<p dir="ltr">This thesis deals with optical cavity-coupled two-dimensional (2D) materials. First, we describe a new theoretical approach to model the properties of cavity-coupled plasmons in 2D conductors. Next, we propose an optical cavity architecture for enhanced light-matter interaction with potential for performance and functionality beyond that of traditional approaches and describe an initial investigation of one example of such a system. Finally, we provide a thorough description of the fabrication techniques used to produce the previously mentioned optical cavities.</p><p dir="ltr">The advent of 2D materials has opened exciting possibilities for controlling light-matter interactions at the nanoscale. The first major contribution of this work is the investigation of coupling between patterned 2D Van der Waals materials and Fabry-Perot cavities, focusing on how system parameters like pattern shape and material properties influence these interactions. Using a quasistatic eigenmode expansion approach, we develop a theoretical framework to predict and manipulate optical behavior in these systems. Our work opens new pathways for engineering light-matter interactions within patterned 2D material platforms, paving the way for the engineering of novel optical phenomena.</p><p dir="ltr">The second major contribution of this work is the development of a versatile platform for light-matter coupling experiments in Van der Waals materials. It is well-known that light-matter interaction can be used to realize unprecedented functionality in the coupled materials. However, few---if any---approaches to date utilize this phenomenon to its fullest extent. We have provided a platform that can be used to realize light-matter coupling efficiencies beyond what is possible in conventional systems, can be easily integrated with 2D materials, and provides new opportunities to engineer the photonic environment of the coupled material. In particular, we focus on silicon dielectric bowtie cavities (DBCs) coupled to few-layer flakes of $\rm WSe_2$. This approach leverages topology-optimized cavity architectures to achieve simultaneous spatial and spectral confinement, yielding Purcell factors exceeding 2500, mode volumes as small as $\sim10^{-3}(\lambda/2n)^3$, and quality factors up to $\sim200$---performance metrics limited only by material losses. The lithographically defined DBCs enable deterministic emission hotspot placement and tunability across a broad wavelength range with minimal performance impact. Photoluminescence imaging and spectroscopy reveal comparable $\rm WSe_2$ exciton emission enhancement to plasmonic structures. This platform surpasses the limitations of conventional cavity architectures by enabling unprecedented coupling efficiencies and unique functionality while maintaining sufficient mechanical robustness for 2D material transfer.</p><p dir="ltr">The final chapter outlines the fabrication process for the cavities described in the previous chapter. The fabrication involves advanced nanolithography techniques to define patterns with high resolution, addressing challenges such as proximity effects and process blur. Techniques such as proximity effect correction (PEC) are used to enhance pattern accuracy, while careful optimization of exposure and development parameters ensures minimal distortion. The process utilizes high-anisotropy reactive ion etching to transfer the patterns onto the substrate, where precise optimization of the etching parameters has been performed to achieve high resolution and selectivity. The final optimized process yields structures with a minimum feature size of approximately 20 nm and minimum radius of curvature of approximately 10 nm, allowing for the repeatable fabrication of complex inverse-designed cavities.</p>

Diode lasers are a convenient and economical source of near-infrared radiation, which may usefully be applied to a host of different sensitive detection methods; this thesis presents novel extensions of these methods, making use of the favourable characteristics of this type of light source. The first part of this thesis details the development of an optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) apparatus, including the development of the optical system, the sample handling, and the electronics for feedback phase control. A preliminary demonstration of the system is reported, presenting the detection of atmospheric water absorptions close to 1596 nm. Optimisation