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Dissertations / Theses on the topic 'Laser micro'
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1
Sierra, Hernández Wilfrido 1975. "Micro laser personal projector." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29704.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2003.Includes bibliographical references (p. 79-81).
The proposed research is a study of the technology and applications of personal projectors, small and inexpensive video projection devices intended for use in battery-powered hand-held or wearable products. This research will describe some ways of steering laser beams in one dimension to produce up to a one-meter wide screen. A one dimensional micro laser array will be used to avoid the effect of flickering while projecting an image. The use of a single lens to focus all lasers will save the complexity of collimating each laser independently. At the moment, the Micro Laser Personal Projector is displaying an image of 50 x 480 pixels. A DC brushless motor is used to steer the laser beams vertically. A fixed plano-convex lens focuses all 50 lasers. A piezo-electric device will be used on the future to increase the laser projector's image resolution from 50 x 480 to 200 x 480 pixels. With this image resolution the Micro Laser Personal Projector can be used in communications, entertainment, and medical applications.
by Wilfrido Sierra Hernández.
S.M.
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Wu, Songping. "Femtosecond laser micro-structuring of silicon wafer in water confinement." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Wu_09007dcc80493fda.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 3, 2008) Includes bibliographical references (p. 66-74).
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Kumar, Mukund. "Laser assisted micro milling of hard materials." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41213.
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This thesis presents an investigation of novel laser assisted micromachining processes that addresses the limitations of micromachining of hard-to-machine materials. Two different laser assisted approaches are used to machine hard metals and high strength ceramics. For hard metals, the basic approach involves localized thermal softening of the workpiece material by focusing a solid-state continuous wave near infra-red laser beam in front of the micro milling tool (end mills of 0.1 to 0.5 mm diameter). By suitably controlling the laser power, spot size and scan speed, it is possible to produce a sufficiently large reduction in the flow strength of the work material and consequently the cutting forces and tool deflections. A force model is developed to predict the cutting forces in Laser Assisted Micro Milling (LAMM) of hard metals. For high strength ceramics, the approach involves use of a two step process. In the first step, thermal cracks are generated in a confined volume by the steep thermal gradients generated by laser irradiation of the workpiece. In the second step, the weakened region is removed by a micro grinding tool. The characterization and modeling of the process serve as bases for users of the two approaches to select optimal process parameters.
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Mendez, Fernandez de Cordoba Enrique. "Laser micro-polishing of silica optics." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/80.
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Lorenz, Norbert. "Laser-based packaging of micro-devices." Thesis, Heriot-Watt University, 2011. http://hdl.handle.net/10399/2491.
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In this PhD thesis the development of laser-based processes for packaging applications in microsystems technologies is investigated. Packaging is one of the major challenges in the fabrication of micro-electro-mechanical systems (MEMS) and other micro-devices. A range of bonding processes have become established in industry, however, in many or even most cases heating of the entire package to the bonding temperature is required to effect efficient and reliable bonding. The high process temperatures of up to 1100°C involved severely limit the application areas of these techniques for packaging of temperature sensitive materials. As an alternative production method, two localised heating processes using a laser were developed where also the heat is restricted to the joining area only by active cooling. Silicon to glass joining with a Benzocyclobutene adhesive layer was demonstrated which is a typical MEMS application. In this laser-based process the temperature in the centre of the device was kept at least 120°C lower than in the bonding area. For chip-level packaging shear forces as high as 290 N were achieved which is comparable and some cases even higher than results obtained using conventional bonding techniques. Furthermore, a considerable reduction of the bonding time from typically 20 minutes down to 8 s was achieved. A further development of this process to wafer-level packaging was demonstrated. For a simplified pattern of 5 samples the same quality of the seal could be achieved as for chip-level packaging. Packaging of a more densely packed pattern of 9 was also investigated. Successful sealing of all nine samples on the same wafer was demonstrated proving the feasibility of wafer-level packaging using this localised heating bonding process. The development of full hermetic glass frit packaging processes of Leadless Chip Carrier (LCC) devices in both air and vacuum is presented. In these laser-based processes the temperature in the centre of the device was kept at least 230°C below the temperature in the joining region (375°C to 440°C). Testing according to MIL-STD-883G showed that hermetic seals were achieved in high yield processes (>90%) and the packages did withstand shear forces in excess of 1 kN. Residual gas analysis has shown that a moderate vacuum of around 5 mbar was achieved inside the vacuum packaged LCC devices. A localised heating glass frit packaging process was developed without any negative effect of the thermal management on the quality of the seal.
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Powell, Rock Allen. "On-line depth measurement of micro-scale laser drilled holes." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Powell_09007dcc806b6dfc.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 14, 2009) Includes bibliographical references (p. 16-17).
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Penchev, Pavel Nedyalkov. "Reconfigurable laser micro-processing systems : development of generic system-level tools for implementing modular laser micro-manufactoring platforms." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6709/.
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Laser micro-machining (LMM) is an attractive manufacturing technology for the fabrication of a wide range of micro-components due to its intrinsic processing attributes. In addition, LMM can be integrated in hybrid manufacturing platforms and thus to combine LMM with other complementary processes for the cost effective fabrication of a broader range of miniaturised products. Nevertheless, the broader industrial uptake of LMM is still to come due to system-level issues in designing and implementing LMM systems. In this context, the research reported in this thesis is aimed at improving the system-level performance of reconfigurable LMM platforms and thus to create the necessary pre-requisites for achieving a much better machining accuracy, repeatability and reproducibility (ARR) in different processing configurations. First, a systematic approach for assessing and characterizing the manufacturing capabilities of LMM platforms in terms of ARR is proposed. Then, the development of generic integration tools for improving the system-level performance of reconfigurable LMM platforms in terms of manufacturing flexibility and reliability both as stand-alone machine tool configurations and also as component technologies in multi-process manufacturing solutions is presented. Next, generic software tools are proposed and validated for improving the manufacturing capabilities of LMM systems for realizing complex multi-axis laser processing strategies with a closed-loop manufacturing control. Finally, the integration of LMM in process chains is validated to extend the capabilities of well proven conventional manufacturing routes, i.e. micro milling, for the fabrication of miniaturised products, i.e. Terahertz technology devices, which have complex and challenging-to-fabricate functional features and overall designs.
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Choi, Hae Woon. "Femtosecond laser material processing for micro-/nano-scale fabrication and biomedical applications." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1184883900.
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Tsopanos, Sozon. "Micro Heat Exchangers by Selective Laser Melting." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507633.
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Selective Laser Melting (SLM), a layer-based Solid Freeform Fabrication (SFF) process, was used to fabricate micro cross-flow heat exchangers from 316L stainless steel, bronze (Cu 90%, Sn 10%) and Inconel 718 powder. Their mechanical and thermal properties were determined using solid blocks of SLM material prior to the fabrication of the micro cross flow heat exchangers. Initially the process parameters for the fabrication of high density (>97%) parts for the different materials were defined. The mechanical and thermal properties of SLM parts were then measured. The tensile test results exhibited yield strength values superior to the parent metals, but also showed low tensile strength and ductility as a result of the inherent residual porosity (2-4%). Results obtained from the thermal conductivity of the stainless steel material system were in good agreement with the bulk material values. The heat transfer performance of the heat exchangers with either micro channels or lattice structures as heat exchange surfaces was investigated experimentally and the results were evaluated in terms of geometry and materials. The performance of the micro heat exchangers was found to be dependent not only on the choice of material but also on the heat exchanger media geometry.
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Sun, Bangshan. "Direct laser micro-fabrication by adaptive optics." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:dc127fab-1ad9-4f23-913e-9ba6438e8934.
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Ultrafast lasers are widely used for the precise three-dimensional micro-fabrication inside transparent materials. The resolution of fabricated features depends upon the size of the focal spot, and the process efficiency depends upon the generation of short pulses at the focus. The performance is detrimentally affected by the presence of phase aberrations, which can be introduced by the optics of the system or by refraction at the surface of material. Efficiency can also be affected by other forms of aberration that are related to the ultra-short pulses, such as pulse front distortion or material dispersion. Adaptive optics has in the past been introduced into laser material processing in order to overcome the problems caused by phase aberrations. However, there are related phenomena specific to systems using ultrashort pulses that have not been extensively studied, nor have benefitted from the application of adaptive optics. This thesis concerns the development of theoretical and practical techniques to address these issues and improve the performance of laser fabrication system. New applications are enabled with this technology. Spatiotemporal modelling of laser focal intensity distribution is enabled by adopting the Fourier optics. The effects of phase aberrations and sample dispersion on the ultrafast laser focusing are studied in detail. Simulations for both conventional and temporal laser focusing methods are presented. I explore the significance of individual aberration and sample dispersion to investigate the benefit of their compensation in various practical scenarios. A new method in controlling the ultrafast laser pulses - pulse front adaptive optics - is introduced. With the combination of a deformable mirror (DM) and a spatial light modulator (SLM), quadratic shape pulse fronts with different magnitudes are created. The results are demonstrated through wave-front sensor and auto-correlator measurements. In addition, I introduce the first application of this method into the pulse front correction for a two-photon microscope. An improvement of 1.4 times in the two-photon signal beyond the phase correction is demonstrated. A series of new applications are enabled by adopting the adaptive optics into laser fabrication. In the adaptive laser fabrication in diamond, graphitic wires with any three-dimensional shapes are enabled. The resistivity of the wires is demonstrated to be reduced by more than 100 times compared to the previous reports. Non-reciprocal effects in the diamond fabrication are studied in detail. The influence of laser parameters, light polarization and pulse front tilt are investigated. I also explore several more advanced applications in the diamond fabrication. Specifically, initial results of the alternating conductor, micro-capacitor and electrode arrays for radiation detector are presented. Additionally, I discuss micro-fabrication of three dimensional funnel structures in silica glass for applications in neuroscience research.
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Campos, Zatarain Alberto. "Diode laser modules based on laser-machined, multi-layer ceramic substrates with integrated water cooling and micro-optics." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2595.
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This thesis presents a study on the use of low temperature co-fired ceramic (LTCC) material as a new platform for the packaging of multiple broad area single emitter diode lasers. This will address the recent trend in the laser industry of combining multiple laser diodes in a common package to reach the beam brightness and power required for pumping fibre lasers and for direct-diode industrial applications, such as welding, cutting, and etching. Packages based on multiple single emitters offer advantages over those derived from monolithic diode bars such as higher brightness, negligible thermal crosstalk between neighbouring emitters and protection against cascading failed emitters. In addition, insulated sub-mounted laser diodes based on telecommunication standards are preferred to diode bars and stacks because of the degree of assembly automation, and improved lifetime. At present, lasers are packaged on Cu or CuW platforms, whose high thermal conductivities allow an efficient passive cooling. However, as the number of emitters per package increases and improvements in the laser technology enable higher output power, the passive cooling will become insufficient. To overcome this problem, a LTCC platform capable of actively removing the heat generated by the lasers through impingement jet cooling was developed. It was provided with an internal water manifold capable to impinge water at 0.15 lmin-1 flow rate on the back surface of each laser with a variation of less than 2 °C in the temperature between the diodes. The thermal impedance of 2.7°C/W obtained allows the LTCC structure to cool the latest commercial broad area single emitter diode lasers which deliver up to 13 W of optical power. Commonly, the emitters are placed in a “staircase” formation to stack the emitters in the fast-axis, maintaining the brightness of the diode lasers. However, due to technical difficulties of machining the LTCC structure with a staircase-shaped face, a novel out-plane beam shaping method was proposed to obtain an elegant and compact free space combination of the laser beam on board using inexpensive optics. A compact arrangement was obtained using aligned folding mirrors, which stacked the beams on top of each other in the fast direction with the minimum dead space.
