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1
Yablon, Andrew D. 1970. "Photothermal effects of pulsed laser irradiation of biological tissue." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10244.
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Dobson, Helen Louise. "The interaction of pulsed Nd:YAG laser irradiation with human enamel." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/4312/.
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The aim of the work presented in this thesis was to investigate the interaction of pulsed Nd:YAG laser irradiation with both sound and artificially carious human enamel. More specifically, the aims were to characterise the effect of Nd:YAG laser irradiation on artificially created white spot enamel lesions (to simulate the effect of lasing carious enamel); to quantify the effects of pulsed Nd:YAG laser irradiation on enamel demineralisation; to investigate whether there is synergy between the action of pulsed Nd:YAG laser irradiation and fluoride in terms of impairing acid resistance to enamel; and finally to clarify the mechanism by which pulsed Nd:YAG laser irradiation physically interacts with enamel to induce acid resistance. Laser irradiation of artificial white spot lesions, at 50 mJ and 100 mJ (10 pps, 2 or 5 sec), was found to ablate tissue, causing crater formation. Ablation depth, as determined by microdensitometry, was correlated only with the power used, being greater at 100 mJ than at 50 mJ. SEM examination of the surface morphology of lased enamel, and the surrounding unlased area, was consistent with a process of melting and recrystallisation. It is evident, from this investigation, that in order to remove carious enamel selectively, while leaving sound enamel intact, successive applications of low power irradiation (50 mJ) are the most suitable. The work presented in this thesis has indicated the versatility of the Nd:YAG laser as a dental instrument. The laser can be used to ablate carious enamel and has potential as a prophylactic treatment for caries. The most significant aspect of the laser as a strategy to prevent caries, is that it seems to physically alter the structure of enamel so may, therefore, be a method of permanently increasing tooth resistance to decay.
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Venugopalan, Vasan. "The thermodynamic response of polymers and biological tissues to pulsed laser irradiation." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12021.
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Dark, Marta Lyselle 1970. "The physical response of soft musculoskeletal tissues to short pulsed laser irradiation." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9538.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1999.Includes bibliographical references (leaves 128-132).
An experimental study was performed to determine the physical properties of knee meniscus using a low energy laser technique. Following irradiation by a 10 ns laser pulse, tissue undergoes thermoelastic expansion in response to laser-induced stresses. The stresses evolve, propagating through the tissue. If they exceed the material's strength, ablation occurs-the material ruptures. Below ablation threshold, the material remains in an expanded state until thermal relaxation occurs. We use numerical methods to solve the 3-D thermoelastic wave equation for a hydrated sample. In addition to thermoelastic expansion, expansion due to the formation of cavitation bubbles within the tissue was modeled. Cavitation occurs when tensile stresses rupture fluid. The laser-induced response of a gelatin phantom was measured with a Michelson interferometer and compared with predictions. Using gelatin as a tissue model provided a consistent experimental model of meniscus. Meniscus, like all biological tissue, is highly heterogeneous. By adapting the time dependent numerical solution of the wave equation, the measurement of physical properties of a hydrated sample became possible. The thermoelastic model depends on sound speed, Poisson's ratio, thermal expansion coefficient, and optical penetration depth. Once the behavior of gelatin was understood, human knee meniscus was studied. The thermoelastic model and experiment, allows measurement of physical properties of meniscus. Also, a numerical model of cavitation based on Rayleigh's equations was developed. By comparing experiment and theory in meniscus and water, we determined properties important to cavitation: threshold pressure, bubble density, surface tension and nucleation size. Finally, histology was compared with experiment. The presence and amount of cavitation displacement was correlated with the condition of meniscus. Physical properties can be used to diagnose degenerative cartilage. This research has increased understanding of the interaction of short laser pulses with cartilage tissue, and measured significant physical properties of knee meniscus with a minimally invasive laser technique.
by Marta Lyselle Dark.
Ph.D.
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Mohanan, Senthilnathan. "Tailoring the magnetic anisotropy of thin films utilizing large persistent stress and pulsed laser irradiation." [S.l. : s.n.], 2009. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-66577.
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Mabakachaba, Boitumelo Mafalo. "Carbon, magnesium implantation and proton irradiation on pulsed laser deposited thermochromic thin film of VO2." University of Western Cape, 2020. http://hdl.handle.net/11394/7723.
