hafizi, Bahman

    2014-05-15

    This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.

  5. Applying laser technology to decommissioning for nuclear power plant

    NASA Astrophysics Data System (ADS)

    Saishu, Sadanori; Abe, Seiji; Inoue, T.

    2000-01-01

    Laser technology has much possibility to accomplish nuclear facility decommissioning effective and the laser application to cutting technique and decontamination technique is considered in Japan. Nuclear Power Engineering Corporation had developed CO laser for cutting technique, and had developed YAG laser for decontamination.

  6. High-power copper vapour lasers and applications

    SciTech Connect

    Chang, J.J.; Warner, B.E.; Boley, C.D.; Dragon, E.P.

    1995-08-01

    Expanded applications of copper vapor lasers has prompted increased demand for higher power and better beam quality. This paper reports recent progress in laser power scaling, MOPA operation, beam quality improvement, and applications in precision laser machining. Issues such as gas heating, radial delay, discharge instability, and window heating will also be discussed.

  7. Modulation instability in high power laser amplifiers.

    PubMed

    Rubenchik, Alexander M; Turitsyn, Sergey K; Fedoruk, Michail P

    2010-01-18

    The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified.

  8. Real-time power measurement and control for high power diode laser

    NASA Astrophysics Data System (ADS)

    Qin, Wen-bin; Liu, You-qiang; Cao, Yin-hua; Wang, Zhi-yong

    2011-06-01

    As the continual improvement of technology and beam quality, diode laser, with poor beam quality, no longer just apply to pump solid-state laser. As a kind of implement of laser materials processing, high-power diode laser has been used in manufacture, as a brand new means of laser processing. Due to the influence of inevitable unstable factors, for example, the temperature of water-cooler, the current of power supply, etc, the output power of diode laser will be unstable. And laser output power, as an important parameter, frequently affects the performance of the laser beam and the experimental results of processing, especially in the laser materials processing. Therefore, researching the real-time power measurement and control of high power diode laser has great significance, and for diode laser, it would improve performance of itself. To achieve the purpose of real-time detection, traditional measuring method, placing a power sensor behind the total-reflection mirror of laser resonant cavity, is mainly applied in the system of gas laser and solid-state laser. However, Owing to the high integration level of diode laser, traditional measuring method can't be adopted. A technique for real-time measure output power of high power diode laser is developed to improve quality of the laser in this paper. A lens placed at an angle of 45° in the system was used to sample output light of laser, and a piece of ground glass was used to uniform the beam power density, then the photoelectric detector received an optic signal and converted it into electric signal. This feeble signal was processed by amplification circuit with a filter. Finally, this detected electric signal was applied to accomplish the closed-loop control of power. The performance of power measurement and control system was tested with the 300W diode laser, and the measuring inaccuracy achieved was less than +/-1%.

  9. Excimer emission from high pressure microhollow cathode discharges in xenon

    SciTech Connect

    El-Habachi, A.; Schoenbach, K.H.

    1998-12-31

    By reducing the diameter of the cathode opening in hollow cathode discharge geometry to values on the order of 100 micrometers the authors were able to operate the discharged in argon and xenon in a direct current mode at atmospheric pressure. The micro-discharges have been shown to emit excimer radiation peaking at wavelengths of 130 nm and 170 nm, respectively. They have in this study particularly concentrated on the xenon VUV radiation. The emission from a 100 micrometers microhollow cathode discharge in xenon at pressures between 40 and 760 Torr was measured over the spectral range from 130 nm to 400 nm. At 40 Torr, the 147 nm Xenon resonance line dominates the emission spectra. There are some indications of the first continuum which extends from the resonance line towards longer wavelength. The second excimer continuum peaking at 170 nm appears at higher pressures. At pressures greater than 300 Torr, it dominates the emission spectra up to the longest recorded wavelength of 400 nm. In order to determine the absolute values of the excimer radiation the emission was compared to that of calibrated UV sources: a Hg lamp and a Deuterium lamp. The results gave them a value of the efficiency defined as the ratio of the optical power of the excimer emitter to the input electrical power, of 5.3% and 6.3%, respectively. A single discharge, which was in this experiment run with a current of 3 mA at a forward voltage of 200 to 250 V, emits therefore {approximately}40 mW of VUV radiation concentrated in the spectral range from 150 to 190 nm. The possibility to operate the discharges in parallel opens the possibility to fabricate scalable flat panel excimer lamps.

  10. Performance and lifetime of high-power diode lasers and diode laser systems

    NASA Astrophysics Data System (ADS)

    Dorsch, Friedhelm; Daiminger, Franz X.

    1999-04-01

    High-power diode lasers have reached output power and reliability to meet requirements for industrial applications. Stacking of laser elements to modules increases the output power, beam shaping techniques allow to focus the radiation of a module to a single spot. An integrated diode laser systems with totally 50 laser bars is shown, that includes cooling, power supply and control unit. The laser radiation is transmitted by an optical fiber and an objective focuses the radiation onto the workpiece with a round spot of less than 1 mm diameter and cw power of more than 1 kW.

  11. Proposed high-power UV industrial demonstration laser at CEBAF

    NASA Astrophysics Data System (ADS)

    Benson, Stephen V.; Bisognano, Joseph J.; Bohn, Courtlandt L.; Cardman, Larry; Colson, William B.; Davidson, Paul C.; Douglas, David; Dylla, H. Frederick; Engwall, David; Fugitt, Jock; Goldstein, John C.; Jordan, Kevin; Kehne, David; Li, Zhenghai; Liu, Hong-Xiu; Merminga, Lia; Neil, George R.; Neuffer, David; Shinn, Michelle D.; Wiseman, Mark; Wong, Robert K.

    1996-04-01

    The Laser Processing Consortium, a collaboration of industries, universities, and the Continuous Electron Accelerator Facility in Newport News, Virginia, has proposed building a demonstration industrial processing laser for surface treatment and micro-machining The laser is a free-electron laser with average power output exceeding 1 kW in the ultraviolet. The design calls for a novel driver accelerator that recovers most of the energy of the exhaust electron beam to produce laser light with good wall-lug efficiency. The laser and accelerator design use technologies that are scalable to much higher power. We will describe the critical design issues in the laser such as the stability, power handling, and losses of the optical resonator, and the quality, power, and reliability of the electron beam. We will also describe the calculated laser performance. Finally progress to date on accelerator development and resonator modeling will be reported.

  12. Near-term feasibility demonstration of laser power beaming

    SciTech Connect

    Friedman, H.W.

    1994-01-01

    A mission to recharge batteries of satellites in geostationary orbits (geosats) may be a commercially viable application which could be achieved with laser systems somewhat larger than present state-of-the-art. The lifetime of batteries on geosats is limited by repetitive discharge cycles which occur when the satellites are eclipsed by the earth during the spring and fall equinoxes. By coupling high power lasers with modern, large aperture telescopes and laser guide star adaptive optics systems, present day communications satellites could be targeted. It is important that a near term demonstration of laser power beaming be accomplished using lasers in the kilowatt range so that issues associated with high average power be addressed. The Laser Guide Star Facility at LLNL has all the necessary subsystems needed for such a near term demonstration, including high power lasers for both the power beam and guide star, beam directors and satellite tracking system.

  13. High power laser workover and completion tools and systems

    SciTech Connect

    Zediker, Mark S; Rinzler, Charles C; Faircloth, Brian O; Koblick, Yeshaya; Moxley, Joel F

    2014-10-28

    Workover and completion systems, devices and methods for utilizing 10 kW or more laser energy transmitted deep into the earth with the suppression of associated nonlinear phenomena. Systems and devices for the laser workover and completion of a borehole in the earth. These systems and devices can deliver high power laser energy down a deep borehole, while maintaining the high power to perform laser workover and completion operations in such boreholes deep within the earth.

  14. In-situ laser power/energy monitoring in biomedical applications

    NASA Astrophysics Data System (ADS)

    Giroux, Michel; Marchand, Loic; Carmichael, Luc; Vander Haeghe, Ronald E.