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Kuang, Zheng. "Parallel diffractive multi-beam ultrafast laser micro-processing." Thesis, University of Liverpool, 2011. http://livrepository.liverpool.ac.uk/1333/.
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During the last decade, ultrashort pulse lasers have been employed for high precision surface micro-structuring of materials such as metals, semiconductors and dielectrics with little thermal damage. Due to the ultra high intensity of focussed femtosecond pulses (I > 1012W/cm2), nonlinear absorption can be induced at the focus leading to highly localised material ablation or modification. This is now opening up applications ranging from integrated optics, through multi-photon induced refractive index engineering to precision surface modification for silicon scribing and solar cell fabrication. To ensure non thermal material processing, the input fluence (F) of the ultrashort pulse laser must be kept in the low regime (F ∼ 1Jcm-2), a few times above the well defined ablation threshold. Accordingly, μJ (10-6J) level pulse energy input is often required for ultrashort pulse laser fine micro/nano-surface structuring. Running at one kilohertz repetition rate, many current ultrashort pulse laser systems can provide mJ (10-3J) level output pulse energy. Accordingly, significant attenuation of the laser output is required for many applications and hence causes a great deal of energy loss. With this limitation in mind, holographic multiple beam ultrashort pulse laser processing, where the mJ pulse energy is split into many desired diffracted beams with arbitrary geometric arrangement, is proposed in this thesis. The multi-beam patterns are generated by phase modulation using computer generated holograms (CGHs) which are displayed on a Spatial Light Modulator (SLM). The ability to address these devices in real time and synchronize with scanning methods adds an additional flexibility to the processing. The results obtained in this thesis demonstrate high precision micro-fabrication of different kinds of materials with greatly increased processing efficiency and throughput, showing many potential industrial applications.
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Li, Qingfeng. "Double-pulse laser-induced forward transfer." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0033/document.
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Pour résoudre la limitation inhérente au procédé d’impression laser LIFT, une approche utilisant une double impulsion (DP-LIFT) a été développée au cours de cette thèse. Dans ce processus, une irradiation laser de durée de quelques dizaines de microsecondes crée un bain de métal en fusion et une seconde impulsion ultra-brève induit le mouvement du fluide, la formation d’un jet ou d’une goutte et le transfert du métal liquide. Cette thèse présente une étude expérimentale détaillée sur le processus DP-LIFT. L'influence des paramètres des deux irradiations laser a été étudiée en s’appyuant sur un ensemble de méthodes d'observation. Pour étudier l’influence de ces paramètres sur la dynamique de l’éjection, un modèle basé sur la conservation de l’énergie a été utilisé. De plus, nous avons démontré que, pour certaines configurations des diamètres respectifs des deux spots lasers, des nanojets focalisés étaient générés. Enfin, en conservant une épaisseur fixe du film métallique, des gouttelettes uniques, sans débris, d'un diamètre allant de 670 nm à 6,0 µm ont été imprimées avec une reproductibilité élevée. des matrices de piliers ont également été imprimées pour démontrer le potentiel de la méthode LIFT à double impulsion pour la fabrication de micro-structures 3DTo solve the inherent limitation of Laser-induced Forward Transfer (LIFT), a double pulse LIFT (DP-LIFT) approach has been developed in this thesis. In this process, a first long pulse laser irradiation creates a melted metal pool and a second ultrashort pulse induces the fluid motion and initiates the jetting transfer. This thesis provides a detailed experimental study on the DP-LIFT process. The influence of double pulse parameters on the jetting phenomena has been carefully studied by means of various observation methods. To predict the jetting behaviors, an energy balanced model has been used. Moreover, we demonstrated that for some configurations of the respective diameters of the two lasers, focused nanojets are generated from the melting pool. Finally, from a fixed thickness of the donor film, debris-free single droplets with diameters ranging from 670 nm to 6.0 µm have been printed with high reproducibility. 2.5 D pillars matrix are printed to demonstrate the potential of the double pulse LIFT method for the fabrication of 3D micro-structures
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Biasotto, Cleber. "Processos alternativos para micro e nanotecnologia." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260856.
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Orientador: Jose Alexandre DinizTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-21T20:16:28Z (GMT). No. of bitstreams: 1 Biasotto_Cleber_D.pdf: 3795677 bytes, checksum: e4e2355f73ec8fb2ad7677cdf17f5daf (MD5) Previous issue date: 2012
Resumo: Atualmente para atender à necessidade de fabricação dos sensores, dispositivos eletrônicos e circuitos integrados com dimensões micro e nanométricas, novos processo de custos e de thermal budgets reduzidos são necessários. Este trabalho apresenta o desenvolvimento de alguns destes novos processos alternativos para aplicação nesta fabricação. O trabalho está dividido em quatro partes: a primeira parte apresenta a obtenção e a caracterização de filmes isolantes de nitreto de silício para aplicação em microsensores, tais como o sensor de pressão. Estes filmes foram obtidos sobre substratos de Si em baixa temperatura (20°C) utilizando-se um reator de plasma do tipo ECRCVD (Electron Cyclotron Resonance - Chemical Vapor Deposition). Normalmente reatores do tipo Low Pressure Chemical Vapor Deposition (LPCVD) ou Plasma Enhanced - CVD (PECVD) em temperaturas maiores que 600ºC e 250ºC, respectivamente, são utilizados para essa aplicação. A caracterização dos plasmas ECR, que foram usados para as deposições dos nitretos, e a fabricação de membranas suspensas com estes filmes são apresentadas. A segunda parte apresenta a fabricação e a caracterização de diodos p+-n fabricados em camada de SiGe crescida por LPCVD sobre substrato de Si. Processo este alternativo em substituição aos executados em reatores epitaxiais de alto custo. Na terceira parte deste trabalho, é apresentado o desenvolvimento de processos em baixa temperatura para aplicação em diodos e tecnologia MOS (Metal-Oxide-Semiconductor). São apresentadas a fabricação e a caracterização elétrica dos capacitores MOS, utilizando as tecnologias ALD (Atomic Layer Deposition) e ICP (Inductively Coupled Plasma) para a obtenção em baixa temperatura dos dielétricos high-k de Al2O3 e SiON de porta MOS, respectivamente. Na quarta parte, são apresentadas também, a fabricação e a caracterização elétrica de diodos n+p utilizando a tecnologia de recozimento a laser. O desenvolvimento de capacitores MOS e diodos possibilitou a fabricação (usando processos em baixa temperatura (?400oC)) de n- e p-MISFETs (Metal- Insulator-Semiconductor Field Effect Transistors), como também a fabricação de um protótipo de transistor MOS de alta velocidade baseado em silício germânio chamado D-DotFET (Disposable Dot Field Effect Transistor). Os processos alternativos desenvolvidos nesta tese apresentam um enorme potencial para aplicação nas próximas gerações de dispositivos CMOS (Complementary Metal Oxide Semiconductor) de dimensões sub-22 nm
Abstract: Nowadays, to attend the needs of the fabrication of sensors, electronic devices and integrated circuits with dimensions of micro and nanometrics, new processes of reduced costs and thermal budgets are needed. This work presents the development of some of these alternative processes for this fabrication. This work is divided in four parts: the first part presents the synthesis and characterization of insulating films of silicon nitride for application in microsensors, such as pressure sensors. These films were deposited on Si substrates at low temperature (20°C) using an ECR-CVD (Electron Cyclotron Resonance - Chemical Vapor Deposition) plasma reactor. Normally, Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma Enhanced CVD - (PECVD) reactors are used for this application with high temperature process higher than 600oC and 250oC, respectively. The characterization of ECR plasmas, which were used to get the silicon nitrides, and the fabrication of suspended membranes based on these nitrides are presented. The second part presents the fabrication and the characterization of p+-n silicon germanium (SiGe) diodes fabricated on SiGe layers, which were grown by LPCVD on Si substrate. The grown of SiGe layers by LPCVD is an alternative process to replace the high cost of epitaxial reactors. In the third part of this work is presented the development of low-temperature processes for application in diodes and MOS (Metal-Oxide-Semiconductor) technology. The fabrication at low temperature and electrical characterization of MOS capacitors, using technologies as: ALD (Atomic Layer Deposition) and ICP (Inductively Coupled Plasma) to get the Al2O3 and SiON high-k gate dielectrics of MOS capacitors are presented, respectively. In the four part, the fabrication and electrical characterization of n+-p diodes using the process of laser annealing are presented as well. The development of MOS capacitors and diodes have become feasible the fabrication (using processes at low temperature (? 400oC)) of n- and p-MISFETs (Metal- Insulator -Semiconductor Field Effect Transistors) and also the fabrication of a high speed MOS transistor prototype based on silicon germanium named D-DotFET (Disposable Dot Field Effect Transistor). In conclusion, the alternative processes developed in this thesis have shown to be a huge potential for application in next generations of CMOS (Complementary Metal Oxide Semiconductor) devices with sub- 22 nm dimensions
Doutorado
Eletrônica, Microeletrônica e Optoeletrônica
Doutor em Engenharia Elétrica
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Hsu, Shu-Ting. "High performance micro scanners for miniature laser projection displays." Dresden TUDpress, 2009. http://d-nb.info/996064125/04.
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TARAZONA, SCAGLIA VERONIQUE. "Etude et realisation d'elements de micro-optique pour la stabilisation de micro-cavites laser." Paris 11, 1996. http://www.theses.fr/1996PA112138.
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Les microlasers solides a cavites a faces planes et paralleles presentent des seuils assez eleves. En effet les cavites de ces lasers sont stabilisees uniquement par des effets thermiques dans le cristal, induits par le faisceau de pompe. Le but de cette these etait de realiser des micro-miroirs spheriques sur l'une des faces du microlaser, afin que la cavite soit geometriquement stable en l'absence d'echauffement du a la pompe. Nous avons ainsi etudie deux methodes de fabrication collective de microlentilles, methodes issues de technologies utilisees en micro-electronique. Des preformes spheriques sont tout d'abord realisees en resine photosensible a la surface du materiau actif, soit par fusion de cylindres de resine, soit par insolation variable de celle-ci a travers un masque a densites variables. Nous avons ensuite transfere ces formes dans le materiau d'interet, par gravure simultanee de la resine et du substrat. Apres depot de miroirs dielectriques, des centaines de microlasers a cavite stable sont obtenus sur une plaque. L'etude du fonctionnement laser (seuil, rendement, divergence) de microlasers continus ou declenches passivement par absorbant saturable a pu etre menee dans le cas d'un pompage par un laser saphir-titane. Le seuil obtenu avec les microlasers a cavite stable est reduit d'un facteur 5 a 20 par rapport aux microlasers plan-plans. Nous avons egalement montre et prouve experimentalement que les effets thermiques dans de telles cavites stables sont negligeables, et que le mode gaussien fondamental de la cavite est effectivement impose par la geometrie de celle-ci
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Deceuster, Andrew Isaac. "Investigation of Joining Micro-Foil Materials with Selective Laser Sintering and Laser Powder Deposition." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/434.
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Continuous and pulse selective laser sintering and laser powder deposition were used to find a solution to the manufacturing of micro-foil lattice structured components. A full factorial test matrix was used for each process to determine the processes capability to produce continuous tracks for joining the micro-foil materials. The samples were evaluated for dimensional profiles, distortion, and cycle times, to develop selection criteria for implementation of the processes into industry. The selective laser sintering processes were able to join the micro-foil materials into lattice structures with continuous tracks. The laser powder deposition processes were not able to properly join the micro-foil materials into lattice structures. The end results showed that micro-foil lattice structures can be produced using continuous and pulse selective laser sintering.
