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Elementos ópticos difrativos operando em regime de modulação complexa completa / Diffractive optical elements Operating in Regime of Full Complex ModulationPatricia Soares Pinto Cardona 04 June 2003 (has links)
Neste trabalho desenvolvemos duas séries de EODs operando em regime simultâneo de modulação das componentes de fase e de amplitude de uma frente de luz (Modulação Complexa Completa MCC). A primeira destas séries foi constituída por Hologramas de Fourier calculados através do Algoritmo Iterativo da Transformada de Fourier (Iterative Fourier Transform Algorithm IFTA) e a segunda, por Hologramad de Fresnel cujo cálculo da propagação da luz foi obtido por filmagem linear espacial proveniente da solução da Equação de Helmholtz no domínio da frequência. Nos dois casos, a Modulação Complexa Completa foi implementada fisicamente empregando, para realizar a modulação de fase, um micro-relevo gravado em um filme de DLC (Diamond Like Carbon) depositado sobre um substrato de vidro. Sobre este relevo foi implementada a modulação de amplitude, através da deposição de um filme de alumínio, no qual foram realizadas micro-aberturas diferentes cujas áreas eram proporcionais à amplitude em cada pixel. Nos Hologramas de Fourier, uma diferente espessura do filme DLC localizada sobre cada pixel foi responsável pela modulação do valor de fase relativo àquele ponto. Nos Hologramas de Fresnel, a combinação de duas espessuras diferentes do filme de DLC em cada pixel foi responsável pela modulação do valor de fase relativo a cada ponto. Os elementos foram caracterizados física e opticamente e produziram imagens de reconstrução totalmente livres de ruídos do tipo speckle. Também em caráter de avaliação dos resultados foi efetuada a comparação entre as imagens de reconstrução óptica produzidas pelos Hologramas de Fresnel com MCC com as produzidas por Hologramas de Fresnel convencionais em regime de modulação de fase. / In this work, we developed two sets of DOESs able to modulate both phase and amplitude components of light simultaneously (Complete Complex Modulation CCM). The first set is composed of Fourier Holograms calculated by Iteractive Fourier Transform Algorithm (IFTA). The second set is composed by Fresnel Holograms, which light propagation was calculated by spatial linear filtering obtained from the solution of the Helmholtz Equation in the frequency domain. In both cases, Complete Complex Modulation was physically implemented by a micro-relief, for phase modulation, recorded on a Diamond Like Carbon (DLC) film deposited on a glass substrate. Amplitude modulation was implemented on a aluminum fim layer deposited on this relief. In this layer, micro-appertures proportional to the amplitude on each pixel, were recorded. Phase modulation in each pixel of the Fourier Holograms was achivied by different thicknesses of the DLC film. For Fresnel Holograms, phase modulation was achieved by combining two different thicknesses of DLC film inside each pixel. The elements were physically and optically characterized and produced reconstruction images completly free of speckle like noise. The optical reconstruction images produced from Fresnel Holograms working in CCM regime and convencional phase-only modulated Fourier Holograms were compared.
