WorldWideScience

Sample records for excimer laser radiation

  1. excimer laser

    Indian Academy of Sciences (India)

    2014-01-07

    Jan 7, 2014 ... Excimer laser; krypton chloride; UV pre-ionization; gas circulation. PACS No 42.55.Lt. 1. ... active discharge volume is by spark UV radiation created adjacent to both sides of the. Figure 4. Output ... HV electrode, all along its length and spatially modulated to ensure uniform irradiation of the gas volume.

  2. Excimer Laser Etching

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-04-01

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

  3. Excimer Laser Technology

    CERN Document Server

    Basting, Dirk

    2005-01-01

    This comprehensive survey on Excimer Lasers investigates the current range of the technology, applications and devices of this commonly used laser source, as well as the future of new technologies, such as F2 laser technology. Additional chapters on optics, devices and laser systems complete this compact handbook. A must read for laser technology students, process application researchers, engineers or anyone interested in excimer laser technology. An effective and understandable introduction to the current and future status of excimer laser technology.

  4. Study on the electromagnetic radiation characteristics of discharging excimer laser system

    Science.gov (United States)

    Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

    2016-10-01

    Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

  5. Changes in gene expression by 193- and 248-nm excimer laser radiation in cultured human fibroblasts.

    Science.gov (United States)

    Rimoldi, D; Flessate, D M; Samid, D

    1992-09-01

    Tissue ablation by ultraviolet excimer lasers results in exposure of viable cells to subablative doses of radiation. To understand the potential biological consequences better, we have studied changes in gene expression in cultured human skin fibroblasts exposed to either 193- or 248-nm laser light. Northern blot analyses revealed that both treatments up-regulate a common set of genes, including interstitial collagenase, tissue inhibitor of metalloprotease, metallothionein, and the proto-oncogene c-fos. Dose-response and kinetic studies of collagenase induction by 193-nm radiation showed a maximal effect with 60 J/m2 and at approximately 24 h. The induction was still persistent 96 h later. In addition to the commonly affected genes, known to be activated also by conventional UV light (254 nm) and tumor-promoting phorbol esters, other genes were found to be selectively induced by the 193-nm radiation. The heat-shock hsp70 mRNA, undetectable in controls and in cultures irradiated at 248 nm, was transiently induced 8 h after exposure to 193-nm radiation. Furthermore, a selective up-regulation of collagen type I expression was observed. The results indicate that the 193- and 248-nm radiations by excimer lasers elicit specific and different cellular responses, in addition to an overlapping pathway of gene activation common also to UV radiation by germicidal lamps. The laser-induced genes could serve as molecular markers in evaluating cell injury in situ.

  6. Excimer lasers for refractive surgery

    Science.gov (United States)

    Vartapetov, Serge K.

    2003-10-01

    Over the last decade excimer lasers have been broadly used for technological and medical processes. One of the most widespread applications of excimer laser is the clinical use for refractive surgery. Refractive surgery with excimer lasers is the prevalent method for the eye acuity correction. Operation at 193 nanometers, the excimer laser is able to precisely sculpt the corneal surface to correct refractive errors. Both the increase in the accuracy of sculpturing and the predictability of procedures are the key elements of the excimer laser designed for refractive surgery. The novel excimer laser for refractive surgery is offered for small aberration treatment. The excimer laser with both a full aperture Gaussian beam and fly spot system is described. The comparison of different systems of laser correction is reviewed.

  7. The effect of 193 nm excimer laser radiation on the human corneal endothelial cell density

    Energy Technology Data Exchange (ETDEWEB)

    Isager, P.; Hjortdal, J.Oe.; Ehlers, N. [Aarhus Univ. Hospital, Dept. of Ophthalmology, Aarhus (Denmark)

    1996-06-01

    The effect of 193 nm excimer laser radiation on human corneal endothelial cell density was examined. Fifty-five eyes from 35 patients underwent photorefractive keratectomy for myopia. Photomicrographs of the endothelium were taken a short time before the operation and on an average of 7 months postoperatively with a specular microscope. The average endothelial cell densities were preoperatively 3375 {+-} 266 cells/mm{sup 2} (means {+-} SD) and postoperatively 3348 {+-} 287 cells/mm{sup 2}, corresponding to a fall of 27 cells/mm{sup 2} (N = 55). This fall in endothelial cell density was not statistically significant. A significant correlation between the change in cell density and age of the patient was found, with older patients losing more cells (N = 35, 2p < 0.05). The magnification of the specular microscope was found to change with corneal thickness. The importance of correcting the endothelial cell densities for corneal thickness is discussed. (au) 14 refs.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Excimer laser drilling of polymers

    Science.gov (United States)

    Chen, Yihong; Zheng, HongYu; Wong, Terence K. S.; Tam, Siu Chung

    1997-08-01

    Laser micro-drilling technology plays a more and more important role in industry, especially in the fabrication of multi-layer electronic packages. In such applications, non- metals are often used as insulators, in which via holes are formed to provide vertical interconnections for densely packed 3D wiring networks. Mechanical punch tools have been the primary means to form holes in ceramic sheets and in polymer boards since the 1970's. As the cost of fabricating punch heads increases drastically and the demand for quick turn around part build becomes more routine, flexible via forming technologies, such as laser drilling, have become more prevalent. In laser drilling, CO2, Nd:YAG, and excimer lasers are often used. Their drilling capabilities, drilling mechanisms, and hole qualities are different because of the different laser beam characteristics such as wavelength and beam energy distribution. In this paper, the mechanisms of laser drilling are briefly reviewed. The results of the experiments on excimer laser drilling of two types of polymer: polyimide and polyethylene terephthalate, are reported. It is found that the etch rate increases with increase of fluence, an the wall angle of drilled holes is dependent on the fluence. The material removal by a laser pulse is highly controllable. There exists an optimal fluence range to obtain clean and smooth edges of quality holes for a given material at a given laser wavelength.

  10. Excimer laser irradiation of metal surfaces

    Science.gov (United States)

    Kinsman, Grant

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

  11. Measurement of radiation and temperature of cathod spots in excimer laser discharge; Ekishima reza reiki hodennai ni fukumareru inkyoku kiten no kogakuteki kansoku to ondo no sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Minamitani, Y.; Nakatani, H. [Mitsubishi Electric Corp., Tokyo (Japan)

    1996-08-20

    Excimer laser is used in various fields such as luminous source for steppers, annealing treatment, ablation process, nuclear fusion and so on. In this paper, the radiation timing and gas temperature of cathode spots, streamer discharges and glow discharges in KrF excimer are measured by observing the radiating spectra thereof. The following conclusions are obtained from the results of the present study. Cathode spots begin to radiate at about 20ns after the discharge initiation, then the first and second radiation peaks are observed respectively when the discharge current reversing after passing zero point and the reserved discharged current approaching zero point. Streamer discharge makes flashover between electrodes at the second radiation peak of cathode spots, while the glow discharges almost disappear when streamer discharges occurring. The temperatures of cathode spots and glow discharge as 5500K and 2600K respectively are almost constant and independent upon the discharging voltage of laser. 14 refs., 12 figs.

  12. Corneal wound healing after excimer laser keratectomy.

    Science.gov (United States)

    Kaji, Yuichi; Yamashita, Hidetoshi; Oshika, Tetsuro

    2003-03-01

    Excimer laser keratectomy is widely used to correct refractive errors. Several complications of excimer laser keratectomy are reported including corneal infection, regression, corneal haze formation, glare and halo. Most of the complications are closely related to the corneal stromal wound healing process. In order to perform the excimer laser keratectomy with minimum complications, we should understand the mechanism of the corneal stroma wound healing process. In addition, such knowledge will help us to regulate the corneal stromal wound healing process in the future. In the present article, we discuss the molecular mechanism of the corneal stromal wound healing process after excimer laser keratectomy and its regulation by anti-inflammatory agents.

  13. Comparison of 3D surfaces produced by 248-nm and 193-nm excimer laser radiation

    Science.gov (United States)

    Toenshoff, Hans K.; Graumann, Christoph; Rinke, Marcus; Hesener, Hanno; Kulik, Christian

    1998-10-01

    Currently there is a strong demand for refractive optical elements made from glass in 21/2D and 3D-structures. Due to the characteristics of brittle materials like glass, only a limited number of manufacturing methods can be used to machine these materials with sub-micron resolution. Thus, current microstructures made out of glass are mainly manufactured by photolithography and etching process. Lithography techniques are only for economic purposes for a series production, but is not suitable for manufacturing prototypes or a small series. Micromachining done with Excimer Lasers in combination with high precision CNC- controlled handling systems offers flexible design possibilities for optical components. Due to the limitations of conventional machining techniques for brittle materials, a new laser machining system for material processing at a wavelength of 193 nm has been designed and built. The better absorption of 193 nm compared to 248 nm or larger wavelengths leads to damage free microstructuring of most glasses. Data generation for the volume to be ablated starts with the mathematical description of the surface shape of the optical component. The contour can be derived from a mathematical function or individual xyz-data point information from any CAD-program. A pre-processor calculates the CNC-data for laser triggering, xyz-table and the CNC- mask control. Each laser pulse leads to a material removal, defined by the illuminated surface on the workpiece as well as the energy density. Superposition or overlapping of pulses allows the creation of the desired surface. The surface roughness is determined by the wavelength as well as the chosen ablation strategy. To achieve best results, the process has to be carefully adjusted for a specific material. This technique is a sufficient method for structuring grooves in ceramics or glass as well as producing aspherical transparent optical surfaces or micro lens arrays. This paper shall describe the potential of 193 nm

  14. (308 nm) excimer laser

    Indian Academy of Sciences (India)

    The UV lasers with high quantum energy photons directly break the atomic and molecular bonds within material. The photons in this spectral range are also capable of inducing photo- chemical reactions. Most solid materials have high absorption in the UV. The short pulses result in reducing interaction time between laser ...

  15. Excimer laser etching of polyimide

    Science.gov (United States)

    Brannon, J. H.; Lankard, J. R.; Baise, A. I.; Burns, F.; Kaufman, J.

    1985-09-01

    It is reported that thin films of polyimide are efficiently etched in air at pulsed excimer laser wavelengths of 248, 308, and 351 nm. Etch rate versus incident fluence data are found to obey a Beer-Lambert etching relation. Sharp laser fluence thresholds for significant etching are found to correlate with the wavelength-dependent absorption coefficient. The absorbed energy density required to initiate significant etching is found, within experimental error, to be independent of the wavelengths examined. It is felt that this information demonstrates the predominantly thermal nature of the laser etching mechanism. Additionally, infrared spectroscopy and coupled gas chromatography/mass spectroscopy were used to identify several gases evolved during pulsed laser etching of polyimide in both air and vacuum.

  16. Applications of the Excimer Laser: A Review.

    Science.gov (United States)

    Beggs, Sarah; Short, Jack; Rengifo-Pardo, Monica; Ehrlich, Alison

    2015-11-01

    The 308-nm excimer laser has been approved by the Food and Drug Administration for the treatment of psoriasis and vitiligo. Its ability to treat localized areas has led to many studies determining its potential in the treatment of focal diseases with inflammation or hypopigmentation. To review the different applications of the 308-nm excimer laser for treating dermatologic conditions. An extensive literature review was conducted by searching PubMed, MEDLINE, and ClinicalKey to find articles pertaining to dermatologic conditions treated with the 308-nm excimer laser. Articles published that contributed to new applications of the excimer laser were included, as well as initial studies utilizing the excimer laser. The outcomes and results were compiled for different dermatologic conditions treated with the excimer laser. The 308-nm excimer laser has a wide range of uses for focal inflammatory and hypopigmented conditions. Treatment is generally well tolerated, with few adverse reactions. Larger studies and studies evaluating the long-term effects of the 308-nm excimer laser are needed.

  17. Pigmentation above the constitutive level: an indicator of excimer laser radiation-induced erythema in Koreans.

    Science.gov (United States)

    Choi, Jee-Woong; Na, Se-Young; Chung, Mi-Young; Na, Jung-Im; Huh, Chang-Hun; Youn, Sang-Woong; Kang, Hee-Young; Park, Kyoung-Chan

    2012-07-01

    Ultraviolet (UV) irradiation induces skin erythema, but it is not clear which factors have the greatest effects on UV sensitivity. Six healthy Korean adult men were enrolled and their melanin index (MI) and increment of erythema index (ΔEI) were measured. In each individual, 12 different sites were selected and 36 spots were irradiated with a single shot of monochromatic excimer laser with a dose of 350 mJ/cm(2) . The sites were categorized into three groups based on the cumulative sun exposure: UZ, unexposed zones; FEZ, frequently exposed zones; and IEZ, intermittently exposed zones. The sun exposure indexes (SEI) were also calculated based on previously described methods. ΔEI, MI and SEI were measured and calculated. The ΔEI of UZ was significantly higher than that of FEZ, but lower than that of IEZ. In general, there was a significant relationship between ΔEI and MI (R(2) = 0.135). However, IEZ did not show significant results. In contrast, there was a stronger relationship between ΔEI and SEI (R(2) = 0.344). Overall, the values were significantly higher for the SEI (0.541 [UZ], 0.281 [IEZ] and 0.228 [FEZ]) than for MI (0.311 [UZ], 0.011 [IEZ] and 0.073 [FEZ]). There were significant site variations in UV sensitivity along with skin pigmentation. In addition, significant differences were observed according to the exposure frequency. The SEI was found to be strongly correlated with UV sensitivity. These results suggest that the induced level of pigmentation above the constitutive level will be a better indicator for UV sensitivity than baseline MI. © 2012 Japanese Dermatological Association.

  18. Mitomicina C e "Excimer laser" Mitomycin C and Excimer Laser

    Directory of Open Access Journals (Sweden)

    Anelise Dutra Wallau

    2005-12-01

    Full Text Available A mitomicina C é um antimetabólito que atua em nível celular bloqueando a replicação de DNA e RNA e inibindo a síntese protéica. Utilizada em diversas áreas da oftalmologia, recentemente vem sendo empregada como moduladora da resposta cicatricial corneana em cirurgias ópticas/refrativas por "excimer laser". A aplicação única de mitomicina C associada à cirurgia fotoablativa de superfície corneana tem se mostrado opção segura e eficiente para fins terapêuticos em olhos com opacidade corneana pré-existente e/ou profiláticos em olhos com alto risco de desenvolvimento de opacificação corneana pós-operatória. O uso da droga em cirurgia fotoablativa deve ser cauteloso até que seguimento de longo prazo avalie sua inocuidade tardia. O presente texto faz revisão dos principais estudos sobre modulação da resposta cicatricial corneana com uso de mitomicina C em cirurgias ópticas/refrativas de superfície.Mitomycin C is an antimetabolite agent that blocks DNA and RNA replication and protein synthesis. It has been used in several ophthalmologic areas, and recently as a modulator of corneal wound healing in excimer laser surgeries. A single application of mitomycin C during surface corneal photoablative surgery seems a safe and efficient therapeutic option for eyes with corneal opacity and/or as prophylaxis in eyes with high risk for corneal opacity development. The use of this drug in photoablative surgery should be cautious until long-term safety results have been reported. The present text presents a review about corneal wound healing with the use of mitomycin C.

  19. Absorption of 308-nm excimer laser radiation by balanced salt solution, sodium hyaluronate, and human cadaver eyes

    Energy Technology Data Exchange (ETDEWEB)

    Keates, R.H.; Bloom, R.T.; Schneider, R.T.; Ren, Q.; Sohl, J.; Viscardi, J.J. (Univ. of California, Irvine (USA))

    1990-11-01

    Absorption of the excimer laser radiations of 193-nm argon fluorine and 308-nm xenon chloride in balanced salt solution, sodium hyaluronate, and human cadaver eyes was measured. The absorption of these materials as considerably different for the two wavelengths; we found that 308-nm light experienced much less absorption than the 193-nm light. The extinction coefficient (k) for 308 nm was k = 0.19/cm for balanced salt solution and k = 0.22/cm for sodium hyaluronate. In contrast to this, the extinction coefficient for 193 nm was k = 140/cm for balanced salt solution and k = 540/cm for sodium hyaluronate. Two 1-day-old human phakic cadaver eyes showed complete absorption with both wavelengths. Using aphakic eyes, incomplete absorption was noted at the posterior pole with 308 nm and complete absorption was noted with 193 nm. The extinction in the anterior part of aphakic eyes (the first 6 mm) was 4.2/cm for 308 nm, meaning that the intensity of the light is reduced by a factor of 10 after traveling the first 5.5 mm. However, we observed that the material in the eye fluoresces, meaning the 308 nm is transformed into other (longer) wavelengths that travel through the total eye with minimal absorption. Conclusions drawn from this experiment are that the use of the 308-nm wavelength may have undesirable side effects, while the use of the 193-nm wavelength should be consistent with ophthalmic use on both the cornea and the lens.

  20. Subpicosecond, high-brightness excimer laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A.J.; Gosnell, T.R.; Roberts, J.P.; Lester, C.S.; Gibson, R.B.; Harper, S.E.; Tallman, C.R.

    1988-01-01

    Subpicosecond, high-brightness excimer laser systems are being used to explore the interaction of intense coherent ultraviolet radiation with matter. Applications of current systems include generation of picosecond x-ray pulses, investigation of possible x-ray laser pumping schemes, studies of multiphoton phenomena in atomic species, and time-resolved photochemistry. These systems, based on the amplification of subpicosecond pulses in small aperture (/approximately/1 cm/sup 2/) XeCl or KrF amplifiers, deliver focal spot intensities of /approximately/10/sup 17/ W/cm/sup 2/. Scaling to higher intensities, however, will require an additional large aperture amplifier which preserves near-diffraction-limited beam quality and subpicosecond pulse duration. We describe here both a small aperture KrF system which routinely provides intensities >10/sup 17/ W/cm/sup 2/ to several experiments, and a large aperture XeCl system designed to deliver /approximately/1 J subpicosecond pulses and yield intensities on target in excess of 10/sup 19/W/cm/sup 2/. We also discuss the effects of two-photon absorption on large-aperture, high-brightness excimer lasers. 4 refs., 2 figs.

  1. 308-nm excimer laser in endodontics

    Science.gov (United States)

    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.

  2. The applicability of the Sedov - Taylor scaling during material removal of metals and oxide layers with pulsed ? and excimer laser radiation

    Science.gov (United States)

    Aden, M.; Kreutz, E. W.; Schlüter, H.; Wissenbach, K.

    1997-03-01

    For the removal of material with pulsed laser radiation the distance travelled by the shock or blast wave and the amount of energy released in the plasma state due to the absorption of laser radiation are determined experimentally and theoretically. The distance travelled by the blast wave is detected by schlieren photography, the released energy by monitoring the transmitted laser radiation during the removal process. The theoretical evaluation is performed by numerical simulation using a model incorporating the laser-induced vaporization process and the dynamics of the plasma state. The results obtained from the experiments and the model are compared with that of the Sedov - Taylor scaling. The removal of the oxide layer from austenitic steel is investigated with 0022-3727/30/6/011/img8 laser radiation produced by a TEA and a high-power 0022-3727/30/6/011/img8 laser device. For the TEA laser with fluences of 5 and 10 J 0022-3727/30/6/011/img10 50 - 80% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling describes the distance travelled by the blast wave in agreement with data from the experiments and the simulation. For the high-power 0022-3727/30/6/011/img8 laser with a fluence of 50 J 0022-3727/30/6/011/img10, 6% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling does not describe the data of the simulation. The process of removal of copper and aluminium material is simulated for excimer laser radiation with fluences of 15 and 30 J 0022-3727/30/6/011/img10. For copper 15 - 30% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling is applicable. For aluminium, less than 2% of the pulse energy is released into the plasma state and the Sedov - Taylor scaling is only applicable for the higher fluence.

  3. Corrosion resistance improvement of metals by excimer laser surface treatment

    Science.gov (United States)

    Autric, Michel L.; Perrais, Jacqueline; Barreau, Gerard

    2000-02-01

    KrF excimer laser has been used for physical and chemical transformations of metallic materials and coated metal samples. Aluminum alloys, steels and chromium coated mild steel have been treated under excimer laser radiation in order to improve their mechanical properties and their corrosion and oxidation resistance. The laser surface treatment leads, after surface remelting process, to important changes in the topography, the microstructure, the phases and the chemical composition of the near-surface region resulting in different hardness, wear properties and corrosion/oxidation behavior. We focus this paper on aluminum alloys (2000 and 6000 type) and steels irradiated using a krypton fluoride laser (20 ns, 0.5 - 10 J/cm2, up to 200 Hz) in laboratory air. The analysis were carried out by means of scanning electron microscopy, energy dispersive spectroscopy, coupled and low incidence angle X-ray diffraction, microhardness tester and electrochemical test equipments.

  4. Ignition by excimer laser photolysis of ozone

    Science.gov (United States)

    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 hydrocarbons as fuels was also demonstrated.

  5. Fabrication of an integrated optical Mach-Zehnder interferometer based on refractive index modification of polymethylmethacrylate by krypton fluoride excimer laser radiation

    Science.gov (United States)

    Koerdt, Michael; Vollertsen, Frank

    2011-04-01

    It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 μm to 1.62 μm. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.

  6. Fabrication of an integrated optical Mach-Zehnder interferometer based on refractive index modification of polymethylmethacrylate by krypton fluoride excimer laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Koerdt, Michael, E-mail: koerdt@bias.de [BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH, Klagenfurter Strasse 2, D-28359 Bremen (Germany); Vollertsen, Frank [BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH, Klagenfurter Strasse 2, D-28359 Bremen (Germany)

    2011-04-01

    It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 {mu}m to 1.62 {mu}m. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.

  7. Triggering Excimer Lasers by Photoionization from Corona Discharges

    Science.gov (United States)

    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.

  8. Investigation of excimer laser ablation of iron

    Science.gov (United States)

    Jordan, R.; Lunney, J. G.

    1998-05-01

    The excimer ablation of iron at 248 nm has been investigated by measuring the ablation depth and average ion energy as a function of laser fluence. Measurements have also been made of the laser transmission through the ablated vapour above the target. The absolute spectral intensity of the emission from the ablation plasma has been measured in both the vacuum ultraviolet and the visible. All results were compared with a simple numerical model describing the main physical processes involved in laser ablation of metal targets.

  9. Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

    Science.gov (United States)

    Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

    2008-04-01

    To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

  10. EFFECT OF OPTICAL FIBER HYDROGEN LOADING ON THE INSCRIPTION EFFICIENCY OF CHIRPED BRAGG GRATINGS BY MEANS OF KrF EXCIMER LASER RADIATION

    Directory of Open Access Journals (Sweden)

    Sergey V. Varzhel

    2016-11-01

    Full Text Available Subject of Research.We present comparative results of the chirped Bragg gratings inscription efficiency in optical fiber of domestic production with and without low-temperature hydrogen loading. Method. Chirped fiber Bragg gratings inscription was made by the Talbot interferometer with chirped phase mask having a chirp rate of 2.3 nm/cm used for the laser beam amplitude separation. The excimer laser system Coherent COMPexPro 150T, working with the gas mixture KrF (248 nm, was used as the radiation source. In order to increase the UV photosensitivity, the optical fiber was placed in a chamber with hydrogen under a pressure of 10 MPa and kept there for 14 days at 40 °C. Main Results. The usage of the chirped phase mask in a Talbot interferometer scheme has made it possible to get a full width at half-maximum of the fiber Bragg grating reflection spectrum of 3.5 nm with induced diffraction structure length of 5 mm. By preliminary hydrogen loading of optical fiber the broad reflection spectrum fiber Bragg gratings with a reflectivity close to 100% has been inscribed. Practical Relevance. The resulting chirped fiber Bragg gratings can be used as dispersion compensators in optical fiber communications, as well as the reflective elements of distributed fiber-optic phase interferometric sensors.

  11. Electrodeless excimer laser; Laser a eccimeri senza elettrodi

    Energy Technology Data Exchange (ETDEWEB)

    Lisi, N. [ENEA, Divisione Nuovi Materiali, Centro Ricerche Casaccia, Rome (Italy)

    2001-07-01

    In this paper it is proposed how to build an excimer laser based on an electrodeless discharge (or Dielectric Barrier Discharge). Such laser could operate with a low energy per pulse (<100 mJ) and a high repetition rate (<100 kHz). The most relevant advantage an electrodeless DBD laser is the much longer gas mixture lifetime. This feature could allow the operation of a sealed laser emitting higher average power with respect to commercially available excimer lasers. Such discharge scheme could be advantageous in order to excite the F{sub 2} excimer molecule, whose emission wavelength in the VUV range (157 nm) at high reprate is particularly interesting in the micro-lithography field. [Italian] In questo documento viene proposto come costruire un laser a eccimeri basato su una scarica priva di elettrodi, o Dielectric Barrier Discharge. Tale laser puo' funzionare con una bassa energia per impulso (<100 mJ) ad alta frequenza di ripetizione (<100 kHz). Il vantaggio fondamentale di un laser a DBD e quindi privo di elettrodi e' la vita media della miscela gassosa molto piu' alta che potrebbe permettere alla camera laser di operare sigillata ad una potenza media superiore a quella dei laser a eccimeri attuali. Tale schema di pompaggio potrebbe essere particolarmente vantaggioso per eccitare la molecola eccimero F{sub 2} la cui lunghezza di emissione nel VUV (157 nm) ad elevata frequenza di ripetizione presenta un notevole interesse nel campo della produzione di microcircuiti.

  12. Excimer laser phototherapeutic keratectomy for keratoconus nodules.

    Science.gov (United States)

    Elsahn, Ahmed F; Rapuano, Christopher J; Antunes, Victor A; Abdalla, Yasmine F; Cohen, Elisabeth J

    2009-02-01

    To report the outcomes of contact lens-intolerant patients with keratoconus (KCN) with subepithelial nodules treated with excimer laser phototherapeutic keratectomy (PTK). The charts of all contact lens-intolerant patients with KCN who underwent excimer laser PTK for subepithelial nodules were identified using a computer database and were retrospectively reviewed. Preoperative and postoperative visual acuity and method of correction, surgical treatment, epithelial healing, complications, and KCN nodule recurrence were all analyzed. Fifteen eyes of 15 patients with a minimum follow-up of 3 months were reviewed. Mean follow-up time was 23.1 months (SD +/- 42.5 months, range 3-143 months). In 9 eyes, the epithelial defect healed by postoperative day 3 and all eyes healed by postoperative day 6. There was no infection or corneal melting in any of the eyes. After PTK, 11 patients were refit successfully with rigid gas-permeable contact lenses and 4 wore glasses. Three patients had a recurrence of the KCN nodule at 3, 8, and 23 months postoperatively. One of them had a repeat PTK 23 months after the initial surgery, improving to 20/40 with contact lenses at 55 months postoperatively. Another patient decided to have a penetrating keratoplasty, and the third patient is considering repeat PTK or penetrating keratoplasty. PTK effectively removed KCN nodules without recurrences in most patients and can be a successful modality to improve contact lens tolerance and delay or avoid more invasive surgery.

  13. Excimer Lasers With Capacitively Excited Tubular Discharges

    Science.gov (United States)

    Eichler, Hans J.; Herweg, Helmut; de la Rosa, Jose

    1989-04-01

    The excitation of excimer lasers in tubular discharges results in simple and compact devices needing no preionization. Optical output energies are in the millijoule range. We investigated XeF, KrF and ArF lasers for various operating conditions. The lasers consist of capillary glass tubes with two internal electrodes at the ends and an aluminium-foil wrapped around the tube as capacitive electrode. A maximum output energy of 0.3 mJ has been achieved for the XeF laser. The good quality of the discharge is indicated by the observation of spontaneous mode locking. The detailed study of the discharge for different polarities of the electrodes has shown that efficient operation with a high gas lifetime can be obtained by a purely capacitively excited discharge. A gas lifetime of about 10,000 pulses for 3 litres gas mixture has been observed. Using a two stage Marx generator to generate 100 kV excitation voltage a maximum output energy of 0.7 mJ was obtained for a gas mixture of Kr, F2 and He with an efficiency of 0.17%. The KrF laser operates also without the buffer gas. Laser action in ArF has been achieved with 15 μJ pulse energy and 10 ns duration.

  14. Excimer laser cleaning of mud stained paper and parchment

    Directory of Open Access Journals (Sweden)

    Duarte, J. P.

    1998-04-01

    Full Text Available The main advantage of excimer lasers when processing materials, its the emission of a radiation with wavelength in the ultraviolet region. This characteristic allows an extremely accurate and very well defined shape of material removal as well as total absence of heat affected zone and alterations in the material structure. In excimer laser paper and parchment cleaning, the mud is removed by breaking the physicalchemical bonding between this last one and the material to be cleaned not affecting neither its structure nor the chromatic pigment existing in some samples.

    A principal vantagem dos lasers de excímeros, no processamento de materiais, é a emissão de um feixe luminoso com comprimento de onda compreendido na região do ultravioleta, permitindo urna remoçao do material com precisão muito elevada e excelente definição de bordos, ausência de zona térmicamente afectada e ausência de alterações da estrutura. Na limpeza dos papéis e pergaminhos a lama é removida por quebra das ligações fisico-químicas entre a lama e o papel não se afectando a estrutura deste, assim como não se afectaram os pigmentos cromáticos existentes em algumas amostras.

  15. Vitreoretinal surgery with the 193-nm excimer laser

    Science.gov (United States)

    Palanker, Daniel V.; Hemo, Itzhak; Turovets, Igor; Zauberman, Hanan; Lewis, Aaron

    1994-06-01

    The 193-nm excimer laser is known for its ability to precisely ablate soft biological tissues in the air environment with sub- micron depth control and sub-micron damage zones in the surrounding. The lack of a convenient delivery system and strong absorption of this radiation by biological liquids prevented, until recently, microsurgical applications of this laser. We have constructed special tips that are capable of delivering enough energy for effective removal of soft tissues in a strongly absorbing liquid environment. These tips attach to an articulated arm-based delivery system. This instrument was applied to vitreoretinal membranes removal. The accepted technique for these membranes removal is mechanical peeling and cutting which is associated with strong traction of the retina and this occasionally results in retinal damage. It was demonstrated in this study that the 193-nm excimer laser is capable of safely and precisely cutting and ablating these membranes which enable their removal without exerting any tractional forces on the retina. The effective cutting regime of retina and vitreoretinal membranes occurred at energy fluence of about 250- to 350-mJ/cm2/pulse with a corresponding cutting depth of 50 to 150 micrometers /pulse. The results obtained in this study suggest that this technology could be applicable to a wide variety of intraocular procedures.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  18. Preionization and gain studies in fluorine based excimer laser gas discharges

    NARCIS (Netherlands)

    Azarov, A.V.

    2008-01-01

    Fluorine-based excimer gas lasers are powerful sources of coherent radiation in the UV and VUV part of the electro-magnetic spectrum. Due to their short wavelengths and high output power they are widely employed in high resolution material processing like micromachining and in lithography. In this

  19. Comparative shock wave analysis during corneal ablation with an excimer laser, picosecond laser, and femtosecond laser

    Science.gov (United States)

    Krueger, Ronald R.; Juhasz, Tibor

    1995-05-01

    With the event of topographic steep central islands following excimer laser surgery and the potential damage to the corneal endothelium, shock waves are playing an increasingly important role in laser refractive surgery. With this in mind, we performed a comparative shock wave analysis in corneal tissue using an excimer laser, picosecond laser, and femtosecond laser. We used a Lambda Physik excimer laser at 308 nm wavelength, a Nd:YLF picosecond laser at 1053 nm wavelength and a synchronously pumped linear cavity femtosecond laser at 630 nm wavelength. The pulse widths of the corresponding lasers were 8 ns, 18 ps, 150 fs, respectively. The energy density of irradiation was 2.5 to 8 times the threshold level being 2 J/cm2 (excimer laser), 86 J/cm2 (picosecond laser) and 10.3 J/cm2 (femtosecond laser). Shock wave dynamics were analyzed using time-resolved photography on a nanosecond time scale using the picosecond laser in corneal tissue, water and air. Shock wave dynamics using the femtosecond laser were studied in water only while the excimer laser induced shock wave during corneal ablation was studied in air only. We found the dynamics of shock waves to be similar in water and corneal tissue indicating that water is a good model to investigate shock wave effects in the cornea. The magnitude of the shock wave velocity and pressure decays over time to that of a sound wave. The distance over which it decays is 3 mm in air with the excimer laser and 600 - 700 micrometers in air with the picosecond laser. In water, the picosecond laser shock wave decays over a distance of 150 micrometers compared to the femtosecond laser shock wave which decays over a distance of 30 micrometers . Overall the excimer laser shock wave propagates 5 times further than that of the picosecond laser and the picosecond laser shock wave propagates 5 times further than that of the femtosecond laser. In this preliminary comparison, the time and distance for shock wave decay appears to be directly

  20. Overview on the high power excimer laser technology

    Science.gov (United States)

    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.

  1. New Class of Excimer-Pumped Atomic Lasers (XPALS)

    Science.gov (United States)

    2017-01-27

    AFRL-AFOSR-VA-TR-2017-0019 New Class of Excimer-Pumped Atomic Lasers (XPALS) James Eden UNIVERSITY OF ILLINOIS CHAMPAIGN 506 S WRIGHT ST 364 HENRY...TITLE AND SUBTITLE New Class of Excimer-Pumped Atomic Lasers (XPALS) 5a. CONIKA\\.INUMBER FA9550-13- 1-0006 5b.GRANT NUMBER Sc. f’ftOGRAM ELEMENT...cxcitcd state-excited state reaction rates. We ore pleased to report that the main goal orthis program, the viability of nn atomic laser having a

  2. Excimer laser interaction with dentin of the human tooth

    Science.gov (United States)

    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.

  3. Preionization and gain studies in fluorine based excimer laser gas discharges

    OpenAIRE

    Azarov, A.V.

    2008-01-01

    Fluorine-based excimer gas lasers are powerful sources of coherent radiation in the UV and VUV part of the electro-magnetic spectrum. Due to their short wavelengths and high output power they are widely employed in high resolution material processing like micromachining and in lithography. In this field pattern sizes several times shorter than the used wavelength can be achieved using an immersion technique. However due to the short duration of the laser pulse (typically of few tens of ns for...

  4. Topographic steep central islands following excimer laser photorefractive keratectomy

    Science.gov (United States)

    Krueger, Ronald R.; McDonnell, Peter J.

    1994-06-01

    The purpose of this study is to demonstrate that topographic irregularities in the form of central islands of higher refractive power can be seen following excimer laser refractive surgery. We reviewed the computerized corneal topographic maps of 35 patients undergoing excimer laser PRK for compound myopic astigmatism or anisometropia from 8/91 to 8/93 at the USC/Doheny Eye Institute. The topographic maps were generated by the Computed Anatomy Corneal Modeling System, and central islands were defined as topographic areas of steepening of at least 3 diopters and 3 mm in diameter. A grading system was developed based on the presence of central islands during the postoperative period. Visually significant topographic steep central islands may be seen in over 50% of patients at 1 month following excimer laser PRK, and persist at 3 months in up to 24% of patients without nitrogen gas blowing. Loss of best corrected visual acuity or ghosting is associated with island formation, and may prolong visual rehabilitation after excimer laser PRK.

  5. HSP47 expression in cornea after excimer laser photoablation.

    Science.gov (United States)

    Kasagi, Yasuo; Yamashita, Hidetoshi

    2002-01-01

    The expression of heat shock protein 47 (HSP47) was observed histologically to investigate the spatial and chronological effects of excimer laser photoablation. HSP47 expression after radial keratotomy (RK) was also investigated and compared with the effects after excimer laser photoablation. Twenty-eight male rabbits were used. The rabbits were divided with two groups and treated with either excimer laser photoablation or four radial incisions to simulate corneal refractive surgery. The chronological and spatial changes in the expression of HSP47 were observed immunohistochemically. In eyes that underwent excimer laser photoablation, HSP47 was detected in the basal layer of the epithelial cells and in the superficial stromal layer 3 days after surgery. After 5 and 7 days, HSP47 expression extended to the deep layer of the stroma and to the endothelial cells. After 14 days, HSP47 was detected only in the deep layer of the stroma and in the endothelial cells. After 28 days, HSP47 expression was reduced. In eyes that underwent RK, HSP47 was detected in the basal layer of the epithelial cells and in the stroma surrounding the wound 1 day after surgery. After 3 and 7 days, HSP47 expression did not expand further. After 28 days, HSP47 expression diminished. Excimer laser photoablation affects the whole layer of the cornea, and may be caused by the shock wave that occurs as a result of photoablation. In addition, interaction among the keratocytes may propagate the stress-induced response to the whole layer of the cornea. With RK, the wound is smaller and deeper. HSP47 expression occurs earlier, but is limited to the area surrounding the wound.

  6. Excimer laser assisted chemical machining of SiC ceramic

    Science.gov (United States)

    Hibi, Yuko; Enomoto, Yuji; Kikuchi, Kaoru; Shikata, Nobuo; Ogiso, Hisato

    1995-02-01

    A highly effective method of machining ceramic has been newly developed using a krypton fluoride (KrF) excimer laser with a 248 nm wavelength. The laser was irradiated on SiC in water to form a soft hydrous oxide layer by photochemical reaction. The softened layer was then cut with a diamond tool to form a mirror surface finish. The optimum conditions were found for both high machining rate and better surface integrity of SiC.

  7. Impacts of excimer laser annealing on Ge epilayer on Si

    Science.gov (United States)

    Huang, Zhiwei; Mao, Yichen; Yi, Xiaohui; Lin, Guangyang; Li, Cheng; Chen, Songyan; Huang, Wei; Wang, Jianyuan

    2017-02-01

    The impacts of excimer laser annealing on the crystallinity of Ge epilayers on Si substrate grown by low- and high-temperature two-step approach in an ultra-high vacuum chemical vapor deposition system were investigated. The samples were treated by excimer laser annealing (ELA) at various laser power densities with the temperature above the melting point of Ge, while below that of Si, resulting in effective reduction of point defects and dislocations in the Ge layer with smooth surface. The full-width at half-maximum (FWHM) of X-ray diffraction patterns of the low-temperature Ge epilayer decreases with the increase in laser power density, indicating the crystalline improvement and negligible effect of Ge-Si intermixing during ELA processes. The short laser pulse time and large cooling rate cause quick melting and recrystallization of Ge epilayer on Si in the non-thermal equilibrium process, rendering tensile strain in Ge epilayer as calculated quantitatively with thermal mismatch between Si and Ge. The FWHM of X-ray diffraction patterns is significantly reduced for the two-step grown samples after treated by a combination of ELA and conventional furnace thermal annealing, indicating that the crystalline of Ge epilayer is improved more effectively with pre- annealing by excimer laser.

  8. Lead extraction experience with high frequency excimer laser.

    Science.gov (United States)

    Tanawuttiwat, Tanyanan; Gallego, Daniel; Carrillo, Roger G

    2014-09-01

    A higher frequency Excimer laser sheath using an 80-Hz pulse repetitive rate was approved by the Food and Drug Administration in April 2012. We reported our initial clinical experience with a high-frequency Excimer laser sheath and compared it with lower-frequency laser sheaths which have been previously used. In this single center, retrospective cohort study, we evaluated patients who underwent lead extraction from December 2008 to May 2013. Those who underwent lead removal without using a laser sheath or with approaches other than subclavian were excluded. Primary endpoints included total laser time, number of pulses, and complications. Data on clinical characteristics, lead type, indications, and outcomes were prospectively collected and analyzed. A total of 427 patients were included in the study (72.6% male; age 67.9 ± 15.23 years). Lower frequency and higher frequency laser sheaths were used in 315 and 112 patients, respectively. A total of 821 leads were removed with 765 leads (93.2%) extracted using the Excimer laser sheath. Lead age was 5.71 ± 4.96 years. Complete extraction was seen in all patients. A higher-frequency laser sheath was associated with a lower laser time and a lower total number of laser pulses even after adjustments for the number of leads, type of leads, and lead age. In the higher frequency group, mortality rate was 0.9% and minor complication rate was 3.6%. When compared with the lower-frequency laser sheath, the higher-frequency laser sheath requires less laser times and more efficient amount of pulses for lead extraction with comparable success rate. Due to the rarity of major and minor complications, no statistical significance was found between the two groups. ©2014 Wiley Periodicals, Inc.

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

    Science.gov (United States)

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

    2001-04-01

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

  10. Subjective results of excimer laser correction of myopia. Review

    Directory of Open Access Journals (Sweden)

    V. N. Trubilin

    2012-01-01

    Full Text Available In review presents data of various authors regarding the subjective results excimer laser correction of myopia by LASIK. It was revealed that a group of patients with a high degree of dissatisfaction amounts to 4.6% of the total in all studies. High subjective results are confirmed by the positive dynamics of the «quality of life» of the patient.

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

    Science.gov (United States)

    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.

  12. Penetrating Keratoplasty for Keratoconus – Excimer Versus Femtosecond Laser Trephination

    Science.gov (United States)

    Seitz, Berthold; Langenbucher, Achim; Hager, Tobias; Janunts, Edgar; El-Husseiny, Moatasem; Szentmáry, Nora

    2017-01-01

    Background: In case of keratoconus, rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis. Methods: In case of advanced keratoconus – especially after corneal hydrops due to rupture of Descemet’s membrane – penetrating keratoplasty (PKP) still is the surgical method of first choice. Noncontact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in case of “keratoconus recurrences” due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually depending on corneal size („as large as possible – as small as necessary“). Limbal centration will be preferred intraoperatively due to optical displacement of the pupil. During the last 10 years femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach. Results: Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces “vertical tilt” and “horizontal torsion” of the graft in the recipient bed, thus resulting in significantly less “all-sutures-out” keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. Refractive outcomes of femtosecond laser

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

    Energy Technology Data Exchange (ETDEWEB)

    Radu, L. [Department of Molecular Genetics and Radiobiology, Babes National Institute, Bucharest (Romania)], E-mail: lilianajradu@yahoo.fr; Mihailescu, I. [Department of Lasers, Laser, Plasma and Radiation Physics Institute, Bucharest (Romania); Radu, S. [Department of Computer Science, Polytechnics University, Bucharest (Romania); Gazdaru, D. [Department of Biophysics, Bucharest University (Romania)

    2007-09-21

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

  14. Effect of open ultraviolet germicidal irradiation lamps on functionality of excimer lasers used in cornea surgery.

    Science.gov (United States)

    Belovickis, Jaroslavas; Kurylenka, Aliaksei; Murashko, Vadim

    2017-01-01

    We report on the impact of direct ultraviolet germicidal irradiation (UVGI) on reflective optics, used in the excimer laser system Allegretto Eye-Q. The aim of our work was to confirm our hypothesis based on long-rate observations of obtained anomalies in post-operative results that are attributed to degradation of reflective optics upon ultraviolet radiation. The presence of direct UVGI coupled with humidity in the operating environment caused merging anomalies and unwanted post-operative correction values. Ultraviolet-A radiation caused a similar effect on the reflective cover of the mirrors.

  15. Recent developments on microablation of glass materials using excimer lasers

    Science.gov (United States)

    Tseng, Ampere A.; Chen, Ying-Tung; Chao, Choung-Lii; Ma, Kung-Jeng; Chen, T. P.

    2007-10-01

    For many years, the development of effective laser machining techniques for making glass-based microcomponents and devices has been a critical factor in the birth of new photonic and biomedical microsystems. In this article, the characteristics and abilities of excimer lasers for micromachining of a wide range of glass materials are reviewed and studied. Following the introduction, the special features of excimer lasers are discussed. The typical micromachining system used for glass materials is presented. Then, the fundamental micromachining parameters and the associated morphologies of machined surfaces are evaluated. The approaches by controlling the ablation rate for making the curve surfaces are specifically formulated. Although a wide range of commercially available glasses is covered in this article, two types of the most widely used glasses, borosilicate glass and fused silica, are thoroughly examined to illustrate the complexity in micromachining the glass materials. The procedures to machine single, arrayed, curved microstructures are described. The utilizations of these procedures for making microneedles, optical waveguides, submicron grating, and microlenses are specifically demonstrated. Finally, recommendations for future efforts are presented.

  16. Laser drilling of metals with a XeCl excimer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.

    2005-01-01

    This thesis is about laser drilling with a unique excimer laser with a nearly diffraction-limited beam and relatively long optical pulse duration of 175 ns. The combination of high processing speed and high processing quality suitable for industrial applications can be obtained because the excellent

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

    Science.gov (United States)

    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.

  18. EXCIMER-LASER ABLATION OF SOFT-TISSUE - A STUDY OF THE CONTENT OF RAPIDLY EXPANDING AND COLLAPSING BUBBLES

    NARCIS (Netherlands)

    van Leeuwen, T. G.; Jansen, E. D.; Motamedi, M.; Welch, A. J.; Borst, C.

    1994-01-01

    Both holmium (lambda = 2.09 mum) and excimer (lambda = 308 nm) lasers are used for ablation of tissue. In a previous study, excimer laser ablation of aorta produced rapidly expanding and collapsing vapor bubbles. To investigate whether the excimer-induced bubble is caused by vaporization of (tissue)

  19. Low threshold buried-heterostructure quantum well lasers by excimer laser assisted disordering

    Energy Technology Data Exchange (ETDEWEB)

    Epler, J.E.; Thornton, R.L.; Mosby, W.J.; Paoli, T.L.

    1988-10-17

    Laser assisted disordering based upon a direct-write Ar/sup +/ laser beam has been established as a fabrication technique for high quality optoelectronic devices. In this letter, we report a new form of laser assisted disordering in which an excimer laser beam, photolithographically patterned, is used to define the incorporation of Si impurity into GaAs-AlGaAs heterostructure crystals. During a subsequent thermal anneal the diffusing Si induces layer disordering to a depth of approx.1 ..mu..m. The excimer laser assisted disordering process is characterized as a function of the energy density of the laser beam. Also, this technique is used to fabricate high quality buried-heterostructure lasers. With a reflective rear facet, the typical cw threshold current is 4 mA and the maximum power output is 27 mW. The devices exhibit single fundamental mode operation with subsidiary longitudinal side modes suppressed by 34 dB.

  20. Combination treatment with excimer laser and narrowband UVB light in vitiligo patients.

    Science.gov (United States)

    Shin, Sungsik; Hann, Seung-Kyung; Oh, Sang Ho

    2016-01-01

    For the treatment of vitiligo, narrowband UVB (NBUVB) light is considered the most effective for nonsegmental vitiligo, while excimer laser treatment is commonly used for localized vitiligo. However, treatment areas may potentially be missed with excimer laser treatment. We aimed to evaluate the effect of combinational treatment with NBUVB light and excimer laser on vitiligo. All patients were first treated with NBUVB; excimer laser was then applied in conjunction with NBUVB phototherapy due to a slow response or no further improvement with continuous NBUVB treatment alone. To minimize adverse effects, a fixed dose of NBUVB was administered, and the dose of excimer laser was increased based on patient response. Among 80 patients, 54 patients showed responses after combination with excimer laser; however, 26 patients (32.5%) showed no remarkable change after combination therapy. Of the 26 patients who showed no further response, 12 patients (46.1%) presented with vitiligo on the acral areas, which are known to the least responsive sites. Our study suggests that combined treatment of NBUVB and excimer laser in vitiligo may enhance the treatment response without remarkable side effects, therefore might also increase the compliance of the patients to the treatment. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. Excimer laser ablation of polyimide: a 14-year IBM perspective

    Science.gov (United States)

    Brannon, James H.; Wassick, Thomas A.

    1997-05-01

    IBM introduced the first commercial high-end mainframe computer system incorporating laser ablation technology in 1991. This milestone was the culmination of nearly a decade of scientific, engineering, and manufacturing effort. Extensive research and development on 308 nm laser ablation of polyimide lead to the first IBM prototype ablation tool in 1987 for the production of via-holes in thin film packaging structures. This prototype, similar to step and repeat photolithography systems, evolved into full-scale manufacturing tools which utilize sophisticated beam shaping, beam homogenizing, and projection optics. But the maturity of this technology belies the fact that the scientific understanding of the laser ablation process is still far from complete. This paper briefly reviews the engineering and scientific accomplishments, both within and external to IBM, that lead to the commercial utilization of the laser ablation process. Current technical tissues are discussed, in addition to alternative IBM applications of polyimide ablation. The paper concludes by discussing the relative merits of excimer vs. solid-state lasers, and how each may impact future manufacturing technology.

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

    Science.gov (United States)

    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.

  3. Wettability characteristics of carbon steel modified with CO2, Nd:YAG, Excimer and high power diode lasers

    OpenAIRE

    Lawrence, Jonathan; Li, Lin

    2000-01-01

    Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of a common mild steel (EN8) was found to effect changes in the wettability characteristics of the steel, namely changes in the measured contact angle. These modifications are related to changes in the surface roughness, changes in the surface oxygen content and changes in the surface energy of the mild steel. The wettability characteristics of the selected mild steel could be controll...

  4. Study on the excimer laser annealed amorphous hydrogenated silicon carbon films deposited by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosone, G. [CNR-INFM CRS-Coherentia, Complesso Universitario MSA, Napoli (Italy); Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario MSA, Napoli (Italy); Basa, D.K. [Utkal University, Bhubaneswar (India); Coscia, U. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario MSA, Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, Napoli (Italy); Tresso, E.; Celasco, E. [Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino (Italy); Chiodoni, A. [Materials and Microsystems Laboratory, chi-LAB, Politecnico di Torino (Italy); Pinto, N.; Murri, R. [Dipartimento di Fisica, Universita' di Camerino (Italy)

    2010-04-15

    Hydrogenated amorphous silicon carbon films of different carbon content were deposited by plasma enhanced chemical vapour deposition at low substrate temperature (200 C) and were subjected to excimer laser annealing. X-ray diffraction spectra and field emission scanning electron microscopy images demonstrate that carbon content plays an important role in facilitating the crystallization process induced by the excimer laser treatment (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Shadowgraphic imaging of metal drilling with a long pulse excimer laser

    NARCIS (Netherlands)

    Schoonderbeek, A.; Biesheuvel, C.A.; Hofstra, R.M.; Boller, Klaus J.; Meijer, J.; Miyamoto, Isamu; Ostendorf, Andreas; Sugioka, Koji; Helvajian, Henry

    2003-01-01

    A shadowgraphic imaging technique is used for studying the interaction between the laser beam and the material during laser drilling. The used laser is a XeCl excimer laser with a nearly diffraction limited beam and 175 ns pulse length. We studied how and when the material is removed. Holes are

  6. Advanced excimer laser technologies enable green semiconductor manufacturing

    Science.gov (United States)

    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.

  7. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  8. LASIK ablation centration: an objective digitized assessment and comparison between two generations of an excimer laser.

    Science.gov (United States)

    Kanellopoulos, Anastasios John; Asimellis, George

    2015-03-01

    To objectively define the effective centration of myopic femtosecond laser-assisted LASIK ablation pattern, evaluate the difference between achieved versus planned excimer laser ablation centration, and compare these results from two different generations of an excimer laser system. The study retrospectively evaluated 280 eyes subjected to myopic LASIK. Digital image analysis was performed on Scheimpflug sagittal curvature maps (difference of preoperative to postoperative). Centration was assessed via proprietary software digital analysis of the coordinate displacement between the achieved ablation geometric center and the planned ablation center, which was the corneal vertex. Results from two different excimer laser generations (Eye-Q 400 [140 eyes] and EX500 [140 eyes]; Alcon/WaveLight, Fort Worth, TX) were compared. Radial displacement was on average 360 ± 220 µm (range: 0 to 1,030 µm) in the Eye-Q 400 laser group and 120 ± 110 µm (range: 0 to 580 µm) in the EX500 laser group (P laser group and 4% in the EX500 laser group. Displacement of ablation pattern may depend on the laser platform used. The improvement in the efficiency of centration indicates that newer generation excimer lasers with faster eye tracking and active centration control appear to achieve a significantly more accurate centration of myopic ablation patterns. The authors propose this novel, objective technique for laser refractive surgeon evaluation may point out significant outcome measures not currently used in standard metrics of refractive laser efficiency. Copyright 2015, SLACK Incorporated.

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

    Science.gov (United States)

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

    2012-03-01

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

  10. Time Evolution of the Excimer State of a Conjugated Polymer Laser

    Directory of Open Access Journals (Sweden)

    Wafa Musa Mujamammi

    2017-11-01

    Full Text Available An excited dimer is an important complex formed in nano- or pico-second time scales in many photophysics and photochemistry applications. The spectral and temporal profile of the excimer state of a laser from a new conjugated polymer, namely, poly (9,9-dioctylfluorenyl-2,7-diyl (PFO, under several concentrations in benzene were investigated. These solutions were optically pumped by intense pulsed third-harmonic Nd:YAG laser (355-nm to obtain the amplified spontaneous emission (ASE spectra of a monomer and an excimer with bandwidths of 6 and 7 nm, respectively. The monomer and excimer ASEs were dependent on the PFO concentration, pump power, and temperature. Employing a sophisticated picosecond spectrometer, the time evolution of the excimer state of this polymer, which is over 400 ps, can be monitored.

  11. Epithelial healing and clinical outcomes in excimer laser photorefractive surgery following three epithelial removal techniques: mechanical, alcohol, and excimer laser.

    Science.gov (United States)

    Lee, Hyung Keun; Lee, Kyung Sub; Kim, Jin Kook; Kim, Hyeon Chang; Seo, Kyung Ryul; Kim, Eung Kweon

    2005-01-01

    To evaluate epithelial healing, postoperative pain, and visual and refractive outcomes after photorefractive keratectomy (PRK) using three epithelial removal techniques. Prospective, nonrandomized, comparative trial. Department of Ophthalmology, Yonsei University College of Medicine and Balgensesang Ophthalmology Clinic, Seoul, Korea. For the PRK procedure, the corneal epithelium was removed in one of three ways: mechanically (conventional PRK [PRK]) in 88 eyes of 44 patients; using excimer laser (transepithelial PRK [tPRK]) in 106 eyes of 53 patients; or using 20% diluted alcohol, laser-assisted subepithelial keratomileusis (LASEK) in 106 eyes of 53 patients. Epithelial healing, postoperative pain, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and remaining refractive error. The mean postoperative pain scores were 4.84 +/- 1.45 for PRK, 4.71 +/- 1.62 for tPRK, and 4.63 +/- 1.52 for LASEK (P = .125). The mean epithelial healing rates were 12.3 +/- 4.6 for PRK, 15.2 +/- 4.9 for tPRK, and 18.1 +/- 5.2 mm2/day for LASEK (P refractive outcomes. Using the same nomogram, tPRK resulted in a slight overcorrection, and LASEK resulted in a slight undercorrection.