    1998-09-01

    The medical laser market is with no doubt one of the most active with a very fast growth. The increase was led by a surge in both ophthalmic excimer systems and CO2 lasers for dermatology treatment and skin resurfacing. Specialty niches in dermatology (wrinkle removal, hair removal), urology (treatment of BPH), and ophthalmology (laser vision correction) continued to boost sales in 1997 and are likely to do so in 1998 (20% expected growth). The laser technologies that will benefit the most from these medical applications are ruby (hair removal), excimer (ophthalmology) and CO2 lasers (skin resurfacing). The control and the monitoring of the energy delivered by these lasers are critical for the success and the repeatability of the treatments. According to the application, lasers are used in Q-switched mode or long-pulse mode, we will present the both the suitable way to make in-situ measurement of the energy delivered by the laser. The second part of the presentation will focus on the on-line monitoring solution and its great advantages for the operator and the patient.

  15. Coherent beam combiner for a high power laser

    DOEpatents

    Dane, C. Brent; Hackel, Lloyd A.

    2002-01-01

    A phase conjugate laser mirror employing Brillouin-enhanced four wave mixing allows multiple independent laser apertures to be phase locked producing an array of diffraction-limited beams with no piston phase errors. The beam combiner has application in laser and optical systems requiring high average power, high pulse energy, and low beam divergence. A broad range of applications exist in laser systems for industrial processing, especially in the field of metal surface treatment and laser shot peening.

  16. High power femtosecond lasers at ELI-NP

    SciTech Connect

    Dabu, Razvan

    2015-02-24

    Specifications of the high power laser system (HPLS) designed for nuclear physics experiments are presented. Configuration of the 2 × 10 PW femtosecond laser system is described. In order to reach the required laser beam parameters, advanced laser techniques are proposed for the HPLS: parametric amplification and cross-polarized wave generation for the intensity contrast improvement and spectral broadening, acousto-optic programmable filters to compensate for spectral phase dispersion, optical filters for spectrum management, combined methods for transversal laser suppression.

  17. Benefits of low-power lasers on oral soft tissue

    NASA Astrophysics Data System (ADS)

    de Paula Eduardo, Carlos; Cecchini, Silvia C.; Cecchini, Renata C.

    1996-04-01

    The last five years have represented a great advance in relation to laser development. Countries like Japan, United States, French, England, Israel and others, have been working on the association of researches and clinical applications, in the field of laser. Low power lasers like He-Ne laser, emitting at 632,8 nm and Ga-As-Al laser, at 790 nm, have been detached acting not only as a coadjutant but some times as an specific treatment. Low power lasers provide non thermal effect at wavelengths believed to stimulate circulation and cellular activity. These lasers have been used to promote wound healing and reduce inflammation edema and pain. This work presents a five year clinical study with good results related to oral tissue healing. Oral cavity lesions, like herpes and aphthous ulcers were irradiated with Ga-Al- As laser. In both cases, an excellent result was obtained. The low power laser application decrease the painful sintomatology immediately and increase the reparation process of these lesions. An excellent result was obtained with application of low power laser in herpetic lesions associated with a secondary infection situated at the lip commissure covering the internal tissue of the mouth. The healing occurred after one week. An association of Ga-Al-As laser and Nd:YAG laser have been also proven to be good therapy for these kind of lesions. This association of low and high power laser has been done since 1992 and it seems to be a complement of the conventional therapies.

  18. Processing of diamond by laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Masanori; Hirata, Atsushi

    1998-10-01

    YAG and ArF excimer laser beams, of which wavelengths are 1.06 micrometers and 193 nm respectively, have been applied to processing of a variety of diamonds. Cutting and smoothing of natural, CVD and sintered diamonds have been performed. CVD diamond films were prepared by arc discharge plasma jet CVD and microwave plasma CVD, and sintered diamonds contain metallic or ceramic binder have been used. Fundamental removal processes of diamond with YAG and ArF excimer laser have been investigated using natural single crystal and CVD diamonds in various atmospheres changing laser irradiation conditions such as average power, energy density and pulse repetition rates. Cutting of natural and CVD diamonds with YAG laser proceeds at higher peal power that occurs at lower pulse repetition rates. Smooth surfaces are obtained by excimer laser irradiation at the incident angle of 80 percent. In the cases of the processing with YAG laser, the effect of local heating by laser beam irradiation mainly assists the diamond processing, and diamond appears to be removed after graphitization and oxidization following vaporization in the atmosphere contains oxygen. The temperature measurement was carried out at backside of irradiation surface, and increase of temperature when YAG laser beam was irradiated was larger than that when excimer laser was irradiated. On the contrary, the detection of C, C2, C+, O2 and CO from the emission at the irradiation area with ArF excimer laser beam suggest that processing partly proceeds by the separation of carbon atoms from the surface of diamond after braking bonds between carbon atoms caused by laser beam. Cutting of sintered diamond with metallic binder was difficult because metallic binder remains in the groove while ceramic binder was easily removed. Processing technique using laser beams has been applied to surface planing, chip preparation and edge formation of CVD diamond and curved surface formation on sintered diamond. Surface planing was

  19. High average power scaleable thin-disk laser

    DOEpatents

    Beach, Raymond J.; Honea, Eric C.; Bibeau, Camille; Payne, Stephen A.; Powell, Howard; Krupke, William F.; Sutton, Steven B.

    2002-01-01

    Using a thin disk laser gain element with an undoped cap layer enables the scaling of lasers to extremely high average output power values. Ordinarily, the power scaling of such thin disk lasers is limited by the deleterious effects of amplified spontaneous emission. By using an undoped cap layer diffusion bonded to the thin disk, the onset of amplified spontaneous emission does not occur as readily as if no cap layer is used, and much larger transverse thin disks can be effectively used as laser gain elements. This invention can be used as a high average power laser for material processing applications as well as for weapon and air defense applications.

  20. High-power lasers for directed-energy applications.

    PubMed

    Sprangle, Phillip; Hafizi, Bahman; Ting, Antonio; Fischer, Richard

    2015-11-01

    In this article, we review and discuss the research programs at the Naval Research Laboratory (NRL) on high-power lasers for directed-energy (DE) applications in the atmosphere. Physical processes affecting propagation include absorption/scattering, turbulence, and thermal blooming. The power levels needed for DE applications require combining a number of lasers. In atmospheric turbulence, there is a maximum intensity that can be placed on a target that is independent of the initial beam spot size and laser beam quality. By combining a number of kW-class fiber lasers, scientists at the NRL have successfully demonstrated high-power laser propagation in a turbulent atmosphere and wireless recharging. In the NRL experiments, four incoherently combined fiber lasers having a total power of 5 kW were propagated to a target 3.2 km away. These successful high-power experiments in a realistic atmosphere formed the basis of the Navy's Laser Weapon System. We compare the propagation characteristics of coherently and incoherently combined beams without adaptive optics. There is little difference in the energy on target between coherently and incoherently combined laser beams for multi-km propagation ranges and moderate to high levels of turbulence. Unlike incoherent combining, coherent combining places severe constraints on the individual lasers. These include the requirement of narrow power spectral linewidths in order to have long coherence times as well as polarization alignment of all the lasers. These requirements are extremely difficult for high-power lasers. PMID:26560609

  1. High-power lasers for directed-energy applications.

    PubMed

    Sprangle, Phillip; Hafizi, Bahman; Ting, Antonio; Fischer, Richard

    2015-11-01

    In this article, we review and discuss the research programs at the Naval Research Laboratory (NRL) on high-power lasers for directed-energy (DE) applications in the atmosphere. Physical processes affecting propagation include absorption/scattering, turbulence, and thermal blooming. The power levels needed for DE applications require combining a number of lasers. In atmospheric turbulence, there is a maximum intensity that can be placed on a target that is independent of the initial beam spot size and laser beam quality. By combining a number of kW-class fiber lasers, scientists at the NRL have successfully demonstrated high-power laser propagation in a turbulent atmosphere and wireless recharging. In the NRL experiments, four incoherently combined fiber lasers having a total power of 5 kW were propagated to a target 3.2 km away. These successful high-power experiments in a realistic atmosphere formed the basis of the Navy's Laser Weapon System. We compare the propagation characteristics of coherently and incoherently combined beams without adaptive optics. There is little difference in the energy on target between coherently and incoherently combined laser beams for multi-km propagation ranges and moderate to high levels of turbulence. Unlike incoherent combining, coherent combining places severe constraints on the individual lasers. These include the requirement of narrow power spectral linewidths in order to have long coherence times as well as polarization alignment of all the lasers. These requirements are extremely difficult for high-power lasers.

  2. High power continuous wave injection-locked solid state laser

    SciTech Connect

    Nabors, C.D.; Byer, R.L.

