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1
Telliez, Cécile. „Advanced optical microscopy for spatially and temporally precise deep brain interrogation“. Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS041.
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Dans le domaine des neurosciences, l'avènement des outils optogénétiques sensibles à la lumière a ouvert de nouvelles opportunités pour contrôler précisément l'activité neuronale et étudier le fonctionnement cérébral optiquement. En optique, cela a motivé le développement de diverses stratégies d'illumination et de collecte de la lumière pour imager l'activité neuronale et la manipuler avec une précision spatiotemporelle élevée. En particulier, les approches de mise en forme de la lumière, telles que l'holographie générée par ordinateur combinée à la focalisation temporelle, ont permis de cibler des neurones individuels ou des groupes de neurones avec une grande précision temporelle et une précision spatiale proche de la cellule unique, dans des espaces volumétriques de centaines de microns. Cette précision est cruciale pour obtenir des informations critiques sur le code neuronal et établir des connexions entre l'activité neuronale, le comportement et la perception à une échelle fine. Malgré ces avancées, des défis persistent pour permettre des investigations cérébrales complexes, notamment en ce qui concerne le contrôle de vastes populations de cellules avec une précision spatiotemporelle élevée en profondeur. Pendant ma thèse, j'ai particulièrement concentré mes efforts sur ces défis et développé de nouvelles stratégies optiques de mise en forme de la lumière visant à (i) étendre le nombre de neurones excitables, (ii) améliorer la résolution temporelle et (iii) augmenter la profondeur de pénétration de l'investigation optogénétique multi-photonique ciblée et basée sur la modulation de phase de la lumière.Initialement, j'ai concentré mes efforts sur le développement d'un système optique ultra-rapide à deux photons (2P) (FLiT), où un modulateur spatial de lumière et un miroir galvanométrique sont couplés pour permettre la commutation à un taux de kHz de motifs d'illumination précis spatialement sur l'échantillon. Cela sert deux objectifs principaux. Premièrement, cela permet d'ajuster optiquement le temps d'excitation relatif de cellules distinctes avec une résolution temporelle d'environ un ordre de grandeur supérieur par rapport aux méthodes précédentes. Deuxièmement, FLiT permet de cibler un ensemble donné de cellules en réduisant le budget de puissance d'excitation d'un facteur 4-5, tout en minimisant l'élévation thermique induite par la lumière. Pour pousser cette approche encore plus loin, j'ai ensuite modifié la conception optique originale en incluant une unité de de-scan (deFLiT), ce qui a permis d'élargir le nombre d'hologrammes utilisables et d'augmenter encore davantage le gain de puissance et la précision temporelle du FLiT conventionnel.Dans la deuxième phase de la thèse, je me suis concentré sur un système holographique à trois photons (3P) pour mener des expériences d'optogénétique plus profondément à l'intérieur du cerveau. J'ai conçu et construit le système, puis je l'ai validé en photo-activant diverses opsines et en induisant leur activation à haute fréquence dans les neurones ciblés sous un régime d'excitation à 3P que j'ai également vérifié. Par rapport aux systèmes holographiques à deux photons précédents, cette approche permettra d'étendre les investigations entièrement optiques à des régions plus profondes du cerveau.Ces nouvelles stratégies seront importantes pour étudier les circuits neuronaux avec une stimulation optogénétique rapide et précise à travers de vastes ensembles neuronaux en profondeurIn the field of neuroscience, the advent of light-sensitive optogenetic tools has opened new opportunities for precisely controlling neuronal activity and study brain functioning optically. In optics, this has motivated the development of various light-delivery and collection strategies to functionally image and manipulate neural activity with high spatiotemporal precision. Particularly, light-shaping approaches, such as Computer-Generated Holography combined with Temporal Focusing, have enabled temporally precise targeting of individual neurons or clusters with near single-cell accuracy within volumetric spaces of hundreds of microns. This precision is crucial to get critical insights into the neural code and establishing connections between neural activity with behavior and perception at fine scale. Despite these advancements, challenges persist in enabling complex brain investigations, especially when it comes to control vast populations of cells with high spatiotemporal precision in depth. During my thesis, I particularly focused on those challenges and developed new light-shaping optical strategies aiming at (i) expanding the number of excitable neurons, (ii) improving temporal resolution and (iii) increasing the penetration depth of cell-targeted multiphoton optogenetic investigation based on phase-modulation light-targeting.Initially, I concentrated on developing an ultra-fast two-photon (2P) optical system (FLiT), where a multiplexing LC-SLM and a galvanometric mirror are coupled to allow kHz-rate switching of spatially precise illumination patterns on the sample. This serves two primary purposes. Firstly, it enables to optically tune the relative spiking time of distinct cells with a temporal resolution of about one order of magnitude higher compared to previous methods. Secondly, FLiT allows targeting a given ensemble of cells by reducing the excitation power budget by a 4-5 factor, while minimizing light-induced thermal rise. To push forward this approach, I further modified the original optical design by including a de-scan unit (deFLiT) which enabled to enlarge the number of usable holograms and increase even further the power gain and temporal precision of conventional FLiT .In the second phase of the thesis, I focused on a three-photon (3P) holographic system to conduct optogenetics experiments deeper inside the brain. I designed and built the system and I then validated it by photo-activating various opsins and driving high-rate firing in targeted neurons under a verified 3PE regime. Compared to previous holographic 2P-photon systems, this approach will enable the extension of all-optical investigations to deeper brain regions.These new strategies will be important for studying neuronal circuits with rapid and precise optogenetic stimulation across large neuronal ensembles in depth
2
Hayward, Robert M. „A coarse mesh transport method for photons and electrons in 3-D“. Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51928.
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A hybrid stochastic-deterministic method, COMET-PE, is developed for dose calculation in radiotherapy. Fast, accurate dose calculation is a key component of successful radiotherapy treatment. To calculate dose, COMET-PE solves the coupled Boltzmann Transport Equations for photons and electrons. The method uses a deterministic iteration to compose response functions that are pre-computed using Monte Carlo. Thus, COMET-PE takes advantage of Monte Carlo physics without incurring the computational costs typically required for statistical convergence. This work extends the method to 3-D problems with realistic source distributions. Additionally, the performance of the deterministic solver is improved, taking advantage of both shared-memory and distributed-memory parallelism to enhance efficiency. To verify the method’s accuracy, it is compared with the DOSXYZnrc (Monte Carlo) method using three different benchmark problems: a heterogeneous slab phantom, a water phantom, and a CT-based lung phantom. For the slab phantom, all errors are less than 1.5% of the maximum dose or less than 3% of local dose. For both the water phantom and the lung phantom, over 97% of voxels receiving greater than 10% of the maximum dose pass a 2% (relative error) / 2 mm (distance-to-agreement) test. Timing comparisons show that COMET-PE is roughly 10-30 times faster than DOSXYZnrc. Thus, the new method provides a fast, accurate alternative to Monte Carlo for dose calculation in radiotherapy treatment planning.
3
Grootoonk, Sylke. „Dual energy window correction for scattered photons in 3-D positron emission tomography“. Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/844524/.
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In the past few years, the collection of positron emission tomography (PET) data without inter-plane shielding has become a widely accepted technique for significantly increasing the sensitivity of multi-ring scanners. However, the resultant increase in the registration of counts due to scattered events is undesirable for quantitative studies, since it reduces contrast and confounds the linear response of the scanner to activity concentration. This thesis describes the development, implementation and evaluation of a correction for scattered photons based on the simultaneous acquisition of emission data in two energy windows. Initial experiments were performed to characterize the distribution of of scattered photons in data collected with a commercial PET brain scanner operated without inter-plane shielding (septa). In this mode of acquisition, termed 3-D, coincidences between all rings of detectors are accepted. This is in contrast to the conventional 2-D acquisition mode, where data is acquired with a more restricted range of inter-ring combinations. The fraction of scattered photons under standard operating conditions was measured as 35 (+/-2) % for a line source in a 20 cm diameter water-filled cylinder, and the scatter response function found to be shift-variant. A 20% gain in counts from events that do not scatter in the object but in the detectors themselves was achieved by lowering the energy threshold as far as reasonably possible. The correction developed for scattered photons relies on parameters relating two energy windows which were selected to maximize counting statistics and minimize spatial variations. The ratio functions for the selected windows were found to be shift-invariant, and showed little variation with object size. The parameters were however found to be very susceptible to changes in detector efficiency, showing up to 10% variations over time. The correction was implemented with constant values taken for the ratio functions, and integrated into the routine reconstruction sequence with pre-processing steps taken to minimize noise propagation. When evaluated in a range of standard and customized test objects, the correction restored contrast in inactive areas to within 5% of the true value. Relative activity concentrations in different sized phantoms were restored to better than 6%. A means of calibrating the data corrected for scattering was implemented and quantification in a range of activity distributions was accurate to within 7%. The correction method was tested in a phantom which simulates the activity distribution in a human brain. Applying the method to human data confirmed the potential of using this method routinely for quantification in vivo. A limitation of the method for dynamic scanning was identified: high count rate pile-up effects introduce global spatial and spectral distortions which are enhanced in the dual energy window correction for scattering. However, in multi-time frame scanning of test phantoms, the correction consistently restored contrast and maintained linearity. The data acquisition, correction for scattering and reconstruction regimes that have been developed in this work have, thus far, allowed the routine collection of several hundred dynamic ligand studies in patients and normal volunteers, which have been analyzed as part of clinical research projects in a fully quantitative manner.
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Bouhadida, Maha. „Étude d’effets optiques non linéaires d’ordres 2 et 3 dans des nanofibres optiques“. Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASP019.
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Cette thèse de doctorat porte sur l'étude d'effets optiques non linéaires d’ordres 2 et 3 dans des nanofibres optiques de silice qui sont des fibres optiques étirées jusqu'à atteindre des diamètres de l'ordre de la longueur d'onde.La première application étudiée est la réalisation de convertisseurs de longueur d’onde dans le visible en régime sub-nanoseconde, domaine peu couvert par les sources impulsionnelles actuelles. Le principe de ces convertisseurs repose sur la diffusion Raman stimulée dans le champ évanescent d’une nanofibre optique de silice baignée dans un liquide. En définissant et optimisant leur domaine de fonctionnement, nous avons atteint des efficacités de conversion externes de l'onde de pompe à 532 nm vers le premier ordre Stokes de l'éthanol à 630 nm proches de 60%. Les performances de nos convertisseurs sont très répétables et ouvrent la voie à une nouvelle famille de convertisseurs de longueur d'onde très compacts, efficaces, fiables et entièrement fibrés.La seconde application visée concerne l'étude d'une source de paires de photons corrélés émettant autour de 1,5 μm pour les télécommunications quantiques. Notre source est basée sur le mécanisme de fluorescence paramétrique à la surface d’une nanofibre optique de silice. Dans l'accord de phase modal étudié, l'onde de pompe est émise sur le mode TM01 à 775 nm et les paires de photons corrélés sont générées autour de 1,5 microm sur le mode fondamental HE11, avec l'avantage de pouvoir se recoupler avec un minimum de pertes dans un réseau fibré. Nos études ont principalement porté sur le choix de la fibre standard permettant d'optimiser l'efficacité du mécanisme, la conception de la nanofibre et de ses tapers ainsi que la mise en place d'expériences préliminaires pour l'excitation de modes d'ordre supérieurIn this PhD thesis we study 2nd and 3rd order optical non-linearities in optical nanofibers, which are obtained by stretching standard fibers until their diameter becomes of the order of magnitude of the wavelength. The first application is the realization of wavelength converters in the visible range in the sub-ns regime, range which is only minimally covered by pulsed sources. The principle of these converters is to use stimulated Raman scattering in the evanescent field immersed in a liquid. By defining and optimizing their operating range, we have reach external conversion efficiencies from the pump at 532 nm to the first Stokes order of ethanol at 630 nm near to 60%. The performances of our converters are very repeatable and open the way to a new family of very compact, reliable and all-fibered components.The second application is the study of a source of correlated photon pairs for quantum telecommunications. Our source is based of parametric fluorescence on the surface of a silica nanofiber. In the phase-matching we propose, the pump wave is emitted on the mode TM01 at 775 nm and the photon pairs are emitted around1.5 μm in the fundamental mode, enabling a recoupling with only a few losses in the optical network. Our study mainly concern the choice of the standard fiber enabling to optimize the efficiency of the mechanism, the conception of the nanofiber and its tapers as well as the implementation of preliminary experiments for the excitation of high ordrer modes
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GRISCOM, LAURENT. „Synthese et proprietes optiques des verres de chalco-halogenures : spectroscopie a 1,3 microns et addition de photons des ions nd 3 + et pr 3 +“. Rennes 1, 1999. http://www.theses.fr/1999REN10191.