  12. All-Solid-State Drivers for High Power Excimer Lasers Used in Projection Gas Immersion Laser Doping

    National Research Council Canada - National Science Library

    Jacob, Jonah

    2001-01-01

    .... P-GILD uses a pulsed, 200-watt-class excimer laser as an illumination source to produce ultra-shallow, low-sheet resistance, box-like and retrograde impurity profiles in silicon without the use...

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

    Energy Technology Data Exchange (ETDEWEB)

    See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

    2016-02-28

    Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: 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 (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), 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{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −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 C=C bond completely through the chain scission process whereas

  14. Evaluation of the efficacy of excimer laser ablation of cross-linked porcine cornea.

    Directory of Open Access Journals (Sweden)

    Shihao Chen

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  16. High efficiency metal marking with CO2 laser and glass marking with excimer laser

    DEFF Research Database (Denmark)

    Bastue, Jens; Olsen, Flemmming Ove

    1997-01-01

    with a thoroughly tested ray-tracing model is presented and compared with experimental results. Special emphasis is put on two different applications namely marking in metal with TEA-CO2 laser and marking in glass with excimer laser. The results are evaluated on the basis of the achievable energy enhancement......Today, mask based laser materials processing and especially marking is widely used. However, the energy efficiency in such processes is very low [1].This paper gives a review of the results, that may be obtained using the energy enhancing technique [1]. Results of simulations performed...

  17. Terraced copper growth deposited onto Teflon AF1600 by the excimer laser irradiation of Cu(hfac)TMVS

    Energy Technology Data Exchange (ETDEWEB)

    Popovici, D.; Piyakis, K.; Sacher, E.; Meunier, M. [Ecole Polytechnique, Montreal, Quebec (Canada)

    1996-12-31

    The authors are studying the feasibility of constructing Cu/fluoropolymer multilayer devices, in an effort to reduce both metal R and insulator C, a necessary condition in VLSI and GSI microelectronic applications. The laser chemical vapor deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.

  18. Performance characteristics of an excimer laser (XeCl) with single ...

    Indian Academy of Sciences (India)

    Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation.

  19. Performance characteristics of an excimer laser (XeCl) with single ...

    Indian Academy of Sciences (India)

    2017-01-10

    Jan 10, 2017 ... Abstract. Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compres- sion suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for ...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Excimer laser-induced metallization for in situ processing on Si and GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Meunier, Michel; Suys, Marc; Tabbal, Maleck; Izquierdo, Ricardo; Yelon, Arthur; Sacher, Edward (Groupe des Couches Minces and Dept. de Genie Physique, Ecole Polytechnique de Montreal, Station ' A' , Montreal, Quebec (Canada))

    1994-05-15

    We have investigated both the large area excimer laser-induced deposition of W and its silicides on GaAs to form thermally stable Schottky contacts, and the reduction of a Cu(I) compound for the deposition of Cu interconnects for Si microelectronics. Using a KrF excimer laser at 25 mJ/cm[sup 2] and a mixture of WF[sub 6], SiH[sub 4] and Ar, metallic W is deposited with an average growth rate of 1 A/pulse. For Cu deposition, the reduction by H[sub 2] of the precursor Cu(hfac)(TMVS) under a KrF excimer laser illumination of 9 mJ/cm[sup 2] gives metallic Cu with a Cu/C ratio of 4.35. For both processes, possible deposition mechanisms are discussed in terms of gas phase and surface reactions

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

    Science.gov (United States)

    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.

  3. Wettability characteristics of a modified mild steel with CO2, Nd:YAG, excimer and high power diode lasers

    OpenAIRE

    Lawrence, Jonathan; Li, Lin

    1999-01-01

    Interaction of CO2, Nd:YAG, excimer and high-power diode laser radiation with the surface of a common mild steel (EN8) was found to effect changes in the wettability characteristics of the steel, namely changes in the measured contact angle of certain liquids. Such changes were identified as being due to modifications to (i) the surface roughness, (ii) changes in the surface oxygen content and (iii) changes in the surface energy of the mild steel. However, it was found that changes in the wet...

  4. Surface modification of an Al2O3/SiO2 based ceramic treated with CO2, Nd:YAG, excimer and high power diode lasers for altered wettability characteristics

    OpenAIRE

    Lawrence, Jonathan; Li, Lin; Spencer, Julian T.

    1998-01-01

    Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to affect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identifi...

  5. Discharge instabilities in high-pressure fluorine based excimer laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.

    2007-01-01

    Fluorine based excimer lasers such as KrF, ArF and F2 are currently the most powerful sources available in the ultraviolet wavelength range, operating at 248 nm, at 193 nm and at 157 nm, respectively. They are thus of central importance for numerous applications in this range. At these short

  6. A new method for three dimensional excimer laser micromachining, Hole Area Modulation (HAM)

    NARCIS (Netherlands)

    Masuzawa, T.; Olde Benneker, Jeroen; Eindhoven, J.J.C.

    2000-01-01

    A new excimer laser system configuration for three dimensional (3D) micromachining, called Hole Area Modulation (HAM) method, is proposed and the feasibility of the system is experimentally confirmed. In this method, information on the depth of machining is converted to the sizes of small holes in

  7. Saline flush during excimer laser angioplasty: short and long term effects in the rabbit femoral artery

    NARCIS (Netherlands)

    van Leeuwen, T. G.; Velema, E.; Pasterkamp, G.; Post, M. J.; Borst, C.

    1998-01-01

    BACKGROUND AND OBJECTIVE: In this study, the effect of flushing saline on arterial wall damage (medial ruptures and necrosis), intimal hyperplasia, and arterial remodeling was determined. During excimer laser coronary angioplasty saline is flushed to reduce the size of explosive water vapor bubbles

  8. Refractive microlenses produced by excimer laser machining of poly(methyl methacrylate)

    DEFF Research Database (Denmark)

    Jensen, Martin Frøhling; Krühne, Ulrich; H., L.

    2005-01-01

    A method has been developed whereby refractive microlenses can be produced in poly (methyl methacrylate) by excimer laser irradiation at λ = 248 nm. The lenses are formed by a combined photochemical and thermal process. The lenses are formed as depressions in the substrate material (negative foca...

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

    Science.gov (United States)

    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

  10. Excimer laser doping technique for application in an integrated CdTe imaging device

    CERN Document Server

    Mochizuki, D; Aoki, T; Tomita, Y; Nihashi, T; Hatanaka, Y

    1999-01-01

    CdTe is an attractive semiconductor material for applications in solid-state high-energy X-ray and gamma-ray imaging systems because of its high absorption coefficient, large band gap, good mobility lifetime product of holes and stability at normal atmospheric conditions. We propose a new concept for fabricating an integrated CdTe with monolithic circuit configuration for two-dimensional imaging systems suitable for medical, research or industrial applications and operation at room temperature. A new doping technique has been recently developed that employs excimer laser radiation to diffuse impurity atoms into the semiconductor. Accordingly, heavily doped n- and p-type layers with resistivities less than 1 OMEGA cm can be formed on the high resistive CdTe crystals. We have further extended this technique for doping with spatial pattern. We will present the laser doping technique and various results thus obtained. Spatially patterned doping is demonstrated and we propose the use of these doping techniques for...

  11. A design of energy detector for ArF excimer lasers

    Science.gov (United States)

    Feng, Zebin; Han, Xiaoquan; Zhou, Yi; Bai, Lujun

    2017-08-01

    ArF excimer lasers with short wavelength and high photon energy are widely applied in the field of integrated circuit lithography, material processing, laser medicine, and so on. Excimer laser single pulse energy is a very important parameter in the application. In order to detect the single pulse energy on-line, one energy detector based on photodiode was designed. The signal processing circuit connected to the photodiode was designed so that the signal obtained by the photodiode was amplified and the pulse width was broadened. The amplified signal was acquired by a data acquisition card and stored in the computer for subsequent data processing. The peak of the pulse signal is used to characterize the single pulse energy of ArF excimer laser. In every condition of deferent pulse energy value levels, a series of data about laser pulses energy were acquired synchronously using the Ophir energy meter and the energy detector. A data set about the relationship between laser pulse energy and the peak of the pulse signal was acquired. Then, by using the data acquired, a model characterizing the functional relationship between the energy value and the peak value of the pulse was trained based on an algorithm of machine learning, Support Vector Regression (SVR). By using the model, the energy value can be obtained directly from the energy detector designed in this project. The result shows that the relative error between the energy obtained by the energy detector and by the Ophir energy meter is less than 2%.

  12. Comparison of femtosecond and excimer laser platforms available for corneal refractive surgery.

    Science.gov (United States)

    Chen, Lisa Y; Manche, Edward E

    2016-07-01

    The evolution of laser technology has left today's refractive surgeon with a choice between multiple laser platforms. The purpose of this review is to compare currently available femtosecond and excimer laser platforms, providing a summary of current evidence. Femtosecond lasers create LASIK flaps with better accuracy, uniformity, and predictability than mechanical microkeratomes. Newer higher-frequency femtosecond platforms elicit less inflammation, producing better visual outcomes. SMILE achieved similar safety, efficacy, and predictability as LASIK with greater preservation of corneal nerves and biomechanical strength. The emergence of wavefront technology has resulted in improved excimer laser treatments. Comparisons of wavefront-guided and wavefront-optimized treatments suggest that there is an advantage to using wavefront-guided platforms in terms of visual acuity and quality of vision. Topography-guided ablations are another well tolerated and effective option, especially in eyes with highly irregular corneas. Advances in femtosecond and excimer laser technology have not only improved the safety and efficacy of refractive procedures, but have also led to the development of promising new treatment modalities, such as SMILE and the use of wavefront-guided and topography-guided ablation. Future studies and continued technological progress will help to better define the optimal use of these treatment platforms.

  13. Color-center laser spectroscopy of transient species produced by excimer-laser flash photolysis

    Energy Technology Data Exchange (ETDEWEB)

    Adams, H.; Hall, J.L.; Rusell, L.A.; Kasper, J.V.V.; Tittel, F.K.; Curl, R.F.,JR.

    1985-05-01

    Kinetic spectroscopy based on excimer-laser flash photolysis and color-center-laser (CCL) infrared probing is explored. In simiple absorption, the achievable signal-to-noise ratio (S/N) is not satisfactory even though the signal itself (corresponding to greater than 1 percent absorption) is fairly large. This is due to amplitude fluctuations of the CCL. By using a double-beam detection scheme to balance out these amplitude fluctuations the sensitivity can be improved to the extent that a 1 percent absorption gives a S/N approximately 100. In certain situations transient decreases in absorption of the precursor and transient increases in absorption due to final product formation can produce severe interferinng signals even in simple systems. This problem is overcome without a major loss in sensitivity by a recently developed 45 deg magnetic rotation scheme. These points are illustrated with spectra of Br, OH, and NH2. 21 references.

  14. High Efficiency Mask Based Laser Materials Processing with TEA-CO2 - and Excimer Laser

    DEFF Research Database (Denmark)

    Bastue, Jens; Olsen, Flemmming Ove

    1997-01-01

    In general, mask based laser materials processing techniques suffer from a very low energy efficiency. We have developed a simple device called an energy enhancer, which is capable of increasing the energy efficiency of typical mask based laser materials processing systems. A short review of the ...... line marking with TEA-CO2 laser of high speed canning lines. The second one is manufactured for marking or microdrilling with excimer laser.......In general, mask based laser materials processing techniques suffer from a very low energy efficiency. We have developed a simple device called an energy enhancer, which is capable of increasing the energy efficiency of typical mask based laser materials processing systems. A short review...... of the most widely used applications of these systems is given and the potential advantages of the energy enhancer are discussed.The basic principle behind the energy enhancing technique is explained and two new energy enhancers are presented and evaluated. The first one is designed especially for single text...

  15. Curative effects of excimer laser corneal refractive surgery for hyperopic anisometropic amblyopia

    Directory of Open Access Journals (Sweden)

    Xin-Gang Nie

    2017-07-01

    Full Text Available AIM: To investigate curative effects of excimer laser corneal refractive surgery for adults or older adolescent with hyperopic anisometropic amblyopia. METHODS: From March 2014 to March 2016, we selected 26 cases 26 eyes of adults or older adolescent with hyperopic anisometropic amblyopia in our hospital. All eyes underwent laser in situ keratomileusis, observed for the uncorrected visual acuity(UCVA, best corrected visual acuity(BCVA, diopter and stereopsis. RESULTS: At the end of the follow-up, the patient's spherical equivalent and anisometropia were 1.47±0.51D and 1.15±0.22D, were significantly lower than that before operation(PPPCONCLUSION: In adult or older adolescent with hyperopic anisometropic amblyopia, excimer laser corneal refractive surgery has a certain effect.

  16. Transformation of microcrystalline silicon films by excimer-laser-induced crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, I.-C. [Department of Electrical Engineering, Da-Yeh University, Changhua 515, Taiwan (China); Lien, S.-Y. [Department of Materials Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung Taiwan 402, (China); Wuu, D.-S. [Department of Materials Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung Taiwan 402 (China)]. E-mail: dsw@dragon.nchu.edu.tw

    2005-02-01

    We describe the excimer-laser-induced crystallization of microcrystalline silicon films deposited by plasma-enhanced chemical vapor deposition (PECVD). Microcrystalline silicon films containing 2 at.% hydrogen can be used as precursor films for the laser recrystallization process without a dehydrogenation step, and provide a wider laser energy fluence process window than the previous explosive recrystallization for low temperature polysilicon (poly-Si) thin-film transistor (TFT) fabrication. Ellipsometry, transmission electron microscopy (TEM), and atomic force microscopy (AFM) are used to evaluate the laser irradiated films. Specially, we describe using atomic force microscopy to obtain plane-view grain microstructure images.

  17. EVALUATION OF SKIN-CANCER RISK RESULTING FROM LONG-TERM OCCUPATIONAL EXPOSURE TO RADIATION FROM ULTRAVIOLET-LASERS IN THE RANGE FROM 190 TO 400 NM

    NARCIS (Netherlands)

    Sterenborg, H. J.; de Gruijl, F. R.; Kelfkens, G.; van der Leun, J. C.

    1991-01-01

    The relative risk of occupational exposure to radiation from UV lasers was estimated using a mathematical model based on both epidemiological data and animal experiments. Calculations were performed for the 193 nm ArF excimer laser cornea shaping, the 308 nm XeCl excimer laser for coronary

  18. Influence of corneal collagen crosslinking with riboflavin and ultraviolet-a irradiation on excimer laser surgery.

    Science.gov (United States)

    Kampik, Daniel; Ralla, Bernhard; Keller, Sabine; Hirschberg, Markus; Friedl, Peter; Geerling, Gerd

    2010-08-01

    Riboflavin/ultraviolet A (UVA) cross-linking (CXL) of corneal collagen is a novel method of stabilizing corneal mechanical properties and preventing progression of keratectasias. This study was conducted to investigate whether CXL influences ablation rate, flap thickness, and refractive results of excimer laser procedures ex vivo. Corneal epithelium was removed from enucleated porcine eyes, and CXL was performed with riboflavin 0.1% and UVA radiation (365 nm, 3 mW/cm(2)) for 30 minutes. Control eyes received epithelial abrasion only. Diffusion of riboflavin through the cornea was assessed by using infrared-excited, two-photon microscopy of riboflavin autofluorescence, combined with second-harmonic generation of fibrillar collagen. During phototherapeutic keratectomy, corneal thickness was measured by optical coherence pachymetry. During LASIK for myopia, the flap thickness of microkeratome cuts was measured and the induced refractive change assessed by Placido topography. Data were analyzed by Shapiro-Wilk test and Student's t-test. Multiphoton imaging showed a rapid (30-minute) and even distribution of riboflavin throughout the corneal stroma. No difference in ablation rate was measured in treated and untreated corneas (P = 0.90). Mean flap thickness was increased by 44% in cross-linked corneas (P refractive change was reduced in CXL-treated eyes by 20.1% (P refractive change after LASIK for myopia. Although the laser ablation rate is unaffected, CXL results in an increased flap thickness. This study suggests the need for adjustment of microkeratome and laser parameters for LASIK after CXL and indirectly endorses the theory of a direct stiffening effect of CXL.

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

    Science.gov (United States)

    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.

  20. Excimer laser refractive surgery versus phakic intraocular lenses for the correction of moderate to high myopia.

    Science.gov (United States)

    Barsam, Allon; Allan, Bruce D S

    2014-06-17

    Myopia is a condition in which the focusing power (refraction) of the eye is greater than that required for clear distance vision. There are two main types of surgical correction for moderate to high myopia; excimer laser and phakic intraocular lenses (IOLs). Excimer laser refractive surgery for myopia works by removing corneal stroma to lessen the refractive power of the cornea and to bring the image of a viewed object into focus onto the retina rather than in front of it. Phakic IOLs for the treatment of myopia work by diverging light rays so that the image of a viewed object is brought into focus onto the retina rather than in front of the retina. They can be placed either in the anterior chamber of the eye in front of the iris or in the posterior chamber of the eye between the iris and the natural lens. To compare excimer laser refractive surgery and phakic IOLs for the correction of moderate to high myopia by evaluating postoperative uncorrected visual acuity, refractive outcome, potential loss of best spectacle corrected visual acuity (BSCVA) and the incidence of adverse outcomes. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to February 2014), EMBASE (January 1980 to February 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 February 2014. We included randomised controlled trials (RCTs) comparing excimer laser refractive surgery and phakic IOLs for the correction of myopia greater than 6.0 diopters (D) spherical equivalent. Two authors independently

  1. Discharge instabilities in high-pressure fluorine based excimer laser gas mixtures

    OpenAIRE

    Mathew, D

    2007-01-01

    Fluorine based excimer lasers such as KrF, ArF and F2 are currently the most powerful sources available in the ultraviolet wavelength range, operating at 248 nm, at 193 nm and at 157 nm, respectively. They are thus of central importance for numerous applications in this range. At these short wavelengths, reaching the laser threshold for an efficient operation, F2-based lasers require to be pumped, in a controlled manner, with very high power densities. This can practically be achieved only vi...

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

    OpenAIRE

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

    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 cor...

  3. Electron microscopic and immunohistochemical examination of scarred human cornea re-treated by excimer laser.

    Science.gov (United States)

    Bleckmann, Heinrich; Schnoy, Norbert; Kresse, Hans

    2002-04-01

    To elucidate differences, at the macromolecular level, in corneal tissue subjected to repeated argon fluoride excimer treatment. A light microscopic, electron microscopic, and immunohistochemical study was performed on a scarred human cornea. Keratocytes were enlarged with an expanded endoplasmic reticulum and exhibited a fibroblastic appearance. Amorphous material was observed extracellularly. Collagen fibrils exhibited a disordered arrangement while banding patterns and diameter were normal. Immunohistochemical investigation of several collagen types, of collagen-associated proteoglycans, and of basement membrane components demonstrated an enhanced immunoreactivity of all of them in the scarred area. Type V collagen was found as a normal component of the epithelial basement membrane whereas types I and III collagen were present beneath Bowman's layer. Excimer-laser-treated sections revealed considerably stronger subepithelial staining for collagen types I, III, IV, and V. Laminin-1, a typical component of basement membranes, was detectable throughout the scarred tissue. The small proteoglycans decorin and fibromodulin accumulated in a patch-like manner in the scarred tissue below the epithelium, whereas biglycan was expressed by the epithelium and throughout the stroma. Lumican was expressed most strongly by the epithelium and rather equally distributed in the excimer-laser-treated and in the normal stroma. Effects of argon laser treatment of the cornea must be regarded as a process acting over many months. Intra- and extracellular structures and components are involved and influence the unpredictable shape of the corneal architecture.

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

    Energy Technology Data Exchange (ETDEWEB)

    Michaljaničová, I. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Heitz, J.; Barb, R.A. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Sajdl, P. [Department of Power Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague (Czech Republic)

    2015-06-01

    Highlights: • The influence of ArF and KrF laser on biopolymer surface was determined. • ArF laser acts predominantly on biopolymer surface. • PHB roughness is increased similarly for both applied wavelengths. • Roughness of nanostructures can be precisely controlled. • ArF laser introduces nitrogen on PHB surface. - Abstract: The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  5. Surface ablation of PLLA induced by KrF excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Michaljaničová, I. [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Sajdl, P. [Department of Power Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic); Fitl, P. [Department of Physics and Measurements, Faculty of Chemical Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague (Czech Republic)

    2013-10-15

    The surface characterization of PLLA (poly-L-lactic-acid) and its ablation due to excimer laser treatment is introduced in this paper. The main focus is to determine surface wettability and morphology changes in combination with changes of surface chemistry. The ablation loss and the determination of ablation threshold were used to study the biopolymer stability when treated to different laser fluences and pulse counts. The surface polarity was estimated using goniometry. AFM (atomic force microscopy) was used to determine the polymer surface morphology and roughness. The excimer laser has a strong effect on the polymer ablation. The thickness loss is strongly dependent on the laser fluence and number of pulses. For the fluences up to 30 mJ cm{sup −2} and 6000 pulses achieved ablation about 5 μm. The glass transition temperature and melting point were determined for the pristine and laser treated films. The increasing pulsed laser fluence leads to the major changes in roughness and morphology. The surface chemistry depends strongly on number of laser pulses.

  6. [Retinal detachment after Excimer laser (myopic LASIK or PRK). A retrospective multicentric study: 15 cases].

    Science.gov (United States)

    Feki, J; Trigui, A; Chaabouni, M; Ben Salah, S; Bouacida, B; Chechia, N; Zayani, A; Nouira, F; Daghfous, F; Ayed, S; Kamoun, M

    2005-05-01

    Refractive surgery by LASIK or photorefractive keratectomy (PRK) generaly aims at a myopic population that has a high probability of developing rhegmatogenous retinal detachment (RD). The authors report a multicenter study with 15 cases of RD appearing after refractive surgery by Excimer laser and discuss the role played by the techniques used. Five centers fitted with nine Excimer laser devices took part in this study. Of 22,700 eyes undergoing refractive myopic surgery during the period 1994-2002, 15 eyes developed rhegmatogenous RD. The average age of the patients with RD was 37 years. The average myopia was 13.5 D. RD occurred a mean of 20 months after refractive laser. Fifteen eyes of 13 patients developed a rhegmatogenous RD, two of which were bilateral. Eight of these cases had LASIK surgery and six had photorefractive keratectomy; one of the latter patients was retreated with LASIK because of substantial regression after PRK. RD was total or subtotal in five eyes, partial superior with a temporal tear in six eyes, and nasal in three eyes. One case with inferior RD, two cases with giant retinal tear and one case with posterior tear were also repaired. Fourteen eyes were suitable for operation. The retina was reattached in 12 cases. Mean postoperative visual acuity was 7/10. The occurrence of rhegmatogenous RD in the myopic population is estimated at 2.2%. It is estimated at 0.1% in the emmetropic population. The Excimer laser, through its thermic effects, shock wave, traumatism undergone by the suction ring at the time of LASIK surgery, could increase this risk in myopic patients. A review of the literature cast doubt on the cause and effect hypothesis. Personal and multicenter studies (including ours) show that the frequency rate of rhegmatogenous RD after Excimer laser is equivalent and even lower than that estimated with an emmetropic population. The low percentage of RD after Excimer surgery found in the literature as well as in our study (surgery, the

  7. Fabrication of SERS Active Surface on Polyimide Sample by Excimer Laser Irradiation

    Directory of Open Access Journals (Sweden)

    T. Csizmadia

    2014-01-01

    Full Text Available A possible application of excimer laser irradiation for the preparation of surface enhanced Raman spectroscopy (SERS substrate is demonstrated. A polyimide foil of 125 μm thickness was irradiated by 240 pulses of focused ArF excimer laser beam (λ = 193 nm, FWHM = 20 ns. The applied fluence was varied between 40 and 80 mJ/cm2. After laser processing, the sample was coated with 40 nm silver by PLD in order to create a conducting layer required for the SERS application. The SERS activity of the samples was tested by Raman microscopy. The Raman spectra of Rhodamine 6G aqueous solution (c=10−3 mol/dm3 were collected from the patterned and metalized areas. For areas prepared at 40–60 mJ/cm2 laser fluences, the measured Raman intensities have shown a linear dependence on the applied laser fluence, while above 60 mJ/cm2 saturation was observed. The morphology of the SERS active surface areas was investigated by scanning electron microscopy. Finite element modeling was performed in order to simulate the laser-absorption induced heating of the polyimide foil. The simulation resulted in the temporal and spatial distribution of the estimated temperature in the irradiated polyimide sample, which are important for understanding the structure formation process.

  8. The development and progress of XeCl Excimer laser system

    Science.gov (United States)

    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.

  9. Scattered ultraviolet emissions during refractive surgery using a high-frequency, wavefront-optimized excimer laser platform.

    Science.gov (United States)

    Bower, Kraig S; Edwards, Jayson D; Ryan, Denise Sediq; Coe, Charles D; Hope, Robert J; Sliney, David H

    2010-08-01

    To evaluate occupational ultraviolet (UV) exposure during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the Allegretto Wave Eye-Q 400 Hz excimer laser. Walter Reed Center for Refractive Surgery, Washington, DC, USA. Intraoperative UV measurements were performed during PRK with epithelial removal using an Amoils brush, PRK with epithelial removal using 20% ethanol, or femtosecond LASIK. A LaserStar power/energy meter with a silicone detector (model PD-10) was used for the measurements. The maximum pulse energy 25.4 cm from the corneal surface was recorded for each surgical procedure. Measurements were evaluated using a worst-case scenario for exposure of operating room personnel, and the results were compared with the occupational exposure limit set by the International Commission on Non-Ionizing Radiation Protection. Measurements were taken during 15 cases of each procedure. The mean maximum exposure was 129.38 nJ/pulse +/- 79.48 (SD) during brush PRK, 69.72 +/- 68.80 nJ/pulse during ethanol PRK, and 29.17 +/- 13.82 nJ/pulse during LASIK. The mean maximum exposure per eye was 0.085 mJ/cm(2), 0.046 mJ/cm(2), and 0.01 mJ/cm(2), respectively. The worst-case cumulative exposure during a heavy workday of 20 patients (40 eyes) was calculated at 3.92 mJ/cm(2), 1.51 mJ/cm(2), and 0.79 mJ/cm(2) for brush PRK, ethanol PRK, and LASIK, respectively. Results indicate that the excimer laser platform used in the study may yield greater UV exposure than previous systems; however, the levels did not exceed occupational exposure limits. No author has a financial or proprietary interest in any material or method mentioned. Published by Elsevier Inc.

  10. Green synthesis of selenium nanoparticles by excimer pulsed laser ablation in water

    Directory of Open Access Journals (Sweden)

    O. Van Overschelde

    2013-10-01

    Full Text Available Pure selenium nanoparticles were successfully synthesized by Liquid Phase - Pulsed Laser Ablation (LP-PLA in de-ionized water. Excimer laser (248 nm operating at low fluence (F ∼ 1 J/cm2 was used to generate colloidal solutions of selenium nanoparticles. The obtained selenium nanoparticles were characterized by UV-visible spectroscopy, Raman spectroscopy, Dynamic Light Scattering, and Transmission Electron Microscopy. We describe the multi-modal size distributions generated and use the centrifugation method to isolate the smallest nanoparticles (∼60 nm in diameter.

  11. Effects of excimer laser annealing on low-temperature solution based indium-zinc-oxide thin film transistor fabrication

    OpenAIRE

    Chen,Chao-Nan; Huang, Jung-Jie

    2015-01-01

    A Solution Based Indium-Zinc-Oxide thin-film transistor (TFT) with a field-effect mobility of 0.58 cm2/Vs, a threshold voltage of 2.84 V by using pulse laser annealing processes. Indium-zinc-oxide (IZO) films with a low process temperature were deposited by sol-gel solution based method and KrF excimer laser annealing (wavelength of 248 nm). Solution based indium-zinc-oxide (IZO) films usually needs high temperature about 500 °C post annealing in a oven. KrF excimer laser annealing shows adva...

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Benerji, N. S., E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra, E-mail: nsb@rrcat.gov.in, E-mail: bsingh@rrcat.gov.in [Excimer Laser Section, LMPD, Raja Ramanna Center for Advanced Technology, Indore 452013 (India)

    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.

  14. Reconsidering Sequential Double Running Suture Removal After Penetrating Keratoplasty: A Prospective Randomized Study Comparing Excimer Laser and Motor Trephination.

    Science.gov (United States)

    Seitz, Berthold; Hager, Tobias; Langenbucher, Achim; Naumann, Gottfried O H

    2017-12-14

    We assessed the impact of sequential double running suture removal on corneal curvature after penetrating keratoplasty (PK), comparing mechanical and nonmechanical excimer laser trephination. PK was performed in 134 patients (mean age 51 ± 18 yrs) using either the excimer laser [excimer, n = 60 (37 keratoconus and 23 Fuchs dystrophy)] or motor trephination [control, n = 74 (44 keratoconus and 30 Fuchs dystrophy)] and a double running cross-stitch suture. Refractometry, Zeiss keratometry, and Tomey corneal topography were performed before removal of the first suture (15.2 ± 4.2 mo) and immediately before and at least 6 weeks after removal of the second suture (21.4 ± 5.6 mo). Keratometry before removal of the first (-1.7 ± 2.3 D vs. -3.1 ± 2.8 D) and second (-2.3 ± 2.6 D vs. -3.8 ± 2.8 D) sutures showed that the change in the corneal base curve was significantly smaller in the excimer group than the control group (P control groups, respectively, resulting in significantly lower astigmatism in the excimer (3.1 ± 2.1 D) group compared with the control group (6.2 ± 2.9 D) with "all-sutures-out" (P vector-corrected astigmatism (Jaffe) was significantly smaller in the excimer group (4.3 ± 3.5 D) than in the control group (6.9 ± 4.5 D; P motor trephination.

  15. Plume emission, shock wave and surface wave formation during excimer laser ablation of the cornea.

    Science.gov (United States)

    Bor, Z; Hopp, B; Rácz, B; Szabó, G; Ratkay, I; Süveges, I; Füst, A; Mohay, J

    1993-01-01

    Excimer lasers are now used for corneal surgery; however, the physical processes occurring during photoablation of the cornea are incompletely understood. High speed laser-based photographic arrangement was constructed. The temporal resolution was better than 1 ns. The setup could work as a Schlieren arrangement, which is sensitive to the refractive index change caused by the shock wave propagating in the air above the eye. With minor changes the setup was converted into a shadowgraph, which could detect the ablation plume and the waves propagating on the surface of the eye. Due to the impact of the excimer laser pulse onto the surface of the cornea, a shock wave was generated in the air. The shadowgraph clearly showed the ejection of the ablated cornea. The ejection velocity of the plume was found to be over 600 m/s. It was shown for the first time that the recoil forces of the plume are generating a wave on the surface of the eye. The laser-based high speed photographic arrangement is a powerful arrangement in the study of physical effects occurring during photoablation of the cornea.

  16. Investigation of the effects of LIFT printing with a KrF-excimer laser on thermally sensitive electrically conductive adhesives

    NARCIS (Netherlands)

    Perinchery, S.M.; Smits, E.C.P.; Sridhar, A.; Albert, P.; Brand, J. van den; Mandamparambil, R.; Yakimets, I.; Schoo, H.F.M.

    2014-01-01

    Laser induced forward transfer is an emerging material deposition technology. We investigated the feasibility of this technique for printing thermally sensitive, electrically conductive adhesives with and without using an intermediate dynamic release layer. A 248nm KrF-excimer laser was used to

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

    NARCIS (Netherlands)

    Naithani, S.; Schaubroeck, D.; Vercammen, Y.; Mandamparambil, R.; Yakimets, I.; Vaeck, L. van; Steenberge, G. van

    2013-01-01

    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

  18. Excimer laser micromachining of oblique microchannels on thin ...

    Indian Academy of Sciences (India)

    The edge roughness of the channels, machined with a square laser spot of side 100lm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping ...

  19. Preliminary results of VISX excimer laser myopic photorefractive keratectomy at Cedars-Sinai Medical Center

    Science.gov (United States)

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

    1992-08-01

    Sixty-two eyes underwent excimer laser photorefractive keratectomy (PRK) for the correction of myopia at Cedars-Sinai-Medical-Center. The first group of 12 patients are presented with follow up data of ten months postoperatively. The second group of 50 patients are presented with follow up data of three months postoperatively. An in-depth comparison of pre and postoperative refractive data is presented. Comparisons between pre and postoperative corrected and uncorrected Snellen visual acuities are provided in order to asses the functional visual result of the procedure.

  20. Generation of large-area microscale manifolds using excimer laser ablation

    Science.gov (United States)

    Zhou, Simon; Kilgo, Marvin M., III; Williams, Charles N.

    1999-08-01

    Excimer laser ablation of polymeric materials is a widely used technology for the generation of nozzles and through- holes. Ablation is also a viable process to create more complex fluidic structures such as channels and manifolds. This paper presents recent results of experiments demonstrating the creation of manifolds in 25 micrometers polyimide films. These structures include cross-over points, and channels of various widths. The results presented include photomicrographs and SEMS, and characterization of channel wall taper and width control as well as an assessment of ablation depth uniformity over large fields. The characteristics of projection ablation systems are reviewed, and the experimental system is described in detail.

  1. Important technological problems with stable operation of electron beam pumped KrF excimer laser amplifier

    CERN Document Server

    Ma Wei Yi; Hu Feng Ming; Shan Yu Sheng; Wang Nai Yan

    2002-01-01

    Some important technological problems with stable operation of the two-side electron beam pumped main amplifier used in the 'Heaven-1' high power KrF excimer laser system are described. They are the problems of the electric breakdown of the insulator support for water dielectric transmission lines, anode foil installation of large area electron beam diode, shape of Hibachi ribs that contact the pressure foil, and formation of diode post pulses and their damage to the anode foil and cathode emitter. Emphasis is put on the effect of different main-switch breakdown times on diode post pulses and the determination of the optimal breakdown time

  2. Excimer laser reactive deposition of vanadium nitride thin films

    Science.gov (United States)

    D'Anna, E.; Di Cristoforo, A.; Fernández, M.; Leggieri, G.; Luches, A.; Majni, G.; Mengucci, P.; Nanai, L.

    2002-01-01

    We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5-200 Pa), KrF laser fluence (4.5-19 J/cm 2), substrate temperature (20-750 °C) and target-to-substrate distance (30-70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2) on substrates at room temperature. At the N 2 pressures of 1-10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm 2), the dominant phase is V 2N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  5. Applicability of KrF excimer laser induced fluorescence in sooting high-pressure flames

    Energy Technology Data Exchange (ETDEWEB)

    Hildenbrandt, F.; Schulz, C.; Sick, V.; Jander, H.; Wagner, H.G.

    1999-07-01

    Laser-induced emissions obtained after excitation with a tunable KrF excimer laser at 248 nm were measured in well-defined sooting laminar high-pressure flames fueled with methane/air and ethylene/air up to 15 bar. A spectral analysis shows that Mie scattering, Raman scattering and laser-induced fluorescence (LIF) signals can be used for detailed flame studies under sooting high-pressure conditions. Mie scattering is correlated with soot, Raman signals can be used to measure spatially-resolved major species concentrations as well as temperatures. A LIF-scheme to measure NO was found to be applicable even under these conditions. The broadband fluorescence in the range from 270 to 290 nm, usually discarded as background, correlates well with the total concentration of polycyclic aromatic hydrocarbons (PAH) as measured via GC-MS methods. (orig.)

  6. Processing of bioglass coatings by excimer laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Serra, J.; Gonzalez, P.; Chiussi, S.; Leon, B.; Perez-Amor, M. [Vigo Univ. (Spain). Dept. de Fisica Aplicada

    2001-07-01

    Bioglass (BG) coatings have been prepared in different N{sub 2}O atmospheres by pulsed laser deposition (PLD) using a BG target and an ArF laser. Changes in composition and refractive index were observed by Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS) and single-wavelength ellipsometry. Film thicknesses were measured by profilometry and surface morphology was observed by scanning electron microscopy (SEM). It has been shown that target composition is transferred to the substrate and that films properties can be modified using different N{sub 2}O atmospheres during the growth process. We observed also a gradual variation of the film refractive index with increasing N{sub 2}O pressures and FTIR spectra reveal that the formation of non-bridging oxygen bonds in the coatings can be controlled. It is well-known, that these bond units determine the formation of apatite on the surfaces of bioactive glass coatings (BGCs) after being soaked in simulated body fluid (SBF), which is an essential characteristic of biocompatibility. (orig.)

  7. Regression and wound healing after excimer laser PRK: a histopathological study on human corneas.

    Science.gov (United States)

    Lohmann, C P; Patmore, A; O'Brart, D; Reischl, U; Winkler Mohrenfels, C; Marshall, J

    1997-01-01

    The results of excimer laser PRK are promising as more than 80% of eyes with up to -6.0 diopters of attempted correction have refractive results within 1.0 diopter of emmetropia. However, throughout the dioptric range some unexpected results have been observed with individual patients showing an aggressive wound healing response with excessive myopic regression and severe corneal haze. Unfortunately, only limited data are available about the cellular and extracellular responses in human corneas after PRK and this information is important to establish adequate postoperative pharmaceutical treatment. We made a histopathological and immunohistochemical study on 20 human corneal samples from patients with severe corneal haze and myopic regression. The indirect immunofluorescence method was used for demonstration of collagen types I, III, IV laminin, chondroitin sulphate, dermatan sulphate, and keratin. All corneal specimens showed a hyperplastic epithelium. Histologically, most samples (16/20) showed mainly a loose lamination of extracellular material which could be identified as collagen type IV. The remaining four samples had newly synthesised collagen type III. Our histopathological results indicate that corneal wound healing after excimer laser PRK varies among individuals. In some people epithelial basement proteins, such as collagen type IV, are the main wound healing products, whereas in others mainly collagen type III is found postoperatively, which does not effect the synthesis of collagen type IV. This suggests the need for individually-tailored postoperative pharmaceutical treatment regimens.

  8. Immunofluorescence study of corneal wound healing after excimer laser anterior keratectomy in the monkey eye.

    Science.gov (United States)

    Malley, D S; Steinert, R F; Puliafito, C A; Dobi, E T

    1990-09-01

    We performed anterior keratectomies on six monkey eyes, four by excimer laser large-area ablation at 193 nm and two by mechanical keratectomy. Immunofluorescence was used to study the wound healing response histopathologically. The distribution of fibrinogen, fibronectin, laminin, collagen types III, IV, and VI, and keratan sulfate was determined at postoperative intervals of 24 hours, 6 days, and 1 month. At 24 hours, fibrinogen and fibronectin coated the ablated surface, but corneal epithelial cells had not yet migrated over the wound. By 6 days and persisting at 1 month, an epithelial ingrowth of seven to 10 layers, mild stromal hypercellularity, and new collagen formation were present in the repair region. At 1 month, fibrinogen, fibronectin, laminin, and type III collagen were strongly detected in the repair region. Type VI collagen was present in both normal and healed corneal stroma at all intervals, and type IV collagen was present in Descemet's membrane only. Sulfated keratan sulfate was absent from the newly synthesized collagen stroma at all intervals. Slit-lamp photographs demonstrated corneal haze in the ablation zone in all cases at 24 hours, persisting for 1 month. The fluorescence patterns produced by excimer laser ablation and mechanical keratectomy were qualitatively identical.

  9. A new transepithelial phototherapeutic keratectomy mode using the NIDEK CXIII excimer laser.

    Science.gov (United States)

    Buzzonetti, Luca; Petrocelli, Gianni; Laborante, Antonio; Mazzilli, Emilio; Gaspari, Mario; Valente, Paola; Francia, Elisa

    2009-01-01

    To evaluate epithelial healing, postoperative pain, and best spectacle-corrected visual acuity (BSCVA) after transepithelial photorefractive keratectomy (PRK) performed with a new phototherapeutic keratectomy (PTK) mode using the NIDEK CXIII excimer laser. Fifteen eyes from 10 patients with myopia underwent transepithelial PRK using a multistage program to perform PTK followed by PRK. The PTK incorporated Flex Scan, which accounts for the loss of radial ablation efficiency on the peripheral cornea. The epithelium was removed with the excimer laser by monitoring the disappearance of blue fluorescence during the ablation. Epithelial healing was evaluated by taking slit-lamp photographs every 24 hours until complete reepithelialization. Postoperative pain was measured according to the Faces Pain Rating Scale. All outcomes are reported for 3 months postoperatively. Haze was graded by two ophthalmologists, each masked to the other's result. Mean reepithelialization took 3.50+/-0.85 days, mean pain score was 3.00+/-1.20, and BSCVA was 20/20 for 9 eyes, 20/30 for 3 eyes, and 20/40 for 3 eyes. All patients had haze below grade 2. The outcomes of the preliminary study show that the incorporation of the Flex Scan algorithm in the PTK mode is as safe and effective as conventional PTK algorithms. The primary advantage of this new PTK mode may be more consistent epithelial removal. Additional studies are needed to determine long-term outcomes.

  10. Pain after epithelial removal by ethanol-assisted mechanical versus transepithelial excimer laser debridement.

    Science.gov (United States)

    Kanitkar, K D; Camp, J; Humble, H; Shen, D J; Wang, M X

    2000-01-01

    To compare subjective pain responses between two techniques of epithelial removal prior to photorefractive keratectomy (PRK) treatment: ethanol-soaked pledget with mechanical debridement of the epithelium versus excimer laser transepithelial ablation. Nine patients underwent bilateral PRK. Each had the epithelium in one eye debrided by placing a pledget soaked in 20% ethanol on the cornea for 2 minutes followed by gentle scraping with a blade. The epithelium in the other eye was removed by transepithelial phototherapeutic keratectomy (PTK) treatment. For each eye, PRK was initiated immediately after removal of the epithelium. On postoperative day one, each patient was asked to rate the level of pain suffered over the last 24 hours on a scale of 0 (minimal) to 10 (maximal). Data were analyzed in a masked fashion. Postoperative day one average pain level in the ethanol-assisted mechanically debrided eyes was 3.0 +/- 2.5 and in the transepithelial PTK eyes was 6.8 +/- 1.8. The difference was statistically significant by Student's t-test (P < .01). All epithelial defects healed within 3 days with no clinically significant difference in healing time between the two techniques. In preparation for PRK, ethanol-assisted mechanical debridement of the epithelium caused significantly less postoperative pain than epithelial removal using the excimer laser.

  11. Photosensitivity and stress changes of Ge-free Bi-Al doped silica optical fibers under ArF excimer laser irradiation.

    Science.gov (United States)

    Ban, Christian; Limberger, Hans G; Mashinsky, Valery; Dianov, Evgeny

    2011-12-19

    The photosensitivity of germanium free Bi-Al-doped silica fibers with different bismuth concentrations was investigated using ArF excimer laser radiation at 193 nm and fiber grating formation. For the fiber with the highest bismuth concentration maximum refractive index changes of 2.2 × 10(-3) and 2.0 × 10(-4) were obtained for hydrogen loaded and unloaded fibers, respectively. Irradiation induced tensile stress changes were observed in the fiber core of H(2)-loaded and unloaded fibers. The results indicate a contribution of compaction to the total refractive index change in both cases.

  12. Validade da topografia de córnea na cirurgia refrativa com excimer laser Validity of corneal topography in refractive surgery with excimer laser

    Directory of Open Access Journals (Sweden)

    Orlando da Silva Filho

    2003-12-01

    Full Text Available OBJETIVO: Avaliar os resultados refracionais e a segurança do procedimento cirúrgico PRK (ceratectomia fotorrefrativa com base na topografia de córnea no pré-operatório. MÉTODOS: Participantes - 44 sujeitos que tinham realizado cirurgia refrativa, com o procedimento ceratectomia fotorrefrativa, os quais apresentaram topografias irregulares pré-operatórias. O grupo controle consistiu de 44 sujeitos com topografia regular pré-operatória. Os 88 olhos foram submetidos a ceratectomia fotorrefrativa utilizando-se o "Summit Apex plus Excimer Laser". As topografias irregulares e regulares foram obtidas pelo "Corneal Analysis System"(EyeSys, sendo consideradas como topografias irregulares os seguintes achados: ápice deslocado acima de 1,5 D (AD, asfericidade maior que 0,25 D/mm (AS, obliquidade maior que 15 graus (OB, assimetria inferior-superior igual ou maior que 1,5 D (IS, curvatura maior que 47 D (CU e combinação de 2 critérios (CB. Principal efeito medido: perda de uma ou mais linhas que foram definidas com segurança para o prognóstico. RESULTADOS: Todos os pacientes foram acompanhados por 6 meses. Verificou-se perda significativa de acuidade visual corrigida em pacientes submetidos ao procedimento PRK-AD (pPURPOSE: To evaluate the refractive results and safety of PRK (photorefractive keratectomy based on the preoperative corneal topography. METHODS: 44 operated eyes, using the photorefractive keratectomy process, and which presented preoperative topographical abnormalities. The control group consisted of 44 eyes with preoperative normal corneal topography. Eighty-eight eyes were submitted to the photorefractive keratectomy process using the Summit Apex plus Excimer Laser. Corneal topographies were accessed by the EyeSys Analysis system; the topographic abnormalities which were considered are the following: apex displacement above 1.5D (AD, asphericity above 0.25D/mm (AS, obliquity above 15 degrees (OB, inferior-superior asymmetry

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

    Science.gov (United States)

    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.

  14. Eye-Tracker-Guided Non-Mechanical Excimer Laser Assisted Penetrating Keratoplasty

    Directory of Open Access Journals (Sweden)

    Achim Langenbucher

    2013-03-01

    Full Text Available Purpose: The purpose of the study was to implement a new eye tracking mask which could be used to guide the laser beam in automated non-mechanical excimer laser assisted penetrating keratoplasty. Materials and methods: A new trephination mask design with an elevated surface geometry has been proposed with a step formation between conical and flat interfaces. Two recipient masks of 7.5/8.0 mm have been manufactured and tested. The masks have outer diameter of 12.5 mm, step formation at 10.5 mm, and slope of conical surfaces 15°. Its functionality has been tested in different lateral positions and tilts on a planar surface, and pig eye experiments. After successful validation on porcine eyes, new masks have been produced and tested on two patients. Results: The build-in eye tracking software of the MEL 70 was always able to capture the masks. It has been shown that the unwanted pigmentation/pattern induced by the laser pulses on the mask surface does not influence the eye-tracking efficiency. The masks could be tracked within the 18 × 14 mm lateral displacement and up to 12° tilt. Two patient cases are demonstrated. No complications were observed during the surgery, although it needs some attention for aligning the mask horizontally before trephination. Stability of eye tracking masks is emphasized by inducing on purpose movements of the patient head. Conclusion: Eye-tracking-guided penetrating keratoplasty was successfully applied in clinical practice, which enables robust tracking criteria within an extended range. It facilitates the automated trephination procedure of excimer laser-assisted penetrating keratoplasty.

  15. Effect of preionization, fluorine concentration, and current density on the discharge uniformity in F2 excimer laser gas mixtures

    NARCIS (Netherlands)

    Mathew, D.; Bastiaens, Hubertus M.J.; Boller, Klaus J.; Peters, P.J.M.

    2007-01-01

    The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal

  16. Evaluation and diffusion of excimer laser treatment of myopia in the United States and in the Netherlands

    NARCIS (Netherlands)

    Vondeling, H.; Rosendal, H.; Banta, D.

    1995-01-01

    Excimer laser photorefractive keratectomy (PRK) is an experimental treatment to correct myopia (short-sightedness) that is diffusing into use without convincing evidence of safety and efficacy. It has been claimed that PRK may render conventional methods of correcting myopia, such as wearing glasses

  17. High-efficient discharge-pumped ArF (193 nm) excimer laser with a TPI thyratron as a high-voltage switch

    Science.gov (United States)

    Razhev, Alexander M.; Zhupikov, Andrey A.; Churkin, Dmitry S.

    2007-06-01

    The results of using the thyratron of the TPI series (pseudo spark gap) as a high-voltage switch in the excitation system of ArF (193 nm) excimer laser are presented. The excitation system of the LC-inverter type based on TPI 10k/20 thyratron in absence of any non-linear elements was developed. An experimental investigation of the energy and temporal parameters of the pumping and lasing for ArF laser on the He:Ar:F II mixture with excitation system developed was carried out. The comparative analysis of the ArF laser pumping and radiation parameters in dependence of the high-voltage switch type such as a standard spark gap RU-65, and thyratron TPI 10k/20 was performed. The output radiation energy for a laser with thyratron TPI 10k/20 was obtained to be of 1.4 times higher than that with standard spark gap RU-65 at the same pumping conditions. Such increase the output energy was shown to be achieving owing to higher level of the pumping intensity due to higher voltage on the discharge gap that occurs due to lower energy losses into TPI thyratron in comparison with the RU- 65 spark gap and leads to more efficient energy transfer from storage to discharge circuit. As a result for ArF laser with TPI thyratron in He:Ar:F II mixture the output radiation energy of 1.0 J with the total efficiency of 1.7% has been achieved. The advantages of using the TPI thyratron in the excitation system of the ArF excimer laser over spark gap are described.

  18. Fabrication of the Long Bragg Grating by Excimer Laser Micro Machining with High-Precision Positioning XXY Platform

    Directory of Open Access Journals (Sweden)

    Jian-Zhong Wu

    2014-03-01

    Full Text Available With the advancement of technology, the application of fiber Bragg grating is widely used as a Bragg grating sensor. Fiber Bragg grating is fabrication using excimer laser machining with the phase masker. The grating length is decided by the width of laser beam. In this paper, we proposed fabrication of the long Bragg grating by excimer Laser micro machining with a high-precision positioning XXY platform. The high-precision positioning XXY platform plays an important role for long FBG. It needs seriously to combine three short FBGs. Therefore, we can obtain a long FBG with 15mm length. This method can provide a solution to fabricate long FBG by using cheap laser with high-precision positioning XXY platform.

  19. Excimer laser cleaning of encrustation on Pentelic marble: procedure and evaluation of the effects

    Science.gov (United States)

    Maravelaki-Kalaitzaki, P.; Zafiropulos, V.; Fotakis, C.

    1999-06-01

    This work focuses on the use and control of excimer lasers (KrF, λ=248 nm and XeCl, λ=308 nm) for the removal of encrustation (black crusts, soil-dust and biological deposits) from Pentelic marble. A number of surface analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) interfaced with microprobe analysis (energy dispersive X-ray analysis: EDX), X-ray diffraction (XRD), laser-induced breakdown spectroscopy (LIBS) and optical microscopy (OM) were used to detect chemical composition and crust morphology, as well as to monitor the effects induced by the laser treatment. SEM and OM providing structural information about the layers of encrustation, LIBS and SEM-EDX providing information on the elemental composition of the ablated material, XRD and FTIR detecting the changes of minerals appear to be particularly effective in assessing the quality of cleaning process. FTIR and XRD showed removal of pollutants from encrustation and partial transformation of calcium sulfate dihydrate (gypsum) to hemihydrate and anhydrite, which have lower specific surface than gypsum. Irradiation conditions creating minimal damaging effects were defined before treatment through surface analysis, ablation rate studies and optimization of laser parameters. On the basis of structural and analytical examinations, both lasers are shown to be appropriate for achieving sufficient removal of unwanted selected layers without modifying the surface morphology and surpassing by far the effectiveness afforded by traditional cleaning techniques.

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

    Science.gov (United States)

    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.

  1. Alternatives to excimer laser refractive surgery: UV and mid-infrared laser ablation of intraocular lenses and porcine cornea

    Science.gov (United States)

    Serafetinides, A. A.; Makropoulou, M.; Spyratou, E.; Bacharis, C.

    2007-03-01

    Despite the fact that the laser applications in human ophthalmology are well established, further research is still required, for better and predictable ablation dosimetry on both cornea tissue and intraocular lenses. Further studies for alternative laser sources to the well established excimer lasers, such as UV or mid-infrared solid state lasers, have been proposed for refractive surgery. The precise lens ablation requires the use of laser wavelengths possessing a small optical penetration depth in the cornea and in the synthetic lenses, in order to confine the laser energy deposition to a small volume. In order to eliminate some very well known problems concerning the reshaping of cornea and the modification of the optical properties of the intraocular lenses, ablation experiments of ex vivo porcine cornea, acrylic PMMA and hydrophilic lenses were conducted with an Er:YAG laser (2.94 μm) and the fifth harmonic of a Nd:YAG laser (213 nm). The morphology of cornea was recorded using a cornea topography system before and immediately after the ablation. Histology analysis of the specimens was obtained, in order to examine the microscopic appearance of the ablated craters and the existence of any thermal damage caused by the mid-infrared and UV laser irradiation. The macroscopic morphology of the intraocular lens craters was inspected with an optical transmission microscope. Measurements of the ablation rates of the lenses were performed and simulated by a mathematical model.