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Composant diffractif numérique multispectral pour la concentration multifonctionnelle pour des dispositifs photovoltaïque de troisième génération / Multispectral digital diffractive element for smart sunlight concentration for third generation photovoltaïc devicesAlbarazanchi, Abbas Kamal Hasan 21 September 2015 (has links)
La lumière du soleil est un bon candidat comme source propre et abondante d'énergie renouvelable. Cette source d'énergie écocompatible peut être exploitée pour répondre aux besoins croissants en énergie du monde. Plusieurs générations de cellules photovoltaïques ont été utilisées pour convertir directement la lumière solaire en énergie électrique. La troisième génération de type multijonction des cellules photovoltaïques est caractérisée par un niveau d'efficacité plus élevé que celui de tous les autres types de cellules photovoltaïques. Des dispositifs optiques, tels que des concentrateurs optiques, des séparateurs optiques et des dispositifs optiques réalisant simultanément la séparation du spectre et la concentration du faisceau ont été utilisés dans des systèmes de cellules solaires. Récemment, les Eléments Optiques Diffractifs (EOD) font l'objet d'un intérêt soutenu en vue de leur utilisation dans la conception de systèmes optiques appliqués aux cellules photovoltaïques. Cette thèse est consacrée à la conception d'un EOD qui peut réaliser simultanément la séparation du spectre et la concentration du faisceau pour des cellules photovoltaïques de type multijonction latéral ou similaire. Les EOD qui ont été conçus ont une structure sous-longueur d'onde et fonctionnent en espace lointain pour implanter la double fonction séparation du spectre et concentration du faisceau. Pour cette raison, des outils de simulation ont été développés pour simuler le comportement du champ magnétique à l'intérieur de l'EOD à structure sous-longueur d'onde. De plus, un propagateur hybride rigoureux a aussi été développé, il est basé sur les deux théories de la diffraction, à savoir la théorie scalaire et la théorie rigoureuse. La méthode FDTD (Finite Difference Time Domain) ou méthode de différences finies dans le domaine temporel a été utilisée pour modéliser la propagation du champ magnétique en champ proche c'est-à-dire à l'intérieur et autour de l'EOD. La méthode ASM (Angular Spectrum Method) ou méthode à spectre angulaire a été utilisée pour modéliser de façon rigoureuse la propagation libre en champ lointain. Deux EOD différents ont été développés permettant d'implanter les fonctions souhaitées (séparation du spectre et concentration du faisceau) ; il s'agit d'une part d'un composant diffractif intitulé G-Fresnel (Grating and Fresnel lens) qui combine un réseau avec une lentille de Fresnel et d'autre part d'une lentille hors-axe. Les composants proposés réalisent la séparation du spectre en deux bandes pour une plage visible-proche infrarouge du spectre solaire. Ces deux bandes peuvent être absorbées et converties en énergie électrique par deux cellules photovoltaïques différentes et disposées latéralement par rapport à l'axe du système. Ces dispositifs permettent d'obtenir un faible facteur de concentration et une efficacité de diffraction théorique d'environ 70 % pour les deux bandes séparées. Grâce à une distance de focalisation faible, ces composants peuvent être intégrés dans des systèmes compacts de cellules solaires. La validation expérimentale du prototype fabriqué montre une bonne correspondance entre les performances expérimentales et le modèle théorique / Sunlight represents a good candidate for an abundant and clean source of renewable energy. This environmentally friendly energy source can be exploited to provide an answer to the increasing requirement of energy from the world. Several generations of photovoltaic cells have been successively used to convert sunlight directly into electrical energy. Third generation multijunction PV cells are characterized by the highest level of efficiency between all types of PV cells. Optical devices have been used in solar cell systems such as optical concentrators, optical splitters, and hybrid optical devices that achieve Spectrum Splitting and Beam Concentration (SSBC) simultaneously. Recently, diffractive optical elements (DOE’s) have attracted more attention for their smart use it in the design of optical devices for PV cells applications.This thesis was allocated to design a DOE that can achieve the SSBC functions for the benefit of the lateral multijunction PV cells or similar. The desired design DOE's have a subwavelength structure and operate in the far field to implement the target functions (i.e. SSBC). Therefore, some modelling tools have been developed which can be used to simulate the electromagnetic field behavior inside a specific DOE structure, in the range of subwavelength features. Furthermore, a rigorous hybrid propagator is developed that is based on both major diffraction theories (i.e. rigorous and scalar diffraction theory). The FDTD method was used to model the propagation of the electromagnetic field in the near field, i.e. inside and around a DOE, and the ASM method was used to model rigorously propagation in the free space far field.The proposed device required to implement the intended functions is based on two different DOE’s components; a G-Fresnel (i.e. Grating and Fresnel lens), and an off-axis lens. The proposed devices achieve the spectrum splitting for a Vis-NIR range of the solar spectrum into two bands. These two bands can be absorbed and converted into electrical energy by two different PV cells, which are laterally arranged. These devices are able to implement a low concentration factor of “concentrator PV cell systems”. These devices also allow achieving theoretically around 70 % of optical diffraction efficiency for the both separated bands. The impact distance is very small for the devices proposed, which allows the possibility to integrate these devices into compact solar cell systems. The experimental validation of the fabricated prototype appears to provide a good matching of the experimental performance with the theoretical model.