and application of the OF-CEAS spectrometer are then demonstrated, after which the spectrometer is applied to the sensitive detection of carbon dioxide absorptions suitable as a diagnostic aid in identifying Heliobacter pylori infection. A time-normalised α-min value of 5.8 × 10⁻⁹ cm⁻¹s^1/2 was measured for these spectra. Further optimisation of the system leads to an ultimate detection sensitivity of 1.42 × 10⁻⁹ cm⁻¹s^1/2, measured on absorption transitions in acetylene close to 1532 nm. In order further to characterise the performance of the OF-CEAS system, analogous experiments are presented using the OF-CEAS setup and a standard diode-laser cavity-enhanced absorption spectroscopy (CEAS) apparatus. Detection is carried out on the P(6) line of the ν₁ + ν₃ vibrational band of the mixed isotopologue of acetylene, ¹²-C¹³-CH₂. Direct comparison is made between the sensitivities of the two methods, and in light of this the suitability of each technique for detection in different environments is considered. The well-characterised and consistent frequency scale which is inherent to the OF-CEAS technique is then applied to a line shape analysis for the presented absorption spectra. Pressure-broadening coefficients are determined for selected absorptions in the ν₁ + ν₃ band of acetylene. In spite of the low resolution associated with this technique, this accurate frequency scaling allows observation of subtle line shape effects such as Dicke collisional narrowing using the data presented in Chapter 3 for the R(60) line in the 3ν₁ + ν₃ vibrational band of CO₂. These effects are quantified through use of a Galatry fit to each absorption spectrum. The statistical significance associated with the use of such a model, and the physical meaning of the results, are examined and discussed. An alternative strategy for increasing the sensitivity of a diode-laser-based gas monitoring technique lies in moving detection to the mid-infrared region, where the absorption cross-sections are generally larger. With this motivation, difference frequency generation is presented, to produce radiation close to 3.5 µm which is then applied to a series of different enhanced spectroscopy techniques. The optimal sensitivity, of 32 ppb NO2 at 45 Torr total sample pressure, was achieved using wavelength modulation spectroscopy. The different techniques are compared and possible improvements to them are put forward. Finally, proof-of-principle work is presented seeking to combine the enhanced circulating power associated with the optical-feedback-locked techniques and non-linear optical techniques to move detection to a more favourable spectral region. Light close to 429 nm is generated by second harmonic generation in a crystal of potassium niobate, with resonance-enhancement afforded by a feedback V-cavity of the sort employed in OF-CEAS. The potential of such a system for diode-laser-based generation of blue and ultraviolet light is demonstrated and discussed, along with improvements that might be implemented to increase the efficiency of the system.

Made available in DSpace on 2016-04-26T20:24:11Z (GMT). No. of bitstreams: 1 Rafael Tocantins Maltez.pdf: 3910859 bytes, checksum: 09532e1840fa58ca5b5f01a0e4d819f7 (MD5) Previous issue date: 2016-02-15 / The Federal Constitution includes as Union property the subterraneous natural cavities and archeological and pre-historic sites . According to this express provision, by itself, highlight the value, just as well interest of the Brazilian society in the protection of this assets, which was clearly elucidate by lawgiver in 1988. As an environmental heritage to be preserved, the subterraneous natural cavities which doesn t have a current regulatory legislation, nothing more than Executive Branch norms about this issue (in special decree n. 6.649/2008) the natural cavities certainly deserve analyses and more specific problematization, specially over the conflicts with others equally constitutionals values, what raises a clash between exploitation of natural resources to supply the present capitalist mode of production against preserving speleological patrimony by multiples values offered at no charge to the humanity. For that all, it is necessary to identify, from the Constitution, the juridical nature and the legal regime applicable to subterraneous natural cavities, for purposes of it s preservation and implementation of sustainable development in relation to mining, under state management of Union. On this