The analysis of wave propagation in hyperelastic waveguides has significant applications in various branches of engineering like Non-Destructive Testing and Evaluation, impact analysis, material characterization and damage detection. Linear elastic models are typically used for wave analysis since they are sufficient for many applications. However, certain solids exhibit inherent nonlinear material properties that cannot be adequately described with linear models. In the presence of large deformations, geometric nonlinearity also needs to be incorporated in the analysis. These two forms of nonlinearity can have significant consequences on the propagation of stress waves in solids. A detailed analysis of nonlinear wave propagation in solids is thus necessary for a proper understanding of these phenomena. The current research focuses on the development of novel algorithms for nonlinear finite element analysis of stress wave propagation in hyperelastic waveguides. A full three-dimensional(3D) finite element analysis of stress wave propagation in waveguides is both computationally difficult and expensive, especially in the presence of nonlinearities. By definition, waveguides are solids with special geometric features that channel the propagation of stress waves along certain preferred directions. This suggests the use of kinematic waveguide models that take advantage of the special geometric features of the waveguide. The primary advantage of using waveguide models is the reduction of the problem dimension and hence the associated computational cost. Elementary waveguide models like the Euler-Bernoulli beam model, Kirchoff plate model etc., which are developed primarily within the context of linear elasticity, need to be modified appropriately in the presence of material/geometric nonlinearities and/or loads with high frequency content. This modification, besides being non-trivial, may be inadequate for studying nonlinear wave propagation and higher order waveguide models need to be developed. However, higher order models are difficult to formulate and typically have complex governing equations for the kinematic modes. This reflects in the relatively scarce research on the development of higher order waveguide models for studying nonlinear wave propagation. The formulation is difficult primarily because of the complexity of both the governing equations and their linearization, which is required as part of a nonlinear finite element analysis. One of the primary contributions of this thesis is the development and implementation of a general, flexible and efficient framework for automating the finite element analysis of higher order kinematic models for nonlinear waveguides. A hierarchic set of higher order waveguide models that are compatible with this formulation are proposed for this purpose. This hierarchic series of waveguide models are similar in form to the kinematic assumptions associated with standard waveguide models, but are different in the sense that no conditions related to the stress distribution specific to a waveguide are imposed since that is automatically handled by the proposed algorithm. The automation of the finite element analysis is accomplished with a dexterous combination of a nodal degrees-of-freedom based assembly algorithm, automatic differentiation and a novel procedure for numerically computing the finite element matrices directly from a given waveguide model. The algorithm, however, is quite general and is also developed for studying nonlinear plane stress configurations and inhomogeneous structures that require a coupling of continuum and waveguide elements. Significant features of the algorithm are the automatic numerical derivation of the finite element matrices for both linear and nonlinear problems, especially in the context of nonlinear plane stress and higher order waveguide models, without requiring an explicit derivation of their algebraic forms, automatic assembly of finite element matrices and the automatic handling of natural boundary conditions. Full geometric nonlinearity and the hyperelastic form of material nonlinearity are considered in this thesis. The procedures developed here are however quite general and can be extended for other types of material nonlinearities. Throughout this thesis, It is assumed that the solids under investigation are homogeneous and isotropic. The subject matter of the research is developed in four stages: First, a comparison of different finite element discretization schemes is carried out using a simple rod model to choose the most efficient computational scheme to study nonlinear wave propagation. As part of this, the frequency domain Fourier spectral finite element method is extended for a special class of weakly nonlinear problems. Based on this comparative study, the Legendre spectral element method is identified as the most efficient computational tool. The efficiency of the Legendre spectral element is also illustrated in the context of a nonlinear Timoshenko beam model. Since the spectral element method is a special case of the standard nonlinear finite element Method, differing primarily in the choice of the element basis functions and quadrature rules, the automation of the standard nonlinear finite element method is undertaken next. The automatic finite element formulation and assembly algorithm that constitutes the most significant contribution of this thesis is developed as an efficient numerical alternative to study the physics of wave propagation in nonlinear higher order structural models. The development of this algorithm and its extension to a general automatic framework for studying a large class of problems in nonlinear solid mechanics forms the second part of this research. Of special importance are the automatic handling of nonlinear plane stress configurations, hierarchic higher order waveguide models and the automatic coupling of continuum and higher order structural elements using specially designed transition elements that enable an efficient means to study waveguides with local inhomogeneities. In the third stage, the automatic algorithm is used to study wave propagation in hyperelastic waveguides using a few higher order 1D kinematic models. Two variants of a particular hyperelastic constitutive law – the6-constantMurnaghanmodel(for rock like solids) and the 9-constant Murnaghan model(for metallic solids) –are chosen for modeling the material nonlinearity in the analysis. Finally, the algorithm is extended to study energy-momentum conserving time integrators that are derived within a Hamiltonian framework, thus illustrating the extensibility of the algorithm for more complex finite element formulations. In short, the current research deals primarily with the identification and automation of finite element schemes that are most suited for studying wave propagation in hyper-elastic waveguides. Of special mention is the development of a novel unified computational framework that automates the finite element analysis of a large class of problems involving nonlinear plane stress/plane strain, higher order waveguide models and coupling of both continuum and waveguide elements. The thesis, which comprises of 10 chapters, provides a detailed account of various aspects of hyperelastic wave propagation, primarily for 1D waveguides.