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Kombinovaná elektronová litografie / Combined Electron Beam LithographyKrátký, Stanislav January 2021 (has links)
This thesis deals with grayscale e-beam lithography and diffractive optical elements fabrication. Three topics are addressed. The first topic is combined grayscale e-beam lithography. The goal of this task is combining exposures performed by two systems with various beam energies. This combined technique leads to a better usage of both systems because various structures can be more easily prepared by one electron beam energy than by the other. The next topic is the optimization of shape borders of exposing structures that are defined by image input. The influence of such optimization on exposure data preparation is evaluated, as well as the exposure time and the change of optical properties of testing structures. The possibility of deep multilevel diffractive optical element fabrication in plexiglass blocks is researched as the third topic. Plexiglass can replace the system of a resist and a substrate. A new approach to writing down the structures by electron beam is presented, minimizing thermal stress on the plexiglass block during the exposure. The writing method also improves the homogeneity of exposed motifs. A method for computing the exposure dose for specific multilevel structures was designed. This method is based on the existing model of proximity effect computation and it minimizes the computing time necessary to obtain the exposure doses.
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Počítačem generované hologramy / Computer Generated HologramsTvarog, Drahoslav January 2010 (has links)
The presented Diploma thesis deals with the computer-generated diffractive structures or rather called computer generated holograms (CGH). We follow basic principles of classical holography and in the context of which we define a synthetic holography. We then show various types of digital holograms and methods of measurement of their quality. We deal with several iterative algorithms useful for computation of the Fourier transform as well as with methods of phase quantization. In the second part of the work, we describe briefly our computer code for iterative Fourier transform computation. With respect to the mentioned techniques, we further present the usability of the method for design of computer generated holograms in reflection regime. After a short introduction to the electron beam lithography and its exploitation for the origination of computer generated diffractive optical elements. We analyze reconstructions of produced holograms and evaluate its quality.
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Phototraçage massivement parallèle, multirésolution et multiprofondeur de microstructures et nanostructres diffractantes pour les applications antifraudes / Massively parallel-direct-write greyscale photolithography, multi-resolution and multi-depth of diffractive microstructures and nanostructures for anti-fraud applicationsPigeon, Yoran-Eli 04 October 2019 (has links)
Les structures optiques diffractives sous forme d’hologramme de sécurité sont largement employées contre la falsification et la contrefaçon.Elles sont présentent sur les billets de banque, les documents de voyage et d’identité, etc. Leurs techniques de fabrication sont de plus en plus accessibles, augmentant les risques de fraudes et la concurrence sur le marché des hologrammes de sécurité. Pour endiguer les fraudes et gagner des parts de marché, il faut innover. Ces travaux de thèse de doctorat s’articulent autour du développement de structures optiques diffractives multiéchelles innovantes. Ces structures diffractives multiéchelles sont la combinaison de structures diffractives microscopiques permettant la mise en forme de la lumière incidente avecdes structures nanoscopiques qui permettent la création d’effets colorés. Ces travaux accordent une grande place au développement de la technique de photolithographie multiniveaux par écriture directe massivement parallèle. Ils abordent également le développement d’un modèle hybride permettant de simuler physiquement le comportement des structures diffractives (notamment de nos structures multiéchelles) en temps réel. Ce rendu en temps réel est possible grâce à l’utilisation du processeur graphique (GPU) au travers d’OpenGL et des programmes Shader, ainsi qu’avec l’utilisation de données précalculées. Le développement de ces structures multiéchelles permet la création et la commercialisation de nombreux nouveaux effets visuels, ce qui participe aux doubles objectifs de contrer les fraudes et de gagner en part de marché. / Diffractive optical structures on the fon of security holograms are widely used against forgery and counterfeiting. They are present on banknotes, travel and identity documents, etc. Their manufacturing techniques are becoming more and more accessible, increasing the risk of fraud and competition in the security hologram market. To stem fraud and gain marketshare, hologram procedures must innovate continously. This Ph.d focuses on the developmentof innovative multi-scale diffractive optical structures. These multi-scale diffractive structures result from combination of microscopic diffractive structures that shape the incident light and nanoscopic structures that generate colored effects. This work places emphasis on the development of the massively parallel-direct-write greyscale photolithography fabrication process. We also discuss the development of an hybrid model for physically simulating the behaviour of diffractive structures (especially our multiscale structures) in real time. This real time rendering is possible thanks to the use of the graphical processor unit (GPU) through OpenGL and Shader programs, as well as the use of precomputed data. The development of these multiscale structures has led to the creation and commercialisation of many new visual effects and contributed to the dual objectives of counter fraud and gain market share.