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>Magister Scientiae - MScWhen the spacecrafts orbit in space, it is subjected to significant thermal cycling variation. Thermal regulation of the spacecraft temperature is required to ensure a good operation of the small crafts such as CubeSats and the on-board equipment while minimizing the weight. Three methods employed for the Smart Radiator Devices (SRD) are (i) mechanical louvers, (ii) electrochromic coatings and (iii) thermochromic coatings (which is of interest in this study). Based on the characteristics of the thermochromic coatings, the passive smart radiator device is by far the most efficient option since there are no mechanical moving components and also no electric energy needed for the craft to operate.
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Itapu, Srikanth. "Microstructuring of Nickel Thin Films and Property Modification of Nickel Oxide Films by Pulsed Laser Irradiation." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501701523725736.
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Tadadjeu, Sokeng Ifriky. "Sub-10 MeV proton irradiation effects on a coating obtained from the pulsed laser ablation of W2B5/B4C for space applications." Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/2181.
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Thesis submitted in partial fulfilment of the requirements for the degree
Doctor of Technology: Electrical, Electronic and Computer Engineering
in the Faculty of Engineering at the Cape Peninsula University of TechnologyThis research investigates the effects of sub-10 MeV protons on coatings obtained from the pulsed laser ablation of W2B5/B4C. This is in an attempt to extend the bullet proof applications of W2B5/B4C to space radiation shielding applications, offering low cost and low mass protection against radiation including X-rays, neutrons, gamma rays and protons in low Earth orbit. The focus in this research, however, is on low energy protons. The associated problems addressed in this work are solar cell degradation and Single Event Upsets in high density semiconductor devices caused by low energy protons. The relevant constraints considered are the necessity for low cost, low mass and high efficiency solutions. The work starts with a literature review of the space environment, the interaction of radiation with matter, and on pulsed laser deposition as a technique of choice for the coating synthesis. This paves the way for the pulsed laser ablation of W2B5/B4C. The resulting coating is a solid solution of the form WC1-xBx which contains crystalline and amorphous forms. Two proton irradiation experiments are carried out on this coating, and the resulting effects are analysed. The effects of 900 keV proton irradiation were the melting and subsequent growing of nanorods on the surface of the coating, the lateral transfer of the proton energy across the coating surface, and the lateral displacement of matter along the coating surface. These effects show that the coating is a promising cost effective and low mass radiation shield against low energy protons. The effects of 1 MeV protons on this coating are the three-stage melting of rods formed on the coating surface, and further evidence of lateral transfer of energy across the coating surface. Optical measurements of this coating show that it is about 73% transparent in the Ultraviolet, Visible and near Infrared range. This allows it to be used as radiation shielding for solar cells, in addition to high density semiconductor devices, against low energy protons in low Earth orbit. Simulations show that based on coulombic interactions alone, the same level of protection coverglass offers to solar cells can be achieved with about half the thickness of WC1-xBx or less.
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Popescu, Andrei. "Laser deposition and characterization of transparent conductive, bioactive, hydrophobic and antiseptic nanostructures." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4016.
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Les applications présentées dans cette thèse valorisent de diverses manières le principe d'ablation laser, c'est à dire l'arrachement de la matière d'une surface solide suite à l'irradiation avec un faisceau laser. Le plasma généré par irradiation laser impulsionnel a été utilisé pour le dépôt de couches minces ou de nanoparticules et pour l'analyse compositionnelle des couches d'épaisseur nanométrique. Nous avons synthétisé par dépôt laser combinatoire des librairies compositionnelles d'un oxyde mixte transparent d'In et Zn. En utilisant le plasma d'ablation pour le diagnostic compositionnel, nous avons déterminé les concentrations d'indium et de zinc dans les couches minces par spectroscopie laser. Des couches minces de bioverre ont été synthétisées par dépôt laser impulsionnel sur des substrats de titane. En contact avec des cellules ostéoblastes, les bioverres ont stimulé la prolifération et ont augmenté la viabilité. La prolifération des ostéoblastes cultivés sur les couches de bioverre a été 30% supérieure a l'échantillon de contrôle. On a déposé par PLD des couches minces ou nanoparticules adhérentes de ZnO sur des substrats textiles hydrophiles dans un flux d'oxygène ou sous vide pour obtenir des structures avec différentes mouillabilités. En augmentant le nombre d'impulsions laser de 10 à 100 nous avons observé la transition du recouvrement par des nanoparticules isolées vers des couches minces. En fonction de l'atmosphère environnant lors du dépôt, les couches minces et les nanoparticules