    1991-06-25

    This patent describes an injection locked laser system. It comprises a master laser, the master laser including a solid state gain medium and having a continuous wave, single frequency output; a slave laser including a solid state gain medium located in a resonant cavity and having a continuous wave output at a power at least ten times greater than the master laser, with the output of the master laser being injected into the slave laser in order to cause the slave laser to oscillate at the same frequency as the output of the master laser; and means for actively stabilizing the slave laser so that its output frequency remains locked with the output frequency of the master laser.

  3. High power laser diodes for the NASA direct detection laser transceiver experiment

    NASA Technical Reports Server (NTRS)

    Seery, Bernard D.; Holcomb, Terry L.

    1988-01-01

    High-power semiconductor laser diodes selected for use in the NASA space laser communications experiments are discussed. The diode selection rationale is reviewed, and the laser structure is shown. The theory and design of the third mirror lasers used in the experiments are addressed.

  4. Low-power laser therapy for carpal tunnel syndrome: effective optical power.

    PubMed

    Chen, Yan; Zhao, Cheng-Qiang; Ye, Gang; Liu, Can-Dong; Xu, Wen-Dong

    2016-07-01

    Low-power laser therapy has been used for the non-surgical treatment of mild to moderate carpal tunnel syndrome, although its efficacy has been a long-standing controversy. The laser parameters in low-power laser therapy are closely related to the laser effect on human tissue. To evaluate the efficacy of low-power laser therapy, laser parameters should be accurately measured and controlled, which has been ignored in previous clinical trials. Here, we report the measurement of the effective optical power of low-power laser therapy for carpal tunnel syndrome. By monitoring the backside reflection and scattering laser power from human skin at the wrist, the effective laser power can be inferred. Using clinical measurements from 30 cases, we found that the effective laser power differed significantly among cases, with the measured laser reflection coefficient ranging from 1.8% to 54%. The reflection coefficient for 36.7% of these 30 cases was in the range of 10-20%, but for 16.7% of cases, it was higher than 40%. Consequently, monitoring the effective optical power during laser irradiation is necessary for the laser therapy of carpal tunnel syndrome. PMID:27630706

  5. Low-power laser therapy for carpal tunnel syndrome: effective optical power

    PubMed Central

    Chen, Yan; Zhao, Cheng-qiang; Ye, Gang; Liu, Can-dong; Xu, Wen-dong

    2016-01-01

    Low-power laser therapy has been used for the non-surgical treatment of mild to moderate carpal tunnel syndrome, although its efficacy has been a long-standing controversy. The laser parameters in low-power laser therapy are closely related to the laser effect on human tissue. To evaluate the efficacy of low-power laser therapy, laser parameters should be accurately measured and controlled, which has been ignored in previous clinical trials. Here, we report the measurement of the effective optical power of low-power laser therapy for carpal tunnel syndrome. By monitoring the backside reflection and scattering laser power from human skin at the wrist, the effective laser power can be inferred. Using clinical measurements from 30 cases, we found that the effective laser power differed significantly among cases, with the measured laser reflection coefficient ranging from 1.8% to 54%. The reflection coefficient for 36.7% of these 30 cases was in the range of 10–20%, but for 16.7% of cases, it was higher than 40%. Consequently, monitoring the effective optical power during laser irradiation is necessary for the laser therapy of carpal tunnel syndrome. PMID:27630706

  6. Low-power laser therapy for carpal tunnel syndrome: effective optical power

    PubMed Central

    Chen, Yan; Zhao, Cheng-qiang; Ye, Gang; Liu, Can-dong; Xu, Wen-dong

    2016-01-01

    Low-power laser therapy has been used for the non-surgical treatment of mild to moderate carpal tunnel syndrome, although its efficacy has been a long-standing controversy. The laser parameters in low-power laser therapy are closely related to the laser effect on human tissue. To evaluate the efficacy of low-power laser therapy, laser parameters should be accurately measured and controlled, which has been ignored in previous clinical trials. Here, we report the measurement of the effective optical power of low-power laser therapy for carpal tunnel syndrome. By monitoring the backside reflection and scattering laser power from human skin at the wrist, the effective laser power can be inferred. Using clinical measurements from 30 cases, we found that the effective laser power differed significantly among cases, with the measured laser reflection coefficient ranging from 1.8% to 54%. The reflection coefficient for 36.7% of these 30 cases was in the range of 10–20%, but for 16.7% of cases, it was higher than 40%. Consequently, monitoring the effective optical power during laser irradiation is necessary for the laser therapy of carpal tunnel syndrome.

  7. X-ray contact microscopy using a plasma source generated by long and short (120ns and 10ns) excimer laser pulses

    SciTech Connect

    Cotton, R.; Bollanti, S.; Di Lazzaro, P.

    1995-12-31

    Soft X-ray contact microscopy (SXCM), using a pulsed X-ray source, offers the possibility of imaging the ultrastructure of living biological systems at sub-50nm resolution. The authors have developed a pulsed plasma X-ray source for this application, generated by the large volume XeCl laser Hercules. Various unstable optical resonator configurations were employed to achieve a high laser intensity to increase the conversion efficiency to water window X-rays (280--530 eV). Optimum plasma conditions for SXCM are discussed, including the effect of pulse duration on image resolution. Soft X-ray contact images of Chlamydomonas dysosmos (unicellular alga) and the cyanobacteria Leptolyngbya are shown. In addition, the potential of producing a movie film of the development of X-ray images within the photoresist (acting as the recording medium) is discussed, following the resist development while viewing by atomic force microscopy.

  8. High Power Fiber Lasers and Applications to Manufacturing

    NASA Astrophysics Data System (ADS)

    Richardson, Martin; McComb, Timothy; Sudesh, Vikas

    2008-09-01

    We summarize recent developments in high power fiber laser technologies and discuss future trends, particularly in their current and future use in manufacturing technologies. We will also describe our current research programs in fiber laser development, ultra-fast and new lasers, and will mention the expectations in these areas for the new Townes Laser Institute. It will focus on new core laser technologies and their applications in medical technologies, advanced manufacturing technologies and defense applications. We will describe a program on large mode area fiber development that includes results with the new gain-guiding approach, as well as high power infra-red fiber lasers. We will review the opportunities for high power fiber lasers in various manufacturing technologies and illustrate this with applications we are pursuing in the areas of femtosecond laser applications, advanced lithographies, and mid-IR technologies.

  9. Application of reactor-pumped lasers to power beaming

    SciTech Connect

    Repetti, T.E.

    1991-10-01

    Power beaming is the concept of centralized power generation and distribution to remote users via energy beams such as microwaves or laser beams. The power beaming community is presently performing technical evaluations of available lasers as part of the design process for developing terrestrial and space-based power beaming systems. This report describes the suitability of employing a nuclear reactor-pumped laser in a power beaming system. Although there are several technical issues to be resolved, the power beaming community currently believes that the AlGaAs solid-state laser is the primary candidate for power beaming because that laser meets the many design criteria for such a system and integrates well with the GaAs photodiode receiver array. After reviewing the history and physics of reactor-pumped lasers, the advantages of these lasers for power beaming are discussed, along with several technical issues which are currently facing reactor-pumped laser research. The overriding conclusion is that reactor-pumped laser technology is not presently developed to the point of being technially or economically competitive with more mature solid-state technologies for application to power beaming. 58 refs.

  10. CHRONICLE: International forum on advanced high-power lasers and applications (AHPLA '99)

    NASA Astrophysics Data System (ADS)

    Afanas'ev, Yurii V.; Zavestovskaya, I. N.; Zvorykin, V. D.; Ionin, Andrei A.; Senatsky, Yu V.; Starodub, Aleksandr N.

    2000-05-01

    A review of reports made on the International Forum on Advanced High-Power Lasers and Applications, which was held at the beginning of November 1999 in Osaka (Japan), is presented. Five conferences were held during the forum on High-Power Laser Ablation, High-Power Lasers in Energy Engineering, High-Power Lasers in Civil Engineering and Architecture, High-Power Lasers in Manufacturing, and Advanced High-Power Lasers. The following trends in the field of high-power lasers and their applications were presented: laser fusion, laser applications in space, laser-triggered lightning, laser ablation of materials by short and ultrashort pulses, application of high-power lasers in manufacturing, application of high-power lasers in mining, laser decommissioning and decontamination of nuclear reactors, high-power solid-state and gas lasers, x-ray and free-electron lasers. One can find complete information on the forum in SPIE, vols. 3885-3889.