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Chemická a spektroskopická charakterizace keltských kovových artefaktů / Chemical and Spectroscopic Characterization of Celtic Metal ArtifactsIšková, Petra January 2010 (has links)
The thesis comprehensively investigates 2 pcs of ferrous and 14 pcs of bronze Celtic artefacts from a region of Zdejciny by Beroun. The study by means of ore microscopy, x-ray fluorescent microspectrometry, chemical microanalysis, Raman microspectrometry and x-ray powder diffractive analysis has showed that the bronze artefacts are made mainly of bronze. The phases present in the studied items correspond to fields and + of the Cu-Sn phase diagram. Content of Sn in bronze ranges between 4 and 33 wt.%. For the bronze selected items there was also Vickers microhardness measured. There were two artefacts where areas with a significant lead enrichment were found. Corrosive products were also deeply analysed and identified.
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Design and Fabrication of Nonconventional Optical Components by Precision Glass MoldingHe, Peng January 2014 (has links)
No description available.
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Manufatura de microelementos ópticos difrativos / Manufacturing of diffractive optical microelementsColafemina, João Paulo 17 December 2010 (has links)
Os elementos ópticos difrativos representam um mercado em franco crescimento, da ordem de bilhões de dólares. Seu uso ostensivo está nos microeletrônicos, sistemas de iluminação, telecomunicações, equipamentos de segurança e outros. Por isso, esta tese teve como objetivo realizar investigação pública profunda no assunto. Insertos de cobre eletrolítico foram usados por proporcionar excelente acabamento superficial quando usinados com ferramenta de diamante monocristalino obtendo valores de Ra = 10,2 nm, Rq = 13,56 e Rt = 363,06 µm e para o aço inoxidável polido os resultados foram de Ra = 7,02 nm, Rq = 9,05 nm e Rt = 225,19 nm. As réplicas foram construídas em PMMA - DH ECL P com transmitância da luz avaliada em aproximadamente 90% em todo o espectro visível e infravermelho. Foram produzidos sete tipos de microelementos ópticos difrativos, baseados na geometria de Fresnel e nos arranjos de microlentes esféricas. Foi necessário desenvolver o código computacional denominado LF2010 para auxiliar a construção do projeto das microlentes anesféricas de Fresnel e calcular sua modulação de fase. Quatro processos determinísticos na fabricação dos µEODs foram usados: torneamento de ultraprecisão com ferramenta de diamante, microforjamento, microfresamento e a combinação dos dois últimos. O método estocástico de polimento foi usado para gerar acabamento óptico e compará-lo ao torneamento com SPDT. As análises metrológicas qualitativas e dimensionais foram conduzidas com o uso do MEV e da perfilometria óptica. No torneamento de ultraprecisão com ferramenta de diamante foi comprovada a presença do fenômeno conhecido como \"stick slip\" nos degraus da zona de Fresnel, corrigidos alterando-se o projeto. Para os arranjos de empacotamento completo os valores da rugosidade foram mais elevados em função da interatividade das lentes adjacentes do conjunto com \'fi\' = 100%, chegando até mesmo a causar microfraturas na estrutura das microlentes. Após sucessivos processos de calibragem, foram manufaturadas as réplicas pelas técnicas de termomoldagem e moldagem por injeção. Os resultados de replicação das microlentes mostraram que a razão de aspecto e a relação superfície/volume influenciaram significativamente na fidelidade de replicação das microlentes, sendo constatado que as lentes de Fresnel com altura variável possuem maior volume em relação às de altura constante e, consequentemente, melhor fidelidade na replicação. Na termomoldagem, as variações nas dimensões das cristas foram de nanômetros e a fidelidade no processo foi de aproximadamente 100% para todas as zonas de Fresnel. Nesta técnica, porém, os tempos de ciclos são até 40 vezes maiores