  2. Levels of interleukin-6 in tears before and after excimer laser treatment.

    Science.gov (United States)

    Resan, Mirko; Stanojević, Ivan; Petković, Aleksandra; Pajić, Bojan; Vojvodić, Danilo

    2015-04-01

    Immune response and consequent inflammatory process which originate on ocular surface after a trauma are mediated by cytokines. Photoablation of corneal stroma performed by excimer laser causes surgically induced trauma. Interleukin-6 (IL-6) is mostly known as a proinflammatory cytokine. However, it also has regenerative and anti-inflammatory effects. It is supposed that this cytokine is likely to play a significant role in the process of corneal wound healing response after photoablation of stroma carried out by laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) methods. The aim of this study was to determine and compare the levels of IL-6 in tears before and after treatment with LASIK and PRK methods. The study included 68 shortsighted eyes up to -3.0 diopter sphere, i.e. 198 samples of tears (per three samples taken from each of the eyes), divided into two groups according to the kind of excimer laser intervention performed: the group 1--eyes treated by LASIK method (n=31), and the group 2--eyes treated by the PRK method (n=37). The samples of tears were taken from each eye at the following time points: before excimer laser treatment (0 h, the control group), 1 h after the treatment (1 h) and 24 h after the treatment (24 h). The patients did not use anti-inflammatory therapy 24 h after the intervention. Tear samples were collected using microsurgical sponge. Level of IL-6 in tear fluid was determined by the flow cytometry method, applying a commercial test kit which allowed cytokine detection from a small sample volume. Results. The values of IL-6 were detectable in 16% of samples before LASIK treatment and in 30% of samples before PRK treatment. One h after the treatment IL-6 was detectable in 29% of samples for the LASIK group and 43% of samples for the PRK group, and 24 h after the treatment it was detectable in 19% of samples for the LASIK group and in 57% of samples for the PRK group. When we analyzed the dynamics of IL76 production

  3. Excimer-laser-based multifunctional patterning systems for optoelectronics, MEMS, materials processing, and biotechnology

    Science.gov (United States)

    Jain, Kanti

    2003-07-01

    Over the past few years, there has been an increasing impact of microelectronics fabrication technologies on the realization of structures and spatial patterns necessary for advances in optoelectronics, MEMS, materials processing, and biotechnology. These fabrication technologies accelerate the pace of research by enabling the micro-manipulation and patterning of a variety of organic, inorganic, and biological materials (including new polymers, compound semiconductors, DNA, proteins, and others), developing new synthesis techniques, and producing structures and devices previously not deemed possible. In order to facilitate the exploration of these fields, it is desirable to develop processing techniques and cost-effective, multifunctional systems that can handle a wide variety of substrate materials and geometries, including non-planar surfaces. This paper describes recent advances made in excimer-laser-based patterning, photoablation, and photo-crystallization technologies, focusing on how these technologies address the unique requirements of applications for scientific research and for technology development.

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

    Science.gov (United States)

    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.

  5. Pre-operative therapeutic eyelid hygiene in the prevention of complications following excimer laser vision correction

    Directory of Open Access Journals (Sweden)

    V. V. Kurenkov

    2012-01-01

    Full Text Available Purpose: to assess the effectiveness of pre-operative therapeutic eyelid hygiene in the prevention and treatment of dry eye and meibomian glands dysfunction following excimer laser vision surgery.Methods: In enrolled 144 patients (288 eyes, ocular surface and meibomian glands functions were evaluated before and following refractive surgery (LASIK and REIK. In pre- and post-operative period, standard ophthalmological studies were performed, including best-corrected visual acuity determination, biomicroscopy, Schirmer’s test and Norn’s test (tear break-up time. In pre-operative pe- riod, ocular surface microbial profile was assessed. Subjective symptoms of impaired tear production were revealed via questioning. In study group (70 patients, 140 eyes, therapeutic eyelid hygiene using Blefarogel 1 or Blefarogel 2 (Ltd. Heltec-Medica, Moscow, Russia was prescribed one week before surgery. In control group, no therapeutic eyelid hygiene was prescribed. All patients were received antibacterial treatment including Vigamox (Alcon, Fort Worth, tX. In both groups, Natural tears and Systane Ultra (Alcon were used as tear replacement therapy.Results: Complex treatment, including therapeutic eyelid hygiene in study group, significantly improved tear film and ocular sur- face health as well as meibomian glands functions. Inflammatory complications rate was estimated as 5.7% in study group and 10.6% in control group.Conclusion: therapeutic eyelid hygiene is highly effective in the prophylaxis and treatment of post-operative complications duу to ocular surface pathology and meibomian glands dysfunction. the procedure is safe and can be recommended as a part of complex preventive treatment before excimer laser vision correction.

  6. Pre-operative therapeutic eyelid hygiene in the prevention of complications following excimer laser vision correction

    Directory of Open Access Journals (Sweden)

    V. V. Kurenkov

    2014-07-01

    Full Text Available Purpose: to assess the effectiveness of pre-operative therapeutic eyelid hygiene in the prevention and treatment of dry eye and meibomian glands dysfunction following excimer laser vision surgery.Methods: In enrolled 144 patients (288 eyes, ocular surface and meibomian glands functions were evaluated before and following refractive surgery (LASIK and REIK. In pre- and post-operative period, standard ophthalmological studies were performed, including best-corrected visual acuity determination, biomicroscopy, Schirmer’s test and Norn’s test (tear break-up time. In pre-operative pe- riod, ocular surface microbial profile was assessed. Subjective symptoms of impaired tear production were revealed via questioning. In study group (70 patients, 140 eyes, therapeutic eyelid hygiene using Blefarogel 1 or Blefarogel 2 (Ltd. Heltec-Medica, Moscow, Russia was prescribed one week before surgery. In control group, no therapeutic eyelid hygiene was prescribed. All patients were received antibacterial treatment including Vigamox (Alcon, Fort Worth, tX. In both groups, Natural tears and Systane Ultra (Alcon were used as tear replacement therapy.Results: Complex treatment, including therapeutic eyelid hygiene in study group, significantly improved tear film and ocular sur- face health as well as meibomian glands functions. Inflammatory complications rate was estimated as 5.7% in study group and 10.6% in control group.Conclusion: therapeutic eyelid hygiene is highly effective in the prophylaxis and treatment of post-operative complications duу to ocular surface pathology and meibomian glands dysfunction. the procedure is safe and can be recommended as a part of complex preventive treatment before excimer laser vision correction.

  7. THE EXPERIENCE OF TREGALOZA BASED LUBRICANT USAGE FOR PATIENTS WHO UNDERWENT EXCIMER LASER SURGERY

    Directory of Open Access Journals (Sweden)

    E. Eskina

    2016-01-01

    Full Text Available Purpose: to evaluate the tregalose based eye drops effectiveness in patients who underwent PRK or TransPRK surgery. patients and methods: 50 patients with moderate myopia were examined before, 7 days and 1 month after PRK or TransPRK surgery made by SCHWIND Amaris excimer laser by the same surgeon. In addition to conventional diagnostics, Schirmer test and tear break up time were performed as well as ODSI questionare and Oxford index of ocular surface disorders were investigated. Patients were divided in two groups, Study group — “Thealos” group and “Control” group. In both groups patients have started using non preservative eye drops based on tregalosa and hyaluronic acid 4-th day after surgery respectively. results: The tear film breakup time was significantly better in “Thealos” group (7,22±3,61 sec 7 days postop and 9,36±3,68 sec 1 month postop in comparison to «Control” group 5,21±0,25 (р<0,01 sec and 7,21±2,85 sec respectively (р<0,05 as well as ocular surface index score in “Thealos” group post surgery was less (0,26±0,38 и 0,85±0,31 marks 7 days postop (р<0,05 and 0,09±0,19 and 0,21±0,4 (р<0,05 1 month postop respectively. There were no other statistically significant differences found in analysed data. Conclusion: Using of “Thealoz” non-preservative eye drops leads to faster recovery after surface excimer laser ablations in terms of dry eye manifestation, those as tearfilm stability and ocular surface index score, measured using “Oxford” scale. Moistening properties of tregaloze solution could be compared with those of hyaluronic acid solution.

  8. Microstructures induced by excimer laser surface melting of the SiCp/Al metal matrix composite

    Science.gov (United States)

    Qian, D. S.; Zhong, X. L.; Yan, Y. Z.; Hashimoto, T.; Liu, Z.

    2017-08-01

    Laser surface melting (LSM) was carried out on the SiCp/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm2. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

  9. Depth-profile investigations of triterpenoid varnishes by KrF excimer laser ablation and laser-induced breakdown spectroscopy

    Science.gov (United States)

    Theodorakopoulos, C.; Zafiropulos, V.

    2009-07-01

    The ablation properties of aged triterpenoid dammar and mastic films were investigated using a Krypton Fluoride excimer laser (248 nm, 25 ns). Ablation rate variations between surface and bulk layers indicated changes of the ablation mechanisms across the depth profiles of the films. In particular, after removal of the uppermost surface varnish layers there was a reduction of the ablation step in the bulk that was in line with a significant reduction of carbon dimer emission beneath the surface layers as detected by laser-induced breakdown spectroscopy. The results are explicable by the generation of condensation, cross-linking and oxidative gradients across the depth profile of triterpenoid varnish films during the aging degradation process, which were recently quantified and established on the molecular level.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dinca, V., E-mail: dincavalentina@yahoo.com [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Alloncle, P.; Delaporte, P. [Aix-Marseille University, CNRS, LP3 Laboratory, Campus de Luminy, 13288 Marseille (France); Ion, V. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Faculty of Physics, University of Bucharest, 077125 Magurele (Romania); Rusen, L.; Filipescu, M. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania); Mustaciosu, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering – IFIN HH, Magurele, Bucharest (Romania); Luculescu, C.; Dinescu, M. [NILPRP, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest (Romania)

    2015-10-15

    Highlights: • Roughness gradients are obtained in one step by applying single laser pulses and sample tilting. • BSA protein and cell dependence behavior onto gradient characteristics was studied. • The degradation of the samples by lysozyme was correlated to its ability to access the textured area. - Abstract: 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.

  11. Film forming properties of silicon nanoparticles on SixNy coated substrates during excimer laser annealing

    Science.gov (United States)

    Caninenberg, M.; Kiesler, D.; Benson, N.; Schmechel, R.

    2017-05-01

    In this article we investigate the film forming properties of excimer laser annealed silicon nanoparticles on non-silicon substrates. In contrast to their film forming properties on oxide free silicon substrates, the nanoparticle thin film tends to dewet and form a porous μ-structure on the silicon nitrite covered glass model substrates considered for our investigation. This is quantified using a SEM study in conjunction with image processing software, in order to evaluate the μ-structure size and inter μ-structure distance in dependence of the laser energy density. To generalize our results, the film forming process is described using a COMSOL Multiphysics ® fluid dynamics model, which solves the Navier Stokes equation for incompressible Newtonian fluids. To account for the porous nanoparticle thin film structure in the simulation, an effective medium approach is used by applying a conservative level set one phase method to our mesh. This effort allows us to predict the Si melt film formation ranging from a porous Si μ-structure to a compact 100% density Si thin film in dependence of the substrate / thin film interaction, as well as the laser energy used for the nanoparticle processing.

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

    Science.gov (United States)

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

    1992-12-01

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

  13. Krypton Gas for High Quality Single Wall Carbon Nanotubes Synthesis by KrF Excimer Laser Ablation

    Directory of Open Access Journals (Sweden)

    Jasim Al-Zanganawee

    2015-01-01

    Full Text Available We report for the first time the production of single wall carbon nanotubes (SWCNTs by KrF excimer laser ablation method under the krypton gas atmosphere. For the ablation experiment 450 mJ energy and 30 Hz repetition rate KrF excimer laser was used, and the target was prepared with the following composition: 0.6% Ni, 0.6% Co, and 98.8% C (atomic percentage. The ablation product was characterized by confocal Raman microspectroscopy, transmission electron microscopy (TEM, scanning electron microscopy (SEM, and thermogravimetric analysis (TGA. The SWCNTs obtained are a mixture of semiconducting and metallic types with narrow diameters distribution of 1.26 to 1.49 nm, are micrometers long, and contain low amount of graphite and amorphous carbon.

  14. Des lasers à excimères pour cristalliser le silicium des écrans plats : pourquoi ? comment ?

    Science.gov (United States)

    Prat, C.

    2003-06-01

    Les contraintes techniques et économiques de la fabrication d'écrans plats à cristaux liquides à matrice active ont suscité de nombreuses études de procédés de cristallisation de couches minces de silicium par laser à excimères, exploitant principalement trois types de phénomènes physiques, dans le but d'obtenir des cristaux micrométriques les plus uniformes possible.

  15. Excimer laser assisted very fast exfoliation and reduction of graphite oxide at room temperature under air ambient for Supercapacitors electrode

    Science.gov (United States)

    Malek Hosseini, S. M. B.; Baizaee, S. M.; Naderi, Hamid Reza; Dare Kordi, Ali

    2018-01-01

    Excimer laser was used for reduction and exfoliation of graphite oxide (GO) at room temperature under air ambient. The prepared excimer laser reduced graphite oxide (XLRGO) is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption (BET method), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption techniques for surface, structural functional groups and band gap analysis. Electrochemical properties are investigated using cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS) and continues cyclic voltammetry (CCV) in 0.5 M Na2SO4 as electrolyte. Electrochemical investigations revealed that XLRGO electrode has enhanced supercapacitive performance including specific capacitance of 299 F/g at a scan rate of 2 mV/s. Furthermore, CCV measurement showed that XLRGO electrode kept 97.8% of its initial capacitance/capacity after 4000 cycles. The obtained results from electrochemical investigations confirm that the reduction of GO by using an excimer laser produces high-quality graphene for supercapacitor applications without the need for additional operations.

  16. Combined Excimer Laser Photoablation and Amniotic Membrane Overlay for Relief of Symptomatic Discomfort in Gelatinous Drop-like Corneal Dystrophy.

    Science.gov (United States)

    Alex, Anne F; Eter, Nicole; Uhlig, Constantin E

    2015-10-01

    To describe the efficacy of combined excimer laser photoablation and amniotic overlay membrane in the relief of symptomatic discomfort in a 17-year-old patient who had gelatinous drop-like corneal dystrophy. The best-corrected visual acuity (BCVA) was measured with Snellen letters. Slit-lamp examination of the ocular surface and anterior chamber was performed at baseline. Results were photodocumented. Excimer laser photoablation was performed and subsequently 2 amniotic membranes were transconjunctivally fixated with 10.0 nylon sutures. Investigations and documentation were performed at baseline, every 2 months in the first year, and then every 6 months. The duration of follow-up was 22 months. At baseline, the BCVA was 20/70 in the right eye and 20/200 in the left eye. The patient reported distinct photophobia. Slit-lamp examination was difficult because of blepharospasm. Although gelatinous drops developed again and the BCVA decreased to 2/200, the patient reported significant relief after both microsurgical treatments and remained comfortable at 20 and 22 months. Excimer laser photocoagulation combined with amniotic membrane overlay does not stop the development of gelatinous drop-like corneal dystrophy but may improve subjective comfort. Such treatment does not hinder subsequent lamellar or penetrating grafts and is helpful in providing the necessary time for preparation of matched keratoplasties.

  17. Microstructures induced by excimer laser surface melting of the SiC{sub p}/Al metal matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Qian, D.S., E-mail: Daishu.qian@postgrad.manchester.ac.uk; Zhong, X.L.; Yan, Y.Z.; Hashimoto, T.; Liu, Z.

    2017-08-01

    Highlights: • Microstructural analysis of the excimer laser-melted SiC{sub p}/AA2124;. • Analytical, FEM, and SPH simulation of the laser-material interaction;. • Mechanism of the formation of the laser-induced microstructure. - Abstract: Laser surface melting (LSM) was carried out on the SiC{sub p}/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm{sup 2}. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

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

    CERN Document Server

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

    2002-01-01

    The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, , and ) 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 centre 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 w...

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

    Science.gov (United States)

    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).

  20. Hydroxyapatite and bioactive glass surfaces for fiber reinforced composite implants via surface ablation by Excimer laser.

    Science.gov (United States)

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

    2017-11-01

    In skeletal reconstructions, composites, such as bisphenol-A-glycidyldimethacrylate resin reinforced with glass fibers, are potentially useful alternatives to metallic implants. Recently, we reported a novel method to prepare bioactive surfaces for these composites. Surface etching by Excimer laser was used to expose bioactive glass granules embedded in the resin. The purpose of this study was to analyze two types of bioactive surfaces created by this technique. The surfaces contained bioactive glass and hydroxyapatite granules. The selected processing parameters were adequate for the creation of the surfaces. However, the use of porous hydroxyapatite prevented the complete exposure the granules. In cell culture, for bioactive glass coatings, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V) while inferior cell proliferation was observed on the surfaces containing hydroxyapatite granules. Scanning electron microscopy revealed osteointegration of implants with both types of surfaces. The technique is suitable for the exposure of solid bioactive glass granules. However, the long-term performance of the surfaces needs further assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Excimer laser phototherapeutic keratectomy for the treatment of clinically presumed fungal keratitis.

    Science.gov (United States)

    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  μ m 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.

  2. Intraoperative videokeratography in penetrating keratoplasty and excimer laser-assisted lamellar keratoplasty for keratoconus.

    Science.gov (United States)

    Spadea, Leopoldo; Fiasca, Arianna; Federici, Simone

    2010-09-01

    To evaluate the usefulness of intraoperative computerized corneal topographic data in excimer laser-assisted lamellar keratoplasty (ELLK) and penetrating keratoplasty (PK). Prospective, comparative, interventional case series. Intra- and postoperative videokeratography (Keratron Scout) evaluation was performed on 30 eyes of 30 consecutive patients affected by keratoconus (16 men and 14 women; mean age 32.63±8.02 years) submitted to ELLK (15 eyes) using 16 interrupted 10-0 nylon stitches or to PK (15 eyes) using a 12-bite 10-0 nylon double-running continuous suture. In the ELLK group, the mean intraoperative keratometric astigmatism was 12.06±4.86 diopters (D), which changed to 5.19±2.51 D after topography-guided intraoperative suture adjustment. In the PK group, intraoperative keratometric astigmatism was 10.18±3.88 D, which changed to 3.49±0.41 D. After 24 months (sutures out), the mean videokeratographic keratometric astigmatism was 3.35±1.96 D in the ELLK group and 3.37±0.92 D in the PK group. The Alpins method of vector analysis showed some significant changes especially in the ELLK group. In keratoplasty surgery, videokeratography is useful for suture adjustment. In the PK group, using a double-running suture technique, the postoperative astigmatism (after all sutures were removed) was similar to the astigmatism measured intraoperatively by videokeratography. Copyright 2010, SLACK Incorporated.

  3. Insight into excimer laser crystallization exploiting ellipsometry: Effect of silicon film precursor

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM sez. Bari, Via Orabona 4, 70125 Bari (Italy)], E-mail: maria.losurdo@ba.imip.cnr.it; Giangregorio, Maria M.; Sacchetti, Alberto; Capezzuto, Pio; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM sez. Bari, Via Orabona 4, 70125 Bari (Italy); Mariucci, Luigi; Fortunato, Guglielmo [IFN-CNR, Via Cineto Romano, 42 - 00156 Rome (Italy)

    2007-07-16

    The optical diagnostic of spectroscopic ellipsometry is shown to be an effective tool to investigate the mechanism of excimer laser crystallization (ELC) of silicon thin films. A detailed spectroscopic ellipsometric investigation of the microstructures of polycrystalline Si films obtained on SiO{sub 2}/Si wafers by ELC of a-Si:H and nc-Si films deposited, respectively, by SiH{sub 4} plasma enhanced chemical vapor deposition (PECVD) and SiF{sub 4}-PECVD is presented. It is shown that ellipsometric spectra of the pseudodielectric function of polysilicon thin films allows to discern the three different ELC regimes of partial melting, super lateral growth and complete melting. Exploiting ellipsometry and atomic force microscopy, it is shown that ELC of nc-Si has very low energy density threshold of 95 mJ/cm{sup 2} for complete melting, and that re-crystallization to large grains of {approx} 2 {mu}m can be achieved by multi-shot irradiation at an energy density as low as 260 mJ/cm{sup 2} when using nc-Si when compared to 340 mJ/cm{sup 2} for the ELC of a-Si films.

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

    Directory of Open Access Journals (Sweden)

    Liang-Mao Li

    2014-01-01

    Full Text Available 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.

  5. [193 excimer laser trepanation in perforating keratoplasty. Report of 70 patients].

    Science.gov (United States)

    Naumann, G O; Seitz, B; Lang, G K; Langenbucher, A; Kus, M M

    1993-10-01

    In penetrating keratoplasty, trephination with the 193 nm excimer laser may help avoid the differences in the deformation of the donor and recipient wound margins which occur with the conventional procedure. By varying the shape of the "open metal mask", other cut configurations can be achieved besides circular. Thus, "vertical tilt" and "horizontal torsion", both potential reasons for persistent long-term astigmatism after PK, may be minimized. Following experimental studies, the authors present the results obtained in their first 70 consecutive patients. 38 women and 32 men were treated (mean age 60.6 years, range 17 to 89 years). Indications were corneal processes without vascularization: Fuchs' dystrophy (n = 32), other stromal dystrophies (n = 5), secondary corneal endothelial decompensation (n = 6), keratoconus (n = 15), nonvascularized corneal scars (n = 4) and miscellaneous (n = 8 ). We used elliptical metal masks with/without orientation teeth and circular masks with four and eight orientation teeth, respectively. The HeNe aiming beam was manually controlled by a micromanipulator ("joystick"). The technical data of the laser were as follows: spot mode, 1.5 x 1.5 mm; repetition rate 30/sec and 25/sec, respectively; pulse energy 15-25 mJ; mean number of pulses 6407 (recipient) and 9150 (donor). With an elliptical outline, wound closure was usually achieved with single sutures. With a circular outline with orientation teeth, wound closure was most commonly achieved with a double running suture. Patients were prospectively documented using modified Erlangen record sheets. Follow-up ranged from 3 months to 3.4 years (mean 11.4 months). With two exceptions, penetration of the anterior chamber with the 193 nm excimer laser was accomplished without deformation of the cut edges. The elliptical outline facilitated fitting of the graft into the recipient wound bed, and the orientation teeth made fitting even easier. Initial intraoperative complications due to

  6. Effect of time sequences in scanning algorithms on the surface temperature during corneal laser surgery with high-repetition-rate excimer laser.

    Science.gov (United States)

    Mrochen, Michael; Schelling, Urs; Wuellner, Christian; Donitzky, Christof

    2009-04-01

    To investigate the influence of temporal and spatial spot sequences on the ocular surface temperature increase during corneal laser surgery with a high-repetition-rate excimer laser. Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland, and WaveLight AG, Erlangen, Germany. An argon-fluoride excimer laser system working at a repetition rate of 1050 Hz was used to photoablate bovine corneas with various myopic, hyperopic, and phototherapeutic ablation profiles. The temporal distribution of ablation profiles was modified by 4 spot sequences: line, circumferential, random, and an optimized scan algorithm. The increase in ocular surface temperature was measured using an infrared camera. The maximum and mean ocular surface temperature increases depended primarily on the spatial and temporal distribution of the spots during photoablation and the amount of refractive correction. The highest temperature increases were with the line and circumferential scan sequences. Significant lower temperature increases were found with the optimized and random scan algorithms. High-repetition-rate excimer laser systems require spot sequences with optimized temporal and spatial spot distribution to minimize the increase in ocular surface temperature. An ocular surface temperature increase will always occur depending on the amount of refractive correction, the type of ablation profile, the radiant exposure, and the repetition rate of the laser system.

  7. Excimer laser-assisted recanalisation of femoral arterial stenosis or occlusion caused by the use of Angio-Seal

    Energy Technology Data Exchange (ETDEWEB)

    Steinkamp, H.J.; Werk, M.; Beck, A.; Teichgraeber, U.; Haufe, M.; Felix, R. [Dept. of Radiology, Humboldt Univ. Berlin (Germany)

    2001-08-01

    The aim of this study was to demonstrate the effect of excimer laser and balloon angioplasty of femoral artery stenosis and occlusion after use of a haemostatic puncture closure device. A haemostatic puncture closure device (Angio-Seal) was used in 6000 patients after diagnostic or therapeutic artery catheterisation. In 34 of those patients symptoms of peripheral artery disease occurred. Sixteen of those 34 cases were transferred to our clinic for excimer laser angioplasty. All 16 patients presented with symptoms of acute peripheral artery disease within 1-14 days: superficial femoral artery (SFA) occlusions (4 cases); superficial femoral artery stenosis (3 cases); high-grade stenosis of the common femoral artery (CFA; 3 cases); high-grade stenosis of CFA; SFA and profund femoral artery (PFA; 3 cases); and occlusions of CFA, SFA and PFA (3 cases). Before any procedure was performed, informed consent was given by the patient, which included the use of the Angio-Seal closure device. Every patient who had to undergo recanalisation procedures gave additional informed consent which especially included the usage of the excimer laser for recanalisation. A measurement of the walking distance, ankle-brachial systolic pressure index (ABI) and diagnostic angiography was performed in 13 cases before and immediate after as well as 3 and 6 months after therapeutic percutaneous transluminal laser angioplasty followed by balloon angioplasty (PTLA/PTA). In 3 patients the risks of PTLA/PTA was considered too high; those patients underwent surgical repair. Angiographic and clinical improvement was achieved in 13 of 13 patients. The mean walking distance increased from 81 to >400 m. The average ankle-brachial systolic pressure index (ABI) increased from 0.47 to 0.84. One patient developed a dissection of the SFA, and in 1 case a peripheral embolisation was seen. The PTLA/PTA technique is a successful therapeutic option for patients with femoral artery occlusion or high-grade stenosis

  8. Effects of excimer laser annealing on low-temperature solution based indium-zinc-oxide thin film transistor fabrication

    Directory of Open Access Journals (Sweden)

    Chao-Nan Chen

    2015-04-01

    Full Text Available A Solution Based Indium-Zinc-Oxide thin-film transistor (TFT with a field-effect mobility of 0.58 cm2/Vs, a threshold voltage of 2.84 V by using pulse laser annealing processes. Indium-zinc-oxide (IZO films with a low process temperature were deposited by sol-gel solution based method and KrF excimer laser annealing (wavelength of 248 nm. Solution based indium-zinc-oxide (IZO films usually needs high temperature about 500 °C post annealing in a oven. KrF excimer laser annealing shows advantages of low temperature process, the less process time deceases to only few seconds was used to replace the high temperature process. IZO thin films suffering laser irradiation still keeps the amorphous film quality by transmission electron microscopy (TEM diffraction pattern analysis. It could be expected this technology to large-area flexible display, in the future.

  9. A comparative study of via drilling and scribing on PEN and PET substrates for flexible electronic applications using excimer and Nd:YAG laser sources

    NARCIS (Netherlands)

    Mandamparambil, R.; Fledderus, H.; Brand, J. van den; Saalmink, M.; Kusters, R.; Podprocky, T.; Steenberge, G. van; Baets, J. de; Dietzel, A.H.

    2009-01-01

    A study on via drilling and channel scribing on PEN and PET substrates for flexible electronic application is discussed in this paper. For the experiments, both KIF excimer laser (248 nm) and frequency tripled Nd:YAG (355 nm) laser are used. Different measurement techniques like optical microscopy,

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

    Science.gov (United States)

    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.

  11. Laser undulator radiation

    CERN Document Server

    Kawamura, Y; Ruschin, S; Tanabé, T; Toyoda, K

    2000-01-01

    Various characteristics such as the number of photons, the wavelength, and the solid angle of the laser undulator radiation have been measured quantitatively. It was performed in the visible wavelength region using the interaction between a high-power pulsed CO sub 2 laser and a high-quality electron beam having an energy of 0.65-0.85 MeV. The experimental results were in good agreement with the theoretical calculations. A criterion to determine the limitation to the number of periods of the laser undulator was also proposed.

  12. Single application on iris localization technology in excimer laser for astigmatism

    Directory of Open Access Journals (Sweden)

    Jun-Hua Hao

    2014-06-01

    Full Text Available AIM:To discuss the single application on iris localization technology in excimer laser for the treatment of astigmatism. METHODS:Totally 203 cases(406 eyesof laser in situ keratomileusis(LASIKin the treatment of compound myopic astigmatism patients were operated from November 2011 to November 2012 in our hospital. They were divided into two groups. One was observation group using iris localization and the other was control group using routine operation. Patients in the observation group of 100 cases(200 eyes, aged 18-43 years old, spherical diopter was -1.25 to -8.75D, astigmatism was -1.0 to -3.25D. In control group, 103 patients(206 eyes, aged 19-44 years old, spherical diopter was -1.75-9.50D, astigmatism was -1.0 to -3.25D. The patients in the observation group before the application of WaveScan aberrometer check for iris image, spherical lens, cylindrical lens and astigmatism axis data operation, only single application of iris location, without using wavefront aberration guided technology, laser cutting patterns for conventional LASIK model, spherical, cylindrical mirror and astigmatism axis data source to preoperative wavefront aberration results. The control group received routine LASIK. It was applicated comprehensive optometry optometry respectively to examine astigmatism and axial, based on the computer analysis during the preoperative, 1wk after the operation, and 6mo. Analysis of using SPSS 17 statistical software, it was independent-sample t test between the two groups of residual astigmatism and astigmatism axis. RESULTS:Postoperative residual astigmatism, the observation group was significantly better than the control group. Astigmatism axial measurement after operation, the observation group was significantly less than that of the control group. Postoperative visual acuity at 6mo, the observation group was better than that of the control group. The difference was statistically significant. CONCLUSION: For patients who cannot

  13. Excimer laser micropatterning of freestanding thermo-responsive hydrogel layers for cells-on-chip applications

    Science.gov (United States)

    Santaniello, Tommaso; Martello, Federico; Tocchio, Alessandro; Gassa, Federico; Webb, Patrick; Milani, Paolo; Lenardi, Cristina

    2012-10-01

    We report a novel reliable and repeatable technologic manufacturing protocol for the realization of micro-patterned freestanding hydrogel layers based on thermo-responsive poly-(N-isopropyl)acrylamide (PNIPAAm), which have potential to be employed as temperature-triggered smart surfaces for cells-on-chip applications. PNIPAAm-based films with controlled mechanical properties and different thicknesses (100-300 µm thickness) were prepared by injection compression moulding at room temperature. A 9 × 9 array of 20 µm diameter through-holes is machined by means of the KrF excimer laser on dry PNIPAAm films which are physically attached to flat polyvinyl chloride (PVC) substrates. Machining parameters, such as fluence and number of shots, are optimized in order to achieve highly resolved features. Micro-structured freestanding films are then easily obtained after hydrogels are detached from PVC by gradually promoting the film swelling in ethanol. In the PNIPAAm water-swollen state, the machined holes’ diameter approaches a slight larger value (30 µm) according to the measured hydrogel swelling ratio. Thermo-responsive behaviour and through-hole tapering characterization are carried out by metrology measurements using an optical inverted and confocal microscope setup, respectively. After the temperature of freestanding films is raised above 32 °C, we observe that the shrinkage of the whole through-hole array occurs, thus reducing the holes’ diameter to less than a half its original size (about 15 µm) as a consequence of the film dehydration. Different holes’ diameters (10 and 30 µm) are also obtained on dry hydrogel employing suitable projection masks, showing similar shrinking behaviour when hydrated and undergone thermo-response tests. Thermo-responsive PNIPAAm-based freestanding layers could then be integrated with other suitable micro-fabricated thermoplastic components in order to preliminary test their feasibility in operating as temperature

  14. Influence of laser beam’s image-plane position on geometry of through-holes in percussion-drilled glass using excimer laser

    Directory of Open Access Journals (Sweden)

    Ales Babnik

    2013-01-01

    Full Text Available We study the influence of a laser beam’s image-plane position relative to the processed surface for the deep-hole, laser-microdrilling of soda-lime glass with an excimer 308-nm laser and mask-projection technique. It is demonstrated that the image-plane position has a significant influence on the hole’s tapering and final depth. Holes with exit diameters up to 10 times smaller than the mask-image diameter are produced in the case of perforation during the appropriate process phase determined by the formation of the plasma plume.

  15. Controllable Change of Photoluminescence Spectra of Silicone Rubber Modified by 193 nm ArF Excimer Laser

    Science.gov (United States)

    Okoshi, Masayuki; Iyono, Minako; Inoue, Narumi

    2009-12-01

    Photoluminescence spectra of silicone rubber ([SiO(CH3)2]n) photochemically modified by a 193 nm ArF excimer laser was found to be controllable. Compared with the modification in air, the photoluminescence spectra could be blueshifted by the modification in vacuum or the additional irradiation of ArF excimer laser in vacuum after the modification in air. To redshift, on the other hand, the additional irradiation of a 157 nm F2 laser in air after the modification in air, the modification in oxygen gas, or the postannealing after the modification in oxygen gas was effective. The blue and redshifts of the photoluminescence were essentially due to the acceleration of reduction and oxidation reactions of silicone rubber, respectively, because the photoluminescence derives its origin from oxygen deficiency centers and peroxy centers of the silica structure in the modified silicone rubber. On the basis of the spectra changes, colorful light-guiding sheets made of silicone rubber under illumination of a 375 nm light-emitting diode were successfully fabricated for cellular phone use.

  16. Corneal lathing using the excimer laser and a computer-controlled positioning system: Part I--Lathing of epikeratoplasty lenticules.

    Science.gov (United States)

    Altmann, J; Grabner, G; Husinsky, W; Mitterer, S; Baumgartner, I; Skorpik, F; Asenbauer, T

    1991-01-01

    Precise lathing of epikeratoplasty lenticules is difficult to achieve with the cryolathe due to unpredictable expansion of the lathing tools and the corneal tissue during the freezing process. In addition, the procedure destroys all viable cells in the transplant thereby possibly contributing to the prolonged period of visual rehabilitation. Non-freezing techniques using the microkeratome or the rotor-trephine, on the other hand, are technically demanding, can cause mechanical damage during cutting or fixation, and, have not given consistently reproducible refractive results. A new system is presented that allows a variable laser ablation of donor corneas into lenticules for aphakic and myopic epikeratoplasty, as well as for lamellar keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is moved, epithelial side down, in a holding device in front of a focused excimer laser beam (ArF, lambda = 193 nm). This photoablation lathing process assures the viability of the stromal cells in the lenticule in close approximation to the treated surface. The user friendly computer software allows the fast and convenient selection of a variety of parameters, such as the diameter of the optical zone, the shape of the wing zone, the refractive power, the central thickness of the lenticule and the overall contour of the transplant. The first laboratory data of lenticules prepared from human corneas with this "Excimer Laser Corneal Shaping System" are presented.

  17. Laser radiation bracket debonding

    Science.gov (United States)

    Dostálová, Tat'jana; Jelínková, Helena; Šulc, Jan; Koranda, Petr; Nemec, Michal; Racek, Jaroslav; Miyagi, Mitsunobu

    2008-02-01

    Ceramic brackets are an aesthetic substitute for conventional stainless steel brackets in orthodontic patients. However, ceramic brackets are more brittle and have higher bond strengths, which can lead to bracket breakage and enamel damage during classical type of debonding. This study examined the possibility of laser radiation ceramic brackets removing as well as the possible damage of a surface structure of hard dental tissue after this procedure. Two types of lasers were used for the experiments - a laser diode LIMO HLU20F400 generating a wavelength of 808 nm with the maximum output power 20W at the end of the fiber (core diameter 400 μm, numerical aperture 0.22). As a second source, a diode-pumped Tm:YAP laser system generating a wavelength of 1.9 μm, with up to 3.8 W maximum output power was chosen. For the investigation, extracted incisors with ceramic brackets were used. In both cases, laser radiation was applied for 0.5 minute at a maximum power of 1 W. Temperature changes of the irradiated tissue was registered by camera Electrophysics PV320. After the interaction experiment, the photo-documentation was prepared by the stereomicroscope Nikon SMZ 2T, Japan. The surface tissue analysis was processed in "low vacuum" (30 Pa) regime without desiccation. This technique was used to record back-scattered electron images. Selecting the appropriate laser, resin, and bracket combination can minimize risks of enamel degradation and make debonding more safe.

  18. Corneal lathing using the excimer laser and a computer-controlled positioning system: Part II--Variable trephination of corneal buttons.

    Science.gov (United States)

    Husinsky, W; Mitterer, S; Altmann, J; Grabner, G; Baumgartner, I; Skorpik, F; Asenbauer, T

    1991-01-01

    A new system is presented that allows a variable trephination of donor corneas for the preparation of corneal buttons used in penetrating keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is removed, epithelial side up, in a fixation device in front of a focused excimer laser beam (ArF, lambda = 193 nm). User friendly computer software allows the surgeon to select a variety of parameters (diameter, shape, angle of trephination) of the corneal graft. Histological and electron microscopical data of human corneas trephined with this "Excimer Laser Corneal Shaping System" are presented.

  19. Update on excimer laser photorefractive keratectomy (PRK) at Cedars-Sinai Medical Center: two-year experience

    Science.gov (United States)

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

    1993-06-01

    Our two year experience with excimer laser photorefractive keratectomy for the correction of myopia on 160 eyes of 128 patients is described. All eyes were treated with a VISX Twenty- Twenty excimer laser, with the following parameters: radiant exposure 160 mJ/cm2, frequency 5 Hz, ablation zone diameter 5.0 to 5.5 mm, and stromal ablation rate 0.18 to 0.33 (mu) /pulse. A suction fixation ring was used in all cases either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from one month (152 eyes) to 24 months (12 eyes). The results are stable between 3 and 24 months with less than 0.25 D change in the mean postoperative spherical equivalents. In eyes with a follow-up of 6 to 24 months, 77% to 100% were 20/40 or better uncorrected, and 84% to 92% were corrected to within +/- 1 D of emmetropia. Further follow-up is needed to assess the long term safety and efficacy of the procedure.

  20. Formation of periodic microswelling structures on silicone rubber surface using ArF excimer laser to realize superhydrophobic property

    Science.gov (United States)

    Nojiri, Hidetoshi; Setyo Pambudi, Wisnu; Okoshi, Masayuki

    2017-07-01

    Periodic microswelling structures were photochemically induced on a silicone rubber surface using a 193 nm ArF excimer laser. Microspheres made of silica glass (SiO2) of 2.5 µm diameter were aligned on the silicone rubber surface during laser irradiation; the laser beam was focused on the silicone surface underneath each microsphere. The height and diameter of the formed microswelling structures were found to be controllable by changing the Ar gas flow rate, single-pulse laser fluence, and laser irradiation time. The chemical bonding of the laser-irradiated sample did not change and thus remained to be a silicone, as analyzed by X-ray photoelectron spectroscopy. As a result, microswelling structures of approximately 1.3 µm height and 1.3 µm diameter were successfully obtained. The contact angles of water on the microstructured silicone were measured to be 150° and larger, clearly indicating superhydrophobicity. The mechanism by which the microswellings form their shape was discussed on the basis of the changes in the focal point and spot size during laser irradiation through the SiO2 microsphere.

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

    Energy Technology Data Exchange (ETDEWEB)

    Van Overschelde, O. [Chimie des Interactions Plasma-Surface, Universite de Mons, 23, Place du Parc, 7000 Mons (Belgium); Delsate, T. [Service de Physique Theorique et Mathematique, Universite de Mons, 6 Avenue du champ de Mars, 7000 Mons (Belgium); Snyders, R. [Chimie des Interactions Plasma-Surface, Universite de Mons, 23, Place du Parc, 7000 Mons (Belgium); Materia Nova Research Center, 1 Avenue Copernic, 7000 Mons (Belgium)

    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.

  2. Improving the ablation efficiency of excimer laser systems with higher repetition rates through enhanced debris removal and optimized spot pattern.

    Science.gov (United States)

    Arba-Mosquera, Samuel; Klinner, Thomas

    2014-03-01

    To evaluate the reasons for the required increased radiant exposure for higher-repetition-rate excimer lasers and determine experimentally possible compensations to achieve equivalent ablation profiles maintaining the same single-pulse energies and radiant exposures for laser repetition rates ranging from 430 to 1000 Hz. Schwind eye-tech-solutions GmbH and Co. KG, Kleinostheim, Germany. Experimental study. Poly(methyl methacrylate) (PMMA) plates were photoablated. The pulse laser energy was maintained during all experiments; the effects of the flow of the debris removal, the shot pattern for the correction, and precooling the PMMA plates were evaluated in terms of achieved ablation versus repetition rate. The mean ablation performance ranged from 88% to 100%; the variability between the profile measurements ranged from 1.4% to 6.2%. Increasing the laser repetition rate from 430 Hz to 1000 Hz reduced the mean ablation performance from 98% to 91% and worsened the variability from 1.9% to 4.3%. Increasing the flow of the debris removal, precooling the PMMA plates to -18°C, and adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the variability. Only adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the mean ablation performance. The ablation performance of higher-repetition-rate excimer lasers on PMMA improved with improvements in the debris removal systems and shot pattern. More powerful debris removal systems and smart shot patterns in terms of thermal response improved the performance of these excimer lasers. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  3. Effects of closed immersion filtered water flow velocity on the ablation threshold of bisphenol A polycarbonate during excimer laser machining

    Energy Technology Data Exchange (ETDEWEB)

    Dowding, Colin, E-mail: c.f.dowding@lboro.ac.uk [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom); Lawrence, Jonathan [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom)

    2010-04-01

    A closed flowing thick film filtered water immersion technique ensures a controlled geometry for both the optical interfaces of the flowing liquid film and allows repeatable control of flow-rate during machining. This has the action of preventing splashing, ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on ablation threshold, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities, that are controllable by modifying the liquid flow-rates. An average decrease in ablation threshold of 7.5% when using turbulent flow velocity regime closed thick film filtered water immersed ablation, compared to ablation using a similar beam in ambient air; however, the use of laminar flow velocities resulted in negligible differences between closed flowing thick film filtered water immersion and ambient air. Plotting the recorded threshold fluence achieved with varying flow velocity showed that an optimum flow velocity of 3.00 m/s existed which yielded a minimum ablation threshold of 112 mJ/cm{sup 2}. This is attributed to the distortion of the ablation plume effected by the flowing immersion fluid changing the ablation mechanism: at laminar flow velocities Bremsstrahlung attenuation decreases etch rate, at excessive flow velocities the plume is completely destroyed, removing the effect of plume etching. Laminar flow velocity regime ablation is limited by slow removal of debris causing a non-linear etch rate over 'n' pulses which is a result of debris produced by one pulse remaining suspended over the feature for the next pulse. The impact of closed thick film filtered water immersed ablation is dependant upon beam fluence: high fluence beams achieved greater etch efficiency at high flow velocities as the effect of Bremsstrahlung attenuation is removed by the action of the fluid on

  4. Species-resolved laser-probing investigations of the hydrodynamics of KrF excimer and copper vapor laser ablation processing of materials

    Science.gov (United States)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Ching, Chi H.; Lindley, R. A.

    1993-06-01

    Hydrodynamic phenomena from KrF excimer laser ablation (10-3-20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

  5. Excimer laser phototherapeutic keratectomy : Indications, results and its role in the Indian scenario

    Directory of Open Access Journals (Sweden)

    Rao Srinivas

    1999-01-01

    Full Text Available PURPOSE: To report indications, technique, and results of excimer phototherapeutic keratectomy (PTK, and describe possible reasons for the small numbers of such procedures performed in a referral institute in India. METHODS: Retrospective review of case records of 10 patients (11 eyes who underwent excimer PTK at our institute between February 1994 and September 1997. RESULTS: Corneal scars were the most common indication for treatment. Best-corrected visual acuity (BCVA improved in 6 eyes (mean: 2 lines of Snellen acuity. All eyes had BCVA > or = 6/12 after treatment. None of the patients experienced loss of BCVA after treatment. Unaided visual acuity improved in 3 eyes and decreased in 2 eyes. Change in spherical equivalent refraction > or = 1 diopter occurred in 77.8% of eyes after treatment. Treating central corneal scars resulted in a significant hyperopic shift in refraction. CONCLUSIONS: Excimer PTK is a safe and effective procedure for the treatment of superficial corneal opacities. Post-treatment ametropia may require further correction with optical aids. Inappropriate referrals, deep corneal scars, and cost of the procedure could have contributed to the small numbers of PTK performed at our institute. Improved understanding of procedural strengths and limitations could lead to increased use of this procedure, with satisfying results in selected patients.

  6. Effects of 308 nanometer excimer laser energy on 316 L stainless-steel stents: implications for laser atherectomy of in-stent restenosis.

    Science.gov (United States)

    Burris, N; Lippincott, R A; Elfe, A; Tcheng, J E; O'Shea, J C; Reiser, C

    2000-11-01

    To determine the effects of the incidental exposure of stents to pulsed 308 nanometer ultraviolet excimer laser energy. Five types of 316 L stainless-steel coronary stents were subjected to two types of study. First, for endurance testing, sixty stents were deployed in 3.0Eth 4.0 mm polymer tubes in three geometries. Up to 1,000 laser pulses were delivered while advancing a 2.0 mm eccentric catheter through the lumen of the stent. These stents were next subjected to 400 million simulated heartbeats and then analyzed for metal etching and fatigue. Second, six additional stents were irradiated with 1,000 pulses underwater and then analyzed for particulates, anions and cations liberated from the stent. Photomicroscopy revealed surface etching on a number of stents. Two stent models exhibited multiple strut fractures at the strut joints in both test samples and controls. In no case was a break observed at the site of laser-stent interaction. Breakage frequency was not significantly different between lazed stents and controls. Lazed stents produced a mean of 14 micrograms of sodium and 4 micrograms of iron more than controls. No excess particulates were detected. Under model conditions typical of clinical use, excimer laser treatment does not alter stainless-steel stent endurance or liberate clinically significant material from the stent.

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

    Energy Technology Data Exchange (ETDEWEB)

    Švanda, Jan; Siegel, Jakub; Švorčík, Vaclav; Lyutakov, Oleksiy, E-mail: lyutakoo@vscht.cz

    2016-05-15

    Highlights: • Combination of bottom-up (BCP separation) and top-down (laser patterning) technologies allows obtaining hierarchical structures. • Surface morphologies were determined by the order of patterning steps (laser modification, annealing, surface reconstruction). • Tuning the order of steps enables the reorientation of BCP domain at large scale, fabrication of hierarchical, hybrid or recessed structures. • The obtained structures can find potential applications in nanotechnology, plasmonics, information storage, sensors and smart surfaces. - Abstract: 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.

  8. Electronic and crystalline structure of Si/SiO 2 interface modified by ArF excimer laser

    Science.gov (United States)

    Cháb, V.; Lukeš, I.; Ondřejček, M.; Jiříček, P.

    The native oxide layers on Si(100) surface were irradiated under UHV conditions by an ArF excimer laser pulses with energy density varied between melting and evaporating thresholds. The resulting changes were studied by LEED, AES and UPS. The increase of the energy density up to evaporation threshold results in the recrystallisation of native oxide layer. The pulses with energy densities just above the evaporation threshold ablate the top layer leaving an ordered and atomicaly clean surface. The observed (1x1) surface reconstruction is probably stabilised by strains introduced during rapid melting and quenching of the topmost layers. The surface electronic structure is dominated by random satisfaction of dangling bonds swearing a well defined surface states observed on (2x1)Si(100) surface.

  9. Synthesis and properties of Ag/ZnO core/shell nanostructures prepared by excimer laser ablation in liquid

    Directory of Open Access Journals (Sweden)

    Yan Zhao

    2015-08-01

    Full Text Available Ag/ZnO core/shell nanostructure was synthesised by a 248-nm KrF excimer pulsed laser ablation in a liquid solution for the first time. It was found that the surface plasma resonance absorption of the Ag/ZnO core/shell nanostructures can be tuned by the thickness of the ZnO shell, which is in agreement with the finite difference in the time domain simulation. Furthermore, the ultraviolet emission spectrum of the Ag/ZnO core/shell nanostructures was stronger and blue-shifted compared with that of pure ZnO nanoparticles. This interesting photoluminescent phenomenon is analysed in detail and a possible explanation is proposed.

  10. ArF excimer laser modulation of TNF-alpha and gelatinase B in NIH 3T3 cells; Modulation de l`expression du TNF-alpha et de la gelatinase B, apres irradiation de fibroblastes NIH 3T3 par un laser a excimeres a 193 NM

    Energy Technology Data Exchange (ETDEWEB)

    Naudy-Vives, C.; Courant, D.; Perot, J.C.; Garcia, J.; Fretier, P.; Court, L.; Dormont, D.

    1995-12-31

    The effects on TNF-alpha and gelatinase B activity in mammalian cells induced by 193 nm argon fluoride excimer laser have been investigated. The data show that a secretion of 92 kDa type IV collagenase and TNF-alpha were increased in cell culture supernatants. Moreover, the 193 nm laser radiation produces a decrease of cell proliferation and an increase of cell activation 8 hours after irradiation. The total protein amount increases with the delivered dose. Same, but less effects were obtained after exposure to a conventional UV lamp at 254 nm. (author). 8 refs.

  11. Efficacy and safety of ab interno excimer laser trabeculotomy in primary open-angle glaucoma: two years of follow-up.

    Science.gov (United States)

    Babighian, Silvia; Rapizzi, Emilio; Galan, Alessandro

    2006-01-01

    Ab interno trabeculotomy was performed using the recently developed XeCl excimer laser in 21 eyes of 21 patients with primary open-angle glaucoma refractory to medical therapy. The patients were followed at the Eye Department of S. Antonio Hospital in Padova, for an average of 25.3 +/- 1.3 months. Intraocular pressure (IOP), visual acuity and ocular complications were evaluated. The laser procedure was quick and relatively easy, with minimal manipulation of tissues; complications were clinically insignificant. At the last follow-up, a marked IOP-lowering effect compared to baseline was observed (from 24.8 +/- 2.0 to 16.9 +/- 2.1 mm Hg; -31.8%, p interno excimer laser trabeculotomy seems effective to decrease IOP, serves to reduce the number of antiglaucoma medications and is relatively safe, proving to be a promising therapeutic option in glaucoma surgery. Copyright 2006 S. Karger AG, Basel.

  12. ArF excimer laser-induced deposition of Ag/C nanocomposite thin films in the presence of n-Hexane

    Energy Technology Data Exchange (ETDEWEB)

    Gondal, Mohammed Ashraf, E-mail: magondal@kfupm.edu.sa [Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Fajgar, Radek [Institute of Chemical Process Fundamentals, 16502 Prague (Czech Republic); Chang, Xiaofeng [Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Institute of Chemical Process Fundamentals, 16502 Prague (Czech Republic); College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China); Shen, Kai [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China); Xu, Qingyu [Department of Physics, Southeast University, Nanjing 211189 (China)

    2014-08-30

    Highlights: • A new excimer laser ablation process was proposed to fabricate Ag/C thin film. • The size of Ag nanoparticles is ranging from 5 to 20 nm. • The ratios of Ag to C can be controlled by adjusting the pressure of n-Hexane. • The graphite-like structure of carbonaceous products was confirmed. - Abstract: Ag/C nanocomposite thin films with different Ag/C molar ratios have been prepared using ArF excimer laser-induced ablation process and silver target under n-Hexane atmosphere. The morphology, crystal structure and composition of as-deposited Ag/C nanocomposite thin films were investigated with high resolution electronic microscopic techniques (including scanning electron microscopy and transmission electron microscopy) and energy-dispersive X-ray spectroscopy, respectively. Laser Raman spectroscopy and Fourier transform infrared spectroscopy techniques were also applied to characterize the final carbonaceous products generated from n-Hexane under laser ablation process. The optical emission of the plume caused by the interaction between excimer laser and silver target in the presence of n-Hexane was studied to understand the possible reaction process. The UV–vis absorption of as-deposited Ag/C thin films, which is attributed to the surface plasmonic excitation, was also investigated in the present work.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Madhushree Bute; Shinde, Shashikant D. [Department of Physics, University of Pune, Pune 411007 (India); Bodas, Dhananjay [Centre for Nanobioscience, Agharkar Research Institute, Agharkar road, Pune 411004 (India); Patil, K.R. [Center for Materials Characterization, National Chemical Laboratories, Pune 411008 (India); Sathe, V.G. [UGC DAE Inter University Consortium, Indore 452017 (India); Adhi, K.P. [Department of Physics, University of Pune, Pune 411007 (India); Gosavi, S.W., E-mail: swg@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411007 (India)

    2014-09-30

    Graphical abstract: - Highlights: • Use of KrF Laser micromachining for Lab-On-Chip applications at lower fluence. • Addition of Benzophenone in PDMS enhances its self development sensitivity. • Benzophenone helps efficient energy transfer for equal density of bond scissioning. • Correlation of chemical composition with laser dose and microstructure. • Microstructures with well defined clean sidewalls. - Abstract: 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/cm{sup 2}. 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 C-O, C=O, Si-O{sub 3} and Si-O{sub 4} bonding at the expense of Si-C and Si-O{sub 2} 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.

  14. Early outcome of high energy Laser (Excimer) facilitated coronary angioplasty ON hARD and complex calcified and balloOn-resistant coronary lesions: LEONARDO Study

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosini, Vittorio; Sorropago, Giovanni; Laurenzano, Eugenio [Montevergine Clinic, Mercogliano (Italy); Golino, Luca, E-mail: lucagolino.jazz@alice.it [Montevergine Clinic, Mercogliano (Italy); Moriggia-Pelascini Hospital, Gravedona, Como (Italy); Casafina, Alfredo; Schiano, Vittorio [Montevergine Clinic, Mercogliano (Italy); Gabrielli, Gabriele [University Hospital Ospedali Riuniti, Ancona (Italy); Ettori, Federica; Chizzola, Giuliano [Spedali Civili University Hospital, Brescia (Italy); Bernardi, Guglielmo; Spedicato, Leonardo [University Hospital S. Maria Misericordia, Udine (Italy); Armigliato, Pietro [Istituto Italiano Ricerche Mediche, Verona (Italy); Spampanato, Carmine [Telethon Institute of Genetics and Medicine (TIGEM), Naples (Italy); Furegato, Martina [Istituto Italiano Ricerche Mediche, Verona (Italy)

    2015-04-15

    Aim: An innovative xenon–chlorine (excimer) pulsed laser catheter (ELCA X80) has been recently used for the treatment of complex coronary lesions, as calcified stenosis, chronic total occlusions and non-compliant plaques. Such complex lesions are difficult to adequately treat with balloon angioplasty and/or intracoronary stenting. The aim of this study was to examine the acute outcome of this approach on a cohort of patients with coronary lesions. Methods and Results: Eighty patients with 100 lesions were enrolled through four centers, and excimer laser coronary angioplasty was performed on 96 lesions (96%). Safety and effectiveness data were compared between patients treated with standard laser therapy and those treated with increased laser therapy. Laser success was obtained in 90 lesions (93.7%), procedural success was reached in 88 lesions (91.7%), and clinical success in was obtained in 87 lesions (90.6%). There was no perforation, major side branch occlusion, spasm, no-reflow phenomenon, dissection nor acute vessel closure. Increased laser parameters were used successfully for 49 resistant lesions without complications. Conclusions: This study suggests that laser-facilitated coronary angioplasty is a simple, safe and effective device for the management of complex coronary lesions. Furthermore, higher laser energy levels delivered by this catheter improved the device performance without increasing complications. - Highlights: • We planned this multicenter study to examine the acute outcome of an innovative xenon–chlorine (excimer) pulsed laser catheter (ELCA X80) for treatment of complex coronary lesions. • We enrolled 80 patients with 100 lesions and performed excimer laser coronary angioplasty in 96 lesions (96%). • Laser success was obtained in 90 lesions (93.7%), procedural success was reached in 88 lesions (91.7%), and clinical success was obtained in 87 lesions (90.6%). • Increased laser parameters were used successfully for 49 resistant

  15. Multifocal Corneal Excimer Femtosecond Laser in situ Keratomileusis following Radial Keratotomy: A Case Report with Six Months of Follow-Up

    Directory of Open Access Journals (Sweden)

    Iraklis Vastardis

    2014-12-01

    Full Text Available We report the case of a 46-year-old female patient who was referred to our clinic (Orasis Eye Clinic, Reinach, Switzerland seeking improvement of her distance and near visual acuity. Radial keratotomy (RK was performed at a younger age on both eyes to correct -5 D myopia. The patient underwent a bilateral same-session multifocal corneal excimer femtosecond laser (Supracor keratomileusis correction. We introduce a new correction approach, possibly suitable for presbyopic patients previously treated with RK, and we present several potential novel advantages such as enhanced near, intermediate vision, and improvement in quality of life. This is the first report of a bilateral excimer laser treatment attempt of presbyopia following RK.