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Des sources lumineuses sont, a ce jour activement recherchees a 1,3 m pour augmenter la capacite des reseaux de telecommunications par fibres optiques. Pour cela, des compositions de verres dopes aux terres rares et optimises du point de leurs proprietes optiques sont necessaires. Les verres de chalcogenures ayant des indices de refraction eleves et une transparence dans l'infrarouge qui s'etend au-dela de 10 m possedent les qualites necessaires pour operer a cette longueur d'onde. Les verres de chalco-halogenures, avec les elements ge-ga-s-csx ou x = c1, br, i ont ete synthetise au laboratoire. L'ajout d'un halogenure au verre de chalcogenure se traduit par une amelioration de la stabilite thermique et un elargissement du domaine de la transparence dans le visible sans changer les caracteristiques dans l'infrarouge. Ces verres possedent, par ailleurs, une bonne solubilite des ions de terre rare. Ils ont ete dopes par les ions nd 3 + et pr 3 +. Les proprietes physiques et optiques (temperatures caracteristiques, densite, indices de refraction, transmission uv et ir) de ces verres ont ete mesurees et comparees avec celles de verres de sulfure classiques. La theorie de judd-ofelt a ete employee pour la comprehension des mecanismes des transitions 4f-4f dans ces verres. Cependant, les verres de chalcogenures posent des problemes pour l'application de cette theorie du fait du bandgap qui occulte les bandes d'absorption de haute energie des ions de terre rare. Quelques methodes nouvelles ont ete testees pour appliquer la theorie de judd-ofelt dans les verres de chalcogenures. Les emissions des ions nd 3 + et pr 3 + ont ete etudiees dans les verres ga-ge-csx, en fonction de halogene x et en fonction de la concentration en ions de terre rare. Concernant la neodyme, les spectres d'emission ir du niveau 4f 3 / 2 et les emissions visibles de ( 4g 7 / 2, 2k 1 3 / 2, 4g 9 / 2) ont ete enregistres et les durees de vie mesurees. Les processus d'esa a partir de 4f 3 / 2 qui contribuent a reduire l'emission a 1,3 m de nd 3 + ont ete egalement enregistre. Concernant le praseodyme, les spectres d'emissions ainsi que les durees de vie des niveaux 1g 4 (transition a 1,3 m), 1d 2 et 3p j ont ete mesures une part important de ce travail a ete consacre a la mise en evidence et a la caracterisation des processus d'addition de photons vers les niveaux ( 4g 7 / 2, 2k 1 3 / 2, 4g 9 / 2) de nd 3 + et vers les niveaux 1d 2 et 3p j de pr 3 +.
6
Harlé, Thibault. „Sources fibrées de paires de photons : caractérisation et influence de la non-uniformité“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLO009/document.
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Les sources de paires de photons constituent un bloc de base pour les technologies de traitement et transmission de l'information quantique. Une source consistant en une fibre microstructurée à coeur liquide permet à la fois une réduction du bruit de diffusion Raman, une adaptation simple et efficace aux réseaux de télécommunication quantique, et l'ajustement de ses propriétés d'émission par ingénierie de la microstructure et choix du liquide non linéaire. Ces recherches se concentrent sur l'étude de l'émission de paires de photons d'une telle source, et du mélange à quatre ondes à leur origine. Nous soulignons le manque d'une description quantitative correcte des phénomènes non linéaires à l'origine des paires dans les modèles existants, et en proposons un se basant sur le champ D pour y parvenir. Nous mettons expérimentalement en évidence l'inconsistance avec la forme de spectre usuellement attendue les sources de paires de photons. Pour l'expliquer, nous développons un modèle rendant compte de la non-uniformité du guide, soit la variation de ses propriétés de propagation sur sa longueur. Par une approche analytique initiale simple de cette caractéristique, nous exposons l'étalement du spectre et la diminution du taux maximum d'émission de paires. Une description numérique par morceaux apporte une description plus proche de la réalité et met en lumière la très forte sensibilité du spectre à la non-uniformité. Un autre effet de cette dernière se traduit par la différenciation du spectre selon le sens de propagation de la lumière dans le guide. Lors de l'intrication en polarisation des paires dans un dispositif de type boucle Sagnac, cette non-réciprocité dégrade la visibilité des paires. Pour compenser cet effet, nous proposons une solution simple de symétrisation du profil des fibres à leur fabrication, appuyée par de premiers résultats encourageants. Cette étude ouvre la voie à la prise en compte des non-uniformités inhérentes aux guides réels, impactant fortement leur émission de paires de photonsPhoton-pair sources are a basic block for implementation of quantum information and telecommunication. A microstructured fibered source with liquid core induce a Raman scattering noise reduction, and at the same time allows a simple and lossless coupling to telecom network, with an engineering of its emission properties through the structure and liquid choices. This work focus on four-wave mixing leading to photon pairs emission in such a source. As existing models lack a correct emph{quantitative} description of nonlinear phenomena for pairs emission, we propose here one based on the D field to do so. We show a mismatch between the spectrum form usually expected and the experimental one. To explain this, we develop a model describing the effects of guide nonuniformity, meaning variation of its propagation properties along itself. Through an initial and simple analytical approach, we demonstrate the spectrum spreading and the diminution of the maximum of emission pairs rate. With a piece-wise numerical description for real guides, we highlight the very strong sensitivity of the emission spectrum towards nonuniformity. Another effect arising from this feature is the spectrum differentiation depending on the propagation direction within the guide. Upon pairs polarization entanglement by inserting the guide into a Sagnac loop interferometer, such nonreciprocity induces a deterioration of pairs visibility. In order to counteract this effect, we propose, based on first encouraging results, a simple solution involving a symmetrization of fibers profile during their manufacture. This study paves the way for taking into account inherent nonuniformity of real waveguides, which strongly impacts their photon pair emission
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MORAES, JAIR R. de. „Estudo da preparação de microcristais de LiLa(WOsub(4))sub(2):TRsup(3+) para aplicações fotônicas“. reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10510.
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Made available in DSpace on 2014-10-09T12:41:19Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:03Z (GMT). No. of bitstreams: 0
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:08/10721-9
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Longueteau, Emmanuel. „Synthèse d'ouverture à 3 télescopes : Etude et caractérisation des sources d'erreurs sur les données interférométriques“. Limoges, 2002. http://www.theses.fr/2002LIMO0020.
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Le développement des interféromètres stellaires nécessite une phase d'étalonnage des instruments en laboratoire. La connaissance et le contrôle des objets étudiés est obligatoire pour la caractérisation de défauts instrumentaux. Ce manuscrit présente différentes sources de dégradations de mesures obtenues sur deux interféromètres stellaires de laboratoire réalisés à l'IRCOM. L'interféromètre ISTROG, réalisé uniquement à l'aide de composant d'optique guidée, a révélé, lors son étalonnage, une erreur systématique résultant des effets différentiels de dispersion chromatique sur les données interférométriques. Ce manuscrit détaille l'éxpérimentation et la modélisation de ce phénomène. Linterféromètre OAST2 financé par l'Agence Spatiale Européenne et développé initialement pour démontrer la faisabilité de l'imagerie haute résolution par synthèse d'ouverture, a permis de mettre en évidence l'influence de la directivité des antennes optiques associée aux imprécisions de pointage dont elles font l'objet : plus les ouvertures sont larges, plus les antennes sont directives, et plus les mesures interférométriques sont succeptibles d'être erronées. D'autre part, cet instrument a aussi fait l'objet d'investigations portant sur la détection en régime de comptage de photons appliquée à ce type d'interféromètre. Une méthode de mesure de contraste et de clôture de phase a pu être établie. Elle intègre une correction de l'erreur systématique sur les données interférométriques résultant de la quantification de la détection.
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Feve, Jean-Philippe. „Existence et symétrie des interactions à 3 et 4 photons dans les cristaux anisotropes : méthodes de mesure des paramètres affectant les couplages à 3 ondes : étude de KTP et isotypes“. Nancy 1, 1994. http://www.theses.fr/1994NAN10038.
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Les propriétés optiques linéaires sont très importantes dans l'expression des propriétés optiques non-linéaires: nous étudions la localisation des accords de phase colinéaires et non colinéaires pour les interactions à 3 photons. L'extension du formalisme des facteurs de champs aux interactions à 4 ondes met en évidence les 7 types d'accord de phase. Il permet un traitement unifié des interactions de somme et différence de fréquence. La fiabilisation des mesures des propriétés optiques linéaires et non-linéaires nécessite la mise au point de méthodes spécifiques. KTP et ses isotypes constituent un banc d'essai privilégié pour cette méthodologie. La dispersion en fréquence des axes optiques apporte une précision importante à la dispersion des indices de réfraction. Nous développons une méthode de prospection du profil longitudinal gaussien d'un faisceau laser par une lame mince doubleuse de fréquence. La grandeur et le signe relatif des coefficients non-linéaires de KTP sont mesures en accord de phase en régime continu, démontrant l'importance du régime temporel du laser pour cette détermination. Nous étudions les paramètres régissant les conditions de focalisation: atténuation par la double réfraction et dommage optique. L'ajustement des conditions d'accord de phase est réalisable par les effets électro-optique ou thermooptique ou par substitution d'éléments chimiques. Pour le triplage de fréquence indirect à 0,44 m, l'existence d'accord de phase non critique à température ambiante est démontrée dans les solutions solides ktiop#1##yas#yo#4
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D'Hose, Nicole. „Étude expérimentale des mécanismes de photoproduction de pions et de photodésintégration sur l'hélium-3 dans la région de la résonance delta (1232)“. Paris 11, 1988. http://www.theses.fr/1988PA112406.