que os da moldagem por injeção. As investigações paraxiais de FTM para a microlente de Fresnel com altura variável convexa foram de 85,2 % para 25 lp/mm, 67,5% para 50 lp/mm e 71,2% para 75 lp/mm. A simulação por elementos finitos foi usada para auxiliar nos estudos conferindo a sensibilidade do método de cálculo numérico do simulador nas escalas macroscópicas e microscópicas. No final, investigado o desgaste da aresta de corte da ferramenta, verificou-se o desgaste de flanco e a formação da APC, constituída de partículas do cavaco de cobre com formação lamelar. Conclui-se que é possível reproduzir diversos tipos de µEODs com métodos de produção em massa da moldagem por injeção tomando-se cuidado com as variáveis do processo, geometria da peça e propriedades físicas e químicas do material a ser replicado. / Diffractive optical elements represent a fast growing market, in order of billions dollars. Its use is employed in microelectronics, illumination systems, telecommunications, security devices, and others. For this reason, this thesis aimed to make depth public research in the subject. Electrolytic copper inserts were used for providing excellent surface finish when machined with monocrystalline diamond tool getting values of Ra = 10,2 nm, Rq = 13,56 e Rt = 363,06 µm, for the polished stainless steel the results were Ra = 7,02 nm, Rq = 9,05 nm e Rt = 225,19 nm. The replicas were built in PMMA - DH ECL P with light transmittance approximately 90% for visible and infrared spectrum. Seven types of diffractive optical microelements were produced, based in Fresnel geometry and spherical microlens array. For this, it was necessary to develop the computer code called LF2010 to support the construction design of aspheric Fresnel microlenses and calculate its phase transformation function. Four deterministic manufacturing processes of µDOEs were used: ultraprecision diamond turning, microforging, micromilling and the combination of the two last. Stochastic method of polishing was used to obtain mirror surface roughness and compare to SPDT. The qualitative analysis and dimensional metrology were conducted using MEV and optical profiling system respectively. In ultraprecision diamond turning has proved the presence of the phenomenon known as stick slip on the steps of Fresnel zone that was corrected by changing the design. For complete packaging arrays the roughness values were higher due the interaction of adjacent lenses of set with \'fi\' = 100% have even cause microfractures in the structure of microlenses. After successive calibration procedures in the manufacture of copper inserts, replicas were fabricated by techniques of hot emboss and injection molding. The results of microlenses replication showed that the aspect ratio and surface/volume ratio affected the fidelity replication of microlenses, and had been noted that the Fresnel lenses with variable height have higher volume in relation to constant height and consequently better fidelity in replication. Hot emboss process show little variations in the dimensions of the crests, in order of few nanometers, resulting a fidelity approximately 100% for all zones of Fresnel, however the cycle\'s technique are up to 40 times higher than injection molding. The paraxial FTM analysis shows 85,2% for 25 lp/mm, 67,5% for 50 lp/mm and 71,2% for 75 lp/mm to convex Fresnel microlens with variable height. Finite element analysis was used to aid in the studies giving the sensitivity of numerical method adopted in terms of macroscale and microscale. In the end, the wear of edge cutting tool was investigated and found wear flank and formation of built up edge that was made up of chip particles of copper, witch were formed continuously with segmented structure lamellar. Hence, after numerous studies and analysis we can conclude that it is possible to construct µDOEs by means of mass production methods of injection molding taking care of process variables, part geometry and physical and chemical properties of material being replicated.