perspective, the present thesis objective (i) identify the environmental speleological patrimony protected constitutionally; (ii) approach of economical exploration over subterraneous natural cavities, in clash between necessity of preservation; (iii) discourse about biodiversity protection and scientific and cultural heritage involved in the environment of this cavities; and (iv) expose the interferences of the mining activity in subterraneous natural cavities and the unique natural resources in danger of extinction, by oversight of regulatory provisions in force and the Union management. Based in problematic exposed and with mainstay in the basic reference reunited law, legal doctrine, treaty, jurisprudence , concludes that decree n. 6.640/2008 is unconstitutional and the subterraneous natural cavities have multiple legal nature, than deserve special legal regulations and, therefore, there is the draft bill n. 5071/1990 specifically treats the natural cavities , which has been processed for two decades and it is only pending a review of changes proposed by Federal Senate Substitute, since September 2011 / A Constituição Federal incluiu como bens da União as cavidades naturais subterrâneas e os sítios arqueológicos e pré-históricos . Essa disposição, por si só, evidencia o valor e o interesse da sociedade brasileira na proteção desses bens, traduzidos pelo legislador originário em 1988. Como patrimônio ambiental a ser preservado o qual não dispõe de legislação regulamentadora de regência, mas apenas de normas emanadas do Poder Executivo regulando a matéria (em especial o Decreto n. 6.640/2008) , as cavidades naturais são merecedoras de análise e problematização mais específicas, especialmente quanto aos conflitos com outros valores igualmente constitucionais, os quais suscitam o embate entre a exploração de recursos do ambiente natural para abastecer o atual modo de produção capitalista e a necessidade de preservar o patrimônio espeleológico pelos múltiplos valores que gratuitamente oferecem ao homem. Por tudo isso, é preciso identificar, a partir da Constituição, a natureza jurídica e o regime jurídico aplicáveis às cavidades naturais subterrâneas, para fins de sua preservação e aplicação do desenvolvimento sustentável em relação à mineração, sob gestão da União. Nesta perspectiva, a presente tese objetiva (i) identificar o patrimônio espeleológico ambiental tutelado constitucionalmente; (ii) abordar a exploração econômica das cavidades naturais subterrâneas, em confronto com a necessária preservação; (iii) discorrer sobre a proteção da biodiversidade e do patrimônio científico-cultural envoltos nos ambientes cavernícolas; e (iv) expor as interferências das atividades de mineração nas cavidades naturais subterrâneas e os recursos naturais peculiares em perigo de extinção, dado o descuido das disposições regulamentares em vigor e da gestão a cargo da União. A partir dos problemas apresentados e com esteio no referencial de base reunido legislação, tratados, doutrinas, jurisprudências , chega-se à conclusão de que o Decreto n. 6.640/2008 é inconstitucional e que as cavidades naturais subterrâneas possuem natureza jurídica múltipla, merecendo regulamentação legal, em sentido formal, específica e, para tanto, existe o PL n. 5.071/1990 especificamente das cavidades naturais , o qual tramita há mais de duas décadas e está pendente apenas de revisão das alterações a ele propostas pelo Substitutivo do Senado Federal, desde setembro de 2011

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Um der Mikrowellenerwärmung als Single- oder Hybridanwendung im industriellen Ofenbau ein weiteres Anwendungsspektrum zu eröffnen, wird dem Anlagenkonstrukteur im Rahmen dieser Arbeit eine Aufstellung von Entwicklungsprioritäten und Konstruktionshinweisen übergeben. Für eine energieeffiziente Ausnutzung des technologischen Potenzials wird hierbei nicht - wie in der Vergangenheit - die Feldstärkenverteilung, sondern das Reflexionsverhalten in den Vordergrund gestellt. Durch die Entwicklung und den Aufbau eines Messplatzes zur Bestimmung temperaturspezifischer Dielektrizitätsparameter konnte die Realitätsnähe der Simulation für die anwendungsorientierte Applikatorentwicklung gesteigert werden. Die Anwendbarkeit der Auslegungskriterien wird im Rahmen der Projektierung und des Aufbaus einer Beispielanlage zur Entbinderung von keramischen Grünkörpern und bei der Entwicklung zahlreicher mikrowellenspezifischer Anlagenbauteile verifiziert.