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Le but de ce travail est l'étude des mécanismes d'absorption d'un photon réel mettant en jeu un, deux ou trois nucléons dans le noyau ³He, dans la région de la résonance Δ (1232). La sélection de ces mécanismes est réalisée par le choix de la réaction : la photo-production de pions s'effectue préférentiellement sur un nucléon quasi-libre du noyau, alors que la photodésintégration sans émission de pions implique l'absorption par plusieurs nucléons corrélés. Ces expériences ont été réalisées à l'Accélérateur Linéaire de Saclay sur la ligne de faisceau de photons quasi- monochromatiques obtenus pur annihilation en vol de positrons. Les spectres de pions et de protons sont mesurés à l'aide de spectromètres magnétiques pour des angles d'émission compris entre 20° et 72° et pour des énergies de photons comprises entre 210 et 450 MeV. Pour chaque cinématique étudiée, la mesure des réactions H(γ,π )n et D(γ,p)n a permis la comparaison des sections efficaces sur l'hélium-3 à celles des réactions élémentaires. Nos résultats expérimentaux sont comparés à des calculs théoriques utilisant des fonctions d'onde réalistes de l'hélium-3. Les modèles effectués dans le cadre de l'approximation d'impulsion en traitant explicitement le mouvement de Fermi ne permettent pas de reproduire la photo-production cohérente de pions ³He(γ,π)³H. De même la photo-production quasi-libre de π⁺ et π⁻ reste surestimée par les prédictions théoriques existantes, qui ne prennent que partiellement en compte les interactions dans l'état final. Pour la photodésintégration sans émission de pions de l'hélium-3, les calculs incluent les corrélations à courte portée et les courants d'échange mésiques ainsi que les interactions dans l'état final. Ils reproduisent assez bien les spectres mesurés dans la région où l'absorption par une paire de nucléons est dominante mais sous-estiment les données dans la région d'impulsion maxi male. L'introduction d'effets à trois corps semble indispensable pour expliquer ce résultat expérimentalThe goal of this work is the study in 3Jie of the rnechanisms involved in the absorption of photons in the (1232) resonance region. One, two, or three nucleons participate in this absorption depending upon the specific reaction induced : pion photo-production proceeds preferentially through absorption on a simple nucleon, whereas in photodisintegration without pion emission the photon is absorbed by few-nucleon subsystems. The experiments were performed at the Saclay Linear Accelerator with the quasi-mono-chromatic in flight positron annihilation photon beam. Pion and proton spectra were measured using magnetic spectrometers for several angles from 20° to 72°. Photon energies were in the 210 - 450 MeV range. For each kinematical setting a corresponding measurement of the reactions ll(ynl-)n and D(yp)n allowed the comparison of the helium-3 cross sections to these more elementary ones. Our experimental results are compared to theoretical calculations utilizing realistic He wave functions. Impulse approximation models which incorporate the nucleon fermi motion cannot reproduce the pion coherent photo-production 31le( yn+). The theoretical predictions of a charged pion quasi - free photo-production which take into account only partially the final state interactions overestimate the experimental cross sections. For 3ue photo-desintegration, without 1r production the calculations include short range correlations, mesonic exchange currents, and final state interactions. They agree reasonably well with the measured spectra in the region where absorption by a nucleon pair dominates, but they underestimate the cross section in the high momentum tip region. Inclusion of three body effects appears necessary in order to explain this experimental feature
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Andraud, Chantal. „Defauts d'empilement dans le materiau unidimensionnel cscdbr::(3) : etude spectroscopique“. Paris 6, 1987. http://www.theses.fr/1987PA066140.
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L'etude des proprietes optiques de cscdbr::(3) a montre l'existence de centres br::(2)**(2-). L'excitation des echantillons par des rayonnements ionisants (rx, faisceau d'electrons) et des experiences d'absorption a deux photons ont permis d'associer les differentes bandes d'emission et d'absorption observees a des transitions appartenant a ces centres. L'existence de ces centres br::(2)**(2-) est attribuee a la presence de defauts d'empilement. L'effet d'une pression hydrostatique, le dopage par des ions pb**(2x) et le recuit des cristaux confirment l'hypothese
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TOUAHRI, DRISS. „Developpement d'une chaine de synthese de frequences de l'infrarouge au visible : application a la mesure de la frequence de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) du rubidium (#8#5rb) a 385 thz (778 nm)“. Paris 11, 1996. http://www.theses.fr/1996PA112262.
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L'objet de cette these est la mesure de la frequence absolue de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) du rubidium a 385 thz (778 nm) sur laquelle est asservie une diode laser. Les performances metrologiques de ce dispositif sont: stabilite: 4 x 10#-#1#3 #-#1#/#2 repetabilite: 5 x 10#-#1#3 reproductibilite: 2 x 10#-#1#2 elles en font un candidat tres prometteur en tant qu'etalon secondaire de frequence dans le domaine visible. La frequence de cette transition est mesuree a l'aide d'une chaine de multiplication de frequence. La frequence d'un laser a co#2 stabilisee sur une transition de la molecule de oso#4 a 29 thz, est multipliee par 13 en quatre etapes, a l'aide de dispositifs non-lineaires (une diode mim et trois cristaux d'aggas#2). Les frequences de trois dispositifs similaires ont ete mesurees simultanement. Deux sont localises au lptf/observatoire de paris. Le troisieme situe au laboratoire kastler-brossel (ens/paris vi) est relie a la chaine de mesure du lptf par une fibre optique longue de 3 km. Ce laser etalon est utilise comme reference de frequence pour l'etude spectroscopique a tres haute resolution de l'atome d'hydrogene. La resolution de la chaine de frequence developpee au lptf est meilleure que 1 x 10#-#1#3. La mesure est limitee principalement par la stabilite des etalons de frequence a rubidium. La valeur de la frequence de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) ainsi mesuree est: = 385 285 142 378. 280 2 khz l'incertitude de 2 khz prend en compte les ecarts observes entre les trois dispositifs
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Maksymov, Ivan. „Modelling of photonic components based on ÷(3)nonlinear photonic crystals“. Doctoral thesis, Universitat Rovira i Virgili, 2006. http://hdl.handle.net/10803/8474.
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En esta tesis se llevó a cabo un estudio de diversas propiedades de los cristales fotónicos 1D y 2D no lineales de tercer orden y de cómo se pueden aplicar dichas propiedades al desarrollo de dispositivos totalmente ópticos (por ejemplo, limitadores y conmutadores, compuertas lógicas, transistores ópticos, etc.). Se propuso una aproximación numérica para calcular las características básicas de los cristales fotónicos no lineales como, por ejemplo, el diagrama de bandas o la transmisión. La aproximación numérica presentada en la tesis tiene ciertas ventajas útiles para cualquiera que diseñe dispositivos ópticos basados en cristales fotónicos no lineales. El sofware desarrollado a base de esta aproximación numérica ha permitido diseñar y simular numéricamente un conmutador totalmente óptico cuyas prestaciones son superiores a las de dispositivos optoelectrónicos convencionales.This dissertation represents a summary of a study of different properties of 1D and 2D third-order nonlinear photonic crystals. It is shown how these properties can be utilized to develop various all-optical devices (e.g. optical limiters and switches, logical gates, optical transistors, etc.) In the dissertation, a novel numerical approximation has been proposed for analyzing the basic characteristics of the nonlinear photonic crystals like dispersion characteristics or transmittance curves. This numerical approximation possesses some important advantages useful in designing all-optical devices based on nonlinear photonic crystals. The software based on its algorithm has allowed to design and simulate a high-production all-optical switching device.
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Melo, Emerson Gonçalves de. „Integração monolítica de guias de onda, curvas e junções em Y baseados em cristais fotônicos planares de silício e com baixas velocidades de grupo“. Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-15012018-150947/.
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A fotônica em silício é um campo de pesquisas emergente com grande potencial para contribuir com a resolução de alguns dos problemas tecnológicos da atualidade. O gargalo imposto por interconexões metálicas na expansão da taxa de transmissão de dados em sistemas de comunicação como os de computadores de alto desempenho talvez seja um dos maiores desafios a serem superados. A propagação de luz em baixas velocidades de grupo e com controle de dispersão é uma das linhas de pesquisa atuais nas quais se busca explorar de forma mais eficiente as propriedades ópticas do silício, e assim, aumentar a compatibilidade entre componentes fotônicos e a tecnologia CMOS (Complementary Metal- Oxide-Semiconductor) por meio da diminuição das dimensões e do consumo de energia de componentes ópticos ativos. Dessa forma, espera-se diminuir os custos de fabricação e viabilizar a produção em larga escala de dispositivos integrados optoeletrônicos, que poderiam ser utilizados em sistemas de comunicação de curtas distâncias e assim ampliar a largura de banda disponível. Investigações recentes têm demonstrado que a fabricação de dispositivos baseados em cristais fotônicos planares possui grande potencial para controlar simultaneamente a velocidade de grupo e a dispersão, além de permitir a redução do tamanho de elementos como curvas, divisores de potência e cavidades ressonantes devido ao efeito do confinamento dos campos através do bandgap fotônico. Dessa forma, esse trabalho aborda um estudo sobre a integração monolítica entre guias de onda, curvas de 60º e junções em Y que operam em baixas velocidades de grupo e com reduzida dispersão, construídos em cristais fotônicos planares formados por uma matriz periódica de furos em uma membrana de silício suspensa em ar. Essa investigação englobou atividades bastante intensivas, tanto de simulações por métodos numéricos, como de processos de fabricação dedicados à nanofotônica, assim como de caracterizações ópticas. Ao longo das discussões são identificados e analisados os mecanismos que afetaram de forma mais crítica a eficiência dos dispositivos propostos. Também foram avaliados os maiores problemas enfrentados nos processos de fabricação, e suas possíveis soluções foram apontadas. Os resultados demonstraram a possibilidade teórica de realizar tal integração de forma eficiente. O melhor entendimento sobre a relação entre a dispersão e os parâmetros geométricos dos guias de onda permitiram modelar curvas e divisores de potência que exibiram, respectivamente, larguras de banda em torno de 56 e 40 nm, cobrindo regiões do espectro com elevados índices de grupo. Foi possível fabricar cristais fotônicos com uma qualidade próxima das já reportadas na literatura sobre o tema e assim foram estabelecidas bases bastante sólidas para a fabricação de tais dispositivos localmente, sem a necessidade expressa de acessar centros de fabricação no exterior.Silicon photonics is an emerging research field that has great potential to contribute to solving some of the technological problems nowadays. Maybe, one of the greatest challenges to be overcome is the bottleneck imposed by electrical interconnections in the expansion of the bandwidth of communication systems such as those of high performance computers. Slow light propagation in dispersionless media is a hot topic in the current research fields that seek to more efficiently explore the silicon optical properties, and thus, increase the compatibility between photonic components and CMOS technology by decreasing the footprint and power consumption of active optical components. This way, the manufacturing costs it is expected to be reduced by making the large-scale production of integrated optoelectronic devices feasible, and so, they could be used in short distance communication systems to expand the available bandwidth. Recent researches has also shown that photonic crystal slab waveguides are very promising to simultaneously control group velocity and devices dispersion, as well as in the reduction of the size of elements such as bends, power splitters and nanocavities due to the fields confinement through the photonic bandgap effect. Thus, this work addresses a study of the monolithic integration of slow light and dispersionless waveguides, 60º bends, and Y-junctions fabricated in air-bridge photonic crystal slabs formed by the drilling of a periodic array of air holes in a silicon membrane. The research was accomplished with intensive activities in numerical simulations, as well as in nanophotonic manufacturing processes, and optical characterizations. Throughout the discussions were identified and analyzed the mechanisms that more critically affected the devices efficiency. The major problems faced in the manufacturing processes were also evaluated, and their possible solutions were pointed out. The results demonstrated a theoretical possibility of performing such integration more efficiently. Having a better understandment about the relation between the photonic crystal waveguides geometrical parameters and their dispersion allowed the modeling of bends and power splitters which exhibited 3 dB bandwidths that covered, respectively, ranges around 56 and 40 nm, along spectral regions with very high group indices. It was possible to fabricate photonic crystals with a quality close to those already reported in the literature on this subject and thus, very solid bases were established for the manufacture of such devices locally, without the necessity of accessing manufacturing centers abroad.
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Pouya, Caroline. „Investigating naturally occurring 3-dimensional photonic crystals“. Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3744.