ont changé leur mouillabilité, passant d'hydrophile en flux d'oxygène à un comportement superhydrophobe (angle de contact de 157°) en cas de dépôt sous videThe applications presented in this thesis exploit in different modes the principle of laser ablation, i.e. the material removal from a solid surface following irradiation with a pulsed laser beam. The plasma generated by laser ablation was used for thin films or nanoparticles deposition and for the compositional analysis of nanometric thin films. We synthesized by combinatorial pulsed laser deposition, thin film libraries of a complex oxide of In and Zn. Using the ablation plasma for compositional diagnostic, we determined the In and Zn concentrations in films by Laser Induced Breakdown Spectroscopy using a procedure based on the spectral luminance calculation of a plasma in local thermodynamic equilibrium. Thin films of bioactive glass were synthesized by pulsed laser deposition, magnetron sputtering and MAPLE on Ti substrates and tested the transfer accuracy by physico-chemical tests and their functionality in vitro. In contact with human osteoblast cells, the bioactive glasses stimulated their proliferation and enhanced their viability. The proliferation of osteoblasts cultivated on bioactive films was 30% superior to the control sample. ZnO thin films or nanoparticles were deposited on hydrophilic textile substrates in oxygen flux or in vacuum in order to obtain structures with different wetting behavior. Increasing the number of laser pulses from 10 to 100, we observed a coating transition from isolated nanoparticles to thin films fully coating the textile fibers. Function of the ambient atmosphere during experiments, the structures changed their wetting behavior, passing from hydrophilic in oxygen flux to superhydrophobic (157°) in case of deposition in vacuum
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Labouret, Timothée. "Irradiation laser ultrabrève de nanobâtonnets d'or individuels en milieu aqueux : photo-génération de phénomènes d'intérêt biomédical." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC078/document.
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Les nanoparticules d’or présentent des propriétés optiques particulières grâce au phénomène de résonance de plasmon de surface. L’irradiation laser d’une nanoparticule au voisinage de sa fréquence de résonance induit deux effets notables : une forte absorption de l’énergie lumineuse et une amplification du champ électromagnétique dans son environnement proche. Grâce à ces deux caractéristiques et à la bonne biocompatibilité de l’or, ces nano-objets peuvent être utilisés pour bon nombre d’applications biomédicales déclenchées par la lumière. Dans ce domaine, les nanobâtonnets d’or (AuNR) sont particulièrement prometteurs. En effet, il est possible d’accorder leur fréquence de résonance via leur rapport d’aspect, par exemple pour la placer dans la fenêtre de transparence relative des tissus biologiques (650–1350 nm). Cette résonance présente alors un facteur de qualité élevé. L’irradiation d’AuNR produit ainsi de multiples effets biologiques complexes, surtout avec des impulsions ultrabrèves intenses. Néanmoins, la physique de l’AuNR en milieu aqueux n’est réellement comprise que dans des conditions plus simples. C’est pourquoi cette thèse vise à mieux comprendre cette multi-physique dans les conditions d’irradiation pertinentes pour la biologie. Elle apporte des éléments de réponse théoriques, numériques et expérimentaux sur la réponse optique transitoire, la dynamique des échanges d’énergies, la génération plasmonique de plasma, la photoluminescence et la production de dérivés réactifs de l’oxygène. Tous ces processus ont un impact biologique ou biomédical. Leur analyse révèle avant tout le rôle prépondérant des électrons chauds en régime ultrabrefGold nanoparticles exhibit specific optical properties thanks to surface plasmon resonance. Laser irradiation close to their resonance frequency induces two main effects : a high absorption of the electromagnetic energy and an enhancement of the electromagnetic field in their close vicinity. In addition, gold is biocompatible. These three features have made them extremely useful for a number of light-triggered biomedical applications. In this field, gold nanorods (AuNRs) specifically show promise. Indeed, their resonance frequency can be tuned by changing their aspect ratio in order to match the window where biological media are relatively transparent (650–1350 nm). Their resonance then exhibits a high quality factor. As a result, light irradiation of AuNRs triggers various complex biological effects, especially when intense, ultrashort pulses are used. Nevertheless, the physics of irradiated AuNRs in aqueous media is only properly understood in more simple situations. That is why this thesis aims at reaching a better understanding of these multi-physics in biologically relevant irradiation conditions. It provides theoretical, numerical and experimental pieces of information about the transient optical response, the dynamics of energy transfer, the plasmon-assisted plasma generation, the photoluminescence and the production of reactive oxygen species. Each of these processes has biological or biomedical impact. Analyzing the underlying mechanisms reveals above all the major role of hot electrons in the ultrashort regime
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Mori, Kazuaki. "Terahertz-wave generation from atomic clusters under the irradiation of intense femtosecond laser pulses." Kyoto University, 2019. http://hdl.handle.net/2433/242607.