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

    Science.gov (United States)

    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.

  17. Morphological and structural modifications induced in a-Si{sub 1-x} C{sub x}:H films by excimer laser annealing

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [CNISM Unita' di Napoli, Complesso Universitario MSA, Napoli (Italy); Universita di Napoli ' Federico II' , Dipartimento di Scienze Fisiche, Napoli (Italy); Ambrosone, G. [Universita di Napoli ' Federico II' , Dipartimento di Scienze Fisiche, Napoli (Italy); CNR-SPIN, Napoli (Italy); Basa, D.K. [Utkal University, Department of Physics, Bhubaneswar (India); Tresso, E. [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Turin (Italy); Chiodoni, A. [IIT rate at POLITO - Center for Space Human Robotics, Turin (Italy); Pinto, N.; Murri, R. [Universita' di Camerino, Dipartimento di Fisica, Camerino (Italy)

    2010-09-15

    Hydrogenated amorphous silicon carbon films of different carbon content deposited by plasma enhanced chemical vapour deposition on Corning glass and crystalline silicon substrates have been irradiated by an excimer (KrF) laser. The properties of these samples were investigated by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy before and after laser treatment, in order to understand the role of the carbon content as well as the substrate in the structural modifications. It has been demonstrated that the changes induced in the films by the laser treatment are independent of the substrate but depend on the carbon content which facilitates the crystallization process. (orig.)

  18. INDEPENDENT EVALUATION OF THE GAM EX5ALN MINIATURE LINE-NARROWED KRF EXCIMER LASER

    Science.gov (United States)

    2017-06-01

    Bookmark not defined. 2: Ex5ALN KrF laser wavelength study. The laser output was recorded at 248.7 nm relative to the Hg atomic emission at 253.7 nm...Error! Bookmark not defined. 3: Ex5ALN KrF laser pulse width versus accumulated pulses for 14 kV discharge at 100 Hz...Error! Bookmark not defined. 4: Ex5ALN KrF laser timing jitter of laser

  19. Numerical study of threshold intensity dependence on gas pressure in the breakdown of molecular hydrogen induced by excimer laser

    Science.gov (United States)

    Gamal, Yosr E. E.-D.; Nassef, O. Aied

    2017-10-01

    In the present work, a numerical analysis is performed to investigate the threshold intensity dependence on gas pressure in laser spark ignition of the H2 plasma. The analysis considered the experimental measurements that were carried out by Yagi and Huo [Appl. Opt. 35, 3183 (1996)]. In their experiment, H2 in a pressure range of 150-3000 Torr is irradiated by a focused excimer laser source using a 96 cm lens at a wavelength of 248 nm and a pulse duration of 20 ns. The study, based on a modified electron cascade model [K. A. Hamam et al., J. Mod. Phys. 4, 311 (2013)], solves numerically a time-dependent energy equation for the distribution of the electron energy as well as a set of rate equations that describe the change in the formed excited molecule population. This model enabled the determination of the threshold intensity as a function of gas pressure. The validity of the model was tested by comparing the calculated thresholds with the experimentally measured ones. Moreover, the calculation of the electron energy distribution function and its parameters justified the role of the electron gain and loss processes in controlling the value of threshold intensity in relation to the gas pressure. The effect of loss processes on the threshold intensity is also presented.

  20. NC-controlled production of smooth 3D surfaces in brittle materials with 193-nm excimer laser

    Science.gov (United States)

    Toenshoff, Hans K.; Graumann, Christoph; Hesener, Hanno; Rinke, Marcus

    1998-08-01

    Micromachining performed by Excimer Lasers in conjunction with NC-controlled machines offer flexible production possibilities for 3-D-surfaces. Due to the limitations of conventional micromachining technology for brittle transparent materials in the micro range, a new laser machining beam guiding and data handling system was designed and built. The data handling starts with the mathematical description of the surface shape to be machined. The contour can be derived from a mathematical function or individual xyz-data point information from any CAD-program. A pre-processor calculates the nc-data for laser triggering, xyz-motion and the nc-mask control. Each laser pulse leads to a material removal, defined by the illuminated surface on the work piece as well as the energy density. The principal of superposition of pulses allows the creation of the desired contour. The chosen ablation strategy determines the surface roughness and the process speed. To achieve best results, it has to be carefully adjusted for a specific material. This technique does not require prefabricated tools such as semiconductor masks. This is a sufficient method for structuring grooves in ceramics, diamonds or glass as well as aspherical transparent optical surfaces or micro lens arrays. The excellent absorption of 193 nm compared to 248 nm or larger wavelengths leads to damage free structuring of most brittle materials. The optimized surface ablation process requires spot sizes and energy densities on the work piece which can not be realized with a mirror based beam guidance system. To eliminate these restrictions, a new mirror free machining concept with a gas flushed beam guiding system mounted on a granite vibration reduction table with air bearing positioning system was build. This paper describes the potential of 193 nm treatment of 3-D micro surfaces with a process optimized machine and data handling system.

  1. FEM numerical analysis of excimer laser induced modification in alternating multi-layers of amorphous and nano-crystalline silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C., E-mail: jconde@uvigo.es [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Martin, E. [Dpto. Mecanica, Maquinas, Motores Termicos y Fluidos, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Stefanov, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Alpuim, P. [Departamento de Fisica, Universidade do Minho, 4800-058 Guimaraes (Portugal); Chiussi, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer nc-Si:H is a material with growing importance for a large-area of nano-electronic, photovoltaic or biomedical devices. Black-Right-Pointing-Pointer UV-ELA technique causes a rapid heating that provokes the H{sub 2} desorption from the Si surface and bulk material. Black-Right-Pointing-Pointer Next, diffusion of P doped nc-Si films and eventually, for high energy densities would be possible to reach the melting point. Black-Right-Pointing-Pointer These multilayer structures consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) films deposited on SiO{sub 2}. Black-Right-Pointing-Pointer To optimize parameters involved in this processing, FEM numerical analysis of multilayer structures have been performed. Black-Right-Pointing-Pointer The numerical results are compared with exhaustive characterization of the experimental results. - Abstract: UV excimer laser annealing (UV-ELA) is an alternative annealing process that, during the last few years, has gained enormous importance for the CMOS nano-electronic technologies, with the ability to provide films and alloys with electrical and optical properties to fit the desired device performance. The UV-ELA of amorphous (a-) and/or doped nano-crystalline (nc-) silicon films is based on the rapid (nanoseconds) formation of temperature profiles caused by laser radiation that is absorbed in the material and lead to crystallisation, diffusion in solid or even in liquid phase. To achieve the desired temperature profiles and to optimize the parameters involved in the processing of hydrogenated nanocrystalline silicon (nc-Si:H) films with the UV-ELA, a numerical analysis by finite element method (FEM) of a multilayer structure has been performed. The multilayer structures, consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193 nm radiation with 25

  2. LASEK for the correction of hyperopia with mitomycin C using SCHWIND AMARIS excimer laser: one-year follow-up

    Directory of Open Access Journals (Sweden)

    Khosrow Jadidi

    2015-11-01

    Full Text Available AIM: To evaluate the efficacy, safety and predictability of laser-assisted sub-epithelial keratectomy(LASEKfor the correction of hyperopia using the SCHWIND AMARIS platform.METHODS: This retrospective single-surgeon study includes 66 eyes of 33 patients with hyperopia who underwent LASEK with mitomycin C(MMC. The median age of patients was 35.42±1.12y(ranging 18 to 56y. In each patient LASEK was performed using SCHWIND AMARIS excimer laser. Postoperatively clinical outcomes were evaluated in terms of predictability, safety, efficacy, subjective and objective refractions, uncorrected visual acuity(UCVA, best spectacle-corrected visual acuity(BSCVAand adverse events. RESULTS: The mean baseline refraction was 3.2±1.6 diopters(D(ranging 0 to 7 D. The mean pre-operative and postoperative spherical equivalent(SEwere 2.34±1.76(ranging -1.25 to 7 Dand 0.30±0.84(ranging -0.2 to 0.8 Drespectively(P=0.001. The mean hyperopia was 0.63±0.84 D(ranging -1.75 to 2.76 D6 to 12mo postoperatively. Likewise, the mean astigmatism was 0.68±0.43 D(range 0 to 2 Dwith 51(77.3%and 15(22.7%eyes within ±1 and ±0.50 D respectively. The safety index and efficacy index were 1.08 and 1.6 respectively.CONCLUSION:LASEK using SCHWIND AMARIS with MMC yields good visual and refractive results for hyperopia. Moreover, there were no serious complications.

  3. Chitosan- and polypropylene-oriented surface modification using excimer laser and their biocompatibility study.

    Science.gov (United States)

    Khaledian, Mohammad; Jiroudhashemi, Faeze; Biazar, Esmaeil

    2017-02-01

    Surface modification of medical polymers is carried out to improve biocompatibility. In this study, conventional polymers (chitosan and polypropylene) were modified to laser at different features (oriented and non-oriented) to create a vast range of physicochemical characteristics on the surface of polymers and investigate their effects on biocompatibility of treated surfaces. Atomic force microscope (AFM) was applied to study the morphology of treated samples in comparison with those of the untreated PS. Contact angle analyses were used to evaluate the wettability and surface energy of the treated films. AFM studies showed that after laser treatment, some distinctive nanostructures are created on the surface of polymers. The data from contact angle measurements demonstrated that laser irradiation created surfaces with a vast range of properties in the wettability point of view. The cellular results revealed that after surface modification by laser irradiation, biocompatibility of polymeric films, especially oriented films was enhanced.

  4. H and Au diffusion in high mobility a-InGaZnO thin-film transistors via low temperature KrF excimer laser annealing

    Science.gov (United States)

    Bermundo, Juan Paolo S.; Ishikawa, Yasuaki; Fujii, Mami N.; Ikenoue, Hiroshi; Uraoka, Yukiharu

    2017-03-01

    We report the fabrication of high mobility amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) irradiated by a single shot of a 248 nm KrF excimer laser. Very high mobilities (μ) of up to 43.5 cm2/V s were obtained after the low temperature excimer laser annealing (ELA) process. ELA induces high temperatures primarily in the upper layers and maintains very low temperatures of less than 50 °C in the substrate region. Scanning Transmission Electron micrographs show no laser induced damage and clear interfaces after the laser irradiation. In addition, several characterization studies were performed to determine the μ improvement mechanism. The analysis of Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy suggests incorporation of H mainly from the hybrid passivation layer into the channel. Moreover, Energy-dispersive X-ray Spectroscopy results show that Au diffused into the channel after ELA. Both KrF ELA-induced H and Au diffusion contributed to the higher μ. These results demonstrate that ELA can greatly enhance the electrical properties of a-IGZO TFTs for promising applications in large area, transparent, and flexible electronics.

  5. Mitomycin-C in corneal surface excimer laser ablation techniques: a report by the American Academy of Ophthalmology.

    Science.gov (United States)

    Majmudar, Parag A; Schallhorn, Steven C; Cason, John B; Donaldson, Kendall E; Kymionis, George D; Shtein, Roni M; Verity, Steven M; Farjo, Ayad A

    2015-06-01

    To review the published literature assessing the efficacy and safety of mitomycin-C (MMC) as an adjunctive treatment in corneal surface excimer laser ablation procedures. Literature searches of the PubMed and Cochrane Library databases were last conducted on August 19, 2014, without language or date limitations. The searches retrieved a total of 239 references. Of these, members of the Ophthalmic Technology Assessment Committee Refractive Management/Intervention Panel selected 26 articles that were considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Ten studies were rated as level I evidence, 5 studies were rated as level II evidence, and the remaining 11 studies were rated as level III evidence. The majority of the articles surveyed in this report support the role of MMC as an adjunctive treatment in surface ablation procedures. When MMC is applied in the appropriate concentration and confined to the central cornea, the incidence of post-surface ablation haze is decreased. Although a minority of studies that evaluated endothelial cell density (ECD) reported an MMC-related decrease in ECD, no clinical adverse outcomes were reported. Over the past 15 years, the use of MMC during surgery in surface ablation has become widespread. There is good evidence of the effectiveness of MMC when used intraoperatively as prophylaxis against haze in higher myopic ablations. Although there are reports of decreased endothelial counts after the administration of MMC during surgery, the clinical significance of this finding remains uncertain, because no adverse outcomes were reported with as much as 5 years of follow-up. Optimal dosage, effectiveness as prophylaxis in lower myopic and hyperopic ablations, and long-term safety, particularly in eyes with reduced corneal endothelial cell counts from prior intraocular surgery, have yet to be established. Copyright © 2015 American Academy of

  6. Laser in situ keratomileusis with a scanning excimer laser for the correction of low to moderate myopia with and without astigmatism.

    Science.gov (United States)

    Balazsi, G; Mullie, M; Lasswell, L; Lee, P A; Duh, Y J

    2001-12-01

    To evaluate the safety and effectiveness of and patient satisfaction with laser in situ keratomileusis (LASIK) performed with a scanning excimer laser by experienced surgeons to correct low and moderate levels of myopia and astigmatism. Clinique Laservue, Montreal, Quebec, Canada. A consecutive series of 125 patients (236 eyes) with myopia of -0.5 to -7.0 diopters (D) and cylinder less than 2.5 D were enrolled in this single-center prospective clinical trial. The patients were treated with LASIK and followed for 6 months. The System-ALK Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical) with a 180 microm thickness plate and the Technolas 217 excimer laser (Bausch & Lomb Surgical) with PlanoScan software for the stromal ablation were used in all procedures. Since this version of PlanoScan tended to undercorrect, a mean of 14.7% was added to the standard nomogram. Patient satisfaction was assessed by questionnaires administered preoperatively and 1 and 6 months postoperatively. Retreatments for enhancement were not performed during the 6-month follow-up. Six months after LASIK (86.4% follow-up), the mean postoperative manifest spherical equivalent was +0.02 D +/- 0.64 (SD) compared with a preoperative mean of -4.01 +/- 1.59 D. The uncorrected visual acuity was 20/40 or better in 94.6% of eyes and 20/20 or better in 81.9%. A total of 91.2% were within +/-1.0 D of emmetropia and 73.0% were within +/-0.5 D. Only 2 eyes were overcorrected by >1.0 D. Of the eyes with astigmatic myopia, 86.8% were within +/-1.0 D of the intended cylinder correction (by vector analysis) and 73.0% were within +/-0.5 D. The refractions were generally stable after 1 month, and the change in refraction between postoperative examinations was within +/-0.5 D in 88.0% of eyes. A 1-line decrease in best spectacle-corrected visual acuity was seen in 11.3% of eyes, and no eye lost more than 1 line. An increase of 1 or 2 lines was seen in 45.1%. No intraoperative problems occurred, and

  7. Biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery: is there a difference between advanced surface ablation and sub-Bowman's keratomileusis?

    Science.gov (United States)

    Dawson, Daniel G; Grossniklaus, Hans E; McCarey, Bernard E; Edelhauser, Henry F

    2008-01-01

    To describe the biomechanical and wound healing characteristics of corneas after excimer laser keratorefractive surgery. Histologic, ultrastructural, and cohesive tensile strength evaluations were performed on 25 normal human corneal specimens, 206 uncomplicated LASIK specimens, 17 uncomplicated sub-Bowman's keratomileusis (SBK) specimens, 4 uncomplicated photorefractive keratectomy (PRK) specimens, 2 uncomplicated advanced surface ablation (ASA) specimens, 5 keratoconus specimens, 12 postoperative LASIK ectasia specimens, and 1 postoperative PRK ectasia specimen and compared to previously published studies. Histologic and ultrastructural studies of normal corneas showed significant differences in the direction of collagen fibrils and/or the degree of lamellar interweaving in Bowman's layer, the anterior third of the corneal stroma, the posterior two-thirds of the corneal stroma, and Descemet's membrane. Cohesive tensile strength testing directly supported these morphologic findings as the stronger, more rigid regions of the cornea were located anteriorly and peripherally. This suggests that PRK and ASA, and secondarily SBK, should be biomechanically safer than conventional LASIK with regard to risk for causing keratectasia after surgery. Because adult human corneal stromal wounds heal slowly and incompletely, all excimer laser keratorefractive surgical techniques still have some distinct disadvantages due to inadequate reparative wound healing. Despite reducing some of the risk for corneal haze compared to conventional PRK, ASA cases still can develop corneal haze or breakthrough haze from the hypercellular fibrotic stromal scarring. In contrast, similar to conventional LASIK, SBK still has the short- and long-term potential for interface wound complications from the hypocellular primitive stromal scar. Ophthalmic pathology and basic science research show that SBK and ASA are improvements in excimer laser keratorefractive surgery compared to conventional LASIK or

  8. Comparison of boron diffusion in silicon during shallow p{sup +}/n junction formation by non-melt excimer and green laser annealing

    Energy Technology Data Exchange (ETDEWEB)

    Aid, Siti Rahmah; Matsumoto, Satoru [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Fuse, Genshu [SEN Corporation, SBS Tower 9F, 4-10-1 Yoga, Setagaya-ku, Tokyo 158-0097 (Japan); Sakuragi, Susumu [Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka, Kanagawa 237-8555 (Japan)

    2011-12-15

    The combination of Ge pre-amorphization implantation, low-energy boron implantation, and non-melt laser annealing is a promising method for forming ultrashallow p{sup +}/n junctions in silicon. In this study, shallow p{sup +}/n junctions were formed by non-melt annealing implanted samples using a green laser (visible laser). The dopant diffusion, activation, and recrystallization of an amorphous silicon layer were compared with those obtained in our previous study in which non-melt annealing was performed using a KrF excimer laser (UV laser). The experimental results reveal that only slight diffusion of boron in the tail region occurred in green-laser-annealed samples. In contrast, remarkable boron diffusion occurred in KrF-laser-annealed samples for very short annealing times. Recrystallization of the amorphous silicon layer was slower in green-laser-annealed samples than in KrF-laser-annealed samples. We consider the penetration depth and the pulse duration are important factors that may affect boron diffusion. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Waddell, Emanuel A. [University of Alabama in Huntsville, Huntsville, AL (United States)], E-mail: ewaddell@chemistry.uah.edu; Shreeves, Stephen [University of Alabama in Huntsville, Huntsville, AL (United States); Carrell, Holly; Perry, Christopher [Oakwood College, Huntsville, AL (United States); Reid, Branden A. [Morgan State University, Baltimore, MD (United States); McKee, James [University of Alabama in Birmingham, Birmingham, AL (United States)

    2008-06-30

    The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO{sub x} (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.

  10. Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy

    Science.gov (United States)

    Waddell, Emanuel A.; Shreeves, Stephen; Carrell, Holly; Perry, Christopher; Reid, Branden A.; McKee, James

    2008-06-01

    The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO x (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.

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

    Science.gov (United States)

    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.

  12. Fabrication of functional fibronectin patterns by nanosecond excimer laser direct write for tissue engineering applications.

    Science.gov (United States)

    Grigorescu, S; Hindié, M; Axente, E; Carreiras, F; Anselme, K; Werckmann, J; Mihailescu, I N; Gallet, O

    2013-07-01

    Laser direct write techniques represent a prospective alternative for engineering a new generation of hybrid biomaterials via the creation of patterns consisting of biological proteins onto practically any type of substrate. In this paper we report on the characterization of fibronectin features obtained onto titanium substrates by UV nanosecond laser transfer. Fourier-transform infrared spectroscopy measurements evidenced no modification in the secondary structure of the post-transferred protein. The molecular weight of the transferred protein was identical to the initial fibronectin, no fragment bands being found in the transferred protein's Western blot migration profile. The presence of the cell-binding domain sequence and the mannose groups within the transferred molecules was revealed by anti-fibronectin monoclonal antibody immunolabelling and FITC-Concanavalin-A staining, respectively. The in vitro tests performed with MC3T3-E1 osteoblast-like cells and Swiss-3T3 fibroblasts showed that the cells' morphology and spreading were strongly influenced by the presence of the fibronectin spots.

  13. FEM for modelling 193 nm excimer laser treatment of SiO{sub 2}/Si/Si{sub (1-x)}Ge{sub x} heterostructures on SOI substrates

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C.; Chiussi, S.; Gontad, F.; Gonzalez, P. [Dpto. Fisica Aplicada, E.T.S.I.I. University of Vigo, Campus Universitario, Rua Maxwell s/n, 36310 Vigo (Spain); Martin, E. [Dpto. de Mecanica, Maquinas, Motores Termicos y Fluidos, E.T.S.I.I. University of Vigo, Campus Universitario, Rua Maxwell s/n, 36310 Vigo (Spain)

    2011-03-15

    Research on epitaxial crystalline silicon (c-Si) and silicon-germanium (Si{sub 1-x}Ge{sub x}) alloys growth and annealing for microelectronic purposes, such as Micro- or Nano-Electro-Mechanical Systems (MEMS or NEMS) and Silicon-On-Nothing (SON) devices is continuously in progress. Laser assisted annealing techniques using commercial ArF Excimer Laser sources are based on ultra-rapid heating and cooling cycles induced by the 193 nm pulses of 20 ns, which are absorbed in the near surface region of the heterostructures. During and after the absorption of these laser pulses, complex physical processes appear that strongly depend on sample structure and applied laser pulse energy densities. The control of the experimental parameters is therefore a key task for obtaining high quality alloys. The Finite ElementsMethod (FEM) is a powerful tool for the optimization of such treatments, because it provides the spatial and temporal temperature fields that are produced by the laser pulses. In this work, we have used a FEM commercial software, to predict the temperatures gradients induced by ArF excimer laser over a wide energy densities range, 0.1<{phi}<0.4 J/cm{sup 2}, on different SiO{sub 2}/Si/Si{sub (1-x)}Ge{sub (x)} thin films deposited on SOI substrate. These numerical results allow us to predict the threshold energies needed to reach the melting point (MP) of the Si and SiGe alloy without oxidation of the thin films system. Therefore, it is possible to optimize the conditions to achieve high quality epitaxy films. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. XeCl excimer laser-induced autofluorescence spectroscopy for human cerebral tumor diagnosis: preliminary study

    Science.gov (United States)

    Avrillier, Sigrid; Hor, Frederic; Desgeorges, Michel; Ettori, Dominique; Sitbon, Jean R.

    1993-09-01

    Three-hundred-eight nm laser-induced autofluorescence spectra of the normal human brain, astrocytoma grade IV and glioblastoma grade IV specimens, have been recorded in vitro two hours after surgical resection. Typical fluorescence spectra for normal (N) and malignant (M) tissue show 4 maxima at about 352, 362, 383, and 460 nm. These spectra are analyzed in detail. Subtle differences in normalized spectra of N and M tissues appear to be large enough for diagnosis. Several criteria such as maxima and minima absolute intensity and intensity ratios at typical wavelengths are computed and used to classify the tissue. This preliminary study shows that fluorescence spectroscopy with 308 nm UV excitation could be a valid technique for discriminating tumor types. However, it should be noted that these measurements are made in vitro. Living tissues may have different spectral characteristics, therefore future in vivo investigations must be performed.

  15. Low temperature high-mobility InZnO thin-film transistors fabricated by excimer laser annealing

    NARCIS (Netherlands)

    Fujii, M.; Ishikawa, Y.; Ishihara, R.; Van der Cingel, J.; Mofrad, M.R.T.; Horita, M.; Uraoka, Y.

    In this study, we successfully achieved a relatively high field-effect mobility of 37.7?cm2/Vs in an InZnO thin-film transistor (TFT) fabricated by excimer layer annealing (ELA). The ELA process allowed us to fabricate such a high-performance InZnO TFT at the substrate temperature less than 50?°C

  16. Low temperature high-mobility InZnO thin-film transistors fabricated by excimer laser annealing

    NARCIS (Netherlands)

    Fujii, M.; Ishikawa, Y.; Ishihara, R.; Van der Cingel, J.; Mofrad, M.R.T.; Horita, M.; Uraoka, Y.

    2013-01-01

    In this study, we successfully achieved a relatively high field-effect mobility of 37.7?cm2/Vs in an InZnO thin-film transistor (TFT) fabricated by excimer layer annealing (ELA). The ELA process allowed us to fabricate such a high-performance InZnO TFT at the substrate temperature less than 50?°C

  17. Long-term efficacy of excimer laser in situ keratomileusis in the management of children with high anisometropic amblyopia.

    Science.gov (United States)

    Lin, Xiao-Ming; Yan, Xiao-He; Wang, Zheng; Yang, Bin; Chen, Qi-Wen; Su, Jin-Ai; Ye, Xue-Lian

    2009-04-05

    Children with anisometropic amblyopia are often noncompliant with traditional treatment including spectacules and contact lenses. This study was to evaluate the long-term efficacy of excimer laser in situ keratomileusis (LASIK) for children with high anisometropic amblyopia. A retrospective analysis of 24 children with high unilateral anisometropic amblyopia, who underwent LASIK during the period between August 2000 and September 2005 in our hospital, was conducted. The mean age of these children was (7.4 +/- 1.9) years (range 5 - 14 years) and the mean follow-up period was (33.3 +/- 14.2) months (range 18.5 - 74.2 months). After LASIK, visual acuity, refraction and far or near stereoacuity were analyzed. Near stereoacuity was measured by the random-dot butterfly stereogram and the pre-school random-dot stereogram, while far stereoacuity was measured by the synoptophore with Yan's random-dot stereogram. Mean preoperative uncorrected visual acuity was 0.06 +/- 0.05, while mean postoperative uncorrected visual acuity was elevated to 0.43 +/- 0.33. Mean preoperative best-corrected visual acuity was 0.26 +/- 0.22, while mean postoperative best-corrected visual acuity was elevated to 0.67 +/- 0.40. For patients with myopic anisometropia, preoperative mean spherical equivalent refraction was (-8.01 +/- 2.70) D while postoperative value significantly reduced to (-1.32 +/- 2.47) D. For patients with hyperopic anisometropia, preoperative mean spherical equivalent refraction was (+7.35 +/- 1.55) D while postoperative value significantly reduced to (+3.30 +/- 0.86) D. These results demonstrated that there was statistical difference in these parameters between preoperative and postoperative tests. At the last follow-up, 20 patients had near stereoacuity, and the mean near stereoacuities measured by the random-dot butterfly stereogram and the preschool random-dot stereogram were (149.00 +/- 152.93)'' and (201.05 +/- 235.94)'', respectively. In contrast, 11 patients had far

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

    Directory of Open Access Journals (Sweden)

    Kaevalin Lekhanont

    Full Text Available 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.

  19. Topography-guided hyperopic and hyperopic astigmatism femtosecond laser-assisted LASIK: long-term experience with the 400 Hz eye-Q excimer platform

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2012-06-01

    Full Text Available Anastasios John KanellopoulosDepartment of Ophthalmology, New York University Medical School, New York, NY, and LaserVision.gr Eye Institute, Athens, GreeceBackground: The purpose of this study was to evaluate the safety and efficacy of topography-guided ablation using the WaveLight 400 Hz excimer laser in laser-assisted in situ keratomileusis (LASIK for hyperopia and/or hyperopic astigmatism.Methods: We prospectively evaluated 208 consecutive LASIK cases for hyperopia with or without astigmatism using the topography-guided platform of the 400 Hz Eye-Q excimer system. The mean preoperative sphere value was +3.04 ± 1.75 (range 0.75–7.25 diopters (D and the mean cylinder value was –1.24 ± 1.41 (–4.75–0 D. Flaps were created either with Intralase FS60 (AMO, Irvine, CA or FS200 (Alcon, Fort Worth, TX femtosecond lasers. Parameters evaluated included age, preoperative and postoperative refractive error, uncorrected distance visual acuity, corrected distance visual acuity, flap diameter and thickness, topographic changes, higher order aberration changes, and low contrast sensitivity. These measurements were repeated postoperatively at regular intervals for at least 24 months.Results: Two hundred and two eyes were available for follow-up at 24 months. Uncorrected distance visual acuity improved from 5.5/10 to 9.2/10. At 24 (8–37 months, 75.5% of the eyes were in the ±0.50 D range and 94.4% were in the ±1.00 D range of the refractive goal. Postoperatively, the mean sphere value was –0.39 ± 0.3 and the cylinder value was –0.35 ± 0.25. Topographic evidence showed that ablation was made in the visual axis and not in the center of the cornea, thus correlating with the angle kappa. No significant complications were encountered in this small group of patients.Conclusion: Hyperopic LASIK utilizing the topography-guided platform of the 400 Hz Eye-Q Allegretto excimer and a femtosecond laser flap appears to be safe and effective for

  20. Formation of densely populated SiOx microtree-like structures on the Si (100) surface using excimer laser irradiation in air

    Science.gov (United States)

    Yang, De-Quan; Sacher, Edward; Meunier, Michel

    2004-10-01

    SiOx microforest-like structures have been produced on Si (100) surfaces by pulsed excimer laser irradiation in air. Scanning electron microscopic observations have indicated these structures, which are composed of aggregated nanoparticles, to be 1-5 μm in diameter and 10-20 μm high, and to have the appearance of trees. XPS analysis has shown them to be composed of a-SiOx (1laser irradiation, our microforest-like trees have many sharp nanoscale branches, which may require lower emission voltages in application such as field-emission sources in plasma displays.

  1. Excimer Laser Research

    Science.gov (United States)

    1976-10-01

    ORGANIZATION N ATTETSTTF»UUHLJJ* Avco Everett Research Laboratory, Inc. 2385 Revere Beach Parkway Everett, Massachusetts 02149 REPORT...apparently enhanced by a large reactive c -oss section for producing excited species by chemica ’ reactions of the type Xe« I F,-XeF* • F. (1

  2. Assessment of expressions of heat shock protein (HSP 72) and apoptosis after ArF excimer laser ablation of the cornea.

    Science.gov (United States)

    Ishihara, Miya; Sato, Masato; Sato, Shunichi; Arai, Tsunenori; Obara, Minoru; Kikuchi, Makoto

    2004-01-01

    We immunohistochemically studied expressions of inducible heat shock protein 70 (HSP 72) and apoptosis of corneas ablated with an ArF excimer laser. The temperature of corneal surfaces and laser-induced optical emission spectra were measured in real time as direct physical parameters related to the ablation mechanism. To the best of the authors' knowledge, there have been no experimental studies regarding the influence of physical parameters directly related to the ablation mechanism on corneal reactions at the cell level after laser ablation. The expression of HSP 72 was mainly localized in the regenerative epithelium, which was confirmed to be caused by laser ablation. The HSP 72 positive cell ratios had a correlation with thermal dose, which was derived from the measured time courses of temperature. Expressions of both HSP 72 and apoptosis depended on the thermal dose and elapsed time after ablation. HSP 72 and apoptosis could be seen up to a few hundred micrometers into the stroma, only at a fluence with an optical breakdown emission. This could have been caused by shock waves induced by the optical breakdown. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

  3. Electromagnetic radiation from a laser wakefield accelerator

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.

    2008-01-01

    Coherent and incoherent electromagnetic radiation emitted from a laser wakefield accelerator is calculated based on Lienard-Wiechert potentials. It is found that at wavelengths longer than the bunch length, the radiation is coherent. The coherent radiation, which typically lies in the infrared

  4. Interaction of power pulses of laser radiation with glasses containing implanted metal nanoparticles

    CERN Document Server

    Stepanov, A L; Hole, D E; Bukharaev, A A

    2001-01-01

    The sodium-calcium silicate glasses, implanted by the Ag sup + ions with the energy of 60 keV and the dose of 7 x 10 sup 1 sup 6 cm sup - sup 2 by the ion current flux density of 10 mu A/cm sup 2 , are studied. The ion implantation makes it possible to synthesize in the near-the-surface glass area the composite layer, including the silver nanoparticles. The effect of the powerful pulse excimer laser on the obtained composite layer is investigated. It is established that the laser radiation leads to decrease in the silver nanoparticles size in the implanted layer. However nonuniform distribution of particles by size remains though not so wide as before the irradiation. The experimental results are explained by the effect of glass and metallic particles melting in the nanosecond period of time

  5. O impacto da cirurgia de ceratectomia fotorrefrativa (PRK e ceratomileuse assistida por excimer laser in situ (LASIK na qualidade visual e de vida em pacientes com ametropias The impact of photorefractive excimer laser keratectomy (PRK and laser in situ keratomileusis (LASIK on visual quality and life in patients with ametropias

    Directory of Open Access Journals (Sweden)

    Ricardo Belfort

    2008-02-01

    Full Text Available OBJETIVO: Avaliar a qualidade de vida e de visão e o estresse de pacientes portadores de ametropias submetidos a procedimentos cirúrgicos. MÉTODOS: Estudo longitudinal observacional em que foram estudados 100 pacientes; 54 usuários de óculos, 21 usuários de lentes de contato interessados no procedimento cirúrgico e 25 controles usuários de óculos ou lentes de contato, mas que não desejavam ser operados no período de um ano. Os questionários aplicados foram o National Eye Institute Visual Function Questionnaire (NEI-VFQ-25 de qualidade de vida e o Self Reporting Questionnaire - SRQ-20 para avaliação da saúde mental. Os pacientes que se submeteram à cirurgia responderam aos questionários aplicados por uma observadora antes da mesma, três, seis e doze meses após a intervenção. O grupo controle respondeu de forma auto-aplicada no início do estudo, seis e doze meses após a primeira avaliação. RESULTADOS: No grupo da cirugia dos 54 pacientes que usavam óculos 39 fizeram cirurgia de ceratectomia fotorrefrativa por excimer laser(PRK e 15 fizeram ceratomileuse assistida por excimer laserin situ (LASIK e dos 21 que usavam lentes de contato 12 fizeram cirurgia de ceratectomia fotorrefrativa e nove fizeram ceratomileuse assistida por excimer laser in situ (LASIK. O grupo controle esteve estável durante os 12 meses em relação aos instrumentos aplicados. Três meses após a cirurgia o grupo da cirurgia apresentou melhora significante da qualidade de vida e de visão em relação ao pré-operatório independentemente do tipo de cirurgia realizada. Um ano após a cirurgia os índices de qualidade de vida e de saúde mental, foram semelhantes aos do grupo controle. O Self Reporting Questionnaire - SRQ 20 mostrou diminuição significante do índice de sintomas a partir dos três meses de pós-operatório. CONCLUSÃO: A qualidade de visão e de vida dos pacientes submetidos à cirurgia de correção de ametropia mudou

  6. Experience in using the excimer laser-assisted nonocclusive anastomosis nonocclusive bypass technique for high-flow revascularization: Mannheim-Helsinki series of 64 patients.

    Science.gov (United States)

    Vajkoczy, Peter; Korja, Miikka; Czabanka, Marcus; Schneider, Ulf C; Reinert, Michael; Lehecka, Martin; Schmiedek, Peter; Hernesniemi, Juha; Kivipelto, Leena

    2012-01-01

    The excimer laser-assisted nonocclusive anastomosis (ELANA) technique enables large-caliber bypass revascularization without temporary occlusion of the parent artery. To present the surgical experience of 2 bypass centers using ELANA in the treatment of complex intracranial lesions. Between July 2002 and December 2007, 64 consecutive patients (37 in Germany and 27 in Finland) were selected for high-flow bypass surgery with ELANA. Modified Rankin Scale, a bypass success rate, and the success rate of the laser arteriotomy were assessed. In 66 surgeries for 64 intent-to-treat patients, 58 ELANA procedures were completed successfully. A favorable outcome (postoperative modified Rankin Scale score less than or equal to preoperative modified Rankin Scale) at 3 months was achieved in 43 of 56 patients (77%) with anterior circulation lesions (37 of the 43 patients had aneurysms, 4 had ischemia, and 2 received a bypass before tumor removal) and only in 2 of 8 patients (25%) with posterior circulation aneurysms. Perioperative (< 7 days) mortality for anterior and posterior circulation aneurysms was 6% and 50%, respectively. At the 3-month follow-up, 12% and 63% of patients with anterior and posterior circulation aneurysms, respectively, were dead. The success rate of the laser arteriotomy was 70%. Another 14% were retrieved manually after a nearly complete laser arteriotomy. The ELANA procedure requires a meticulous and careful operative technique. Morbidity and especially mortality rates, usually unrelated to ELANA, are comparable to those of contemporary series of conventional high-flow revascularization operations. This underscores the overall complexity of treating neurovascular pathologies by high-flow bypasses.

  7. High-fidelity modelling of an exciplex pumped alkali laser with radiative transport

    Energy Technology Data Exchange (ETDEWEB)

    Palla, Andrew D; Carroll, David L; Verdeyen, Joseph T [CU Aerospace, Champaign, IL 61820 (United States); Heaven, Michael C, E-mail: apalla@cuaerospace.com [Department of Chemistry, Emory University, Atlanta, GA 30322 (United States)

    2011-07-14

    The exciplex-pumped alkali laser (XPAL) system has been demonstrated in mixtures of Cs vapour, Ar, and ethane by pumping Cs-Ar atomic collision pairs and subsequent dissociation of diatomic, electronically excited CsAr molecules (exciplexes or excimers). Because of the addition of atomic collision pairs and exciplex states, modelling of the XPAL system is far more complicated than the modelling of the classic diode-pumped alkali laser (DPAL). In this paper, we discuss BLAZE-V time-dependent multi-dimensional modelling of this new laser system including radiative transport and parasitic loss effects. A two-dimensional, time-dependent baseline simulation of a pulsed XPAL is presented and compared to data. Good agreement is achieved on a laser pulse full width at half-maximum and laser pulse rise time. Parametric simulations of pulsed XPAL system configurations similar to that of the baseline case, given both four- and five-level laser operation, are presented in which good agreement is obtained with outcoupled laser energy as a function of absorbed pump energy data. The potential impact of parasitic losses on modelled system configurations is discussed.

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

    Science.gov (United States)

    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

  9. High-performance p-channel thin-film transistors with lightly doped n-type excimer-laser-crystallized germanium films

    Science.gov (United States)

    Liao, Chan-Yu; Huang, Ching-Yu; Huang, Ming-Hui; Huang, Wen-Hsien; Shen, Chang-Hong; Shieh, Jia-Min; Cheng, Huang-Chung

    2017-06-01

    High-performance polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) fabricated with lightly doped Ge thin films by excimer laser crystallization (ELC) and counter doping (CD) have been demonstrated. High-quality n-type Ge thin films with a grain size as large as 1 µm were fabricated by ELC in the super lateral-growth regime and CD at a dose of 1 × 1013 cm-2 or higher. Consequently, a superior field-effect mobility of 271 cm2 V-1 s-1 and a high on/off current ratio of 2.7 × 103 have been obtained for p-channel Ge TFTs with the channel width and length of both 0.5 µm fabricated by ELC at 300 mJ/cm2 and CD at a dose of 1 × 1013 cm-2. The effects of ELC conditions and CD dose on the electrical characteristics of p-channel Ge TFTs were also investigated.

  10. [Laser radiations in medical therapy].

    Science.gov (United States)

    Richand, P; Boulnois, J L

    1983-06-30

    The therapeutic effects of various types of laser beams and the various techniques employed are studied. Clinical and experimental research has shown that Helio-Neon laser beams are most effective as biological stimulants and in reducing inflammation. For this reasons they are best used in dermatological surgery cases (varicose ulcers, decubital and surgical wounds, keloid scars, etc.). Infrared diode laser beams have been shown to be highly effective painkillers especially in painful pathologies like postherpetic neuritis. The various applications of laser therapy in acupuncture, the treatment of reflex dermatologia and optic fibre endocavital therapy are presented. The neurophysiological bases of this therapy are also briefly described.

  11. Laser synchrotron radiation and beam cooling

    Energy Technology Data Exchange (ETDEWEB)

    Esarey, E.; Sprangle, P.; Ting, A. [Naval Research Lab., Washington, DC (United States)] [and others

    1995-12-31

    The interaction of intense {approx_gt} 10{sup 18} W/cm{sup 2}, short pulse ({approx_lt} 1 ps) lasers with electron beams and plasmas can lead to the generation of harmonic radiation by several mechanisms. Laser synchrotron radiation may provide a practical method for generating tunable, near monochromatic, well collimated, short pulse x-rays in compact, relatively inexpensive source. The mechanism for the generation of laser synchrotron radiation is nonlinear Thomson scattering. Short wavelengths can be generated via Thomson scattering by two methods, (i) backscattering from relativistic electron beams, in which the radiation frequency is upshifted by the relativistic factor 4{gamma}{sup 2}, and (ii) harmonic scattering, in which a multitude of harmonics are generated with harmonic numbers extending out to the critical harmonic number nc{approx_equal}a{sub 0}{sup 3} {much_gt} 1, where a{sub 0} {approx_equal}10{sup -9}{lambda}I{sup 1/2}, {lambda} is the laser wavelength in {mu}m and I is the laser intensity in W/cm{sup 2}. Laser synchrotron sources are capable of generating short ({approx_lt} ps) x-ray pulses with high peak flux ({approx_gt} 10{sup 21} photons/s) and brightness ({approx_gt}{sup 19} photons/s-mm{sup 2}-mrad{sup 2} 0.1%BW. As the electron beam radiates via Thomson scattering, it can subsequently be cooled, i.e., the beam emittance and energy spread can be reduced. This cooling can occur on rapid ({approximately} ps) time scales. In addition, electron distributions with sufficiently small axial energy spreads can be used to generate coherent XUV radiation via a laser-pumped FEL mechanism.

  12. Effect of laser radiation on rat radiosensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Laprun, I.B.

    1979-03-01

    Quite a few experimental data have been obtained to date indicating that radioresistance of the organism is enhanced under the influence of electromagnetic emissions in the radiofrequency and optical ranges. But no studies were made of the possible radioprotective properties of coherent laser radiation. At the same time, it was demonstrated that the low-energy emission of optical quantum generators (lasers) in the red band stimulates the protective forces of the organism and accelerates regenerative processes; i.e., it induces effects that are the opposite of that of ionizing radiation. Moreover, it was recently demonstrated that there is activation of catalase, a radiosensitive enzyme that plays an important role in the metabolism of peroxide compounds, under the influence of lasers. For this reason, the effect of pre-exposure to laser beams on radiosensitivity of rats was tested.

  13. Heat pump processes induced by laser radiation

    Science.gov (United States)

    Garbuny, M.; Henningsen, T.

    1980-01-01

    A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

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

    Science.gov (United States)

    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.

  15. Review of the biocompatibility and blood compatibility properties of polyethersulfone film modified by the excimer and CO2 lasers

    Science.gov (United States)

    Pazokian, H.; Jelvani, S.; Mollabashi, M.; Barzin, J.

    2014-06-01

    In this paper the biocompatibility and blood compatibility changes of polyethersulfone (PES) films following laser irradiation at four different wavelengths of ArF (193 nm), KrF (248 nm), XeCl (308 nm) and CO2 (9.58 µm) lasers are studied. The surface behaviors in contact with platelets and fibroblasts cells are examined and the best irradiation parameters to improve the surface biocompatibility and blood compatibility were found. The biological modifications on the surface were explained by alteration of the surface morphology and chemistry following the irradiation. The results show that a KrF laser is the best choice for treatment of PES film in the biological applications.

  16. Interaction of laser radiation with urinary calculi

    OpenAIRE

    Mayo, M E

    2009-01-01

    Urolithias, calculus formation in the urinary system, affects 5 – 10% of the population and is a painful and recurrent medical condition. A common approach in the treatment of calculi is the use of laser radiation, a procedure known as laser lithotripsy, however, the technique has not yet been fully optimised. This research examines the experimental parameters relevant to the interactions of the variable microsecond pulsed holmium laser (λ = 2.12 μm, τp = 120 – 800 μs, I ~ 3 MW...

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Microwave generation in an optical breakdown plasma created by modulated laser radiation

    Science.gov (United States)

    Antipov, A. A.; Grasyuk, Arkadii Z.; Losev, Leonid L.; Soskov, V. I.

    1990-06-01

    It was established that when laser radiation, intensity modulated at a frequency of 2.2 GHz, interacted with an optical breakdown plasma which it had created, a microwave component appeared in the thermal emf of the plasma. The amplitude of the microwave thermal emf reached 0.7 V for a laser radiation intensity of 6 GW/cm2. Laser radiation with λL = 1.06 μm was converted to the microwave range with λmω = 13 cm in the optical breakdown plasma. A microwave signal power of ~ 0.5 W was obtained from a laser power of ~ 5 MW.

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

    Energy Technology Data Exchange (ETDEWEB)

    Schaubroeck, David, E-mail: David.Schaubroeck@elis.ugent.be [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium); De Smet, Jelle; Willems, Wouter [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium); Cools, Pieter; De Geyter, Nathalie; Morent, Rino [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering, Ghent University, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); De Smet, Herbert; Van Steenbeerge, Geert [Center for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 15, B-9052 Ghent (Belgium)

    2016-07-15

    Highlights: • Laser patterning of thin film PEDOT:PSS on polymer foils is characterized in great detail. • PEDOT:PSS does not need to be fully removed to create electrically insulating patterns. • The underlying polymer foil influences the ablation behavior. - Abstract: 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.

  19. Effect of force on ablation depth for a XeCl excimer laser beam delivered by an optical fiber in contact with arterial tissue under saline

    NARCIS (Netherlands)

    Gijsbers, G. H.; van den Broecke, D. G.; Sprangers, R. L.; van Gemert, M. J.

    1992-01-01

    The effect of force applied to a 430 micron single fiber, delivering 60 pulses of 308 nm XeCl laser radiation at 20 Hz, on the ablation depth in porcine aortic tissue under saline has been investigated. Energy densities of 8, 15, 25, 28, 31, 37, and 45 mJ/mm2 were used. Force was applied by adding

  20. Monovisión con láser de excímeros en pacientes présbitas Monovision with Excimer laser surgery in presbyopic patients

    Directory of Open Access Journals (Sweden)

    Patricia Andújar Coba

    2010-01-01

    previstos que caracterizan a la cirugía con láser de excímeros.OBJECTIVES: To describe the refractive results achieved with Excimer laser surgery in presbyopic patients, both hyperopic and myopic, with monovision. METHODS: A prospective, longitudinal and descriptive study was performed on 60 presbyopic patients, 18 myopic and 42 hyperopic, who underwent Excimer laser surgery to correct presbyopia based on the monovision method at the Corneal and Refractive Surgery Service of «Ramón Pando Ferrer» Cuban Institute of Ophthalmology from February 2009 to February 2010. The variables used were pre- and post-operative visual acuity with correction, visual acuity without binocular correction, both near and distant, and spheral equivalents. For presenting this information, the mean and standard deviation were used for all variables. RESULTS: In the preoperative phase, it was observed that average visual acuity improved from 0,1 and 0,3 for myopic and hyperopic patients without correction, to 0,94 and 0,97 binocular visual acuity without correction for the same groups in the postoperative phase, thus correcting their average spherical equivalent of 4,63 D and +2,21 D respectively. Average near visual acuity for both groups was Jeager (J 1 - 2 and average spheral equivalents reached for distant vision were 0,02 ± 0, 27 D for myopic and +0.09 ± 0,34 D for hyperopic patients. For near vision, i.e. in the non- dominant eye, the spheral equivalent values were 1.7 ± 0,22 D for myopic and 1.4 ± 0,38 D for hyperopic patients. CONCLUSIONS: After surgery both myopic and hyperopic patients experienced improvement in their visual acuity without correction for distant as well as for near vision. Spheral equivalents were widely modified in both groups for the dominant and non-dominant eyes, in order to facilitate the final visual result in both distances with the foreseen precision in the visual results that characterizes the Excimer laser surgery.

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

    Science.gov (United States)

    Kalachyova, Yevgeniya; Lyutakov, Oleksiy; Slepicka, Petr; Elashnikov, Roman; Svorcik, Vaclav

    2014-10-01

    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.

  2. Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

    Science.gov (United States)

    Tsakonas, C.; Kuznetsov, V. L.; Cranton, W. M.; Kalfagiannis, N.; Abusabee, K. M.; Koutsogeorgis, D. C.; Abeywickrama, N.; Edwards, P. P.

    2017-12-01

    We report the low temperature (T  ZnO thin films (~140 nm) with Hall mobility of up to 17.3 cm2 V‑1 s‑1 making them suitable for thin film transistor (TFT) applications. The films were deposited by rf magnetron sputtering at T  V‑1 s‑1 at a carrier density of 2.3  ×  1018 cm‑3 was measured from a 1 GΩ as deposited and aged film after the laser treatment. We suggest that the aging of non-processed films reduces structural defects mainly at grain boundaries by air species chemisorption, with concomitant increase in thermal conductivity so that laser processing can have an enhancing effect. Such a processing combination can act synergistically and produce suitable active layers for TFT applications with low temperature processing requirements.

  3. Evaluating the interaction of 308-nm xenon chloride excimer laser with human dentin and enamel hard tissues

    Directory of Open Access Journals (Sweden)

    Mahshid Yaghmaeian-Mahabadi

    2017-11-01

    Full Text Available Background: The pulsed output of the 308 nm XeCl laser and its photoablation action rather than photothermal action offers the ability to remove dental hard tissues with minimal generation of heat in the tissue. Materials and Methods: A total of 20 human molar teeth (ten teeth used as enamel samples and ten teeth used as dentin samples after removing the enamel tissue from their crowns were irradiated by the laser. The crown of each sample was regarded as a cube which its lateral sides were exposed in 2Hz frequency without water cooling. Also, 18 holes for all enamel samples and 18 holes for all dentin samples were obtained. Three different amounts of energy were selected as a variable factor with 6 different numbers of pulses in each energy. The images of these holes were prepared by optic and computer combining, and the amounts of the ablation depth and effective ablation area were calculated using the MATLAB software. Results: The amounts of ablation depth were increased with increasing the number of pulses for both enamel and dentin tissues. The amounts of ablation depth were also increased with increasing the amounts of energy for both enamel and dentin tissues. The greater amounts of ablation depth and effective ablation area were observed in the dentin tissue rather than the enamel tissue. The borders of created holes were reported sharp and clear. Conclusion: The application of the XeCl laser for hard tissue removal and cavity preparation can be possible after some certain modifications.

  4. Suppressed intermixing in InAlGaAs/AlGaAs/GaAs and AlGaAs/GaAs quantum well heterostructures irradiated with a KrF excimer laser

    Energy Technology Data Exchange (ETDEWEB)

    Genest, J.; Dubowski, J.J.; Aimez, V. [Universite de Sherbrooke, Centre de recherche en Nanofabrication et Nanocaracteriasation (CRN2), Departement de Genie Electrique et Genie Informatique, Sherbrooke, Quebec (Canada)

    2007-11-15

    The influence of gallium arsenide surface modification induced by irradiation with a KrF excimer laser on the magnitude of the quantum well (QW) intermixing effect has been investigated in InAlGaAs/AlGaAs/GaAs QW heterostructures. The irradiation in an air environment with laser pulses of fluences between 60 and 100 mJ/cm{sup 2} has resulted in the formation of a gallium oxide-rich film at the surface. Following the annealing at 900 C, up to 35 nm suppression of the band gap blue shift was observed in all the laser irradiated samples when compared to the non-irradiated samples. The origin of suppression has been discussed in terms of stress controlled diffusion. (orig.)

  5. Controlling the parameters of YBa2Cu3O(7-delta) high-temperature superconductors through excimer laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dovgii, IA.O.; Kityk, I.V.; Lutsiv, R.V.; Malinich, S.Z.; Nosan, A.V.

    1991-02-01

    Single crystals (2x3 sq mm) of YBa2Cu3O(7{minus}{delta}) high-temperature superconductors were irradiated by an XeCl laser pumped by a gas discharge with a voltage of 35 kW and a frequency of 5 Hz. The formation of the superconducting phase was observed at oxygen pressures of 4-8 kbar. With an increase in oxygen pressure to 20 kbar, the transition temperature increased to 90 K. A possible mechanism of the observed phenomenon is examined.

  6. Controlling the parameters of YBa2Cu3O(7-delta) high-temperature superconductors through excimer laser irradiation

    Science.gov (United States)

    Dovgii, Ia. O.; Kityk, I. V.; Lutsiv, R. V.; Malinich, S. Z.; Nosan, A. V.

    1991-02-01

    Single crystals (2x3 sq mm) of YBa2Cu3O(7-delta) high-temperature superconductors were irradiated by an XeCl laser pumped by a gas discharge with a voltage of 35 kW and a frequency of 5 Hz. The formation of the superconducting phase was observed at oxygen pressures of 4-8 kbar. With an increase in oxygen pressure to 20 kbar, the transition temperature increased to 90 K. A possible mechanism of the observed phenomenon is examined.