Cette recherche doctorale porte sur la modélisation 3D de la dynamique des teneurs en eau dans le sol et le soussol lorsque les écoulements sont à saturation variable. La modélisation est basée sur une version généralisée de la loi de Darcy-Buckingham et de l’équation de Richards multidimensionnelle. Les recherches présentées dans cette thèse concernent différents volets, présentés ci-dessous, dont le fil conducteur est l’analyse de phénomènes d’écoulements en milieux poreux, contenant de fortes hétérogénéités et/ou perturbés par des fluctuations temporelles. Dans le cadre d’un partenariat de recherche entre l’IMFT et l'IRSN sur la problématique du stockage souterrain de déchets radioactifs, nous avons modélisé en 3D la dynamique du front de désaturation d’une couche argileuse autour d’une galerie souterraine ventilée, à l’aide du code volumes finis BIGFLOW 3D. Ce travail a permis de mettre au point une approche d’immersion pour la modélisation des écoulements en milieux composites. Un autre volet de cette thèse concerne une étude analytique et numérique des profils verticaux de succion et de teneur en eau lors d’une infiltration verticale, non-saturante, dans un sol hétérogène finement stratifié. Des solutions analytiques exactes et approchées sont obtenues en régime permanent, à l’aide de transformations de variables, et sont comparées avec des solutions numériques pour différents degrés d’hétérogénéité. De même, les phénomènes de « barrière capillaire » sont étudiés d’une part analytiquement et d’autre part, par expérimentations numériques transitoires d’infiltration sur des systèmes bicouches, en présence d’une nappe plus ou moins profonde. D’autre part, les écoulements nonsaturés sont étudiés, cette fois, en présence d’un forçage transitoire fortement oscillatoire, dans une colonne de sable fin homogène, sous l’effet de fluctuations périodiques du niveau de la surface libre. Une méthode multi-front mise au point lors d’une thèse précédente à l’IMFT est validée numériquement en montrant que cette méthode simule efficacement la dynamique oscillatoire des flux et des profils de pression avec un nombre limité de « fronts ». De plus, nous avons analysé la phénoménologie capillaire/gravitaire des écoulements oscillatoires dans la colonne grâce à un suivi dynamique du plan de flux nul. Enfin, nous présentons, comme extension aux travaux précédents, une étude préliminaire des phénomènes 3D d’infiltration et de redistribution d’eau, notamment lorsque l’hétérogénéité du sol est de type aléatoire. Les premiers essais d’infiltration permettent de tester, en réplique unique, des méthodes de prises de moyennes spatiales des champs de succion et teneur en eau et évaluer la taille minimum du domaine de calcul 3D permettant d’obtenir des profils verticaux moyens représentatifs de l’infiltration dans une réplique unique du sol aléatoire. / This doctoral research, defended at the Institut de Mécanique des Fluides de Toulouse, is devoted to modeling water pressure and water content in soils and in subsurface geologic formations, in the case of variably saturated flow. One of the main scientific objectives of this work is to analyze the response of unsaturated flow systems, and particularly capillary and gravitational effects, in the presence of material heterogeneities, discontinuities, and/or space-time fluctuations. Modeling is based on a generalized version of Darcy- Buckingham’s law, and of Richards’ flow equation. Overall, the topics developed in this PhD thesis focus on several related aspects of variably saturated water flow in the subsurface. These aspects all occur at once in most applications (drying/wetting,heterogeneity, temporal forcing), but they are "decoupled" here for convenience. A preliminary research (collaborative project IMFT / IRSN) was developed to study the 2D/3D drying process at the porous wall of a deep cylindrical excavation in response to hydrometeorological signals. This project has motivated the design and testing of a novel approach to include cavities in the modeling domain. A detailed study of steady state infiltration was developed for the case of finely stratified soils, with parameters that vary continuously and cyclically with depth. Exact and approximate analytical solutions are calculated based on variable transformation methods and on perturbation type approximations, and they are tested numerically using a finite volume code (BIGFLOW 3D). The sensitivity of suction fluctuations vs. stratification wavelength is investigated, as well as the effect of the degree of heterogeneity, and of water table depth. Capillary barrier effects are studied for the case of unsaturated infiltration in multilayer soil systems characterized by a discontinuity of soil properties at interfaces. Numerical experiments are developed for transient infiltration towards a water table through a two-layer system, the goal being to analyze possible capillary barrier effects under various scenarios. On the other hand, we study numerically the case of a partially saturated / unsaturated soil column submitted to highly variable oscillatory pressure at the bottom of the column: this leads to vertical flow oscillations in the unsaturated zone above the water table influenced by tides (coastal beach sand). We analyze the dynamics of this oscillatory flow, where capillary and gravitational effects compete; for this purpose we use a novel method that tracks the positions of the zero flux plane in the unsaturated column. Finally, we also present, as an extension to the previous studies, a preliminary investigation of multidimensional infiltration/redistribution phenomena, particularly for the case of fully 3D random-type soil heterogeneity. The first numerical experiments of 3D infiltration are undertaken based on the single realization approach to soil heterogeneity, and assuming a uniform distribution of wetting at soil surface.