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This thesis describes my research into the highly tuned naturally occurring 3D photonic structures that are present on a selection of insects. The experimental and theoretical work presented in this thesis was performed in both the optical and microwave regimes. The work performed in the optical regime included both the geometric and optical characterisation of the native photonic structures present on the beetle Eupholus magni cus and the butter y Parides sesostris. The native photonic structures of these organisms were probed in order to determine their photonic responses and also to ascertain their geometries and structural classes. In cases where the geometry of a photonic crystal system has been determined, I have performed additional theoretical analysis of the structure to establish how it might be optimised for a particular optical function. The overall aim of the work performed in the optical regime is to further the understanding of the photonic structural designs present on a selection of beetles and butter ies, by both identifying and characterising their underlying structural geometries and consequent photonic responses. Eupholus magni cus is a species of weevil that produces its coloured appearance from photonic structures that are present on its outer wing casing, producing a striped coloured pattern. The photonic structures that I discovered were present on this weevil were found to be contrasting in structural order. I used a wide-ranging variety of experimental and theoretical techniques in order to perform an extensive electromagnetic and structural characterisation of these contrasting structures. The two contrasting photonic mechanisms employed by E. magni cus were found to produce a similar optical response in terms of angle-independent colour whilst re ecting di erent coloured hues. Parides sesostris is a species of butter y that uses a gyroid photonic crystal structure, contained within scales, to produce green coloured patches on the dorsal side of its wings. In addition to this, P. sesostris uses embellishments to its scale morphology in order to produce a highly tuned angle-independent optical response. The optical e ects brought about by these structural embellishments were investigated with optical experimental techniques and they were found to di usely scatter light and aid iridescence suppression. In addition to this, theoretical modelling was performed on a variety of gyroid geometries. The gyroid photonic structure found in the wing scales of P. sesostris was determined to be highly optimised to re ect the largest range of frequencies possible from this geometry, also aiding iridescence suppression. In addition to this, the arrangement of gyroid arrays within each scale was determined to produce the highest intensity possible by using the smallest possible number of unit cells. In addition to the optical characterisations of the organic naturally occurring photonic structures found on these organisms, I also synthetically replicated the three fundamental naturally occurring triply periodic bicontinuous cubic photonic crystal structures for experimental and theoretical electromagnetic characterisation in the microwave regime. The microwave regime was selected to perform the characterisation as a high-resolution fabrication method can be employed in order to produce millimetre-scale structures, suitable for probing in this wavelength regime. A high resolution fabrication method is an absolute requirement for accurately replicating the complex geometries of constant mean curvature structures and retaining a high level of detail. I have electromagnetically characterised these three structures with the aim of gaining a better understanding of their polarisation-dependent photonic stop-band responses. Speci cally, I have identi ed the origin of, and the dispersion of, photonic stop-bands produced by each unique structural geometry. I have principally focused on the characterisation of the electromagnetic responses of these structures, how they di er from each other and also why a linear polarisation dependence arises from these 3D photonic structures. In addition to this I have related the electromagnetic responses of these structures to analogous optical structures that naturally occur on the wings of the butter y P. sesostris and elytra of the weevil E. magni cus. With this I aimed to gain a better understanding of the origin of the optical e ects they provide the host biological system. This includes the characterisation of the gyroid photonic crystal structures, chosen to mimic that found in P. sesostris wing scales. The results from this were also subsequently used in the optical optimisation examination performed on the P. sesostris gyroid. Finally, I have investigated a dynamic aspect of the 3D gyroid photonic crystal, formed from a constant mean curvature surface. A compliant gyroid structure was fabricated for analysis in the microwave regime and a systematic compression force applied to it. I have measured the electromagnetic response of this compliant gyroid at each compression distance. Alongside this, I used theoretical modelling to electromagnetically characterise an analogous system under compression. In doing this I have identi ed the origin of the novel and complex photonic band-shifting behaviour produced by this 3D geometry.
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Sunter, Kristen Ann. „Optical Modeling of Superconducting Nanowire Single Photon Detectors“. Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13106421.
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Superconducting nanowire single photon detectors (SNSPDs) can detect single photons or low levels of infrared light in applications that require high speed and low timing jitter, such as integrated circuit analysis. Most applications also require a high device detection efficiency (DDE), but the DDE of SNSPDs is limited by many factors. A good optical design with an integrated optical cavity and dielectric layers can increase the absorptance of 1550-nm light in the active area to over 90%. Therefore, optical modeling using the transfer matrix method was used to guide the design and fabrication of high-efficiency detectors with a measured DDE of over 70%. In addition, finite element analysis was used to simulate the effect of adding different types of optical antennas to SNSPD designs to increase their active area without compromising their speed, and the fabrication of antennas integrated with nanowires achieved sub-10 nm gaps between features.
Thin films of niobium nitride, the starting material of the SNSPDs, were investigated using several techniques for thin film characterization, including x-ray diffraction, Auger electron spectroscopy and x-ray photoelectron spectroscopy. Optical setups based on reflectometry and transmittometry were built to determine the film thickness more accurately than deposition time for optical modeling and to provide feedback on the deposition conditions. The optical setups are able to provide reproducible and precise thickness measurements to within 0.1 nm.Engineering and Applied Sciences
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Buzbee, Michael Laurence. „3-Dimensional Photonic Circuits for Quantum Information Processing“. University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461970290.
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Shneidman, Anna Vitalyevna. „Photonics in Low Index Media“. Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493317.
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Many applications in photonics rely on the ability to confine light in small volumes. This is commonly achieved by utilizing two or more materials with a large refractive index contrast, such as silicon and silicon dioxide, diamond and air, etc. However, techniques available to fabricate sub-wavelength structures in these materials, including electron beam lithography followed by etching, or focused ion beam milling, are often costly and time consuming. In addition, there are few options to tune the optical response of fabricated devices. A panoply of new photonic applications can be unlocked by taking advantage of the versatility of so-called ”soft” materials. Though they typically have a lower index contrast, they can be manipulated by a variety of accurate and rapid techniques, in addition to the standard cleanroom approaches. Polymers and colloids are thus attractive materials for photonics because of the large toolbox available for their fabrication on length scales comparable to the wavelength of light. In this thesis, photonic applications based on three different platforms are presented, each of which comes with a unique fabrication approach: (1) colloidal self-assembly of three dimensional periodic structures, (2) roll-to-roll nano-imprint lithography (R2RNIL) of polymers towards functional photonic devices such as colorimetric sensors and on-chip spectrometers and (3) biopolymer (silk) microspheres. Spherical polystyrene colloids are self-assembled into a 3D face-centered cubic (fcc) lattice and are embedded in SiO2 or TiO2. Once the colloids are burnt out, a porous structure which preserves the fcc arrangement remains. It possesses optical properties of a photonic crystal, which are modified by infiltrating liquids that create partially filled patterns throughout the structure. The evolution of the photonic properties are investigated as deviations from perfect periodicity increase. Furthermore, the opportunity to realize optically pumped lasers (e.g. band edge or random lasers) in this material platform is discussed.
Polymers have numerous desirable properties for the future of photonic devices. However, they suffer from a low refractive index contrast. The ability to create functional polymer photonic devices for chip-scale operation is demonstrated, and simulations and experiments are conducted for various photonic components, including waveguides, gratings, and ring resonators. Two dimensional photonic crystals with 100 nm feature sizes are produced by the R2RNIL and they display tunable structural color. Photonic elements for on-chip photonic integration are also fabricated with R2RNIL. S-shaped waveguides are coupled to ring resonators and ring resonator quality (Q) factors close to 60,000 are measured. A grating coupler setup is built and tested by measuring silicon-on-insulator devices featuring rings coupled to the waveguide, and Qs of 20,000- 30,000 are obtained.
Silk is a special polymer in the sense that it is biocompatible and thus interfacing photonic components with internal organs can be envisaged. Here, investigations of silk’s photonic properties in the context of microspheres are performed. A tapered fiber is used to couple in and out of the whispering gallery optical resonances of silk microspheres. Qs of 500-1000 are determined from transmission measurements; simulations and scanning electron micrographs confirm that the reduction in Q is due to deviations from a completely spherical shape.Chemistry and Chemical Biology
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Romijn, Elisabeth Inge. „Development of 3-D Quantitative Analysis of Multi-Photon Microscopy Images“. Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18425.
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Motivation: Cartilage is a robust but flexible connective tissue found in most joints of the body. The collagen fibres present in the extracellular matrix of cartilage contribute to its tensile strength and stiffness. The purpose of this study is to develop and implement methods to determine the orientation and anisotropy of collagen fibres in 3-D images gen- erated with multi-photon microscopy. The motivation behind developing these techniques is to improve the foundation for further studies on understanding the characteristics of the cartilage matrix. This in turn would give a better foundation for developing artificial matrices and mechanical models, as well as improve diagnostics.Material and methods: The two methods developed in this study are based on analysing the frequency domain. One is an expansion of a previous developed method by Chaudhuri et al. [1]. This method is based on evaluating the average intensity at different directions in the frequency domain. The direction with the least average intensity is equivalent to the direction of the fibres. The other method is based on thresholding the frequency domain according to intensity followed by fitting an ellipsoid to the remaining data set. The direction of the collagen fibres is equivalent to the direction of the shortest axis of the ellipsoid. These methods are called the sector and ellipsoid method, respectively. To determine how robust these methods are a series of tests were developed. The focus of these tests was to determine if the methods are rotational invariant and if the results are influences by different preprocessing techniques. These preprocessing techniques are: median filtering, deconvolution and skeletonization of the original image containing the collagen fibres. It is also important to determine the sensitivity of the ellipsoid method according to the chosen threshold value. In addition data generated fibres and frequency domains were made to determine the accuracy of the methods.Results and conclusion: The sector method was not very robust. For most cases there is not one specific direction that has the least average intensity in the frequency domain. Instead there is a quite large minimum area. The ellipsoid method shows promising results. It managed to find the correct direction both for the data generated data sets, but also for the real images. It seems like no preprocessing nor frequency filtering, except for thresholding, is needed to still find the correct direction and its anisotropy. The only remark is that the automatically chosen threshold value was to low for one of the samples. This can probably be improved by making a slight change in the process for choosing a threshold value.
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Sun, Chengwei. „First measurement of the reaction helium-3(photon,proton -proton)neutron“. W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539623791.
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Differential cross sections for the {dollar}\sp3{dollar}He({dollar}\gamma{dollar},pp)n reaction were measured with a bremsstrahlung beam for kinematics selected in the quasi-free two-nucleon region with neutron recoil q{dollar}\sb{lcub}\rm n{rcub}\approx{dollar} 0. Five photon energy points were taken between 200 and 440 MeV. The two proton detectors were positioned in such a way that the angle of one proton, in the CM of the pp pair, relative to the photon direction is 75{dollar}\sp\circ{dollar}. The data confirm the predicted quenching of the cross section. In the photon energy region from 310 to 440 MeV the data are in agreement with a theoretical prediction based on a diagrammatic description of the process. at lower energies (200 to 310 MeV) the data are about 40% to 70% higher than the predictions. However the shape of the proton momentum spectrum is reproduced when three body mechanisms are included.
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Tang, Xiaofeng. „The fabrication of 3-D photonic band gap structures“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/43305.
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Thesis (Elec. E.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 85-88).
by Xiaofeng Tang.
Elec.E.
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Damon, Vianney. „Filtrage programmable et mémoire quantique dans Er 3+ YSO“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00877060.