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Moening, Joseph Patrick. "Formation of Nano-Sharp Tips and Microbumps on Silicon and Metal Films by Localized Single-Pulse Laser Irradiation." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279052874.
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Marchant, A. L. "Experimental and theoretical studies of surface and volume changes in dielectrics induced by long-pulse RF CO₂ laser irradiation." Thesis, University of Hull, 2012. http://hydra.hull.ac.uk/resources/hull:5763.
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This thesis describes research into infrared (IR) laser irradiation and damage of four commercially significant polymers: polyimide (PI), polyether ether ketone (PEEK), polyethylene terephthalate (PET) and polypropylene (PP). Many research groups have studied the laser ablation and irradiation of polymers, but they have focussed mainly on ultraviolet and pulsed infrared sources. There appears to be little published data for laser irradiation of polymers with IR lasers operating with pulse durations in the range 50µs to 1ms. Laser coupling to polymers is strongly dependent on the absorption coefficient at the emission wavelength. These properties are widely known and used to inform experimental practice but the absorption coefficient used in the literature is usually that measured at room temperature and low power. In this way it does not truly represent typical experimental conditions. It is also commonly assumed that the laser wavelength is constant. In this work the laser wavelength has been determined as a function of time during a typical pulse for a radio frequency (RF) excited CO2 laser. It was found that the emission wavelength could move from as short as 10.53µm to as long as 10.63µm during a 200µs duration pulse. This alone was seen to affect the absorption cofficient of the polymers studied. The absorption coefficient as a function of polymer temperature was measured over all wavelengths. This allowed any changes in the optical coupling during laser heating to be inferred. The change in absorption coefficient as a function of temperature was determined as being -0.40cm-1K-1, 0.86cm-1K-1, 0.48cm-1K-1and 0.04cm-1K-1 for PI, PEEK, PET and PP respectively at a wavelength of 10.59µm. The threshold fluence for damage was determined as a function of the laser pulse duration. Damage included any permanent change to the polymer surface and in this way took into account decomposition and melting, as well as ablation. Together with the absorption coefficient data, this allowed the energy densities to be calculated. For PI and PEEK these were found to be 2.4kJ/cm3 and 1.9kJ/cm3 respectively and agreed with existing data. The threshold energy density was 0.1kJ/cm3 for PET and 0.2kJ/cm3 for PP. These results were smaller than those expected from the literature due to melting rather than ablation taking place. The threshold fluence for each polymer was found to be mostly independent of laser pulse duration over the range investigated. The small thermal diffusivity of the materials was thought to be the reason for this. Calculations using solutions to the heat diffusion equation and a rate limited thermal decomposition model were found to be consistent with the experimental results. Some initial calculations of the effect of including the temperature dependent absorption coefficient indicated that this does indeed affect the temperature profile during and after the laser pulse. It has been shown that the RF CO2 laser is suitable for polymer processing, particularly for applications where spot size and high resolution etching are not an issue. Laser marking, cutting and hole-drilling would be acceptable applications for this laser which offers more choice in terms of duty-cycle and pulse duration than the pulsed TEA CO2 alternatives. Quantification of the thermal and optical properties and the interaction between these two parameters could be extended to other polymers and it is expected that similar behaviours would be observed.
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Jiang, Hao. "Numerical Modeling and Analysis of Micro-structuring on Silicon on Insulator (SOI) Film under Localized Single Pulse Laser Irradiation." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302280541.
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Beaudier, Alexandre. "Etude de l'interaction laser-matière dans les composants optiques en irradiation multiple, en régime nanoseconde et dans l'UV." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0334/document.
