Dissertations / Theses on the topic 'Excimer lasers'
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1
Retter, Mark Joseph. "PHOTODISSOCIATIVE GENERATION OF A POPULATION INVERSION FOR THE THALLIUM-MERCURY EXCIMER SYSTEM (LASERS, EXCIMERS)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275407.
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Richardson, Michael Brian. "Transputer control of excimer lasers." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238799.
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Dang, Ngoc Thierry. "Indications actuelles de la photokératectomie thérapeutique, à propos de 12 observations." Bordeaux 2, 1998. http://www.theses.fr/1998BOR23012.
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Wu, Fushun. "Nd:YAG and excimer lasers application aspects." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395661.
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Ford, Joseph Earl. "Investigations into the xenon chloride excimer laser." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24666.
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A discharge pumped LC inversion type XeCl excimer laser was constructed, and its discharge and output were examined. A maximum output energy of 167 mJ was achieved, with an efficiency of 0.56%, using 60 psi of a gas composed of 0.56% HCl, 2.48% Xe, 48.48% He, and 48.48% Ne. The 308 nm laser output pulse had a fwhm of 20 ns and a peak power of 8.6 MW. When charged to 35 kV, the voltage inversion reached a peak of ~45 kV and dropped to zero in ~35 ns. The fwhm of the discharge current was 46 ns, with a peak current of 15.3 kA. The electron density in the discharge was measured using an infrared Michelson interferometer, and found to have a fwhm of 30 ns and a peak value of 12±5xl0¹⁴ cm⁻³.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Jenkins, Stephen Derek. "Modification of polymer surfaces using excimer lasers." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291960.
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Hodgson, Elizabeth Mary. "Monitoring of high repetition rate excimer lasers." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334073.
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Ebrahimzadeh, Majid. "Optical parametric oscillators pumped by excimer lasers." Thesis, University of St Andrews, 1990. http://hdl.handle.net/10023/14164.
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This thesis describes the development of a new generation of pulsed optical parametric oscillators (OPO's) based on two new non-linear materials, urea and beta-BaB2O4 (or BBO), and pumped by a new class of laser pump sources, namely, excimer lasers, to provide broadly tunable coherent radiation in new regions of the electromagnetic spectrum, particularly in the ultraviolet and the visible, which have previously been inaccessible. The laser pump source used during this work was a pulsed ultraviolet XeCl excimer laser operating at 308nm. Because of the stringent demands on the pump beam quality (with regard to both spatial and spectral coherence) for successful operation of OPO's, the pump laser was designed and constructed as an injection-seeded system, to provide a narrow-linewidth, near-diffraction-limited output beam, with sufficiently high peak powers to enable OPO operation. In this way, we were able to obtain an output beam with a linewidth ≤ 0.2cm-1, and a full-angle of divergence as low as 60muR (~3 times the diffraction limit). The maximum energy available from the pump laser was 30mJ, in pulses measuring typically 10ns in duration. The output beam was also linearly polarised to better than 95%, and the pulse repetition rate was 1 Hz. In the early part of this work, we used the constructed pump laser to investigate spontaneous parametric fluorescence in a home-grown urea sample, in order to characterise the crystal, and to compare the observed spectrum with the calculated OPO tuning curves. The results of these experiments were found to be in good agreement with the theoretical predictions. The main thrust of the project, however, was the development of an OPO based on urea as the non-linear medium and pumped at 308nm by the narrowband XeCl excimer laser. We were successful in constructing such an OPO, using an 8-mm-long, home-grown crystal, and were able to generate, continuously tunable output from 572 to 667nm, with a 2.5% energy conversion efficiency. The timing range of the device was later extended to 537-720nm, by utilising a 15-mm-long, home-grown urea sample, and its conversion efficiency was improved to as high as 37% at 90° phase-matching, with ≥ 10% efficiency over a 100-nm range in the visible (from 570 to 670nm). Finally, in an effort to achieve even higher efficiencies, we performed experiments in a 25-mm-long commercial urea crystal, and demonstrated exceptionally high external energy conversion efficiencies of up to 66%, with evidence of even higher levels of pump depletion (as high as 85%) at 90° phase-matching. The latter part of the project was concerned with the design and development of a similar device based on the new non-linear material, beta-BaB2O4, to provide continuously tunable radiation over a much broader tuning range, particularly in the blue and the near ultraviolet, not accessed by the urea OPO. We used a 12-mm-long commercially available beta-BaB2O4 crystal to construct this OPO, and successfully operated this device over the entire wavelength range from 354nm in the near ultraviolet, throughout the visible, to 2.37mum in the near infrared, with an energy conversion efficiency in excess of 10% over the range 450-960 nm. The constructed OPO's were also characterised with regard to several operating parameters, including oscillation threshold, spectral linewidth, as well as spatial and temporal variation and, where appropriate, the experimental results were compared with the predictions of theory.
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Jousselin, François. "Chirurgie réfractive par laser excimer et aptitude professionnelle." Bordeaux 2, 1993. http://www.theses.fr/1993BOR2M079.
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Saidam, Sabri Mamdouh. "Fabrication and assembly of microsystems using excimer lasers." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391946.
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George, Sharon Rose. "Interaction of 157-nm excimer laser light with fused silica, polytertrafluoroethylene and calcium fluoride." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/s_george_031210.pdf.
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Lee, Wen-Chieh. "Thin film adhesion measurement using excimer laser ablation test /." Online version of thesis, 1991. http://hdl.handle.net/1850/11034.
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McDuff, Glen. "Elements of a 200 watt pulsed excimer laser." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/13926.