Les amas des galaxies sont l’une des plus grandes structures liées gravitationnellement de l’univers. Leur dynamique est complexe et bien que plusieurs études multi-longueur d’onde ont été effectuées depuis la fin du 20ème siècle, il persiste plusieurs incertitudes sur les subtilités de leur dynamique. À ce jour, le consensus scientifique est que les trous noirs supermassifs actifs au centre des amas ont un impact important sur l’évolution de ces structures. Le trou noir central agit comme centre gravitationnel, mais lorsque ce trou noir est actif, son rôle ne se limite pas seulement à son impact gravitationnel. D’une part, les trous noirs actifs ont un rôle crucial dans l’émission thermique des amas. En effet, les jets radio influencent l’émission rayons-X des amas en poussant mécaniquement le milieu intra-amas qui émet en rayons-X via l’émission Bremsstrahlung. Ce phénomène engendre la formation de cavités rayons-X qui constituent une preuve de la rétroaction énergétique du trou noir sur l’ensemble de l’amas. Un tel phénomène est nécessaire afin d’expliquer les résultats observationnels qui témoignent d’un refroidissement moins important que prédit théoriquement au centre des amas à cœur froid. D’autre part, il existe de plus en plus d’études qui supportent l’hypothèse que les trous noirs actifs ont un rôle dans la (ré-)accélération de particules relativistes responsables de l’émission synchrotron au cœur des amas à cœur froid. Ces structures appelées mini-halos sont typiquement diffuses en radio et donc difficiles à détecter. Dans ce mémoire, nous étudierons en détail l’émission radio de l’amas de galaxies massif à cœur froid MS 0735.6+7421 (z = 0.216). Cet amas est unique puisqu’il possède les jets radio les plus énergétiques détectés au centre d’un amas à cœur froid. Il s’agit donc d’un exemple de trou noir actif parmi les plus extrêmes connus. Cet objet constitue ainsi une cible parfaite afin d’étudier le lien qui unit la rétroaction du trou noir actif central et l’émission synchrotron au centre des amas à cœur froid. Pour réaliser cette étude, nous avons effectué une analyse radio exhaustive de MS 0735.6+7421 à l’aide de données acquises sur le Karl G. Jansky Very Large Array. Cette analyse a permis de détecter une nouvelle structure radio diffuse jamais détectée auparavant. Cette nouvelle structure possède une puissance radio à 1.4 GHz qui concorde avec celles des mini-halos les plus lumineux. Le résultat principal de notre étude supporte donc l’hypothèse selon laquelle il existe un lien fondamental entre la rétroaction du trou noir actif central et la formation de mini-halos au centre des amas à cœur froid. / Galaxy clusters are one of the largest gravitationally bound structures in the universe. They exhibit complex dynamics and even though several multi-wavelength studies have been conducted since the end of the 20th century, there are still a lot of uncertainties concerning their evolution. To this day, the scientific consensus is that the active supermassive black hole at the center of the cluster has a profound impact on the cluster’s evolution. Indeed, the central supermassive black hole has a substantial gravitational impact, but when the black hole actively accretes material, its role goes beyond its gravitational influence. Active supermassive black holes have a crucial role in terms of the thermal emission in clusters. Indeed, the radio jets influence the X-ray emission of clusters by mechanically pushing the intracluster medium which emits in X-ray via Bremsstrahlung emission. This leads to the formation of X-ray cavities which are proof of the energetic feedback of the central supermassive black hole on the cluster. Such a phenomenon is required to reconcile the observational results that report less cooling at the center of cool core clusters than what is theoretically predicted. Moreover, there are more and more studies that support the hypothesis that active supermassive black holes have a crucial role in the (re-)acceleration of seed particles responsible for synchrotron emission at the center of cool core clusters. These structures are named mini-halos and are usually difficult to detect because they are diffuse. In this Master’s thesis, we will study the radio emission of the massive cool core galaxy cluster MS 0735.6+7421 (z = 0.216). This cluster is unique because it exhibits the most powerful radio jets ever detected at the center of a cool core cluster. It thus contains one of the most powerful active supermassive black holes known. This object is a perfect target to study the link between active black hole feedback and synchrotron emission in cool core clusters. To conduct this study, we performed a radio analysis of MS 0735.6+7421 with new data obtained with the Karl G. Jansky Very Large Array. This analysis led to the discovery of an extended diffuse radio structure. This newly detected structure has a radio power at 1.4 GHz that matches the most luminous mini-halos known in the literature. The principal result of our study argues in favor of the hypothesis that there is a fundamental link between active black hole feedback and the formation of mini-halos at the center of cool core clusters.