Dans un contexte où les besoins en capteurs de gaz sont de plus en plus importants, en particulier pour la métrologie de l'environnement, il est proposé dans ce travail la réalisation de guides d'onde droits, de guides spirales, de jonctions Y,…, éléments indispensables pour la fabrication de micro-capteurs optiques infrarouges. La réalisation de ces différents éléments, par empilement et gravure de couches amorphes du système ternaire Ge-Se-Te, a nécessité en premier lieu l'étude du dit système. Des couches minces Ge-Se-Te de compositions très différentes ont été déposées par co-évaporation thermique, puis caractérisées en termes d'homogénéité, stabilité thermique, gap optique et indice de réfraction. L'évolution des propriétés en fonction de la composition a ensuite permis de mettre en évidence un domaine de compositions du système Ge-Se-Te particulièrement attractif : dans ce domaine, correspondant aux compositions riches en sélénium (plus de 55 % atomique) et contenant entre 20 et 30 % de germanium, les couches sont en effet monophasées, caractérisées par des températures de transition vitreuse élevées, une grande stabilité thermique, et un domaine de transparence s'étendant de 1 à 16 µm environ. Dans ce domaine de compositions, deux d'entre elles ont été choisies, Ge25Te10Se65 et Ge25Te20Se55, et utilisées pour fabriquer différents circuits d'optique intégrée. Les éléments les plus simples, à savoir des guides d'onde canaux, ont été réalisés en déposant successivement deux couches (Ge25Te10Se65 puis Ge25Te20Se55) sur un substrat silicium, puis en modifiant la géométrie de la couche supérieure d'indice de réfraction plus élevé par usinage ionique, de sorte à obtenir un confinement bidimensionnel de la lumière. Les pertes de propagation de ces guides ont été estimées à 1 dB.cm-1 à la longueur d'onde 1,55 µm. D'autres éléments plus complexes ont ensuite été fabriqués : des guides d'onde courbes pour lesquels les propriétés de guidage ont été obtenues quel que soit le rayon de courbure, des guides spirales ayant donné lieu à un bon guidage de la lumière, des jonctions Y caractérisées par une division satisfaisante de l'intensité lumineuse, ainsi que des interféromètres de type Mach-Zehnder en sortie desquels la lumière a été correctement recombinée. / In a context where the needs for gas sensors are increasingly important, especially for environmental metrology, it is proposed in this work to achieve straight waveguides, spirals, Y-junctions, ..., elements essential for the fabrication of infrared optical micro-sensors. The realization of these elements, by stacking and etching of amorphous thin films from the Ge-Se-Te ternary system, first required the study of this system. Ge-Se-Te thin films of very different compositions were deposited by thermal co-evaporation and characterized in terms of uniformity, thermal stability, optical band gap and refractive index. The evolution of the film properties with the composition was then used to highlight a particularly attractive area of compositions in the Ge-Se-Te system: in this domain, corresponding to compositions rich in Se (more than 55 atomic %) and containing between 20 and 30 atomic % in Ge, the layers are indeed single-phase, characterized by high glass transition temperatures, high thermal stability, and a transparency window extending from 1 to about 16 microns. In this composition region, two of them were selected, Ge25Te10Se65 and Ge25Te20Se55, and used to realize different integrated optics circuits. The simplest elements, which are channel waveguides, were made by depositing successively two layers (Ge25Te10Se65 then Ge25Te20Se55) on a silicon substrate, and then by modifying the geometry of the higher refractive index top layer by ion beam etching, so as to obtain a two-dimensional confinement of light. Propagation losses of these straight waveguides were estimated at 1 dB.cm-1 at the 1.55 µm wavelength. Other more complex elements were then fabricated: S-bent waveguides for which the guiding properties were obtained whatever the curvature radius, operational spiral waveguides, Y-junctions able of a satisfactory division of the light intensity, and Mach-Zehnder interferometers at the output of which the light was successfully recombined.