  7. Four-year to seven-year outcomes of advanced surface ablation with excimer laser for high myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob

    2015-01-01

    Purpose: To evaluate and compare long-term outcomes ofafter photorefractive keratectomy with cooling (cPRK) and laser-assisted subepithelial keratectomy (LASEK) for high myopia. Methods: Retrospective single-masked follow-up study of patients treated for myopia between 2007 and 2009 with c...... ±1.0 D of intended refraction. Finally, 100% of cPRK patients and 92% of LASEK patients (P=0.87) were satisfied or very satisfied with the surgery at final follow-up. Conclusion: cPRK and LASEK seemed safe and with high patient satisfaction 4 to 7 years after surgery for high myopia. However, c...

  8. Development mechanism of high pressure argon plasma produced by irradiation of excimer laser. Ekishima reza ni yori seiseishita koatsuryoku arugon purazuma no seicho kiko

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, J.; Tsuda, N.; Uchida, Y.; Furuhashi, H. (Aichi Inst. of Technology, Aichi (Japan)); Sahashi, T. (Daido Inst. of Technology, Aichi (Japan))

    1994-04-20

    The studies of a high temperature and high density laser plasma are being carried out centering around solid targets, but a high density plasma can be generated also by focused irradiation of a laser light onto a high pressure gas target. However, in this case, studies on a high pressure laser plasma using the ultra-violet beam are seldom conducted. In this paper, the generation mechanism of a plasma generated mainly behind the focal point of the lens is mentioned in case when the ultra violet laser beam is focused and irradiated onto a high pressure argon gas, and it has been compared for study with the plasma generated by a ruby laser. Part of the obtained results is as follows; it has been elucidated that the plasma generated behind the focal point by focusing and irradiating an ultra violet laser beam onto a high pressure argon gas is growing simultaneously by the radiation supported shock wave and the breakdown wave, same as the case of a visible laser beam. When the ultra violet beam with frequency higher than the plasma frequency is irradiated, a plasma grows in front of the focal point too. 6 refs., 9 figs.

  9. The correlation between the laser energy density and the properties of diamond-like carbon films with Nd:YAG (355 nm) excimer laser

    CERN Document Server

    Jung, H S; Pang, S S; Lee, S Y

    1998-01-01

    Diamond-like carbon (DLC) films were deposited using pulsed laser ablation of graphite target. The deposition process was performed with the change of laser energy density from 8 to 17 J/cm sup 2. collected from analytical results, laser energy density is seen to play an important role in the formation of sp sup 3 carbon bondings in films. Also, the optimal deposition condition for DLC films was proposed and correlated with the laser energy density.

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

    Science.gov (United States)

    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.

  11. Radiative trapping in intense laser beams

    CERN Document Server

    Kirk, J G

    2016-01-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  12. LASER PHYSICS: Formation of XeCl excimer molecules as a result of mixing of gas streams excited by a continuous discharge

    Science.gov (United States)

    Mikhkel'soo, V. T.; Treshchalov, A. B.; Peét, V. É.; Yalviste, É. Kh; Belokon', A. A.; Braĭnin, B. I.; Khritov, K. M.

    1987-07-01

    A longitudinal continuous discharge in two independent supersonic gas streams, which were subsequently mixed, was used for nonequilibrium electronic excitation of components undergoing reactions and emitting chemiluminescence. Formation of XeCl excimer molecules as a result of mixing of excited He:Xe = 95:5 and He:HCl(Cl2) = 99:1 streams was deduced from the XeCl* fluorescence spectra (B→X and C→A bands). The steady-state concentration of the XeCl molecules in B and C states determined in the mixing region was ~1010 cm-3 when the pump power was 50 W, so that the efficiency of conversion of the input electrical energy into the excimer fluorescence was ~1%.

  13. Discharge modulation noise in He---Ne laser radiation

    NARCIS (Netherlands)

    Bolwijn, P.T.

    1967-01-01

    Discharge modulation noise in He---Ne laser radiation is considered theoretically, including explicitly the laser oscillator properties. Experiments reported previously by us and other authors are in agreement with our analysis.

  14. Seven year follow-up after advanced surface ablation with excimer laser for treatment of myopia: Long-term outcomes of cooling PRK and LASEK

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob

    , Odense University Hospital. Inclusion criteria: Age 20-50 years at time of surgery, pre-operative CDVA ≤ 0.10 (logMAR) and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Pregnancy and eyes having undergone re-treatment. A MEL80 flying-spot excimer......, corneal densitometry and patient satisfaction, although the long-term predictability of cPRK seemed better. Financial Disclosures: None...

  15. Competitive and synergistic effects between excimer VUV radiation and O radicals on the etching mechanisms of polyethylene and fluoropolymer surfaces treated by atmospheric He-O$_2$ post-discharge

    CERN Document Server

    Dufour, Thierry; Vandencasteele, Nicolas; Viville, Pascal; Lazzaroni, Roberto; Reniers, François

    2016-01-01

    Among various surface modification techniques, plasma can be used as a source for tailoring the surface properties of diverse materials. HDPE and fluoropolymer surfaces have been treated by the post-discharge of an atmospheric RF-plasma torch supplied with helium and oxygen gases. The plasma-treated surfaces were characterized by measurements of mass losses, water contact angles, x-ray photoelectron spectroscopy and atomic force microscopy. This experimental approach correlated with an optical characterization of the plasma phase allowed us to propose etching mechanisms occurring at the post-discharge/polymer interface. We discuss how competitive and synergistic effects can result from the oxidation and/or the roughening of the surface but also from the excimer VUV radiation, the He metastable species and the O radicals reaching the plasma-polymer interface.

  16. Laser method for simulating the transient radiation effects of semiconductor

    Science.gov (United States)

    Li, Mo; Sun, Peng; Tang, Ge; Wang, Xiaofeng; Wang, Jianwei; Zhang, Jian

    2017-05-01

    In this paper, we demonstrate the laser simulation adequacy both by theoretical analysis and experiments. We first explain the basic theory and physical mechanisms of laser simulation of transient radiation effect of semiconductor. Based on a simplified semiconductor structure, we describe the reflection, optical absorption and transmission of laser beam. Considering two cases of single-photon absorption when laser intensity is relatively low and two-photon absorption with higher laser intensity, we derive the laser simulation equivalent dose rate model. Then with 2 types of BJT transistors, laser simulation experiments and gamma ray radiation experiments are conducted. We found good linear relationship between laser simulation and gammy ray which depict the reliability of laser simulation.

  17. Laser-plasma-based Space Radiation Reproduction in the Laboratory.

    Science.gov (United States)

    Hidding, B; Karger, O; Königstein, T; Pretzler, G; Manahan, G G; McKenna, P; Gray, R; Wilson, R; Wiggins, S M; Welsh, G H; Beaton, A; Delinikolas, P; Jaroszynski, D A; Rosenzweig, J B; Karmakar, A; Ferlet-Cavrois, V; Costantino, A; Muschitiello, M; Daly, E

    2017-02-08

    Space radiation is a great danger to electronics and astronauts onboard space vessels. The spectral flux of space electrons, protons and ions for example in the radiation belts is inherently broadband, but this is a feature hard to mimic with conventional radiation sources. Using laser-plasma-accelerators, we reproduced relativistic, broadband radiation belt flux in the laboratory, and used this man-made space radiation to test the radiation hardness of space electronics. Such close mimicking of space radiation in the lab builds on the inherent ability of laser-plasma-accelerators to directly produce broadband Maxwellian-type particle flux, akin to conditions in space. In combination with the established sources, utilisation of the growing number of ever more potent laser-plasma-accelerator facilities worldwide as complementary space radiation sources can help alleviate the shortage of available beamtime and may allow for development of advanced test procedures, paving the way towards higher reliability of space missions.

  18. Synchrotron radiation photoionization mass spectrometry of laser ablated species

    OpenAIRE

    Alvarez Ruiz, Jesus; Casu, A.; Coreno, M.; De Simone, M.; Hoyos Campos, L.M.; Juarez-Reyes, A.M.; Kivimäki, A.; Orlando, S.; Sanz, M.; Spezzani, C.; Stankiewicz, M; Trucchi, D. M.

    2010-01-01

    The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1–8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation–synchrotron radiation experiments is demonstrated, opening new ...

  19. Helical magnetized wiggler for synchrotron radiation laser

    CERN Document Server

    Wang Mei; Hirshfield, J L

    1999-01-01

    A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude.

  20. Studying laser radiation effect on steel structure and properties

    Directory of Open Access Journals (Sweden)

    А. М. Gazaliyev

    2016-07-01

    Full Text Available There was studied the effect of laser radiation on the structure and properties of annealed and tempered steel with different content of carbon. For surface hardening there was used a laser complex equipped with Nd: YAG pulse laser with power density up to 30 kW/сm2. As a result of the carried-out studies there were calculated characteristics of laser, steel microstructure and properties.

  1. Interaction of CO2 laser radiation with dense plasma

    OpenAIRE

    Abdel-Raoof, Wasfi Sharkawy

    1980-01-01

    The instabilities which occur in the interaction of CO2 laser radiation with a dense plasma have been studied. A TEA CO2 laser provided pulses of up to 30 joules of energy with a duration of 50 nanoseconds. By focussing the radiation on to a plane target a focal spot of about 180 micrometers diameter was formed with a irradiance of 10 to 10 W cm. The scattered radiation was collected by a laser focussing lens and analysed with a grating spectrometer. Linear relationships have been found betwe...

  2. Laser in operative dentistry

    Directory of Open Access Journals (Sweden)

    E. Yasini

    1994-06-01

    Full Text Available Today laser has a lot of usage in medicine and dentistry. In the field of dentistry, laser is used in soft tissue surgery, sterilization of canals (in root canal therapy and in restorative dentistry laser is used for cavity preparation, caries removal, sealing the grooves (in preventive dentistry, etching enamel and dentin, composite polymerization and removal of tooth sensitivity. The use of Co2 lasers and Nd: YAG for cavity preparation, due to creating high heat causes darkness and cracks around the region of laser radiation. Also due to high temperature of these lasers, pulp damage is inevitable. So today, by using the Excimer laser especially the argon floride type with a wavelength of 193 nm, the problem of heat stress have been solved, but the use of lasers in dentistry, especially for cavity preparation needs more researches and evaluations.

  3. Controlled reshaping of the front surface of the cornea through its full-area ablation outside of the optical zone with a Gaussian ArF excimer laser beam

    Science.gov (United States)

    Semchishen, A. V.; Semchishen, V. A.

    2014-01-01

    We studied in vitro the response of the topography of the cornea to its full-area laser ablation (the laser beam spot diameter is commensurable with the size of the interface) outside of the central zone with an excimer laser having a Gaussian fluence distribution across the beam. Subject to investigation were the topographically controlled surface changes of the anterior cornea in 60 porcine eyes with a 5 ± 1.25-diopter artificially induced astigmatism, the changes being caused by laser ablation of the stromal collagen in two 3.5-mm-dia. circular areas along the weaker astigmatism axis. Experimental relationships are presented between the actual astigmatism correction and the expected correction for the intact optical zones 1, 2, 3, and 4 mm in diameter. The data for each zone were approximated by the least-squares method with the function d = a + bx. The coefficient b is given with the root-mean-square error. The statistical processing of the data yielded the following results: d = (0.14 ± 0.037)x for the 1-mm-dia. optical zone, (1.10 ± 0.036)x for the 2-mm-dia. optical zone, (1.04 ± 0.020)x for the 3-mm-dia. optical zone, and (0.55 ± 0.04)x for the 4-mm-dia. optical zone. Full astigmatism correction was achieved with ablation effected outside of the 3-mm-dia. optical zone. The surface changes of the cornea are shown to be due not only to the removal of the corneal tissue, but also to the biomechanical topographic response of the cornea to its strain caused by the formation of a dense pseudomembrane in the ablation area.

  4. A 5 Gb/s Radiation Tolerant Laser Driver

    CERN Document Server

    Amaral, L; Da Silva, S; Mazza, G; Meroli, S; Moreira, P; Rivetti, A; Troska, J; Wyllie, K

    2009-01-01

    A laser driver for data transmission at 5 Gb/s has been developed as a part of the Giga Bit Transceiver (GBT) project. The Giga Bit Laser Driver (GBLD) targets High Energy Physics (HEP) applications for which radiation tolerance is mandatory. The GBLD ASIC can drive both VCSELs and some types of edge emitting lasers. It is essentially composed of two drivers capable of sinking up to 12 mA each from the load at a maximum data rate of 5 Gb/s, and of a current sink for the laser bias current. The laser driver include also pre-emphasis and duty cycle control capabilities.

  5. Plasma lasers (a strong source of coherent radiation in astrophysics)

    Science.gov (United States)

    Papadopoulos, K.

    1981-01-01

    The generation of electromagnetic radiation from the free energy available in electron streams is discussed. The fundamental principles involved in a particular class of coherent plasma radiation sources, i.e., plasma lasers, are reviewed, focusing on three wave coupling, nonlinear parametric instabilities, and negative energy waves. The simplest case of plasma lasers, that of an unmagnetized plasma containing a finite level of density fluctuations and electrons streaming with respect to the ions, is dealt with. A much more complicated application of plasma lasers to the case of auroral kilometric radiation is then examined. The concept of free electron lasers, including the role of relativistic scattering, is elucidated. Important problems involving the escape of the excited radiation from its generation region, effects due to plasma shielding and nonlinear limits, are brought out.

  6. Spectrum characteristic study of sodium-ethane excimer pairs

    Science.gov (United States)

    Hu, Shu; Gai, Baodong; Wang, Pengyuan; Li, Hui; Tan, Yannan; Liu, Jinbo; Guo, Jingwei

    2017-01-01

    Excimer pumped sodium laser (XPNaL) can accurately achieve lasing at 589.16 nm without any complicated control system to reduce the wavelength error, so XPNaL will provide a novel technical system for sodium beacon laser. In this paper, we studied the Na-C2H6 system, which was an efficient excimer pair. We excited the Na-C2H6 system using a pulsed dye laser with wavelength of 553 nm, and measured lifetime of sodium D2 line based on the fluorescence spectra. Meanwhile, we have also detected strong amplified spontaneous emission (ASE) signal in Na-C2H6 system, through the experimental study, the Na-C2H6 system is considered to own the potential to be utilized in high power XPNaL.

  7. Coherent Cherenkov radiation and laser oscillation in a photonic crystal

    CERN Document Server

    Denis, T; Lee, J H H; van der Meer, R; Strooisma, A; van der Slot, P J M; Vos, W L; Boller, K J

    2016-01-01

    We demonstrate that photonic crystals can be used to generate powerful and highly coherent laser radiation when injecting a beam of free electrons. Using theoretical investigations we present the startup dynamics and coherence properties of such laser, in which gain is provided by matching the optical phase velocity in the photonic crystal to the velocity of the electron beam.

  8. Studies of new media radiation induced laser

    Science.gov (United States)

    Han, K. S.; Shiu, Y. J.; Raju, S. R.; Hwang, I. H.; Tabibi, B.

    1984-01-01

    Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed.

  9. Laser interferometry of radiation driven gas jets

    Science.gov (United States)

    Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

    2017-06-01

    In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)

  10. Excimer Ladar Pointer Trackers

    Science.gov (United States)

    Grossman, Jon; Brindley, William E.

    Spaceborne optical pointing and tracking systems have historically used passive sensors. With the advent of space based laser programs ,such as submarine laser communication ( SLC SAT ) and laser atmospheric wind sounder ( LAWS ), it is now possible to conceive of laser based active pointing and tracking systems. In this paper we present some the advantages of going to an active pointer-tracker, the advantages of going to a short wavelength system, and what the performance of this system would be based on current technology.

  11. INTERACTION OF FEMTOSECOND LASER RADIATION WITH SKIN: MATHEMATICAL MODEL

    Directory of Open Access Journals (Sweden)

    Pavel Yu. Rogov

    2017-03-01

    Full Text Available The features of human skin response to the impact of femtosecond laser radiation were researched. The Monte–Carlo method was used for estimation of the radiation penetration depth into the skin cover. We used prevalent wavelength equal to 800 nm (for Ti: sapphire laser femtosecond systems. A mathematical model of heat transfer process was introduced based on the analytical solution of the system of equations describing the dynamics of the electron and phonon subsystems. An experiment was carried out to determine the threshold energy of biological tissue injury (chicken skin was used as a test object. The value of electronic subsystem relaxation time was determined from the experiment and is in keeping with literature data. The results of this work can be used to assess the maximum permissible exposure of laser radiation of different lengths that cause the damage of biological tissues, as well as for the formation of safe operation standards for femtosecond laser systems.

  12. Spectroscopic study of laser irradiated chromatin

    Science.gov (United States)

    Radu, Liliana; Mihailescu, I.; Gazdaru, Doina; Preoteasa, V.

    2013-04-01

    The effects of three UV excimer laser radiations, with wavelengths of 193, 248 and 282 nm respectively, on the structure of chromatin (the complex of deoxyribonucleic acid with proteins that exists in eukaryotic cells nuclei) were investigated. The chromatin was extracted from livers of Winstar rats. The spectroscopic methods used are: fluorescence (Förster) resonance energy transfer (FRET), time resolved fluorescence and steady-state fluorescence. A chromatin deoxyribonucleic acid radiolysis, a chromatin proteins damage and a change of the global chromatin structure on lasers action were indicated by this study. It exists some small differences between the actions of these three laser radiations.

  13. Spectroscopic study of laser irradiated chromatin

    Energy Technology Data Exchange (ETDEWEB)

    Radu, Liliana, E-mail: liliana1radu@gmail.com [V. Babes National Institute, Department of Molecular Genetics and Radiobiology (Romania); Mihailescu, I. [National Institute for Lasers, Plasma and Radiation Physics, Department of Lasers (Romania); Gazdaru, Doina [Faculty of Physics, Bucharest University, Department of Biophysics (Romania); Preoteasa, V. [V. Babes National Institute, Department of Molecular Genetics and Radiobiology (Romania)

    2013-04-15

    The effects of three UV excimer laser radiations, with wavelengths of 193, 248 and 282 nm respectively, on the structure of chromatin (the complex of deoxyribonucleic acid with proteins that exists in eukaryotic cells nuclei) were investigated. The chromatin was extracted from livers of Winstar rats. The spectroscopic methods used are: fluorescence (Foerster) resonance energy transfer (FRET), time resolved fluorescence and steady-state fluorescence. A chromatin deoxyribonucleic acid radiolysis, a chromatin proteins damage and a change of the global chromatin structure on lasers action were indicated by this study. It exists some small differences between the actions of these three laser radiations.

  14. Radiative shocks in gas on the Omega laser

    Science.gov (United States)

    Reighard, A.; Drake, R. P.; Keiter, P.; Korreck, K. E.; Perry, T. S.; Robey, H. A.; Remington, B. A.; Wallace, R. J.; Ryutov, D. D.; Knauer, J.; Calder, A.; Rosner, R.; Fryxell, B.; Arnett, D.; Turner, N.; Stone, J.; Koenig, M.; Bouquet, Serge

    2002-11-01

    A number of astrophysical systems involve radiative shocks that collapse spatially in response to the energy lost through radiation. This is believed to produce thin, dense, unstable shells. We have begun experiments on the Omega laser intended to produce such collapsing shocks and to study their evolution. The experiments use the laser to accelerate a thin slab of Be, which becomes a piston that drives a shock through 1.1 atm of Ar gas at 100 km/s. The shock is predicted to collapse. Experiments are in preparation that will detect the dense layer and also the radiative precursor in front of the shock. We will report their results.

  15. [Influence of microwave and laser radiation on survivability of organisms].

    Science.gov (United States)

    Ismailov, E Sh; Zakharov, S D; Aminova, E M; Ismailova, G E; Khachirov, D G

    2001-01-01

    Depending on energy, spatial-temporal, modulation and other characteristics of an electromagnetic field, properties of a subject, exposure settings and possible interaction of other attendant factors microwaves may have either stabilizing, wholesome and even therapeutic or negative (damaging) effects on biological and ecological objects and systems. Therefore, there are two interrelated problems to be addressed. One is electromagnetic safety of and health provisions for humans exposed to EMF and EMR and the other, effective utilization of microwave EMF and EMR for biomedical and other purposes associated with enhancement of viability of organisms. The light-oxygen effect of laser radiation is gaining footing in therapy where it is used to activate or destroy biological systems by optical radiation at a specified light dose. Thus, low-intensity laser radiation can be used to improve viability and high-intensity laser radiation, to treat cancers.

  16. Counterpropagating Radiative Shock Experiments on the Orion Laser

    Science.gov (United States)

    Suzuki-Vidal, F.; Clayson, T.; Stehlé, C.; Swadling, G. F.; Foster, J. M.; Skidmore, J.; Graham, P.; Burdiak, G. C.; Lebedev, S. V.; Chaulagain, U.; Singh, R. L.; Gumbrell, E. T.; Patankar, S.; Spindloe, C.; Larour, J.; Kozlova, M.; Rodriguez, R.; Gil, J. M.; Espinosa, G.; Velarde, P.; Danson, C.

    2017-08-01

    We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

  17. Counterpropagating Radiative Shock Experiments on the Orion Laser.

    Science.gov (United States)

    Suzuki-Vidal, F; Clayson, T; Stehlé, C; Swadling, G F; Foster, J M; Skidmore, J; Graham, P; Burdiak, G C; Lebedev, S V; Chaulagain, U; Singh, R L; Gumbrell, E T; Patankar, S; Spindloe, C; Larour, J; Kozlova, M; Rodriguez, R; Gil, J M; Espinosa, G; Velarde, P; Danson, C

    2017-08-04

    We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

  18. Surface treatment of CFRP composites using femtosecond laser radiation

    Science.gov (United States)

    Oliveira, V.; Sharma, S. P.; de Moura, M. F. S. F.; Moreira, R. D. F.; Vilar, R.

    2017-07-01

    In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024 nm wavelength and 550 fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1-0.5 mJ and 0.1-5 mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

  19. Development of laser ablation plasma by anisotropic self-radiation

    Directory of Open Access Journals (Sweden)

    Ohnishi Naofumi

    2013-11-01

    Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.

  20. [Effects of laser shot frequency on plasma radiation characteristics].

    Science.gov (United States)

    Chen, Jin-Zhong; Bai, Jin-Ning; Song, Guang-Ju; Sun, Jiang; Deng, Ze-Chao; Wang, Ying-Long

    2012-11-01

    To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd:YAG laser was used to excite soil sample. The intensity and signal-to-background ratio of A1 I 394.401 nm, Ba I 455.403 nm, Fe I 430.791 nm and Ti I 498.173 nm were observed using a grating spectrometer and a photoelectric detection system. The effects of laser shot frequency (5, 10 and 15 Hz)on the radiation characteristics of laser-induced plasma was studied. The experimental results show that as compared with the laser shot frequency of 5 Hz, the spectral line intensity of A1, Ba, Fe and Ti increased by about 50.94%, 112.7%, 107.46%, and 99.38% at 15 Hz respectively under the same laser energy, while the spectral signal-to-background ratio increased by about 15.16%, 24.08%, 40.26% and 72.06% respectively. The effects mechanism of the laser shot frequency on radiation characteristics of plasma is explained by measuring plasma parameters.

  1. Mechanisms of tissue damage during ArF excimer endolaser microsurgery

    Science.gov (United States)

    Palanker, Daniel V.; Turovets, Igor; Lewis, Aaron

    1996-05-01

    The novel fiberoptic delivery system for the 193 nm excimer laser has been developed for vitreoretinal microsurgery. During the application of this laser in a liquid environment both the short-living cavitation bubbles and hydrogen gas-containing insoluble bubbles are produced. In present work we study the influence of these bubbles generated in free liquid on membranous tissue. Damage zones resulting from application of pulse trains at various repetition rates were investigated using vital stains which indicate the increase of cell membrane permeability. Cavitation bubbles were created by laser above the tissue in a highly absorbing liquid--Hartmann's solution with an addition of 7% albumin. These conditions simulate a situation in which a thin membrane separated from the underlying retina by layer of liquid is cut. After application of 50 pulses at 20 Hz at energy levels varying from 14 to 68 (mu) J per pulse we have detected cell damage at corresponding distances varying from 100 to 1200 microns. In Hartmann's solution (physiological medium), where the cavitation bubbles could not be formed at the same applied energies, the laser damage has been detected only at the distances varying from 150 to 200 microns. Penetration depth of the laser radiation in this solution is about 50 microns. The cells damage in this case probably has a photochemical nature. The difference in damage distance obtained at 1 and 20 Hz repetition rates can be explained by the influence of insoluble gas bubbles that grow at the tip exit and play a role of a transparent medium for the laser radiation. This effect probably determines the minimal distance at which the surgeon can apply the laser in standard physiological medium without being concerned with underlying cells damage. On the other hand, this phenomenon enable to destroy the upper level of cells in tissue without the deep penetrating mechanical influence associated with cavitation bubble-based tissue removal.

  2. Interaction of laser radiation with metal island films

    Science.gov (United States)

    Benditskii, A. A.; Viduta, L. V.; Ostranitsa, A. P.; Tomchuk, P. M.; Iakovlev, V. A.

    1986-08-01

    The emission phenomena arising during the interaction of pulsed laser emission with island films are examined with reference to experimental results obtained for island films of gold irradiated by a CO2 laser at a wavelength of 10.6 microns. Well reproducible emission pulses that are also accompanied by light pulses are produced at intensities less than 10 to the 5th W/sq cm, with the film structure remaining unchanged. The maximum energy of the electrons emitted under the effect of laser radiation is estimated at 3 eV; the work function is 2.1 eV.

  3. Base-Level Management of Laser Radiation Protection Program

    Science.gov (United States)

    1992-02-01

    gallium-aluminum-arsenide (GaAlAs), or alexandrite. Liquid materials that are used as active mediums include: rhodamine dye and coumarin . Section D...a source of radiation and the dye emits radiation at a longer wavelength. Coumarin dyes are useful as active media for emissions inthe blue to green...plastic, or quartz. Optical fibers have found uses in many areas including: industrial laser welding; medical surgery; dental work; product-code

  4. Selective laser cleaning of chlorine on ancient coins

    Science.gov (United States)

    Aiello, Domenico; Buccolieri, Alessandro; Buccolieri, Giovanni; Castellano, Alfredo; Di Giulio, Massimo; Leo, Laura Sandra; Lorusso, Antonella; Nassisi, Gloria; Nassisi, Vincenzo; Torrisi, Lorenzo

    2007-05-01

    Results about the efficiency of the laser cleaning on the reduction of corrosion products from the surface of ancient coins are reported. In this work an ancient copper coin datable from 1500 to 1600 A.D. and a UV excimer laser were utilized. The goal of this work consists to study the potentiality of UV laser treatment in the reduction of the chlorine concentration on the coin surface which is the main responsible of the corrosion processes of the ancient coins. We used Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD) techniques to estimate the chemical composition of the coin surface, before and after UV excimer laser cleaning. In particular, we measured the chlorine, copper and calcium concentrations. We found that a radiation dose of about 19 J/cm2 was able to reduce the chlorine concentration from 2.3 % w/w to 0.6 % w/w without damaging the metal bulk.

  5. Laser annealing heals radiation damage in avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jin Gyu [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); Anisimova, Elena; Higgins, Brendon L.; Bourgoin, Jean-Philippe [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Jennewein, Thomas [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Canadian Institute for Advanced Research, Quantum Information Science Program, Toronto, ON (Canada); Makarov, Vadim [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)

    2017-12-15

    Avalanche photodiodes (APDs) are a practical option for space-based quantum communications requiring single-photon detection. However, radiation damage to APDs significantly increases their dark count rates and thus reduces their useful lifetimes in orbit. We show that high-power laser annealing of irradiated APDs of three different models (Excelitas C30902SH, Excelitas SLiK, and Laser Components SAP500S2) heals the radiation damage and several APDs are restored to typical pre-radiation dark count rates. Of nine samples we test, six APDs were thermally annealed in a previous experiment as another solution to mitigate the radiation damage. Laser annealing reduces the dark count rates further in all samples with the maximum dark count rate reduction factor varying between 5.3 and 758 when operating at -80 C. This indicates that laser annealing is a more effective method than thermal annealing. The illumination power to reach these reduction factors ranges from 0.8 to 1.6 W. Other photon detection characteristics, such as photon detection efficiency, timing jitter, and afterpulsing probability, fluctuate but the overall performance of quantum communications should be largely unaffected by these variations. These results herald a promising method to extend the lifetime of a quantum satellite equipped with APDs. (orig.)

  6. Effect of Infrared Laser Radiation on Biological Systems.

    Science.gov (United States)

    1973-06-01

    Streptococcus faecium . The deactivation obtained in 60 seconds in the CO2 beam was the equivalent to that produced by a radiation dose of 2.5 M rad...laser pulse of the order of 10-2 seconds duration if all the energy absorbed were taken up by specific vibrational modes of the irradiated molecules

  7. Organelle-specific injury to melanin-containing cells in human skin by pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, G.F.; Shepard, R.S.; Paul, B.S.; Menkes, A.; Anderson, R.R.; Parrish, J.A.

    1983-12-01

    Physical models predict that ultraviolet laser radiation of appropriately brief pulses can selectively alter melanin-containing cellular targets in human skin. Skin of normal human volunteers was exposed to brief (20 nanosecond) 351-nm wave length pulses from a XeF excimer laser, predicting that those cells containing the greatest quantities of melanized melanosomes (lower half of the epidermis) would be selectively damaged. Transmission electron microscopy revealed the earliest cellular alteration to be immediate disruption of melanosomes, both within melanocytes and basal keratinocytes. This disruption was dose dependent and culminated in striking degenerative changes in these cells. Superficial keratinocytes and Langerhans cells were not affected. It was concluded that the XeF excimer laser is capable of organelle-specific injury to melanosomes. These findings may have important clinical implications in the treatment of both benign and malignant pigmented lesions by laser radiations of defined wave lengths and pulse durations.

  8. Laser sources in dentistry and radiation safety regulations

    Science.gov (United States)

    De Luca, D.; Gaeta, G. M.; Lepore, M.

    2007-02-01

    Nowadays laser sources are largely adopted in dentistry due to their unique properties making them good candidates to substitute traditional scalpel and conventional diamond bur in the surgery of the soft and hard oral tissue, respectively. The large use of laser sources outside the research laboratories without the need of highly specialized personnel can ask for a widespread knowledge of safety issues related to this kind of equipment. The main hazard of accidental exposures regards eyes injury but increasing the power of the laser beam also skin can be involved. Safety legislations in Europe and U.S.A. take into account non ionizing radiations and laser radiation for the hazards for the health deriving from physical agents. Laser safety standards introduce 3 useful parameters for hazard characterization: "Accessible Emission Limit" (AEL), "Maximum Permissible Exposure" (MPE) and "Nominal Ocular Hazard Distance" (NOHD). We measured the MPE and NOHD for Er:YAG and other laser sources currently adopted in dentistry and we compared our results with data elaborated from standards in order to single out safe and comfortable working conditions. In fact an experimental assessment of the hazard parameters and the comparison with those of reference from safety standards turns out to be useful in order to estimate the residual hazard that can be still present after applying all the engineering protection and administrative rules.

  9. Ovarian response to laser puncture in conditions of ionizing radiation

    Science.gov (United States)

    Vylegzhanina, T. A.; Ryzhkovskaya, E. L.

    1998-01-01

    Experimental results on long-term consequences of laser puncture applied to active points of the projection zones for the reproductive organs in guinea pigs after preliminary exposure to (gamma) -radiation are given. In female guinea pigs, it was shown that combination of external radiation (12.9 mCoul/kg) and incorporated 131I (6.5 mCi/kg) induced morphohistochemical and electron microscopic changes in the ovaries long (6 months) after, which indicated functional tension in the ovarian functioning. Laser biostimulation 3 months after the exposure to (gamma) - radiation induced severe injuries of the ovary, i.e. formation of thin-walled cysts, destruction of interstitial cells of the thecal sheath, by 6 months of the experiment. Functional incompetence of the organ was observed.

  10. Modeling classical and quantum radiation from laser-plasma accelerators

    Directory of Open Access Journals (Sweden)

    M. Chen

    2013-03-01

    Full Text Available The development of models and the “Virtual Detector for Synchrotron Radiation” (vdsr code that accurately describe the production of synchrotron radiation are described. These models and code are valid in the classical and linear (single-scattering quantum regimes and are capable of describing radiation produced from laser-plasma accelerators (LPAs through a variety of mechanisms including betatron radiation, undulator radiation, and Thomson/Compton scattering. Previous models of classical synchrotron radiation, such as those typically used for undulator radiation, are inadequate in describing the radiation spectra from electrons undergoing small numbers of oscillations. This is due to an improper treatment of a mathematical evaluation at the end points of an integration that leads to an unphysical plateau in the radiation spectrum at high frequencies, the magnitude of which increases as the number of oscillation periods decreases. This is important for betatron radiation from LPAs, in which the betatron strength parameter is large but the number of betatron periods is small. The code vdsr allows the radiation to be calculated in this regime by full integration over each electron trajectory, including end-point effects, and this code is used to calculate betatron radiation for cases of experimental interest. Radiation from Thomson scattering and Compton scattering is also studied with vdsr. For Thomson scattering, radiation reaction is included by using the Sokolov method for the calculation of the electron dynamics. For Compton scattering, quantum recoil effects are considered in vdsr by using Monte Carlo methods. The quantum calculation has been benchmarked with the classical calculation in a classical regime.

  11. Counter-propagating radiative shock experiments on the Orion laser and the formation of radiative precursors

    Science.gov (United States)

    Clayson, T.; Suzuki-Vidal, F.; Lebedev, S. V.; Swadling, G. F.; Stehlé, C.; Burdiak, G. C.; Foster, J. M.; Skidmore, J.; Graham, P.; Gumbrell, E.; Patankar, S.; Spindloe, C.; Chaulagain, U.; Kozlová, M.; Larour, J.; Singh, R. L.; Rodriguez, R.; Gil, J. M.; Espinosa, G.; Velarde, P.; Danson, C.

    2017-06-01

    We present results from new experiments to study the dynamics of radiative shocks, reverse shocks and radiative precursors. Laser ablation of a solid piston by the Orion high-power laser at AWE Aldermaston UK was used to drive radiative shocks into a gas cell initially pressurised between 0.1 and 1.0 bar with different noble gases. Shocks propagated at 80 ± 10 km/s and experienced strong radiative cooling resulting in post-shock compressions of ×25 ± 2. A combination of X-ray backlighting, optical self-emission streak imaging and interferometry (multi-frame and streak imaging) were used to simultaneously study both the shock front and the radiative precursor. These experiments present a new configuration to produce counter-propagating radiative shocks, allowing for the study of reverse shocks and providing a unique platform for numerical validation. In addition, the radiative shocks were able to expand freely into a large gas volume without being confined by the walls of the gas cell. This allows for 3-D effects of the shocks to be studied which, in principle, could lead to a more direct comparison to astrophysical phenomena. By maintaining a constant mass density between different gas fills the shocks evolved with similar hydrodynamics but the radiative precursor was found to extend significantly further in higher atomic number gases (∼4 times further in xenon than neon). Finally, 1-D and 2-D radiative-hydrodynamic simulations are presented showing good agreement with the experimental data.

  12. Effects of excimer laser irradiation on the expression of Th17, Treg, TGF-beta1, and IL-6 in patients with psoriasis vulgaris

    Science.gov (United States)

    Xiong, Guo-Xin; Li, Xin-Zhong

    2017-11-01

    The effects of laser irradiation on the expression of T helper 17 (Th17) and regulatory T (Treg) cells and their related cytokines, transforming growth factor beta 1 (TGF-β1) and interleukin-6 (IL-6), respectively, in the peripheral blood of patients with psoriasis vulgaris were investigated. 38 patients with psoriasis vulgaris in the stable state were selected as the treatment group that was treated twice a week for eight weeks. Another 38 healthy persons were chosen as the control group. Before and after treatment, the percentages of Th17 cells and Treg cells in the patients’ peripheral blood were detected using flow cytometry, the content of TGF-β1 and IL-6 in the patients’ sera were detected using enzyme-linked immunosorbent assay, and the extent and severity of lesions were determined by weighing the psoriasis area and severity index (PASI). After laser treatment, the percentage of Th17 cells, the Th17/Treg cell ratio and the level of IL-6 in the peripheral blood of patients with psoriasis in the treatment group were significantly lower than those of the same patients before the treatment (P  psoriasis vulgaris was 84.21%, and the PASI score was significantly lower (P  psoriasis vulgaris.

  13. Interaction of Er:YAG laser radiation with ureter tissue

    Science.gov (United States)

    Jelínkova, Helena; Koranda, Petr; Němec, Michal; Šulc, Jan; Köhler, Oto; Drlík, Pavel; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji

    2005-11-01

    The aim of the work was to investigate the possibility of the ureter wall perforation by Er:YAG laser radiation and to explore the basic interaction characteristics for ureter surface and its deep structures. For these experiments Er:YAG laser system (wavelength 2.94 μm) working in free-running and Q-switched regime was utilized. Laser radiation was delivered to the investigated tissue by a special waveguide system. The basic part was a cyclic olefin polymer-coated silver hollow glass waveguide (inner/outer diameter 700/850 μm or 320/450 μm). Sealed cap of the waveguide was used for contact treatment. Maximum interaction pulse energy and length for free-running Er:YAG I laser with the 700μm waveguide were 100mJ and 200μs, respectively (corresponding intensity was 130 kW/cm2). Similarly the maximum interaction pulse energy and length for free-running Er:YAG II laser with the 320 μm waveguide were 80 mJ and 200 μs , respectively (corresponding intensity was 500 kW/cm2). Maximum interaction pulse energy and length in Q-switched regime were 17 mJ and 70 ns, respectively (corresponding intensity 63 MW/cm2). The number of pulses needed to perforate the ureter wall tissue (thickness ~1 mm) for using long 200 μs Er:YAG pulses (thermal ablation) and short 70 ns Er:YAG pulses (photoablation) was found. From the histological evaluation it follows that the application of Q-switched Er:YAG laser radiation on ureteral tissue resulted in minimum adjacent tissue alteration (up to 50μm from the surface) without any influence on the deeper layers.

  14. TEA HF laser with a high specific radiation energy

    Science.gov (United States)

    Puchikin, A. V.; Andreev, M. V.; Losev, V. F.; Panchenko, Yu. N.

    2017-01-01

    Results of experimental studies of the chemical HF laser with a non-chain reaction are presented. The possibility of the total laser efficiency of 5 % is shown when a traditional C-to-C pumping circuit with the charging voltage of 20-24 kV is used. It is experimentally shown that the specific radiation output energy of 21 J/l is reached at the specific pump energy of 350 J/l in SF6/H2 = 14/1 mixture at the total pressure of 0.27 bar.

  15. Ideal radiation source for plasma spectroscopy generated by laser ablation

    Science.gov (United States)

    Hermann, Jörg; Grojo, David; Axente, Emanuel; Gerhard, Christoph; Burger, Miloš; Craciun, Valentin

    2017-11-01

    Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.

  16. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

    Science.gov (United States)

    Hugenschmidt, Manfred

    1986-10-01

    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  17. Laser system for testing radiation imaging detector circuits

    Science.gov (United States)

    Zubrzycka, Weronika; Kasinski, Krzysztof

    2015-09-01

    Performance and functionality of radiation imaging detector circuits in charge and position measurement systems need to meet tight requirements. It is therefore necessary to thoroughly test sensors as well as read-out electronics. The major disadvantages of using radioactive sources or particle beams for testing are high financial expenses and limited accessibility. As an alternative short pulses of well-focused laser beam are often used for preliminary tests. There are number of laser-based devices available on the market, but very often their applicability in this field is limited. This paper describes concept, design and validation of laser system for testing silicon sensor based radiation imaging detector circuits. The emphasis is put on keeping overall costs low while achieving all required goals: mobility, flexible parameters, remote control and possibility of carrying out automated tests. The main part of the developed device is an optical pick-up unit (OPU) used in optical disc drives. The hardware includes FPGA-controlled circuits for laser positioning in 2 dimensions (horizontal and vertical), precision timing (frequency and number) and amplitude (diode current) of short ns-scale (3.2 ns) light pulses. The system is controlled via USB interface by a dedicated LabVIEW-based application enabling full manual or semi-automated test procedures.

  18. High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

    Science.gov (United States)

    Exner, H.; Streek, A.

    2015-03-01

    Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

  19. Nozzle flow of laser-heated radiating hydrogen with application to a laser-heated rocket

    Science.gov (United States)

    Kemp, N. H.; Root, R. G.

    1977-01-01

    This paper presents a model for the steady heating of flowing hydrogen by a CW 10.6 micron laser, to consider the feasibility of a laser-heated rocket. The hydrogen flow and the laser beam are parallel, and move into a converging-diverging nozzle. The absorption of laser energy is initiated by a laser-supported combustion wave. The hydrogen is in chemical equilibrium, absorbs laser energy by inverse Bremsstrahlung, and loses energy by radiation. The hydrogen flow was calculated from the rear of the LSC wave to the throat. Estimates of convective heat losses were made using a hydrogen boundary layer analysis. Specific impulse, obtained by expanding isentropically from the throat to 1 atm or a vacuum, varies from 1400 to 3000 s. Radiation losses are 5 to 20%, though the energy fluxes to the walls are quite high. Convective loss estimates are high enough to indicate that coupling to the hot gas flow is required for a 10 kW engine, but not for a 5 MW engine.

  20. Measurements of Ionizing Radiation Doses Induced by High Irradiance Laser on Targets in LCLS MEC Instrument

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Liu, J. C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Prinz, A. A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Rokni, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tran, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Woods, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Xia, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Galter, e. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lee, H. -J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Milathianaki, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nagler, B. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2014-01-21

    Comprehensive measurements for photon and neutron radiation doses generated from laser-plasma interaction at SLAC’s MEC laser facility have been conducted. The goals of the measurements were to; determine the radiation dose per laser shot as a function of laser, optic and target parameters that are relevant to the MEC laser operations; validate the RPD-developed analytic model for photon dose calculations; and evaluate the performance of various types of passive and active detectors in the laser-induced radiation fields.

  1. Discharge-current characteristics in UV-preionized Kr/He, F2/He gas-mixtures and KrF excimer laser gas. Shigaisen yobi denri Kr/He, F2/He kongo kitai hoden oyobi KrF laser reiki hoden no denryu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, N.; Kawakami, H.; Yukimura, K. (Doshisha University, Kyoto (Japan))

    1992-08-15

    In order to study effects of Kr and F2 on discharge characteristics of KrF excimer laser gas, gap phenomena in Kr/He and F2/He gas-mixtures were observed and discharge current (I[sub d]) was measured. In the range where Kr concentration was over 10% in Kr/He gas, in which production of filamentation as well as glow discharge started, discontinuous change in I[sub d] in the second or third half cycle was observed. According to the results of experiments and model analyses, it was considered that the discontinuity of the current showed the transition point to filamentation. When F2 concentration was in the range between 0.1 and 0.3% in F2/He mixture gas, filamentation and arc with glow were observed. Sine-waveform I[sub d] ended in the first half cycle, and began to flow again after cessation or had almost constant current due to arc and others. When F2 was over 0.4%, only are discharge was observed. It was thus found that F2 has a large effect on discharge characteristics of KrF laser gas. 18 refs., 9 figs.

  2. Endoscopic diode laser therapy for chronic radiation proctitis.

    Science.gov (United States)

    Polese, Lino; Marini, Lucia; Rizzato, Roberto; Picardi, Edgardo; Merigliano, Stefano

    2018-01-01

    The purpose of this study is to determine the effectiveness of endoscopic diode laser therapy in patients presenting rectal bleeding due to chronic radiation proctitis (CRP). A retrospective analysis of CRP patients who underwent diode laser therapy in a single institution between 2010 and 2016 was carried out. The patients were treated by non-contact fibers without sedation in an outpatient setting. Fourteen patients (median age 77, range 73-87 years) diagnosed with CRP who had undergone high-dose radiotherapy for prostatic cancer and who presented with rectal bleeding were included. Six required blood transfusions. Antiplatelet (three patients) and anticoagulant (two patients) therapy was not suspended during the treatments. The patients underwent a median of two sessions; overall, a mean of 1684 J of laser energy per session was used. Bleeding was resolved in 10/14 (71%) patients, and other two patients showed improvement (93%). Only one patient, who did not complete the treatment, required blood transfusions after laser therapy; no complications were noted during or after the procedures. Study findings demonstrated that endoscopic non-contact diode laser treatment is safe and effective in CRP patients, even in those receiving antiplatelet and/or anticoagulant therapy.

  3. Use of 3-um laser radiation in middle ear surgery

    Science.gov (United States)

    Pratisto, Hans S.; Frenz, Martin; Ith, Michael; Altermatt, Hans J.; Weber, Heinz P.

    1995-01-01

    An inner ear model was used to demonstrate thermal and mechanical effects occurring during Erbium laser stapedotomy. Results of inverse schlieren optical flash photography and time resolved pressure amplitude measurements indicate the existence of safe laser parameters for stapes foot plate perforation. Due to the high absorption of 3 micrometers radiation in water, efficient bone ablation and precise fenestration with small thermally damaged zones is achieved. Pressure transients caused by the explosive ablation process correlate with the spiking of the laser intensity. The energy of a laser pulse, directly applied into the perilymph through an already existing perforation, creates a vapor channel which afterwards collapses, sending out a strong pressure transient. The maximal amplitude of this pressure transient depends on the geometry and dynamics of the vapor channel and is several times stronger than the pressure amplitudes generated by the bone ablation process. This study shows that no permanent hearing loss or damage of inner ear structures is expected using an Erbium laser fluence of 10 J/cm2.

  4. Counter-streaming radiative shock experiments on the Orion laser

    Science.gov (United States)

    Suzuki-Vidal, F.; Clayson, T.; Swadling, G. F.; Patankar, S.; Burdiak, G. C.; Lebedev, S. V.; Smith, R. A.; Stehle, C.; Chaulagain, U.; Singh, R. L.; Larour, J.; Kozlova, M.; Spindloe, C.; Foster, J.; Skidmore, J.; Gumbrell, E.; Graham, P.; Danson, C.

    2016-10-01

    The formation of radiative shocks, shocks in which the structure of density and temperature is affected by radiation from the shock-heated matter, is ubiquitous in many astrophysical scenarios. Experiments were performed at the Orion laser using a new target configuration that allows studying the formation of single and counter-streaming radiative shocks in gas-filled targets (Ne, Ar, Kr, Xe), with initial pressures 0.1-1 bar and a driver intensity of 6x1014 W/cm2 . The shocks propagate at velocities >60 km/s and were diagnosed with optical interferometry (streaked and time-resolved) and point-projection X-ray backlighting allowing to probe simultaneously the pre-shock radiative precursor and the shock front itself. Besides varying the extent of the radiative precursor the results show that different gases seem to have an effect on the shock front as evidenced by a number of spatial features. The results are compared with radiative hydrodynamics simulations in 1-D (HELIOS) and 2-D (NYM/PETRA). Supported by Orion Academic Access, the Royal Society, EPSRC, Labex PLAS@PAR. Currently at (2) LLNL, USA, (3) ELI, CZ, (4) First Light Fusion, UK.

  5. Evaluation of the performance of small diode pumped UV solid state (DPSS) Nd:YAG lasers as new radiation sources for atmospheric pressure laser ionization mass spectrometry (APLI-MS).

    Science.gov (United States)

    Kersten, Hendrik; Lorenz, Matthias; Brockmann, Klaus J; Benter, Thorsten

    2011-06-01

    The performance of a KrF* bench top excimer laser and a compact diode pumped UV solid state (DPSS) Nd:YAG laser as photo-ionizing source in LC-APLI MS is compared. The commonly applied bench-top excimer laser, operating at 248 nm, provides power densities of the order of low MW/cm(2) on an illuminated area of 0.5 cm(2) (8 mJ/pulse, 5 ns pulse duration, beam waist area 0.5 cm(2), 3 MW/cm(2)). The DPSS laser, operating at 266 nm, provides higher power densities, however, on a two orders of magnitude smaller illuminated area (60 μJ/pulse, 1 ns pulse duration, beam waist area 2 × 10(-3) cm(2), 30 MW/cm(2)). In a common LC-APLI MS setup with direct infusion of a 10 nM pyrene solution, the DPSS laser yields a significantly smaller ion signal (0.9%) and signal to noise ratio (1.4%) compared with the excimer laser. With respect to the determined low detection limits (LODs) for PAHs of 0.1 fmol using an excimer laser, LODs in DPSS laser LC-APLI MS in the low pmol regime are expected. The advantages of the DPSS laser with respect to applicability (size, cost, simplicity) may render this light source the preferred one for APLI applications not focusing on ultimately high sensitivities. Furthermore, the impact of adjustable ion source parameters on the performance of both laser systems is discussed in terms of the spatial sensitivity distribution described by the distribution of ion acceptance (DIA) measurements. Perspectives concerning the impact on future APLI-MS applications are given.

  6. Choice of the laser wavelength for a herpetic keratitis treatment

    Science.gov (United States)

    Razhev, Alexander M.; Bagayev, Sergei N.; Chernikh, Valery V.; Kargapoltsev, Evgeny S.; Trunov, Alexander; Zhupikov, Andrey A.

    2002-06-01

    For the first time the effect of the UV laser radiation to human eye cornea with herpetic keratitis was experimentally investigated. In experiments the UV radiation of ArF (193 nm), KrCl (223 nm), KrF (248 nm) excimer lasers were used. Optimal laser radiation parameters for the treatment of the herpetic keratitis were determined. The immuno-biochemical investigations were carried out and the results of clinical trials are presented. The maximum ablation rate was obtained for the 248 nm radiation wavelength. The process of healing was successful but in some cases the haze on the surface of the cornea was observed. When used the 193 nm radiation wavelength the corneal surface was clear without any hazes but the epithelization process was slower than for 248 nm wavelength and in some cases the relapse was occurred. The best results for herpetic keratitis treatment have been achieved by utilizing the 223 nm radiation wavelength of the KrCl excimer laser. The use of the 223 nm radiation wavelength allows treating the herpetic keratitis with low traumatic process of ablation and provides high quality of corneal surface.

  7. Generation and use of high power 213 nm and 266 nm laser radiation and tunable 210-400 nm laser radiation with BBO crystal matrix array

    Science.gov (United States)

    Gruen, Dieter M.

    2000-01-01

    A 213 nm laser beam is capable of single photon ablative photodecomposition for the removal of a polymer or biological material substrate. Breaking the molecular bonds and displacing the molecules away from the substrate in a very short time period results in most of the laser photon energy being carried away by the displaced molecules, thus minimizing thermal damage to the substrate. The incident laser beam may be unfocussed and is preferably produced by quintupling the 1064 nm radiation from a Nd:YAG solid state laser, i.e., at 213 nm. In one application, the 213 nm laser beam is expanded in cross section and directed through a plurality of small beta barium borate (BBO) crystals for increasing the energy per photon of the laser radiation directed onto the substrate. The BBO crystals are arranged in a crystal matrix array to provide a large laser beam transmission area capable of accommodating high energy laser radiation without damaging the BBO crystals. The BBO crystal matrix array may also be used with 266 nm laser radiation for carrying out single or multi photon ablative photodecomposition. The BBO crystal matrix array may also be used in an optical parametric oscillator mode to generate high power tunable laser radiation in the range of 210-400 nm.

  8. Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues

    Science.gov (United States)

    Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.

    2013-08-01

    This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

  9. LASERS: Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge

    Science.gov (United States)

    Kamrukov, A. S.; Kozlov, N. P.; Opekan, A. G.; Protasov, Yu S.; Rudoĭ, I. G.; Soroka, A. M.

    1989-07-01

    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic discharge in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar = 1:250) and the total pressure was 1 atm, the output energy was ~ 0.5 J in the form of pulses of ~ 10 μs duration and the maximum specific output energy represented by laser radiation was 1-2 J/liter. The unsaturated gain was 27 m - 1. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated and it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  10. Photolysis of tryptophan with 337. 1 nm laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Borkman, R.F.; Hibbard, L.B.; Dillon, J.

    1986-01-01

    Aqueous solutions of L-tryptophan were photolyzed by exposure to 337.1 nm radiation from a pulsed nitrogen laser. These data were compared with results for the 290 nm conventional-source photolysis of tryptophan. The loss of Trp was observed to be first order for 290 nm photolysis but of mixed order for 337.1 nm photolysis. Five photolysis products including N-formylkynurenine, kynurenine, tryptamine and two unknown products were detected. The tryptophan-containing peptides N-acetyl-tryptophanamide (NATA) and tryptophylglycine (Trp-Gly) were also observed to photolyze upon 337.1 nm laser radiation demonstrating that this phenomenon is not restricted to free tryptophan monomer. A number of experiments were performed in an effort to determine the mechanism of photolysis at this wavelength. It is concluded that this photolysis results either from a very weak absorption tail extending to 337.1 nm in tryptophan itself or from a reaction involving an impurity sensitizer which absorbs the 337.1 nm radiation.

  11. Experimental comparison of laser energy losses in high-quality laser-oxygen cutting of low-carbon steel using radiation from fibre and CO2 lasers

    Science.gov (United States)

    Golyshev, A. A.; Malikov, A. G.; Orishich, A. M.; Shulyat'ev, V. B.

    2015-09-01

    We report a comparative experimental study of laseroxygen cutting of low-carbon steel using a fibre laser with a wavelength of 1.07 μm and a CO2 laser with a wavelength of 10.6 μm at the sheet thickness of 3 - 16 mm. For the two lasers we have measured the dependence of the cutting speed on the radiation power and determined the cutting speed at which the surface roughness is minimal. The coefficient of laser radiation absorption in the laser cutting process is measured for these lasers at different values of the cutting speed and radiation power. It is found that the minimal roughness of the cut surface is reached at the absorbed laser energy per unit volume of the removed material, equal to 11 - 13 J mm-3; this value is the same for the two lasers and does not depend on the sheet thickness.