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This thesis describes the theoretical and experimental investigation into many aspects of circuit and component design for high average power short pulse systems. The primary objective of this work is to develop both circuit design criteria and pulsed components for long life rare gas halide lasers. A pulsed system consists of three major components, energy storage, switches, and load. This investigation considers the type of circuit which uses capacitive energy storage in combination with a closing switch to transfer electrical power to a load. Specific loads are not addressed but the implications of load characteristics that affect circuit/component design and life are considered. The investigation reported, describes the physical and electrical characteristics and analysis of phenomena that adversely affect the performance and life of pulse duty components. In the area of capacitive storage, lifetimes of one particular design was improved by 3 orders of magnitude and a means of detecting the imminent failure of oil filled capacitors was devised and patented. In the area of switching, methods are described by which hydrogen thyratrons can be operated in parallel with equal current sharing without the need for inductive or resistive ballasting. Finally, the design and testing of a 200 watt XeCl laser modulator is presented.
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Poirier, Laurent. "Le laser excimer argon fluor 193 nm en chirurgie ophtalmologique : revue de la littérature - illustrations." Bordeaux 2, 1992. http://www.theses.fr/1992BOR23063.
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Sheerin, David Thomas. "Optical scatter and damage testing of excimer laser components." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/10536.
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Wagner, Franz X. "Excimer laser ablation and processing of II-VI compound semiconductors." Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363271.
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Fairlie, S. A. "Investigations into improving the performance of discharge-pumped rare-gas-halide excimer lasers." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/13892.
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The construction and operation of a small active volume, discharge pumped, rare gas halide excimer laser is described. The values of laser output parameters such as pulse duration, pulse energy and overall efficiency presently achieved with such systems are much less that theoretical studies predict. The performance of this laser when pumped using a novel pulsed power modulator design containing nonlinear capacitors to produce a very fast rise time voltage pulse is contrasted with the performance obtained from a conventional driver circuit. The purpose of this was to determine if such circuits could lead to improvements in glow discharge stability and also laser pumping efficiency by quickly achieving the optimum pumping rates predicted by theory. It was concluded that while the rapid establishment of optimum pumping conditions may be beneficial, too fast a rate of rise of discharge current appears to be detrimental to discharge stability, probably due to skin effects. Having established that premature glow discharge collapse is a serious limiting factor in producing long duration excimer laser pulses, a study is carried out of the factors believed to influence discharge stability. While the effects of halogen donors on discharge stability have received most attention in the past the part played by the other constituents of the laser gas mix tends to have been neglected. A theoretical and experimental study of the role of the rare gas partners, xenon, krypton and argon is presented. It is well known that gas mixes using helium as the buffer gas perform less well than with a neon buffer and this is attributed to the driving of discharge instabilities rather than kinetic factors. A comparison of the relative influences of the buffer gases helium, neon and argon on discharge stability is carried out and claims by other workers for improved laser performance using a mixed helium / argon buffer are tested. Finally, in an attempt to inhibit the mechanisms driving glow discharge collapse, the effects of externally applied magnetic fields on discharge stability and laser performance are investigated.
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Mutapcic, Emir. "Optimised part programs for excimer laser-ablation micromachining directly from 3D CAD models." Australian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20061117.154651.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted to the Industrial Research Institute, Faculty of Engineering and Industrial Sciences, in fulfillment of the requirements for the degree of Doctor of Philosophy, Swinburne, ne University of Technology - 2006. Typescript. Includes bibliographical references (p. 218-229).
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Turcu, Ion Cristian Edmond. "Generation and application of x-rays from excimer laser produced plasmas." Thesis, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265966.
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Vareilles-Guétari, Marie-Claude. "Photokératectomie réfractive au laser excimer chez le myope fort : résultats à un an, à propos de 35 cas." Bordeaux 2, 1994. http://www.theses.fr/1994BOR23040.
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Mutapcic, Emir, and n/a. "Optimised part programs for excimer laser-ablation micromachining directly from 3D CAD models." Swinburne University of Technology. Faculty of Engineering and Industrial Sciences, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20061117.154651.
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Fabrication of a 3D structure and surface texture using excimer laser mask
projection ablation processes typically requires the machine operator to develop a specific
NC part program for the desired structure geometry, and also incorporate appropriate
machine parameters to achieve the desired surface finish. The capability of the laser
ablation process could therefore be significantly improved by developing a CAD/CAM
system that automatically generates the NC part program using the 3D information of the
CAD model of the desired structure. Accordingly, the focus of this research was to
develop such a system that is, an effective CAD/CAM system specifically for excimer
laser mask projection micromachining tools.
To meet these requirements, a unique combination of commercially available
systems was used to develop the new CAD/CAM system. The systems used comprised of
a computer aided, feature based parametric design system (SolidWorks), together with
its extended programming capabilities based on Automated Programming Interface (API)
functions for Windows applications, and Visual Basic (VB) 6.0 programming utilities.
The system's algorithms use a novel methodology to extract the 3D geometry of a
microstructure. Two different techniques have been developed to extract the 3D data.
First, where 3D geometry information from a CAD model was defined as a Stereolithography
(STL) file, and second, where this information has been contained in a set of
bit-map (BMP) files that represent a sliced or layered structure of a CAD model. Based
on this, first an algorithm to create NC part programs to support Step-and-repeat
micromachining technique was developed and then successfully extended to be applicable
for another commonly used micromachining method, Workpiece-Dragging technique.
The systems algorithms for both techniques are based on the raster-colour
programming technique, resulting in substantially reduced mathematical complexity and
computational time. This is the first time this approach has been used to support direct
conversion of 3D geometry from a CAD model into an NC part program compatible with
the excimer laser CNC controller. 2D mathematical models for controlling edge and
stitching errors were also implemented in the system.
An additional technique, named as 'Common Nest' has been developed with the
aim to enable automatic NC part programming when microstructure design to be
completed successfully, requires use of multiple complex mask patterns as a projection
tool instead of just a single square aperture.