Dans le domaine de la nanophotonique, la compréhension des phénomènes optiques liés au guidage sub-longueur d'onde dans des structures pleines (nanofils) ou creuses (nanotubes) est un enjeu prioritaire. L'objectif de cette thèse a porté sur l'étude de la propagation lumineuse au sein de nouveaux guides d'onde nanométriques passifs et actifs. Pour cela, des nanofils et nanotubes à base de polymère ont été conçus et élaborés par méthode wetting template. Afin de caractériser leur comportement optique et en particulier la propagation sub-longueur d'onde, de nouveaux outils expérimentaux et numériques ont été développés. La modélisation des phénomènes propagatifs dans ces nanofibres a été effectuée par la méthode numérique FDTD. Les effets de la géométrie de ces nanofils et nanotubes, de par leurs dimensions (diamètres externe et interne pour les nanotubes) et du substrat sur le comportement propagatif et le niveau des pertes ont en particulier été déterminés. Sur le plan expérimental, deux types de nanofibres on été utilisés : - des nanofibres "passives" à base de polymère SU8 et - des nanofibres "actives" comportant un polymère guidant la lumière et un luminophore servant de source à l'échelle nanométrique. Pour l'étude des nanofibres de SU8, l'injection directe a été réalisée par le biais d'une fibre optique microlentillée. Un résultat marquant est l'évaluation des pertes optiques mesuré par la méthode cut- back autour de 1,25 dB/mm pour des nanotubes aux diamètres externes et internes respectivement de 240 nm et 120 nm. Cette évaluation de pertes optiques apparaît très compétitif comparativement à d'autres systèmes actuellement envisagés pour la nanophotonique intégrée. Concernant les nanofibres actives qui comportent des luminophores (cluster organométalliques ou polymère fluorescent PFO), nos études ont validé l'excitation du mode propre par caractérisation dans l'espace de Fourier. Nos résultats ont montré le potentiel de ces nanofibres organiques comme briques pour la nanophotonique. / In the field of nanophotonics, the understanding of optical phenomena related to sub-wavelength guiding in filled structures (nanowires) or hollow (nanotubes) is a priority. The objective of this thesis focused on the study of light propagation in new passive and active nanoscale waveguides. For this, nanowires and nanotubes based polymer has been designed and developed by template wetting method. To characterize their optical behavior and in particular the sub-wavelength propagation, new numerical and experimental tools have been developed. Modelling phenomena propagating in these nanofibers was performed by the numerical FDTD method. The effects of the geometry of these nanotubes and nanowires, by their size (outer and inner diameter for nanotubes) and propagating on the substrate and the behavior of losses have been determined in particular. Experimentally, two types of nanofibers have been used: - "passive" nanofibers based on SU8 polymer and - "active" polymer nanofibers having a waveguiding polymer and a luminophor as a source at nanoscale. To study nanofibers SU8, direct injection was performed through an microlensed optical fiber. A striking result is the assessment of optical losses measured by the cut-back around 1.25 dB/mm for nanotubes to external and internal diameters respectively 240 nm and 120 nm. This assessment of optical losses appear very competitive compared to other systems currently envisaged for integrated nanophotonics. Regarding the active nanofibers which comprise luminophors (organometallic cluster or fluorescent polymer PFO), our studies have validated the excitation of mode by characterization in Fourier space. Our results showed the potential of organic nanofibers as bricks for nanophotonics.

Dielectric High-frequency transmission lines are natural alternative to the lines made of metal in term of low loss. These lines are mainly used in microwave techniques of measuring. The main object is to describe basic parameters of metal and dielectric transmission lines and their comparison. Next point is a basic overview of the excitation the lines from metal and it's application on dielectric transmission lines. Then make the simulation of microstrip directional couplers and coupler made by dielectric waveguides. The last point of work is construction these directional couplers and measuring their most important parameters.

Cette thèse est une contribution à la modélisation et à l'étude expérimentale de cavités à cristaux photoniques à fente développées en vue d’un intégration hybride de matériaux actifs sur silicium. Parmi les travaux de conception, nous avons d'abord utilisé la méthodes des ondes planes et la méthode des différences finies (FDTD) pour concevoir une série de cavités SOI à hétérostructures, mécaniquement robustes, infiltrées par des liquides d’indices (n environ 1,5), présentant des longueurs d'onde de résonance dans la gamme des télécommunications (1,3 μm - 1,6 μm), des facteurs de qualité de plusieurs dizaines de milliers, et des volumes modaux proches de 0,03 (lambda/n)3. Nous avons ensuite étudié analytiquement et numériquement le couplage entre une cavité à cristaux photoniques à fente et un guide d'onde à fente par la théorie des modes couplés, complétée par des simulations FDTD, qui ont permis de confirmer la possibilité d'exciter efficacement les modes de fente des cavités à partir d'un guide externe. Enfin, nous avons étudié numériquement et semi-analytiquement des géométries de molécules photoniques constituées de deux cavités à cristaux photoniques à fentes couplées, dont l’écart fréquentiel entre les