  11. Freeform beam shaping for high-power multimode lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2014-03-01

    Widening of using high power multimode lasers in industrial laser material processing is accompanied by special requirements to irradiance profiles in such technologies like metal or plastics welding, cladding, hardening, brazing, annealing, laser pumping and amplification in MOPA lasers. Typical irradiance distribution of high power multimode lasers: free space solid state, fiber-coupled solid state and diodes lasers, fiber lasers, is similar to Gaussian. Laser technologies can be essentially improved when irradiance distribution on a workpiece is uniform (flattop) or inverse-Gauss; when building high-power pulsed lasers it is possible to enhance efficiency of pumping and amplification by applying super-Gauss irradiance distribution with controlled convexity. Therefore, "freeform" beam shaping of multimode laser beams is an important task. A proved solution is refractive field mapping beam shaper like Shaper capable to control resulting irradiance profile - with the same unit it is possible to get various beam profiles and choose optimum one for a particular application. Operational principle of these devices implies transformation of laser irradiance distribution by conserving beam consistency, high transmittance, providing collimated low divergent output beam. Using additional optics makes it possible to create resulting laser spots of necessary size and round, elliptical or linear shape. Operation out of focal plane and, hence, in field of lower wavefront curvature, allows extending depth of field. The refractive beam shapers are implemented as telescopes and collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation.

  12. Advances in bonding technology for high power diode laser bars

    NASA Astrophysics Data System (ADS)

    Wang, Jingwei; Li, Xiaoning; Hou, Dong; Feng, Feifei; Liu, Yalong; Liu, Xingsheng

    2015-02-01

    Due to their high electrical-optical conversion efficiency, compact size and long lifetime, high power diode lasers have found increased applications in many fields. As the improvement of device technology, high power diode laser bars with output power of tens or hundreds watts have been commercially available. With the increase of high current and output power, the reliability and lifetime of high power diode laser bars becomes a challenge, especially under harsh working conditions and hard-pulse operations. The bonding technology is still one of the bottlenecks of the advancement of high power diode laser bars. Currently, materials used in bonding high power diode laser bars are commonly indium and goldtin solders. Experimental and field application results indicates that the lifetime and reliability of high power diode laser bars bonded by gold-tin solder is much better than that bonded by indium solder which is prone to thermal fatigue, electro-migration and oxidization. In this paper, we review the bonding technologies for high power diode laser bars and present the advances in bonding technology for single bars, horizontal bar arrays and vertical bar stacks. We will also present the challenges and issues in bonding technology for high power diode laser bars and discuss some approaches and strategies in addressing the challenges and issues.

  13. Improving Reliability of High Power Quasi-CW Laser Diode Arrays for Pumping Solid State Lasers

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Baggott, Renee S.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.

    2005-01-01

    Most Lidar applications rely on moderate to high power solid state lasers to generate the required transmitted pulses. However, the reliability of solid state lasers, which can operate autonomously over long periods, is constrained by their laser diode pump arrays. Thermal cycling of the active regions is considered the primary reason for rapid degradation of the quasi-CW high power laser diode arrays, and the excessive temperature rise is the leading suspect in premature failure. The thermal issues of laser diode arrays are even more drastic for 2-micron solid state lasers which require considerably longer pump pulses compared to the more commonly used pump arrays for 1-micron lasers. This paper describes several advanced packaging techniques being employed for more efficient heat removal from the active regions of the laser diode bars. Experimental results for several high power laser diode array devices will be reported and their performance when operated at long pulsewidths of about 1msec will be described.

  14. Non-intrusive beam power monitor for high power pulsed or continuous wave lasers

    DOEpatents

    Hawsey, Robert A.; Scudiere, Matthew B.

    1993-01-01

    A system and method for monitoring the output of a laser is provided in which the output of a photodiode disposed in the cavity of the laser is used to provide a correlated indication of the laser power. The photodiode is disposed out of the laser beam to view the extraneous light generated in the laser cavity whose intensity has been found to be a direct correlation of the laser beam output power level. Further, the system provides means for monitoring the phase of the laser output beam relative to a modulated control signal through the photodiode monitor.

  15. High Peak Power Gain Switched Flared Waveguide Lasers

    SciTech Connect

    Chow, W.W.; Indik, R.; Koch, S.W.; Mar, Alan, Vawter, G. Allen; Moloney, J.

    1999-08-05

    We gain-switch flared waveguide lasers to obtain 14.5 W peak powers and 0.5 nJ pulse energies with laser structures compatible with the generation of diffraction-limited beams. The results are in excellent agreement with a microscopic laser model.

  16. Industrial CO laser with tens of kilowatt power: technical offer

    NASA Astrophysics Data System (ADS)

    Baranov, Igor Y.

    2005-09-01

    The laser with power tens of kilowatt would be essential for dismantlement of obsolete nuclear-power reactors, laser-hardening the surfaces of railway rails and etc. The production of high power, high efficiency, high specific energy and high optical beam quality can be obtained in the experimental systems of a quasi-cw electroionization CO laser with cooling a CO mixture by its expansion in the nozzles. The way of transfer to industrial high-power CO lasers is proposed through the continuous formation of a CO laser mixture during laser operation. CO laser mixture is formed by using air as a buffer gas (about 90%). CO molecules are generated in oxidation reaction of oxygen-containing molecules with carbon. The carbon arises from a decomposition of hydrocarbon fuel on the catalyst surface. CO mixture is excited by radio-frequency (RF) electric discharge in a supersonic gas flow without an electron gun. The given conception was used on a small-scale model system to demonstrate that the laser radiation was possible in a CO mixture with combustion products and air, which are excited by RF discharge in a supersonic flow. The industrial CO laser with tens of kilowatt power is offer with open working cycle without ejecting toxic CO into the atmosphere by converting CO molecules to C02 ones. The estimated cost of a laser is several hundred thousand and the small sizes of laser give possibility to install its on manipulator without fiber-optic delivery.

  17. Laser surface melting of aluminium alloy 6013 for improving stress corrosion and corrosion fatigue resistance

    NASA Astrophysics Data System (ADS)

    Xu, Wen-Long

    terms of percentage elongation and corrosion current density, the resistance to stress corrosion cracking improved after excimer laser treatment. While the corrosion fatigue results showed that the total fatigue life of the alloy increased noticeably after laser surface treatment. However, a higher overall fatigue crack propagation rate occurred in the laser-treated material. The effect of post-treatment ageing and residual stress on fatigue strength was also investigated; the results showed that they did not have a significant influence. Recognising that the depth of the excimer laser melted layer was very shallow, typically in the range of a few micrometers, this when compared to the melt depth in the hundred micrometer range for Nd-YAG laser treatment may disadvantage excimer laser treatment. As a consequence, a 2kW high power Nd:YAG laser was employed for the LSM experiment during the second phase of this research. It was found that a totally different re-melt microstructure to that of excimer laser melting resulted from YAG laser melting: the depth of the melt pool was in the range of a few hundreds micrometers, and instead of the planar growth morphology that occurred in excimer laser melting, a fine dendritic/cellular structure was produced. Although, an AIN film was produced at the outer surface of the re-melt layer which was similar to that of excimer laser melting, the YAG laser formed film was much thicker with larger crystallines of the nitride phase. With regard to pitting corrosion resistance, although improvement was obtained after YAG laser melting, the improvement was not as significant as that which can be achieved by excimer laser melting. This is mainly because the second phase particles at the dendrite boundaries behaved as cathodic sites while the dendrite cells acted as anodic sites. The results of the equivalent circuit modelling showed that the polarisation resistance of the YAG laser formed surface film was one order of magnitude lower than

  18. Measuring laser power as a force: a new paradigm to accurately monitor optical power during laser-based machining operations

    NASA Astrophysics Data System (ADS)

    Williams, Paul; Simonds, Brian; Sowards, Jeffrey; Hadler, Joshua

    2016-03-01

    In laser manufacturing operations, accurate measurement of laser power is important for product quality, operational repeatability, and process validation. Accurate real-time measurement of high-power lasers, however, is difficult. Typical thermal power meters must absorb all the laser power in order to measure it. This constrains power meters to be large, slow and exclusive (that is, the laser cannot be used for its intended purpose during the measurement). To address these limitations, we have developed a different paradigm in laser power measurement where the power is not measured according to its thermal equivalent but rather by measuring the laser beam's momentum (radiation pressure). Very simply, light reflecting from a mirror imparts a small force perpendicular to the mirror which is proportional to the optical power. By mounting a high-reflectivity mirror on a high-sensitivity force transducer (scale), we are able to measure laser power in the range of tens of watts up to ~ 100 kW. The critical parameters for such a device are mirror reflectivity, angle of incidence, and scale sensitivity and accuracy. We will describe our experimental characterization of a radiation-pressure-based optical power meter. We have tested it for modulated and CW laser powers up to 92 kW in the laboratory and up to 20 kW in an experimental laser welding booth. We will describe present accuracy, temporal response, sources of measurement uncertainty, and hurdles which must be overcome to have an accurate power meter capable of routine operation as a turning mirror within a laser delivery head.