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Pruneau, Godmaire Xavier. "Micro-usinage de fibres optiques avec un laser CO2." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/26911/26911.pdf.
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Hélie, David. "Micro-usinage de lamelles de verre au laser femtoseconde." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28184/28184.pdf.
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Otanocha, Omonigho. "Laser surface micro/nano patterning for improving aerodynamic performance." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/laser-surface-micronano-patterning-for-improving-aerodynamic-performance(f78b8df4-fa5d-4dd8-9d93-88e1068c5857).html.
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The use of ultrafast lasers in material surface engineering has gained pre-eminence in recent years. This is due to optimal utility arising from their versatility, better process control, repeatability and high precision fabrication, without need for post processing. Reported in this thesis are experimental results on the use of picosecond laser to produce micro-patterns on cyclone components and their effects on flow characteristics. Results show that micro- dimples achieved reduction in dust accumulation within a multi-cyclone system considered, up to 78%. These micro-dimples when applied on the cyclone roof effected a 3% reduction in inlet velocity and 5% reduction on the dynamic pressure across the cyclone, without dust introduction. Results support the possibility for energy savings, without compromise on cyclone overall separation efficiency. Findings further demonstrated the effects of micro-riblets on cyclonic airflow at the wall boundary. Research outcomes supported the view that surface roughness of the cyclone roof could contribute on its dust separation capacity. Injection moulding was used to produce bumps on ABS plastic materials utilising picosecond laser machined micro-dimples on H13 tool steel. A statistical model detailing the interactions between the critical factors involved with picosecond laser interaction with H13 for micro-patterning was proposed. Critical factors identified were laser fluence, scanning speed and number of laser scans. In addition, results demonstrated the suitability of predicting depth of 40 - 100 µm for H13 tool steel, with 96% accuracy. The findings in this research could be explored to develop embedded micro/nano-wires within riblets through injection moulding, to effect electrically biased charging within the internal walls of a cyclone to aid dust separation processes.
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Hivin, Quentin. "Micro-structuration laser pour le packaging électro-optique avancé." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I031/document.
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Le développement de l’internet des objets et des services de vidéo en temps réel (streaming) a conduit à une augmentation continue du trafic des données au sein des data-centers. Celui-ci devrait être multiplié par trois entre 2012 et 2020 pour atteindre 15.3 zettaoctets/an. Cette évolution appelle parallèlement à un accroissement des performances des composants télécom en transmission optique monomode dont le standard s’établit aujourd’hui à 100-200 Gbits/s pour évoluer vers 400-800 Gbits/s dans un futur proche. Bien que les cœurs de technologies semiconducteurs soient aujourd’hui disponibles pour répondre à cette demande, les coûts élevés d’assemblage des puces électroniques (EIC) et photoniques (PIC) ainsi que l’alignement avec les fibres optiques monomodes limitent la pénétration de cette solution technologique sur le marché. Afin de relever ce défi, une structure originale d’interposeur en verre a été proposée dans le cadre du laboratoire commun IEMN-STMicroelectronics. Ce substrat d’assemblage en verre présente des avantages distinctifs majeurs tels que i) l'alignement passif de la fibre externe, ii) l'alignement optique passif du PIC sur l'interposeur, iii) le transfert des fonctions optiques passives du PIC sur l'interposeur de verre et iv) une approche conservative réutilisant les coupleurs à réseau du PIC.Le contexte du packaging électro-optique étant posé, ce travail de thèse s’est concentré sur la fonctionnalisation de substrats de verre par photo-inscription ou micro-usinage laser en régime femtoseconde afin de structurer les guides d’onde optique, les miroirs de redirection du faisceau guidé et la couche de redistribution électrique en cuivre. En premier lieu, des guides optiques monomodes à 1310 nm de bonne qualité ont été obtenus et caractérisés, permettant une mise en évidence franche des effets d’absorption non linéaire, d’auto-focalisation et de filamentation. Une étude expérimentale complète a permis de déterminer les paramètres d’exposition laser et de gravure chimique pour la fabrication de miroirs photoniques. Enfin, une méthode originale de structuration des interconnexions basée sur le fractionnement et le décollement de la couche de cuivre par effet thermo-mécanique a été développéeThe development of the Internet of Things and video streaming services is leadng to a continuous increase in data traffic within data-centers that is expected to increase threefold between 2012 and 2020 reaching 15.3 zettabytes/year. This evolution calls for an increase in performance of telecom components in optical single mode transmission, the standard of which is now 100-200 Gbits/s and will evolve towards 400-800 Gbits/s in the near future. Although the semiconductor technology cores are now available to meet this demand, the high assembly costs of electronic (EIC) and photonic (PIC) integrated circuits as well as the alignment with single-mode optical fibers limit the market penetration of this technological solution. In order to meet the challenge, an original glass interposer structure has been proposed in the framework of the IEMN-STMicroelectronics common laboratory. This glass assembly substrate holds major distinctive advantages such as i) passive alignment of the external fiber, ii) passive optical alignment of the PIC on the interposer, iii) transfer of the passive optical functions of the PIC onto the glass interposer and iv) a conservative approach reusing the PIC grating couplers.With this context associated to electro-optical packaging in mind, this thesis has focused on the functionalization of glass substrates by photo-inscription or laser micromachining in femtosecond regime in order to structure optical waveguides, redirection mirrors and copper electrical redistribution layer. First, good quality 1310 nm single-mode optical guides were obtained and characterized, allowing a clear demonstration of the effects of non-linear absorption, self-focusing and filamentation. A complete experimental study determined the laser exposure and chemical etching parameters for the manufacture of photonic mirrors. Finally, an original method for structuring interconnections based on the fractionation and detachment of the copper layer by thermo-mechanical effect has been developed
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Pruneau, Godmaire Xavier. "Micro-usinage de fibres optiques avec un laser CO₂." Master's thesis, Université Laval, 2011. http://hdl.handle.net/20.500.11794/23028.
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Le mandat initial de ce projet de maîtrise visait l'élaboration de procédures de microusinage de fibres optiques à l'aide d'un laser C0₂ puisé. L'efficacité d'usinage d'une fibre optique a d'abord été mise en évidence via l'étude théorique des phénomènes engendrés par l'absorption du rayonnement infrarouge. Suite à une caractérisation spatiale et temporelle du système laser, des méthodes sans contact de dégainage, de clivage et de polissage ont été mises sur pied en exploitant les propriétés uniques du rayonnement à 10,6/xm. Des fibres optiques de silice, de ZBLAN et de verre de chalcogénure ont toutes trois été soumises à ces procédures de micro-usinage. En définitive, l'étude de l'interaction entre un laser CO₂ et des réseaux de Bragg a permis de mettre en lumière quelques applications intéressantes.
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Griffiths, Jonathan. "Modelling of laser forming at macro and micro scales." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/9633/.
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Laser forming (LF) offers industry the promise of controlled shaping of metallic and nonmetallic components in prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfil this promise in a manufacturing environment the process must have a high degree of controllability, which can be achieved through a better understanding of its underlying mechanisms. The work presented in this thesis is primarily concerned with the use of modelling of the LF process at macro and micro scales as a means of process development. At the macro scale, finite element (FE), finite difference (FD) and analytical modelling were used to gain a better understanding of the complex interrelation between the various process parameters for specific geometries, reducing the need for extensive empirical investigations. A particular focus of the investigation was ascertaining which of these parameters influenced the fall off in bend angle per pass in multiple pass LF, along with the magnitude of their influence. The development of a full thermal-mechanical model of the LF process is detailed, as well as its application in a feasibility study into the forming of square section mild steel tubes for the automotive industry. Using this model, experimental observations were rationalized and novel scan strategies were developed which optimized the efficiency and accuracy of the process, something hitherto not possible using empirical methods alone. At the micro-scale, FE modelling was used to determine the mechanism of deformation in a novel laser micro-forming (LμF) technique, in conjunction with a full empirical study. The technique combined short pulse durations (20 ps) with high repetition rates (500 kHz) to generate localized heat build-up on the top surface of micro-scale stainless steel components, allowing for controlled and repeatable micro-adjustment. Modelling results suggest the mechanism works by confining the heating effect to the surface of the material, thereby selectively inducing thermal stresses and avoiding thermal damage of the component.
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Allegre, Olivier. "Advanced polarization control for optimizing ultrafast laser micro-processing." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/11793/.
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The ability to control and manipulate the state of polarization of a laser beam is becoming an increasingly desirable feature in a number of industrial laser micro-processing applications. Being able to control polarization would enable the improvement of the efficiency and quality of processes such as the drilling of holes for fuel-injection nozzles, the processing of silicon wafers or the machining of medical stent devices. This thesis presents novel, liquid-crystal-based optical setups for controlling the polarization of ultrafast laser beams, and demonstrates how such optical setups can be used to improve laser micro-processing efficiency and quality. Two experimental strategies were followed: the first used dynamic control of the polarization direction of a linearly polarized beam; the second generated beams with complex polarization structures. Novel optical analysis methods were used to map the polarization structures in the focal region of these laser micro-processing setups, using Laser Induced Periodic Surface Structures (LIPSS) produced on stainless steel sample surfaces at low laser fluence (around 1.5J/cm²), close to the ablation threshold of steel (i.e. 0.16J/cm²). This helped to characterize and calibrate the optical setups used in this thesis. The first experimental method used a fast-response, analogue, liquid-crystal polarization rotation device to dynamically control the direction of linear polarization of a laser beam during micro-processing. Thanks to its flexibility, the polarization rotator could be set-up in various synchronized configurations, for example keeping the polarization direction constantly perpendicular to the beam scanning motion. Drilling and cutting tests were performed on thin (~0.4mm thick) stainless steel sheets using a 775nm femtosecond laser at 24J/cm². The experimental results showed a consistent improvement in the micro-processing quality when the polarization direction was synchronized with the beam scanning motion. The sidewall surface roughness and edge quality of the machined structures were improved significantly, with the dimensions of ripples and distortions divided by a factor of two. The overall processing efficiency was also increased compared to that produced by linear or circular polarizations. The second experimental method used a digital, Liquid-Crystal On Silicon (LCOS) Spatial Light Modulator (SLM) to generate polarization structures with a cylindrical geometry, or Cylindrical Vector Beams (CVBs). A Jones matrix analysis was used to model the optical setup and predict the ability to produce CVBs in this way. The setup was implemented in a 775nm femtosecond laser micro-processing bench and the resulting polarization analyzed with a polarizing filter, demonstrating a polarization purity better than 84%. The amplitude and polarization properties in the focal region of the setup were studied using LIPSS produced on the surface of stainless steel samples at low fluence (1.5J/cm²), to check that the expected state of polarization had been achieved. An analytical model of the experimental setup was developed to explain the experimental results. The model predictions were in agreement with the experimental results and clarified how the polarization and phase structures affect the focal properties of the produced laser beams. Various types of CVBs were used with a high laser beam fluence (24J/cm²) for micro-machining 0.2-0.4mm thick stainless steel plates. A comparative analysis of micro-machining with radially, azimuthally, circularly and linearly polarized beams was carried out. It was shown that a radially polarized beam was more efficient at drilling and cutting high-aspect-ratio features when the plate thickness was above 0.2mm. The gain in processing speed was better than 5% compared with a circularly polarized beam and better than 10% compared with an azimuthally polarized beam, under the chosen processing parameters. However the processing speed was similar for all these polarization states (radial, azimuthal and circular) when machining 0.2mm thick plates. It was also shown that a radially polarized beam improved the processing quality, reducing the distortions affecting the edge quality of the machined structures.