supermodes a pu être ajusté en amplitude et en signe. Nous avons utilisé une méthode perturbative (« Tight binding ») pour estimer les distributions spatiales des modes des molécules photoniques et prédire leurs fréquences dans plusieurs configurations de cavités à cristaux photoniques à fentes couplées.Ce travail exploratoire a été complété par une partie expérimentale qui a porté sur l'étude d'une famille de cavités de hétérostructure à cristaux photoniques à fente. Les cavités à cœur creux fabriquées ont montré des facteurs de qualité (Q) de plusieurs dizaines de milliers, associés à des volumes modaux de l’ordre de V=0,03 (λ/n)^3 après infiltration de la fente et des trous des structures par des liquides d'indice de réfraction proches de 1,46. Des facteurs Q/V supérieurs à 600 000 et atteignant 1 000 000 dans le meilleur des cas (vers lambda=1,3µm) ont ainsi été observés. Cette phase expérimentale préliminaire a donné ensuite lieu à deux types de développements.Tout d'abord, les propriétés des cavités à cristaux photoniques à fentes ont été étudiées pour des applications en détection d'indice en volume, et testées en utilisant différents liquides d'indice de réfraction compris entre 1,345 à 1,545. Les résonateurs étudiés ont présenté des sensibilités de ~ 235 nm / RIU et des facteur de mérite de détection d'indice de l’ordre de 3700, à l’état de l’art pour des résonateurs silicium intégrés à cœur creux.Dans une autre direction, le potentiel des résonateurs diélectriques à fente a été exploré en vue d’une intégration des matériaux actifs sur silicium. Un polymère dopé aux nanotubes de carbone semiconducteurs a été déposé comme matériau de couverture en vue d’étudier le renforcement de la photoluminescence (PL) des nano-émetteurs sous pompage optique vertical à lambda=740nm. Les expériences conduites ont permis de corréler le renforcement de la PL des nanotubes avec les modes de résonance des cavités et de démontrer le couplage partiel de cette PL vers des guides SOI longs de plusieurs millimètres (collection par la tranche vers lambda=1.3µm), apportant une preuve de principe d’une possible intégration des nanotubes émetteurs en photonique sur silicium. / This Ph.D. work is a contribution to the modeling and the experimental study of slot photonic crystal cavities for hybrid on-silicon integration. Among the design works, we first have used plane the wave expansion and finite-difference time-domain methods to design a series of mechanically robust (non-free membrane) SOI slot photonic crystal heterostructure cavities with resonance wavelengths in the telecommunication range, i.e. from 1.3 µm – 1.6 µm, with Q-factors of around several tens of thousands and mode volumes around 0.03(lambda/n)^3 after being infiltrated by cladding materials with typical index values around 1.5. We have then analytically and numerically studied the coupling between a slot photonic crystal cavity and a slot photonic crystal waveguide by using the coupled mode theory and FDTD simulation. Then we confirmed the ability to excite the cavity slot modes from a waveguide by using FDTD simulation. Finally, as a preliminary step towards the use of several coupled slotted cavities for future hybrid integration schemes, we have numerically and semi-analytically investigated photonic molecules made of two coupled slot photonic crystal cavities providing two different supermodes (bonding and antibonding ones) with controllable wavelength splitting. We successfully employed the tight-binding (TB) approach, which relies on the overlap of the two tightly confined cavity electric fields, to predict the supermodes frequencies and spatial distributions in several coupled slot photonic crystal cavity configurations.This exploratory work was supplemented by an experimental part, which focused on the investigation of a family of slot photonic crystal heterostructure cavities. The fabricated silicon on insulator hollow core cavities showed quality factors of several tens of thousands, i.e. from 18,000 to 31,000 and mode volume V of ~0.03(λ/n)3 after being infiltrated with liquids of ~1.46 refractive index, yielding Q/V ratio larger than 600,000, and reaching 1,000,000 in the best case (at λ ≈ 1.3 μm).This preliminary experimental stage gave rise to two types of additional developments.Firstly, the properties of the studied slot photonic crystal cavities have been investigated for index sensing applications by using different liquids with refractive index values ranging from 1.345 to 1.545. The considered photonic crystal resonators have demonstrated quality factors of several tens of thousands with sensitivities of ~235 nm/RIU and index sensing FOMs around 3,700, i.e. at the state of the art considering hollow core silicon integrated resonators.Secondly, in the view of the integration of active materials on silicon, the potential of these hollow core nanoresonators has been considered to enhance the photo-luminescence (PL) of semiconductor single-walled carbon nanotubes (SWNTs) integrated in thin films deposited on top of silicon. We have brought the first experimental demonstration of SWNTs PL collection (around lambda=1.28 µm) under vertical pumping at short wavelength (lambda=740 nm) from a slotted resonator into millimeter long integrated silicon waveguides, providing a first proof-of-concept step towards nanotube/Si-PhC integration as an active photonic platform. The reported works demonstrate the feasibility of integrating telecommunication wavelength nanotube emitters in silicon photonics as well as emphasize the role of slot photonic crystal cavities for on-chip hybrid integration.