  12. Determination of the radiation axis position of an unstable-cavity laser

    Science.gov (United States)

    Agroskin, V. Ya; Bravyi, B. G.; Vasil'ev, G. K.; Gur'ev, V. I.; Karel'skii, V. G.; Kashtanov, S. A.; Makarov, E. F.; Sotnichenko, S. A.; Chernyshev, Yu A.

    2017-08-01

    Propagation of an alignment laser beam through an unstable cavity laser is numerically simulated. It is shown that the axis of the expanded beam coincides with that of the fundamental laser radiation within an accuracy of no less than 1'' even under cavity misalignment of up to 30''. Experiments on determining the position of the radiation axis of a high-power pulsed unstable cavity chemical laser and various cavity misalignments confirm the calculation results.

  13. Xenon plasma sustained by pulse-periodic laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu., E-mail: yakimov@lantanlaser.ru [Russian Academy of Sciences, A. Ishlinsky Institute for Problems in Mechanics (Russian Federation)

    2015-10-15

    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  14. Investigation of temperature feedback signal parameters during neoplasms treatment by diode laser radiation

    Science.gov (United States)

    Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Semyashkina, Yulia V.

    2016-04-01

    Dynamics of temperature signal in operation area and laser power at nevus, papilloma, and keratoma in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and with temperature feedback (APC) mode are presented. Feedback allows maintaining temperature in the area of laser treatment at a preset level by regulating power of diode laser radiation (automatic power control). Temperature in the area of laser treatment was controlled by measuring the amplitude of thermal radiation, which occurs when tissue is heated by laser radiation. Removal of neoplasm was carried out in CW mode with laser radiation average power of 12.5+/-0.5 W; mean temperature in the area of laser treatment was 900+/-10°C for nevus, 800+/-15°C for papilloma, and 850+/-20°C for keratoma. The same laser radiation maximal power (12.5 W) and targeted temperature (900°C) were set for nevus removal in APC mode. The results of investigation are real time oscillograms of the laser power and temperature in the area of laser treatment at neoplasms removal in two described above modes. Simultaneously with the measurement of laser power and the temperature in the area of laser treatment video recording of surgeon manipulations was carried out. We discuss the correlation between the power of the laser radiation, the temperature in the area of laser treatment and consistency of surgeon manipulation. It is shown that the method of removal (excision with or without traction, scanning) influences the temperature in the area of laser treatment. It was found, that at removal of nevus with temperature feedback (APC) mode to achieve comparable with CW mode temperature in the area of laser treatment (900+/-10°C) 20-50% less laser power is required. Consequently, removing these neoplasms in temperature feedback mode can be less traumatic than the removal in CW mode.

  15. High Energy Ion Acceleration by Extreme Laser Radiation Pressure

    Science.gov (United States)

    2017-03-14

    AFRL-AFOSR-UK-TR-2017-0015 High energy ion acceleration by extreme laser radiation pressure Paul McKenna UNIVERSITY OF STRATHCLYDE VIZ ROYAL COLLEGE...MM-YYYY)   14-03-2017 2. REPORT TYPE  Final 3. DATES COVERED (From - To)  01 May 2013 to 31 Dec 2016 4. TITLE AND SUBTITLE High energy ion acceleration...Prescribed by ANSI Std. Z39.18 Page 1 of 1FORM SF 298 3/15/2017https://livelink.ebs.afrl.af.mil/livelink/llisapi.dll 1 HIGH ENERGY ION ACCELERATION BY

  16. Pressure and gap length dependence of gap breakdown voltage and discharge current of discharge-pumped KrF excimer laser. Hoden reiki KrF laser no zetsuen hakai den prime atsu to reiki denryu no atsuryoku, gap cho izon sei

    Energy Technology Data Exchange (ETDEWEB)

    Yukimura, K.; Kawakami, H. (Doshisha Univ., Tokyo (Japan)); Hitomi, K. (Kyoto Polytechnic College, Kyoto (Japan))

    1991-04-20

    On the gap destruction characteristics of UV-preionized discharge-pumped KrF excimer laser (charge transfer type) and the electric characteristics of the excited discharge, studies were made by changing the pressure (1.5-3 atm) and the discharge gap length (14-21 mm) of the discharge medium. (1) Gap breakdown voltage and the maximum current of the excited discharge give a similarity by a product of pressure and the gap length at the charge volatge. (2) Insulation breakdown of the gap occurs at the wave front of the applied voltage and the breakdown time gets delayed by the decreasing voltage applied. By setting the ionization index at constant value 20, the gap breakdown voltage is estimated at the error within 10%. (3) The relation between the maximum current, pressure and the gap length product changes the characteristics by the charge voltage of the primary condenser. With the result combined with the standardization of voltage/current of the excited discharge, the electric characteristics at the specific pressure and gap length can be readily known. 10 refs., 10 figs.

  17. Ultraviolet Radiation Effects On UV-Transmitting Fluor Crown Glasses

    Science.gov (United States)

    Liepmann, Monika J.; Marker, Alexander J.; Sowada, Ulrich

    1989-01-01

    Fluor crown glasses, having improved transparency in the UV-spectral region, can be produced by using a proprietary melting technique. The short wavelength cut on of this family of UV-transmitting glasses is similar to that of vitreous silica. In the present investigation the effect of broadband UV-radiation has been studied as a function of time and optical absorption primarily for the glass type UVFK-54. Further tests were performed using discrete line radiation of 248 nm from a pulsed excimer laser. The intensity of the darkening effect is correlated to the intensity and dose of radiation. In addition, recovery experiments using elevated temperatures and different times are discussed.

  18. Photo-induced growth of dielectrics with excimer lamps

    Science.gov (United States)

    Boyd, Ian W.; Zhang, Jun-Ying

    2001-08-01

    The underlying principles and properties of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation (excimer lamps), generated by a dielectric barrier discharge in a rare-gas (Rg) or a mixture of Rg and halogen, are discussed. Compared with conventional sources, these excimer lamps offer narrow-band radiation at various wavelengths from 108-354 nm and over large areas with high efficiencies and high power densities. The variety of available wavelengths offers an enormous potential for new industrial applications in materials processing. Previously, photo-oxidation of silicon, germanium and silicon-germanium and photo-deposition of single- and multi-layered films of silicon oxide, silicon nitride, and silicon oxynitride have been demonstrated by using excimer lamps. This paper reviews the progress on excimer lamp-assisted growth of high dielectric constant (Ta2O5, TiO2 and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing, summarizes the properties of photo-induced growth of Ta2O5 films and discusses the effect and mechanism of low temperature UV annealing with 172 nm radiation. Metal oxide semiconductor capacitors based on the photo-induced Ta2O5 films grown directly on Si at low temperatures exhibit excellent electrical properties. Leakage current densities as low as 5.2×10-7 A cm-2 and 2.41×10-7 A cm-2 at 1 MV cm-1 have been achieved for the as-grown Ta2O5 films deposited by photo-induced sol-gel processing and photo-CVD, respectively-several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 10-8 A cm-2. These values are comparable to those only previously achieved for films annealed at high temperatures between 600°C and 1000°C. These properties make the photo-induced growth of Ta2O5 layers suitable alternative to SiO2 for high density DRAM application.

  19. INTERACTION OF LASER RADIATION WITH MATTER: Investigation of the interaction of laser radiation with composite materials by infrared spectroscopy methods

    Science.gov (United States)

    Eremin, V. I.; Kovalenko, I. P.; Levashenko, G. I.; Mazaev, N. V.; Sokol'nikov, A. S.; Shuralev, S. L.

    1990-10-01

    A description is given of the method and apparatus for determination of the effective temperature and composition of a jet of products of the interaction of laser radiation with a glass-fiber-reinforced plastic and an organic plastic. Measurements are also possible of the temperature and emissivity of a target when it is exposed in atmospheric air to cw CO2 laser radiation with a flux density of 3 × 102 — 103 W/cm2. The products of damage to the glass-fiber-reinforced plastic consisted of particles of metal oxides with a diameter d32 = 2.3-3.5 μm and a volume concentration Cv = (0.06-0.25) × 10 - 4, and of molecular gases CO2, H2O, and HCl; the damage products of the organic plastic were conglomerates of soot particles with the diameter d32 = 1-1.8 μm and a volume concentration Cv = (0.4-0.9) × 10 - 4, and the same molecular gases. The target emissivity increased with time and reached 0.8-0.9.

  20. Temporal structure of X-ray radiation pulses of picosecond laser plasma

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, V S; Kovkov, D V; Matafonov, A P; Karabadzhak, G F; Raikunov, G G [Central Research Institute of Machine Building, Korolev, Moscow region (Russian Federation); Faenov, A Ya; Pikuz, S A; Skobelev, I Yu; Pikuz, T A; Fokin, D A; Fortov, V E [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Ignat' ev, G N; Kapitanov, S V; Krapiva, P S; Korotkov, K E [All-Russian Institute of Automatics, Moscow (Russian Federation)

    2013-09-30

    The shape of the X-ray pulse generated by picosecond laser plasma is experimentally studied. The unusual phenomenon was experimentally observed for the first time for targets made of moderate-heavy chemical elements, namely, the pulse of hard X-ray radiation generated by laser plasma at the laser radiation flux of ∼10{sup 18} W cm{sup -2} had a longer duration than the pulse of softer X-ray radiation. A simple kinetic model is suggested for explaining this fact. We have suggested a method for controlling the temporal shape of X-ray pulse emitted by laser plasma by varying the contrast of laser pulse. (interaction of laser radiation with matter)

  1. The influence of resonance IR laser radiation on magnetoabsorption in quantum wires

    Science.gov (United States)

    Sinyavskii, E. P.; Karapetyan, S. A.; Kostyukevich, N. S.

    2017-04-01

    The coefficient of interband absorption of a weak electromagnetic wave by quantum wires in a transverse magnetic field and an intense laser radiation field is calculated. It is shown that, if the laser radiation frequency is equal either to the size quantization frequency (dimensional infrared resonance) or to a hybrid frequency (magnetoinfrared resonance), laser illumination can determine the shape of absorption oscillations. In particular, it is shown that the second magnetoabsorption peak is split into two peaks, the half-widths of which and the distance between which depend on the intensity of resonance laser radiation. The influence of the polarization of IR radiation on the interband absorption in quantum wires is discussed. The dynamics of the frequency dependence of the optical absorption coefficient with increasing intensity of resonance laser radiation is studied.

  2. Interaction of laser radiation with a low-density structured absorber

    Czech Academy of Sciences Publication Activity Database

    Rozanov, V. B.; Barishpol’tsev, D.V.; Vergunova, G.A.; Demchenko, N. N.; Ivanov, E.M.; Aristova, E.N.; Zmitrenko, N.V.; Limpouch, I.; Ullschmied, Jiří

    2016-01-01

    Roč. 122, č. 2 (2016), s. 256-276 ISSN 1063-7761 Institutional support: RVO:61389021 Keywords : laser radiation interaction * laser with low-density Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.196, year: 2016

  3. INTERACTION OF LASER RADIATION WITH MATTER: Influence of surface breakdown on the process of drilling metals with pulsed CO2 laser radiation

    Science.gov (United States)

    Arutyunyan, R. V.; Baranov, V. Yu; Bobkov, I. V.; Bol'shov, Leonid A.; Dolgov, V. A.; Kanevskiĭ, M. F.; Malyuta, D. D.; Mezhevov, V. S.

    1988-03-01

    A report is given of the influence of low-threshold surface optical breakdown, occurring under the action of short (~ 5-μs) radiation pulses from a CO2 laser, on the process of the laser drilling of metals. Data are given on the difference between the interaction of radiation pulses having the same duration but differing in shape. A study was made of the influence of the pressure of the atmosphere surrounding a target on the results of laser drilling of metals. A theoretical explanation is given of the experimental results.

  4. Mobility of Electron in DNA Crystals by Laser Radiation

    Science.gov (United States)

    Zhang, Kaixi; Zhao, Qingxun; Cui, Zhiyun; Zhang, Ping; Dong, Lifang

    1996-01-01

    The mobility of electrons in laser radiated DNA is closed to the energy transfer and energy migration of a biological molecule. Arrhenius has studied the conductivity of the electrons in a biological molecule. But his result is far from the experimental result and meanwhile the relation between some parameters in his theory and the micro-quantities in DNA is not very clear. In this paper, we propose a new phonon model of electron mobility in DNA and use Lippman-Schwinger equation and S-matrix theory to study the mobility of electrons in DNA crystal. The result is relatively close to the experiment result and some parameters in Arrhenius theory are explained in our work.

  5. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Plasma heating near a metal target by nanosecond pulses of the first, second, and fourth Nd-laser harmonics

    Science.gov (United States)

    Bufetov, Igor'A.; Bufetova, G. A.; Kravtsov, S. B.; Fyodorov, V. B.; Fomin, V. K.

    1995-08-01

    Measurements were made of the electron temperature Te of a laser plasma formed on the surface of a metal target by the action of nanosecond pulses of wavelengths λ = 1060, 530, and 265 nm. The laser radiation intensity was I approx 109—1013 W cm-2. The electron temperature was determined from the emf of a double charge layer at the plasma boundary. Within the limits of the scatter of the experimental results, the plasma temperature was independent of the laser radiation wavelength (in the range 1060-265 nm). The dependence of this temperature on the radiation intensity obeyed approximately Te propto I1/3 throughout the investigated range.

  6. Radiation effects on poly(methyl methacrylate) induced by pulsed laser irradiations

    Science.gov (United States)

    Torrisi, L.; Italiano, A.; Amato, E.; Caridi, F.; Cutroneo, M.; Squeri, C. A.; Squeri, G.; Roszkowska, A. M.

    2012-09-01

    Poly(methyl methacrylate) (PMMA) was irradiated using a medical UV-ArF excimer laser operating at the fundamental wavelength of 193 nm. Characterized by a beam diameter of 1.8 mm and energy of 180 mJ with a Gaussian energy profile, it operates in a single mode or at 30 Hz repetition rate. Mechanical profilometry was carried out on ablation craters in order to study the rugosity and the ablation yield in the various operative conditions. Optical transmission and reflection measurements at six wavelengths were conducted in order to characterize the optical properties of the irradiated surfaces. Measured crater depths in PMMA were lower with respect to the forecasted ones in corneal tissue, while the lateral crater aperture was maintained. The rugosity produced at the crater bottom after irradiation was about 0.3 μm, and the ablation yield was about 1015 molecules/laser pulse, while etching depth and diameter show a roughly linear dependence on the number of laser shots. These experiments constitute a base for deeper clinical investigations.

  7. Influence of He-Ne laser radiation of pacemaker on the frog's heart function

    Science.gov (United States)

    Porozov, Yury B.; Brill, Gregory E.; Kiritchuk, Vyacheslav F.

    1997-02-01

    In experiments on isolated amphibian hearts changes in photoreactivity of pacemaker cells under the influence of He-Ne laser radiation in different phases of the heart cycle were studied. The specificity of heart photoreaction, peculiarities of relaxation period after laser light action and laser modification of hypodynamic depression development were revealed. Adaptation of pacemaker cells to the He-Ne laser exposure was observed.

  8. Multidisciplinary approaches to radiation-balanced lasers (MARBLE): a MURI program by AFOSR (Conference Presentation)

    Science.gov (United States)

    Sheik-Bahae, Mansoor

    2017-02-01

    An overview of the diverse research activities under the newly funded MURI project by AFOSR will be presented. The main goal is to advance the science of radiation-balanced lasers, also known as athermal lasers, in order to mitigate the thermal degradation of the high-power laser beams. The MARBLE project involves researchers from four universities and spans research activities in rare-earth doped crystals and fibers to semiconductor disc lasers.

  9. Generation of UV radiation by vapors of complex molecules

    Energy Technology Data Exchange (ETDEWEB)

    Barkova, L.A.; Gruzinskii, V.V.; Danilova, V.I.; Degtiarenko, K.M.; Kopylova, T.N.; Kuznetsov, A.L.

    1981-08-01

    Laser action has been obtained in the following organic compounds under pumping by XeCl excimer laser radiation at 308 nm: para-terphenyl, 2-phenylbenzoxazole, 2-(n-tolyl)-benzoxaxole, 2-(n-methoxyphenyl)-benzoxazole, 2-(n-dimethylaminophenyl)-benzoxazole, 2-biphenylbenzoxazole, (2-alpha-naphthyl)-benzoxazole, 1.4-di(n-phenylethynyl)-benzole, and paraquaterphenyl. The nontuning lasing bands covered the range of 330-370 nm, and the most short-wavelength maximum (333.5 nm) was found for 2(n-methoxyphenyl)-benzoxazole. The lasing capability of the molecules was analyzed.

  10. Coherent and incoherent radiation from a channel-guided laser wakefield accelerator

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.

    2008-01-01

    Coherent and incoherent electromagnetic radiation emitted from a channel-guided laser wakefield accelerator (LWFA) is calculated based on the Lienard–Wiechert potentials. It is found that at wavelengths longer than the bunch length, the radiation is coherent. The coherent radiation, which typically

  11. Transurethral coagulation for radiation-induced hemorrhagic cystitis using Greenlight™ potassium-titanyl-phosphate laser.

    Science.gov (United States)

    Zhu, Jin; Xue, Boxin; Shan, Yuxi; Yang, Dongrong; Zang, Yachen

    2013-02-01

    The aim of this study was to to demonstrate the initial treatment outcomes of Greenlight™ potassium-titanyl-phosphate (KTP) laser on radiation-induced hemorrhagic cystitis. Hemorrhagic cystitis is a common complication of radiation therapy for pelvic tumors. From September 2004 to February 2011, 10 patients with radiation-induced intractable hemorrhagic cystitis underwent transurethral Greenlight KTP laser coagulation of the bladder. The power setting was limited to 20-30 W. Bleeding stopped in all cases after one session of laser treatment. Mean follow-up time was 17 months (6-36 months). All patients underwent cystoscopy 3 months postoperatively, and no bleeding or significant scar was found. Recurrence of significant bleeding was seen in one case 7 months post-operation, and was again cured by KTP laser. There were no complications from the procedures. Our experience suggests that transurethral coagulation using KTP laser is a safe and effective strategy for the treatment of hemorrhagic radiation cystitis.

  12. Modelling of micromachining of human tooth enamel by erbium laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Belikov, A V; Skrypnik, A V; Shatilova, K V [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg (Russian Federation)

    2014-08-31

    We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained. (laser biophotonics)

  13. Recycling of laser and plasma radiation energy for enhancement of extreme ultraviolet sources for nanolithography

    Science.gov (United States)

    Sizyuk, V.; Sizyuk, T.; Hassanein, A.; Johnson, K.

    2018-01-01

    We have developed comprehensive integrated models for detailed simulation of laser-produced plasma (LPP) and laser/target interaction, with potential recycling of the escaping laser and out-of-band plasma radiation. Recycling, i.e., returning the escaping laser and plasma radiation to the extreme ultraviolet (EUV) generation region using retroreflective mirrors, has the potential of increasing the EUV conversion efficiency (CE) by up to 60% according to our simulations. This would result in significantly reduced power consumption and/or increased EUV output. Based on our recently developed models, our High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer simulation package was upgraded for LPP devices to include various radiation recycling regimes and to estimate the potential CE enhancement. The upgraded HEIGHTS was used to study recycling of both laser and plasma-generated radiation and to predict possible gains in conversion efficiency compared to no-recycling LPP devices when using droplets of tin target. We considered three versions of the LPP system including a single CO2 laser, a single Nd:YAG laser, and a dual-pulse device combining both laser systems. The gains in generating EUV energy were predicted and compared for these systems. Overall, laser and radiation energy recycling showed the potential for significant enhancement in source efficiency of up to 60% for the dual-pulse system. Significantly higher CE gains might be possible with optimization of the pre-pulse and main pulse parameters and source size.

  14. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Laser ablation plume dynamics in nanoparticle synthesis

    Science.gov (United States)

    Osipov, V. V.; Platonov, V. V.; Lisenkov, V. V.

    2009-06-01

    The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO2 laser pulse with a duration of ~500 μs (at the 0.03 level), energy of 1.0-1.3 J and peak power of 6-7 kW have been studied using high-speed photography of the plume luminescence and shadow. The targets were used to produce nanopowders by laser evaporation. About 200 μs after termination of the pulse, shadowgraph images of the plumes above the YSZ and Nd:YAG targets showed dark straight tracks produced by large particles. The formation of large (~10 μm) particles is tentatively attributed to cracking of the solidified melt at the bottom of the ablation crater. This is supported by the fact that no large particles are ejected from graphite, which sublimes without melting. Further support to this hypothesis is provided by numerical 3D modelling of melt cooling in craters produced by laser pulses of different shapes.

  15. Comparison of the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation.

    Science.gov (United States)

    Yin, Jian; Han, Zhengfeng; Guo, Baofeng; Guo, Han; Zhang, Tongtong; Zeng, Yanjun; Ren, Longxi

    2015-07-01

    To compare the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation. Goat spine specimen (GSS) was radiated using Nd:YAG laser and 980 nm diode laser and then divided into five groups based on the final energy--200, 400, 600, 800 and 1,000 J groups. The ablation quality of nucleus pulposus after radiation was recorded. The ablation quality of GSS was greater at higher radiation energies in both lasers. When compared at the same energy level, the ablation quality of GSS was greater in 980 nm diode laser than in 1,064 nm Nd:YAG laser. Statistical significance was observed in 200 and 400 J groups (P laser showed better ablation ability than 1,064 nm Nd:YAG laser.

  16. Mechanisms of graphene exfoliation under the action of femtosecond laser radiation in liquid nitrogen

    Science.gov (United States)

    Khorkov, K. S.; Kochuev, D. A.; Ilin, V. A.; Chkalov, R. V.; Prokoshev, V. G.; Arakelian, S. M.

    2018-01-01

    The processes of graphene structures formation under the action of the femtosecond laser radiation on carbon samples in liquid nitrogen are discussed. Mechanisms of graphene sheets exfoliation are proposed depending on the power density of the laser radiation: in the first case, the separation occurs due to the volumetric expansion during heating the region occupied by nitrogen molecules; at a laser radiation energy exceeding the ablation threshold, the surface of graphite begins to breakdown in the region of the action, followed by separation into graphene layers.

  17. High power lasers in manufacturing

    OpenAIRE

    Chatwin, Chris R

    2017-01-01

    Lecture covers a brief history of lasers and the important beam parameters for manufacturing applications. It introduces the main laser types that are appropriate for manufacturing: carbon dioxide lasers, Nd YAG, Diode and fibre lasers, excimer lasers. It then looks at applications to different products and also micro-engineering

  18. Analytical modeling of polarization transformation of laser radiation of various spectral ranges by birefringent structures

    Science.gov (United States)

    Motrich, A. V.; Ushenko, O. G.

    2018-01-01

    The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave ("red-blue") approach - layer of biological tissues irradiated by He-Ne laser (λ1 = 0,63μm ) and He-Cd laser (λ1 = 0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

  19. Role of laser radiation in activating anodic dissolution under electrochemical machining of metals and alloys

    Directory of Open Access Journals (Sweden)

    Rakhimyanov Kharis

    2017-01-01

    Full Text Available The specific features of electrochemical dissolution of the 12X18H9T stainless steel, the OT-4 titanium alloy and the BK8 hard alloy in the sodium nitrate water solution exposed to 1.06 micrometer wavelength laser radiation were considered. It is found that depassivation of the anode surface is the main mechanism of laser activation in electrochemical dissolving of materials. It is established that the maximum efficiency of laser electrochemical machining is achieved at a pulse repetition frequency of 10 kHz laser radiation. It is connected with the photoactivation mechanism of electrolyte solution molecules, which increases their reaction capacity.

  20. ARTICLES: Physical laws governing the interaction of pulse-periodic CO2 laser radiation with metals

    Science.gov (United States)

    Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Pavlovich, Yu V.; Senatorov, Yu M.

    1985-01-01

    It is shown theoretically and experimentally that the efficiency of welding metals with a pulse-periodic CO2 laser beam of low duty ratio, at low velocities, can exceed that of welding with cw lasers and with electron beams. For the first time an investigation was made of the influence of the laser radiation parameters (energy and frequency) and of the welding velocity on the characteristics of the weld and on the shape of the weldpool. The influence of the laser radiation polarization on the efficiency of deep penetration was analyzed.

  1. Radiation from laser accelerated electron bunches: Coherent terahertz and femtosecond X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Leemans, W.P.; Esarey, E.; van Tilborg, J.; Michel, P.A.; Schroeder, C.B.; Toth, Cs.; Geddes, C.G.R.; Shadwick, B.A.

    2004-10-01

    Electron beam based radiation sources provide electromagnetic radiation for countless applications. The properties of the radiation are primarily determined by the properties of the electron beam. Compact laser driven accelerators are being developed that can provide ultra-short electron bunches (femtosecond duration) with relativistic energies reaching towards a GeV. The electron bunches are produced when an intense laser interacts with a dense plasma and excites a large amplitude plasma density modulation (wakefield) that can trap background electrons and accelerate them to high energies. The short pulse nature of the accelerated bunches and high particle energy offer the possibility of generating radiation from one compact source that ranges from coherent terahertz to gamma rays. The intrinsic synchronization to a laser pulse and unique character of the radiation offers a wide range of possibilities for scientific applications. Two particular radiation source regimes are discussed: Coherent terahertz emission and x-ray emission based on betatron oscillations and Thomson scattering.

  2. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: The mechanism of the drilling of holes in vertical metallic plates by cw CO2 laser radiation

    Science.gov (United States)

    Likhanskii, V. V.; Loboiko, A. I.; Antonova, G. F.; Krasyukov, A. G.; Sayapin, V. P.

    1999-02-01

    The possibility of making a hole in a vertical plate with the aid of laser radiation at a surface temperature not exceeding the boiling point is analysed neglecting the vapour pressure. The mechanism of the degradation of the liquid layer involving a reduction of its thickness, as a result of the redistribution of the molten mass owing to the operation of the force of gravity and of thermocapillary convection, is examined. The theoretical dependence of the critical size of the molten zone on the plate thickness is obtained and a comparison is made with experimental data.

  3. Brilliant radiation sources by laser-plasma accelerators and optical undulators

    Energy Technology Data Exchange (ETDEWEB)

    Debus, Alexander

    2012-09-06

    This thesis investigates the use of high-power lasers for synchrotron radiation sources with high brilliance, from the EUV to the hard X-ray spectral range. Hereby lasers accelerate electrons by laser-wakefield acceleration (LWFA), act as optical undulators, or both. Experimental evidence shows for the first time that LWFA electron bunches are shorter than the driving laser and have a length scale comparable to the plasma wavelength. Furthermore, a first proof of principle experiment demonstrates that LWFA electrons can be exploited to generate undulator radiation. Building upon these experimental findings, as well as extensive numerical simulations of Thomson scattering, the theoretical foundations of a novel interaction geometry for laser-matter interaction are developed. This new method is very general and when tailored towards relativistically moving targets not being limited by the focusability (Rayleigh length) of the laser, while it does not require a waveguide. In a theoretical investigation of Thomson scattering, the optical analogue of undulator radiation, the limits of Thomson sources in scaling towards higher peak brilliances are highlighted. This leads to a novel method for generating brilliant, highly tunable X-ray sources, which is highly energy efficient by circumventing the laser Rayleigh limit through a novel traveling-wave Thomson scattering (TWTS) geometry. This new method suggests increases in X-ray photon yields of 2-3 orders of magnitudes using existing lasers and a way towards efficient, optical undulators to drive a free-electron laser. The results presented here extend far beyond the scope of this work. The possibility to use lasers as particle accelerators, as well as optical undulators, leads to very compact and energy efficient synchrotron sources. The resulting monoenergetic radiation of high brilliance in a range from extreme ultraviolet (EUV) to hard X-ray radiation is of fundamental importance for basic research, medical

  4. Dichromatic and monochromatic laser radiation effects on survival and morphology of Pantoea agglomerans

    Science.gov (United States)

    Thomé, A. M. C.; Souza, B. P.; Mendes, J. P. M.; Soares, L. C.; Trajano, E. T. L.; Fonseca, A. S.

    2017-05-01

    Despite the beneficial effects of low-level lasers on wound healing, their application for treatment of infected injuries is controversial because low-level lasers could stimulate bacterial growth exacerbating the infectious process. Thus, the aim of this work was to evaluate in vitro effects of low-level lasers on survival, morphology and cell aggregation of Pantoea agglomerans. P. agglomerans samples were isolated from human pressure injuries and cultures were exposed to low-level monochromatic and simultaneous dichromatic laser radiation to study the survival, cell aggregation, filamentation and morphology of bacterial cells in exponential and stationary growth phases. Fluence, wavelength and emission mode were those used in therapeutic protocols for wound healing. Data show no changes in morphology and cell aggregation, but dichromatic laser radiation decreased bacterial survival in exponential growth phase and monochromatic red and infrared lasers increased bacterial survival at the same fluence. Simultaneous dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation and simultaneous dichromatic laser could be the option for treatment of infected pressure injuries by Pantoea agglomerans.

  5. INTERACTION OF LASER RADIATION WITH MATTER: Influence of a target on operation of a pulsed CO2 laser emitting microsecond pulses

    Science.gov (United States)

    Baranov, V. Yu; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1987-12-01

    The profile of pulses emitted by a TEA CO2 laser with an unstable resonator changed as a result of interaction of laser radiation with the surface of a metal in the presence of a breakdown plasma. This influence of a target on laser operation and its possible applications in laser processing of materials are analyzed.

  6. Modelling of micromachining of human tooth enamel by erbium laser radiation

    Science.gov (United States)

    Belikov, A. V.; Skrypnik, A. V.; Shatilova, K. V.

    2014-08-01

    We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained.

  7. Solar radiation pumped solid state of lasers for Solar Power Satellites

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Ruiyi [New Jersey (United States)

    2000-07-01

    The Laser Solar Power Satellites (L-SPS) is the most promising way to overcome global energy and environmental and economical problems. The purpose was to use the favorable combination of solar radiation, modern lasers and the extremely promising phenomenon Optical Phase Conjugation (OPC). Direct conversion of solar energy to energy of a high-power laser beam has the advantage of high efficiency and precise energy transportation. In this paper, direct solar radiation pumping of the laser is compared with the pumping using the intermediate stage of the conversion of the solar radiation in electrical energy. Possible solid-state lasers that can be used in L-SPS are also discussed (including optical system and cooling system). [Spanish] Los Satelites de Energia Solar Laser (L-SPS) son la forma mas prometedora para contrarrestar los problemas globales de energia, ambientales y problemas economicos. El proposito fue el de usar la combinacion favorable de radiacion solar, laseres modernos y el fenomeno extremadamente prometedor de conjugacion de fase optica (OPC). La conversion directa de energia solar a energia de un rayo laser de alta potencia tiene la ventaja de la alta eficiencia y precision de la transportacion de la energia. En este documento la radiacion solar directa impulsada por el laser se compara con la impulsion usando el estado intermedio de conversion de la radiacion solar en energia electrica. Tambien se analizan los posibles laseres de estado solido que pueden usarse en L-SPS (incluyendo el sistema optico y el sistema de enfriamiento).

  8. Propagation of the radiation of laser instruments in road telematics systems

    Science.gov (United States)

    Palys, Marek

    2003-10-01

    In this paper I would like to present the necessity of taking into account a deformation of laser radiation in the real atmosphere while conducting measurements providing data for Intelligent Transport Systems.

  9. High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps

    Science.gov (United States)

    Masoud, N. M.; Murnick, D. E.

    2013-12-01

    A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

  10. High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps

    Energy Technology Data Exchange (ETDEWEB)

    Masoud, N. M. [UV Solutions Inc, Newark, New Jersey 07103 (United States); Physics and Chemistry Department, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202 (United States); Murnick, D. E. [UV Solutions Inc, Newark, New Jersey 07103 (United States); Department of Physics, Rutgers University, Newark, New Jersey 07102 (United States)

    2013-12-15

    A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

  11. [Effects of laser radiation on the periodontium. An animal model approach. Effects of usual radiation dosage].

    Science.gov (United States)

    Noguerol Rodriguez, B; Alandez Chamorro, J; Cañizares Garcia, J; Campos Muñoz, A; Sicilia Felechosa, A

    1989-05-01

    Twenty four albino mice of forty days old were selected. Twelve forty days old albino mice were irradiated with a Helium-Neon laser source, dose of 10.50566 Jul/cm2. They were divided in two groups according to time of animal sacrifice (immediately after irradiation and ten days after). As control were used twelve mice using the same time as the experimental groups, but without radiation. T.E.M. ultrathin sections showed alteration only in the conjunctiva and in the bone tissues, but not in the epithelial tissue. The bone showed two osteocyte population according to their response to irradiation. The first population showed characteristic comparable with the controls, and the second showed alterations suggestive of a degenerative process. The connective tissue also showed two fibroblasts populations, the first showed signs of a big synthesizing activity, and the second, degenerative signs. The first fibroblast population appeared in the animals sacrificed immediately after irradiation.

  12. Effects of radiation reaction in the interaction between cluster media and high intensity lasers in the radiation dominant regime

    Science.gov (United States)

    Iwata, Natsumi; Nagatomo, Hideo; Fukuda, Yuji; Matsui, Ryutaro; Kishimoto, Yasuaki

    2016-06-01

    Interaction between media composed of clusters and high intensity lasers in the radiation dominant regime, i.e., intensity of 10 22 - 23 W / cm 2 , is studied based on the particle-in-cell simulation that includes the radiation reaction. By introducing target materials that have the same total mass but different internal structures, i.e., uniform plasma and cluster media with different cluster radii, we investigate the effect of the internal structure on the interaction dynamics, high energy radiation emission, and its reaction. Intense radiation emission is found in the cluster media where electrons exhibit non-ballistic motions suffering from strong accelerations by both the penetrated laser field and charge separation field of clusters. As a result, the clustered structure increases the energy conversion into high energy radiations significantly at the expense of the conversion into particles, while the total absorption rate into radiation and particles remains unchanged from the absorption rate into particles in the case without radiation reaction. The maximum ion energy achieved in the interaction with cluster media is found to be decreased through the radiation reaction to electrons into the same level with that achieved in the interaction with the uniform plasma. The clustered structure thus enhances high energy radiation emission rather than the ion acceleration in the considered intensity regime.

  13. Therapy of patients with osteoarthritis with low energy laser radiation

    Directory of Open Access Journals (Sweden)

    L. V. Vasiljeva

    2008-01-01

    Full Text Available Objective. To assess influence oflow energy laser radiation (LELR on glycosaminoglycan (GAG and vitamin С level in pts with osteoarthritis (OA. Material and methods. 82 pts with primary OA and 25 healthy volunteers signed informed consent were included in an open randomized prospective 12-month study. Inclusion criteria: unsatisfactory effect of previous drug therapy (DT, stable NSAID dose 3-5 days before and during LELR course, absence of comorbid hepatic and kidney diseases in stage of functional decompensation, malignant diseases, exclusion therapy influencing microcirculation, exercise therapy, physical therapy. Intra-articular injections were not done during 3 months before the study. Pts were divided into 2 groups. Group 1 received complex DT and LELR, group 2 - DT. clinical and laboratory parameters were used as efficacy measures. Statistical analysis was performed on personal computer IBM PC (OS — Windows EP Home Edition with Microsoft office and STATISTICA 6.0 programs. Results. Analysis of the results showed significant improvement of most measures in comparison with traditional DT. LELR administration allowed to decrease chondroprotector and NSAID doses. Vitamin С decrease in serum of OA pts may be a risk factor of development and progression of this disease.

  14. Intracavity scanning of the radiation of an electric-discharge nonchain DF laser

    Science.gov (United States)

    Alekseev, V. N.; Liber, V. I.; Kotylev, V. N.; Fonin, V. M.

    2005-04-01

    This paper presents the results of a study of the possibility of using an electrically controlled space-time light modulator based on the transparent electrooptic ceramic PLZT for intracavity scanning of the radiation of a chemical nonchain DF laser (lasing-wavelength range 3.5-4.0 μm). The radiation pulses are scanned in space in the pulsed and pulse-frequency operating modes of the laser.

  15. One-dimensional modelling of DBDs in NeXe mixtures for excimer lamps

    OpenAIRE

    Belasri, A; Khodja, K; Bendella, S; Harrache, Z

    2010-01-01

    Abstract Dielectric barrier discharges (DBDs) are a promising technology for high-intensity sources of specific UV and VUV radiation. In this work, the microdischarge dynamics in DBDs for Ne?Xe mixtures under the close conditions of excimer lamp working has been investigated. The computer model including the cathode fall, the positive column and the dielectric is composed of two coupled sub-models. The first submodel describes the electrical properties of the discharge and is based on a fl...

  16. Evolution analysis of EUV radiation from laser-produced tin plasmas based on a radiation hydrodynamics model.

    Science.gov (United States)

    Su, M G; Min, Q; Cao, S Q; Sun, D X; Hayden, P; O'Sullivan, G; Dong, C Z

    2017-03-23

    One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging.

  17. Reflection of Carbon Dioxide (CO 2 ) laser radiation from the theatre ...

    African Journals Online (AJOL)

    This work has investigated the power of both specular and diffusely reflected beams of CO2 laser radiation from metallic and non-metallic surfaces of an operating theatre including surgical instruments (specula) and different samples of wall paints in theatre 6 of the Aberdeen Royal Infirmary, U.K. where the CO2 laser ...

  18. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    September 2000 physics pp. 405–412. Third harmonic generation of CO2 laser radiation in. AgGaSe2 crystal. GOPAL C BHAR, PATHIK KUMBHAKAR. ½. , D V SATYANARAYANA. ¾. ,. N S N BANERJEE. ¾. , U NUNDY. ¾ and C G CHAO. ¿. Laser Laboratory, Physics Department, Burdwan University, Burdwan 713 104, ...

  19. Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors

    Science.gov (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, V. A.

    1980-09-01

    The design and operation of an iodine photodissociation laser, pumped by radiation from magnetoplasma compressors, are described. The laser uses a closed-circulation system with C3F7I as the working gas. Repetitive-pulse operation has been achieved with an interval between pulses of 1 minute, a lasing energy of 110 J, and a pulse duration of 30 microseconds.

  20. Combined Impact of Gamma and Laser Radiation on Peripheral Blood of Rats in vivo

    Science.gov (United States)

    Zalesskaya, G. A.; Batay, L. E.; Koshlan, I. V.; Nasek, V. M.; Zilberman, R. D.; Milevich, T. I.; Govorun, R. D.; Koshlan, N. A.; Blaga, P.

    2017-11-01

    The impact of γ radiation of 137Cs (doses of 1 and 3 Gy), low-intensity laser radiation (λ = 670 nm, 5.3 or 10.6 J/cm2) as well as the influence of consecutive laser and γ radiation on peripheral blood and blood cells (erythrocytes, leukocytes, lymphocytes, granulocytes) were studied by analyzing the number of blood cells, blood absorption spectra, and activity of antioxidant defense enzymes. Two series of experiments were performed on four groups of rats. The rats of the control group (group 1) were not exposed to γ or laser radiation. In the experimental groups, single irradiation of the whole body of rats with γ radiation (group 2), three- or four-day over-vein irradiation of blood in the tail vein by low-intensity laser radiation (group 3), and successive three- or four-day irradiation of blood by laser and then a single irradiation of the whole body with γ radiation (group 4) were performed. It was shown that changes of the blood cell content in the experimental groups are accompanied by changes in the spectral characteristics of the blood and the activity of antioxidant defense enzymes. The radioprotective effect of low-intensity laser radiation is manifested as an increase in the average number of leukocytes and lymphocytes in the group as compared with the postradiation, as well as an increase in the activity of antioxidant protection enzymes. The possibility of using low-intensity optical radiation for correction of hematological disorders caused by ionizing radiation is discussed.

  1. Ablation of oral mucosa by erbium:YAG and holmium:YAG laser radiation

    Science.gov (United States)

    Nuebler-Moritz, Michael; Gutknecht, Norbert; Sailer, Hermann F.; Hering, Peter; Prettl, Wilhelm

    1997-05-01

    The in vitro tissue ablation characteristics of two pulsed mid-infrared lasers were studied, especially, with the intent to evaluate photomechanical and photothermal side effects. The Erbium:YAG laser emitted radiation at 2.94 micrometers in a spiking mode. The free-running beam from the laser was focused onto freshly-excised porcine samples via a 108-mm sapphire lens. The spot size was determined by a photosensitive metallic foil. The Holmium:YAG laser emitted radiation at 2.10 micrometers . The radiation was coupled to a 400- micrometers core quartz fiber. Both lasers were operated at 5 Hz, and 6 pulses were delivered to each porcine specimen using 'dry' and 'wet' ablation mode, respectively. After irradiation, the samples were investigated by means of light and scanning electron microscopy. The results of this survey indicate that both laser types ablate porcine oral mucosa efficiently. The Er:YAG laser produces less surrounding mechanical and thermal damage. In contrast to safe and suitable optical fibers available for the Ho:YAG laser, fiber optical delivery systems for the Er:YAG laser are still in the development phase. Nevertheless, current research work in this field seems promising and the near future may hold an adequate optical transmission systems for the delivery of both wavelengths, 2.10 micrometers and 2.94 micrometers , in order to provide on the one hand atraumatic ablation and on the other hand sufficient hemostasis.

  2. Radiation-Reaction Trapping of Electrons in Extreme Laser Fields

    CERN Document Server

    Ji, L L; Kostyukov, I Yu; Shen, B F; Akli, K

    2014-01-01

    proposed analysis shows that the threshold of laser field amplitude for RRT is approximately the cubic root of laser wavelength over classical electron radius. Because of the pinching effect of the trapped electron bunch, the required laser intensity for RRT can be further reduced.

  3. Laser-induced fluorescence imaging of coronary arteries for open-heart surgery applications

    Science.gov (United States)

    Taylor, Roderick S.; Gladysz, D.; Brown, Derek W.; Higginson, Lyall A. J.

    1991-07-01

    A technique utilizing laser induced fluorescence has been developed to obtain direct real-time imaging of the coronary artery network for open heart surgery applications. Both excimer pumped dye and cw argon-ion laser radiation transmitted through a fused silica fiber were used as laser sources to irradiate swine, bovine, and human cadaver hearts whose coronary arteries had been injected with strongly fluorescent dyes. The laser induces fluorescence originating from within the coronary arteries and detected by the surgeon's eye, allows the entire coronary network to be directly viewed. A comparison between laser induced fluorescence and the use of direct visual inspection of arteries following injection of the dye Cardio-Green(R) as well as conventional thermal imaging is presented. The limitations imposed on each technique by layers of fat on top of the coronary arteries are also described. The possibility of using these techniques to detect mechanical or laser beam perforations during laser endarterectomy procedures is discussed.

  4. Particularities of interaction of CO sub 2 -laser radiation with oxide materials

    CERN Document Server

    Salikhov, T P

    2002-01-01

    The results of experimental investigation of vapor phase influence on the interaction parameters of the infrared laser radiation with oxide materials (Al sub 2 O sub 3 , ZrO sub 2 , CeO sub 2) have been presented. A phenomenon of laser radiation by the samples investigated under laser heating has been experimentally discovered for the first time. This phenomenon connected with forming of the stable vapor shell above the irradiated samples was expressed as a sharp drop in temperature on the heating curve and called as an absorption flash. (author)

  5. Investigation of damage to metals by pulsed CO2 laser radiation

    Science.gov (United States)

    Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Senatorov, Yu M.

    1981-10-01

    A study was made of the physical mechanism involved in piercing holes in metallic plates, using CO2 laser radiation. It was established experimentally that the energy consumed in removing a unit volume of a metal has a minimum, depending on the duration and energy of the laser pulse. An explanation is proposed for the laws governing this behavior, based on ideas of the ejection of liquid from a crater by the vapor pressure of the material. The effect on the interaction efficiency of the absorption of laser radiation in the plasma jet is taken into account.

  6. Formation of luminescent emitters by intense laser radiation in transparent media

    Science.gov (United States)

    Martynovich, E. F.; Kuznetsov, A. V.; Kirpichnikov, A. V.; Pestryakov, Efim V.; Bagayev, Sergei N.

    2013-05-01

    The formation of luminescent colour centres in the LiF crystal under the action of femtosecond pulses of the first harmonic of a Ti : sapphire laser is experimentally studied. The experiments were carried out at low- and high-aperture focusing of radiation. The effect of both single pulses and multi-pulse trains on the crystals was studied. Channelling of laser radiation in the waveguides, induced by the filaments of the first pulses, is found. The multiphoton mechanism of interband absorption is confirmed. The optimal conditions of laser impact for designing luminescent emitters in the LiF crystal are determined.

  7. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

    Directory of Open Access Journals (Sweden)

    K.S. Canuto

    2015-01-01

    Full Text Available Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia coli cells that were exposed to ultraviolet C (UVC radiation. Exponential and stationary wild-type and uvrA-deficient E. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC. Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out.

  8. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

    Energy Technology Data Exchange (ETDEWEB)

    Canuto, K.S.; Guimaraes, O.R.; Geller, M. [Centro Universitario Serra dos Orgaos, Teresopolis, RJ (Brazil). Centro de Ciencias da Saude; Sergio, L.P.S. [Instituto de Biologia Roberto Alcantara Gomes, Rio de Janeiro, RJ (Brazil). Departamento de Biofisica e Biometria; Paoli, F. [Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, MG (Brazil). Departamento de Morfologia; Fonseca, A.S., E-mail: adnfonseca@ig.com.br [Universidade Federal do Estado do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Departamento de Ciencias Fisiologicas

    2015-10-15

    Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia coli cells that were exposed to ultraviolet C (UVC) radiation. Exponential and stationary wild-type and uvrA-deficient E. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC). Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out. (author)

  9. Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry

    Science.gov (United States)

    Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed

    2016-01-01

    Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. PMID:26642047

  10. Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry.

    Science.gov (United States)

    Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed

    2016-01-01

    Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. © 2015 S. Karger AG, Basel.

  11. Selective irradiation of radicals for biomedical treatment using vacuum ultraviolet light from an excimer lamp

    Science.gov (United States)

    Ono, Ryo; Tokumitsu, Yusuke; Zen, Shungo; Yonemori, Seiya

    2014-10-01

    In plasma medicine, radicals are considered to play important roles. However, the medical effect of each radical, such as OH and O, is unknown. To examine the effect of each radical, selective production of radicals is needed. We developed selective production of radicals for biomedical treatment using a vacuum ultraviolet (VUV) light emitted from an excimer lamp. Selective irradiation of OH radicals can be achieved by irradiating the 172-nm VUV light from a Xe2 excimer lamp to a humid helium flow in a quartz tube. The water molecules are strongly photodissociated by the VUV light to produce OH radicals. A photochemical simulation for the selective OH production is developed to calculate the OH density. The calculated OH density is compared with OH density measured using laser-induced fluorescence (LIF). Selective production of other radicals than OH is also discussed.

  12. Effect of laser radiation on multi-wall carbon nanotubes: study of shell structure and immobilization process

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, Enikoe, E-mail: egyorgy@icmab.es; Perez del Pino, Angel [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain); Roqueta, Jaume; Ballesteros, Belen [Centro de Investigaciones en Nanociencia y Nanotecnologia, Consejo Superior de Investigaciones Cientificas (CIN2-CSIC) (Spain); Cabana, Laura; Tobias, Gerard [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain)

    2013-08-15

    Multi-wall carbon nanotubes (MWCNTs) with diameters between 10 and 15 nm were transferred and immobilized onto SiO{sub 2} glass substrates by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE). Toluene was chosen as solvent material for the preparation of the composite MAPLE targets. An UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 25 ns, {nu} = 10 Hz) excimer laser source was used for the irradiation experiments. The effects of incident laser fluence on the structure of the laser transferred MWCNTs was investigated by high resolution transmission electron microscopy and Raman spectroscopy. The surface morphology of the laser processed MWCNTs was investigated by field emission scanning electron microscopy and atomic force microscopy in acoustic (dynamic) configuration. Network-like structures constituted by individual nanotubes and nanotube bundles were created onto solid substrates. Changes in the nanotubes' shell structure can be induced through the tuning of the laser fluence value incident onto the composite MAPLE targets.

  13. Radiation Dose Measurement for High-Intensity Laser Interactions with Solid Targets at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Taiee [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-09-25

    A systematic study of photon and neutron radiation doses generated in high-intensity laser-solid interactions is underway at SLAC National Accelerator Laboratory. We found that these laser-solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Additionally, radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser-solid experiments at SLAC MEC in 2014 with peak intensity between 1018 to 7.1x1019 W/cm2 are presented.

  14. Two-frequency picosecond laser based on composite vanadate crystals with {sigma}-polarised radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sirotkin, A A; Sadovskiy, S P; Garnov, Sergei V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2013-07-31

    A two-frequency picosecond laser based on {alpha}-cut Nd:YVO{sub 4}-YVO{sub 4} composite vanadate crystals is experimentally studied for the s-polarised radiation at the {sup 4}F{sub 3/2} - {sup 4}I{sub 11/2} transition with frequency tuning using Fabry-Perot etalons of different thickness. The difference between the radiation wavelengths was tuned within the range of 1.2-4.4 nm. In the mode-locking regime, the two-frequency radiation power was 280 mW at an absorbed pump power of 12 W. (lasers)

  15. Laser pumped light emitting diodes as broad area sources of coherent radiation

    Science.gov (United States)

    Rahman, Faiz; Sorel, Marc

    2006-08-01

    This paper describes the use of large area light emitting diodes, pumped with various laser sources, as extended area emitters of coherent radiation. The photon recycling takes place through the intermediary of electron hole pair formation and subsequent stimulated recombination. It is possible to generate both spontaneous and stimulated emission together and the two channels are then independent of each other. This allows the generation of a mixture of coherent and non-coherent radiation in any desired proportion. The technique described is a broad-band resonant process with diffusive feedback and can be used for generating non-collimated laser radiation for a variety of applications.

  16. Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits

    Science.gov (United States)

    2017-03-01

    Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits Zachary E. Fleetwood and John D. Cressler School of...platforms intended for radiation - intense applications and spaceflight hardware considerations. A number of new radio frequency (RF) studies have...extended the knowledge base of applying radiation -hardening-by- design (RHBD) to SiGe Heterojunction Bipolar Transistor (HBT) circuits. Other research

  17. A cesium plasma TELEC device for conversion of laser radiation to electric power

    Science.gov (United States)

    Britt, E. J.; Rasor, N. S.; Lee, G.; Billman, K. W.

    1978-01-01

    Tests of the thermoelectronic laser energy converter (TELEC) concept are reported. This device has been devised as a means to convert high-average-power laser radiation into electrical energy, a crucial element in any space laser power transmission scheme using the available high-power/efficiency infrared lasers. Theoretical calculations, based upon inverse bremsstrahlung absorption in a cesium plasma, indicate internal conversion efficiency up to 50% with an overall system efficiency of 42%. The experiments reported were made with a test cell designed to confirm the theoretical model rather than demonstrate efficiency; 10.6-micron laser-beam absorption was limited to about 0.001 of the incident beam by the short absorption region. Nevertheless, confirmatory results were obtained, and the conversion of absorbed radiation to electric power is estimated to be near 10%.

  18. Combination of fiber-guided pulsed erbium and holmium laser radiation for tissue ablation under water.

    Science.gov (United States)

    Pratisto, H; Frenz, M; Ith, M; Altermatt, H J; Jansen, E D; Weber, H P

    1996-07-01

    Because of the high absorption of near-infrared laser radiation in biological tissue, erbium lasers and holmium lasers emitting at 3 and 2 µm, respectively, have been proven to have optimal qualities for cutting or welding and coagulating tissue. To combine the advantages of both wavelengths, we realized a multiwavelength laser system by simultaneously guiding erbium and holmium laser radiation by means of a single zirconium fluoride (ZrF(4)) fiber. Laser-induced channel formation in water and poly(acrylamide) gel was investigated by the use of a time-resolved flash-photography setup, while pressure transients were recorded simultaneously with a needle hydrophone. The shapes and depths of vapor channels produced in water and in a submerged gel after single erbium and after combination erbium-holmium radiation delivered by means of a 400-µm ZrF(4) fiber were measured. Transmission measurements were performed to determine the amount of pulse energy available for tissue ablation. The effects of laser wavelength and the delay time between pulses of different wavelengths on the photomechanical and photothermal responses of meniscal tissue were evaluated in vitro by the use of histology. It was observed that the use of a short (200-µs, 100-mJ) holmium laser pulse as a prepulse to generate a vapor bubble through which the ablating erbium laser pulse can be transmitted (delay time, 100 µs) increases the cutting depth in meniscus from 450 to 1120 µm as compared with the depth following a single erbium pulse. The results indicate that a combination of erbium and holmium laser radiation precisely and efficiently cuts tissue under water with 20-50-µm collateral tissue damage.

  19. Stress relaxation and cartilage shaping under laser radiation

    Science.gov (United States)

    Sobol, Emil N.; Sviridov, Alexander P.; Bagratashvili, Victor N.; Omelchenko, Alexander I.; Ovchinnikov, Yuriy M.; Shekhter, Anatoliy B.; Downes, S.; Howdle, Steven; Jones, Nicholas; Lowe, J.

    1996-05-01

    The problem of a purposeful change of the shape of cartilage is of great importance for otolaryngology, orthopaedics, and plastic surgery. In 1992 we have found a possibility of controlled shaping of cartilage under moderate laser heating. This paper presents new results in studies of that phenomenon. We have measured temperature and stress in a tissue undergoing to irradiation with a Holmium laser. Study of cartilage structure allowed us to find conditions for laser shaping without pronounced alterations in the structure of matrix.

  20. Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Li, E-mail: ligan0001@gmail.com; Mousen, Cheng; Xiaokang, Li [College of Aerospace Science and Engineering, National University of Defense Technology, Changsha (China)

    2014-03-15

    In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

  1. Regeneration of spine disc and joint cartilages under temporal and space modulated laser radiation

    Science.gov (United States)

    Sobol, E.; Shekhter, A.; Baskov, A.; Baskov, V.; Baum, O.; Borchshenko, I.; Golubev, V.; Guller, A.; Kolyshev, I.; Omeltchenko, A.; Sviridov, A.; Zakharkina, O.