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La fatigue du seuil d’endommagement laser dans la silice fondue a été largement étudiée au cours des dernières années, car ce phénomène est directement lié à la durée de vie des matériaux optiques utilisés dans des applications laser, le plus souvent à forte puissance. En effet, dans l’UV, on observe une décroissance du seuil d’endommagement laser quand le nombre de tirs laser augmente. Ce phénomène a été attribué pour ce couple longueur d’onde-matériau à des modifications laser-induites dans le matériau. Sous irradiation laser multiple à 266 nm, en utilisant des impulsions nanosecondes de densité d’énergie constante, nous avons observé que le signal de photoluminescence est modifié jusqu’à l’endommagement. A partir de cela, nous proposons une nouvelle représentation des données expérimentales qui permet de prédire l’apparition d’un endommagement dans le matériau. Cette prédiction réalisée à partir du signal de fluorescence et non de la statistique d’endommagement utilisée jusque-là, permet une économie significative de surface de composant et du temps d’expérience. Afin d’étendre l’intérêt de l’étude à un plus grand nombre d’applications, une extension des résultats à la longueur d’onde de 355 nm est proposée. Nous proposons un modèle où l’endommagement dans la silice fondue sous irradiation multiple à 266 nm est causé par une accumulation de modifications laser-induites induisant de l’autofocalisation non-linéaire. Afin d’essayer de généraliser la méthode de diagnostic de la fatigue par fluorescence, nous avons aussi réalisé des tests préliminaires sur des cristaux optiques non-linéaires bien connus comme le LBO ou le KDPFatigue effects in fused silica have been largely studied in the past years, as this phenomenon is directly linked to the lifetime of high power photonic materials. Indeed, in the UV regime, we observe a decrease of the LIDT (Laser-Induced Damage Threshold) when the number of laser shots increases and this has been attributed for this couple wavelength/material to laser-induced material modifications. Under 266 nm laser irradiation, with nanosecond pulses of constant fluence, we observed that the photoluminescence is modified until damage occurs. Based on this observation, we propose a new representation of the experimental S-on-1 breakdown data which allows predicting the occurrence of material breakdown. This prediction, based on fluorescence signal and not damage statistics (presently widely used) allows consuming fewer sample surface and saving time. To extend the interest of the study to many more applications, we propose an extension of the results at 355 nm. We suppose that damage is caused in our fused silica samples by accumulation of laser-induced modifications under multiple-pulse UV irradiation inducing catastrophic non-linear self-focusing. In order to try to extend the fatigue diagnostic method by fluorescence, we have also realized preliminary tests in well-known non-linear crystals like LBO and KDP
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Gouldieff, Céline. "Etude de l'interaction laser-matière en régime nanoseconde sous irradiations multiples : application aux composants optiques pour l’UV." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4328.
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Les travaux portent sur l’endommagement laser en régime nanoseconde aux longueurs d’onde 355 nm et 266 nm. L'objectif de cette étude est de comprendre et d'analyser les processus mis en jeu lors de l'endommagement laser en surface et en volume de matériaux optiques, massifs ou en couches minces, lors de tirs répétés. Dans ce contexte, un banc d'endommagement laser a été entièrement mis en place et automatisé. Il permet d'analyser la résistance et le vieillissement de ces composants sous irradiation UV à des fréquences de tir de 50Hz, pour un grand nombre de tirs et de relever de façon systématique les paramètres du test les plus importants (profiles spatiaux et énergies des impulsions, images du site avant et après dommage). Pour une meilleure compréhension des phénomènes physiques conduisant à la fatigue des matériaux en tirs laser répétés, un modèle a été développé afin de discriminer les effets statistiques (dus au grand nombre de tirs impliqués) de modifications du matériau sous flux UV. Ce modèle a été validé expérimentalement dans le cas de la silice synthétique étudiée en volume. En ce qui concerne les couches minces, une étude multi-paramètres de la tenue au flux UV de mixtures d'oxydes a été menée, en partenariat avec le Laser Zentrum Hannover (LZH, Allemagne). Ces matériaux ont en effet un comportement complexe et encore mal connu, en particulier en tirs répétés. Enfin, une partie du travail de thèse est consacrée à la caractérisation non-destructive de cristaux de KDP par photoluminescence pompée dans l'UV, réalisée dans le contexte du laser MégaJoule en collaboration avec le CEA Le Ripault (Monts)The work is devoted to laser-induced damage in the nanosecond regime at the wavelengths of 266 nm and 355 nm. The goal of this study is to understand and to analyze the processes taking place during multi-pulse irradiation causing laser-damage, on the surface and in the bulk of massive or thin-films optical materials. To this end, a laser-damage experiment was entirely set up and automated. It allows analyzing the laser-damage resistance and the ageing of these components under UV irradiation at a pulse repetition rate of 50 Hz and for a high number of laser pulses and to record systematically the most important test parameters (spatial beam profiles, energies, images of the site before and after irradiation).To better understand the physical phenomena leading to fatigue effects in the materials under multiple pulse irradiation, a model was developed allowing the discrimination of statistical effects (due to the high number of shots) from material modifications under UV irradiation. This model was confirmed by testing synthetic fused silica irradiated in the bulk. Concerning thin-film coated components, oxide mixtures were studied in collaboration with the Laser Zentrum Hannover (LZH, Germany) using a multi-parameter approach. These materials show indeed a complex behavior and remain poorly known, in particular under multi-pulse irradiation. Finally, a part of the work is dedicated to the non-destructive characterization of KDP crystals by UV-pumped photoluminescence, realized in the framework of the MegaJoule project, in collaboration with CEA Le Ripault (Monts, France)
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ROSSI, WAGNER de. "Construcao e operacao de lasers de neodimio: estudo do comportamento temporal." reponame:Repositório Institucional do IPEN, 1995. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10435.