  19. Photovoltaic receivers for laser beamed power in space

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1991-01-01

    There has recently been a resurgence of interest in the use of beamed power to support space exploration activities. One of the most promising beamed power concepts uses a laser beam to transmit power to a remote photovoltaic array. Large lasers can be located on cloud-free sites at one or more ground locations and illuminate solar arrays to a level sufficient to provide operating power. Issues involved in providing photovoltaic receivers for such applications are discussed.

  20. High power solid state laser modulator

    DOEpatents

    Birx, Daniel L.; Ball, Don G.; Cook, Edward G.

    2004-04-27

    A multi-stage magnetic modulator provides a pulse train of .+-.40 kV electrical pulses at a 5-7 kHz repetition rate to a metal vapor laser. A fractional turn transformer steps up the voltage by a factor of 80 to 1 and magnetic pulse compression is used to reduce the pulse width of the pulse train. The transformer is fabricated utilizing a rod and plate stack type of construction to achieve a high packing factor. The pulses are controlled by an SCR stack where a plurality of SCRs are electrically connected in parallel, each SCR electrically connected to a saturable inductor, all saturable inductors being wound on the same core of magnetic material for enhanced power handling characteristics.

  1. Development of High Average Power Lasers for the Photon Collider

    SciTech Connect

    Gronberg, Jeff; Stuart, Brent; Seryi, Andrei; /SLAC

    2012-07-05

    The laser and optics system for the photon collider seeks to minimize the required laser power by using an optical stacking cavity to recirculate the laser light. An enhancement of between 300 to 400 is desired. In order to achieve this the laser pulses which drive the cavity must precisely match the phase of the pulse circulating within the cavity. We report on simulations of the performance of a stacking cavity to various variations of the drive laser in order to specify the required tolerances of the laser system.

  2. 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.

  3. Hybrid Laser Would Combine Power With Efficiency

    NASA Technical Reports Server (NTRS)

    Sipes, Donald L., Jr

    1986-01-01

    Efficient laser system constructed by using two semiconductor lasers to pump neodymium yttrium aluminum garnet (Nd:YAG) device. Hybrid concept allows digital transmission at data rates of several megabits per second with reasonably sized optical aperture of 20 cm. Beams from two GaAs lasers efficiently coupled for pumping Nd:YAG crystal. Combination of lasers exploits best features of each.

  4. High power semiconductor lasers for deep space communications

    NASA Technical Reports Server (NTRS)

    Katz, J.

    1981-01-01

    The parameters of semiconductor lasers pertaining to their application as optical emitters are discussed. Several methods to overcome their basic disadvantage, which is the low level of powers they emit, are reviewed. Most of these methods are based on a coherent power combining of several lasers.

  5. Power blue and green laser diodes and their applications

    NASA Astrophysics Data System (ADS)

    Hager, Thomas; Strauß, Uwe; Eichler, Christoph; Vierheilig, Clemens; Tautz, Sönke; Brüderl, Georg; Stojetz, Bernhard; Wurm, Teresa; Avramescu, Adrian; Somers, André; Ristic, Jelena; Gerhard, Sven; Lell, Alfred; Morgott, Stefan; Mehl, Oliver

    2013-03-01

    InGaN based green laser diodes with output powers up to 50mW are now well established for variety of applications ranging from leveling to special lighting effects and mobile projection of 12lm brightness. In future the highest market potential for visible single mode profile lasers might be laser projection of 20lm. Therefore direct green single-mode laser diodes with higher power are required. We found that self heating was the limiting factor for higher current operation. We present power-current characteristics of improved R and D samples with up to 200mW in cw-operation. An optical output power of 100mW is reached at 215mA, a current level which is suitable for long term operation. Blue InGaN laser diodes are also the ideal source for phosphor based generation of green light sources of high luminance. We present a light engine based on LARP (Laser Activated Remote Phosphor) which can be used in business projectors of several thousand lumens on screen. We discuss the advantages of a laser based systems in comparison with LED light engines. LARP requires highly efficient blue power laser diodes with output power above 1W. Future market penetration of LARP will require lower costs. Therefore we studied new designs for higher powers levels. R and D chips with power-current characteristics up to 4W in continuous wave operation on C-mount at 25°C are presented.

  6. Overview of the NASA high power laser program

    NASA Technical Reports Server (NTRS)

    Lundholm, J. G.

    1976-01-01

    The overall objectives of the NASA High Power Laser Program are reviewed along with their structure and center responsibilities. Present and future funding, laser power transmission in space, selected program highlights, the research and technology schedule, and the expected pace of the program are briefly considered.

  7. A stable, high power optically pumped far infrared laser system

    NASA Technical Reports Server (NTRS)

    Farhoomand, Jam; Pickett, Herbert M.

    1988-01-01

    The generation of 1.25 watts of CW laser power at the 119-micron (2522.8 GHz) methanol line is reported. The maximum frequency fluctuation of the free running laser is less than + or - 100 kHz per hour. This laser has also been tested on numerous other lines ranging from 403.7 GHz (HCOOH) to 5260 GHz (CH3OD) with improved power and stability.

  8. High-power laser diodes at various wavelengths

    SciTech Connect

    Emanuel, M.A.

    1997-02-19

    High power laser diodes at various wavelengths are described. First, performance and reliability of an optimized large transverse mode diode structure at 808 and 941 nm are presented. Next, data are presented on a 9.5 kW peak power array at 900 nm having a narrow emission bandwidth suitable for pumping Yb:S-FAP laser materials. Finally, results on a fiber-coupled laser diode array at {approx}730 nm are presented.

  9. High power laser downhole cutting tools and systems

    SciTech Connect

    Zediker, Mark S; Rinzler, Charles C; Faircloth, Brian O; Koblick, Yeshaya; Moxley, Joel F

    2015-01-20

    Downhole cutting systems, devices and methods for utilizing 10 kW or more laser energy transmitted deep into the earth with the suppression of associated nonlinear phenomena. Systems and devices for the laser cutting operations within a borehole in the earth. These systems and devices can deliver high power laser energy down a deep borehole, while maintaining the high power to perform cutting operations in such boreholes deep within the earth.

  10. High-power direct-diode laser successes

    NASA Astrophysics Data System (ADS)

    Haake, John M.; Zediker, Mark S.

    2004-06-01

    Direct diode laser will become much more prevalent in the solar system of manufacturing due to their high efficiency, small portable size, unique beam profiles, and low ownership costs. There has been many novel applications described for high power direct diode laser [HPDDL] systems but few have been implemented in extreme production environments due to diode and diode system reliability. We discuss several novel applications in which the HPDDL have been implemented and proven reliable and cost-effective in production environments. These applications are laser hardening/surface modification, laser wire feed welding and laser paint stripping. Each of these applications uniquely tests the direct diode laser systems capabilities and confirms their reliability in production environments. A comparison of the advantages direct diode laser versus traditional industrial lasers such as CO2 and Nd:YAG and non-laser technologies such a RF induction, and MIG welders for each of these production applications is presented.

  11. Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms

    SciTech Connect

    Hosoya, Toshiyuki; Miranda, Martin; Inoue, Ryotaro; Kozuma, Mikio

    2015-07-15

    We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources for laser cooling experiments including transportable optical lattice clocks.