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Manufatura de microelementos ópticos difrativos / Manufacturing of diffractive optical microelementsJoão Paulo Colafemina 17 December 2010 (has links)
Os elementos ópticos difrativos representam um mercado em franco crescimento, da ordem de bilhões de dólares. Seu uso ostensivo está nos microeletrônicos, sistemas de iluminação, telecomunicações, equipamentos de segurança e outros. Por isso, esta tese teve como objetivo realizar investigação pública profunda no assunto. Insertos de cobre eletrolítico foram usados por proporcionar excelente acabamento superficial quando usinados com ferramenta de diamante monocristalino obtendo valores de Ra = 10,2 nm, Rq = 13,56 e Rt = 363,06 µm e para o aço inoxidável polido os resultados foram de Ra = 7,02 nm, Rq = 9,05 nm e Rt = 225,19 nm. As réplicas foram construídas em PMMA - DH ECL P com transmitância da luz avaliada em aproximadamente 90% em todo o espectro visível e infravermelho. Foram produzidos sete tipos de microelementos ópticos difrativos, baseados na geometria de Fresnel e nos arranjos de microlentes esféricas. Foi necessário desenvolver o código computacional denominado LF2010 para auxiliar a construção do projeto das microlentes anesféricas de Fresnel e calcular sua modulação de fase. Quatro processos determinísticos na fabricação dos µEODs foram usados: torneamento de ultraprecisão com ferramenta de diamante, microforjamento, microfresamento e a combinação dos dois últimos. O método estocástico de polimento foi usado para gerar acabamento óptico e compará-lo ao torneamento com SPDT. As análises metrológicas qualitativas e dimensionais foram conduzidas com o uso do MEV e da perfilometria óptica. No torneamento de ultraprecisão com ferramenta de diamante foi comprovada a presença do fenômeno conhecido como \"stick slip\" nos degraus da zona de Fresnel, corrigidos alterando-se o projeto. Para os arranjos de empacotamento completo os valores da rugosidade foram mais elevados em função da interatividade das lentes adjacentes do conjunto com \'fi\' = 100%, chegando até mesmo a causar microfraturas na estrutura das microlentes. Após sucessivos processos de calibragem, foram manufaturadas as réplicas pelas técnicas de termomoldagem e moldagem por injeção. Os resultados de replicação das microlentes mostraram que a razão de aspecto e a relação superfície/volume influenciaram significativamente na fidelidade de replicação das microlentes, sendo constatado que as lentes de Fresnel com altura variável possuem maior volume em relação às de altura constante e, consequentemente, melhor fidelidade na replicação. Na termomoldagem, as variações nas dimensões das cristas foram de nanômetros e a fidelidade no processo foi de aproximadamente 100% para todas as zonas de Fresnel. Nesta técnica, porém, os tempos de ciclos são até 40 vezes maiores que os da moldagem por injeção. As investigações paraxiais de FTM para a microlente de Fresnel com altura variável convexa foram de 85,2 % para 25 lp/mm, 67,5% para 50 lp/mm e 71,2% para 75 lp/mm. A simulação por elementos finitos foi usada para auxiliar nos estudos conferindo a sensibilidade do método de cálculo numérico do simulador nas escalas macroscópicas e microscópicas. No final, investigado o desgaste da aresta de corte da ferramenta, verificou-se o desgaste de flanco e a formação da APC, constituída de partículas do cavaco de cobre com formação lamelar. Conclui-se