The effectiveness of the system was verified by NC part program generation for
several 3D microstructures and subsequent machining trials using polycarbonate (PC) and
Polyethylene terephthalate (PET), and optimised processing parameters. Excellent
agreement was obtained between the laser machined geometries and the microstructure
CAD models. The Laser Scanning Confocal Microscope (LSCM) measured the lateral
dimensions tolerance of 2m.
The system was also successfully applied for a practical micro-engineering
application, for the development of a microfluidics cell transportation device.
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Setia, Ronald. "Modeling and Diagnosis of Excimer Laser Ablation." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7634.
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Recent advances in the miniaturization, functionality, and integration of integrated circuits and packages, such as the system-on-package (SOP) methodology, require increasing use of microvias that generates vertical signal paths in a high-density multilayer substrate. A scanning projection excimer laser system has been utilized to fabricate the microvias. In this thesis, a novel technique implementing statistical experimental design and neural networks (NNs) is used to characterize and model the excimer laser ablation process for microvia formation. Vias with diameters from 10 50 micrometer have been ablated in DuPont Kapton(r) E polyimide using an Anvik HexScan(tm) 2150 SXE pulsed excimer laser operating at 308 nm. Accurate NN models, developed from experimental data, are obtained for microvia responses, including ablated thickness, via diameter, wall angle, and resistance. Subsequent to modeling, NNs and genetic algorithms (GAs) are utilized to generate optimal process recipes for the laser tool. Such recipes can be used to produce desired microvia responses, including open vias, specific diameter, steep wall angle, and low resistance. With continuing advancement in the use of excimer laser systems in microsystems packaging has come an increasing need to offset capital equipment investment and lower equipment downtime. In this thesis, an automated in-line failure diagnosis system using NNs and Dempster-Shafer (D-S) theory is implemented. For the sake of comparison, an adaptive neuro-fuzzy approach is applied to achieve the same objective. Both the D-S theory and neuro-fuzzy logic are used to develop an automated inference system to specifically identify failures. Successful results in failure detection and diagnosis are obtained from the two approaches. The result of this investigation will benefit both engineering and management. Engineers will benefit from high yield, reliable production, and low equipment down-time. Business people, on the other hand, will benefit from cost-savings resulting from more production-worthy (i.e., lower maintenance) laser ablation equipment.
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Ghanem, Ramon Coral. "Ceractomia fotorrefrativa (PRK) com mitomicina C baseada na análise de frentes de onda corneanas para o tratamento da hipermetropia consecutiva à ceratotomia radial." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/5/5149/tde-20122010-172917/.
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OBJETIVO: Avaliar a eficácia, estabilidade, previsibilidade e segurança da ceratectomia fotorrefrativa (PRK) guiada pelas frentes de onda corneana para o tratamento da hipermetropia secundária à ceratotomia radial (CR). MÉTODOS: Foram avaliados prospectivamente 61 olhos de 39 pacientes consecutivos, submetidos a PRK personalizado com o laser Esiris-Schwind. A técnica constou de desepitelização mecânica, fotoablação, e utilização de mitomicina C (MMC) 0,02% por 20 ou 40 segundos. A MMC foi aplicada por 40 segundos em 17 olhos (27,9%) que haviam sido submetidos a ablações mais profundas do que 100 ?m ou apresentavam córneas previamente suturadas. As avaliações pós-operatórias foram realizadas após sete dias, um, seis, 12 e 24 meses. Todos os olhos foram avaliados após um ano e dois anos. RESULTADOS: O intervalo médio entre a CR e o PRK foi de 18,8 anos ± 3,8 (DP); o equivalente esférico (EE) médio antes da ceratotomia radial era -4,10 dioptrias (D) ± 1,44. As medidas prévias ao PRK mostraram EE médio de +4,17 D ± 1,97; astigmatismo médio de -1,39 D ± 1,04; AV com correção (AVcc) média de 0,161 ± 0,137 (logMAR); e curvatura corneana média de 35,85 ± 3,60 D. Os resultados encontrados dois anos após a cirurgia foram: EE médio de 0,14 ± 0,99 D (p < 0,001); astigmatismo médio de -1,19 ± 1,02 D (p = 0,627); AV sem correção (AVsc) média de 0,265 ± 0,196 (p < 0,001); AVcc média de 0,072 ± 0,094 (p < 0,001); e curvatura corneana média de 39,01 ± 3,18 D (p < 0,001). AVsc igual ou melhor a 20/25 foi observada em 38% dos olhos e igual ou melhor a 20/40 em 69%. A AVcc melhorou em 62,3% dos olhos, sendo que 21 olhos (34,4%) melhoraram uma linha e outros 17 olhos (27,9%), duas ou mais linhas. Um olho (1,6%) perdeu duas linhas devido ao astigmatismo irregular ocasionado por opacificação corneana periférica. Outro olho perdeu três linhas pelo desenvolvimento de ectasia corneana entre seis e 24 meses, devido ao alargamento progressivo de uma incisão radial inferior, e foi posteriormente submetido à sutura da incisão. Houve 30 olhos (49,2%) entre ± 0,50 D do EE planejado e 45 (73,8%) entre ± 1,00 D. Entre seis e 24 meses, a regressão média do EE foi de +0,39 D (p < 0,05) e cinco olhos (8,3%) sofreram desvio hipermetrópico > 1,00 D. Ocorreu redução estatisticamente significante do coma (p = 0,001), trefoil (p = 0,008), aberração esférica (p < 0,001), astigmatismo secundário (p = 0,001) e quatrefoil (p < 0,001). Não houve mudança estatisticamente significativa da contagem endotelial (p = 0,161). Dois olhos (3,3%) desenvolveram opacificação corneana periférica grau 2 e um, grau 3. CONCLUSÃO: O PRK personalizado pelas frentes