  12. High-Power Solid-State Lasers from a Laser Glass Perspective

    SciTech Connect

    Campbell, J H; Hayden, J S; Marker, A J

    2010-12-17

    Advances in laser glass compositions and manufacturing have enabled a new class of high-energy/high-power (HEHP), petawatt (PW) and high-average-power (HAP) laser systems that are being used for fusion energy ignition demonstration, fundamental physics research and materials processing, respectively. The requirements for these three laser systems are different necessitating different glasses or groups of glasses. The manufacturing technology is now mature for melting, annealing, fabricating and finishing of laser glasses for all three applications. The laser glass properties of major importance for HEHP, PW and HAP applications are briefly reviewed and the compositions and properties of the most widely used commercial laser glasses summarized. Proposed advances in these three laser systems will require new glasses and new melting methods which are briefly discussed. The challenges presented by these laser systems will likely dominate the field of laser glass development over the next several decades.

  13. High power diode laser Master Oscillator-Power Amplifier (MOPA)

    NASA Technical Reports Server (NTRS)

    Andrews, John R.; Mouroulis, P.; Wicks, G.

    1994-01-01

    High power multiple quantum well AlGaAs diode laser master oscillator - power amplifier (MOPA) systems were examined both experimentally and theoretically. For two pass operation, it was found that powers in excess of 0.3 W per 100 micrometers of facet length were achievable while maintaining diffraction-limited beam quality. Internal electrical-to-optical conversion efficiencies as high as 25 percent were observed at an internal amplifier gain of 9 dB. Theoretical modeling of multiple quantum well amplifiers was done using appropriate rate equations and a heuristic model of the carrier density dependent gain. The model gave a qualitative agreement with the experimental results. In addition, the model allowed exploration of a wider design space for the amplifiers. The model predicted that internal electrical-to-optical conversion efficiencies in excess of 50 percent should be achievable with careful system design. The model predicted that no global optimum design exists, but gain, efficiency, and optical confinement (coupling efficiency) can be mutually adjusted to meet a specific system requirement. A three quantum well, low optical confinement amplifier was fabricated using molecular beam epitaxial growth. Coherent beam combining of two high power amplifiers injected from a common master oscillator was also examined. Coherent beam combining with an efficiency of 93 percent resulted in a single beam having diffraction-limited characteristics. This beam combining efficiency is a world record result for such a system. Interferometric observations of the output of the amplifier indicated that spatial mode matching was a significant factor in the less than perfect beam combining. Finally, the system issues of arrays of amplifiers in a coherent beam combining system were investigated. Based upon experimentally observed parameters coherent beam combining could result in a megawatt-scale coherent beam with a 10 percent electrical-to-optical conversion efficiency.

  14. The NASA high power carbon dioxide laser: A versatile tool for laser applications

    NASA Technical Reports Server (NTRS)

    Lancashire, R. B.; Alger, D. L.; Manista, E. J.; Slaby, J. G.; Dunning, J. W.; Stubbs, R. M.

    1976-01-01

    A closed-cycle, continuous wave, carbon dioxide high power laser has been designed and fabricated to support research for the identification and evaluation of possible high power laser applications. The device is designed to generate up to 70 kW of laser power in annular shape beams from 1 to 9 cm in diameter. Electric discharge, either self sustained or electron beam sustained, is used for excitation. This laser facility provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams. The facility provides a well defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.

  15. A sensitive and high dynamic range cw laser power meter

    NASA Astrophysics Data System (ADS)

    Krishnan, S.; Bindra, K. S.; Oak, S. M.

    2008-12-01

    We report the design of a cost effective, highly sensitive cw laser power meter with a large dynamic range based on a photodiode. The power meter consists of a photodiode, a current to voltage converter circuit, an offset balancing circuit, a microcontroller, an analog to digital converter, reed relays, and an alphanumeric liquid crystal display. The power meter can record absolute laser power levels as low as 1 pW. The dynamic range measured with a cw laser at a wavelength of 532 nm is 8×1010. The high sensitivity and large dynamic range are achieved by the implementation of an analog background balancing circuit and autoranging.

  16. FY2002 Progress Summary Program Plan, Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers, and Complementary Technologies, for Applications in Energy and Defense

    SciTech Connect

    Bayramian, A; Bibeau, C; Beach, R; Behrendt, B; Ebbers, C; Latkowski, J; Meier, W; Payne, S; Perkins, J; Schaffers, K; Skulina, K; Ditmire, T; Kelly, J; Waxer, L; Rudi, P; Randles, M; Witter, D; Meissner, H; Merissner, O

    2001-12-13

    The High Average Power Laser Program (HAPL) is a multi-institutional, coordinated effort to develop a high-energy, repetitively pulsed laser system for Inertial Fusion Energy and other DOE and DOD applications. This program is building a laser-fusion energy base to complement the laser-fusion science developed by DOE Defense programs over the past 25 years. The primary institutions responsible for overseeing and coordinating the research activities are the Naval Research Laboratory (NRL) and LLNL. The current LLNL proposal is a companion proposal to that submitted by NRL, for which the driver development element is focused on the krypton fluoride excimer laser option. Aside from the driver development aspect, the NRL and LLNL companion proposals pursue complementary activities with the associated rep-rated laser technologies relating to target fabrication, target injection, final optics, fusion chamber, materials and power plant economics. This report requests continued funding in FY02 to support LLNL in its program to build a 1kW, 100J, diode-pumped, crystalline laser. In addition, research in high gain laser target design, fusion chamber issues and survivability of the final optic element will be pursued. These technologies are crucial to the feasibility of inertial fusion energy power plants and also have relevance in rep-rated stewardship experiments.

  17. Solar power satellite system definition study. Volume 3: Laser SPS analysis, phase 3

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The potential use of lasers for transmitting power to Earth from Solar Power Satellites was examined. Free electron lasers appear most promising and would have some benefits over microwave power transmission. Further research in laser technology is needed.

  18. Processing of concretes with a high power CO 2 laser

    NASA Astrophysics Data System (ADS)

    Rao, B. Tirumala; Kumar, Harish; Nath, A. K.

    2005-07-01

    Laser material processing, being a non-contact process, minimizes many of the complexities involved in the decontamination and decommissioning of nuclear facilities. A high power laser beam incident on a concrete surface can produce spalling, glazing or vaporization, depending upon the laser power density and scan speed. This paper presents effect of various laser processing parameters on the efficiency of material removal by surface spalling and glazing. The size of laser beam at constant fluence or energy density had significantly different effect on the spalling process. In thick concrete block cutting the flow or removal of molten material limits the cutting depth. By employing repeated laser glazing followed by mechanical scrubbing process cutting of 150 mm thick concrete block was carried out. Gravitation force was utilized for molten materials to flow out while drilling holes on vertical concrete walls. The dependence of the incident laser beam angle on drilling time was experimentally studied.

  19. Trends in high power laser applications in civil engineering

    NASA Astrophysics Data System (ADS)

    Wignarajah, Sivakumaran; Sugimoto, Kenji; Nagai, Kaori

    2005-03-01

    This paper reviews the research and development efforts made on the use of lasers for material processing in the civil engineering industry. Initial investigations regarding the possibility of using lasers in civil engineering were made in the 1960s and '70s, the target being rock excavation. At that time however, the laser powers available were too small for any practical application utilization. In the 1980's, the technology of laser surface cleaning of historically important structures was developed in Europe. In the early 1990s, techniques of laser surface modification, including glazing and coloring of concrete, roughening of granite stones, carbonization of wood were pursued, mainly in Japan. In the latter part of the decade, techniques of laser decontamination of concrete surfaces in nuclear facilities were developed in many countries, and field tests were caried out in Japan. The rapid advances in development of diode lasers and YAG lasers with high power outputs and efficiencies since the late 1990's have led to a revival of worldwide interest in the use of lasers for material processing in civil engineering. The authors believe that, in the next 10 years or so, the advent of compact high power lasers is likely to lead to increased use of lasers of material processing in the field of civil engineering.

  20. Space Solar Power Technology Demonstration for Lunar Polar Applications: Laser-Photovoltaic Wireless Power Transmission

    NASA Technical Reports Server (NTRS)

    Henley, M. W.; Fikes, J. C.; Howell, J.; Mankins, J. C.; Howell, Joe T. (Technical Monitor)

    2002-01-01

    Space Solar Power technology offers unique benefits for near-term NASA space science missions, which can mature this technology for other future applications. "Laser-Photo-Voltaic Wireless Power Transmission" (Laser-PV WPT) is a technology that uses a laser to beam power to a photovoltaic receiver, which converts the laser's light into electricity. Future Laser-PV WPT systems may beam power from Earth to satellites or large Space Solar Power satellites may beam power to Earth, perhaps supplementing terrestrial solar photo-voltaic receivers. In a near-term scientific mission to the moon, Laser-PV WPT can enable robotic operations in permanently shadowed lunar polar craters, which may contain ice. Ground-based technology demonstrations are proceeding, to mature the technology for this initial application, in the moon's polar regions.