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Made available in DSpace on 2014-10-09T12:38:43Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:03Z (GMT). No. of bitstreams: 1 06043.pdf: 11141670 bytes, checksum: 6dd9b63e574d6cd26d0271a82c9dd0ef (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Wang, Jin Jimmy. "Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation." Thesis, 2016. https://doi.org/10.7916/D8NV9J7Q.
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This thesis examines melting in superheated silicon films in contact with SiO₂ under pulsed laser irradiation. An excimer-laser pulse was employed to induce heating of the film by irradiating the film through the transparent fused-quartz substrate such that most of the beam energy was deposited near the bottom Si-SiO₂ interface. Melting dynamics were probed via in situ transient reflectance measurements. The temperature profile was estimated computationally by incorporating temperature- and phase-dependent physical parameters and the time-dependent intensity profile of the incident excimer-laser beam obtained from the experiments.
The results indicate that a significant degree of superheating occurred in the subsurface region of the film. Surface-initiated melting was observed in spite of the internal heating scheme, which resulted in the film being substantially hotter at and near the bottom Si-SiO₂ interface. By considering that the surface melts at the equilibrium melting point, the solid-phase-only heat-flow analysis estimates that the bottom Si-SiO₂ interface can be superheated by at least 220K during excimer-laser irradiation.
It was found that at higher laser fluences (i.e., at higher temperatures), melting can be triggered internally. At heating rates of 10¹⁰ K/s, melting was observed to initiate at or near the (100)-oriented Si-SiO₂ interface at temperatures estimated to be over 300K above the equilibrium melting point. Based on theoretical considerations, it was deduced that melting in the superheated solid initiated via a nucleation and growth process. Nucleation rates were estimated from the experimental data using Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Interpretation of the results using classical nucleation theory suggests that nucleation of the liquid phase occurred via the heterogeneous mechanism along the Si-SiO₂ interface.
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Wesolowski, Michal John. "Properties of Carbon Nanomaterials Produced by Ultrashort Pulsed Laser Irradiation." Thesis, 2012. http://hdl.handle.net/10012/6904.
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Two synthesis pathways were employed throughout this work to create a variety of unique carbon materials. The first of these routes involves the photo-dissociation of liquids by direct irradiation with ultrashort laser pulses; while the second entails the bombardment of polycrystalline chemical layers by a pulsed laser induced carbon plasma.
The pulsed laser irradiation (PLI) of liquid benzene (C6H6) was found to result in the formation of amorphous carbon nanoparticles consisting of clusters of sp2-bonded aromatic rings bridged by sp hybridized polyyne functionalities. In a complimentary experiment, liquid toluene (C6H5CH3) was irradiated under similar conditions leading to the synthesis of a series of free floating methyl capped polyynes, with chain lengths ranging from C10 – C20. The synthesis of polyynes is an active and cutting edge topic in material science and chemistry. In a more complex experiment, solutions of ferrocene and benzene were irradiated by fs-laser pulses resulting in highly ordered mesoscale structures exhibiting four unique geometries; ribbons, loops, tubes, and hollow spherical shells. After a purification process, the higher order structures were destroyed and replaced with nanoparticles consisting of three distinct species including; pure iron, and two phases in which part of the ferrocene molecule was bound to either carbon or iron/carbon complexes. This material is extremely interesting because it exhibits properties similar to that of an electret and is also ferromagnetic over a large temperature range. In the final liquid phase laser irradiation experiment, a new hybrid deposition technique was originated and used to coat stainless steel electrodes with disordered mesoporous nanocrystalline graphite. This method involves the laser induced breakdown of benzene and the subsequent electrodeposition of the resulting carbon ions.
Another focus in this work involved the synthesis of a special class of polymer-like carbon nanomaterials using a new method that augments traditional pulsed laser deposition. This technique involves the plasma processing of frozen materials with a pulsed laser initiated graphitic plasma. We call this technique "pulsed laser induced plasma processing" or "PLIPP". Various thin film compositions were created by processing alkane and alkene ices. Finally, in a slight departure from the previous experiments, the effects of carbon ion bombardment on water ice were examined in an effort to understand certain astrophysical processes.
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Kim, Jihoon. "Measurement of optical path length change in response to pulsed laser irradiation using phase sensitive OCT." Thesis, 2006. http://hdl.handle.net/2152/2738.