de onda corneana coadjuvado pela MMC foi eficaz, previsível e seguro pelo período de dois anos para a redução da hipermetropia após a CR. No pós-operatório observou-se melhora significativa da AVsc, AVcc e das aberrações corneanas. Constatou-se, entretanto, que a hipermetropia consecutiva à CR continua a progredir após o tratamento com o excimer laser.PURPOSE: To assess the efficacy, stability, predictability and safety of corneal wavefront-guided photorefractive keratectomy (PRK) for correcting hyperopia after radial keratotomy (RK). METHODS: In a prospective study, 61 eyes of 39 consecutive patients were treated with PRK using an Esiris-Schwind excimer laser. Corneal epithelium was mechanically removed, followed by photoablation and use of 0.02% mitomycin C (MMC) for 20 or 40 seconds. MMC was used for 40 seconds in 18 eyes (27.9%) which underwent ablations deeper than 100 micron or had previous corneal sutures. Postoperative evaluations were performed after seven days, six, 12 and 24 months. All patients were followed up for two years. RESULTS: The mean time between RK and PRK was 18.8 years ± 3.8 (SD); mean spherical equivalent (SE) before RK was -4.10 diopters (D) ± 1.44. Before PRK, the mean SE was +4.17 D ± 1.97, mean astigmatism was -1.39 D ± 1.04, the mean best-corrected visual acuity (BCVA) was 0.161 ± 0.137 (logMAR) and the mean corneal curvature was 35.85 ± 3.60 D. At 24 months, mean SE was 0.14 ± 0.99 D (p < 0.001), mean astigmatism was -1.19 ± 1.02 D (p = 0.627), mean UCVA was 0.265 ± 0.196 (p < 0.001), mean BSCVA was 0.072 ± 0.094 (p < 0.001) and the mean corneal curvature was 39.01 ± 3.18 D (p < 0.001). UCVA was 20/25 or better in 38% of eyes and 20/40 or better in 69%. BCVA improved in 62.3% of eyes, with 21 (34.4%) gaining one line and 17 (27.9%), two or more lines. One eye (1.6%) lost two lines due to irregular astigmatism and peripheral haze. Another eye lost three lines due to keratectasia occurring between six and 24 months resulting from widening of an inferior radial incision that was later sutured. Thirty eyes (49.2%) were within ± 0.50 D of intended SE and 45 (73.8%) were within ± 1.00 D. From six to 24 months, the mean SE regression was +0.39 D (p < 0.05) and five eyes (8.3%) had a hyperopic shift > 1.00 D. A significant decrease in coma (p = 0.001), trefoil (p = 0.008), spherical aberration (p < 0.001), secondary astigmatism (p = 0.001) and quatrefoil (p < 0.001) was observed. Endothelial cell counts did not show a statistically significant decrease (p = 0.161). Two eyes (3.3%) developed peripheral haze grade 2 and one, grade 3. CONCLUSION: Corneal wavefront-guided PRK with MMC was effective, predictable and safe after two years for the treatment of hyperopia after RK. A significant improvement in UCVA, BSCVA and corneal aberrations was obtained. However, hyperopic shift after RK continued to progress after excimer laser surgery.
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Giedl, Roswitha. "Grating formation on polymer films and in optical fibres using excimer laser irradiated phase masks." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322329.
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Fieret, Jim. "Design and operation of a compact gas flow system for a high power excimer laser." Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337242.
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Pereira, Vinícius Borges Porfírio. "Dor no pós-operatório da ceratectomia fotorrefrativa (PRK) com fosfato de codeína 30 mg/ paracetamol 500 mg: ensaio clínico aleatório." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/5/5149/tde-08052018-112512/.
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Introdução: A ceratectornia fotorrefrativa (PRK) é uma das técnicas de cirurgia refrativa mais empregadas no mundo. A despeito de sua efetividade e segurança no tratamento de miopia, hipermetropia e astigmatismo, a dor permanece ainda como um dos grandes desafios no período pós-operatório da PRK. Embora a associação dos fármacos codeína (opióide oral) e paracetamol (analgésico) seja amplamente empregada no período pós-cirúrgico de várias especialidades médicas. a eficácia e segurança dessa associação não foi avaliada no manejo da dor no pós-PRK. Objetivo: O objetivo da presente tese foi testar a combinação codeína + paracetamol no manejo da dor pós-PRK. Métodos: Trata-se de um ensaio clínico controlado por placebo, randomizado, paralelo e duplo-cego. O subdelineamento é do tipo \"add-on \", isto é. o grupo da intervenção recebeu a terapia padrão + a intervenção. enquanto o grupo controle recebeu a terapia padrão + placebo. A amostra foi composta por 41 participantes (82 olhos) - por meio do delineamento \"olhos pareados\" (paired-eye design), ou seja, o olho foi a unidade de análise. As cirurgias foram realizadas com duas semanas de intervalo. Um olho recebeu codeína (30 mg) + paracetamol (500 mg) 4x1dia por quatro dias (período A), enquanto o outro olho recebeu placebo 4x/dia por quatro dias (período B). Tanto a alocação (intervenção ou placebo) quanto a ordem (A-B ou B-A) foram aleatorizadas. A dor foi avaliada por meio de três escalas: questionário de dor McGill (MPQ). Inventário Resumido da Dor (I3PI) e escala visual análoga (EVA) nos períodos I, 24, 48 e 72 horas após a cirurgia. O período de seguimento total foi de quatro meses. Resultados: A idade média dos pacientes foi de 30 anos (rnin-máx: 22-52), dos quais 67% foram mulheres. Dos 82 olhos inicialmente arrolados no estudo, 80 completaram os quatro meses de seguimento (40 na intervenção e 40 no placebo). Os escores medianos de dor mensurados pela EVA foram significativamente mais baixos no grupo da intervenção comparado com o grupo placebo - durante todo o período do pós- cirúrgico imediato (1-48 horas). Os eventos adversos foram brandos e de fácil manejo clínico; os mais comuns foram sonolência, náusea e constipação. Após um seguimento de quatro