que é possível reproduzir diversos tipos de µEODs com métodos de produção em massa da moldagem por injeção tomando-se cuidado com as variáveis do processo, geometria da peça e propriedades físicas e químicas do material a ser replicado. / Diffractive optical elements represent a fast growing market, in order of billions dollars. Its use is employed in microelectronics, illumination systems, telecommunications, security devices, and others. For this reason, this thesis aimed to make depth public research in the subject. Electrolytic copper inserts were used for providing excellent surface finish when machined with monocrystalline diamond tool getting values of Ra = 10,2 nm, Rq = 13,56 e Rt = 363,06 µm, for the polished stainless steel the results were Ra = 7,02 nm, Rq = 9,05 nm e Rt = 225,19 nm. The replicas were built in PMMA - DH ECL P with light transmittance approximately 90% for visible and infrared spectrum. Seven types of diffractive optical microelements were produced, based in Fresnel geometry and spherical microlens array. For this, it was necessary to develop the computer code called LF2010 to support the construction design of aspheric Fresnel microlenses and calculate its phase transformation function. Four deterministic manufacturing processes of µDOEs were used: ultraprecision diamond turning, microforging, micromilling and the combination of the two last. Stochastic method of polishing was used to obtain mirror surface roughness and compare to SPDT. The qualitative analysis and dimensional metrology were conducted using MEV and optical profiling system respectively. In ultraprecision diamond turning has proved the presence of the phenomenon known as stick slip on the steps of Fresnel zone that was corrected by changing the design. For complete packaging arrays the roughness values were higher due the interaction of adjacent lenses of set with \'fi\' = 100% have even cause microfractures in the structure of microlenses. After successive calibration procedures in the manufacture of copper inserts, replicas were fabricated by techniques of hot emboss and injection molding. The results of microlenses replication showed that the aspect ratio and surface/volume ratio affected the fidelity replication of microlenses, and had been noted that the Fresnel lenses with variable height have higher volume in relation to constant height and consequently better fidelity in replication. Hot emboss process show little variations in the dimensions of the crests, in order of few nanometers, resulting a fidelity approximately 100% for all zones of Fresnel, however the cycle\'s technique are up to 40 times higher than injection molding. The paraxial FTM analysis shows 85,2% for 25 lp/mm, 67,5% for 50 lp/mm and 71,2% for 75 lp/mm to convex Fresnel microlens with variable height. Finite element analysis was used to aid in the studies giving the sensitivity of numerical method adopted in terms of macroscale and microscale. In the end, the wear of edge cutting tool was investigated and found wear flank and formation of built up edge that was made up of chip particles of copper, witch were formed continuously with segmented structure lamellar. Hence, after numerous studies and analysis we can conclude that it is possible to construct µDOEs by means of mass production methods of injection molding taking care of process variables, part geometry and physical and chemical properties of material being replicated.