Ce travail est consacré à l’étude de la génération de deuxième harmonique (SHG) dans des guides d’ondes de Nitrure d’éléments III. Un des buts principaux de ce travail, était d’identifier les origines des pertes à la propagation dans les guides d’ondes GaN et de fortement les réduire dans des guides présentant des possibilités d’accord de phase, pour améliorer l’efficacité de la SHG. Nous avons fait un progrès très important dans cette direction et avons fabriqué des guides d’ondes plans de GaN épitaxiés sur des substrats de saphir avec des pertes à la propagation inférieure à 1dB/cm dans le visible. Dans ces guides d’ondes à faibles pertes, il a été possible d’obtenir un processus de SHG efficace en utilisant l’accord de phase modal. Nous avons obtenu 2% de conversion entre une pompe dans le proche infrarouge et un harmonique dans le visible, ce qui correspond à une efficacité de conversion normalisée de 0,15%W-1cm-2. Les pertes à la propagation et l’efficacité de conversion obtenues sont les meilleurs résultats rapportés jusqu'ici pour des guides d’ondes plan en GaN. De plus, nous avons étudié des guides d’ondes de Nitrure d’éléments III épitaxiés sur des substrats de Si, dont la fabrication demande de relever plusieurs défis, mais qui ouvrent des possibilités intéressantes. La première est la possibilité de graver sélectivement les nitrures ou le Si, ce que nous avons utilisé pour développer une plate-forme permettant la fabrication d’objets suspendus comme des micro-disques, des guides d’ondes et des micro-disques couplés à un guide d’ondes. Cette plate-forme a permis la première démonstration de SHG doublement résonante en utilisant un accord de phase modal entre des modes de galerie du micro-disque. Bien que toutes les expériences que nous avons exécutées aient été faites dans une région spectrale limitée, l’étude numérique présentée dans ce manuscrit démontre la grande adaptabilité de cette plate-forme basée sur la possibilité de faire varier la composition des guides d’ondes AlGaN de GaN pur à AlN pur. La deuxième possibilité liée à l’épitaxie de nitrures d’éléments III sur Si, est qu'en la combinant avec des techniques de report, on peut jouer avec des guides nitrures d’éléments III sur SiO2. Nos résultats numériques révèlent le potentiel complet des guides d’ondes d’AlGaN en démontrant qu’en utilisant différentes combinaisons de mode et en jouant sur la composition et la géométrie des guides d’ondes, il est possible d’obtenir un signal de deuxième harmonique dans l’ultra-violet, le visible ou le proche-infrarouges. Ces résultats montrent aussi, que pour améliorer encore l’efficacité de la SHG, on doit fabriquer des guides d’ondes canaux présentant un isolement optique parfait du substrat de Si et une inversion de polarité précisément placée dans le cœur du guide d’ondes. Dans une telle structure on pourrait profiter simultanément du confinement de la puissance, de l’accord de phase modal et d’un recouvrement optimisé des modes en interaction. Dans ce cas, nos calculs montrent que l’efficacité de conversion pourrait atteindre 100%W-1cm-2. Au cours de ce travail nous avons pu tester des guides canaux et des guides présentant une inversion de polarité dans le cœur. La qualité des flancs des guides canaux s’est avérée être tout à fait encourageante, mais leur performance non linéaire sont restées très limitées, principalement à cause de fortes pertes à la propagation dues au couplage avec le substrat absorbant et à la forte rugosité de surface des couches inversées. Les structures utilisant les techniques de report, n'ont pu être testées car elles ont cassé en cour de fabrication. L'obtention de guides optimisés exige de progresser encore pour réaliser des couches de confinement optique plus épaisses et/ou d’adapter la technique de report à ces matériaux. / This work is dedicated to the study of the second harmonic generation (SHG) in III-Nitride waveguides. One of the main goals of this work, was to identify the origins of the propagation losses in GaN waveguides, and to strongly reduce them in waveguides presenting some phase matching possibilities, in order to improve the SHG efficiency. We have made a very important progress in this direction, and fabricated by hetero-epitaxy GaN planar waveguides on sapphire substrates with propagation losses below 1dB/cm in the visible spectral region. These low-loss waveguides were used for the demonstration of an efficient second harmonic generation process using modal phase matching. We obtained 2% of power conversion from the near-infrared to the visible spectral regions with a normalized efficiency of 0.15%W-1cm-2. The obtained propagation losses and conversion efficiency are the best-reported results so far for GaN planar waveguides. In addition, we have studied epitaxial III-nitride waveguides on Si substrates, which are very challenging to fabricate, but opens new interesting opportunities. The first one is the possibility to etch selectively the nitrides or the Si. The selective chemical etching was used to develop a platform allowing the fabrication of suspended objects such as micro-disks, waveguides and micro-disks coupled to a waveguide. This platform has allowed the first demonstration of doubly resonant SHG using phase matching between the whispering gallery modes of a micro-disk. Although all the experiments we performed were done in a limited spectral region, the numerical study presented in this manuscript demonstrates the large adaptability of this platform based on the possibility of varying the composition of AlGaN waveguides from pure GaN to pure AlN. The second opportunity of epitaxial III-nitrides layers on Si is the possibility to combine them with report technologies to obtain III-nitride waveguides on SiO2. Our numerical results reveal the full potential of AlGaN waveguides by demonstrating that using different mode combinations and playing with waveguides composition and geometry, it is possible to obtain a second harmonic signal in the ultraviolet, the visible or the near-infrared spectral regions. These results also demonstrate, that to further improve the SHG efficiency, one has to fabricate ridge waveguides presenting a perfect optical isolation from the Si substrate and a polarity inversion precisely positioned in the core of the waveguide. In these structures one could benefit simultaneously from the power confinement, the modal phase matching and an optimized overlap of the interacting modes. In this case, we calculate that the conversion efficiencies could be as high as 100%W-1cm-2. Both ridge waveguides and polarity inversion were tested in this work. The quality of the ridges was quite encouraging, but their nonlinear performance remained limited mainly because of the high propagation losses due to the coupling with the absorbing substrate and to the roughness of the surface of the epitaxial inverted layers. The structures fabricated using the report technique, haven’t been tested, as they were broken during their fabrication. Getting fully optimized waveguides requires further progresses in realizing thicker optical buffer layers and/or adapting the report technique to these materials.