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Les ions de terres rares en matrice cristalline, refroidis à très basse température, offrent des propriétés remarquables pour le traitement analogique du signal sur porteuse optique. L'élargissement inhomogène du spectre d'absorption peut en effet atteindre plusieurs centaines de gigahertz alors que la largeur homogène des raies d'absorption des ions individuels ne dépasse pas quelques kilohertz. Par pompage optique il est alors possible de modifier à volonté le profil du spectre d'absorption. On dispose ainsi d'un filtre programmable présentant à la fois une très grande bande passante, donnée par la largeur inhomogène, et une excellente résolution, fixée par la largeur homogène. Une raie d'absorption étroite correspond à un état de superposition quantique de longue durée de vie. C'est sous cet angle, celui des transitoires cohérents, et spécifiquement celui des échos de photons que nous abordons les propriétés du filtre programmable. Dans la première partie de la thèse, le filtre est programmé comme un élément dispersif. Il permet d'atteindre des taux de dispersion inaccessibles aux dispositifs optiques conventionnels, tels que les fibres optiques. Nous l'utilisons comme un composant de lentille temporelle, en vue de produire des signaux de forme arbitraire. Par rapport à des dispositifs d'optique conventionnels, on gagne plusieurs ordres de grandeurs en termes de produit temps x bande passante. Après avoir exploité l'écho de photon dans un contexte de filtrage linéaire, nous tirons parti de ses propriétés de très forte non-linéarité dans la seconde partie de la thèse. Cette fois nous cherchons à capturer un signal lumineux de très faible intensité, à le convertir en état de superposition atomique, puis à le restituer dans son état lumineux initial. Cela suppose en particulier d'empêcher les effets d'émission spontanée ou stimulé qui nuisent à la fidélité de la restitution. Pour ce faire, nous proposons un nouveau protocole que nous avons appelé " Revival Of Silenced Echo " (ROSE)
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Yilmaz, Ercan. „Characteristic X-ray, Photoelectron And Compton-scattered Photon Escape From A Hpge Detector“. Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/3/1210061/index.pdf.
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Escape of photoelectrons, Compton-scattered photons and Ge X-rays from a HPGe detector was studied as a function of energy in the range 8-52 keV. A variable-energy source producing Cu, Rb, Mo, Ag, Ba, and Tb X-rays was used. All three mechanisms for energy loss were observed in the same experiment for Ba and Tb, while only X-ray and photoelectron escapes were evident in the spectra for Ag, Mo, Rb, and Cu. Spectral features and possible mechanisms for partial energy deposition were investigated. A Monte Carlo program was used to simulate the relevant interactions and to estimate the escape probabilities.
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Hui, Pui Chuen. „Optomechanics and nonlinear mechanics of suspended photonic crystal membranes“. Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13068536.
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The recent demonstration of strong interactions between optical force and mechanical motion of an optomechanical structure has led to the triumphant result of mechanical ground-state cooling, where the quantum nature of a macroscopic object is revealed. Another intriguing demonstration of quantum physics on a macroscopic level is the measurement of the Casimir force which is a manifestation of the zero- point energy. An interesting aspect of the Casimir effect is that the anharmonicity of the Casimir potential becomes significant when the separation of microscale objects is in the sub-100nm regime. This regime is readily accessible by many of the realized gradient-force-based optomechanical structures. Hence, a new avenue of probing the Casimir effect on-chip all-optically has become available. We propose an integrated optomechanical platform, consisting of a suspended photonic crystal membrane evanescently coupled with a silicon-on-insulator substrate, for (i) measuring the Casimir force gradient and (ii) counteracting the attractive force by exerting a resonantly enhanced repulsive optical gradient force. This thesis first presents the full characterization of the optomechanical properties of the system in vacuo. The interplay of the optical gradient force (optomechanical coupling strength \(g_{om}/2\pi=- 66GHz/nm\)) and the photothermal force manifested in the optical spring effect and dynamic backaction is elucidated. Static displacement by the repulsive force of 1nm/mW is also demonstrated.
In the second part of the thesis, the nonlinear mechanical signatures upon a strong coherent drive are reported. By resonantly driving the photonic crystal membrane with a piezo-actuator and an optical gradient force, we observed mechanical frequency mixing, mechanical bistability and non-trivial interactions of the Brownian peak with the driving signal. Finally we present our recent progress in establishing electro- static control of individual photonic crystal membranes to reduce and calibrate the electrostatic artifact which plagues Casimir measurements.
The results discussed in this thesis point towards an auspicious future of a complete realization of a Casimir optomechanical structure and novel applications with nonlinearity afforded by the Casimir force and the optical gradient force.Engineering and Applied Sciences
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Nunes, Luiz Antonio de Oliveira. „Espectroscopia de dois fotons do ion Gd+3 em estruturas perovskitas“. Universidade de São Paulo, 1988. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-10032008-113404/.
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Através da absorção de um e de dois fótons estudamos as diferentes transições do íon \'Gd POT.+3\' e GGG. Utilizando técnicas espectroscópicas com laser pulsado e laser contínuo, analisamos a influência do campo cristalino sobre o íon. Estes resultados estão em concordância com as previsões advindas da teoria de grupo. A partir da análise dos espectros de luminescência das amostras de GdAl\'O IND.3\', conseguimos detectar pequenos traços de impurezas nas mesmas. Não conseguimos detectar nenhuma anomalia nos espectros obtidos, de modo a não acreditarmos na existência de alguma interação Gadolínio - Galdoíno, acima da temperatura de transição de fase. Laser de corante contínuo de alta resolução, laser de corante pulsado foram construídos para a realização dos experimentos. Também desenvolvemos os equipamentos eletrônicos envolvidos.The different transitions of \'Gd POT.3+\' ion in samples of GdAl\'O IND.3\' and GGG were studied by means of the absorption of one and two photons. The crystalline field influence an the ion was studied by using spectroscopic techniques with pulsed laser as well as continuous laser. These results are in agreement with the group theory prediction. From the luminescence spectrum of this sample little impurities aspects in the GdA1\'O IND.3\' sample were detected. No anomaly was detected in the spectra obtained so that we believed there is no \'Gd POT.3+\'-\'Gd POT.3+\' interaction above the phase transition temperature. High resolution continuous dye laser and pulsed die laser were built up to carry out the experiments. The electronic equipment used in the experiment was developed by us.
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Zoubir, Arnaud. „TOWARDS DIRECT WRITING OF 3-D PHOTONIC CIRCUITS USING ULTRAFAST LASERS“. Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3907.
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The advent of ultrafast lasers has enabled micromachining schemes that cannot be achieved by other current techniques. Laser direct writing has emerged as one of the possible routes for fabrication of optical waveguides in transparent materials. In this thesis, the advantages and limitations of this technique are explored. Two extended-cavity ultrafast lasers were built and characterized as the laser sources for this study, with improved performance over existing systems. Waveguides are fabricated in oxide glass, chalcogenide glass, and polymers, these being the three major classes of materials for the telecommunication industry. Standard waveguide metrology is performed on the fabricated waveguides, including refractive index profiling and mode analysis. Furthermore, a finite-difference beam propagation method for wave propagation in 3D-waveguides is proposed. The photo-structural modifications underlying the changes in the material optical properties after exposure are investigated. The highly nonlinear processes of the light/matter interaction during the writing process are described using a free electron model. UV/visible absorption spectroscopy, photoluminescence spectroscopy and Raman spectroscopy are used to assess the changes occurring at the atomic level. Finally, the impact of laser direct writing on nonlinear waveguide applications is discussed.Ph.D.
Other
Optics and Photonics
Optics
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Aldousari, Hanan. „Study of 2-to-3 photon annihilation using hydrophilic material as hypoxic tumour phantom“. Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616952.
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The use of three gamma annihilation as a new PET molecular imaging modality which can predict tumour hypoxia was proposed by Kacperski and Spyrou in 2004. The positronium and its annihilation, could then serve as an oxygen-sensitive marker. The relative magnitude of three photon annihilation is increased in an oxygen deficient environment. The main questions addressed in this thesis are the potential use of the lanthanum bromide LaBr3: Ce (5%) scintillator detector for three-photon positron annihilation measurements. Also, the optimum source-to-detector distance that achieves good efficiency and sensitivity of the measurements. The other question is finding the best method to prepare in vitro three types of hypoxic samples (mineral water, defibrinated horse blood and semm). In addition, the suitability of the hydrophilic material is examined in terms of hydration behaviour, radiation and physical properties, for use as a phantom that represents the hypoxic tumour in the three-photon positron annihilation measurements. The main critical question is which the best method that could be used to measure the three-photon positron annihilation yields. Also, how does the 3y/2y ratio vary with different oxygen concentrations in different hydrophilic materials? Lanthanum bromide LaBr3: Ce (5%) scintillator detectors have good fast timing resolution, good stopping power and large light output. The LaBr3:Ce (5%) has very good scintillator characteristics, combining high effective Z and density, fast decay time, light emission wavelengths matching that of commonly available photon detectors and excellent energy resolution (~3% at 662 keY). However, it is highly hygroscopic in nature, making it difficult to produce, but its commercial availability has been gradually increasing in recent times. LaBr3: Ce (5%) has come to be accepted for the superior energy resolution it offers. Therefore, LaBr3: Ce (5%) detectors can be considered as the scintillators of choice for determining the yield of 2-and3-y positron annihilation. The characterisation of the detector used was can-ied out in terms of energy resolution and efficiency. The effect of amplifier parameters on the energy resolution was also studied. The 'geometrical solid angles subtended by the source-to-detector distances play an important role in the sensitivity and accuracy of the detector efficiency measurements. Therefore, the efficiency measurements were investigated at various distances to optimise the geometrical solid angle for the LaBr3: Ce (5%) detector for the three photon annihilation measurements. The experimental data were compared with the GATE simulated results obtained. The objective to study the factors that affect dissolved oxygen (DO) in three types of samples (mineral water, defibrinated horse blood and semm) was to investigate the 3y/2y ratio in hypoxic, nOlIDoxic and hyperoxic conditions of tissues for future application in oncology in the detection and quantification of tumour hypoxia. This was achieved by measuring the DO, pH and temperature before, during and after treating the samples with nitrogen, carbon dioxide and ascorbic acid (AnaeroGen). Two methods for the preparation of the in vitro hypoxic samples were investigated and evaluated. Carbon dioxide proved to be most effective for the reduction of DO in the samples. Blood tended to resist DO reduction since it decreased at a much slower rate than in water and semm. Together with the fact that the oxygen level in blood remained low after the end of exposure to the gases and ascorbic acid suggests that the solubility of oxygen in blood depends upon the concentration of haemoglobin as well as upon ligands such as CO2 • CO2 combines with haemoglobin affecting oxygen binding and fonns bicarbonate which further decreases the affinity of haemoglobin to oxygen Hydrophilic materials.
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Pooley, Kathryn Jessica. „Patterned Aqueous Growth of Single Crystalline Zinc Oxide for Photonic Applications“. Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467362.
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Typically a top-down approach is used in the fabrication of functional nanodevices beginning with the bulk material and imposing a two or three-dimensional structure on the material through a combination of lithography and etching. Pre-patterning of a substrate, resulting in the selective growth of a material, has potential for forming three-dimensional device structures in ways that can be more efficient and which can avoid process complexity and process induced damage. In this thesis, the low temperature (90°C) aqueous growth of complex, single crystalline zinc oxide (ZnO) three-dimensional devices through pre-patterned micron and nanometer sized molds is presented. This work focuses on the quality of the single crystalline ZnO material, the constrained growth of ZnO through various sizes and shapes of molds, and the fabrication of several device structures including pillars, rings, and photonic crystals. Due to their single crystalline nature and crystallographically smooth sidewalls, photonic devices created using this growth method have the potential to outperform traditionally fabricated structures in a range of optoelectronic applications.