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Mohanan, Senthilnathan [Verfasser]. "Tailoring the magnetic anisotropy of thin films utilizing large persistent stress and pulsed laser irradiation / von Senthilnathan Mohanan." 2008. http://d-nb.info/1000832627/34.
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Hashem, Mjed H. "Laser Based Pre-treatment of Secondary Bonded Composite T-joints for Improved Energy Dissipation." Thesis, 2004. http://hdl.handle.net/10754/669124.
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This study demonstrates an experimental investigation into the efficacy of a novel surface pre-treatment technique to improve the toughness and energy dissipation of composite CFRP T-joints. This novel technique optimizes CO2 laser irradiations to remove surface contaminations and modify the surface morphology of CFRP T-joint adherents. Pull-off tests were performed on T-joints that experienced peel-ply (PP) treatment and to those that were ablated with 10% (LC) and 30% (LA) laser power respectively. A further developed alternative pattern between LA and LC surface pre-treatment was examined. Two different quasi-isotropic stacking sequences have been studied by having surface fibers aligned in 0° and 45° direction. A series of surface roughness analysis, optical microscopy, SEM, CT scan and pictorial findings have been carried out to characterize the surface morphologies and failure modes prior to and after the failure. The patterning technique promoted non-local damage mechanisms which resulted in large improvements in the toughness and energy dissipation as compared to the other pre-treatment techniques. Up to ~12 times higher energy dissipation compared to peel-ply pre-treated T-joint were achieved with patterned T-joint structures that are stacked with a 0° surface fiber direction.
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Hashem, Mjed H. "Laser Based Pre-treatment of Secondary Bonded Composite T-joints for Improved Energy Dissipation." Thesis, 2021. http://hdl.handle.net/10754/669124.
Full textAbstract:
This study demonstrates an experimental investigation into the efficacy of a novel surface pre-treatment technique to improve the toughness and energy dissipation of composite CFRP T-joints. This novel technique optimizes CO2 laser irradiations to remove surface contaminations and modify the surface morphology of CFRP T-joint adherents. Pull-off tests were performed on T-joints that experienced peel-ply (PP) treatment and to those that were ablated with 10% (LC) and 30% (LA) laser power respectively. A further developed alternative pattern between LA and LC surface pre-treatment was examined. Two different quasi-isotropic stacking sequences have been studied by having surface fibers aligned in 0° and 45° direction. A series of surface roughness analysis, optical microscopy, SEM, CT scan and pictorial findings have been carried out to characterize the surface morphologies and failure modes prior to and after the failure. The patterning technique promoted non-local damage mechanisms which resulted in large improvements in the toughness and energy dissipation as compared to the other pre-treatment techniques. Up to ~12 times higher energy dissipation compared to peel-ply pre-treated T-joint were achieved with patterned T-joint structures that are stacked with a 0° surface fiber direction.
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KUO, I.-HSIANG, and 郭翊翔. "Effects of Pulsed KrF Laser Irradiation and Ion Implantation on the Growth and Properties of Liquid-Phase-Deposited SiO2." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/66118729964427498946.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系
88
Effects of the H2SiF6 concentration, pulsed KrF laser irradiation, and ion implantation on the growth and electrical properties of liquid phase deposition (LPD) SiO2 were studied. The F concentration in the LPD SiO2 increased with the H2SiF6 concentration, resulting in the increase of effective oxide charges and hence the leakage current, and the decrease of the dielectric constant of LPD SiO2, respectively. During LPD pulsed KrF irradiation did not apparently increase the growth rate of SiO2, however, it decreased the F concentration in SiO2. After N2+ implantation with a dose of 1x1015/cm2 some Si-F bonds in LPD SiO2 were replaced by the Si-N bonds from FTIR analysis, resulted in lower effective oxide charges and hence lower leakage current of LPD SiO2. Concomitantly, the dielectric constant of LPD SiO2 was increased. After C+ implantation with a dose of 1x1015/cm2 the effect oxide changes of LPD SiO2 were increased, however, its dielectric constant and leakage current were decreased.
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Chen, Wen-Yi, and 陳文乙. "Study of Graphene Thin-Film-Based Device for Polymerase Chain Reaction Using Ultra-Violet Ultra-Short Pulsed Laser Irradiation." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/36243060222170529142.