  1. Space power by ground-based laser transmission

    SciTech Connect

    Landis, G.A. NASA, Lewis Research Center, Cleveland, OH )

    1992-07-01

    A new method for providing power to space vehicles consists of using high-power CW lasers on the ground to beam power to photovoltaic receivers in space. Such large lasers could be located at cloud-free sites at one or more ground locations, and use large mirrors with adaptive optical correction to reduce the beam spread due to diffraction or atmospheric turbulence. This can result in lower requirements for battery storage, due to continuous illumination of arrays even during periods of shadow by the earth, and higher power output, due to the higher efficiency of photovoltaic arrays under laser illumination compared to solar and the ability to achieve higher intensities of illumination. Applications include providing power for satellites during eclipse, providing power to resurrect satellites which are failing due to solar array degradation, powering orbital transfer vehicles or lunar transfer shuttles, and providing night power to a solar array on the moon. 22 refs.

  2. 1047 nm laser diode master oscillator Nd:YLF power amplifier laser system

    NASA Technical Reports Server (NTRS)

    Yu, A. W.; Krainak, M. A.; Unger, G. L.

    1993-01-01

    A master oscillator power amplifier (MOPA) laser transmitter system at 1047 nm wavelength using a semiconductor laser diode and a diode pumped solid state (Nd:YLF) laser (DPSSL) amplifier is described. A small signal gain of 23 dB, a near diffraction limited beam, 1 Gbit/s modulation rates and greater than 0.6 W average power are achieved. This MOPA laser has the advantage of amplifying the modulation signal from the laser diode master oscillator (MO) with no signal degradation.

  3. Dependence of terahertz power from laser-produced plasma on laser intensity

    NASA Astrophysics Data System (ADS)

    Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.

    2012-07-01

    Power of terahertz radiation from plasma which is generated from air irradiated by coupled (ω, 2ω) femtosecond laser pulses is analyzed for high laser intensities, for which non-linear plasma effects on the pulse propagation become essential, with multidimensional particle-in-cell simulations including the self-consistent plasma kinetics. The growth rate of THz power becomes slower as the laser intensity increases. A reason of such a lowering of efficiency in THz emission is found to be ionization of air by the laser pulse, which results in poor focusing of laser pulses.

  4. Optimal laser wavelength for efficient laser power converter operation over temperature

    NASA Astrophysics Data System (ADS)

    Höhn, O.; Walker, A. W.; Bett, A. W.; Helmers, H.

    2016-06-01

    A temperature dependent modeling study is conducted on a GaAs laser power converter to identify the optimal incident laser wavelength for optical power transmission. Furthermore, the respective temperature dependent maximal conversion efficiencies in the radiative limit as well as in a practically achievable limit are presented. The model is based on the transfer matrix method coupled to a two-diode model, and is calibrated to experimental data of a GaAs photovoltaic device over laser irradiance and temperature. Since the laser wavelength does not strongly influence the open circuit voltage of the laser power converter, the optimal laser wavelength is determined to be in the range where the external quantum efficiency is maximal, but weighted by the photon flux of the laser.

  5. High-power synchronously pumped femtosecond Raman fiber laser.

    PubMed

    Churin, D; Olson, J; Norwood, R A; Peyghambarian, N; Kieu, K

    2015-06-01

    We report a high-power synchronously pumped femtosecond Raman fiber laser operating in the normal dispersion regime. The Raman laser is pumped by a picosecond Yb(3+)-doped fiber laser. It produces highly chirped pulses with energy up to 18 nJ, average power of 0.76 W and 88% efficiency. The pulse duration is measured to be 147 fs after external compression. We observed two different regimes of operation of the laser: coherent and noise-like regime. Both regimes were experimentally characterized. Numerical simulations are in a good agreement with experimental results. PMID:26030549

  6. Laser photovoltaic power system synergy for SEI applications

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Hickman, J. M.

    1991-01-01

    Solar arrays can provide reliable space power, but do not operate when there is no solar energy. Photovoltaic arrays can also convert laser energy with high efficiency. One proposal to reduce the required mass of energy storage required is to illuminate the photovoltaic arrays by a ground laser system. It is proposed to locate large lasers on cloud-free sites at one or more ground locations, and use large lenses or mirrors with adaptive optical correction to reduce the beam spread due to diffraction or atmospheric turbulence. During the eclipse periods or lunar night, the lasers illuminate the solar arrays to a level sufficient to provide operating power.

  7. Molecular Dynamics Simulations of Laser Powered Carbon Nanotube Gears

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Globus, Al; Han, Jie; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    Dynamics of laser powered carbon nanotube gears is investigated by molecular dynamics simulations with Brenner's hydrocarbon potential. We find that when the frequency of the laser electric field is much less than the intrinsic frequency of the carbon nanotube, the tube exhibits an oscillatory pendulam behavior. However, a unidirectional rotation of the gear with oscillating frequency is observed under conditions of resonance between the laser field and intrinsic gear frequencies. The operating conditions for stable rotations of the nanotube gears, powered by laser electric fields are explored, in these simulations.

  8. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    SciTech Connect

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.

    1989-04-01

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10/sup 12/ watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10/sup 9/ watts) and can be focussed to intensities of /approximately/10/sup 16/ W/cm/sup 2/. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs.

  9. Robotics For High Power Laser Beam Manipulation

    NASA Astrophysics Data System (ADS)

    Watson, Henry E.

    1989-03-01

    The research and development programs in manufacturing science at The Pennsylvania State University have a major emphasis on laser materials processing technology development. A major thrust of this program is the development of an intelligent robotic system which can manipulate a laser beam in three dimension with the precision required for welding. The robot is called LARS for Laser Articulated Robotic System. A gantry based robot was selected as the foundation for LARS and the system is divided into five major subsystems: robot, electronic control, vision, workhead, beam transport, and software. An overview of the Laser Robotics program including laser materials processing research programs will be provided.

  10. Atmospheric propagation and combining of high-power lasers.

    PubMed

    Nelson, W; Sprangle, P; Davis, C C

    2016-03-01

    In this paper, we analyze beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations that occur on subnanosecond time scales. Coherently combining these high-power lasers would involve instruments capable of precise phase control and operation at rates greater than ∼10  GHz. To the best of our knowledge, this technology does not currently exist. This presents a challenging problem when attempting to phase lock high-power lasers that is not encountered when phase locking low-power lasers, for example, at milliwatt power levels. Regardless, we demonstrate that even if instruments are developed that can precisely control the phase of high-power lasers, coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Through simulations, we find that coherent beam combining in moderate turbulence and over multikilometer propagation distances has little advantage over incoherent combining. Additionally, in cases of strong turbulence and multikilometer propagation ranges, we find nearly indistinguishable intensity profiles and virtually no difference in the energy on the target between coherently and incoherently combined laser beams. Consequently, we find that coherent beam combining at the transmitter plane is ineffective under typical atmospheric conditions.

  11. Atmospheric propagation and combining of high-power lasers.

    PubMed

    Nelson, W; Sprangle, P; Davis, C C

    2016-03-01

    In this paper, we analyze beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations that occur on subnanosecond time scales. Coherently combining these high-power lasers would involve instruments capable of precise phase control and operation at rates greater than ∼10  GHz. To the best of our knowledge, this technology does not currently exist. This presents a challenging problem when attempting to phase lock high-power lasers that is not encountered when phase locking low-power lasers, for example, at milliwatt power levels. Regardless, we demonstrate that even if instruments are developed that can precisely control the phase of high-power lasers, coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Through simulations, we find that coherent beam combining in moderate turbulence and over multikilometer propagation distances has little advantage over incoherent combining. Additionally, in cases of strong turbulence and multikilometer propagation ranges, we find nearly indistinguishable intensity profiles and virtually no difference in the energy on the target between coherently and incoherently combined laser beams. Consequently, we find that coherent beam combining at the transmitter plane is ineffective under typical atmospheric conditions. PMID:26974640

  12. Laser plasma influence on the space-time structure of powerful laser radiation

    NASA Astrophysics Data System (ADS)

    Ananyin, O. B.; Bogdanov, G. S.; Vovchenko, E. D.; Gerasimov, I. A.; Kuznetsov, A. P.; Melekhov, A. P.