meses, não foi observado nenhum retardo na resposta de cicatrização da córnea ou haze. Conclusões: A combinação de codeína (30mg) e paracetamol (500mg) via oral (4x/dia) é segura e significativamente superior ao placebo para o controle da dor após a PRKIntroduction: Photorefractive keratectomy (PRK) is one of most widely performed types of refractive surgery in the world. In spite of its effectiveness and safety for the treatment of myopia, hypermetropia and astigmatism, pain remains one of the biggest clinical challenges during the early postoperative period after PRK. Although the combination of codeine (an oral opioid) plus acetaminophcn (an analgesic) has been widely used during the postoperative period in many medical specialties, both its efficacy and safety have not been formally investigated for pain control after PRK. Objective: To carry out a randomized, controlled c1inical trial, specifically dcsigned to test whether the combination of codeine + acetaminophen is efficacious and safe for pain control after PRK. Methods: Double-blind (patients and outcome assessors), randomized, parallel, placebo-controlled trial. An add-on design was adopted. tl.at is, the intervention group received the standard of care therapy + codeine/acetaminophen, whereas the control group received the standard o[ care therapy + placebo. The sample encompassed 41 participants (82 eyes) through the \"paired-eye design\". In other words, the eye was the unity of analysis. Surgeries were performed two weeks ap311. One eye received codeine (30mg) + acetaminophen (500mg) 4x/day for four days (period A), whereas the fellow (control) eye received placebo 4x/day for four days (period B). Both treatrnents (intervention or placebo) and treatment order (A-B or B-A) were randomly chosen. Pain was asscsscd at 1, 24, 48 and 72h postopcrativcly by three scales: visual analogue scale (VAS), McGill Pain Questionnaire (MQP) and Brief Pain Inventory (BPI). The total follow-up period was 4 months. Results: The mean age of patients was 30 years (rnin-max: 22-52) and 67% (27/40) were female. Ofthe initial 82 eyes, 80 completed the trial (40 in the intervention 31m, 40 in the placebo arm). Median pain scores as measured by the VAS were significantly lower during treatment with codeine/acetaminophen compared to the placebo throughout the early postoperative period (1-48h). Virtually identical results were obtained by the MQP and BPI scales, suggesting that the intervention can have a positive impact not only on the pain intensity, but also on the multidimensional aspects of pain, such as interference on activities of daily living as well as emotional status. Adverse events (AEs) were usually mild and easily managed. The most common AEs were drowsiness, nausea and constipation. After a follow- up period of four months, no case of delayed epithelial healing or haze was observed in both treatment arms. Conclusions: When added to the standard of care therapy, the oral combination of codeine (30mg) and acetaminophen (500mg) given 4x/day was safe and significantly superior to placebo for pain control after PRK
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Theodorakopoulos, Charalampos. "The excimer laser ablation of picture varnishes : an evaluation with reference to light-induced deterioration." Thesis, Royal College of Art, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602333.
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Gery, Guillaume. "Procédés d'implantation moléculaire laser : implantation et réactivité de fluorophores dans des poly(méthacrylates) d'alkyles par irradiation laser à excimère XeF." Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL062N.
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L’implantation moléculaire tire son origine de l'ablation par irradiation laser de films polymères dopés par une molécule photosensible. Le dispositif expérimental fait intervenir deux films polymères superposés en contact direct irradiés par une impulsion laser à excimère (XeF). Le film source est un film dopé en molécules photosensibles tandis que le film d'implantation peut être non dopé ou dopé avec une molécule susceptible de réagir avec la molécule dopante du film source, mais transparente à la longueur d'onde du faisceau laser. Les molécules du film source sont excitées, convertissent l'énergie du faisceau laser en énergie calorifique puis sont implantées dans le film en contact. L'étude a porté sur l'implantation d'anthracène et de dicyanoanthracène dans des films de poly(méthacrylates d'alkyles) de différentes températures de transition vitreuse. L’analyse de la quantité de molécules implantées en fonction de la température du film source suit une loi d'Arrhenius et indique l'origine diffusionnelle du processus d'implantation (activation thermique). Un modèle, prenant en compte le coefficient de diffusion et l'énergie d'activation de diffusion de l'anthracène dans le polymère, est en bon accord avec les résultats expérimentaux. L’implantation moléculaire est ensuite appliquée à la formation d'un complexe par transfert de charge dans une matrice polymère. L’anthracène et le tetracyanobenzène ne représentent pas un bon couple de complexassions, du a un rendement quantique de fluorescence du complexe très faible (gênant sa détection par spectrofluorimétrie). En revanche, le couple dicyanoanthracène/hexamethylbenzène a permis de mettre en évidence la complexation des deux constituants dans la matrice, ce qui permet de dégager des perspectives originales pour la chimie dans les polymères puisque l'implantation moléculaire permet des réactions dans un volume parfaitement défini d'un film polymère solide sans l'utilisation de solvant.
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Honoré, David. "Fluorescence induite par laser à excimères bande-fine. Application à la caractérisation de souffleries à haute enthalpie." Rouen, 1995. http://www.theses.fr/1995ROUES051.