    2009-02-01

    The effect of laser radiation on the generation of hyaline cartilage in spine disc and joints has been demonstrated. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reconstruction of spine discs. Possible mechanisms of laser-induced regeneration include: (1) Space and temporary modulated laser beam induces nonhomogeneous and pulse repetitive thermal expansion and stress in the irradiated zone of cartilage. Mechanical effect due to controllable thermal expansion of the tissue and micro and nano gas bubbles formation in the course of the moderate (up to 45-50 oC) heating of the NP activate biological cells (chondrocytes) and promote cartilage regeneration. (2) Nondestructive laser radiation leads to the formation of nano and micro-pores in cartilage matrix. That promotes water permeability and increases the feeding of biological cells. Results provide the scientific and engineering basis for the novel low-invasive laser procedures to be used in orthopedics for the treatment cartilages of spine and joints. The technology and equipment for laser reconstruction of spine discs have been tested first on animals, and then in a clinical trial. Since 2001 the laser reconstruction of intervertebral discs have been performed for 340 patients with chronic symptoms of low back or neck pain who failed to improve with non-operative care. Substantial relief of back pain was obtained in 90% of patients treated who returned to their daily activities. The experiments on reparation of the defects in articular cartilage of the porcine joints under temporal and spase modulated laser radiation have shown promising results.

  2. A new method and device of aligning patient setup lasers in radiation therapy.

    Science.gov (United States)

    Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong

    2016-01-08

    The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.

  3. Development of Laser Plasma X-ray Microbeam Irradiation System and Radiation Biological Application

    Science.gov (United States)

    Sato, Katsutoshi; Nishikino, Masaharu; Numasaki, Hodaka; Kawachi, Tetsuya; Teshima, Teruki; Nishimura, Hiroaki

    Laser plasma x-ray source has the features such as ultra short pulse, high brilliance, monochromaticity, and focusing ability. These features are excellent compared with conventional x-ray source. In order to apply the laser plasma x-ray source to the biomedical study and to more closely research the radiobilogical responce of the cancer cell such as radiation induced bystander effect, we have developed x-ray microbeam system using laser plasma x-ray source. The absorbed dose of laser plasma x-ray was estimated with Gafchromic EBT film and DNA double strand breaks on the cells were detected by immunofluorescence staining. When the cells were irradiated with laser plasma x-ray, the circular regions existing γ-H2AX positive cells were clearly identified. The usefulness of the laser plasma x-ray on the radiobiological study was proved in this research.

  4. LASERS: Characteristics of the radiation of an Nd:YAG laser with an intracavity spatiotemporal modulator based on a PLZT electro-optical ceramic

    Science.gov (United States)

    Alekseev, V. N.; Kotylev, V. N.; Liber, V. I.

    1999-06-01

    The characteristics of the radiation of a laser with intracavity scanning with the aid of electrically controlled spatiotemporal modulators based on a transparent electro-optical PLZT ceramic were investigated. The possibility of the generation of packets of single pulses of scanning laser radiation with a repetition frequency up to 100 kHz, and up to 10 kHz under the conditions of continuous flashlamp pumping with an intracavity spatiotemporal modulator is demonstrated. Possible applications of the laser are discussed.

  5. Laser-plasma SXR/EUV sources: adjustment of radiation parameters for specific applications

    Science.gov (United States)

    Bartnik, A.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Kostecki, J.; Szczurek, A.; Szczurek, M.; Wachulak, P.; Wegrzyński, Ł.

    2014-12-01

    In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

  6. Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method

    CERN Document Server

    Nechayev, Sergey; Baldo, Marc A; Rotschild, Carmel

    2016-01-01

    High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump ...

  7. Stimulated emission of ultraviolet radiation by vapors of complex molecules

    Energy Technology Data Exchange (ETDEWEB)

    Barkova, L.A.; Gruzinskii, V.V.; Danilova, V.I.; Degtyarenko, K.M.; Kopylova, T.N.; Kuznetsov, A.L.

    1981-08-01

    Lasing was observed in vapors of new organic compounds: para-terphenyl, 2-phenylbenzoxazole, 2-(n-tolyl) benzoxazole, 2-(n-methoxyphenyl) benzoxazole, 2-(n-dimethylaminophenyl) benzoxazole, 2-biphenylbenzoxazole, 2-(..cap alpha..-naphthyl) benzoxazole, and also 1,4-di(n-phenylethynyl) benzole, and para-quaterphenyl pumped transversely by XeCl excimer laser radiation at lambda/sub p/ = 308 nm. The lasing bands without tuning covered the 330--370 nm range. The shortest-wavelength maximum (333.5 nm) was observed for 2-(n-methoxyphenyl) benzoxazole. An analysis was made of the lasing ability of the molecules.

  8. New frontier of laser particle acceleration: driving protons to 80 MeV by radiation pressure

    CERN Document Server

    Kim, I Jong; Kim, Chul Min; Kim, Hyung Taek; Lee, Chang-Lyoul; Choi, Il Woo; Singhal, Himanshu; Sung, Jae Hee; Lee, Seong Ku; Lee, Hwang Woon; Nickles, Peter V; Jeong, Tae Moon; Nam, Chang Hee

    2014-01-01

    The radiation pressure acceleration (RPA) of charged particles has been considered a challenging task in laser particle acceleration. Laser-driven proton/ion acceleration has attracted considerable interests due to its underlying physics and potential for applications such as high-energy density physics, ultrafast radiography, and cancer therapy. Among critical issues to overcome the biggest challenge is to produce energetic protons using an efficient acceleration mechanism. The proton acceleration by radiation pressure is considerably more efficient than the conventional target normal sheath acceleration driven by expanding hot electrons. Here we report the generation of 80-MeV proton beams achieved by applying 30-fs circularly polarized laser pulses with an intensity of 6.1 x 1020 W/cm2 to ultrathin targets. The radiation pressure acceleration was confirmed from the obtained optimal target thickness, quadratic energy scaling, polarization dependence, and 3D-PIC simulations. We expect this fast energy scalin...

  9. Quantum mechanical theory of collisional ionization in the presence of intense laser radiation

    Science.gov (United States)

    Bellum, J. C.; George, T. F.

    1978-01-01

    The paper presents a quantum mechanical formalism for treating ionizing collisions occurring in the presence of an intense laser field. Both the intense laser radiation and the internal electronic continuum states associated with the emitted electrons are rigorously taken into account by combining discretization techniques with expansions in terms of electronic-field representations for the quasi-molecule-plus-photon system. The procedure leads to a coupled-channel description of the heavy-particle dynamics which involves effective electronic-field potential surfaces and continua. It is suggested that laser-influenced ionizing collisions can be studied to verify the effects of intense laser radiation on inelastic collisional processes. Calculation procedures for electronic transition dipole matrix elements between discrete and continuum electronic states are outlined.

  10. Reduction of collisional-radiative models for laser-produced argon plasmas

    Science.gov (United States)

    Abrantes, Richard June; Karagozian, Ann; Le, Hai

    2016-10-01

    The formation of a laser-induced plasma involves a variety of physical phenomena stemming from the laser-plasma interaction. A thorough understanding of these processes encourages improvement and innovation for many applications. In this work, we aim to computationally reduce a previously-developed collisional-radiative (CR) model constructed from the LANL database, which includes all of the relevant collisional and radiative processes for all the ionic stages of argon. The laser is coupled to the plasma via multiphoton ionization and inverse Bremsstrahlung, processes important for electron production and heating. The use of the CR model allows us to identify dominant mechanisms responsible for initial breakdown of the gas and thermal equilibriation processes. The results are compared with experimental data from laser-induced breakdown experiments. Research supported by the AFOSR.

  11. Electromagnetic radiations from laser interaction with gas-filled Hohlraum

    Science.gov (United States)

    Yang, Ming; Yang, Yongmei; Li, Tingshuai; Yi, Tao; Wang, Chuanke; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun

    2018-01-01

    The emission of intensive electromagnetic pulse (EMP) due to laser-target interactions at the ShenGuang-III laser facility has been evaluated by probes. EMP signals measured using the small discone antennas demonstrated two variation trends including a bilateral oscillation wave and a unilateral oscillation wave. The new trend of unilateral oscillation could be attributed to the hohlraum structure and low-Z gas in the hohlraum. The EMP waveform showed multiple peaks when the gas-filled hohlraum was shot by the high-power laser. Comparing the EMP signals with the verification of stimulated Raman scattering energy and hard x-ray energy spectrum, we found that the intensity of EMP signals decreased with the increase of the hohlraum size. The current results are expected to offer preliminary information to study physical processes on laser injecting gas-filled hohlraums in the National Ignition Facility implementation.

  12. Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Zhou, Y., E-mail: nzhou@uwaterloo.ca [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Duley, W. W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2015-12-14

    Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

  13. The role of laser radiation therapy in maxillary sinusitis

    OpenAIRE

    Isser, D. K.; Sett, S.; Saha, B.P.

    2002-01-01

    Efficacy of prescribed noninvasive & invasive types of treatment of maxillary sinusitis has been compared with low-dose LASER therapy (LLT). After going through the observations of different authors on the therapeutic role of LLT (GaA1AS-LASER) in non-ENT infective diseases, its use in ‘sinusitis’ has been adjudged. Such type of study-report has not been found by us in the literatures, available to us.

  14. Influence of laser radiation on acceleration of postextraction wound healing

    Science.gov (United States)

    Grzesiak-Janas, Grazyna; Kobos, Jozef

    1997-10-01

    The investigations included 50 patients who were subjected to extraction of two adjacent teeth because of chronic periodontal ligament inflammation using 2 percent lignocaine as an anaesthetic agent. One postextraction wound was irradiated with laser light, whereas the second one was left to be healed in a natural way. The use of laser beam accelerates postextraction wound healing on the basis of clinical and cytologic evaluation.

  15. Atmospheric propagation of high power laser radiation at different weather conditions

    OpenAIRE

    Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Handke, Jürgen

    2016-01-01

    Applications based on the propagation of high power laser radiation through the atmosphere are limited in range and effect, due to weather dependent beam wandering, beam deterioration, and scattering processes. Security and defense related application examples are countermeasures against hostile projectiles and the powering of satellites and aircrafts. For an examination of the correlations between weather condition and laser beam characteristics DLR operates at Lampoldshausen a 130 m long fr...

  16. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    ... for second harmonic and third harmonic generations are 6.3% and 2.4% respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 m, (20) line. A compact TEA CO2 laser source has been built in ...

  17. BRIEF COMMUNICATIONS: Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors

    Science.gov (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, Vladimir A.

    1980-09-01

    A study was made of the characteristics of an iodine photodissociation laser pumped by radiation emitted from magnetoplasma compressors. A closed system for circulating the working gas C3F7I was employed in this laser. Pulse-periodic operation with an interval of 1 min between the pulses was achieved; the output energy was 110 J and the pulse duration was 30 μ sec.

  18. The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.

    Science.gov (United States)

    Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria

    2014-09-01

    The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.

  19. Collisionless dissociation and isotopic enrichment of SF6 using high-powered CO2 laser radiation

    Science.gov (United States)

    Gower, M. C.; Billman, K. W.

    1977-01-01

    Dissociation of S-32F6 and the resultant isotopic enrichment of S-34F6 using high-powered CO2 laser radiation has been studied with higher experimental sensitivity than previously reported. Enrichment factors have been measured as a function of laser pulse number, wavelength, energy and time duration. A geometry independent dissociation cross section is introduced and measured values are presented. Threshold energy densities, below which no dissociation was observed, were also determined.

  20. He-Ne laser radiation in combined therapy of children's bronchial asthma

    Science.gov (United States)

    Zhilnikov, Dmitriy V.; Varavva, Andrey S.; Tarasova, Olga N.; Plaksina, Galina V.; Barybin, Vitaliy F.; Khlutkova, Svetlana N.

    2004-02-01

    In this paper the medical application of He-Ne lasers for the treatment of bronchial asthma is described. Research objective of this work was the development of a treatment method for children with bronchial asthman of heavy and medium-heavy forms, resistant to the base therapy, with the help of low-intensive laser radiation with wave length λ=0,63 μm.

  1. Exposure to laser radiation for creation of metal materials nanoporous structures

    Science.gov (United States)

    Murzin, Serguei P.

    2013-06-01

    Exposure to laser radiation for creation of nanoporous structures in the Cu-Zn alloy was investigated. It was established that exposure to laser pulse-periodic radiation with pulse repetition rate up to 5000 Hz makes it possible to form a nanoporous structure in the near-surface layer. The conditions of increase of area depth of such structures formation up to 40-45 μm were ascertained. The temperature and speed conditions which provide predominant channel-type nanopores formation with width of about 100 nm forming a nanoporous net were determined. This patented technology is a perspective for production of catalysts and microfiltration membranes.

  2. Research on a laser ultrasound method for testing the quality of a nuclear radiation protection structure

    Science.gov (United States)

    Zhang, Kuanshuang; Zhou, Zhenggan; Ma, Liyin

    2017-02-01

    Laser ultrasonics has been investigated for inspecting the quality of a nuclear radiation protection structure. A possibility is proposed to improve the signal to noise ratio (SNR) of a laser ultrasonic inspection system. Then, a nuclear radiation protection structure composed of an AISI 1045 steel sheet connected with a lead alloy sheet by using an epoxy resin adhesive was manufactured with simulated defects. A non-contact laser ultrasonic inspection system, where the measured signals were filtered using a wavelet threshold de-noising method, was established to conduct a series of experiments. The proposed signal processing method can significantly improve the SNR of measured laser ultrasound signals on a rough solid surface. Compared with the SNR of original ultrasonic signals measured in transmission and reflection, the SNR of processed transmitted and reflected signals is improved by 13.8 and 16.6 dB, respectively. Moreover, laser ultrasonic C-scans based on the transmission and pulse-echo method can detect the simulated de-bonding defects, and the relative deviation between the measured sizes and design values is below 9%. Therefore, the laser ultrasonic method combined with effective signal processing can achieve the quantitative characterization of de-bonding defects in nuclear radiation protection structures.

  3. UV and IR laser radiation's interaction with metal film and teflon surfaces

    Science.gov (United States)

    Fedenev, A. V.; Alekseev, S. B.; Goncharenko, I. M.; Koval', N. N.; Lipatov, E. I.; Orlovskii, V. M.; Shulepov, M. A.; Tarasenko, V. F.

    2003-04-01

    The interaction of Xe ([lambda] [similar] 1.73 [mu]m) and XeCl (0.308 [mu]m) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 ([lambda] [similar] 10.6 [mu]m), and Xe ([lambda] [similar] 1.73 [mu]m) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

  4. Biomolecular papain thin films growth by laser techniques.

    Science.gov (United States)

    György, Enikö; Santiso, Jose; Figueras, Albert; Socol, Gabriel; Mihailescu, Ion N

    2007-08-01

    Papain thin films were synthesised by matrix assisted and conventional pulsed laser deposition (PLD) techniques. The targets submitted to laser radiation consisted on a frozen composite obtained by dissolving the biomaterials in distilled water. For the deposition of the thin films by conventional PLD pressed biomaterial powder targets were submitted to laser irradiation. An UV KrF* excimer laser source was used in the experiments at 0.5 J/cm(2) incident fluence value, diminished one order of magnitude as compared to irradiation of inorganic materials. The surface morphology of the obtained thin films was studied by atomic force profilometry and atomic force microscopy. The investigations showed that the growth mode and surface quality of the deposited biomaterial thin films is strongly influenced by the target preparation procedure.

  5. Quantized form factor shift in the presence of free electron laser radiation

    CERN Document Server

    Fratini, F; Hayrapetyan, A G; Jänkälä, K; Amaro, P; Santos, J P

    2015-01-01

    In electron scattering, the target form factors contribute significantly to the diffraction pattern and carry information on the target electromagnetic charge distribution. Here we show that the presence of electromagnetic radiation, as intense as currently available in Free Electron Lasers, shifts the dependence of the target form factors by a quantity that depends on the number of photons absorbed or emitted by the electron as well as on the parameters of the electromagnetic radiation. As example, we show the impact of intense ultraviolet and soft X-ray radiation on elastic electron scattering by Ne-like Argon ion and by Xenon atom. We find that the shift brought by the radiation to the form factor is in the order of some percent. Our results may open up a new avenue to explore matter with the assistance of laser.

  6. Shear bond strength after Er:YAG laser radiation conditioning of enamel and dentin

    Science.gov (United States)

    Dostalova, Tatjana; Jelinkova, Helena; Dolezalova, Libuse; Kubelka, Jiri; Prochazka, Stanislav; Hamal, Karel; Krejsa, Otakar

    1997-12-01

    This study compares bond shear strength between hard dental tissues and composite resin filling material after a classical acid etching treatment procedure and Er:YAG laser surface conditioning. The retention of composite resin was evaluated for three cases: (1) the flat dental substrate without any conditioning, (2) the classical drilling machine prepared surface with acid etching and (3) the Er:YAG laser conditioning of enamel and dentin. None significant differences between bond shear strength of the classical drilling machine prepared surface with acid etching in comparison with the laser radiation conditioning were found.

  7. Influence of laser radiation on the growth and development of seeds of agricultural plants

    Science.gov (United States)

    Grishkanich, Alexander; Zhevlakov, Alexander; Polyakov, Vadim; Kascheev, Sergey; Sidorov, Igor; Ruzankina, Julia; Yakovlev, Alexey; Mak, Andrey

    2016-04-01

    The experimental results presented in this study focused on the study of biological processes caused by exposure to the coating layers of the laser green light seed (λ = 532 nm) range for the larch, violet (λ = 405 nm) and red (λ = 640 nm) for spruce. Spend a series of experiments to study the dependence of crop seed quality (spruce and larch from the pine family) from exposure to laser radiation under different conditions. In all the analyzed groups studied seed germination and growth of seedlings exposed to laser exposure, compared with the control group. The results showed that the higher percentage of germination than seeds of the control group.

  8. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

    Science.gov (United States)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

    2015-03-01

    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  9. [Photomodification of blood by laser and ultraviolet radiation: a comparative study].

    Science.gov (United States)

    Zalesskaia, G A; Kalosha, I I

    2014-01-01

    The efficiency of in vivo blood irradiation by a laser light source (λ = 632.8 and 670 nm) and a mercury lamp (UV light, λ = 254 nm) was compared. Absorption spectra, gas content, oxyhemoglobin content, hemoglobin oxygen saturation, concentrations of lactate and glucose were studied for both irradiated and control samples. Hemoglobin was assumed to be the primary photoacceptor of light radiation for the indicated wavelengths. No substantial differences have been found between the effects of laser and non-laser irradiation. We conclude that the biological impact of the procedure is related to photoinduced changes in hemoglobin oxygen saturation.

  10. Acoustic-wave generation in the process of CO2-TEA-laser-radiation interaction with metal targets in air

    Science.gov (United States)

    Apostol, Ileana; Teodorescu, G.; Serbanescu-Oasa, Anca; Dragulinescu, Dumitru; Chis, Ioan; Stoian, Razvan

    1995-03-01

    Laser radiation interaction with materials is a complex process in which creation of acoustic waves or stress waves is a part of it. As a function of the laser radiation energy and intensity incident on steel target surface ultrasound signals were registered and studied. Thermoelastic, ablation and breakdown mechanisms of generation of acoustic waves were analyzed.

  11. Experimental observation of strong radiation reaction in the field of an ultra-intense laser

    Science.gov (United States)

    Sarri, G.; Poder, K.; Tamburini, M.; di Piazza, A.; Keitel, C. H.; Zepf, M.

    2017-10-01

    Describing radiation reaction in an electromagnetic field is one of the most fundamental outstanding problems in electrodynamics. It consists of determining the dynamics of a charged particle fully taking into account self-forces (loosely referred to as radiation reaction) resulting from the radiation fields generated by the particle whilst it is accelerated. Radiation reaction has only been invoked to explain the radiative properties of powerful astrophysical objects, such as pulsars and quasars. From a theoretical standpoint, this phenomenon is subject of fervent debate and this impasse is worsened by the lack of experimental data, due to extremely high fields required to trigger these effects. Here, we report on the first experimental evidence of strong radiation reaction during the interaction of an ultra-relativistic electron beam with an intense laser field, beyond a purely classical description.

  12. Influence of the dentin surface properties on the laser radiation absorption

    Science.gov (United States)

    Chmelickova, Hana; Sebestova, Hana; Hiklova, Helena; Rihakova, Lenka

    2012-01-01

    Research of the optical radiation interaction with human tooth tissues has started early after the first laser construction. Absorptivity of the particular tissue is dependent on the wavelength, thus CO2, Er:YAG and Nd:YAG lasers were used in many experimental works all over the world. Near infrared radiation of the pulsed Nd:YAG laser was found to be suitable for dentine hypersensitivity treatment by sealing of the open tubules with melted and re-solidified dentin. Series of experiments were performed to find suitable process parameters in the laser laboratory equipped with the industrial pulsed Nd:YAG laser system. Tooth samples were prepared and classified into five groups according to their different degree of the surface grinding and polishing. Two types of antireflective agents, erythrosine and black ink, were applied on the samples surfaces. Coated samples and reference ones without any agents were treated with a set of increasing pulse energy values. Pulse frequency, pulse length, laser beam diameter on the sample surface and relative speed remained constant. Lines of the melted spots were displayed by confocal microscope; surface profiles were scanned by contact profilometer. Dimensions of the dentine melted spots were extracted from the measured data and their dependence on the laser pulse energy, degree of the surface grinding and type of antireflective agent were evaluated.

  13. APPLICATIONS OF LASERS AND OTHER TOPICS IN LASER PHYSICS AND TECHNOLOGY: Influence of atmospheric fluctuations of the induced temperature on the characteristics of laser radiation

    Science.gov (United States)

    Banakh, Viktor A.; Smalikho, I. N.

    1987-10-01

    The expression for the function representing the second-order mutual coherence of a laser beam propagating in a turbulent atmosphere under thermal self-interaction conditions is derived in the aberration-free approximation. An analysis is made of the width of a beam, its wind refraction, and the radius of coherence as a function of the initial coherence of the radiation, of conditions of diffraction on the transmitting aperture, and of fluctuations of the wind velocity. It is shown that on increase in the power the coherence radius of cw laser radiation first increases because of thermal defocusing and then decreases due to the appearance (because of fluctuations of the wind velocity) of induced temperature inhomogeneities in air in the beam localization region. The conditions under which fluctuations of the induced temperature have a significant influence on the coherence of the radiation are determined.

  14. Plastic hollow waveguides: properties and possibilities as a flexible radiation delivery system for CO2-laser radiation.

    Science.gov (United States)

    Cossmann, P H; Romano, V; Spörri, S; Altermatt, H J; Croitoru, N; Frenz, M; Weber, H P

    1995-01-01

    One significant inconvenience of the CO2 laser is the lack of flexible fibers essential for endoscopic applications. The goal of this study is to test the feasibility of hollow waveguides in view of a practical use in medicine. Various types of plastic hollow waveguides for flexible delivery of CO2 laser radiation were examined. The transmission losses, divergence angle, damage threshold, and input and output beam profiles were determined. The interaction process between radiation transmitted through these guides with soft as well as hard tissues was studied. Plastic hollow waveguides can transmit high power (up to 50 W) with low losses (straight guide 1 dB/m) even through bendings. The divergence angle is laser beam. The results of this study show good cutting quality and durability of these flexible plastic hollow waveguides, which render possible to deliver CO2 radiation in the power range needed for most surgical applications with affordable transmission losses. Plastic hollow waveguides are, therefore, a real alternative to replace the mirror arms.

  15. Effects of femtosecond laser radiation on blood cell suspensions

    Science.gov (United States)

    Gening, Tatyana; Sysolyatin, Aleksey; Abakumova, Tatyana; Arslanova, Dinara; Voronova, Olga; Zolotovsky, Igor; Ostatochnikov, Vladimir; Yavtushenko, Marina

    2011-03-01

    In the present work the effects of high-power femtosecond laser irradiation on a functional condition of red blood cells and neutrophils in vitro have been investigated. The data on parameters of the lipid peroxidation - antioxidants system, hemoglobin level and rigidity of red blood cell membranes testify destabilization of the membranes under the influence of the given laser. The study of phagocytic activity, anaerobic and aerobic metabolism of neutrophils, and rigidity of their membranes allows to suppose the dose-dependent effect to be stimulating.

  16. Formation of pores in Ge single crystal by laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Medvid' , A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia)]. E-mail: medvids@latnet.lv; Mychko, A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia); Krivich, A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia); Onufrijevs, P. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia)

    2005-05-15

    Formation of a porous structure on the surface of Ge single crystals by pulsed YAG:Nd laser irradiation at the intensity of {approx}25 MW/cm{sup 2} is reported. An increase of surface recombination velocity on the irradiated surface by a factor of 100 is observed and explained by increase of the geometric area of the surface due to formation of pores. The latter is attributed to inhomogeneous pressure of a pulsed laser beam on the melting irradiated surface of the crystal.

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases

    Science.gov (United States)

    Kanevskiĭ, M. F.; Stepanova, M. A.

    1990-06-01

    An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

  18. Risks induced by laser radiation; Risques induits par le rayonnement laser

    Energy Technology Data Exchange (ETDEWEB)

    Courant, D. [CEA Fontenay-aux-Roses, 92 (France). Dept. de Radiobiologie et de Radiopathologie

    2001-07-01

    The use of lasers is often dangerous because of the emitted power, the wave length, the conduction system(optical fiber, wave guide, mirrors) and the use conditions. The safety notion involves the precise knowledge of materials, the biological effects in function of laser emission parameters, the knowledge of protection standards, the observance of use rules and the personnel training. This chapter treats the risks induced by the beam. It gives the different biological effects induced by the laser beam, at the eye and skin levels that are at the origin of exposure limits and the lasers classification recommended by the protection standards. (N.C.)

  19. Testing relativity again, laser, laser, laser, laser

    NARCIS (Netherlands)

    Einstein, A.

    2015-01-01

    laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser,

  20. Refraction Measurements Of Excimer Area Ablated Animal Corneas Using A Modified Autorefractor

    Science.gov (United States)

    Clapham, Terrance N.; Herekar, Satish; Koons, Stephen

    1988-06-01

    Developing refractive surgery techniques usually requires pre-clinical trials with animals before human clinicals are performed. In order to assess the results of the surgery, an accurate and repeatable measurement of the resultant refraction must be made. Normal techniques such as retinoscopy, subjective examinations, and conventional autorefractions all run into problems when animals are involved. The authors have modified a conventional autorefractor and have made measurements on rabbits and monkeys both before and after refractive surgery treatments with an excimer laser. The results showed refractive changes with degrees of myopic correction.

  1. The role of radiation transport in the thermal response of semitransparent materials to localized laser heating

    Energy Technology Data Exchange (ETDEWEB)

    Colvin, Jeffrey [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shestakov, Aleksei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stolken, James [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vignes, Ryan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2011-03-09

    Lasers are widely used to modify the internal structure of semitransparent materials for a wide variety of applications, including waveguide fabrication and laser glass damage healing. The gray diffusion approximation used in past models to describe radiation cooling is not adequate for these materials, particularly near the heated surface layer. In this paper we describe a computational model based upon solving the radiation transport equation in 1D by the Pn method with ~500 photon energy bands, and by multi-group radiationdiffusion in 2D with fourteen photon energy bands. The model accounts for the temperature-dependent absorption of infrared laser light and subsequent redistribution of the deposited heat by both radiation and conductive transport. We present representative results for fused silica irradiated with 2–12 W of 4.6 or 10.6 µm laser light for 5–10 s pulse durations in a 1 mm spot, which is small compared to the diameter and thickness of the silica slab. Furthermore, we show that, unlike the case for bulk heating, in localized infrared laser heatingradiation transport plays only a very small role in the thermal response of silica.

  2. Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation

    CERN Document Server

    Fourmaux, S; Phuoc, K Ta; Leguay, P M; Payeur, S; Lassonde, P; Gnedyuk, S; Lebrun, G; Fourment, C; Malka, V; Sebban, S; Rousse, A; Kieffer, J C

    2011-01-01

    Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated and wiggled in the laser-wakefield cavity. This femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt range has been observed at different interaction regime using high power laser from 10 to 100 TW. However, none of the spectral measurement performed were at sufficient resolution, bandwidth and signal to noise ratio to precisely determine the shape of spectra with a single laser shot in order to avoid shot to shot fluctuations. In this letter, the Betatron radiation produced using a 80 TW laser is characterized by using a single photon counting method. We measure in single shot spectra from 8 to 21 keV with a resolution better than 350 eV. The results obtained are in excellent agreement with theoretical predictions and demonstrate the synchrotron type nature of this radiation mechanism. The critical energy is found to be Ec = 5.6 \\pm 1 keV for our experimental conditions. In addition, th...

  3. NONLINEAR OPTICAL FREQUENCY CONVERTER OF LASER RADIATION ON THE LBO TYPE I CRYSTALS

    Directory of Open Access Journals (Sweden)

    N. V. Kondratyuk

    2014-01-01

    Full Text Available Describes nonlinear optical frequency converter of laser radiation based on the two LBO type I crystals allowing to receive pulses of radiation at three wavelengths of 1064 nm, 532 nm and 355 nm with an adjustable pulse energy. For fine adjustment of the output pulse energy used two dual phase plates that change the orientation of the plane of polarization of the two waves in cascade third harmonic generation. Measured the efficiency of the generation of harmonics of the intensity of radiation at 1064 nm.

  4. Second harmonic generation of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary

    Energy Technology Data Exchange (ETDEWEB)

    Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu

    2011-09-30

    A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by generating the second harmonic in a KDP crystal. The energy efficiency of the conversion was 30 %.

  5. Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field

    NARCIS (Netherlands)

    Astapenko, VA

    A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1 : 2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection

  6. Caries inhibition potential of Er:YAG and Er:YSGG laser radiation

    Science.gov (United States)

    Fried, Daniel; Featherstone, John D. B.; Visuri, Steven R.; Seka, Wolf D.; Walsh, Joseph T., Jr.

    1996-04-01

    Dental hard tissues can be ablated efficiency by (lambda) equals 3 micrometers laser irradiation with minimal subsurface thermal damage. However, the potential of lasers operating in the region of the infrared for caries preventive treatments has not been investigated. In this study, the caries inhibition potential of Er:YAG ((lambda) equals 2.94 micrometers ) and Er:YSGG ((lambda) equals 2.79 micrometers ) laser radiation on dental enamel was evaluated at various irradiation intensities. Pulsed IR radiometry and scanning electron microscopy (SEM) were used to measure the time-resolved surface temperatures during laser irradiation and to detect changes in the surface morphology. The magnitude and temporal evolution of the surface temperature during multiple pulse irradiation of the tissue was dependent on the wavelength, irradiation intensity, and the number of laser pulses. Radiometry and SEM micrographs indicated that ablation was initiated at temperatures of approximately 300 degree(s)C for Er:YAG and 800 degree(s)C for Er:YSGG laser irradiation, well below the melting and vaporization temperatures of the carbonated hydroxyapatite mineral component (m.p. equals 1200 degree(s)C). Nevertheless, there was marked caries inhibition for irradiation intensities below those temperature thresholds, notably 60% and 40% inhibition was achieved after Er:YSGG and Er:YAG laser irradiation, respectively. These results indicate that the Er:YSGG laser can be used effectively for both preventive dental treatments and for hard tissue removal.

  7. Characterization of Tin/Ethylene Glycol Solar Nanofluids Synthesized by Femtosecond Laser Radiation.

    Science.gov (United States)

    Torres-Mendieta, Rafael; Mondragón, Rosa; Puerto-Belda, Verónica; Mendoza-Yero, Omel; Lancis, Jesús; Juliá, J Enrique; Mínguez-Vega, Gladys

    2017-05-05

    Solar energy is available over wide geographical areas and its harnessing is becoming an essential tool to satisfy the ever-increasing demand for energy with minimal environmental impact. Solar nanofluids are a novel solar receiver concept for efficient harvesting of solar radiation based on volumetric absorption of directly irradiated nanoparticles in a heat transfer fluid. Herein, the fabrication of a solar nanofluid by pulsed laser ablation in liquids was explored. This study was conducted with the ablation of bulk tin immersed in ethylene glycol with a femtosecond laser. Laser irradiation promotes the formation of tin nanoparticles that are collected in the ethylene glycol as colloids, creating the solar nanofluid. The ability to trap incoming electromagnetic radiation, thermal conductivity, and the stability of the solar nanofluid in comparison with conventional synthesis methods is enhanced. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Propagation of intense laser radiation through a diffusion flame of burning oil

    Energy Technology Data Exchange (ETDEWEB)

    Gvozdev, S V; Glova, A F; Dubrovskii, V Yu; Durmanov, S T; Krasyukov, A G; Lysikov, A Yu; Smirnov, G V; Pleshkov, V M [State Research Center of Russian Federation ' Troitsk Institute for Innovation and Fusion Research' , Troitsk, Moscow Region (Russian Federation)

    2015-06-30

    We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 10{sup 3} to 1.2 × 10{sup 6} W cm{sup -2}) entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented. (laser applications and other topics in quantum electronics)

  9. Effective extreme ultraviolet radiation source based on laser-produced plasma in supersonic xenon jet

    Science.gov (United States)

    Bobashev, S. V.; Domracheva, I. V.; Petrenko, M. V.; Tumakaev, G. K.; Stepanova, Z. A.

    2007-04-01

    Development of highly effective debris free EUV (extreme ultraviolet) radiation source is an actual problem today. Experimental results on EUV output from the source based on laser-produced plasma in supersonic Xe jet have been obtained. The conversion efficiency is 0.08% at a wavelength of 13.5 nm (Δλ = 0.35 nm, 2π sterrad). The methods of optimization of gas-jet converter have been determined. Measurements of EUV radiation energy dependence on the laser energy and the target material (solid-state Cu, Mo, W, Ta and supersonic Xe jet) have been made. The conversion efficiency of laser-produced plasma (CELPP) has been determined and the experimental values have been obtained for different materials of the target.

  10. Maculopathy following exposure to visible and infrared radiation from a laser pointer: a clinical case study.

    Science.gov (United States)

    Hanson, James V M; Sromicki, Julian; Mangold, Mario; Golling, Matthias; Gerth-Kahlert, Christina

    2016-04-01

    Laser pointer devices have become increasingly available in recent years, and their misuse has caused a number of ocular injuries. Online distribution channels permit trade in devices which may not conform to international standards in terms of their output power and spectral content. We present a case study of ocular injury caused by one such device. The patient was examined approximately 9 months following laser exposure using full-field and multifocal electroretinography (ERG and MF-ERG), electrooculography (EOG), and optical coherence tomography (OCT), in addition to a full ophthalmological examination. MF-ERG, OCT, and the ophthalmological examination were repeated 7 months after the first examination. The output of the laser pointer was measured. Despite severe focal damage to the central retina visible fundoscopically and with OCT, all electrophysiological examinations were quantitatively normal; however, qualitatively the central responses of the MF-ERG appeared slightly reduced. When the MF-ERG was repeated 7 months later, all findings were normal. The laser pointer was found to emit both visible and infrared radiation in dangerous amounts. Loss of retinal function following laser pointer injury may not always be detectable using standard electrophysiological tests. Exposure to non-visible radiation should be considered as a possible aggravating factor when assessing cases of alleged laser pointer injury.

  11. In vitro effects of Nd:YAG laser radiation on blood: a quantitative and morphologic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Borrero, E.; Rosenthal, D.; Otis, J.B.

    1988-01-01

    Use of the Neodymium: yttrium -aluminum -garnet (Nd:YAG) laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 54 samples of citrated whole blood were exposed to Nd:YAG laser radiation of varying powers (10, 20 and 30 watts) and duration (1, 2.5 and 5 seconds). Compared to control samples which were not subjected to laser light, there was no significant decrease in hematocrit (41 to 40.5 +/- 5%), hemoglobin concentration (13.8 to 13.8 +/- .06 g/1OO ml), or increase in free hemoglobin concentration. Debris weight (from .45 +/- .002 to .45 +/- .002 mg), as well as the white blood cell count, was also not significantly changed (from 5,400 to 5,200 +/- 240 WBC/cm). Light microscopy examination of debris from samples of whole blood, washed erythrocytes, and platelet-rich plasma subjected to the laser at 30 watts for five seconds failed to demonstrate the presence of membrane denaturation of blood elements, as compared with the morphologic changes observed in whole blood samples exposed to a hot tip rather than Nd:YAG laser radiation. Nd:YAG laser can be used intravascularly without fear of hemolysis or debris micro-embolization up to a power of 30 watts for five seconds.

  12. Application of laser radiation and magnetostimulation in therapy of patients with multiple sclerosis.

    Science.gov (United States)

    Kubsik, Anna; Klimkiewicz, Robert; Janczewska, Katarzyna; Klimkiewicz, Paulina; Jankowska, Agnieszka; Woldańska-Okońska, Marta

    2016-01-01

    Multiple sclerosis is one of the most common neurological disorders. It is a chronic inflammatory demyelinating disease of the CNS, whose etiology is not fully understood. Application of new rehabilitation methods are essential to improve functional status. The material studied consisted of 120 patients of both sexes (82 women and 38 men) aged 21-81 years. The study involved patients with a diagnosis of multiple sclerosis. The aim of the study was to evaluate the effect of laser radiation and other therapies on the functional status of patients with multiple sclerosis. Patients were randomly divided into four treatment groups. The evaluation was performed three times - before the start of rehabilitation, immediately after rehabilitation (21 days of treatment) and subsequent control - 30 days after the patients leave the clinic. The following tests were performed for all patients to assess functional status: Expanded Disability Status Scale (EDSS) of Kurtzke and Barthel Index. Results of all testing procedures show that the treatment methods are improving the functional status of patients with multiple sclerosis, with the significant advantage of the synergistic action of laser and magneto stimulation. The combination of laser and magneto stimulation significantly confirmed beneficial effect on quality of life. The results of these studies present new scientific value and are improved compared to program of rehabilitation of patients with multiple sclerosis by laser radiation which was previously used. This study showed that synergic action of laser radiation and magneto stimulation has a beneficial effect on improving functional status, and thus improves the quality of life of patients with multiple sclerosis. The effects of all methods of rehabilitation are persisted after cessation of treatment applications, with a particular advantage of the synergistic action of laser radiation and magneto stimulation, which indicates the possibility to elicitation in these

  13. Rotatory power of sodium vapour oriented by laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Bicchi, P. (Siena Univ. (Italy). Ist. di Fisica); Moi, L.; Zambon, B. (Consiglio Nazionale delle Ricerche, Pisa (Italy). Lab. di Fisica Atomica e Moleculare)

    1979-01-11

    In this paper the rotatory power of sodium vapour is studied when laser light is used as pumping as well as analysis light. The possibility of having an analysis light whose frequency may be varied in a range larger than the interval between the D/sub 1/ and D/sub 2/ atomic lines allows us to get for the first time the complete shape of the rotation curve and to measure a rotation different from zero even for frequencies very far from the resonance ones. The complete orientation in the vapour caused by the laser pumping-light power permits to obtain very high rotation values. In a cell containing Na and 200 Torr of Ne, we measured, at 185/sup 0/C, 10/sup 0//cm of specific rotation. The dependence of the optical activity on the buffer gas pressure and on the frequency of the pumping light is also studied.

  14. Dynamics of Radiation and Atoms in Ultrahigh Intensity Laser Fields

    Science.gov (United States)

    2013-12-31

    excitation in strong and ultrastrong optical frequency fields. Advances in laser technology continue to push the boundaries of this interaction in...possible ultrastrong magnetic fields and the electron cyclotron frequency in the bound state can create dynamics, such as is the case for `cycloatoms...promise of increasing the returning rescattering electron energy led to advances in the production of HHG. In addition to (e,2e) and HHG rescattering

  15. Two-dimensional modeling of multiply scattered laser radiation in optically dense aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Zardecki, A.; Gerstl, S.A.W.; Embury, J.F.

    1982-01-01

    The discrete ordinates finite element radiation transport code TWOTRAN is applied to describe the multiple scattering of a laser beam from a reflecting target. For a model scenario involving a 99% relative humidity rural aerosol, we compute the average intensity of the scattered radiation and correction factors to the Lambert-Beer law arising from multiple scattering. As our results indicate, two-dimensional x-y and r-z geometry modeling can reliably describe a realistic three-dimensional scenario. Specific results are presented for the two visual ranges of 1.52 and 0.76 km which show that for sufficiently high aerosol concentrations (e.g., equivalent to V = 0.76 km) the target signature in a distant detector becomes dominated by multiply scattered radiation from interactions of the laser light with the aerosol environment.

  16. Biophotonics of the interaction of low-intensity laser radiation with blood erythrocytes

    Science.gov (United States)

    Asimov, M. M.; Asimov, R. M.; Batyan, A. N.; Trusevich, M. O.; Rubinov, A. N.

    2013-06-01

    We have studied experimentally how optical radiation affects the neutralization of the toxic action of heavy metals and harmful chemical compounds (ecotoxicants) on the oxygen-transport function of blood erythrocytes. It has been found that the optical radiation has a stabilizing effect and prevents lowering the erythrocyte concentration in the presence of phenol and heavy metals in blood. We have studied the neutralization efficiency of the toxic action of ecotoxicants in relation to the laser irradiation time. The obtained data on the effect of the laser radiation on the thermal denaturation of hemoglobin and erythrocytes yield the scientific substantiation to the development of the optical method for the use in medicine upon drawing and conserving donor blood. We have shown that the obtained data can be used in medicine for improving the reliability of conditions of conservation and storage of donor blood, as well as for preventing the toxic action of harmful chemical compounds in the environment.

  17. Systems and methods for imaging using radiation from laser produced plasmas

    Science.gov (United States)

    Renard-Le Galloudec, Nathalie; Cowan, Thomas E.; Sentoku, Yasuhiko; Rassuchine, Jennifer

    2009-06-30

    In particular embodiments, the present disclosure provides systems and methods for imaging a subject using radiation emitted from a laser produced plasma generating by irradiating a target with a laser. In particular examples, the target includes at least one radiation enhancing component, such as a fluor, cap, or wire. In further examples, the target has a metal layer and an internal surface defining an internal apex, the internal apex of less than about 15 .mu.m, such as less than about 1 .mu.m. The targets may take a variety of shapes, including cones, pyramids, and hemispheres. Certain aspects of the present disclosure provide improved imaging of a subject, such as improved medical images of a radiation dose than typical conventional methods and systems.

  18. Radiation reaction induced spiral attractors in ultra-intense colliding laser beams

    Directory of Open Access Journals (Sweden)

    Zheng Gong

    2016-11-01

    Full Text Available The radiation reaction effects on electron dynamics in counter-propagating circularly polarized laser beams are investigated through the linearization theorem and the results are in great agreement with numeric solutions. For the first time, the properties of fixed points in electron phase-space were analyzed with linear stability theory, showing that center nodes will become attractors if the classical radiation reaction is considered. Electron dynamics are significantly affected by the properties of the fixed points and the electron phase-space densities are found to be increasing exponentially near the attractors. The density growth rates are derived theoretically and further verified by particle-in-cell simulations, which can be detected in experiments to explore the effects of radiation reaction qualitatively. The attractor can also facilitate realizing a series of nanometer-scaled flying electron slices via adjusting the colliding laser frequencies.

  19. Controlled joining of Ag nanoparticles with femtosecond laser radiation

    Science.gov (United States)

    Huang, H.; Liu, L.; Peng, P.; Hu, A.; Duley, W. W.; Zhou, Y.

    2012-12-01

    We show that it is possible to tailor the gap separation and interface geometry between adjacent Ag nanoparticles (NPs) by controlling fluence when irradiating with pulses from a fs laser. Unirradiated samples extracted from aqueous solution consist of networks of Ag NPs coated with polyvinylpyrrolidone (PVP). At low laser fluence, bonding between NPs occurs via the formation of an intervening hydrogenated amorphous carbon (α-C:H) layer resulting from the laser-induced decomposition of PVP. This occurs when electrons are emitted at hot-spots created by the trapping of plasmons. The thickness of the α-C:H layer determines the minimum separation between NPs. Ag NPs with different contact geometries can be produced by irradiation of the networks in solution at fluences exceeding the threshold for the formation of α-C:H. At fluences between 200 and 380 μJ/cm2, the α-C:H interface layer is replaced with a metallic neck. Surface enhanced Raman scattering (SERS) has been used to quantify the electromagnetic field enhancement in joined NP samples. We find that Ag NPs bonded by α-C:H and exhibiting a narrow gap possess the highest SERS enhancement.

  20. Recommendations concerning the prevention of radiation-induced health hazards through the application of soft and MID lasers

    Energy Technology Data Exchange (ETDEWEB)

    1987-01-01

    The Federal Health Office (BGA) recommends observation of the following practical hints: The application of soft lasers or MID lasers for cosmetic treatment or acupuncture represents a danger to the eye. Instructions for use of laser equipment have to indicate this danger. Appropriate use of the equipment will prevent damage. Any person applying soft lasers or MID lasers for treatment of customers or patients near the eye are required to give proof of a special training assuring appropriate handling, and of instructions in laser radiation protection.

  1. Beam characteristics of a large-bore copper laser with a radiatively cooled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chang, J.J.; Boley, C.D.; Molander, W.A.; Warner, B.E. [Lawrence Livermore National Lab., CA (United States); Martinez, M.W. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)

    1994-01-18

    In a large-bore copper vapor laser (CVL), excessive gas heating at the axial region of the discharge lowers its efficiency by thermally populating the metastable lower laser levels. The associated lower gas density also lengthens the discharge field-diffusion time, leading to weaker axial pumping and undesired beam characteristics. The authors` laboratory has developed a novel approach to circumvent this obstacle by cooling the plasma radiatively via a series of segmented metal plates (septa) placed vertically along the length of the tube. This improved tube design significantly lowers the average gas temperature and shortens the radial delay. A 27% increase in laser power was observed with the addition of septa. The authors have characterized the beam intensity profile, spatial and temporal pulse variation, and beam polarization through extensive laboratory measurements. A detailed computational model of the laser has been used to characterize and interpret the laboratory results.

  2. Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios

    Science.gov (United States)

    Zhang, Liang-Liang; Wang, Wei-Min; Wu, Tong; Zhang, Rui; Zhang, Shi-Jing; Zhang, Cun-Lin; Zhang, Yan; Sheng, Zheng-Ming; Zhang, Xi-Cheng

    2017-12-01

    In the widely studied two-color laser scheme for terahertz (THz) radiation from a gas, the frequency ratio of the two lasers is usually fixed at ω2/ω1=1 :2 . We investigate THz generation with uncommon frequency ratios. Our experiments show, for the first time, efficient THz generation with new ratios of ω2/ω1=1 :4 and 2 ∶3 . We observe that the THz polarization can be adjusted by rotating the longer-wavelength laser polarization and the polarization adjustment becomes inefficient by rotating the other laser polarization; the THz energy shows similar scaling laws with different frequency ratios. These observations are inconsistent with multiwave mixing theory, but support the gas-ionization or plasma-current model. This study pushes the development of the two-color scheme and provides a new dimension to explore the long-standing problem of the THz generation mechanism.

  3. Laser-induced narrowband coherent synchrotron radiation: Efficiency versus frequency and laser power

    Directory of Open Access Journals (Sweden)

    C. Evain

    2010-09-01

    Full Text Available We analyze the narrowband terahertz emission process occurring from electron bunches passing in a bending magnet, after a laser-induced sinusoidal modulation has been performed. In particular, we focus on experimental tunability curves, and power scalings with current and laser power. Theoretically, we simplify the problem formulation using the slowly varying envelope approximation. At low powers, the scaling with laser power appears to be quadratic, and analytical expressions for the tuning curves are obtained. Emission at first passage in the bending magnet, and after one full turn in the storage ring, are considered both experimentally and theoretically. The experiments are performed on the UVSOR-II storage ring.

  4. Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4

    Science.gov (United States)

    Telle, John M.

    1986-01-01

    Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4. Laser radiation at 16 .mu.m has been observed in a cooled static cell containing low pressure CF.sub.4 optically pumped by an approximately 3 W output power cw CO.sub.2 laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF.sub.4 laser output power at 615 cm.sup.-1 exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 .mu.m might be obtained.

  5. Apparatus and method for generating continuous wave 16. mu. m laser radiation using gaseous CF/sub 4/

    Science.gov (United States)

    Telle, J.M.

    1984-05-01

    Apparatus and method for generating continuous wave 16 ..mu..m laser radiation using gaseous CF/sub 4/. Laser radiation at 16 ..mu..m has been observed in a cooled static cell containing low pressure CF/sub 4/ optically pumped by an approximately 3 W output power c-w CO/sub 2/ laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF/sub 4/ laser output power at 615 cm/sup -1/ exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 ..mu..m might be obtained.

  6. 3D Finite Element Model for Writing Long-Period Fiber Gratings by CO2 Laser Radiation

    Directory of Open Access Journals (Sweden)

    José Rebordão

    2013-08-01

    Full Text Available In the last years, mid-infrared radiation emitted by CO2 lasers has become increasing popular as a tool in the development of long-period fiber gratings. However, although the development and characterization of the resulting sensing devices have progressed quickly, further research is still necessary to consolidate functional models, especially regarding the interaction between laser radiation and the fiber’s material. In this paper, a 3D finite element model is presented to simulate the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Dependence with temperature of the main parameters of the optical fiber materials (with special focus on the absorption of incident laser radiation is considered, as well as convection and radiation losses. Thermal and residual stress analyses are made for a standard single mode fiber, and experimental results are presented.

  7. 3D finite element model for writing long-period fiber gratings by CO2 laser radiation.

    Science.gov (United States)

    Coelho, João M P; Nespereira, Marta; Abreu, Manuel; Rebordão, José

    2013-08-12

    In the last years, mid-infrared radiation emitted by CO2 lasers has become increasing popular as a tool in the development of long-period fiber gratings. However, although the development and characterization of the resulting sensing devices have progressed quickly, further research is still necessary to consolidate functional models, especially regarding the interaction between laser radiation and the fiber's material. In this paper, a 3D finite element model is presented to simulate the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Dependence with temperature of the main parameters of the optical fiber materials (with special focus on the absorption of incident laser radiation) is considered, as well as convection and radiation losses. Thermal and residual stress analyses are made for a standard single mode fiber, and experimental results are presented.

  8. An assessment of techniques for dehydrating root canals using infrared laser radiation.

    Science.gov (United States)

    Amyra, T; Walsh, L T; Walsh, L J

    2000-08-01

    Infrared lasers have been used for debridement and sterilisation of both soft and hard tissues, but there have been few studies of such laser applications in endodontics. The present laboratory study was undertaken to examine the feasibility of using pulsed infrared laser radiation to remove moisture from root canals (with an adjunctive sterilising effect). Canals were prepared in extracted teeth and a standardised technique used to fill the apical half of the root canal with saline. Pulses of CO2 or Nd:YAG laser energy were delivered into the root canal system via miniature applicators and residual fluid determined, as well as temperature changes on the root surface. With the CO2 laser, long pulse durations were effective at dehydrating the canals, but elicited deleterious thermal changes both locally within the canal as well as on the root surface. With Nd:YAG laser treatment, large temperature increases on the root surface occurred even with low powers and low pulse frequencies, and extended times were necessary for dehydration. With higher powers and pulse frequencies, complete dehydration could be achieved in less than 60 seconds, however root surface temperatures increased approximately 25 degrees, and the radicular dentine was damaged by the production of plasma. Dehydration of root canals could not be achieved safely with these two infrared lasers, and damage to both radicular dentine and the periodontal ligament would occur if these techniques were to be applied clinically. Alternative methods which do not exert significant thermal effects should be investigated.

  9. [Research on radiation intensity of nanosecond pulse laser-induced soil plasma].

    Science.gov (United States)

    Chen, Jin-zhong; Song, Guang-ju; Sun, Jiang; Li, Xu; Wei, Yan-hong

    2012-01-01

    To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd : YAG laser was used to excite soil sample. The laser-induced plasma spectrum was observed using a grating spectrometer and a photoelectric detection system. The influence of laser output energy ranging from 100 to 500 mJ on the radiation intensity of plasma was studied. The results show that both the line intensity and signal-to-background ratio can be enhanced under the optimized condition that the laser energy is 200 mJ. The quality of spectrum was further improved after the laser beam used to excite the sample was defocused properly. When the defocusing position is + 6 mm, the spectral lines intensity of element Mg, Al, K and Fe increased about 46%, 63%, 59% and 45% compared to that without defocusing respectively. The spectral signal-to-background ratio increased about 11%, 31%, 35% and 38% respectively. This lays a foundation for detection of trace impurity element in soil.

  10. Evaluating the use of laser radiation in cleaning of copper embroidery threads on archaeological Egyptian textiles

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Kareem, Omar [Conservation Department, Faculty of Archaeology, Cairo University, El-Gamaa Street, El-Giza (Egypt)], E-mail: Omaa67@yahoo.com; Harith, M.A. [National Institute of Laser Enhanced Science, Cairo University (Egypt)], E-mail: mharithm@niles.edu.eg

    2008-07-15

    Cleaning of copper embroidery threads on archaeological textiles is still a complicated conservation process, as most textile conservators believe that the advantages of using traditional cleaning techniques are less than their disadvantages. In this study, the uses of laser cleaning method and two modified recipes of wet cleaning methods were evaluated for cleaning of the corroded archaeological Egyptian copper embroidery threads on an archaeological Egyptian textile fabric. Some corroded copper thread samples were cleaned using modified recipes of wet cleaning method; other corroded copper thread samples were cleaned with Q-switched Nd:YAG laser radiation of wavelength 532 nm. All tested metal thread samples before and after cleaning were investigated using a light microscope and a scanning electron microscope with an energy dispersive X-ray analysis unit. Also the laser-induced breakdown spectroscopy (LIBS) technique was used for the elemental analysis of laser-cleaned samples to follow up the laser cleaning procedure. The results show that laser cleaning is the most effective method among all tested methods in the cleaning of corroded copper threads. It can be used safely in removing the corrosion products without any damage to both metal strips and fibrous core. The tested laser cleaning technique has solved the problems caused by other traditional cleaning techniques that are commonly used in the cleaning of metal threads on museum textiles.