Um der Mikrowellenerwärmung als Single- oder Hybridanwendung im industriellen Ofenbau ein weiteres Anwendungsspektrum zu eröffnen, wird dem Anlagenkonstrukteur im Rahmen dieser Arbeit eine Aufstellung von Entwicklungsprioritäten und Konstruktionshinweisen übergeben. Für eine energieeffiziente Ausnutzung des technologischen Potenzials wird hierbei nicht - wie in der Vergangenheit - die Feldstärkenverteilung, sondern das Reflexionsverhalten in den Vordergrund gestellt. Durch die Entwicklung und den Aufbau eines Messplatzes zur Bestimmung temperaturspezifischer Dielektrizitätsparameter konnte die Realitätsnähe der Simulation für die anwendungsorientierte Applikatorentwicklung gesteigert werden. Die Anwendbarkeit der Auslegungskriterien wird im Rahmen der Projektierung und des Aufbaus einer Beispielanlage zur Entbinderung von keramischen Grünkörpern und bei der Entwicklung zahlreicher mikrowellenspezifischer Anlagenbauteile verifiziert.

Ce mémoire est consacré au développement de technologies de filtrage novatrices qui apportent un gain en performance permettant de répondre aux besoins de filtrage pour télécommunications spatiales à moyen et long termes. Il s’inscrit dans le projet ANR ATOMIQ coordonné par Thales Alenia Space ayant comme partenaires le laboratoire SPCTS et la société 3D CERAM. Le premier chapitre est constitué d’une étude bibliographique sur les filtres en bande Q et V ainsi que les technologies de fabrication 3D. Le deuxième chapitre est consacré à l’élaboration d’une nouvelle formulation d’alumine très pure à faible pertes et stable en température. Le troisième chapitre présente une conception de filtres hyperfréquences en bande Q et V à base de cavités résonantes diélectriques. Le quatrième chapitre concerne la fabrication des filtres par usinage en cru ainsi que la présentation des différents démonstrateurs fabriqués par stéréolithographie et moulage basse pression. Il présente aussi des solutions de correction post-fabrication par tir laser. Ce travail est original par l’utilisation de la stéréolithographie céramique 3D ainsi que du moulage basse pression pour fabriquer des filtres hyperfréquences de petites tailles en bande Q et V. / This thesis focus on the development of innovative filtering technologies that enhance the performance to meet the filtering requirements for spacial communications. It is part of the ANR project ATOMIQ coordinated by Thales Alenia Space with partners (SPCTS 3D CERAM). The first chapter consists of a literature review on the Q and V band filters as well as 3D manufacturing technologies. The second chapter is devoted to the development of a new formulation of highly pure, low losses and temperature stable alumina. The third chapter presents a microwave filter design in Q and V band based on a dielectric resonant cavity. The fourth chapter is about the manufacturing of filters and presentation of various demonstrators manufactured by stereolithography and low pressure molding. It also provides a post-production correction solutions based on laser shoots. This work is original because, to the best of our knowledge, 3D ceramic stereolithography and the low pressure molding have not been used to produce small sizes Q and V band microwave filters.

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