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Le travail présenté dans ce mémoire concerne le développement de la technique de mesure de fluorescence induite par laser (LIF) à excimères fluorure d'argon bande-fine, et son utilisation pour l'étude expérimentale de jets supersoniques de plasma au voisinage de maquettes immergées dans l'écoulement, simulant les conditions de réentrée atmosphérique d'un engin spatial. Les différents schémas de fluorescence des molécules monoxyde d'azote et monoxyde de carbone sont discutés. La température du milieu est déduite de la comparaison des spectres d'excitation expérimentaux de la bande epsilon de NO avec les spectres synthétiques obtenus à l'aide d'un code de calcul. La vitesse de l'écoulement est déterminée par mesure du décalage Doppler. Cette technique de mesure est appliquée à un jet de plasma dioxyde de carbone-azote, généré dans une soufflerie de laboratoire, simulant l'atmosphère de Mars, et à la couche limite au-dessus d'une tuile de C/SIC. De manière complémentaire, la température pariétale des échantillons est mesurée par thermographie infrarouge. L'instrumentation de deux souffleries à haute enthalpie de l'institut Tsniimash (Moscou) a permis de démontrer les potentialités offertes par l'implantation sur site industriel de la technique de mesure LIF. La première étude concerne la couche limite générée au voisinage d'un modèle SIC immergé dans un jet supersonique de plasma d'air (Mach 2,5), créé par une torche haute fréquence (100 kW), et a permis de mettre en évidence l'effet catalytique de la surface du matériau de protection thermique pour différents processus cinétiques de recombinaison atomique. Dans la soufflerie à arc TT1 (4 MW, Mach 5), les expériences sont menées dans le jet libre et au voisinage d'une plaque plane comportant une marche, pour simuler un désalignement de tuiles à la surface d'un avion spatial. L'ensemble des mesures constitue un cas test pour la validation de codes de calcul d'écoulements supersoniques.
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Gévaudan, Alain. "Modélisation d'un laser à exciplexe XeCL à décharge par avalanche préionisée par faisceau de rayons X." Aix-Marseille 2, 1986. http://www.theses.fr/1986AIX22052.
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Laser xecl a decharge par avalanche preionisee par faisceau de rayons x, utilisant un circuit de decharge a condensateur de transfert ou a ligne de transmission. Les phenomenes electroniques presents au tout debut de l'avalanche de la decharge preionisee du laser sont etudies dans le but d'etablir les conditions necessaires a la formation homogene d'une decharge dans un grand volume. L'etude parametrique de l'optimisation du depot d'energie dans le milieu est effectuee a l'aide d'une modelisation des circuits de decharge. Le modele complet de laser xecl est ensuite etabli, permettant de simuler le modele experimental
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Lott, Joseph Robert. "Design, Synthesis and Incorporation of Functional Additives into Multilayered Polymer Films." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1295673932.
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Fariaut, François. "Traitement de surface par laser excimère." Orléans, 2002. http://www.theses.fr/2002ORLE2049.
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Les alliages légers d'aluminium ont un fort potentiel dans l'industrie automobile, mais leur mauvais comportement en usure et frottement les rend peu attractifs. Une solution pour améliorer ce comportement est d'effectuer une carburation de l'alliage en surface par traitement laser. Pour ce traitement, le faisceau d'un laser excimère KrF (??= 248 nm, ??= 25 ns) homogénéisé est focalisé sur la surface à traiter. L'échantillon est placé dans une enceinte à vide remplie d'un gaz carboné (CH4, C3H6) à une pression de 1 bar. L'interaction du faisceau laser avec la surface produit un plasma qui permet la dissociation du gaz en contact avec la surface, les espèces ainsi formées pénètrent dans le matériau et forment une couche de carbure d'aluminium Al4C3 sur 2 à 3 æm d'épaisseur. Cette étude présente les différents diagnostiques du plasma par imagerie et par spectroscopie d'émission. Des profils de concentration du carbone ont été mesurés par analyses nucléaires. Des analyses des structures et des phases cristallines ont été réalisées par diffraction de rayons X en incidence rasante, et par microscopie électronique en transmission et en balayage. Des tests de tribologie ont permis de montrer une amélioration des propriétés mécaniques des surfaces traitées. Les différentes techniques d'analyses employées au cours de cette étude nous ont amené à mieux comprendre les phénomènes de formation de la couche carburée et les différents mécanismes qui entrent en jeu lors du procédé. Ainsi nous avons pu proposer un modèle de formation de cette couche via un phénomène de transport du carbone par convection micro-thermocapillaire.
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Apte, Paul. "Laser beam characterisation for industrial applications." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/33964.
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This thesis describes the theory, development and applications of laser beam characterisation for industrial laser materials processing systems. Descriptions are given of novel forms of beam diagnostic systems and their integration into highly automated industrial tools. Work is also presented that has contributed to the new ISO standard on beam characterisation. Particular emphasis is given to excimer laser applications and UV micromachining.
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Utzinger, Urs. "Selektive koronare Excimer Laser Angioplastie /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11131.
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Hassan, R. M. R. "Studies of excimer laser systems." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637242.
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Anderson, Jason. "Aspects of excimer laser technology." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308090.
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Wrobel, René. "Étude de la transmission d'impulsions lumineuses délivrées par un laser à XeC1 dans des fibres optiques à usage médical : Utilisation de ce laser à la fragmentation et à l'identification in-vitro de calculs biliaires." Lille 1, 1990. http://www.theses.fr/1990LIL10082.
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La lithotripsie laser des calculs biliaires constitue une application potentielle des lasers à excimer. Dans ce mémoire, nous étudions différents problèmes physiques posés par l'utilisation de cette technique. Dans le premier chapitre, nous nous livrons tout d'abord à une réflexion d'ordre théorique afin de fixer l'ordre de grandeur des différents phénomènes susceptibles de modifier les caractéristiques des impulsions ultraviolettes au cours de leur transmission dans des fibres optiques à usage médical. Nous décrivons ensuite les expériences que nous avons réalisées afin d'estimer les valeurs numériques des paramètres de la transmission dans trois types de fibres disponibles commercialement. Nous avons, en particulier, mesuré les seuils de fracture optique de ces fibres et mis en évidence des effets de photochromisme de fibre induits par leur irradiation prolongée au flux laser. Dans le deuxième chapitre, nous examinons la faisabilité de destruction de calculs biliaires par des impulsions ultraviolettres (xecl). Nous déterminons les densités d'énergie correspondant au seuil d'ablation, et mesurons l'efficacité de cette ablation en fonction de la densité d'énergie. Nous analysons la composition chimique des gaz produits lors de la destruction des calculs par spectroscopie d'absorption infrarouge et évaluons ainsi leur risque de toxicité. Dans le troisième chapitre, nous présentons une méthode originale d'identification de la nature chimique des calculs biliaires (cholestérolique ou pigmentée). Cette méthode repose sur l'analyse multicanale des spectres de fluorescence émis par les calculs lorsqu'ils sont irradiés par des impulsions laser de faible fluence
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Key, Philip Henry. "Excimer laser micromachining of inorganic materials." Thesis, University of Hull, 1989. http://hydra.hull.ac.uk/resources/hull:11090.