A major focus is on integrated Silicon-based optoelectronics for the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive and portable optical sensors in the environmental control and medicine follows in the development of integrated high resolution sensors [1]. In particular, since 2013 the quick onsite verification of pathogens, like legionella in drinking water pipes, is becoming increasingly important [2, 3]. The essential questions regarding the establishment of portable biochemical sensors are the incorporation of electronic and optical devices as well as the implementations of fundamental cross-innovations between biotechnology and microelectronics. This thesis describes the design, fabrication and analysis of high-refractive-index-contrast photonic structures. Besides silicon nitride (Si3N4) strip waveguides, lateral tapers, bended waveguides, two-dimensional photonic crystals (PhCs) the focus lies on monolithically integrated waveguide butt-coupled Silicon-based light emitting devices (Sibased LEDs) [4, 5] for use as bioanalytical sensor components. Firstly, the design and performance characteristics as single mode regime, confinement factor and propagation losses due to the geometry and operation wavelength (1550 nm, 541 nm) of single mode (SM), multi mode (MM) waveguides and bends are studied and simulated. As a result, SM operation is obtained for 1550 nm by limiting the waveguide cross-section to 0.5 μm x 1 μm resulting in modal confinement factors of 87 %. In contrast, for shorter wavelengths as 541 nm SM propagation is excluded if the core height is not further decreased. Moreover, the obtained theoretical propagation losses for the lowestorder TE/TM mode are in the range of 0.3 - 1.3 dB/cm for an interface roughness of 1 nm. The lower silicon dioxide (SiO2) waveguide cladding should be at least 1 μm to avoid substrate radiations. These results are in a good correlation to the known values for common dielectric structures. In the case of bended waveguides, an idealized device with a radius of 10 μm was developed which shows a reflection minimum (S11 = - 22 dB) at 1550 nm resulting in almost perfect transmission of the signal. Additionally, tapered waveguides were investigated for an optimized light coupling between high-aspect-ratio devices. Here, adiabatic down-tapered waveguides were designed for the elimination of higher-order modes and perfect signal transmission. Secondly, fabrication lines including Electron-beam (E-beam) lithography and reactive ion etching (RIE) with an Aluminum (Al) mask were developed and lead to well fabricated optical devices in the (sub)micrometer range. The usage of focused ion beam (FIB) milling is invented for smoother front faces which were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result, the anisotropy of the RIE process was increased, but the obtained surface roughness parameters are still too high (10 – 20 nm) demonstrating a more advanced lithography technique is needed for higher quality structures. Moreover, this study presents an alternative fabrication pathway for novel designed waveguides with free-edge overlapping endfaces for improving fiber-chipcoupling. Thirdly, the main focus lies on the development of a monolithic integration circuit consisting of the Si-based LED coupled to an integrated waveguide. The light propagation between high-aspect-ratio devices is enabled through low-loss adiabatic tapers. This study shows, that the usage of CMOS-related fabrication technologies result in a monolithic manufacturing pathway for the successful implementation of fully integrated Si-based photonic circuits. Fourth, transmission loss measurements of the fabricated photonic structures as well as the waveguide butt-coupled Si-based LEDs were performed with a generated setup. As a result, free-edge overlapping MM waveguides show propagation loss coefficients of ~ 65 dB/cm in the range of the telecommunication wavelength. The high surface roughness parameters (~ 150 nm) and the modal dispersion in the core are one of the key driving factors. These facts clearly underline the improvement potential of the used fabrication processes. However, electroluminescence (EL) measurements of waveguide butt-coupled Si-based LEDs due to the implanted rare earth (RE) ion (Tb3+, Er3+) and the host material (SiO2/SiNx) were carried out. The detected transmission spectra of the coupled Tb:SiO2 systems show a weak EL signal at the main transition line of the Tb3+-ion (538 nm). A second emission line was detected in the red region of the spectrum either corresponding to a further optical transition of Tb3+ or a Non Bridging Oxygen Hole Center (NBOHC) in SiO2. Unfortunately, no light emission in the infrared range was established for the Er3+-doped photonic circuits caused by the low external quantum efficiencies (EQE) of the Er3+ implanted Si-based LEDs. Nevertheless, transmission measurements between 450 nm – 800 nm lead again to the result that an emission at 650 nm is either caused by an optical transition of the Er3+-ion or initialized by the NBOHC in the host. Overall, it is difficult to assess whether or not these EL signals are generated from the implanted ions, thus detailed statements about the coupling efficiency between the LED and the integrated waveguide are quite inadequate. Nevertheless, the principle of a fully monolithically integrated photonic circuit consisting of a Si-based LED and a waveguide has been successfully proven in this study.