In addition, metal-oxide interfaces are the critical components of many electrical and optical devices, and it is rare to find epitaxial metal-oxide structures. In this work, the first demonstration of low temperature, epitaxial growth of ZnO on single crystalline gold plates is presented. The quality and structure of the ZnO on the gold plates is investigated using scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy. The epitaxial growth is confirmed using electron backscatter diffraction and transmission electron microscopy. The metal-oxide interfaces fabricated have the potential to be used in a number of technologically important applications. Possible examples include creating high quality electrical contacts on high bandgap materials and improving light extraction from planar LED structures.Engineering and Applied Sciences - Applied Physics
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Makgopa, Bessie Mmakgoto. „Simulation of the irradiation behaviour of the PBMR fuel in the SAFARI-1 reactor / B.M. Makgopa“. Thesis, North-West University, 2009. http://hdl.handle.net/10394/4030.
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Irradiation experiments for the pebble bed modular reactor PBMR fuel (coated fuel particles and pebble
fuel) are planned at the South African First Atomic Reactor Installation (SAFARI-1). The experiments
are conducted to investigate the behavior of the fuel under normal operating and accelerated/accident
simulating conditions because the safe operation of the reactor relies on the integrity of the fuel for
retention of radioactivity.
For fuel irradiation experiments, the accurate knowledge and analysis of the neutron spectrum of the
irradiation facility is required. In addition to knowledge of the neutron spectrum in the irradiation facility,
power distributions and knowledge of nuclear heating values has to be acquired. The SAFARI-1 reactor
boosts operating fluid temperatures of about 300 K. On the contrary, the PBMR can reach temperatures in
up to about 1370 K under normal operating conditions. This calls for design of high temperature
irradiation rigs for irradiation of the PBMR fuel in the SAFARI-1 reactor. The design of this instrument
(rig) should be such that to create an isolated high temperature environment in the SAFARI-1 reactor, to
achieve the requirements of the PBMR fuel irradiation program. The design of the irradiation rig is
planned such that the rig should fit in the existing irradiation channels of the SAFARI-1 reactor, a time
and cost saving from the licensing perspective.
This study aims to establish the know-how of coated particle and pebble modeling in using the Monte
Carlo N-Particle code (MCNP5). The study also aims to establish the know-how of rig design. In this
study, the Necsa in-house code Overall System for the Calculation of Reactors (OSCAR-3), a software
known as OScar 3-Mcnp INTerface (OSMINT) linking OSCAR-3 and MCNP5, also developed at Necsa,
as well as MCNP5 code developed and maintained by the Los Alamos team, are used to calculate
neutronic and power distribution parameters that are important for fuel irradiations and for rig design.
This study presents results and data that can be used to make improvements in the design of the rig or to
confirm if the required operational conditions can be met with the current preliminary rig design. Result
of the neutronic analysis are presented for the SAFARI-1 core, core irradiation channel B6 (where the
PBMR fuel irradiation rig is loaded for the purpose of this study), the rig structure and the pebble fuel are
presented. Furthermore results of the power distribution and nuclear heating values in the reactor core, the
irradiation channel B6, the rig structures and the pebble fuel is also presented.
The loading of the PBMR fuel irradiation rig in core position B6 reduces the core reactivity due to the
fact that the loading of the rig displaces the water moderator in channel B6 introducing vast amounts of
helium. This impacts on the keff value because there will be less neutron thermalization and reproduction
due to the decreased population of thermal neutrons. The rig is found to introduce a negative reactivity
insertion of 46 pcm. The loading of this rig in the core leads to no significant perturbations on the core
power distribution. The core hottest channel is still localized in core channel C6 both with RIG IN and RIG OUT cases. A power tilt is observed, with the south side of the core experiencing reduced assembly
averaged fission power, with correspondingly small compensations from the assemblies on the north side
of the core.
The perturbations on the core assembly averaged fluxes are more pronounced in the eight assemblies
surrounding B6. Core position B6 suffers an 18% neutron flux depression with the loading of the rig. The
fluxes in core positions A5, A6, A7, B5, B7 and C7 are increased when the rig is loading. The largest
increases are noted as 12% in A7, 9% in A6 and 6% in A5 and B7. All the eight core positions
surrounding B6 experience reduced photon fluxes with the loading of the rig. Core position B6 shows a
flux depression of up to 20%, with 10% reduction in core position A6. The remainder seven positions
surrounding B6 shows flux depressions of no more than 5%.
Further on, due to decreased moderation effects, the axial neutron flux in core position B6 is reduced by
20% when the rig is loaded. The energy dependent neutron flux in B6 decreases by 50% in the thermal
energy range with corresponding increases of up to 50% in the resonance and fast energy regions. The
axial and the energy dependent photon flux in core position B6 decreases by up to 20% when the rig is
loaded.
The magnitude of the neutron and photon fluxes is found to have a direct proportion on the neutron and
photon heating values. While the amount of neutron heating in core position B6 increases by one order of
magnitude, when the rig is loaded, the photon heating values increases by up to 60% in the region
spanning ±10cm about the core centerline. The amount of photon heating in the rig structural materials
dominates neutron heating, except in the helium regions of the rig, where neutron heating dominates
photon heating. In the fuel region of the pebble, fission heating (3803W) largely dominates photon heating (119W).Thesis (M.Sc. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009
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Mankin, Max Nathan. „Advances in Crystal Growth and Assembly for Imparting Novel Photonic Properties to Semiconductor Nanowires“. Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845427.
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Semiconductor nanowires comprise a versatile materials platform with which to characterize the properties of nanomaterials. The vast range of structural and compositional diversity of nanowires has also enabled their use as low-footprint building blocks in a variety of applications including bioelectronics, photonics, and energy conversion. Synthetic control of nanowire size, morphology, and composition as well as assembly of nanowires into pre-determined positions and orientations are paramount to enabling the aforementioned fundamental and applied research. To this end, this thesis presents original research on four aspects of semiconductor nanowire synthesis and assembly, with emphasis on material characterization and how advances in synthesis and assembly can impart new photonic properties to nanowires.
First, I demonstrate facet-selective epitaxial growth of compound semiconductors on silicon nanowires. Electron microscopy and growth studies suggest that facet-selective formation of an oxide prevents growth of the compound semiconductor on certain facets. Facet-selective epitaxy is general to several compound semiconductor materials and for micro-to-mesoscale wires. Optical characterization shows that facet-selective epitaxy integrates the photonic properties of compound semiconductors with silicon nanowires.
Next, I discuss a crystal growth phenomenon unique to one-dimensional materials that combines Plateau-Rayleigh instability with nanowire shell growth to yield diameter-modulated nanowires. We demonstrate wide synthetic tunability over diameter-modulated nanowire morphologies and compositions. Growth studies suggest that surface energy reductions drive the formation of periodic shells, and that kinetic control of growth enables this tunability. Finally, we show that diameter-modulated nanowires display unique optical properties compared to uniform diameter nanowires.
Third, I present an assembly technique that incorporates positioning and shaping to yield U-shaped nanowires with >90% yield and positioning accuracy within 10s of nanometers over a wafer scale. Shape-controlled assembly involves patterning shaped trenches and then shear transferring nanowires to the patterned substrate wafers, where the trenches define the positions and shapes of transferred nanowires. We assemble U-shaped nanowire directional optical couplers that function as nanoscale photonic circuit elements.
Finally, I present optical studies of strained, U-shaped germanium nanowires. Light emission from single germanium nanowires is (i) localized to the strained portions of the nanowires, (ii) enhanced by factors >25 compared to unstrained segments of the nanowires, and (iii) can be monotonically tuned from ~1550 to 1900 nm by deterministically adjusting the radius of curvature and/or the diameter of the nanowires. These studies show that tuning assembly parameters to adjust strain in the nanowires yields changes to the nanowires’ electronic structure, and correspondingly, their optical properties.
Facet-selective epitaxy, Plateau-Rayleigh crystal growth, and shaped nanowire assembly afford exciting opportunities for (i) characterizing unique crystal growth modes of nanomaterials, (ii) imparting novel morphological and crystallographic properties to nanowires, and (iii) studying relationships between these properties and the photonic attributes of nanostructures.Chemistry and Chemical Biology
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LIBRANTZ, ANDRE F. H. „Estudo comparativo da emissoes do Nd(3+) nas configuracoes 4fsup(2)5d e 4fsup(3) induzidas pela excitacao multifotonica em cristais de YLF, GLF, LLF“. reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10830.
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Made available in DSpace on 2014-10-09T12:44:29Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:07:22Z (GMT). No. of bitstreams: 1 07114.pdf: 5950239 bytes, checksum: a45c843d71dddc5fe0b565d5be615211 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Lloyd, Christopher. „The Photo-initiated Bergamn Cyclisation of Z-hex-3-ene-1,5-diyne“. Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499954.
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Bettahar, Houari. „High accurate 3-D photo-robotic nano-positioning for hybrid integrated optics“. Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCD019/document.
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L'intégration hybride d'éléments photoniques individuels offre la promesse de fournir des performances très élevées, de proposer de nouvelles fonctionnalités et produits optiques mais aussi pour exploiter de nouveaux modes de propagation des faisceaux lumineux. Cette approche repose sur la capacité d'un positionnement multi Degré-De-Liberté (DDL) précis des éléments photoniques individuels. Ainsi, la mesure multi-DDL imprécise et le contrôle inexact des robots sont les principaux verrous à surmonter, notamment à l'échelle micrométrique Pour cela, une approche photo-robotique originale a été proposée, s'appuyant sur les mouvements d'un robot à plusieurs DDL associé à l'utilisation de l'interférométrie Fabry-Perot 1-D pour réaliser une mesure de pose multi-DOF. Cette approche intègre notamment la question de l'étalonnage des robots 6-DDL qui a été étudiée à travers l'étalonnage des paramètres géométriques extrinsèques et/ou intrinsèques. Afin de trouver la stratégie d'étalonnage appropriée pour une grande précision de positionnement et adaptée au contexte du micro-positionnement de composants optiques, une quantification et une analyse de durabilité des performances optiques et robotiques ont été étudiées. Des études expérimentales ont démontré qu'une précision de positionnement en rotation et en translation de 0.004° et 27.6 nm ont été obtenues respectivement.Cette approche photo-robotique a été notament appliquée pour réaliser le positionnement 6-DDL d'une lamelle optique par rapport à une fibre optique avec une grande précision ce qui conduit également à des performances optiques maximales. L'approche a également été appliquée pour contrôler les états de polarisation à la sortie d'un système optique hybride en réalisant des rotations très précises d'une lamelle d'onde optique spécifique autour de son axe optique. Les résultats expérimentaux démontrent notamment que la grande précision du positionnement permet un contrôle précis de l'état de polarisation optiqueThe hybrid integration of individual photonic elements appears as promising, because it may provide high performances, propose new optical functionalities and products and exploit new propagation modes of light beams. This approach requires an accurate multi Degree-Of-Freedom (DOF) positioning of the individual photonic elements. Hence, the inaccurate multi-DOF measurement and robots control are the main locks to overcome, notably at the micro-scale. For this sake, an original photo-robotic approach has been proposed, relying on multi-DOF robot motion associated with the use of 1-D Fabry-Perot interferometry measure to realize multi-DOF pose measure. This approach notably integrates the issue of 6-DOF robot calibration that has been studied through extrinsic and/or intrinsic geometric parameters calibration. In order to find the appropriate calibration strategy for high positioning accuracy and adapted to the context of micro-positioning of optical components, a quantification and durability analysis of optical and robotic performances have been investigated. Experimental investigations demonstrate that a rotational and translational positioning accuracy of 0.004° and 27.6 nm have been obtained respectively.This photo-robotic approach has especially been applied to achieve the 6-DOF positioning of an optical lamella relative to an optical fiber with high accuracy that also conduct to maximum optical performances. The approach has also been applied to control the optical polarization states at the output of an hybrid optical system through achieving high accurate rotations of a specific optical wave plate around the optical axis. The experimental results notably demonstrate that the high positioning accuracy enables to accurately control of the optical polarization state
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Petersson, Johan. „Effect of body posture on regional ventilation and perfusion at normal and increased gravity /“. Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-920-3/.