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Alshehri, Ali. "Micro and Nanostructuring of Polymers by Femtosecond Laser Pulses." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35356.
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Micro/Nanostructuring of polymers by femtosecond pulses is of extreme importance because it drives applications in photonics and biomedicine. A femtosecond pulse, with an intensity of ∼ 10^13 W/cm^2, is capable of causing an optical breakdown and inducing permanent modification in the material. With such high intensity, and considering the fact that polymers possess high band gaps, the interaction nature is completely nonlinear, and the material can be modified locally on the surface and in bulk. The irradiated regions exhibit fluorescence, and they display new wetting properties as a consequence of the optical breakdown of a material. The optical breakdown can be investigated by studying the nonlinear absorption. In this thesis, we discuss the nonlinear absorption of fs-laser pulses inside polymers using transmission measurements. We show a step– function–like behaviour of the transmission, dropping abruptly to ∼ 20% at the optical breakdown threshold with a ∼ 40 % reduction in the band gap. Utilizing spectroscopy, we show that the laser-modified regions contain randomly distributed nanoclusters. The presence of localized nanoclusters is responsible for exhibiting fluorescence, within ∼ 10 µm3 for a single pulse. This feature was exploited to demonstrate high-density data storage in Polymethyl methacrylate (PMMA) without any special material preparation. We demonstrate up to 20 layers of embedded data that can be stored in a standard 120 mm disc. Storage capacity of 0.2 TBytes/disc can be achieved by adjusting read laser parameters. Besides the fluorescence capability induced in the bulk of polymers, the hydrophilicity shown by the fs–laser modified surface is utilized to study selective cell growth on the micro-structured Polydimethylsiloxane (PDMS) surface. We show that the C2C12 cells and rabbit anti-mouse protein attach preferentially to the modified regions when the surface is modified with low pulse energies. However, in the high pulse energy regime, the laser-modified regions exhibit superhydrophobicity inhibiting cell adhesion.
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Bruneel, David. "Ablation laser femtoseconde pour le contrôle de la micro et nano structuration." Phd thesis, Université Jean Monnet - Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00675144.
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Le développement actuel de la technologie induit une constante nécessité d'obtenir des tailles de plus en plus petites pouvant descendre jusqu'à des dimensions micrométriques et sub -micrométriques. L'ablation laser, qui a le grand avantage d'un enlèvement de matière très précis, est un candidat prometteur. Dans cette thèse on démontre la faisabilité de tirer avantage des impulsions laser femtosecondes avec la matière pour la micro et nano structuration, et ceci en ayant développé une machine compacte de grande précision et flexibilité. Une approche théorique comparant les régimes d'interaction à haute et basse cadence est présentée. Des investigations de l'efficacité du temps de procédé aussi bien que l'effet de la cadence pendant l'ablation de métaux ont été effectuées. Le potentiel de l'outil multifonctionnel couplé avec un oscillateur laser femtoseconde à haute cadence est montré pour différentes applications en biotechnologie. Les résultats sur la cartographie d'une large zone aussi bien que la nano découpe de précision de tissus biologiques et de matériaux variés sont présentés. Cet outil polyvalent couvre de larges domaines de recherche de la nano découpe d'échantillons biologiques aussi bien que la nanostructuration de différents types de matériaux. C'est d'un grand intérêt pour de nombreuses applications en science des matériaux, nanobiotechnologie et nanomédecine
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Matras, Guillaume. "Développement d'un amplificateur laser titane Saphir 10 kHz : application au micro-usage." Saint-Etienne, 2008. http://www.theses.fr/2008STET4008.
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Ce mémoire présente les résultats de travaux de thèse menés dans le cadre d'une convention CIFRE en collaboration avec la laboratoire Hubert Curien à Saint-Etienne et la société Thales Laser à Orsay. L'objectif principal de ces travaux était la réalisation d'un système amplificateur femtoseconde à base de cristal de saphir dopé titane cadencé à un taux de répétition de 10 kHz répondant au besoin industriel dans le domaine du micro-usinage laser. Des études préalables, à la fois théoriques et expérimentales, ont permis de caractériser avec précision la lentille thermique induite dans un cristal refroidi par eau fortement pompé sur un faible diamètre. Une cavité amplificatrice régénérative adaptée a pu alors être conçue. Des impulsions d'énergie relativement élevée ont pu être extraites de cette cavité. L'utilisation d'un deuxième étage amplificateur double-passage a permis d'augmenter significativement cette énergie. L'intérêt de cette source a été validé à travers des applications de micro-usinage. Le but de ces expérimentations était de démontrer le maintien du taux d'ablation et de la qualité d'usinage dans les métaux et acier tels que l'inox 316L, le tantale, le cuivre, le nickel et encore l'aluminium, lorsqu'on augmente le taux de répétition dans une plage de fluence centrée autour de la fluence optimale définie dans ce mémoire. Dans des conditions proches des conditions industrielles, des séries de fentes ont été usinées à différentes fluences et différentes cadences : 1, 5, 10 et 15 kHz. Leurs profondeurs ont été mesurées au profilomètre optique afin d'en déduire le taux d'ablation. Elles ont été également observées au MEB pour comparer la qualité d'usinage. Les résultats n'ont pas montré de baise de taux d'ablation et de dégradation de la qualité d'usinage quand la cadence augmente de 1 à 15 kHz validant ainsi l'intérêt de la source femtoseconde 10 kHz développée
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Hélie, David. "Développement de procédés de micro-usinage de matériaux optiques au laser femtoseconde." Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25446.
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Lors des travaux de recherche décrits dans cette thèse, un laser à impulsions femtosecondes (fs) est employé comme outil chirurgical pour joindre/souder les matériaux optiques. Lorsque ces impulsions traversent un premier matériau transparent (typiquement un verre) et sont focalisées à l’interface entre celui-ci et un deuxième matériau, l’ionisation non linéaire de la matière produit une soudure localisée à la région irradiée sans affecter thermiquement les environs. Le deuxième matériau peut être de composition soit identique ou différente du premier, soit transparent ou opaque. Les surfaces à joindre devant être préalablement mises en contact optique, nous avons donc pratiqué la technique du collage optique pour éliminer l’écart entre elles. Cette technique consiste à utiliser des matériaux avec une qualité de surface exemplaire de façon à établir un contact optique lors de leur rapprochement qui couvre idéalement l’aire totale entre les surfaces. De cette façon, les matériaux sont préjoints par de faibles liaisons moléculaires de type Van der Waals avant l’inscription de la soudure. Il est coutumier de renforcer cette jonction par un recuit thermique, ce qui est inapplicable sur les assemblages de matériaux différents puisque la dilatation thermique inégale va induire le décollement du contact optique. Nous avons donc proposé la soudure laser fs pour la renforcer. Puisqu’aucun chauffage macroscopique des échantillons n’est induit, cette technique est applicable aux combinaisons de matériaux identiques et différents. Le renforcement se fait par l’inscription d’une multitude de lignes de soudure en périphérie de la zone en contact optique suivant un patron soit rectangulaire ou circulaire. La partie scellée définit une fenêtre de transmission optique dont la transparence est conservée. Les lignes de soudure en périphérie de cette fenêtre la protègent contre le décollement du contact optique induit par des contraintes mécaniques et/ou thermiques. Ce procédé a été adapté à deux applications tirant profit des avantages susmentionnées. Dans un premier temps, un endcap microscopique en verre fut soudé sur des fibres optiques ordinaires et microstructurées. Subséquemment, un laser à disque a été joint à un dissipateur de chaleur en silicium. Ces deux applications démontrent la versatilité et le potentiel de miniaturisation de ce procédé original combinant la soudure laser femtoseconde et le collage optique.Within the research described in this thesis, femtosecond (fs) laser pulses are utilized as a surgical tool to join optical materials. When these sub 100 fs pulses are transmitted through a first material (typically glass) and focussed at the interface between the first and second materials, the nonlinear ionization of matter will generate a weld localized solely inside the irradiated region without thermally affecting its surroundings. The second material may be of identical or different composition to that of the first, either transparent or opaque. The joining surfaces must be put in optical contact beforehand, so we used the direct bonding technique to eliminate any pending gap between them. This technique consists in using materials with very flat polished surfaces so as to induce optical contact ideally throughout the whole area between the bonding surfaces. The materials will thus be prebonded by Van der Waals forces prior to welding. It is customary to reinforce the direct bond by thermal annealing, which is however unpractical for dissimilar material combinations since the uneven thermal dilatation will lift-off the optical contact. We propose the use of fs laser welding as an alternative to thermal annealing to reinforce such assemblies. Since no macroscopic heating is induced, this technique is applicable to both similar and dissimilar material combinations. Reinforcement is produced by the inscription of multiple weld lines at the periphery of the direct bonded area in a closed shape pattern. The region sealed by the weld seams defines an optical transmission window where the optical transparency of the assembly is maintained. The weld lines at the periphery protect this window against lift-off of optical contact initiated by mechanical and/or thermal constraints. This process was adapted to two specific applications which greatly profit from the aforementioned benefits. Firstly, a microscopic endcap made of glass was welded to the polished tip of regular and microstructured optical fibers. Subsequently, a crystal disc acting as a laser medium was joined to a semi-conductor heat sink. These applications demonstrate the great versatility and miniaturisation potential of the novel joining process developed during this doctorate, which combines fs laser welding and direct bonding.
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Verit, Isabel. "Micro-Usinage par laser femtoseconde : Fabrication d'une microfibre glomérulaire perfusée." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0159.
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Le nombre de patients en attente sur la liste de transplantation d'organe est croissant dû notamment à une augmentation de la durée de vie. L'ingénierie tissulaire, dans une optique de remplacement d'organes pourrait être une alternative à ce problème de pénurie d'organes. Cependant, la création d'un organe entier par ingénierie tissulaire est limitée par la complexité de son organisation et la vascularisation des tissus créés. La vascularisation permet en effet d’apporter l'oxygène et les nutriments nécessaires aux cellules et d'éliminer les déchets qu'elles génèrent. Sans vascularisation, les cellules ne peuvent survivre et nécrosent.Ce projet de thèse est un partenariat entre le laboratoire français BioTis - INSERM U1026 et le centre technologique d'optique et laser ALPhANOV autour de la bio-ingénierie tissulaire. L'objectif est de développer un procédé de fabrication et d'usinage pour créer un modèle de microfibres glomérulaires perfusables. Des microfibres cellulaires ont été réalisées au sein du laboratoire BioTis. Elles sont composées d’un cœur d’hydrogel de collagène et d’une paroi externe bicellulaire modélisant la barrière de filtration rénale. L’originalité de ce travail repose ensuite sur la création d’une lumière interne, à l’aide d’un faisceau laser à impulsions ultracourtes. Inspiré des procédés industriels d’usinages intravolumiques de matériaux transparents, les impulsions ultracourtes sont ici fortement focalisées dans le cœur de collagène pour créer un canal intravolumique via un phénomène de cavitation à l’intérieur des fibres sans impacter la couche externe de cellulesThe demand for organ transplantation has rapidly increased during the past decades due to the increased incidence of vital organ failure and the greater improvement in post-transplant outcome. However, the unavailability of adequate organs for transplantation to meet the existing demand has resulted in major organ shortage crisis. Today, the emergence of regenerative medicine and more particularly, tissue engineering, appears as the best opportunity to effectively regenerate functional tissues and organs. However, these approaches face the 3D architectural complexity of a real organ’s system. More particularly, one of the most challenging issues when engineering tissues is the lack of an efficient method to produce blood vessel systems — the vascularization. Without nutrients and oxygen supply, cells die, and engineered tissues show cell necrosis.This project is a collaboration between the French laboratory of tissue engineering BioTis – INSERM U1026 and the technological centre in optics and lasers ALPhANOV. The aim of this project is to develop a model of perfusable glomerular microcapillary that would mimic glomerular filtration. Microfibres was crafted in the BioTis lab with a core made of collagen hydrogel and a peripheric cell bilayer. This thesis focuses on the creation of a channel within the collagen core using femtosecond laser processing. Following the principle of industrialized intra-volume laser microprocessing of transparent materials, ultra-short laser pulses were strongly focused inside collagen hydrogel to induce the formation of a channel through cavitation phenomena without affecting the cell bilayer
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SILVA, Renato Barbosa da. "Materiais Micro e Nanoestruturados para Aplicações Fotônicas." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17328.