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Osborne, M. R. "An X-ray preionised excimer laser." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37810.
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Mudugamuwa, Nilushan Kulunu. "Excimer laser crystallised polysilicon solar cells." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/844231/.
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Crystalline silicon (c-Si) has been the main material for solar cells as a renewable energy source. The main advantage has been the abundance of this material. However, due to the high costs, thin film alternatives to c-Si in the form of hydrogenated amorphous silicon (a- Si:H) has shown promising progress. The popularity of a-Si:H increased due to the lower pay back times although initial efficiencies were lower for a-Si:H. Higher efficiency of c-Si is primarily due to the absorption of broader spectrum of radiation from the sun compared to a-Si:H. Although cheaper to produce, a-Si:H suffers from light induced degradation resulting in lower efficiencies. Thinner absorber layers of a-Si:H have shown better stability in this regard. In this thesis, attempts were made to fabricate a-Si:H/c-Si hybrid solar cell structures by the use of a laser crystallisation process using excimer laser. An excimer laser, KrF 248nm, was used to crystallise a-Si:H as excimer laser readily absorb into a-Si:H within a few tens of nanometres enabling melting and solidification creating c-Si. An a-Si;H p/i structure deposited on textured ITO is crystallised in partial melting regime and is used to make solar cells. Initially, a suitable metal for back contact was investigated. Al was selected as the preferred back contact compared to Au due to the better efficiencies observed. Further, different methods were attempted to obtain an n-layer to complete a-Si:H p-i-n solar cell. Devices were fabricated for different intrinsic layer thicknesses using ion implanted phosphorus and diffused phosphorus as dopants in the n+-layer. Ion implanted phosphorus devices showed poor efficiencies due to implantation damage even after laser annealing. Phosphorus diffused and thermal annealed devices showed lower efficiencies than the reference devices, where dopant profile showed possible activation of dopants. Excimer laser was utilised to obtain a crystallised structure in two different ways as single shot and multiple shot. Both methods resulted in poor device performances with increasing laser energy density. However, reversible increment of current density was observed for these devices due to the creation of high band gap silicon nanocrystals. Finally, broadband absorbing hybrid devices were fabricated by incorporating PbS nanocrytals/BCP with a-Si:H and laser crystallised silicon. Although these devices show small contributions in the IR region compared to a-Si:H only cells, the overall device efficiencies were observed to be very low.
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Gartry, David Stanley. "The development of excimer laser corneal surgery." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244678.
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Clark, Stuart E. "Excimer-laser-induced modifications of optical surfaces." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/33023.
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The work in this thesis is a study of the interactions of a well characterized high power ultra violet excimer laser beam with solid optical quality surfaces, principally Al and Ge but with limited work on dielectrics. In order to characterize the beam and to monitor the changes induced on test surfaces by the beam, a computer controlled image processing system was developed. The system used the fluorescence from a UV absorbing glass to image the excimer beam and Schlieren imaging of the test surfaces with cw HeNe or pulsed dye laser illumination to monitor the induced changes.
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Chang, I.-Ta. "Excimer Laser Ablation of Polymer-Clay Nanocomposites." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333995807.
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MSELLATI, ANDRE. "Photokeratectomie refractive au laser excimer : etude clinique." Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX20718.
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Chisholm, Catharine Mary. "Assessment of visual performance : comparison of normal subjects and post-refractive surgery patients." Thesis, City University London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270600.
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Pearson, Guy Neville. "RF excited carbon monoxide lasers." Thesis, Heriot-Watt University, 1988. http://hdl.handle.net/10399/981.
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Richmond, A. M. "Vacuum ultraviolet discharge excited lasers." Thesis, University of Oxford, 1987. http://ora.ox.ac.uk/objects/uuid:3a09736b-bffb-4ac9-b57c-fb9daa1c8484.
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The thesis concerns experimental studies of discharge excited lasers operating in the vacuum ultraviolet (VUV) region of the spectrum. The known molecular fluorine laser operating at 157nm, on a bound- to-bound transition of the F2 molecule was selected for initial study. As a result of the work reported here the energy per pulse was increased by a factor of five (10mJ to 50mJ) from that of earlier F2 lasers. Similary the working lifetime of the gas mixture was increased from a few shots to several thousand by the application of cryogenic gas purification techniques. These improvements have resulted in the development of a practical commercial F2 laser. The performance characteristics of the fluorine laser and their relationship to the physical mechanisms are discussed. With the objective of achieving laser action in the 110 to 130nm region of the VUV a novel scheme is investigated. The scheme involves the production of a population inversion between the v'=1 level of the b1πu state of molecular nitrogen and high lying levels of the X1Σg ground state. The excitation of the upper laser level involves production of N2 molecules in the a1πg state by means of a pulsed discharge. Transfer of population from this intermediate 'a' state to the upper level is accomplished by absorption of radiation at 308nm from a discharge excited xenon chloride laser. The practicality of this scheme has been investigated to the extent that populations of the order of 1013 molecules per cm3 have been produced in the 'a' state and laser induced fluorescence on the 'b' to 'X' band has been observed. Under the conditions of "the present experiments the potential VUV gain is too small (10-4cm-1>/sup>) to reach laser threshold. The problems of increasing the gain to reach threshold for a practical device are discussed.