Full textAbstract:
碩士國立臺灣師範大學
機電工程學系
104
In this study, the graphene-based micro-heater can be fabricated by the advanced laser micromachining and spinning-coating techniques for thin-film device. Based on electrical and thermal characteristics of graphene-based device, the control program and circuit design for developing polymerase chain reaction (PCR) chip can be performed to deoxyribonucleic acid(DNA) amplification. The results of this study found that the length of the shorter micro-heater and the width of wider graphene-based electrode channel where the heating characteristics indicate their better. That is to use of less energy can achieve the predicted temperature. In order to DNA amplification in the small chamber on the micro-heater device, the study is to use the design of micro-heater (length: 9 mm; width: 1 mm) with the LabView program control, the solid state relays (SSR) and pulse width modulation circuit to achieve the single voltage source input and multi-source voltage output. The study can be applied to practical PCR chip reaction with three step temperature control, including 90-95 °C, 50-55 °C and 72-78 °C. Through the experimental parameters control, this study can be done DNA amplification experiments. The measured results reveal the its amplification condition. It demonstrates that the graphene-based micro-heater device can be performed and will have the opportunity to develop the design and fabrication of practical PCR chip products.
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Kim, Kyunghan. "The thermal response of biological tissue subjected to short-pulsed irradiations." 2008. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051761.
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Murphy, Brendan Francis 1976. "Dynamics of noble gas cluster expansion driven by intense pulses of extreme ultraviolet light." 2009. http://hdl.handle.net/2152/10580.
Full textAbstract:
The interaction of intense laser pulses with nanometer scale atomic clusters has been an active area of study since the advent of amplified femtosecond lasers. In the case of infrared irradiation of noble gas clusters, direct field-driven ionization results in the ejection of energetic electrons, high ion charge states, and Coulomb explosion of the ion core of the clusters. These processes result from electron motion driven by the cluster potential and the large ponderomotive potential of the laser field. When extreme ultraviolet (XUV) pulses interact with clusters, the mechanisms responsible for the infrared response are 'turned off' because the ponderomotive potential is very small. We have conducted cluster experiments at 38nm using focused XUV pulses produced by high harmonic generation with a 15TW Ti:Sapphire laser. We measured the charge states and kinetic energy spectra of ions produced in the interaction, and observe substantial ion population up to Xe⁵⁺, with a small number of Xe⁶⁺-Xe⁸⁺ ions produced by collisional ionization by hot plasma electrons. The ion kinetic energy spectrum indicates a hydrodynamic expansion at an ion temperature of 8eV. This is in stark contrast to intense infrared/cluster interactions, where clusters are stripped of electrons to a large degree and expand by Coulomb forces, resulting in far higher ion kinetic energy for similar degrees of ionization.text
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BERHE, ANDERGACHEW MEKONNEN, and Tazebey. "Synthesis and properties of gold quantum particles under femtosecond pulse laser irradiation and their effect on ZnO-based DSSC." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/g24m5w.
Full textAbstract:
碩士國立臺灣科技大學
應用科技研究所
107
Gold quantum clusters and nanoparticles were synthesized and studied their property under femtosecond laser irradiation in water. Additionally, the produced plasmonic gold nanoparticles were also used for dye-sensitized solar cell (DSSC) application. Hence, synthesis, quantum property and respective applications of the gold nanoparticles are the major objectives of the study. In the first work, the synthesis and factors that govern their quantum properties of gold quantum clusters and nanoparticles under femtosecond laser pulses irradiation in water were studied. In the experiments, gold quantum clusters, and nanoparticles were produced by irradiating femtosecond laser to the gold ions without adding any reducing agent. Atomic force microscopy, transmission electron microscope, high resolution-transmission microscope, UV-Visible spectroscopy and some calculations were applied to analyze their quantum property of the produced particles. The size and properties of quantum clusters and nanoparticles can be studied through the influence of irradiation time and intensity of femtosecond pulse laser. The strategy leads to improve the understanding about quantum properties of gold atomic clusters (quantum clusters). The results particularly reflected the transition from isolated atoms to nanoparticles and demonstrated advantages of physical reduction method compared to chemical methods with regard to technical simplicity, product purity and size controllability. In the second work, zinc oxide (ZnO) nanowires were grew by in situ method on flexible substrate This conductive composite film was used as a substrate to deposit composites of ZnO nanoparticles, carbon dots and gold nanoparticles working electrodes of the dye-sensitized solar cells (DSSCs), where plasmonic gold nanoparticles were produced under femtosecond laser irradiation. The optimized photoanodes provided the efficiency of conductive polymer flexible film counter electrode. This efficiency was lower than that of DSSC consisting of a composite working electrode plasmonic gold nanoparticles with ZnO nanoparticles on solid conductive substrate and a Pt counter electrode.