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Henry, Samuel C. „3-D Terahertz Synthetic-Aperture Imaging and Spectroscopy“. PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/693.
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Terahertz (THz) wavelengths have attracted recent interest in multiple disciplines within engineering and science. Situated between the infrared and the microwave region of the electromagnetic spectrum, THz energy can propagate through non-polar materials such as clothing or packaging layers. Moreover, many chemical compounds, including explosives and many drugs, reveal strong absorption signatures in the THz range. For these reasons, THz wavelengths have great potential for non-destructive evaluation and explosive detection. Three-dimensional (3-D) reflection imaging with considerable depth resolution is also possible using pulsed THz systems. While THz imaging (especially 3-D) systems typically operate in transmission mode, reflection offers the most practical configuration for standoff detection, especially for objects with high water content (like human tissue) which are opaque at THz frequencies. In this research, reflection-based THz synthetic-aperture (SA) imaging is investigated as a potential imaging solution. THz SA imaging results presented in this dissertation are unique in that a 2-D planar synthetic array was used to generate a 3-D image without relying on a narrow time-window for depth isolation [1]. Novel THz chemical detection techniques are developed and combined with broadband THz SA capabilities to provide concurrent 3-D spectral imaging. All algorithms are tested with various objects and pressed pellets using a pulsed THz time-domain system in the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab).
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Graham, Matthew. „DEVELOPMENT OF HIGH REFRACTIVE INDEX POLY(THIOPHENE) FOR THE FABRICATION OF ALL ORGANIC 3-D PHOTONIC MATERIALS WITH A COMPLETE PHOTONIC BAND GAP“. University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164049666.
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Shim, Dong Eun. „UV nanoimprinting using a polymer mold and its application to 3-D photonic crystal fabrication“. Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1970611211&sid=54&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Cameron, Craig G. „Natural and artificial fluorescence on 3-dimensional bioorganic nanostructures“. Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53451.
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A challenge exists for understanding the origin of color for structurally colored, 3-dimensional bioorganic nanostructures, such as the scales of butterflies, beetles, and moths. Complex, hierarchical structures found within such scales create the overall scale appearance. The controlled alteration of color through material deposition and the addition of new optical functionalities to such structures are other areas of scientific interest. This dissertation addresses these challenges with a first-of-its-kind, systematic isolation (deconstruction) of scale component nanostructures, followed by evaluation of optical property/structure correlations. The additive deposition (constructive alteration) of emissive materials to structurally-colored templates complements this deconstructive approach towards understanding the origin of color in butterfly scales. Discoveries made through this work may help advance the bioinspired design of synthetic optical structures and subsequent color control through the addition of multilayered, emissive optical components.
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Paulik, Julia [Verfasser]. „[123I]-3-Iodcytisin als möglicher Radiotracer für die Darstellung der nikotinergen Acetylcholinrezeptoren mittels Single-Photon-Emissions-Tomographie / Julia Paulik“. Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1077271263/34.
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Khanduyeva, Natalya. „Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1232556562686-70575.
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The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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Hintz, Holger [Verfasser], und Thomas [Akademischer Betreuer] Chassé. „Photo-oxidation Kinetics of Poly-3-hexylthiophene Thin Films / Holger Hintz ; Betreuer: Thomas Chassé“. Tübingen : Universitätsbibliothek Tübingen, 2012. http://d-nb.info/1162699760/34.
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Khanduyeva, Natalya. „Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures“. Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23635.
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The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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Fuentes, Iriarte Gonzalo. „AlN Thin Film Electroacoustic Devices“. Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://publications.uu.se/theses/91-554-5557-3/.
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Silva, Diego Silvério da. „Produção e caracterização de guias de onda dopados com terras-raras contendo nanopartículas semicondutoras“. Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-20062016-153455/.
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O presente trabalho tem como objetivo estudar a produção e caracterização de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopartículas (NPs) semicondutoras, dopados e codopados com íons de Er3+ ou Er3+/Yb3+ para a produção de amplificadores ópticos. A produção de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia óptica seguida por processo de corrosão por plasma e deposição física a vapor. A incorporação dos íons de terras-raras (TRs) foi verificada a partir dos espectros de emissão. Análises de espectroscopia e microscopia foram indispensáveis para otimizar os parâmetros dos processos para a construção dos guias de onda. Foi observado aumento significativo da luminescência do Er3+ (região do visível e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presença de nanopartículas de Si. As perdas por propagação mínimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presença de NPs de silício (1,8 dB/cm). O ganho óptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de silício também foi medido. Ganho de ~8dB/cm em 1542 nm, sob excitação em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 átomos/cm3, Yb = 3,60.1020 átomos/cm3) com largura de 80 µm; para os guias codopados com concentração superior de Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) e com NPs de Si, foi observado aumento do ganho óptico de 50% para guia com largura de 100 µm. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, são promissores para aplicações em dispositivos fotônicos.This work aims to study the production and characterization of GeO2-Bi2O3 (BGO) thin films produced by RF-sputtering with and without semiconductor nanoparticles (NPs),doped and codoped with Er3+ or Er3+/Yb3+ ions for the production of optical amplifiers. The pedestal type waveguide production based on BGO thin film was done trough optical lithography followed by reactive ion etching and physical vapor deposition processes. The incorporation of the rare-earth ions was verified from the emission spectra. Spectroscopy and microscopy analysis were indispensable to optimize the processes parameters for the waveguide fabrication. It was observed minimum propagation losses of ~1,75 dB/cm, at 1068 nm for the pedestal type waveguides. Optical gain was also measured in the Er3+/Yb3+ codoped waveguides with and without Si nanoparticles. Optical gain of 8 dB/cm, at 1542 nm, under 980nm pumping were obtained for 80 µm width Er3+/Yb3+ codoped waveguides (Er = 4,64.1019 atoms/cm3, Yb = 3,60.1020 atoms/cm3). For waveguides doped with higher concentration of Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) and containing silicon nanoparticles, it was observed 50% enhancement of the optical gain for 100 µm width waveguides. For the Er3+ doped waveguides, it was observed significant gain enhancement in the presence of silicon nanoparticles (1.8 dB/cm). The present results demonstrate that germanate waveguides, with or without semiconductor NPs are promising for applications in photonic devices.
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Pauwels, Jaël. „High performance optical reservoir computing based on spatially extended systems“. Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/331699/3/thesis.pdf.
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In this thesis we study photonic computation within the framework of reservoir computing. Inspired by the insight that the human brain processes information by generating patterns of transient neuronal activity excited by input sensory signals, reservoir computing exploits the transient dynamics of an analogue nonlinear dynamical system to solve tasks that are hard to solve by algorithmic approaches. Harnessing the massive parallelism offered by optics, we consider a generic class of nonlinear dynamical systems which are suitable for reservoir computing and which we label photonic computing liquids. These are spatially extended systems which exhibit dispersive or diffractive signal coupling and nonlinear signal distortion. We demonstrate that a wide range of optical systems meet these requirements and allow for elegant and performant imple- mentations of optical reservoirs. These advances address the limitations of current photonic reservoirs in terms of scalability, ease of implementation and the transition towards truly all-optical computing systems.We start with an abstract presentation of a photonic computing liquid and an in-depth analysis of what makes these kinds of systems function as potent reservoir computers. We then present an experimental study of two photonic reservoir computers, the first based on a diffractive free-space cavity, the second based on a fiber-loop cavity. These systems allow us to validate the promising concept of photonic computing liquids, to investigate the effects of symme- tries in the neural interconnectivity and to demonstrate the effectiveness of weak and distributed optical nonlinearities. We also investigate the ability to recover performance lost due to uncontrolled parameters variations in unstable operating environments by introducing an easily scalable way to expand a reservoir’s output layer. Finally, we show how to exploit random diffraction in a strongly dispersive optical system, including applications in optical telecom- munications. In the conclusion we discuss future perspectives and identify the characteristic of the optical systems that we consider most promising for the future of photonic reservoir computing.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Bahrs, Sabine. „Persistent photo induced effects in high-temperature superconducting RBa2Cu3O7-ddelta [RBa 2 Cu 3 O 7 delta]“. [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978946693.
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Araujo, Leandro Goulart de. „Photo-oxidative degradation of bisphenol A by H2O2/UV: process study and kinetic modelling“. Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-17072018-111837/.
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Bisphenol A (BPA) is widely used in the production of plastics, epoxy resins and polycarbonates. It is a toxic, endocrine disruptor compound. Different studies have shown the presence of BPA in several environmental systems, classifying it as a worldwide persistent pollutant which may act synergistically with other pollutants. In this context, advanced oxidation processes (AOP) have received great attention due to their ability to degrade pollutants with such characteristics, through their transformation into less hazardous compounds or even their mineralization. Although there are investigations on the use of AOPs for BPA degradation, systematic studies on the effects of process variables, coupled with the statistical interpretation of the results are virtually non-existent. Furthermore, to the best of our knowledge, a rigorous kinetic model has not yet been proposed for the degradation of this pollutant by the H2O2/UV process. The objective of this work was to evaluate BPA degradation by the H2O2/UV process, investigating the effects of the initial H2O2 concentration and the specific rate of photons emission (EP,0) by means of a Doehlert experimental design, combined with the response surface methodology. The experiments were performed in a photochemical tubular reactor equipped with a 254-nm UV lamp, for [H2O2]0 and EP,0 in the ranges 1.6-9.6 mmol L-1 and 0.87 × 1018-3.6 × 1018 photons L-1 s-1, respectively. Total BPA degradation was achieved after 60 min of irradiation in all experiments. The best conditions were [H2O2]0 = 7.6 mmol L-1 and EP,0 = 3.6 × 1018 photons L-1 s-1, for which the best performance was obtained regarding the BPA degradation rate, BPA degradation after 15 min, and the second highest TOC removal after 180 min. However, in most experiments less than 75% TOC removal was observed, with 95% mineralization obtained only for the superior [H2O2]0 and EP,0. A mathematical model was developed, considering the reactor characteristics and the radiation field, based on the line source with parallel emission (LSPP) approach, in combination with the radiative transfer equation (RTE), mass balances, and a detailed kinetic model of the H2O2/UV process. The steady-state approximation was applied for all radical species. In the estimation of unknown kinetic constants, the non-linear least squares method was employed. The model was able to satisfactorily fit experimental BPA and H2O2 concentrations as a function of time. This work shows that the H2O2/UV process is a good alternative for BPA removal from aqueous streams, with total degradation of the target compound and adequate percent mineralization under optimal operating conditions. Such conditions may serve as first guidelines for pilot-plant and industrial processes operation. In addition, simulations using the proposed kinetic model may provide useful information for the design and scale-up of pre- or post-treatment of effluents containing this pollutant.O bisfenol A (BPA) é amplamente utilizado na fabricação de plásticos, resinas epóxi e policarbonatos. Trata-se de um composto tóxico e um desregulador endócrino. Diferentes estudos evidenciam a presença do BPA em diversos compartimentos ambientais em todo planeta, identificando-o como um poluente persistente e resistente à degradação biológica, que apresenta efeitos sinergéticos com outros poluentes. Nesse contexto, os processos oxidativos avançados (POA) têm recebido atenção devido a sua capacidade em degradar poluentes com tais características, transformando-os em compostos menos perigosos ou até mesmo mineralizando-os totalmente. Apesar de haver trabalhos na literatura acerca da utilização de POA para degradação de BPA, estudos sistemáticos dos efeitos de variáveis de processo junto com a interpretação estatística dos resultados são virtualmente inexistentes. Além disso, até onde se sabe um modelo cinético rigoroso ainda não foi proposto para a degradação desse poluente por meio do processo H2O2/UV. Este trabalho teve por objetivo avaliar a degradação do BPA pelo processo H2O2/UV, investigando os efeitos da concentração inicial de H2O2 e da taxa específica de emissão de fótons (EP,0) por meio de um projeto experimental Doehlert, combinado com a análise de superfície de resposta. Os experimentos foram realizados em um reator tubular fotoquímico equipado com uma lâmpada UV de 254 nm, para [H2O2]0 e EP,0 entre 1,6-9,6 mmol L-1 e 0,87 × 1018 - 3,6 × 1018 fótons L-1 s-1, respectivamente. Todos os experimentos sob H2O2/UV resultaram em total degradação do BPA após 60 min de irradiação. Nesse caso, as melhores condições foram [H2O2]0 = 7,6 mmol L-1 e EP,0 = 3,6 × 1018 fótons L-1 s-1, para as quais se obteve o melhor desempenho quanto à taxa de degradação de BPA e à remoção após 15 min, e a segunda maior remoção de COT após 180 min. Entretanto, na maioria dos experimentos menos de 75% de remoção de COT foram observados, com 95% de mineralização obtida apenas para os maiores [H2O2]0 e EP,0. Elaborou-se um modelo matemático que considera as características do reator utilizado e o campo de radiação, baseado no modelo de fonte linear de emissão em planos paralelos (LSPP), combinado à equação de transferência radiativa (RTE), aos balanços materiais e a um modelo cinético detalhado do processo H2O2/UV. Foi empregada a aproximação de estado estacionário para todas as espécies radicalares. Na estimativa das constantes cinéticas desconhecidas, utilizou-se o método de mínimos quadrados não linear. Esse modelo foi capaz de ajustar satisfatoriamente as concentrações experimentais de BPA e de H2O2 em função do tempo. Este trabalho mostra que o processo H2O2/UV constitui uma alternativa conveniente para a degradação de BPA em matrizes aquosas, com total degradação do composto alvo e porcentagem de mineralização adequada nas condições ótimas de operação. Tais condições podem servir como diretrizes iniciais de processamento em escalas piloto e industrial. Por sua vez, simulações empregando o modelo matemático proposto permitem gerar informações úteis para projeto e aumento de escala de processos de pré- ou pós-tratamento de efluentes contendo esse poluente.