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Diferentes tipos de materiais foram abordados nesta tese visando sua possível aplicação na fotônica. Por isso, o texto foi dividido em duas partes. A Parte 1 trata da preparação de materiais para a aplicação em laser aleatório. O primeiro material sintetizado foram as nanocascas metálicas, cuja estrutura é formada por um caroço de sílica com uma casca metálica ao seu redor. Assim, foi descrito um procedimento experimental melhorado com o intuito de se obter nanocascas de ouro e de prata de maneira mais reprodutível no menor tempo possível. Neste experimento, foi demostrado que a taxa de agitação no final da síntese tem importante influência na formação ou não das nanocascas metálicas. O crescimento de nanocascas de ouro e prata ocorria para taxas de 190 rpm e 1500 rpm respectivamente. O segundo material consistiu de partículas sub-micrométricas de sílica com corante rodamina 640 encapsulado. O encapsulamento ocorreu pela simples adição de uma solução do corante durante a síntese das partículas de sílica. Assim, para uma concentração de corante de 10-2 M, foi descrito um experimento de laser aleatório bicromático. Ao contrário de outros trabalhos na literatura foi possível controlar a emissão do laser aleatório apenas mudando a intensidade de excitação. Durante estes experimentos também foi verificada a existência de frequency-pulling entre dímeros e monômeros nos experimentos. Finalmente na Parte 2 é discutida a síntese e caracterização de nanocristais de silício (ncSi). Os ncSi apresentam luminescência cujo comprimento de onda pode ser controlado variando o tamanho dos nanocristais. A síntese foi baseada no processamento termal em altas temperaturas do hidrossilicato HSiO1.5, derivado do triclorossilano (HSiCl3). Em seguida, os vidros são finamente macerados num almofariz e pistilo de ágata antes dos ncSi serem extraídos via extração ácida. Neste experimento o objetivo foi obter nanocristais de silício monodispersos sem a utilização de etapas pós-síntese como a ultracentrifugação. O objetivo foi alcançado adicionando cloreto de sódio (NaCl) durante a etapa maceração, com o intuito de diminuir o tamanho dos grãos e garantir uma extração uniforme dos mesmos
Different materials were reported in this thesis aiming their possible photonic applications. Therefore the content of this thesis was distributed in two parts. Part 1 is related to the synthesis of materials for applications in random laser. The first material synthesized were the metallic nanoshells, which structure is based in a silica core and a metallic shell around it. An improved experimental method was reported for synthesize gold and silver nanoshells in order to guarantee the reproducibility and decrease the time necessary for synthesis. It was shown that the stirring rate at the end of synthesis plays an important role on the growth of metallic nanoshells. The growth of gold nanoshells was performed using a stirring rate of 190 rpm, on the other hand, the growth of silver nanoshells was performed using a stirring rate of 1500 rpm. The second material consisted of sub-micrometer silica particles whith encapsulated rhodamine 640. The encapsulation was made by the simple addition of a dye solution to do during a Synthesis of silica particles. An bichromatic random laser was operated using a concentration of 10-2 M of laser dye. Unlike other works in the literature it was possible to control the emission of the random laser only changing the intensity of the excitation source. These experiments were also revealed the possibility of frequency-pulling between dimers and monomers of rhodamine through the shift of the laser emission. Finally, in Part 2 it is discussed the synthesis and characterization of silicon nanocrystals (ncSi). The ncSi present luminescence that can be tunable by changing the ncSi sizes The synthesis was based on the thermal processing at high temperatures of HSiO1.5 hydrosilicate derivative of trichlorosilane (HSiCl3). Then, the glasses are finely grounded in a agate mortar and pestle before been extracted via an acid etching. In this experiment the objective was to obtain monodisperse nanocrystals of silicon without the use of post-synthesis steps such as ultracentrifugation. The objective was reached added sodium chloride (NaCl) during the ground step in order to decrease the size of grain for to obtain a uniform etching.
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Wagner, Frank. "Interaction laser matière à forts flux : Micro-usinage et endommagement laser dans le domaine nanoseconde." Habilitation à diriger des recherches, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00769459.
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Ce document décrit mon cheminement professionnel, en détaillant principalement mes activités de recherche successives qui, par delà les changements de pays et de thématiques précises, ont gardé le dénominateur commun " d'interaction lumière-matière ". Ce document débute par un curriculum vitae (section 1) qui résume les différentes étapes de mon cheminement professionnel (" Diplomarbeit " au Laser-Laboratorium Göttingen, Doctorat à l'Ecole Polytechnique Fédérale de Lausanne, Recherche dans une PME à Lausanne, Maître de Conférence à l'Université d'Aix-Marseille / Institut Fresnel) en précisant les responsabilités que j'ai assumées. Suit la liste de mes travaux (section 2), puis la liste des personnes dont j'ai encadré le travail (section 3). La section suivante résume mes activités d'enseignement (section 4). Le mémoire se termine ensuite avec le résumé de mes activités de recherche dans les deux dernières positions que j'ai occupées (section 5) et se conclut par une esquisse de mon projet scientifique (section 6) tel que je le perçois aujourd'hui. En annexe, j'ai finalement attaché les copies de quelques publications significatives sur différents aspects de mon travail.
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Li, Kun. "Laser micro-processing of silicon using nanosecond pulse shaped fibre laser at 1 μm wavelength." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/245313.
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Processing of Si in the semiconductor and solar cell industry has been dominated by the Diode Pumped Solid State (DPSS) Ultraviolet (UV) laser. Recent advances in laser source technology have produced fibre lasers with Master Oscillator Power Amplifier (MOPA) architectures that offer high repetition rates, high operational efficiencies, and pulse modulation controls exceeding those of typical Q-switched DPSS lasers. The aim of this research is to investigate 1 μm fibre laser machining of Si with a view to identifying the influential laser parameters for optimum processing of high quality, high efficiency micro drilling and surface texturing applications. A secondary aim is to develop a greater understanding of the laser material interactions and material removal mechanism when using fast rise-time nanosecond laser pulse envelopes. The IR fibre laser was able to perform percussion drilling and single pulse machining on the polished Si over a range of intensities up to 1.22 GW/cm2. With the optimum parameters, the micro-sized holes generated by the IR laser have a well defined edge, no heavy recast and no cracks. With a pulse shape of fast rise time (<7.5 ns for a 10-90% rise in signal), a high front peak power zone (approaching 14 kW) and an energetic long tail (40-180 ns), the absorption coefficient of Si at IR wavelength increased dramatically with time and temperature due to the fact that the liquid Si has a metal like absorption behavior. As a result, Si was quickly melted and the rest of pulse energy was able to remove the liquid Si effectively. The machining process left a limited amount of resolidified melt droplets and vapor condensates, which could be washed off ultrasonically. The drilling process was energy efficient when melt expulsion dominated the machining mechanism (0.08-0.2 mJ pulse energy depending on the pulse durations). The low energy pulse (~0.2 mJ) can achieve similar depth as the high energy pulse (~0.7 mJ), so high repetition rates of 100 kHz can be used to instead of 25 kHz, resulted in high processing speed. In addition, by comparing the single pulse machining with the state of the art UV laser, the IR fibre laser machined deeper features and better surface finish in the pulse energy region of >0.07 mJ. With the pulse shaping capability, the material properties can be varied and the wavelength factor can be minimized. The results suggest that applications like microvia drilling can now be carried out with the more flexible and low cost IR fibre laser. The increased repetition rates of fibre laser can increase production speed to satisfy the needs of drilling ~10 thousands holes per second, required by the modern semiconductor and solar cell production. The shortened optical penetration length of 1 μm wavelength laser on Si with increasing temperature and sufficient thermal diffusion length resulted from the asymmetrical fibre laser pulse and the dynamic properties of Si produced a thick liquid layer. A one-dimensional heat conduction model based on the surface heating source predicted that this superheated liquid layer was able to stay above 4706 K (0.905 times the thermal critical temperature 5200 K of Si) for longer than 70 ns to induce explosive boiling. This proposed material removal mechanism was also confirmed by the shadowgraph images, showing particulates ejection lasting up to ten microseconds after the laser pulse. The estimated hole depth based on the explosive boiling alone were different from the measured ones at varying peak power densities (<1.22 GW/cm2) but fixed pulse duration (200 ns), since Si was removed by a mixture of mechanisms. With varying pulse durations (40-200 ns) but fixed peak power density (~0.63 GW/cm2), the estimated depth based on the explosive boiling was in close agreement with the measured ones (6% difference on average). The SEM images at this power density showed a micron- /submicron-sized debris field, which was also observed with the explosive boiling in the past. Although the improved quality of Si machining was demonstrated with the 1 μm MOPA based fibre laser, the setup of this system was only applicable to surface texturing, blind holes and through holes of less than 100 μm in depth. Further research is required to demonstrate the capability of more energetic pulse with higher peak power and large pulse duration range to explore more machining options.
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Ten, Jyi Sheuan. "High speed mask-less laser-controlled precision micro-additive manufacture." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/285409.