Le confinement électrique et optique par oxydation des couches minces d'AlGaAs est une étape essentielle dans la réalisation des composants photoniques actifs et passifs dans la filière de matériaux GaAs. La recherche de performances ultimes sur ces composants nécessite une meilleure maîtrise du procédé d'oxydation ainsi qu'une meilleure connaissance des propriétés optiques de l'oxyde d'aluminium (AlOx). Dans cette perspective, j'ai d'abord réalisé une étude expérimentale de la vitesse d'oxydation des couches d'AlGaAs en fonction de la température du substrat, de la composition en gallium des couches étudiées, de la pression atmosphérique et de la géométrie des mesas considérés. Puis, j'ai établi un modèle anisotrope permettant une meilleure résolution spatiale et temporelle de la forme du front d'oxydation de l'AlAs. Enfin, j'ai exploité ce procédé pour réaliser des composants d'optique guidée notamment des micro-résonateurs puis réalisé des guides optiques à fente et caractérisé leurs performances optiques. / Optical and electrical confinement using Al(Ga)As layer oxidation is a key milestone in the fabrication of active and passive GaAs-based photonic components. To optimize those devices, through the control of the optical and electrical confinements, a better modelling of oxidation process and a better understanding of optical properties of aluminum oxide (AlOx) is required. One part of this work is focusing on a throughout experimental study of AlGaAs oxidation kinetics, where I studied different important parameters such as wafer temperature, gallium composition, atmospheric pressure and mesa geometry. Then, I developed a new predictive model taking into account the process anisotropy, thus allowing a better temporal and spatial of AlAs oxidation front evolution. Finally, I could exploit this technological process to realize whispering gallery mode microdisks as well as slot optical waveguides, and I have characterized this latter photonic devices.

Industrial innovation is mostly driven by miniaturization. As a result of remarkable technological advancements in the fields of equipment, materials and production processes, transistor, the fundamental active component in conventional electronics, has shrunk in size. Semiconductor technology is unique in that all performance metrics are enhanced, while at the same time unit prices are reduced. Moore’s Law, which predicts that the number of components per chip will double every two years, was established in 1965, and the industry has been able to keep up with this prophetic prognosis since. Thermal management, on the other hand, has become a key limiting factor for current electronic circuits and is set to put a stop to Moore’s Law. Given the fact that complementary metal oxide semiconductor (CMOS) scaling is reaching fundamental limits, there are several new alternative processing devices and architectures that have been investigated for both traditional integrated circuit (IC) technologies and novel technologies, including new technologies aimed at contributing to advances in scaling progress and cost reductions in manufacturing operations in the coming decades. These factors will encourage the development of new information processing and memory systems, new technologies for integrating numerous features heterogeneously and new system architectural design layouts, among other things. Energy efficiency is advantageous from a sustainability perspective and for consumer electronics, for which fewer power-hungry components mean longer times between charges and smaller batteries. The creation of novel chip-scale tools that can aid in the transfer of information across optical frequencies and microscale photonics between nanoscale electronic devices is now a possibility. Bridging this technological gap may be achieved by plasmonics. The incorporation of plasmonic, photonic and electrical components on a single chip may lead to a number of innovative breakthroughs. Photonic integrated circuits (PICs) enable the realization of ultra-small, high-efficiency, ultra-responsive and CMOS-compatible devices that can be used in applications ranging from optical wireless communication systems (6G and beyond) and supercomputers to health and energy.   This thesis provides a platform from which to design nanoplasmonic devices while facilitating high-transmission and/or absorption efficiency, miniaturized size and the use of near-infrared (NIR) wavelengths for telecom applications. With a significant amount of Internet traffic transmitted optically, communication systems are further tightening the requirements for the development of new optical devices. Several new device structures based on the metal-insulator-metal (MIM) plasmonic waveguide are proposed and investigated using performance metrics. The transmission line theory (TLM) from microwave circuit theory and coupled mode theory (CMT) is studied and employed in the design process of the nanostructures, in particular to address the losses in plasmonic-based devices, which has been the major factor hampering their widespread usage in communication systems. By taking advantage of well-established microwave circuit theory (through new design that paves the way for mitigating these losses and enabling efficient transmission of power flow in the optical devices), we have suggested a number of high-transmission efficiency nanodevices that offer highly competitive performance compared with other platforms. As a result, a promising future for plasmonic technology, which would enable design and fabrication of multipurpose and multifunctional optical devices that are efficient in terms of losses, footprint and capability of integrating active devices, is anticipated. / Branschinnovation drivs främst av miniatyrisering. Som ett resultat av anmärkningsvärda tekniska framsteg inom områdena utrustning, material och produktionsprocesser kunde transistoren, den grundläggande aktiva komponenten i samtida elektronik, krympa i