    2016-01-01

    This paper deals with the influence of laser plasma on the structure of the radiation field of a powerful Nd-glass laser with pulse energy up to 30 J and with the diameter of the output beam 45 mm. Laser plasma is generated by focusing the laser radiation on a low-density target such as nylon mesh and teflon or mylar films. Temporal profile of the laser pulse with a total duration of 25 ns consists of a several short pulse train. Duration of each pulse is about 2 ns. Notable smoothing of spatially non-uniform radiation structure was observed in the middle of the laser pulse.

  13. YO A{sup 2}II{sub 1/2,3/2} vibrational state distributions measured after the excimer laser ablation of Y{sub 2}O{sub 3} using a laser-initiated pulsed discharge as a probe

    SciTech Connect

    Fried, D.; Kushida, T.; Reck, G.P.; Rothe, E.W.

    1994-02-01

    The vibrational populations of the YO A{sup 2}II-{Chi}{sup 2}{Sigma} system of YO were measured in the plasmas generated after the excimer laser ablation of Y{sub 2}O{sub 3} in oxygen when both continuous and pulsed electric fields were applied. When an electric field is applied antiparallel to the direction of propagation of the ejected electrons, two luminous plumes appear, separated by several microseconds. The measured vibrational populations of the YO A{sup 2}II-{Chi}{sup 2}{Sigma} system are different for each plume. The YO A{sup 2}II populations were nonthermal in the first plume, representing emission from chemiluminescent reactive collisions in the plume after ablation. The second emission pulse, initiated by the discharge of a high-voltage capacitor, probes the ground-state YO in the plume via electron collisions. This pulsed electric field holds promise as a diagnostic probe of the ground-state species emitted in laser ablative processes. 11 refs., 5 figs., 1 tab.

  14. High-power laser applications in Nippon Steel Corporation

    NASA Astrophysics Data System (ADS)

    Minamida, Katsuhiro

    2000-02-01

    The laser, which was invented in 1960, has been developed using various substances of solids, liquids, gases and semiconductors as laser active media. Applications of laser utilizing the coherent properties of laser light and the high power density light abound in many industries and in heavy industries respectively. The full-scale use of lasers in the steel industry began nearly 23 years ago with their applications as controllable light sources. Its contribution to the increase in efficiency and quality of the steel making process has been important and brought us the saving of the energy, the resource and the labor. Laser applications in the steel making process generally require high input energy, so it is essential to consider the interaction between the laser beam and the irradiated material. In particular, the reflectivity of the laser beam on the surface of material and the quantity of the laser-induced plasma are critical parameters for high efficient processes with low energy losses. We have developed plenty of new laser systems for the steel making process with their considerations in mind. A review of the following high-power-laser applications is given in the present paper: (1) Use of plasma as a secondary heat source in CO2 laser welding for connecting steel sheets of various grades. (2) Laser-assisted electric resistance welding of pipes. (3) New type all-laser-welded honeycomb panels for high-speed transport. (4) Laser flying welder for continuous hot rolling mill using two 45 kW CO2 lasers.

  15. High average power diode pumped solid state lasers for CALIOPE

    SciTech Connect

    Comaskey, B.; Halpin, J.; Moran, B.

    1994-07-01

    Diode pumping of solid state media offers the opportunity for very low maintenance, high efficiency, and compact laser systems. For remote sensing, such lasers may be used to pump tunable non-linear sources, or if tunable themselves, act directly or through harmonic crystals as the probe. The needs of long range remote sensing missions require laser performance in the several watts to kilowatts range. At these power performance levels, more advanced thermal management technologies are required for the diode pumps. The solid state laser design must now address a variety of issues arising from the thermal loads, including fracture limits, induced lensing and aberrations, induced birefringence, and laser cavity optical component performance degradation with average power loading. In order to highlight the design trade-offs involved in addressing the above issues, a variety of existing average power laser systems are briefly described. Included are two systems based on Spectra Diode Laboratory`s water impingement cooled diode packages: a two times diffraction limited, 200 watt average power, 200 Hz multi-rod laser/amplifier by Fibertek, and TRW`s 100 watt, 100 Hz, phase conjugated amplifier. The authors also present two laser systems built at Lawrence Livermore National Laboratory (LLNL) based on their more aggressive diode bar cooling package, which uses microchannel cooler technology capable of 100% duty factor operation. They then present the design of LLNL`s first generation OPO pump laser for remote sensing. This system is specified to run at 100 Hz, 20 nsec pulses each with 300 mJ, less than two times diffraction limited, and with a stable single longitudinal mode. The performance of the first testbed version will be presented. The authors conclude with directions their group is pursuing to advance average power lasers. This includes average power electro-optics, low heat load lasing media, and heat capacity lasers.

  16. Completely monolithic linearly polarized high-power fiber laser oscillator

    NASA Astrophysics Data System (ADS)

    Belke, Steffen; Becker, Frank; Neumann, Benjamin; Ruppik, Stefan; Hefter, Ulrich

    2014-03-01

    We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M² < 1.2). Pump power is delivered via a high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers. Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed1. Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

  17. Frequency-doubled monolithic master oscillator power amplifier laser diode

    SciTech Connect

    Waarts, R.; Sanders, S.; Parke, R.; Mehuys, D.; Lang, R.; O'Brien, S.; Dzurko, K.; Welch, D.; Scifres, D. )

    1993-10-01

    Single-pass frequency doubling of laser diodes extends the wavelength range of infrared laser diodes to blue-green wavelengths. The authors describe the first experiments of frequency doubling of a coherent, high-power, monolithic master oscillator power amplifier (M-MOPA) laser diode. The output from a 1-W M-MOPA is frequency doubled in a single pass through an 8.2-mm-long KNbO[sub 3] crystal. They obtained 3.7-mW diffraction-limited output power at a wavelength of 491 nm and demonstrated modulation at 20 MHz.

  18. Comparisons of selected laser beam power missions to conventionally powered missions

    NASA Technical Reports Server (NTRS)

    Bozek, John M.; Oleson, Steven R.; Landis, Geoffrey A.; Stavnes, Mark W.

    1993-01-01

    Earth-based laser sites beaming laser power to space assets have shown benefits over competing power system concepts for specific missions. Missions analyzed in this report that show benefits of laser beam power are low Earth orbit (LEO) to geosynchronous Earth orbit (GEO) transfer, LEO to low lunar orbit (LLO) cargo missions, and lunar-base power. Both laser- and solar-powered orbit-transfer vehicles (OTV's) make a 'tug' concept viable, which substantially reduces cumulative initial mass to LEO in comparison to chemical propulsion concepts. Lunar cargo missions utilizing laser electric propulsion from Earth-orbit to LLO show substantial mass saving to LEO over chemical propulsion systems. Lunar-base power system options were compared on a landed-mass basis. Photovoltaics with regenerative fuel cells, reactor-based systems, and laser-based systems were sized to meet a generic lunar-base power profile. A laser-based system begins to show landed mass benefits over reactor-based systems when proposed production facilities on the Moon require power levels greater than approximately 300 kWe. Benefit/cost ratios of laser power systems for an OTV, both to GEO and LLO, and for a lunar base were calculated to be greater than 1.

  19. High power CW iodine laser pumped by solar simulator

    NASA Technical Reports Server (NTRS)

    Lee, Ja H.; Lee, Min H.; Weaver, Willard R.

    1987-01-01

    An iodine photodissociation laser was pumped by a long Ar arc as the solar simulator to produce a 10-W CW output. Continuous lasing for 1 h was achieved with a flow of the laser material n-C3F7I. The 10-W CW output is the highest produced to date and establishes the feasibility of developing a solar-pumped laser for space power transmission.

  20. Solid state laser media driven by remote nuclear powered fluorescence

    DOEpatents

    Prelas, Mark A.

    1992-01-01

    An apparatus is provided for driving a solid state laser by a nuclear powered fluorescence source which is located remote from the fluorescence source. A nuclear reaction produced in a reaction chamber generates fluorescence or photons. The photons are collected from the chamber into a waveguide, such as a fiber optic waveguide. The waveguide transports the photons to the remote laser for exciting the laser.