  11. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Generation of magnetic fields as a result of interaction of pairs of radiation pulses with solid barriers

    Science.gov (United States)

    Zakharov, N. S.; Shaĭnoga, I. S.; Shentsev, N. I.

    1989-02-01

    An analysis is made of the problem of generation of magnetic fields in a laser plasma jet formed as a result of the interaction of two consecutive radiation pulses of moderate intensity with a dielectric barrier. It is assumed that the source of an emf is the thermo-emf of the inhomogeneous plasma. The structure of gasdynamic streams and the parameters of magnetic fields in the plasma jet are found by numerical solution of a known system of equations considered in a two-dimensional cylindrical configuration. The profiles of the plasma parameters and the temporal and spatial distributions of the magnetic fields are presented. It is shown that the results of numerical calculations can be useful, for example, in the diagnostics of laser jets.

  12. Effect of uv laser radiation on copper-proteins

    Science.gov (United States)

    Bacci, M.; Fabeni, P.; Linari, R.; Pazzi, G. P.

    The results of irradiation studies of human ceruloplasmin, mushroom tyrosinase and Limuluspolyphemus hemocyanin with a nitrogen laser (Λ = 337.1 nm) are presented. In all the proteins we have considered the absorption band at 330 nm, characteristic of dimer Type 3 copper centres, decreases, while an increase of the absorbance at 280 nm is observed. Moreover a new band at about 400 nm appears in irradiated ceruloplasmin. Finally sharp oscillations of the absorbance at 610 and 794 nm are recorded in ceruloplasmin, when the irradiation is switched off.

  13. Microsecond enamel ablation with 10.6μm CO2 laser radiation

    Science.gov (United States)

    Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.

    2016-02-01

    Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold

  14. Biological Effects of Laser Radiation. Volume II. Review of Our Studies on Biological Effects of Laser Radiation-1965-1971.

    Science.gov (United States)

    1978-10-17

    produces dermal and nasal irritation.5 Boron systems. Bromine, chlorine and ucine are irntants to the trifluoride (TLV I ppm) in air, can cause pneumonitis...bromine, chlorine , iodine. General. Dept. of the Army. VASA Grant .VGR 011-07.I7 hydrolluoric acid. -141- from LASER OC~US/CC7t0SER !;68 The rare tarths...the system may crack and release the enclosed vapors. Examples of these gases are chlorine , bromine, lead, mercury, carbon monoxide, and hydro- gen

  15. Generation of nano-voids inside polylactide using femtosecond laser radiation

    Science.gov (United States)

    Viertel, Tina; Pabst, Linda; Olbrich, Markus; Ebert, Robby; Horn, Alexander; Exner, Horst

    2017-12-01

    The arrangement of nanometer-sized voids, induced by focusing intense laser radiation within transparent material can allow the generation of transparent components with dimensions in the micrometer to nanometre range due to internal contour cut and thus satisfy the progressive miniaturization of products in micro-optics and medical technologies. For further improvements in the precision of those components, a deep understanding of the involved processes during the interaction of laser radiation within the material is necessary. In this work, voids inside bulk polylactide (PLA), a bioabsorbable polymer, were generated using a femtosecond laser ( λ = 1030 nm, τH = 180 fs) with single and multiple pulse irradiation. The dependence of the spot size was examined by the use of four microscope objectives with focus radii of 4.9, 3.3, 2 and 1.2 µm. For the experiments, the pulse energy and focusing depth into the material were varied. The dimensions of the voids were experimentally determined as function of the intensity. Differences in the lateral and axial extents of the voids were obtained for different focus radii and focusing depths at same intensities. Furthermore, the intensity distribution of the laser radiation inside the material for the different focus radii and focusing depths, and their dependence on the lateral and axial sizes of the voids was simulated and compared with the experimental results.

  16. [Enhancing effect of sample additive on laser-induced plasma radiation].

    Science.gov (United States)

    Zhang, Lin-Jing; Chen, Jin-Zhong; Yang, Shao-Peng; Wei, Yan-Hong; Guo, Qing-Lin

    2010-05-01

    In order to improve the radiation characteristic of laser-induced plasma, with the national standard soil taken as the target sample, a laser spectrum analytical system which composed of a high-energy neodymium glass laser, a multifunctional and compact integrated spectrometer, and a CCD detector was used to detect the influence of the NaCl sample additive on the laser plasma radiation intensity. The electron temperature and the electron density of the plasmas were also calculated from the lines intensity and stark broadening of emission spectral line respectively. The experimental results indicated that with the increase in the NaCl additive, the spectral intensity, signal-to-background ratio, the electron temperature, and the electron density all went up firstly and then down. When 15% NaCl was added, the radiation intensity of the plasma reached the maximum value, the spectral lines intensity of element Mn, K, Fe, and Ti increased by 39.2%, 42.5%, 53.9% and 33.8% compared to that without additive respectively, the spectral signal-to-background ratio increased by 64.4%, 84.39, 44.55% and 58.2% respectively, while the electron temperature and the electron density of the plasmas were heightened by 0.17 times and 0.36 times respectively.

  17. Eczematous Dermatitis Occurring on a Café-au-Lait Spot Long after Laser Radiation.

    Science.gov (United States)

    Mihara, Motoyuki

    2013-05-01

    A 40-year-old woman presented with an itchy erythematosquamous change of a café-au-lait spot in her face. The onset of this change occurred just after her relocation. The café-au-lait spot had been irradiated by laser approximately 20 years ago. Clinically, there was a coin-sized erythema with a slight scale on the pigmented lesion in the left lateral orbital region. Histopathologically, the lesion demonstrated both spongiotic dermatitis and interface dermatitis together with lymphohistiocytic cell infiltration, in addition to moderate acanthosis and elongation of rete ridges with slight basal hyperpigmentation. From these clinical and histopathological findings, the lesion was diagnosed as eczematous dermatitis occurring on the café-au-lait spot after laser radiation. Another interesting histopathological finding was that some parts of a lobule of the sebaceous gland were occupied exclusively by degenerative atrophic sebocytes. From the viewpoint of pathogenesis, the eczematous dermatitis of this patient could have been an accompanying feature of a neurogenic inflammation occurring on the café-au-lait spot after laser radiation, and the atrophic change of a part of the sebaceous lobule might have been induced by a morphogenetic alteration of certain germinative cells of the sebaceous lobule due to laser radiation.

  18. Coatings of metal substrates assisted by laser radiation

    Directory of Open Access Journals (Sweden)

    Caudevilla, H.

    1998-04-01

    Full Text Available In this contribution, a new way of obtaining ceramic coatings is presented. This method uses precursor suspensions, settled on substrates and in-situ pyrolised with a laser. Different deposition techniques of the ceramic precursors have been tested in order to obtain a homogeneous distribution on the metal substrate before the laser treatment.

    La combinación de recubrimientos utilizando disoluciones de precursores metálicos con la pirólisis asistida por láser, permite obtener una gran diversidad de recubrimientos sobre sustratos de muy distinta naturaleza. Se han realizado estudios, tanto con disoluciones poliméricas, como con disoluciones de tipo sol-gel y pastas obtenidas con técnicas similares, depositadas utilizando métodos convencionales de inmersión y atomización previa a la pirólisis asistida por láser, así como simultánea. En este trabajo se presenta un resumen de los resultados más significativos obtenidos en la realización de recubrimientos sobre sustratos metálicos y cerámicos.

  19. Measurement of heat pump processes induced by laser radiation

    Science.gov (United States)

    Garbuny, M.; Henningsen, T.

    1983-01-01

    A series of experiments was performed in which a suitably tuned CO2 laser, frequency doubled by a Tl3AsSe37 crystal, was brought into resonance with a P-line or two R-lines in the fundamental vibration spectrum of CO. Cooling or heating produced by absorption in CO was measured in a gas-thermometer arrangement. P-line cooling and R-line heating could be demonstrated, measured, and compared. The experiments were continued with CO mixed with N2 added in partial pressures from 9 to 200 Torr. It was found that an efficient collisional resonance energy transfer from CO to N2 existed which increased the cooling effects by one to two orders of magnitude over those in pure CO. Temperature reductions in the order of tens of degrees Kelvin were obtained by a single pulse in the core of the irradiated volume. These measurements followed predicted values rather closely, and it is expected that increase of pulse energies and durations will enhance the heat pump effects. The experiments confirm the feasibility of quasi-isentropic engines which convert laser power into work without the need for heat rejection. Of more immediate potential interest is the possibility of remotely powered heat pumps for cryogenic use, such applications are discussed to the extent possible at the present stage.

  20. Antibacterial effects of pulsed Nd:YAG laser radiation at different energy settings in root canals.

    Science.gov (United States)

    Folwaczny, Matthias; Mehl, Albert; Jordan, Christian; Hickel, Reinhard

    2002-01-01

    The in vitro study aimed at the determination of the bacterial reduction in root canals used pulsed Nd:YAG laser radiation without a photosensitizing dye. In addition the temperature change in the root canals was determined during laser irradiation. The study sample was 114 root canals of extracted single-rooted human teeth that have been enlarged mechanically, sterilized, and randomly assigned to two experimental units. The source of radiation was a Nd:YAG laser device emitting pulsed infrared radiation at a wavelength of 1.064 microm, a pulse duration of 100 micros, and a pulse repetition rate of 20 pps. Samples of each experimental unit were inoculated with Escherichia coli (ATCC 25922) or Staphylococcus aureus (ATCC 25923), respectively, and divided into subgroups of 13 teeth each for irradiation for 20 s at 100 mJ or 200 mJ. One subgroup was left untreated as positive control and one subgroup was rinsed with 0.5 ml of sodium hypochloride. After laser treatment or rinsing with sodium hypochloride the number of bacteria in each root canal was determined using the surface spread plate technique. Statistical analysis of the results was performed with ANOVA and Scheffé test at a level of significance of 5% (p temperature increase at 100 mJ was 24.3 degrees C (+/-3.9) and that at 200 mJ was 61.8 degrees C (+/-4.2). The Nd:YAG laser radiation has antimicrobial effects in root canals even in the absence of photosensitizing dyes but also causes considerable temperature increase.

  1. Two-stage model of nanocone formation on a surface of elementary semiconductors by laser radiation

    Science.gov (United States)

    2012-01-01

    In this work, we study the mechanism of nanocone formation on a surface of elementary semiconductors by Nd:YAG laser radiation. Our previous investigations of SiGe and CdZnTe solid solutions have shown that nanocone formation mechanism is characterized by two stages. The first stage is characterized by formation of heterostructure, for example, Ge/Si heterostructure from SiGe solid solutions, and the second stage is characterized by formation of nanocones by mechanical plastic deformation of the compressed Ge layer on Si due to mismatch of Si and Ge crystalline lattices. The mechanism of nanocone formation for elementary semiconductors is not clear until now. Therefore, the main goal of our investigations is to study the stages of nanocone formation in elementary semiconductors. A new mechanism of p-n junction formation by laser radiation in the elementary semiconductor as a first stage of nanocone formation is proposed. We explain this effect by the following way: p-n junction is formed by generation and redistribution of intrinsic point defects in temperature gradient field – the thermogradient effect, which is caused by strongly absorbed laser radiation. According to the thermogradient effect, interstitial atoms drift towards the irradiated surface, but vacancies drift to the opposite direction – in the bulk of semiconductor. Since interstitials in Ge crystal are of n-type and vacancies are known to be of p-type, a n-p junction is formed. The mechanism is confirmed by the appearance of diode-like current–voltage characteristics after i-Ge irradiation crystal by laser radiation. The mechanism in Si is confirmed by conductivity type inversion and increased microhardness of Si crystal. The second stage of nanocone formation is laser heating up of top layer enriched by interstitial atoms with its further plastic deformation due to compressive stress caused by interstitials in the top layer and vacancies in the buried layer. PMID:22849869

  2. In vitro effects of argon laser radiation on blood: quantitative and morphologic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Abela, G.S.; Crea, F.; Smith, W.; Pepine, C.J.; Conti, C.R.

    1985-02-01

    Use of the argon laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 84 samples of citrated whole blood were exposed to argon laser radiation with varying power (1, 2 and 3 watts) and duration (5, 10, 20 and 40 seconds). Compared with control samples, only blood samples exposed to a power of 3 watts for 40 seconds showed a marked decrease in hematocrit (from 37 +/- 1.3 to 33 +/- 1.4%, p less than 0.01) and a marked increase in both free hemoglobin concentration (from 0.2 +/- 0.2 to 1.3 +/- 0.5 g/100 ml, p less than 0.01) and debris weight (from 0.9 +/- 0.3 to 2.8 +/- 0.5 mg, p less than 0.01). Scanning electron microscopy of debris from samples of whole blood, washed erythrocytes and platelet-rich plasma lased at 3 watts for 40 seconds documented the presence of membrane denaturation of blood elements, resulting in their fusion to form complex mesh-like conglomerates. Similar morphologic changes were observed in whole blood samples exposed to a ''hot tip'' rather than laser radiation. These data indicate that: 1) argon laser radiation with a power of 3 watts does not produce apparent hemolysis or debris formation for exposure periods up to 20 seconds, and 2) the effects of laser radiation on blood are probably mediated by thermal denaturation of cell membranes, as suggested by the same morphologic changes produced by thermal injury from a ''hot tip.''

  3. Influence of Welding Current and Focal Position on the Resonant Absorption of Laser Radiation in a TIG Welding Arc

    Science.gov (United States)

    Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.

    The work presents the influence of welding current and focal position on the resonant absorption of diode laser radiation in a TIG welding arc. The laser beam is guided perpendicular to the electrical arc to avoid an interaction with the electrodes. Laser power measurements have shown a reduction of the measured laser power up to 18% after passing the electrical arc. This reduction results from the interaction of argon shielding gas atoms and laser radiation at 810.4 nm and 811.5 nm. The interaction is strongly affected by the adjusted welding current and the adjustment of the laser beam and the electrical arc. Lowering the welding current or shifting the laser beam out of the centerline of the electrical arc reduces the ionization probability. An increased ionization is necessary to decrease the resistance of the electrical arc.

  4. Development of short pulse laser driven micro-hohlraums as a source of EUV radiation

    Science.gov (United States)

    Krushelnick, Karl; Batson, Thomas; McKelvey, Andrew; Raymond, Anthony; Thomas, Alec; Yanovsky, Victor; Nees, John; Maksimchuk, Anatoly

    2015-11-01

    Experiments at large scale laser facilities such as NIF allow the radiativ properties of dens, high-temperature matter to be studied at previously unreachable regime, but are limited by cost and system availability. A scaled system using a short laser pulses and delivering energy to much smaller hohlraum could be capable of reaching comparable energy densities by depositing the energy in a much smaller volume before ablation of the wall material closes the cavit. The laser is tightl focused through the cavity and then expands to illuminate the wall. Experiments were performe using the Hercules Ti:Sapphire laser system at Michiga. Targets include cavities machined in bulk material using low laser power, and then shot in situ with a single full power pulse as well as micron scale pre-fabricate target. Spectral characteristics were measured using a soft X-ray spectromete, K-alpha x-ray imaging system and a filtered photo cathode array. Scalings of the radiation temperature were made for variations in the hohlraum cavit, the pulse duration as well as the focusing conditions. Proof of principle time resolved absorption spectroscopy experiments were also performe. These sources may allow opacity and atomic physics measurements with plasma an radiation temperatures comparable to much larger hohlraums, but with much higher repetition rate and in a university scale laboratory. We acknowledge funding from DTRA grant HDTRA1-11-1-0066.

  5. Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge

    Science.gov (United States)

    Kamrukov, A. S.; Kozlov, Nicolay P.; Opekan, A. G.; Protasov, Yuri S.; Rudoi, I. G.; Soroka, A. M.

    1991-09-01

    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar equals 1:250) and the total pressure was 1 atm, the output energy was approximately 0.5 in the form of pulses of approximately 10 microsecond(s) duration, and maximum specific output energy represented by laser radiation was 1-2 J/l. The unsaturated gain was 27 m. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated; it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered, and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  6. Scattering effect in radiative heat transfer during selective laser sintering of polymers

    Science.gov (United States)

    Liu, Xin; Boutaous, M'hamed; Xin, Shihe

    2016-10-01

    The aim of this work is to develop an accurate model to simulate the selective laser sintering (SLS) process, in order to understand the multiple phenomena occurring in the material and to study the influence of each parameter on the quality of the sintered parts. A numerical model, coupling radiative and conductive heat transfers in a polymer powder bed providing a local temperature field, is proposed. To simulate the polymer sintering by laser heating as in additive manufacturing, a double-lines scanning of a laser beam over a thin layer of polymer powder is studied. An effective volumetric heat source, using a modified Monte Carlo method, is estimated from laser radiation scattering and absorption in a semi-transparent polymer powder bed. In order to quantify the laser-polymer interaction, the heating and cooling of the material is modeled and simulated with different types heat sources by both finite elements method (FEM) and discrete elements method (DEM). To highlight the importance of introducing a semi-transparent behavior of such materials and in order to validate our model, the results are compared with works taken from the literature.

  7. Echo-enabled tunable terahertz radiation generation with a laser-modulated relativistic electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Wang

    2014-09-01

    Full Text Available A new scheme to generate narrow-band tunable terahertz (THz radiation using a variant of the echo-enabled harmonic generation is analyzed. We show that by using an energy chirped beam, THz density modulation in the beam phase space can be produced with two lasers having the same wavelength. This removes the need for an optical parametric amplifier system to provide a wavelength-tunable laser to vary the central frequency of the THz radiation. The practical feasibility and applications of this scheme are demonstrated numerically with a start-to-end simulation using the beam parameters at the Shanghai Deep Ultraviolet Free-Electron Laser facility (SDUV. The central frequency of the density modulation can be continuously tuned by either varying the chirp of the beam or the momentum compactions of the chicanes. The influence of nonlinear rf chirp and longitudinal space charge effect have also been studied in our article. The methods to generate the THz radiation in SDUV with the new scheme and the estimation of the radiation power are also discussed briefly.

  8. Effects of Soft-Core Potentials and Coulombic Potentials on Bremsstrahlung Radiation during Laser Matter Interaction

    Science.gov (United States)

    Pandit, Rishi; Sentoku, Yasuhiko; Sawada, Hiroshi; Ramunno, Lora; Ackad, Edward

    2017-10-01

    An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, both from phonons and ions, they emit bremsstrahlung radiation. Here we compare a theory of Bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and coulombic potential. A new scaling for the radiation cross-section and Emissivity via bremsstrahlung are derived for soft-core potential which depends on the potential depth, used to avoid coulomb singularity and for coulombic potential and implemented in a particle in cell code (PICLS). The radiation cross-section and emissivity via bremsstrahlung is found to increase rapidly with increases in potential depth up to 100 eV and then becomes mostly saturated for larger depths of a soft-core potential. For both cases, the radiation cross-section and emissivity of Bremsstrahlung increases with increases in laser wavelength. The bremsstrahlung emission may provide a broadband light source for diagnostics. This work was supported by Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0247.

  9. Modification in oxidative processes in muscle tissues exposed to laser- and light-emitting diode radiation.

    Science.gov (United States)

    Monich, Victor A; Bavrina, Anna P; Malinovskaya, Svetlana L

    2018-01-01

    Exposure of living tissues to high-intensity red or near-infrared light can produce the oxidative stress effects both in the target zone and adjacent ones. The protein oxidative modification (POM) products can be used as reliable and early markers of oxidative stress. The contents of modified proteins in the investigated specimens can be evaluated by the 2,4-dinitrophenylhydrazine assay (the DNPH assay). Low-intensity red light is able to decrease the activity of oxidative processes and the DNPH assay data about the POM products in the biological tissues could show both an oxidative stress level and an efficiency of physical agent protection against the oxidative processes. Two control groups of white rats were irradiated by laser light, the first control group by red light and the second one by near-infrared radiation (NIR).Two experimental groups were consequently treated with laser and red low-level light-emitting diode radiation (LED). One of them was exposed to red laser light + LED and the other to NIR + LED. The fifth group was intact. Each group included ten animals. The effect of laser light was studied by methods of protein oxidative modifications. We measured levels of both induced and spontaneous POM products by the DNPH assay. The dramatic increase in levels of POM products in the control group samples when compared with the intact group data as well as the sharp decrease in the POM products in the experimental groups treated with LED low-level light were statistically significant (p ≤ 0.05). Exposure of skeletal muscles to high-intensity red and near-infrared laser light causes oxidative stress that continues not less than 3 days. The method of measurement of POM product contents by the DNPH assay is a reliable test of an oxidative process rate. Red low-intensity LED radiation can provide rehabilitation of skeletal muscle tissues treated with high-intensity laser light.

  10. Synthesis and characterization of CdSe/ZnS core-shell quantum dots immobilized on solid substrates through laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, E. [Centre d' Investigacions en Nanociencia i Nanotecnologia, Institut Catala de Nanotecnologia, Consejo Superior de Investigaciones Cientificas (CIN2, ICN-CSIC), Bellaterra (Spain); National Institute for Lasers, Plasma and Radiation Physics, Bucharest (Romania); Perez del Pino, A. [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB, CSIC), Bellaterra (Spain); Roqueta, J.; Ballesteros, B. [Centre d' Investigacions en Nanociencia i Nanotecnologia, Institut Catala de Nanotecnologia, Consejo Superior de Investigaciones Cientificas (CIN2, ICN-CSIC), Bellaterra (Spain); Miguel, A.S.; Maycock, C.; Oliva, A.G. [Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa (ITQB-UNL), Oeiras (Portugal)

    2012-11-15

    CdSe/ZnS core-shell quantum dots (QDs) have been immobilized onto solid substrates by matrix assisted pulsed laser evaporation (MAPLE). An UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 25 ns) excimer laser source was used for irradiations of the composite MAPLE targets. The targets were prepared by the dispersion of the CdSe/ZnS QDs in a solvent with high absorption at the incident laser radiation. The dependence of the surface morphology, crystalline structure, chemical composition, and functional properties of the laser transferred CdSe/ZnS QDs on the processing conditions as incident laser fluence value and ambient atmosphere inside the irradiation chamber was investigated. The possible physical mechanisms implied in the laser ablation process were identified. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Investigation of Doppler spectra of laser radiation scattered inside hand skin during occlusion test

    Science.gov (United States)

    Kozlov, I. O.; Zherebtsov, E. A.; Zherebtsova, A. I.; Dremin, V. V.; Dunaev, A. V.

    2017-11-01

    Laser Doppler flowmetry (LDF) is a method widely used in diagnosis of microcirculation diseases. It is well known that information about frequency distribution of Doppler spectrum of the laser radiation scattered by moving red blood cells (RBC) usually disappears after signal processing procedure. Photocurrent’s spectrum distribution contains valuable diagnostic information about velocity distribution of the RBC. In this research it is proposed to compute the indexes of microcirculation in the sub-ranges of the Doppler spectrum as well as investigate the frequency distribution of the computed indexes.

  12. Radiative processes in air excited by an ArF laser

    Science.gov (United States)

    Laufer, Gabriel; Mckenzie, Robert L.; Huo, Winifred M.

    1988-01-01

    The emission spectrum of air that is excited by an ArF laser has been investigated experimentally and theoretically to determine the conditions under which fluorescence from O2 can be used for the measurement of temperature in aerodynamic flows. In addition to the expected fluorescence from O2, the spectrum from excitation with an intense laser beam is shown to contain significant contributions from the near-resonant Raman fundamental and overtone bands, the four-photon fluorescence excitation of C produced from ambient CO2, and possibly the three-photon excitation of O(2+). The nature of the radiative interactions contributing to these additional features is described.

  13. Thermoelastic Property of a Semi-Infinite Medium Induced by a Homogeneously Illuminating Laser Radiation

    Directory of Open Access Journals (Sweden)

    Tayel I. M.

    2008-10-01

    Full Text Available The problem of thermoelasticity, based on the theory of Lord and Shulman with one relaxation time, is used to solve a boundary value problem of one dimensional semi-infinite medium heated by a laser beam having a temporal Dirac distribution. The surface of the medium is taken as traction free. The general solution is obtained using the Laplace transformation. Small time approximation analysis for the stresses, displacement and temperature are performed. The convolution theorem is applied to get the response of the system on temporally Gaussian distributed laser radiation. Results are presented graphically. Concluding that the small time approximation has not affected the finite velocity of the heat conductivity.

  14. Ultraviolet out-of-band radiation studies in laser tin plasma sources

    Science.gov (United States)

    Parchamy, Homaira; Szilagyi, John; Masnavi, Majid; Richardson, Martin

    2017-11-01

    Out-of-band long wavelength emission measurements from high power, high-repetition-rate extreme-ultra-violet lithography (EUVL) laser plasma sources are imperative to estimating heat deposition in EUV mirrors, and the impact of short wavelength light transported through the imaging system to the wafer surface. This paper reports a series of experiments conducted to measure the absolute spectral irradiances of laser-plasmas produced from planar tin targets over the wavelength region of 124 to 164 nm by 1.06 μm wavelength, 10 ns full-width-at-half-maximum Gaussian laser pulses. The use of spherical targets is relevant to the EUVL source scenario. Although plasmas produced from planar surfaces evolve differently, there is a close similarity to the evolution of current from 10.6 μm CO2 laser EUVL sources, which use a pre-pulse from a lower energy solid-state laser to melt and reform an initial spherical droplet into a thin planar disc target. The maximum of radiation conversion efficiency in the 124-164 nm wavelength band (1%/2πsr) occurs at the laser intensity of 1010 W cm-2. A developed collisional-radiative model reveals the strong experimental spectra that originate mainly from the 4d105p2-4d105s5p, 4d105p-4d105s resonance lines, and 4d95p-4d95s unresolved transition arrays from Sn III, Sn IV, and Sn V ions, respectively. The calculated conversion efficiencies using a 2D radiation-hydrodynamics model are in agreement with the measurements. The model predicts the out-of-band (100-400 nm) radiation conversion efficiencies generated by both 1.06 and 10.6 μm pulses. The 10.6 μm laser pulse produces a higher conversion efficiency (12%/2πsr) at the lower laser intensity of 109 W cm-2.

  15. Statistical and coherence properties of radiation from X-ray free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    2009-12-15

    We describe statistical and coherence properties of the radiation from X-ray free electron lasers (XFEL). It is shown that the X-ray FEL radiation before saturation is described with gaussian statistics. Particularly important is the case of the optimized X-ray FEL, studied in detail. Applying similarity techniques to the results of numerical simulations allowed us to find universal scaling relations for the main characteristics of an X-ray FEL operating in the saturation regime: efficiency, coherence time and degree of transverse coherence. We find that with an appropriate normalization of these quantities, they are functions of only the ratio of the geometrical emittance of the electron beam to the radiation wavelength. Statistical and coherence properties of the higher harmonics of the radiation are highlighted as well. (orig.)

  16. Laser in ophthalmology. Laser i oftalmologien

    Energy Technology Data Exchange (ETDEWEB)

    Syrdalen, P. (Rikshospitalet, Oslo (Norway))

    1991-09-01

    The article presents a brief history of the use of laser in ophthalmology in Norway, from the introduction of the first argon-photocoalulator in 1972 to the excimer laser in 1990. The argon-photocoagulator is in daily us in all Eye Departments in Norway and the main group of patients treated are those with diabetic retionopathy. Glaucoma has been treated with argon-laser with good results for the last ten years. YAG-laser, introduced in Norway in 1985, is used to treat secondary cataracts which occur after extracapsular cataract extractions and implantation of artificial lenses. In 1990, the excimer laser was introduced for refractive surgery (myopia, astigmatism). 4 refs., 6 figs., 1 tab.

  17. Laser Radiation Induces Growth and Lipid Accumulation in the Seawater Microalga Chlorella pacifica

    Directory of Open Access Journals (Sweden)

    Haonan Zhang

    2017-10-01

    Full Text Available The impacts of laser radiation (Nd: YAG laser, 1064 nm at 800 mW, He–Ne laser 808 nm at 6 W, semiconductor laser 632.8 nm at 40 mW on growth and lipid accumulation of Chlorella pacifica were investigated in this study. The results showed growth rates increased 1.23, 1.41, and 1.40-fold over controls by 4 min Nd: YAG, 4 min He–Ne, and 8 min semiconductor laser treatments, respectively, whereas the corresponding nitrate reductase observed increased 1.25, 1.63, and 2.08-fold over controls. Moreover, total chlorophyll concentration was increased to 1.09, 1.29, and 1.33-fold over controls, respectively. After 20 days cultivation, the highest lipid content was 35.99%, 18.46%, and 31.00% after 2 min Nd: YAG, 4 min He–Ne, and 4 min semiconductor laser treatments, corresponding to 2.86, 1.50, and 2.46-fold increase over controls, respectively. Furthermore, the lipid productivity of the above 3 treatments were 15.25 ± 2.56, 16.25 ± 2.45, and 14.75 ± 2.11 mg L−1 d−1. However, the highest lipid productivity was 22.00 ± 3.28, 16.25 ± 2.45, and 19.25 ± 1.78 mg L−1 d−1, in response to treatment for 2 min Nd: YAG, 1 min He–Ne, and 4 min semiconductor laser treatments, with 2.67, 1.97, and 2.33-fold increase over controls, respectively. These results indicated that lipid accumulation efficiency of C. pacifica could be significantly improved by laser irradiation using Nd: YAG, He–Ne, and semiconductor laser treatments.

  18. Biological Effects of Laser Radiation. Volume I. Review of the Literature on Biological Effects of Laser Radiation-to 1965.

    Science.gov (United States)

    1978-10-17

    to coaz-%eta brea -ccoia of the Vessel wall. ’oc’e - d Baez corclae fro-u: their- studies that the vessel wallI -rinoled in ti’zo:-.borenesds, but tic...embryo in early pregnancy is probably not feasible. Other mammalian species may provide a better basis fdr production of localized superficial lesions in...of laser irradiation on e rp-ariz-ntal ti-ors, presented at the Amrican Association for Cancer Research, April 1964, Chicago, Illinois. 20. Klein, 1

  19. X-ray spectra of plasma radiation from laser induced low-power vacuum discharge

    Science.gov (United States)

    Romanov, I. V.; Kologrivov, A. A.; Paperny, V. L.; Rupasov, A. A.; Starodub, A. N.

    2018-02-01

    The x-ray spectra of plasma radiation in the wavelength range 30–300 Å are studied. The radiation is emitted from plasma of a vacuum discharge with storage energy less than 30 J that is initiated on an Al or Fe cathode by beam from neodymium laser with a power density up to 1012 W cm‑2. It is shown that both the spectral composition and intensity of radiation of hot micropinch plasma that is formed in the cathodic jet are determined by the set of the discharge and the laser pulse characteristics. By optimizing these characteristics, a mode of the discharge operation is attainable, in which a significant portion of the radiation energy is located in the long-wave band of the quasi-continuum (230–270 Å and 160–200 Å for Al and Fe cathodes, respectively). That makes it possible to treat such a discharge as an intense source of narrow-band soft x-ray radiation.

  20. Interaction of mid-infrared laser radiation with soft ureter tissue

    Science.gov (United States)

    Jelinkova, Helena; Kohler, Oto; Nemec, Michal; Koranda, Petr; Sulc, Jan; Drlik, Pavel; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji; Kokta, Milan R.; Hrabal, Petr

    2004-09-01

    Aim of the work was an investigation of ureter wall perforation possibility by various types of mid-infrared radiations (from 2.01 μm (Tm:YAG) up to 2.94 μm (Er:YAG)) and exploration of the interaction basic characteristic for ureter surface (epithelium) and its deep structures (mesenchym). From results follow that CTH:YAG, Er:YAG, and CTE:YAG laser radiations accomplish a good wall ureter perforation. A distinguished difference appeared in modifications of the ureter tissue - epithelium and mesenchym.

  1. Laser-plasma accelerator and femtosecond photon sources-based ultrafast radiation chemistry and biophysics

    Science.gov (United States)

    Gauduel, Y. A.

    2017-02-01

    The initial distribution of energy deposition triggered by the interaction of ionizing radiations (far UV and X rays, electron, proton and accelerated ions) with molecular targets or integrated biological systems is often decisive for the spatio-temporal behavior of radiation effects that take place on several orders of magnitude. This contribution deals with an interdisciplinary approach that concerns cutting-edge advances on primary radiation events, considering the potentialities of innovating strategies based on ultrafast laser science, from femtosecond photon sources to laser-driven relativistic particles acceleration. Recent advances of powerful TW laser sources (~ 1019 Wcm-2) and laser-plasma interactions providing ultrashort relativistic particle beams in the energy domain 2.5-150 MeV open exciting opportunities for the development of high-energy radiation femtochemistry (HERF). Early radiation damages being dependent on the survival probability of secondary electrons and radial distribution of short-lived radicals inside ionization clusters, a thorough knowledge of these processes involves the real-time probing of primary events in the temporal range 10-14-10-11 s. In the framework of a closed synergy between low-energy radiation femtochemistry (LERF) and the emerging domain of HERF, the paper focuses on early phenomena that occur in the prethermal regime of low-energy secondary electrons, considering very short-lived quantum effects in aqueous environments. A high dose-rate delivered by femtosecond electron beam (~ 1011-1013 Gy s-1) can be used to investigate early radiation processes in native ionization tracks, down to 10-12 s and 10-9 m. We explain how this breakthrough favours the innovating development of real-time nanodosimetry in biologically relevant environments and open new perspectives for spatio-temporal radiation biophysics. The emerging domain of HERF would provide guidance for understanding the specific bioeffects of ultrashort particle

  2. Treatment of compounds and alloys in radiation hydrodynamics simulations of ablative laser loading.

    Science.gov (United States)

    Swift, Damian C; Gammel, J Tinka; Clegg, Samuel M

    2004-05-01

    Different methods were compared for constructing models of the behavior of a prototype intermetallic compound, nickel aluminide, for use in radiation hydrodynamics simulations of shock wave generation by ablation induced by laser energy. The models included the equation of state, ionization, and radiation opacity. The methods of construction were evaluated by comparing the results of simulations of an ablatively generated shock wave in a sample of the alloy. The most accurate simulations were obtained using the "constant number density" mixture model to calculate the equation of state and opacity, and Thomas-Fermi ionization. This model is consistent with that found to be most accurate for simulations of ablatively shocked elements.

  3. Localized dispersing of ceramic particles in tool steel surfaces by pulsed laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hilgenberg, K., E-mail: hilgenberg@uni-kassel.de [Metal Forming Technology, University of Kassel (Germany); Behler, K. [Laser Technology, THM University of Applied Sciences (Germany); Steinhoff, K. [Metal Forming Technology, University of Kassel (Germany)

    2014-06-01

    In this paper the capability of a localized laser dispersing technique for changing the material microstructure and the surface topology of steels is discussed. The laser implantation named technique bases on a discontinuous dispersing of ceramic particles into the surface of steels by using pulsed laser radiation. As ceramic particles TiC, WC and TiB{sub 2} are used, substrate material is high-alloyed cold working steel (X153CrMoV12). The influence of the laser parameters pulse length and pulse intensity was investigated in a comprehensive parameter study. The gained surface topology and microstructure were evaluated by optical microscopy, energy dispersive X-ray spectroscopy (EDX) and white light interferometry; mechanical properties were analyzed by micro hardness measurement. The experiments reveal that the alignment of separated, elevated, dome-shaped spots on the steel surface is feasible. The geometrical properties as well as the mechanical properties are highly controllable by the laser parameters. The laser implanted spots show a mostly crack-free and pore-free bonding to the substrate material as well as a significant increase of micro hardness.

  4. Localized dispersing of ceramic particles in tool steel surfaces by pulsed laser radiation

    Science.gov (United States)

    Hilgenberg, K.; Behler, K.; Steinhoff, K.

    2014-06-01

    In this paper the capability of a localized laser dispersing technique for changing the material microstructure and the surface topology of steels is discussed. The laser implantation named technique bases on a discontinuous dispersing of ceramic particles into the surface of steels by using pulsed laser radiation. As ceramic particles TiC, WC and TiB2 are used, substrate material is high-alloyed cold working steel (X153CrMoV12). The influence of the laser parameters pulse length and pulse intensity was investigated in a comprehensive parameter study. The gained surface topology and microstructure were evaluated by optical microscopy, energy dispersive X-ray spectroscopy (EDX) and white light interferometry; mechanical properties were analyzed by micro hardness measurement. The experiments reveal that the alignment of separated, elevated, dome-shaped spots on the steel surface is feasible. The geometrical properties as well as the mechanical properties are highly controllable by the laser parameters. The laser implanted spots show a mostly crack-free and pore-free bonding to the substrate material as well as a significant increase of micro hardness.

  5. The influence of laser radiation on human osteoblasts cultured on nanostructured composite substrates.

    Science.gov (United States)

    Crisan, Liana; Soritau, Olga; Baciut, Mihaela; Baciut, Grigore; Crisan, Bogdan Vasile

    2015-01-01

    Carbon-based nanomaterials such as carbon nanotubes, graphene oxide and graphene have been explored by researchers as well as the industry. Graphene is a new nanomaterial which has commercial and scientific advantages. Laser therapy has proven highly useful in biomedicine, with the use of different laser types and energies for distinct purposes. The low level laser therapy (LLLT) can have anti-inflammatory, analgesic and biostimulant effects. Recent research has shown that laser radiation has different effects on osteoblasts. The aim of this study was to identify the influence of laser radiation on human osteoblastic cells cultured on nanostructured composite substrates. Four types of substrates were created using colloidal suspensions of nanostructured composites in PBS at a concentration of 30 μg/ml. We used human osteoblasts isolated from patella bone pieces harvested during arthroplasty. Irradiation of osteoblasts cultured on nanostructured composite substrates was made with a semiconductor laser model BTL-10 having a wavelength of 830 nm. The proliferation activity of osteoblast cells was assessed using the MTT assay. After laser irradiation procedure the viability and proliferation of osteoblast cells were analyzed using fluorescein diacetate (FDA) staining. The osteoblast cells viability and proliferation were evaluated with MTT assay at 30 minutes, 24 hours, 5 days and 10 days after laser irradiation. In the first 30 minutes there were no significant differences between the irradiated and non-irradiated cells. At 24 hours after laser irradiation procedure a significant increase of MTT values in case of irradiated osteoblasts cultivated on nanostructured hydroxyapatite, nanostructured hydroxyapatite with gold nanoparticles and 1.6% and 3.15% graphenes composites substrates was observed. A more marked proliferation rate was observed after 10 days of irradiation for irradiated osteoblasts seeded on nanostructured hydroxyapatite with gold nanoparticles and

  6. Effects of IR laser radiation in thyroid follicular cells: fine structural and stereological study

    Science.gov (United States)

    Vidal, Lourdes; Perez de Vargas, I.; Ruiz, C.; Parrado, C.; Pelaez, A.

    1993-06-01

    We have examined the results obtained from the stereological ultraestructural study of follicular cells in thyroid glands treated with IR laser (904 nm). We studied 40 wistar rats exposed to radiation with doses of 46,80 J/cm2. They were sacrificed 1 and 180 days after the treatment. A stereological study of the volume and surface density was made in mitochondria, rER. Gogi complex and cytoplasmic granules. In the rats sacrificed 1 day after exposure to laser radiation, the thyrocited showed minimal morphological changes. In the rats sacrificed after a long period (180 days) the thyrocites showed a significant increase of volume and surface densities of rER, that may mean decreased capacity of the cells to synthesize thyroglobulin. Volume and surface densities of the citoplasmic granules experienced a significant increase.

  7. Modeling of terahertz radiation emission from a free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Suresh C.; Panwar, Jyotsna; Sharma, Rinku [Department of Applied Physics, Delhi Technological University, Delhi (India)

    2017-05-15

    In this article, we report the generation of terahertz (THz) radiation using the interaction of a laser-modulated relativistic electron beam (REB) with a surface plasma wave. Two laser beams propagating through the modulator interact with the REB, leading to velocity modulation of the beam. This results in pre-bunching of the REB. The pre-bunched beam travels through the drift space, where the velocity modulation translates into density modulation. The density-modulated beam, on interacting with the surface plasma pump wave, acquires an oscillatory velocity that couples with the modulated beam density to give rise to a nonlinear current density which acts as an antenna to give THz radiation. By optimizing the parameters of the beam and the wiggler, we obtain power of the order of 10{sup -4} using the current scheme. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Design and fabrication of radiation shielded laser ablation ICP-MS system

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Yeong Keong; Han, Sun Ho; Park, Soon Dal; Park, Yang Soon; Jee, Kwang Yong; Kim, Won Ho

    2006-09-15

    In relation to high burn up and extended fuel cycle for the fuel cycle efficiency, we need to take chemical analysis of spent nuclear fuel for the integrity of nuclear fuel at high burn up. to measure the isotopic distribution of fission product in a high burn up nuclear fuel, radiation shielded laser ablation system was designed and fabricated. By probing the sample with a laser beam, micro sampling system for the mass analyzer was successfully developed. This report describes the structural design and the function of developed radiation shielded LA system. This system will be used for the analysis of isotopic distribution from core to rim of a spent nuclear fuel prepared from the hot-cell in PIE facility and/or an irradiated fuel from research reactor.

  9. Ultraintense laser absorption and γ-ray synchrotron radiation in near critical density plasmas

    Science.gov (United States)

    Chang, H. X.; Qiao, B.; Zhang, Y. X.; Xu, Z.; Yao, W. P.; Zhou, C. T.; He, X. T.

    2017-04-01

    Ultraintense laser absorption and γ-ray synchrotron radiation in near-critical-density (NCD) plasmas are investigated. Besides the known skin-depth emission and reinjected electron synchrotron emission in NCD plasmas, we find a new γ-ray emission mechanism, where γ-rays are dominantly produced by the Transversely Oscillating Electron synchrotron Emission (TOEE). In this new TOEE mechanism, electrons mainly oscillate in the transverse direction under the balance between the longitudinal laser ponderomotive force and the restoring electrostatic force. A great amount of γ photons are emitted in the transverse direction, where the peak radiation power is enhanced by twice and the photon divergence angle is relatively decreased. The features of γ-rays produced from this new TOEE mechanism have been identified and compared with the other two mechanisms by two-dimensional particle-in-cell simulations.

  10. Interaction of cw CO2 laser radiation with plasma near-metallic substrate surface

    Science.gov (United States)

    Azharonok, V. V.; Astapchik, S. A.; Zabelin, Alexandre M.; Golubev, Vladimir S.; Golubev, V. S.; Grezev, A. N.; Filatov, Igor V.; Chubrik, N. I.; Shimanovich, V. D.

    2000-07-01

    Optical and spectroscopic methods were used in studying near-surface plasma that is formed under the effect CW CO2 laser of (2- 5)x106W/cm2 power density upon stainless steel in He and Ar shielding gases. The variation of plume spatial structure with time has been studied, the outflow of gas-vapor jets from the interaction area has been characterized. The spectra of plasma plume pulsations have been obtained for the frequency range Δf = 0-1 MHz. The temperature and electron concentration of plasma plume have been found under radiation effect upon the target of stainless steel. Consideration has been given to the most probable mechanisms of CW laser radiation-metal non-stationary interaction.

  11. Influence of nuclear radiation and laser beams on optical fibers and components

    Directory of Open Access Journals (Sweden)

    Pantelić Slađana N.

    2011-01-01

    Full Text Available The influence of nuclear radiation and particles has been the object of investigation for a long time. For new materials and systems the research should be continued. Human activities in various environments, including space, call for more detailed research. The role of fibers in contemporary communications, medicine, and industry increases. Fibers, their connections and fused optics components have one type of tasks - the transmission of information and power. The other type of tasks is reserved for fiber lasers: quantum generators and amplifiers. The third type of tasks is for fiber sensors, including high energy nuclear physics. In this paper we present some chosen topics in the mentioned areas as well as our experiments with nuclear radiation and laser beams to fiber and bulk materials of various nature (glass, polymer, metallic, etc..

  12. 3D microstructuring with F2 lasers

    Science.gov (United States)

    Toenshoff, Hans K.; von Alvensleben, Ferdinand; Ostendorf, Andreas; Koerber, Klaus; Kulik, Christian

    2000-09-01

    F2 lasers emitting radiation with a wavelength (lambda) equals 157 nm allow the direct laser based micro-structuring of materials like PTFE (e.g. Teflon) or quartz glass for MST-applications. This paper reports about the fundamental basis of controlling and modelling the structuring process and about existing tools for the 3-D micron structuring with F2 excimer lasers. The concept of three-dimensional micro-structuring is based on gradual ablation, using single laser pulses. A CNC-controlled precision machining centre with a vacuum encapsulated beam guiding system has been developed. For the material processing with F2 lasers a model of the single ablation size was qualified, which provides an exact description of the laser pulse taking the material properties, the energy density and the lateral dimensions of the single ablation into account. The non- linear characteristics between pulse geometry and process parameters were experimentally determined and implemented into software for automated NC-data generation. A special software tool makes the simulation of manufacturing micro-components possible. It is based on the complex NC-code and on the exact model of the single ablation. Using this simulation, the process parameters can be optimised before processing with a laser micro-machining centre. The described technology was verified by manufacturing 3-D micro-structures in several materials, such as quartz glass and PTFE.

  13. Deposition and characterization of ITO films produced by laser ablation at 355 nm

    DEFF Research Database (Denmark)

    Holmelund, E.; Thestrup Nielsen, Birgitte; Schou, Jørgen

    2002-01-01

    and at high substrate temperatures, the specific resistivity of the films, 2–3×10-4 Ω cm, is comparable to values obtained with excimer lasers, whereas the resistivities obtained at room temperature are somewhat higher than those of films produced by excimer lasers. The transmission coefficient of visible...... light, about 0.9, is also comparable to values for films deposited by excimer lasers. The crystalline structure of films produced at 355 nm is similar to that of samples produced by these lasers.......Indium tin oxide (ITO) films have been deposited by pulsed laser deposition (PLD) at 355 nm. Even though the absorption of laser light at the wavelength 355 nm is much smaller than that of the standard excimer lasers for PLD at 248 nm and 193 nm, high-quality films can be produced. At high fluence...

  14. Research on the shooting accuracy of ICF laser device based on radiation fluid

    Science.gov (United States)

    Zhang, Xiaolu; Zeng, Fa; Wang, Shenzhen; Zhao, Junpu; Xue, Qiao; Dai, Wanjun

    2017-10-01

    The shooting accuracy of cluster laser is an important indicator to evaluate the performance of ICF laser devices. By measuring the distribution of the X-ray generated from interaction between the third-harmonic beam and the target, the position information of the third-harmonic beam to the target can be obtained, along with the shooting accuracy. In the beam transmission process, the fundamental, second-harmonic beams and the third-harmonic beams approach to the target at the same time generating spurious X-ray. Based on the radiation fluid, the present paper is to assess the effect of the stray light on the performance of the shooting accuracy. The intensity distribution and power density of the fundamental, second-harmonic and third-harmonic beams at the target position were calculated for the SG-III laser device using SG-99 software. The characteristics of X-ray generated by the different beams radiation are simulated by one-dimensional radiation fluid program MULTI 1D. The results show that the power density of the fundamental, the second-harmonic and third-harmonic beams at the target position are, under the condition of typical shooting precision test (infused fundamental energy of 50J and pulse width is 200ps) 0.28GW / s / cm2 , 0.14GW / s / cm2 , 99GW / s / cm2 , respectively. The X-ray energy intensity radiated from the interaction between the third-harmonic beam and target is 104 times of that from the fundamental, second-harmonic beam. In the current optical system configuration conditions of SG-III laser device, the effects of the fundamental and second-harmonic beams on the target accuracy test can be ignored.

  15. Biomolecular urease thin films grown by laser techniques for blood diagnostic applications

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, E., E-mail: eniko.gyorgy@inflpr.ro [Consejo Superior de Investigaciones Cientificas, Institut de Ciencia de Materials de Barcelona and Centre d' Investigacions en Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Spain); National Institute for Lasers, Plasma and Radiations Physics, P. O. Box MG 36, 77125 Bucharest (Romania); Sima, F.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiations Physics, P. O. Box MG 36, 77125 Bucharest (Romania); Smausz, T. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary); Hopp, B. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Predoi, D. [National Institute for Physics of Materials, P.O. Box MG 07, Bucharest, Magurele (Romania); Sima, L.E.; Petrescu, S.M. [Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 060031 Bucharest (Romania)

    2010-05-10

    Matrix assisted pulsed laser evaporation (MAPLE) was used for growing urease thin films designed for bio-sensor applications in clinical diagnostics. The targets exposed to laser radiation were made from a frozen composite manufactured by dissolving biomaterials in distilled water. We used a UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 30 ns, {nu} = 10 Hz) excimer source for multipulse laser irradiation of the frozen targets cooled with Peltier elements. The laser source was operated at an incident fluence of 0.4 J/cm{sup 2}. Urease activity and kinetics were assayed by the Worthington method that monitors urea hydrolysis by coupling ammonia production to a glutamate dehydrogenase reaction. A decrease in absorbance was measured at 340 nm and correlated with the enzymatic activity of urease. We show that the urease films obtained by MAPLE techniques remain active up to three months after deposition.

  16. A path to practical Solar Pumped Lasers via Radiative Energy Transfer.

    Science.gov (United States)

    Reusswig, Philip D; Nechayev, Sergey; Scherer, Jennifer M; Hwang, Gyu Weon; Bawendi, Moungi G; Baldo, Marc A; Rotschild, Carmel

    2015-10-05

    The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd(3+)-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm(-2), or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.

  17. BRIEF COMMUNICATIONS: Bleaching-wave laser excited by radiation from magnetoplasma compressors

    Science.gov (United States)

    Kamrukov, A. S.; Logunov, O. A.; Ovchinnikov, P. A.; Protasov, Yu S.; Startsev, Aleksandr V.; Stoĭlov, Yu Yu

    1989-04-01

    A bleaching-wave laser (utilizing an ether solution of coumarin 6 and 1,4-diphenylbutadiene) was pumped by a flashlamp-type source utilizing magnetoplasma compressors. When the bleaching wave propagated in the solution at a velocity of ~ 1 km/s, cw lasing was obtained for 30-40 μs with an output energy of 1.2 J in the 517 ± 5 nm range. Estimates were made of the threshold pump intensity and of the internal losses in the bleaching-wave laser. It was found that, compared with a laser without a bleaching wave (utilizing an ethyl solution of coumarin 6), a bleaching wave improved greatly (under the same excitation conditions) the output energy and the directionality of the radiation.

  18. Synthesis of Glass Nanofibers Using Femtosecond Laser Radiation Under Ambient Condition

    Directory of Open Access Journals (Sweden)

    Venkatakrishnan K

    2009-01-01

    Full Text Available Abstract We report the unique growth of nanofibers in silica and borosilicate glass using femtosecond laser radiation at 8 MHz repetition rate and a pulse width of 214 fs in air at atmospheric pressure. The nanofibers are grown perpendicular to the substrate surface from the molten material in laser-drilled microvias where they intertwine and bundle up above the surface. The fibers are few tens of nanometers in thickness and up to several millimeters in length. Further, it is found that at some places nanoparticles are attached to the fiber surface along its length. Nanofiber growth is explained by the process of nanojets formed in the molten liquid due to pressure gradient induced from the laser pulses and subsequently drawn into fibers by the intense plasma pressure. The attachment of nanoparticles is due to the condensation of vapor in the plasma.

  19. The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 2: the consequences of treating astigmatism on an incorrect axis via excimer laser

    Directory of Open Access Journals (Sweden)

    Motwani M

    2017-05-01

    Full Text Available Manoj Motwani Motwani LASIK Institute, San Diego, CA, USA Purpose: To show how an incorrect manifest astigmatism axis can cause an abnormal induced astigmatism on a new axis. Patients and methods: Four eyes of three patients were treated primarily with WaveLight® EX500 wavefront optimized (WFO treatments for astigmatism. All four eyes needed enhancements and were analyzed retrospectively via WaveLight® Contoura to determine the reason for the incorrect astigmatism treatment. Two of the eyes were retreated with topographic-guided ablation, and two were treated with WFO correction. Results: The eyes that had an incorrect manifest axis resulted in a new abnormal induced astigmatism on a wholly new axis. Treatment with topographic-guided ablation completely eliminated the newly induced astigmatism. Treatment with WFO of an abnormal induced astigmatism corrected the refraction but still left topographic evidence of the abnormal astigmatism behind. One eye was incorrectly treated for astigmatism due to coma affecting refraction when the patient was dilated. This eye had a normal induced astigmatism on a perpendicular axis and was corrected using WFO. The use of manifest refraction with WaveLight® Contoura topographic-guided ablation will lead to incorrect astigmatism correction when the manifest astigmatism and axis differ from the WaveLight® Contoura measured. Conclusion: Correction of an incorrect manifest refraction astigmatic axis does not simply create undercorrection of the astigmatism but induces an entirely new abnormal astigmatism on a different axis. Manifest refraction is less accurate and can lead to abnormal astigmatism when laser ablation is performed. Keywords: WaveLight Contoura, astigmatism treatment, asymmetric astigmatism, topographic guide ablation, higher order aberrations, Contoura with LYRA Protocol, LASIK, PRK

  20. Intra-operative radiation therapy with laser-accelerated carbon ions

    Science.gov (United States)

    Mur, P.; Bellido, P.; Seimetz, M.; Lera, R.; Ruiz-de la Cruz, A.; Galán, M.; Roso, L.; Sánchez, F.; Benlloch, J. M.

    2017-03-01

    Laser accelerators have long been proposed as beam source for hadron therapy. However, the high energies necessary for the treatment of deep-lying tumours, combined with stringent requirements on the beam quality, are still a severe challenge. In the present work, we discuss the applicability of laser-accelerated carbon ions at moderate energies (100-480 MeV) to the irradiation of superficial lesions. We propose a new therapeutic modality which combines the versatility of Intra-Operative Radiation Therapy with the advantages of carbon ions as compared to photon and electron radiation. To justify this idea a feasibility study has been carried out, focused on the uniformity of dose deposition inside the treatment volume. Physical and biological aspects characteristic to laser-accelerated carbon ion beams are considered. A GATE simulation has been performed, showing an approximately uniform depth-dose profile up to a maximum penetration depth of 5 mm for a single radiation boost of 10 GyE.