storlek. Halvledarteknik är unik genom att alla prestandamått förbättras, samtidigt som enhetspriserna sänks. Moores Lag, som förutspår att antalet komponenter per chip skulle fördubblas vartannat år, inrättades 1965, och branschen har kunnat hålla jämna steg med den profetiska prognosen sedan dess. Termisk hantering, å andra sidan, har blivit en viktig begränsande faktor för nuvarande elektroniska kretsar, och är inställd på att sätta stopp för Moores Lag. Med tanke på att CMOS-skalningen (Complementary Metal Oxide Semiconductor) når grundläggande gränser finns det flera nya alternativa bearbetningsanordningar och arkitekturer som har undersökts för både traditionell integrerad kretsteknik och ny teknik. Ny teknik som syftar till att bidra till framsteg i skalningen av framsteg och kostnadsminskningar i tillverkningsverksamheten under de kommande årtiondena. Dessa faktorer uppmuntrar utvecklingen av nya informationsbehandlings- och minnessystem, ny teknik för att integrera många funktioner heterogent och nya systemarkitekturdesignlayouter, bland annat. Energieffektivitet är fördelaktigt ur ett hållbarhetsperspektiv och för hemelektronik, där färre krafthungriga elektroniker innebär längre tid mellan laddningar och stimulerar för ett mindre energilagringssystem ombord. Skapandet av nya chip-scale verktyg som kan bidra till överföring av information över optiska frekvenser och mikroskala fotonik mellan elektroniska enheter i nanoskala är nu en möjlighet. Överbrygga denna tekniska klyfta kan uppnås av plasmonics. Införlivandet av plasmoniska, fotoniska och elektriska komponenter på ett enda chip kan leda till ett antal innovativa genombrott. Fotoniska integrerade kretsar (PIC-enheter) möjliggör förverkligande av ultrasmå, högeffektiva, ultraresponsiva och CMOS-kompatibla enheter som kan användas i applikationer som sträcker sig från optiska trådlösa kommunikationssystem (6G och därefter), superdatorer till hälso- och energiändamål. Denna avhandling ger en plattform för att designa nanoplasmoniska enheter samtidigt som den innehåller hög överförings- och eller absorptionseffektivitet, miniatyriserad storlek och vid önskade våglängder av nära infraröd (NIR) för telekomapplikationer. Med den betydande mängden Internettrafik som överförs optiskt skärper kommunikationssystemen ytterligare kraven för utveckling av nya optiska enheter. Flera nya enhetsstrukturer baserade på metall-isolator-metall (MIM) plasmonisk vågledare föreslås och numeriskt undersöks. Överföringslinjeteorin (TLM) från mikrovågskretsteori och kombinationslägesteori (CMT) studeras och används i nanostrukturerna. För att ta itu med de förluster i plasmonbaserade enheter som har varit den viktigaste parametern som hindrade deras utbredda användning i kommunikationssystem, genom att dra nytta av den väletablerade mikrovågskretsteorin (genom ny design som banar väg för att mildra förlusterna och möjliggöra effektiv överföring av kraftflödet i den optiska enheten).  Vi har framgångsrikt föreslagit ett antal nanodevices med hög överföringseffektivitet som erbjuder en mycket konkurrenskraftig prestanda jämfört med andra plattformar. Som ett resultat förväntar vi oss en lovande framtid för plasmonisk teknik som skulle möjliggöra design och tillverkning av mångsidiga och multifunktionella optiska enheter som är effektiva när det gäller förluster, fotavtryck och förmåga att integrera aktiva enheter. / <p>Vid tidpunkten för framläggandet av avhandlingen var följande delarbeten opublicerade: delarbete II inskickat, III, IV, V manuskript.</p><p>At the time of the licentiate defence the following papers were unpublished: paper II submitted, III, IV, V manuscript.</p>

[pt] Neste presente trabalho, o Método do Casamento de Modos é aplicado na análise e no projeto de estruturas coaxiais. A estrutura de excitação é um dos pontos críticos do projeto de antenas do tipo discone quando se pretende explorar suas características de banda larga. Seções não uniformes de guias de ondas coaxiais são usualmente utilizadas como elementos dessa estrutura de excitação sendo, eventualmente, necessária a inclusão de anéis dielétricos para garantir a rigidez mecânica da antena. Devido a essas não uniformidades encontradas nas dimensões e no meio dielétrico desse dispositivo de microondas, métodos numéricos serão utilizados na predição do seu comportamento eletromagnético. O correto dimensionamento desses anéis e das descontinuidades de guias de onda coaxiais que compõe a estrutura de alimentação, permite estabelecer um compromisso entre minimização das perdas, alargamento da banda passante e rigidez mecânica. Associados ao Método do Casamento de Modos serão utilizados algoritmos de otimização que farão o ajuste das dimensões dessas seções de guias de onda coaxiais não uniformes, visando à minimização da perda de retorno e o aumento da banda de operação da antena. Finalmente, será feito o estudo de algumas estruturas de excitação, onde serão otimizados seus desempenhos para a perda de retorno. / [en] In this present work, the Mode Matching technique is applied in the analysis and project of coaxial structures. The feed junction is one of the critical points of the project of discone antennas when broadband performance is expected. Usually, these junctions are composed of nonuniform sections of coaxial waveguide and, to guarantee the necessary mechanical rigidity of the structure, some sections are filled with dielectric material. The project of these feed junctions requires a compromise between frequency band, compact structure, minimal losses, and mechanical rigidity. Due to the discontinuities, numerical methods are used to predict the electromagnetic behavior. Here, Mode Matching technique associated with an optimization algorithm is employed in the adjustment of the dimensions of the coaxial waveguide sections, seeking the minimization of the return loss and the enlargement of the antenna bandwidth. Several types of junctions are explored and their performance is compared.