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A rapid, mask-less deposition technique for writing metal tracks has been developed. The technique was based on laser-induced chemical vapour deposition. The novelty in the technique was the usage of pulsed ultrafast lasers instead of continuous wave lasers in pyrolytic dissociation of the chemical precursor. The motivation of the study was that (1) ultrafast laser pulses have smaller heat affected zones thus the deposition resolution would be higher, (2) the ultrashort pulses are absorbed in most materials (including those transparent to the continuous wave light at the same wavelength) thus the deposition would be compatible with a large range of materials, and (3) the development of higher frequency repetition rate ultrafast lasers would enable higher deposition rates. A deposition system was set-up for the study to investigate the ultrafast laser deposition of tungsten from tungsten hexacarbonyl chemical vapour precursors. A 405 nm laser diode was used for continuous wave deposition experiments that were optimized to achieve the lowest track resistivity. These results were used for comparison with the ultrafast laser track deposition. The usage of the 405 nm laser diode was itself novel and beneficial due to the low capital and running cost, high wall plug efficiency, high device lifetime, and shallower optical penetration depth in silicon substrates compared to green argon ion lasers which were commonly used by other investigators. The lowest as-deposited track resistivity achieved in the continuous wave laser experiments on silicon dioxide coated silicon was 93±27 µΩ cm (16.6 times bulk tungsten resistivity). This deposition was done with a laser output power of 350 mW, scan speed of 10 µm/s, deposition pressure of 0.5 mBar, substrate temperature of 100 °C and laser spot size of approximately 7 µm. The laser power, scan speed, deposition pressure and substrate temperature were all optimized in this study. By annealing the deposited track with hydrogen at 650 °C for 30 mins, removal of the deposition outside the laser spot was achieved and the overall track resistivity dropped to 66±7 µΩ cm (11.7 times bulk tungsten resistivity). For ultrafast laser deposition of tungsten, spot dwell experiments showed that a thin film of tungsten was first deposited followed by quasi-periodic structures perpendicular to the linear polarization of the laser beam. The wavelength of the periodic structures was approximately half the laser wavelength (λ/2) and was thought to be formed due to interference between the incident laser and scattered surface waves similar to that in laser-induced surface periodic structures. Deposition of the quasi-periodic structures was possible on stainless steel, silicon dioxide coated silicon wafers, borosilicate glass and polyimide films. The thin-films were deposited when the laser was scanned at higher laser speeds such that the number of pulses per spot was lower (η≤11,000) and using a larger focal spot diameter of 33 µm. The lowest track resistivity for the thin-film tracks on silicon dioxide coated silicon wafers was 37±4 µΩ cm (6.7 times bulk tungsten resistivity). This value was achieved without post-deposition annealing and was lower than the annealed track deposited using the continuous wave laser. The ultrafast tungsten thin-film direct write technique was tested for writing metal contacts to single layer graphene on silicon dioxide coated silicon substrates. Without the precursor, the exposure of the graphene to the laser at the deposition parameters damaged the graphene without removing it. This was evidenced by the increase in the Raman D peak of the exposed graphene compared to pristine. The damage threshold was estimated to be 53±7 mJ/cm2 for a scanning speed of 500 µm/s. The deposition threshold of thin-film tungsten on graphene at that speed was lower at 38±8 mJ/cm2. However, no graphene was found when the deposited thin-film tungsten was dissolved in 30 wt% H2O2 that was tested to have no effect on the graphene for the dissolution time of one hour. The graphene likely reacted with the deposited tungsten to form tungsten carbide which was reported to dissolve in H2O2. Tungsten carbide was also found on the tungsten tracks deposited on reduced graphene oxide samples. The contact resistance between tungsten and graphene was measured by both transfer length and four-point probe method with an average value of 4.3±0.4 kΩ µm. This value was higher than reported values using noble metals such as palladium (2.8±0.4 kΩ µm), but lower than reported values using other metals that creates carbides such as nickel (9.3±1.0 kΩ µm). This study opened many potential paths for future work. The main issue to address in the tungsten ultrafast deposition was the deposition outside the laser spot. This prevented uniform deposition in successive tracks close to one another. The ultrafast deposition technique also needs verification using other precursors to understand the precursor requirements for this process. An interesting future study would be a combination with a sulphur source for the direct write of tungsten disulphide, a transition metal dichalcogenide that has a two-dimensional structure similar to graphene. This material has a bandgap and is sought after for applications in high-end electronics, spintronics, optoelectronics, energy harvesting, flexible electronics, DNA sequencing and personalized medicine. Initial tests using sulphur micro-flakes on silicon and stainless-steel substrates exposed to the tungsten precursor and ultrafast laser pulses produced multilayer tungsten disulphide as verified in Raman measurements.
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Danion, Gwennaël. "Synthétiseur micro-onde à térahertz ultra-stable." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S014/document.
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Le but de cette thèse est la synthèse optique d'ondes millimétriques et submillimétriques avec un très bas bruit de phase. La première partie concerne la réalisation d'un laser biaxe bifréquence dont chacune des deux fréquences est accordable indépendamment et continûment sur 1 THz. Ce laser est caractérisé en bruit d'amplitude et de phase. Nous avons mis en évidence un facteur de couplage entre les fluctuations de puissance de la diode de pompe et le bruit de phase du laser. La deuxième partie concerne le développement d'un système amplificateur qui se compose d'un amplificateur EDFA et d'un SOA par polarisation. Ce système amplificateur permet d'obtenir une puissance de l'ordre de 17 dBm, tout en réduisant le bruit relatif d'intensité (RIN) d'une vingtaine de dB sur 1 GHz. Cet amplificateur est également un actionneur pour la stabilisation de puissance permettant un RIN de l'ordre de -150 dB/Hz de 3 Hz à 5 kHz. La dernière partie concerne la mise en place du banc cavité et de l'asservissement des fréquences du laser sur une cavité ultra-stable. Nous obtenons un bruit de phase, à 10 kHz pour une porteuse à 10 GHz, meilleur que le plancher de bruit d'un analyseur de bruit de phase hautes performances de l'ordre de -115 dBc/ Hz. Le bruit de phase du système est indépendant de la fréquence de battementThe aim of this thesis is the optical synthesis of millimeter and submillimeter waves with a very low phase noise. The first part concerns the development of a dual-axis dual frequency laser, whose the two frequencies are tuneable independently and continuously on 1 THz. This laser is characterized in amplitude noise and phase noise. We have identified a coupling factor between the diode pump and the power fluctuations of the laser phase noise. In the second part, we report the development of an amplifier system which consists of an EDFA and a SOA per polarisation axis. This amplifier system delivers 17 dBm of power and reduces the relative intensity noise (RIN) by 20 dB on a 1 GHz bandwidth. This amplifier is also an actuator for the power stabilization to a RIN of the order of -150 dB/Hz from 3 Hz to 5 kHz. The last part concerns the setup of the cavity bench and the stabilization of the laser frequency on a ultrastable cavity. We obtain a phase noise at 10 kHz of frequency offset on a 10 GHz carrier better than the noise floor of a phase noise analyser with high performance of the order of -115 dBc/Hz. The system phase noise is independent of the beatnote frequency
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Mota, Alessandro Damiani. "Sistema eletrônico de controle para laser amarelo de aplicação oftalmológica com regime de operação contínuo e micro-pulsado." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-26042012-100723/.
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Mais recentemente foi proposta uma nova técnica para tratamento de doenças relacionadas à retina humana, utilizando descargas laser na retina com seqüência de pulsos da ordem de 200 \'mü\'s, em substituição ao tratamento convencional que utiliza pulsos longos da ordem de 300 ms. A principal vantagem da nova técnica é a preservação (sem morte celular) do tecido exposto ao laser. Esse trabalho apresenta os mecanismos adotados para o desenvolvimento de um sistema eletrônico de controle de uma cavidade laser em 586 nm, para uso oftalmológico, que objetiva atender o protocolo exigido por essa técnica mais recente. O referido protocolo exige a formação de pulsos rápidos de laser, o que torna vital a velocidade do sistema eletrônico de controle da cavidade laser. Para atender os requisitos do projeto foram implementados dois controladores de corrente em malha fechada PI (Proporcional integrative controller) que trabalham em sincronismo, um controlador de potência óptica em malha fechada PI, e circuitos auxiliares de controle térmico da cavidade laser. Em software foram implementados um PI de potência, com objetivo de tornar a malha de controle estável com o tempo de resposta necessário, e o PI de controle térmico dos elementos da cavidade laser. Os testes realizados do protótipo demonstraram que o sistema de controle atendeu as especificações de projeto, principalmente no que se refere a tempo de resposta do pulso rápido, ponto fundamental na obtenção do protocolo clínico (FastPulse), que esse trabalho objetiva atender. Adicionalmente, o protótipo foi submetido a teste clínico em um paciente, e os resultados demonstraram eficácia no tratamento e ausência de marcas (lesões) na retina.Recently, scientists have proposed a new technique for treating diseases related to the human retina, which is based on retinal laser discharges using pulse sequence around of 200 \'mü\'s, replacing the conventional treatment using long pulses around of 300 ms. The main advantage of the new technique is the conservation (without cell death) of the area exposed to the laser. This work presents the mechanisms adopted for the development of an electronic control system of a laser cavity at 586 nm for ophthalmic use, which aims to meet the protocol required by this recent technique. The protocol requires the formation of rapid pulses of laser, which makes the electronic control system response velocity of the laser cavity vital to the protocol. To meet the project requirements were implemented two current controllers in closed loop PI (proportional integrative controller) working synchronized, an optical power controller in closed loop PI, and auxiliary circuits for temperature control of the laser cavity. Software were implemented for two controls, a PI power, in order to make the control loop stable with the required response time, and a PI thermal control for elements of the laser cavity. Tests showed that the prototype met the design specifications, especially regarding the response time of rapid pulse, key point in obtaining the clinical protocol (FastPulse), that this work aims to meet. Additionally, the prototype was subjected to clinical trial on a patient, and the results demonstrated efficacy and no visible lesions were noticed on retina.
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Pence, Chelsey Nicole. "Micro-bending and patterning via high energy pulse laser peening." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4714.
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High energy pulse laser peening (HEPLP) is a manufacturing process, in which a strong shock wave is produced and induces high pressures on the surface of the target material. Generally, this process is used to improve material properties such as the hardness and fatigue life. First a 2D multi-physics model for the process was investigated, which simulates the pressure induced on the surface of the target material. The model can be coupled with commercial finite element software, such as ABAQUS, to more accurately simulate the HEPLP process to find stresses and deformations on the surface. Next two novel applications using the HEPLP process were investigated.
The first, laser shock bending is a sheet metal micro-forming process using HEPLP to accurately bend, shape, precision align, or repair micro-components with bending angles less than 10°. Negative bending angle (away from laser beam) can be achieved with the high-energy pulsed laser, in addition to the conventional positive laser bending mechanism. In this thesis, various experimental and numerical studies on aluminum sheets were conducted to investigate the different deformation mechanisms, positive and negative. The experiments were conducted with the sheet thickness varying from 0.25 to 1.75 mm and laser pulse energy of 0.2 to 0.5 J. A critical thickness threshold of 0.7-0.88 mm was found that the transition of positive negative bending mechanism occurs. A statistic regression analysis was also developed to determine the bending angle as a function of laser process parameters for positive bending cases.
The second application studied used HEPLP to imprint complex two-dimensional (2D) patterns dental implant material of cpTi. Pure titanium (commercial pure cpTi) is an ideal dental implant material, without the leeching of toxic alloy elements. Evidence has shown that unsmooth implant surface topologies may contribute to the osteoblast differentiation in human mesenchymal pre-osteoblastic cells, which is helpful to avoid long-term peri-abutment inflammation issues for the dental implant therapy with transcutaneous devices. Studies have been conducted on the grit blasted, acid etched, or uni-directional grooved Ti surface, however, for these existing approaches the surface quality is difficult to control or may even damage the implant. The strong shock wave generated by HEPLP is used to press a stainless steel grid, used as a stamp, on Ti foils to imprint a 2D pattern. In this study, the multiple grid patterns and grid sizes were applied to test for cell-attachment improvements. Then, the cell culture tests were conducted with the patterned surface to investigate the contribution of these 2D patterns, with the control tests of the other existing implant surface topography forming approaches. The micro-patterns proved successful in increasing the cell-attachment, increasing the number of cells attaching to the material and also contributing to the cell-growth within the grooved areas.
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Dobrev, Todor. "Investigation of laser milling process characteristics for micro tooling applications." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56007/.