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Monflier, Richard. "Etude des défauts induits par recuit laser excimère dans le silicium." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30067.
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La micro-électronique est un domaine exigeant, en constante évolution, motivé par le secteur applicatif et les besoins des utilisateurs. La réalisation de jonctions ultra-minces et fortement dopées est un enjeu majeur pour la poursuite de son évolution, et notamment pour son composant de base, le transistor MOS. Dans ce contexte, de nouvelles techniques de dopage permettant d'obtenir des jonctions ultra-minces ont été développées. Le recuit par laser nanoseconde (LTA) en mode " melt " est une de ces techniques. En effet, il permet une très forte activation locale (en surface et en profondeur) et une distribution uniforme des dopants. Ce procédé utilisé en laboratoire depuis les années 1980 dans la fabrication des cellules solaires offre également de nouvelles possibilités technologiques comme le développement d'architectures 3D. Néanmoins, des dégradations électriques de paramètres sensibles aux défauts tels que la mobilité et le courant inverse d'un transistor MOS ou la durée de vie des porteurs dans le cas de cellule photovoltaïque ont été observées. Dans ce contexte, cette thèse propose une étude rigoureuse des défauts générés par recuit laser en deux volets. Le premier volet traite de l'impact du recuit laser sur les propriétés physiques du silicium et repose essentiellement sur des caractérisations approfondies par spectroscopie infrarouge et photoluminescence d'échantillons silicium non intentionnellement dopés soumis à diverses conditions de recuits par impulsions laser à excimère. L'étude met en évidence la formation de défauts suite au procédé de recuit laser. Leur identification a permis d'affirmer l'introduction d'impuretés d'oxygène et de carbone durant le recuit. A partir de cette identification, le suivi en profondeur par spectroscopie de masse à ionisation secondaire de chacune des impuretés a été effectué révélant une augmentation de la concentration et de la diffusion des impuretés avec l'augmentation de la densité d'énergie du laser et/ou du nombre de tirs. A haute énergie laser, les profils de concentration d'oxygène montrent la présence d'un pic immobile (en concordance avec la solubilité limite de l'oxygène dans le silicium liquide) associé à des cavités de silicium observées par microscopie électronique en transmission (MET). L'origine de ces impuretés est discutée ; la caractérisation de véhicules tests dédiés a permis de définir l'oxyde natif comme étant leurs sources. Le second volet permet de répondre au second objectif qui consiste à évaluer l'impact du recuit laser sur les propriétés électriques de composants à base de silicium et s'appuie sur la caractérisation de diodes Schottky et PN préalablement fabriquées. Les résultats obtenus constituent un moyen supplémentaire pour, non seulement localiser les défauts électriquement actifs, mais également les identifier. Les caractéristiques courant-tension des diodes montrent systématiquement l'impact du recuit sur le courant de fuite, paramètre sensible aux défauts. Plus spécifiquement, le courant de fuite se dégrade avec l'augmentation de la densité d'énergie. Ces mesures électriques ont permis également de mettre en évidence la présence de défauts localisés à l'interface liquide/solide, défauts ayant un fort impact sur les propriétés électriques des diodes. Les résultats sont en accord avec la littérature qui suggère la présence de lacunes à cette interface. Pour aller plus loin, des mesures de DLTS ont été effectuées et dévoilent, selon la localisation (zone fondue ou interface), des signatures singulières laissant présager plusieurs types de défautsThe micro-electronic domain is constantly evolving in response to the continuous emerging of new application fields as well as new users' needs. The fabrication of heavily-doped regions for ultra-shallow junctions is a major issue to ensure its evolution. In this context, new doping techniques allowing to obtain ultra-shallow junctions have been developed. Nanosecond laser annealing in "melt mode" is one of these techniques. Indeed, it allows a very strong local activation (on surface and in depth) and a uniform distribution of doping. This process used in laboratory since the 1980s for the realization of solar cells offers also new technological possibilities such as the development of 3D architectures. However, degradation of several parameters sensitive to laser-induced defects were observed, such as carrier mobility and reverse current in MOS transistors or carrier lifetime in the case of photovoltaic cells. In this context, this thesis proposes a rigorous study of the defects generated by laser annealing in two parts. The first part analyses the impact of the laser annealing on the physical properties, thanks to infrared and photoluminescence spectroscopy characterizations of bare silicon samples submitted to different annealing conditions. The study highlights the formation of defects following the laser process. Their identification allowed to confirm the introduction of oxygen and carbon impurities during the annealing. From this identification, the impurities were followed in depth by secondary ion mass spectrometry allowing to reveal an increase of their concentration and diffusivity when increasing the laser energy density and/or the number of laser pulses. At high energy, the oxygen concentration profiles show the presence of an immobile peak (in agreement with the known solubility limit value in liquid silicon) which are related to silicon cavities observed by transmission electron microscopy. The origin of these impurities is also discussed and the characterization of dedicated test vehicles allowed to identify the native oxide as the source of the impurities. The objective of second part is to evaluate the impact of laser annealing on the electrical properties of silicon devices thanks to the characterization of PN and Schottky diodes. The obtained results provide an additional mean to localize the electrically active defects but also to identify them. The current-voltage characteristics of diodes systematically show an impact of the annealing on the leakage current, which is a strongly defect-sensitive parameter. More specifically, the leakage current deteriorates with increasing the laser energy. These measurements have allowed also to highlight the presence of defects at the liquid/solid interface, defects which also have a strong impact on diodes electric properties. The results are in agreement with the literature which suggests the presence of vacancies at the interface. To go further on this study, DLTS measurements have been carried out and reveal, depending on their localization (melt zone or liquid/solid interface), singular signatures suggesting several types of defects
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Al-Dhahir, Rashid K. "Development and interaction of excimer laser with tissue." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279810.
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Newsome, Christopher James. "Liquid crystal alignment on excimer laser irradiated polyimide." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310307.
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