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Carvalho, Daniel Orquiza de. „Desenvolvimento de processos de fabricação de dispositivos óptico integrados em tecnologia de silício para aplicação em sensoriamento“. Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-19092012-170421/.
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Os objetivos desta tese são: o estudo e aprimoramento dos diferentes parâmetros geométricos e de processo de fabricação de guias de onda ARROW (Anti-Resonant Reflecting Optical Waveguides), visando reduzir as perdas por propagação; e o projeto, fabricação e caracterização de sensores óptico integrados utilizando os processos aprimorados. Os parâmetros estudados foram: os materiais utilizados nas camadas antirresonantes, as espessuras destas camadas, a profundidade de corrosão para definição do rib e a rugosidade nas paredes laterais, que considera-se o parâmetro mais crítico no que diz respeito às perdas por propagação obtidas com o processo de fabricação utilizado neste trabalho. Os materiais utilizados na fabricação dos guias de onda ARROW sobre substrato de silício foram filmes de oxinitreto de silício (SiOxNy) depositados por PECVD à temperatura de 320°C, filmes de SiO2 crescidos em forno de oxidação em ambiente úmido a 1200°C e filmes de TiOxNy depositados pela técnica de Magnetron Sputtering Reativo. A definição das paredes laterais dessas estruturas foi feita através da Corrosão por Plasma Reativo (RIE) e técnicas fotolitográficas convencionais. Para o aprimoramento dos processos, as técnicas de caracterização utilizadas foram: medidas de perdas por propagação, utilizando a técnica de vista superior e a análise modal dos guias de onda. A principal contribuição deste trabalho foi a proposição de um processo de fabricação alternativo, onde pedestais são utilizados para a definição das paredes laterais antes da deposição do núcleo dos guias de onda. Este processo permitiu a redução significativa das perdas e o corte dos modos superiores para guias com larguras menores ou iguais a 6 µm. Finalmente, com os guias e os processos aperfeiçoados foram fabricados dois diferentes tipos de sensores ópticos: sensores refratométricos baseados em interferômetro de Mach-Zehnder (IMZ) e sensores de umidade baseados em absorção utilizando o polímero polipirrol (PPy). A caracterização dos sensores baseados em IMZ permitiu concluir que, embora se tenha observado uma resposta do sensor em termos de variação da potência na saída do dispositivo com a variação do índice de refração, esta variação possivelmente está sendo influenciada pela interferência multimodo resultante de limitações do processo de fabricação, o que reduz significativamente a sensibilidade com relação a valores projetados. Os sensores de umidade apresentaram uma variação significativa da potência de saída para umidades relativas ao redor de 70%, permitindo sua utilização em diferentes aplicações, como na indústria alimentícia e no monitoramento da qualidade do ar.The main goals of this thesis are: the study and improvement of different geometrical and fabrication process parameters of Anti-Resonant Reflecting Optical Waveguides (ARROWs), aiming at reducing the propagation losses; and the design, fabrication and characterization of integrated optics sensors using the improved processes. The studied parameters were: the materials used as anti-resonant layers, the thickness of these layers, the rib height and the sidewall roughness (SWR), which is considered the most critical parameter with respect to propagation losses in the fabrication process used in this work. The materials used in the fabrication of ARROW waveguides over silicon substrate were silicon oxynitride (SiOxNy) films deposited by PECVD at 320°C, SiO2 films, thermally grown at 1200°C and TiOxNy films deposited by the reactive magnetron sputtering technique. The definition of the sidewalls of these waveguides was performed by Reactive Ion Etching (RIE) and conventional photolithographic techniques. The characterization techniques used were: propagation loss measurements, using the top view technique and modal analysis. The main contribution of this work was the proposition of an alternative fabrication process where pedestals are used in order to define the sidewalls before deposition of the core of the ARROW waveguides. This process allowed significant reduction of losses and cutoff of higher modes at widths of 6 µm. Finally, with the waveguides and improved processes two different types of optical sensors were fabricated: refractometric sensors based on Mach-Zehnder interferometer (IMZ) and humidity sensors based on evanescent field absorption using polypyrrole polymer (PPy). The characterization results of IMZ based sensors showed that, although a sensor response has been observed in terms of change of output power with variation of the external medium\'s refractive index, this variation is possibly being influenced by multimode interference resulting from limitations in the fabrication process. This significantly reduces the sensitivity with respect to designed values. The humidity sensors show a significant variation in output power for relative humidity values around 70%, allowing its use in different applications, such as in food industry and in air quality monitoring.
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Rizzo, Vinícius Zacarias. „Estudo das propriedades ópticas e eletro-ópticas de filmes de carbono amorfo tipo diamante - DLC“. Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-10012011-143459/.
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Neste trabalho foram estudadas as características elétricas e ópticas de filmes de carbono tipo diamante (DLC Diamond-Like Carbon) depositados em um sistema de sputtering RF magnetron reativo em substratos de silício e vidro. Foram depositadas amostras em condições de processo distintas em cada tipo de substrato, sendo duas condições de pressão (5 mTorr e 10 mTorr) e para cada uma, quatro condições de potência de RF (100 W, 150 W, 200 W e 250 W). Os filmes depositados foram submetidos às seguintes técnicas de caracterização: perfilometria, para obtenção da espessura dos filmes e com isso a taxa de deposição; elipsometria, para obtenção do índice de refração; obtenção de curvas I-V, para obtenção da resistividade elétrica e cálculo do ganho de foto corrente, e da curva C-V de alta frequência, para cálculo da constante dielétrica dos filmes; transmitância óptica, para o cálculo do gap óptico através do método de Tauc; fotoluminescência, para determinar a emissão característica deste gap e espectroscopia de infravermelho por transformada de Fourier (FTIR), para se observar os tipos de ligações presentes no filme e calcular a relação entre hibridizações sp3 e sp2 entre átomos de carbono e hidrogênio no filme. As variações de algumas características dos filmes de DLC com os parâmetros de processo são apresentadas e comparadas. De acordo com as características dos filmes obtidos neste trabalho, com a variação dos parâmetros de processo, é possível sua aplicação como dielétrico de campo, por apresentarem baixa constante dielétrica, sendo o valor mais baixo obtido igual a 3,4; como material dielétrico de porta considerando os filmes com alta constante dielétrica, chegando a 6,7; como material para cobertura, devido à alta uniformidade (até 95%); e, o que foi mais explorado neste trabalho, para aplicações como sensores foto sensíveis, sendo que o maior ganho de foto corrente obtido foi 67 vezes. A possibilidade de produção de filmes de DLC com diferentes propriedades através da variação das condições de processo mostra sua versatilidade para uso em diferentes aplicações.In this work it was studied electrical and optical characteristics of diamond-like carbon (DLC) films deposited in a reactive RF magnetron sputtering system on silicon and glass substrates. Samples were deposited at different process conditions in each type of substrate at two pressure conditions (5 mTorr and 10 mTorr) and four conditions of RF power (100 W, 150 W, 200 W and 250 W). The DLC films were characterized by the following techniques: high step meter analysis, to obtain the thickness of the films and thus the deposition rate; Ellipsometry to obtain the refractive index; electrical characterization by the I-V curve, to obtain the resistivity and calculate the photo current gain, and high-frequency C-V curve, to calculate the dielectric constant of the films; optical transmittance, to calculate the optical gap by the Tauc method; photoluminescence analysis, to determine the characteristic emission of this gap; Fourier transform infrared spectroscopy (FTIR), to observe the different carbon-hydrogen bonds and calculate its sp3/sp2 hybridizations ratio. The way some characteristics of DLC films vary with the process parameters are presented and compared in this work. According to the characteristics of the DLC films obtained in this work, with the variation of the process parameters it is possible their application as low k dielectric insulators, because of its low dielectric constant, being the lowest obtained value 3.4; as dielectric gate material, reaching 6.7 in the films deposited in this work, as coating material due to its high uniformity (95%), and which was further explored in this work, for applications like photo-sensitive sensors, since it was obtained samples with photo current gain up to 65. The possibility of producing DLC films with different properties by varying process parameters shows its versatility for using in different applications.
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Pereira, Luciana. „Lições da indústria fotônica para o desenvolvimento tecnológico“. Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3136/tde-18082008-143542/.
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Esta tese analisa como tecnologias emergentes podem ajudar a fortalecer o desenvolvimento industrial. A preocupação é pertinente, pois a produção tecnológica é um importante componente do desenvolvimento econômico. A partir das observações empíricas da indústria fotônica, nós extraímos algumas lições e propomos um modelo que explica como ocorre a evolução tecnoindustrial. Trata-se, pois, de um modelo geral que ajuda a entender os mecanismos que levam ao aumento da participação da produção industrial intensiva em tecnologia e que serve tanto para países em desenvolvimento quanto para os desenvolvidos.This dissertation analyses how emerging technologies can help fostering industrial development. It\'s an important issue since the high-tech intensive output has become an important element of economic growth. From the empirical findings and literature discussion, we proposed a model that explains the evolution of high-technology industries. This is a general model that helps to understand the mechanisms to increase the share of production in technology-intensive industries, both in developing and developed countries.