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Laser milling is a new application that is challenging for the power contained in the laser light. Due to its small unit of material removal, accuracy and repeatability, laser milling has found an application area in micro manufacturing, especially the manufacturing of microtools. There is a number of micro manufacturing and replication processes on the market at present. Their needs raise the requirements that have to be met by the microtool manufacturing process. Initially, the requirements of micro manufacturing processes, such as micro-injection moulding and hot-embossing, are identified and compared to what the laser milling process can achieve. An investigation is carried out to identify the capabilities of the laser milling process and match them to these requirements. The investigated process characteristics are surface finish, aspect ratio, accuracy and minimum feature size. Furthermore, as surface finish is identified to be a considerable constraint, an investigation is undertaken to improve the resulting surface finish obtained from the laser milling process. A two-dimensional theoretical model is developed to investigate the crater formation on a metal target by a microsecond laser pulse. The model takes into account the absorption of the laser light by the target, and simulates the heating and vaporisation of the material, including an adjustment to compensate for the change of state. A simple numerical technique is employed to describe the major physical processes taking part in the laser milling process. Experimental validation of the proposed model is provided for two common tooling materials. To investigate the formation of the material surface after laser milling, a complex 3D surface model is presented based on the single crater profiles of the 2D theoretical model together with a consideration for the overlapping of the craters. Additional factors, that are influential in the formation of the final material surface, are also considered and their effect on the surface roughness estimated. Finally, a number of techniques for reducing surface roughness are presented. Laser cleaning is a technique that utilises the de-focused laser beam to "smooth out" the material surface irregularities. The other three techniques are applied after laser milling, and are ultrasonic cleaning bath, chemical pickling and electro-chemical polishing.
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Guo, Wei. "Laser Micro/Nano Scale Surface Patterning by Particle Lens Array." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508543.
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Gill, Matthew. "Micro and nano structuring of metals using femtosecond laser ablation." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434009.
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Desbiens, Jean-Philippe. "Micro-usinage au laser excimère pour le prototypage de MEMS." [S.l. : s.n.], 2006.
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Ouyang, J. "Tailored optical vector fields for ultrashort-pulse laser micro-processing." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3001726/.
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In this thesis, a Spatial Light Modulator (SLM) and a nano-structured S-waveplate were integrated with a picosecond laser system and employed to generate complex vector optical fields. Precise tailoring of optical vector beams is demonstrated, shaping their focal electric fields. Using novel optical setups, radial and azimuthal polarizations with and without vortex phase wavefront were created, producing complex laser micro patterning on a polished metal surface. Imprinting Laser Induced Periodic Surface Structures(LIPSS) elucidates the detailed vector fields around the focal region, which shows clearly how the Orbital Angular Momentum(OAM) associated with a helical wavefront induces rotation of vector fields along the optical axis of a focusing lens. In addition, unique, variable logarithmic spiral micro-structures were imprinted on the metal surface. These are the first experimental observations of such micro-structured spirals created by multi-pulse exposure with spiral vector fields which are shown to be due to superpositions of plane wave radial and azimuthal polarizations. A comparative analysis of micro-drilling with radially, azimuthally, circularly and linearly polarized beams with various wavefront was also carried out. The results are compared in terms of quality and efficiency, illustrating how the distinct machining properties associated with each beam make it best suited for specific processes or materials. A radially polarized beam was considered as the most efficient at drilling high-aspect-ratio features. By applying an axicon phase map on the SLM, annular shaped laser beams with adjustable dimension were created and employed in semiconductor thin film selective removal, which enhanced processing speed to a new level. Furthermore, annular beams with radial and azimuthal polarization were generated, imprinting complex concentric ring LIPSS pattern on a polished stainless steel surface. Side white light illumination tests demonstrated distinguishable bright strips on these rings due to diffractive properties of LIPSS, which offers a novel way in variable information encoding technologies. Finally, synchronization of vector field polarizations with micro-positioning at a material surface was demonstrated, leading to potential industrial applications of this work.
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Lasagni, Andrés F., Tim Kunze, Matthias Bieda, Denise Günther, Anne Gärtner, Valentin Lang, Andreas Rank, and Teja Roch. "Large area micro-/nano-structuring using direct laser interference patterning." SPIE, 2016. https://tud.qucosa.de/id/qucosa%3A34803.
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Smart surfaces are a source of innovation in the 21^st Century. Potential applications can be found in a wide range of fields where improved optical, mechanical or biological properties can enhance the functions of products. In the last years, a method called Direct LaserInterference Patterning (DLIP) has demonstrated to be capable of fabricating a wide range of periodic surface patterns even with resolution at the nanometer and sub-micrometer scales. This article describes recent advances of the DLIP method to process 2D and 3D parts. Firstly, the possibility to fabricate periodic arrays on metallic substrates with sub-micrometer resolution is shown. After that, different concepts to process three dimensional parts are shown, including the use of Cartesian translational stages as well as an industrial robot arm. Finally, some application examples aredescribed.
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Itoh, Sho. "Studies on laser processing of glasses for micro- and nanostructures." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217174.
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Desbiens, Jean-Philippe. "Micro-usinage au laser excimère pour le prototypage de MEMS." Mémoire, Université de Sherbrooke, 2006. http://savoirs.usherbrooke.ca/handle/11143/1280.
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De plus en plus de dispositifs miniatures appelés MEMS (Micro Electro Mechanical systems) sont développés au Canada. Parmi ces dispositifs, on retrouve notamment des capteurs (pression, accélération, température, etc.), des micro-actionneurs (électrostatiques, piézoélectriques, etc.) et une panoplie d'autres applications possibles de la mécanique et de l'électronique à petite échelle (ex. micro-laboratoire, microturbine). Les MEMS sont généralement fabriqués par des procédés de microélectronique en salle blanche (lithographie, gravure humide, DRIE, etc.). Ces méthodes ne permettent de réaliser les MEMS que par empilement de structures 2D les unes sur les autres. Cependant, l'ablation au laser s'avère être une méthode de fabrication prometteuse afin de compléter ces dernières pour le prototypage de MEMS de taille microscopique (10 *m à 10 mm typiquement). Ce projet de recherche vise donc à développer un outil permettant de réaliser, par écriture directe, l'ablation des matériaux pour créer des structures 2D et possiblement 3D à l'aide d'un laser excimère ArF (193 nm) à cette échelle. Un poste de micro-usinage à commande numérique a donc été conçu sur mesure par le GAUS en collaboration avec l'Institut National d'Optique (INO)."--résumé abrégé par UMI.
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Farhana, Baset. "Micro/nano-scale Manipulation of Material Properties." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31862.
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Femtosecond laser interaction with dielectrics has unique characteristics for micromachining, notably non-thermal interaction with materials, precision and flexibility. The nature of this interaction is highly nonlinear due to multiphoton ionization, so the laser energy can be nonlinearly absorbed by the material, leading to permanent change in the material properties in a localized region of Mu-m3. This dissertation demonstrated the potential of these nonlinear interactions induced changes (index modification and ablation for machining) in the dielectrics and explored several practical applications. We studied femtosecond laser ablation of Poly-methayl methacrylate (PMMA) under single and multiple pulse irradiation regimes. We demonstrated that the onset of surface ablation in dielectric surface is associated with surface swelling, followed by material removal. Also, the shape of the ablation craters becomes polarization dependent with increasing fluence, except for circular polarization. The morphology of the damaged/ablated material was examined by optical and scanning electron microscopy. The dynamics of laser ablation of PMMA was simulated using a 2 dimensional Molecular Dynamics model and a 3 dimensional Finite Difference Time Domain model. The results from numerical simulations agreed well with experimental results presented in this thesis.
We also demonstrated the formation of nano-pillar within the ablation crater when the surface of bulk-PMMA was irradiated by two femtosecond pulses at a certain delay with energies below single shot ablation threshold. With increasing fluence, the nano-pillar vanished and the structure within the ablation crater resembled volcanic eruption. At higher fluences we demonstrated nanoscale porosity in PMMA.
For application, a novel in-line fiber micro-cantilever was fabricated in bend insensitive fiber, that provides details of in-line measurement of frequency and amplitude of vibration, and can be further extended to be used as chemical/bio and temperature sensors. By modifying the refractive index at random spacing within the single mode fiber core, a unique quasi-random micro-cavities fiber laser was fabricated, which exhibits comparable characteristics with a commercial fiber laser in terms of narrow linewidth and frequency stability.
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Nshimirimana, Josélyne. "Caractéristiques d’antennes térahertz photoconductrices de type micro-ruban coplanaire." Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9801.
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Ce projet de recherche a permis d'étudier l'émission d'un rayonnement térahertz (THz) par des antennes photoconductrices (PC) émettrices de type micro-ruban coplanaire. Ces antennes sont fabriquées sur substrats d'arséniure de gallium semi-isolant (GaAs-SI) ou sur ce même substrat ayant subit un traitement d'implantation ionique aux protons suivi d'un recuit thermique (GaAs:H). L'influence de ce procédé de fabrication sur les propriétés du matériau photoconducteur et sur les caractéristiques de l'antenne émettrice a été étudiée.
Des mesures de photoconductivité résolue en temps effectuées sur les deux types de substrat montrent que le procédé d'implantation/recuit a eu pour effet de diminuer le temps de vie des photoporteurs de 630 ps à environ 4 ps, tandis que la mobilité n'est réduite que d'un facteur maximum de 1,6. Cette valeur de la mobilité des photoporteurs a par ailleurs été estimée à environ 100 cm$^2$/(V.s) pour le substrat GaAs:H. Les mesures électriques effectuées sur les antennes fabriquées sur les deux types de substrat montrent que le procédé d'implantation/recuit permet d'augmenter la résistivité de la couche active du dispositif d'un facteur 10 (elle passerait de 10$^{8}$ $\Omega$.cm pour le GaAs-SI à 10$^9$ $\Omega$.cm pour le GaAs:H). Les courbes courant-tension, en obscurité et sous illumination, de ces antennes suggèrent également que la densité de pièges profonds est fortement augmentée suite au traitement d'implantation/recuit. L'étude des caractéristiques des diverses antennes a permis de montrer l'intérêt de ce procédé de fabrication. Pour les antennes fabriquées sur GaAs:H, la largeur de bande est améliorée (elle atteint environ 3 THz) et l'amplitude du champ THz émis est augmentée par un facteur 1,4 (dans les mêmes conditions expérimentales). Le rapport signal/bruit des traces THz mesurées sur les antennes les plus performantes est $>$ 200. Une plus grande résistivité et une densité de pièges profonds plus élevée, permet d'appliquer de plus fortes tensions de polarisation sur ces antennes GaAs:H. Finalement, nos résultats ont montré que les améliorations des caractéristiques d'émission de ces antennes THz sont corrélées à la présence d'un champ électrique local plus élevé du coté de l'anode du dispositif.
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Dumont, Paul. "Laser à semiconducteur pompé optiquement bifréquence pour les horloges à atomiques à piégeage cohérent d'atomes de Césium." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLO012/document.