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Spectroscopie de phase multi-dimensionnelle de l'émission attoseconde moléculaire / Multidimensionnal Phase Spectroscopy of the Attosecond Molecular EmissionCamper, Antoine 31 January 2014 (has links)
Une molécule soumise à un champ laser infra-rouge intense (dans la gamme des 10 14 W.cm−2) peut être ionisée par effet tunnel. Le paquet d’ondes électroniques (POE) ainsi libéré est alors accéléré par le champ laser et, lorsqu’il repasse à proximité de l’ion parent, il a une certaine probabilité de se recombiner dans son état fondamental. Lors de cette recombinaison, le POE libère son énergie sous la forme d’un flash attoseconde (1as=10 −18s) de rayons XUV. Cette émission cohérente est produite à chaque demi-cycle laser résultant en un train d’impulsions attosecondes. Dans le domaine spectral, ce train correspond à un spectre discret d’harmoniques de la fréquence lasers. L’étape de recombinaison de l’électron avec l’ion parent peut être considérée comme une sonde de la structure des orbitales de valence moléculaires participant à la génération d’harmoniques et de la dynamique ayant lieu dans l’ion pendant l’excursion de l’électron dans le continuum. En caractérisant en amplitude, phase et polarisation, l’émission harmonique associée à cette recombinaison, il est possible de remonter à ces informations structurales et dynamiques avec une précision de l’ordre de l’Ångström et une résolution attoseconde. En particulier, la phase de l’émission harmonique qui est difficile à caractériser, encode des informations indispensables à la bonne compréhension des processus ayant lieu dans le milieu de génération. Nous présentons les principes et testons de nouvelles techniques permet tant de caractériser la phase de l’émission attoseconde suivant plusieurs dimensions à la fois et dans un laps de temps optimisé. Dans une première partie, nous présentons une méthode permettant de caractériser rapidement la phase spectrale de l’émission harmonique, fondée sur un modèle en champ fort de la photoionisation à deux couleurs (RABBIT). Nous introduisons ensuite une nouveau dispositif interférométrique à deux sources, permettant de mesurer les variations de phase de l’émission attoseconde induites par l’excitation d’un paquet d’ondes rotationnelles ou vibrationnelles. Ce dispositif très stable, compact et sobre énergétiquement repose sur l’utilisation d’un élément optique de diffraction (DOE) binaire. Après avoir qualifié notre dispositif par des simulations numériques et des expériences préliminaires, nous montrons qu’il est si sensible qu’il permet de mesurer les variations de phase en fonction du paramètre d’excitation pour différentes trajectoires électroniques dans le continuum. Pour l’azote et le dioxyde de carbone, les mesures expérimentales montrent des variations de phase très différentes pour les deux premières trajectoires électroniques. Ce DOE est ensuite utilisé pour mesurer la phase de l’émission harmonique dans les molécules alignées dans les mêmes conditions expérimentales que le RABBIT. Les deux expériences menées successivement donnent des résultats compatibles que nous combinons par deux méthodes différentes : le CHASSEUR et le MAMMOTH. Enfin, nous proposons de combiner le DOE avec un réseau transitoire pour caractériser simultanément la phase de l'émission attoseconde moléculaire suivant deux axes de polarisation différents. Ces différentes techniques de mesure de phase nous ont permis d’étudier précisément l’émission harmonique suivant différentes dimensions (angle d’alignement, intensité de génération, trajectoire électronique) et d’en tirer de nouvelles informations sur le mécanisme de génération dans les molécules. / When a low-frequency laser pulse is focused to a high intensity into a gas, the electric field of the laser light may become of comparable strength to that felt by the electrons bound in an atom or molecule. A valence electron can then be 'freed' by tunnel ionization, accelerated by the strong oscillating laser field and can eventually recollide and recombine with the ion. The gained kinetic energy is then released as a burst of coherent XUV light which is spectrally organized as harmonics of the fundamental driving field frequency.In high-harmonic molecular spectroscopy, the recombining electron wave-packet probes the structure of the molecule and the dynamics occurring in the ion left after tunnel ionization. The XUV burst is imprinted with this information which can be retrieved through an accurate characterization of the amplitude, phase and polarization of the harmonics. In the case of small molecules as nitrogen and carbon dioxide, impulsive alignment allows to change the direction of recombination of the electron wave-packet with respect to the molecular axis. The XUV burst from the molecular sample should then be characterized both along the spectral dimension and the alignment angle one, and this for the two polarization components. In this report, we present a new experimental scheme to perform two-source interferometry to measure the phase of the emission in aligned molecules along the alignment angle dimension. We how a refined spatio-spectral analysis of the fringe patterns obtained with this very stable interferometer allows one to extend high-harmonic spectroscopy from short to long trajectories. We then show how the combination of this setup together with RABBIT gives access to a bidimensionnal (spectrum and alignment angle) phase map with no arbitrary constant. Finally comparing two-source interferometry with transient grating spectroscopy leads to inconsistent results that can be interpreted taking into consideration polarization effects.
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