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Les horloges atomiques à piégeage cohérent de population (CPT) constituent aujourd'hui un outil idéal pour la réalisation de références de fréquence stables, compactes et à faible consommation énergétique. Dans le cas des horloges à base de césium, elles nécessitent l'utilisation d'un champ laser bifréquence à 895 nm (raie D1) ou à 852 nm (raie D2) et dont la différence entre les fréquences optiques est égale à 9,19 GHz, soit l'écart entre les niveaux hyperfins du niveau fondamental. Nous proposons une nouvelle solution pour générer ce champ laser, à partir d'un unique laser à semiconducteur pompé optiquement et à émission bipolarisée et bifréquence.Dans ce manuscrit, nous étudions la conception d'une telle source dont l'émission est accordable en fréquence sur la transition D2 du césium. Nous détaillons tout particulièrement le choix des éléments intracavité et de la structure semiconductrice utilisée. Nous décrivons ensuite la mise en oeuvre expérimentale et la caractérisation d'un prototype. Nous présentons les deux boucles d'asservissement que nous avons mises en place pour verrouiller la fréquence optique du laser sur la transition du césium, et la différence de fréquence sur la fréquence délivrée par un oscillateur local. Nous effectuons une modélisation et une caractérisation complète des trois types de bruits du laser, à savoir le bruit d'intensité, le bruit de fréquence optique, et le bruit de phase du signal généré par battement entre les modes laser. Enfin, nous montrons les premiers résultats expérimentaux de piégeage cohérent d'atomes de césium réalisé avec le prototype et étudions les caractéristiques du signal obtenu. Finalement nous établissons un budget de bruit d'une horloge CPT, en nous appuyant sur l'estimation de l'impact de chacun des bruits laser précédemment étudiés. Après avoir identifié les limites du système actuel, nous proposons quelques pistes d'améliorations du laser bifréquence, reposant sur la réduction du bruit d'intensité laser et sur la modification de la structure semiconductriceAtomic clocks using the coherent population trapping (CPT) technic are ex-cellent candidates to obtain frequency references that are stable, compact and with a low powerconsumption. In the case of cesium atomic clocks, this technic require a dual-frequency laserfield either at 895 nm (D1 transition) or 852 nm (D2 transition) whose frequency difference isequal to 9.19 GHz, the frequency splitting between the two hyperfine levels of the fundamentalstate. Here we present a new concept for generating this type of laser field using a unique dualfrequency and optically-pumped laser with a dual-polarized emission.In this manuscript, we study the conception of such a laser source at a wavelength of 852 nm.We detail the design of the intracavity elements and the semiconductor active structure. Thenwe describe the experimental set-up and characterization of a first prototype. We present thestabilization set-up of the laser based on two different servo-loops, one used to lock the opticalfrequency onto the cesium transition and the other to lock the frequency difference onto thefrequency generated by a local oscillator. We report a complete simulation and characterizationof the main laser noises: the laser intensity noise, the optical frequency noise, and the phase noiseof the radiofrequency signal generated by the beatnote of the two laser modes. We show the firstexperimental results of coherent population trapping obtained with the prototype. Finally weestablish a noise budget of a CPT atomic clock by estimating the impact of each laser noises.After we identify the system limits, we propose different ways to improve the dual-frequencywhich rely on the reduction of the intensity noise and the modification of the semiconductorstructure design
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Catros, Sylvain. "Etude de la Micro-Impression d'Eléments Biologiques par Laser pour l'Ingénierie du Tissu Osseux." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14108/document.
Full textAbstract:
L'ingénierie tissulaire osseuse est un domaine multidisciplinaire qui vise à produire des substituts tissulaires pour la médecine régénératrice. Ce travail visait à produire des substituts osseux structurés tridimensionnels grâce à un système d'impression d'éléments biologiques par laser développé au laboratoire Inserm U577 (Projet LASIT: LASer pour L'Ingénierie Tissulaire). Les étapes de la thèse ont consisté tout d'abord à préparer des matériaux adaptés à l'impression par laser et à les caractériser au niveau physico-chimique et biologique. Il s'agissait d'hydroxyapatite nano-cristalline, de cellules humaines et d'hydrogels (alginate, matrigel). Ensuite des impressions structurées combinant ces matériaux ont été réalisées en 3 dimensions avant d'être implantés in vivo chez la souris. Les résultats ont montré que l'impression par laser d'éléments biologiques est une méthode efficace pour organiser des matériaux tridimensionnels à plusieurs composants pour l'ingénierie tissulaireBone Tissue Engineering is a multidisciplinary field which aims to produce artificial tissues for regenerative medicine. The purpose of this work was to produce three-dimensional bone substitute using a laser-assisted bioprinting (LAB) workstation developped in the laboratory INSERM U577 (TEAL Project: Tissue Engineering Assisted by Laser). The first step of the work consisted in the synthesis of specific materials for LAB and in the characterization of their biological and physico-chemical properties. We have prepared a nano-hydroxyapatite bioink, human cells bioinks and hydrogels bioinks. Then, three-dimensional materials have been prepared using LAB and have been implanted in vivo in mice. The results have shown that Laser Assisted Bioprinting is an efficient method fo patterning 3-D materials using biolgical elements
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Gülçür, Mert, J.-M. Romano, P. Penchev, Timothy D. Gough, Elaine C. Brown, S. Dimov, and Benjamin R. Whiteside. "A cost-effective process chain for thermoplastic microneedle manufacture combining laser micro-machining and micro-injection moulding." Elsevier, 2021. http://hdl.handle.net/10454/18446.
Full textAbstract:
YesHigh-throughput manufacturing of transdermal microneedle arrays poses a significant challenge due to the high precision and number of features that need to be produced and the requirement of multi-step processing methods for achieving challenging micro-features. To address this challenge, we report a flexible and cost-effective process chain for transdermal microneedle array manufacture that includes mould production using laser machining and replication of thermoplastic microneedles via micro-injection moulding (micromoulding). The process chain also incorporates an in-line manufacturing data monitoring capability where the variability in the quality of microneedle arrays can be determined in a production run using captured data. Optical imaging and machine vision technologies are also implemented to create a quality inspection system that allows rapid evaluation of key quality indicators. The work presents the capability of laser machining as a cost-effective method for making microneedle moulds and micro-injection moulding of thermoplastic microneedle arrays as a highly-suitable manufacturing technique for large-scale production with low marginal cost.
This research work was undertaken in the context of MICRO-MAN project (“Process Fingerprint for Zero-defect Net-shapeMICROMANufacturing”, http://www.microman.mek.dtu.dk/).MICROMAN is a European Training Network supported byHorizon 2020, the EU Framework Programme for Research andInnovation (Project ID: 674801). This research has also receivedfunding and support from two other Horizon 2020 projects:HIMALAIA (Grant agreement No. 766871) and Laser4Fun (GA no.675063).
The full-text of this article will be released for public view at the end of the publisher embargo on 04 Feb 2022.
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Ma, Hongfeng. "Étude numérique de la micro et nano structuration laser de matériaux poreux nanocomposites." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSES001.
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Cette thèse porte sur les simulations numériques de l’interaction laser avec des matériaux poreux. Une possibilité de traitement bien contrôlé est particulièrement importante pour la microstructuration laser du verre poreux et le nano-usinage de matériaux poreux semiconducteurs en présence de nanoparticules métalliques. La modélisation auto-cohérente se concentre donc sur une étude détaillée des processus impliqués. En particulier, pour comprendre les structures des micro-vides périodiques produits à l’intérieur du verre poreux par des impulsions laser femtoseconde, une analyse thermodynamique numérique détaillée a été réalisée. Les résultats des calculs montrent la possibilité de contrôler le micro-usinage laser en volume de SiO2 . De plus, les dimensions des structures densifiées par laser sont examinées pour différentes conditions de focalisation à de faibles énergies d’impulsion. Les dimensions caractéristiques obtenues à partir des structures sont corrélées avec les résultats expérimentaux. Comparés au verre poreux, les films mésoporeux TiO2 chargés d’ions Ag et de nanoparticules supportent des ré- sonances plasmoniques localisées. Les films nanocomposites obtenus sont capables de transférer des électrons libres et d’absorber l’énergie laser de manière résonnante, offrant des possibilités supplémentaires pour contrôler la taille des nanoparticules d’Ag. Pour identifier les paramètres optimaux du laser à onde continue, un modèle multi-physique prenant en compte la croissance des nanoparticules d’Ag, photo-oxydation, réduction a été développé. Les simulations réalisées montrent que la vitesse d’écriture laser contrôle la taille des nanoparticules d’Ag. Les calculs ont également représenté une nouvelle vision selon laquelle les nanoparticules d’Ag se développent devant le centre du faisceau laser du fait de la diffusion de chaleur. Il a été démontré que la croissance rapide activée thermiquement suivie d’une photo-oxydation est la principale raison du changement de taille et de température en fonction de la vitesse d’écriture. Un modèle tridimensionnel a été développé et reproduit les lignes écrites au laser. L’écriture de films mésoporeux TiO2 chargés de nanoparticules d’Ag par un laser pulsé promet également d’offrir des possibilités supplémentaires dans la génération de deux types de nanostructures: les rainures de surface périodiques induites par laser (LIPSS) et les nanogratings Ag à l’intérieur du film TiO2 . Pour mieux comprendre les effets d’un laser pulsé, deux modèles multiimpulsions - un semi-analytique et un autre basé sur une méthode par éléments finis (FEM) - sont développés pour simuler la croissance des nanoparticules d’Ag. Le modèle FEM s’avère précis car il traite mieux la diffusion de la chaleur à l’intérieur des films minces TiO2 . Le modèle pourrait être étendu à l’avenir pour comprendre la formation de nanogratings LIPSS et Ag dans de tels milieux en les couplant avec les migrations de nanoparticules, la fusion de surface et l’hydrodynamique.Les résultats obtenus ont ouvert de nouvelles perspectives sur le microtraitement laser des matériaux poreux et un meilleur contrôle laser sur la nanostructuration dans les films semiconducteurs poreux chargés de nanoparticules métalliquesThis thesis is focused on numerical simulations of the laser interaction with porous materials. A possibility of well-controlled processing is particularly important for the laser based micro-structuring of porous glass and nano-machining of semiconducting porous materials in the presence of metallic nanoparticles. The self-consistent modeling is, therefore, focused on a detailed investigation of the involved processes. Particularly, to understand the periodic micro-void structures produced inside porous glass by femtosecond laser pulses, a detailed numerical thermodynamic analysis was performed. The calculation results show the possibility to control laser micro-machining in volume of SiO2 . Furthermore, the dimensions of laser-densified structures are examined for different focusing conditions at low pulse energies. The obtained characteristic dimensions of the structures correlate with the experimental results. Comparing to the porous glass, the mesoporous TiO2 films loaded by Ag ions and nanoparticles support localized plasmon resonances. The resulted nanocomposite films are capable to transfer free electrons and to resonantly absorb laser energy providing additional possibilities in controlling Ag nanoparticle size.To identify the optimum parameters of the continuous-wave laser, a multi-physical model considering Ag nanoparticle growth, photo-oxidation, reduction was developed. The performed simulations show that the laser writing speed controls the Ag nanoparticles size. The calculations also depicted a novel view that Ag nanoparticles grow ahead of the laser beam center due to the heat diffusion. The thermally activated fast growth followed by the photo-oxidation was found to be the main reason for the writing speed dependent sizechange and temperature rises. A three-dimensional model was developed and reproduced the laser written lines.Writing of mesoporous TiO2 films loaded with Ag nanoparticles by a pulsed laser is, furthermore, promising to provide additional possibilities in the generation of two kinds of nanostructures: laser induced periodic surface grooves (LIPSS) and Ag nanogratingsinside the TiO2 film. To better understand the effects of a pulsed laser, two multi-pulses models - one semi-analytic and another one based on a finite element method (FEM) are developed to simulate the Ag nanoparticle growth. The FEM model is shown to be precise because it better treats heat diffusion inside the TiO2 thin films. The model could be extended in future to understand the formation of LIPSS and Ag nanogratings in such media by coupling with nanoparticle migrations, surface melting and hydrodynamics. The obtained results provided new insights into laser micro-processing of porous material and better laser controlling over nanostructuring in porous semiconducting films loaded with metallic nanoparticles