Non-reciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counter-propagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one direction only. Given the popularity of photonic integrated circuits (PIC), in which all the optical components are fabricated on the same chip so that the entire optical system can be made more compact, it is desirable to have an easily integrated optical isolator. Common free-space optical isolator designs, which rely on the Faraday effect, are limited by the availability of suitable magnetic materials. This research proposes a novel integrated optical isolator based on an array of closely spaced, identical waveguides. Because of the nonlinear optical properties of the material, this device exploits the differing behaviors of such an array when illuminated with either a high power or a low power beam to achieve non-reciprocal wave transmission in the forwards and backwards directions, respectively. The switching can be controlled electro-optically via an integrated gain section which provides optical amplification before the input to the array. The design, fabrication, characterization and testing of this optical isolator are covered in this dissertation. We study the switching dynamics of this device and present its optimum operating conditions.

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Interference between the modes of an optical fiber results in specific intensity patterns which can be modulated as a function of disturbances in the optical fiber system. These modulation effects are a direct result of the difference in propagation constants of the constituent modes. In this presentation it is shown how the modulated intensity patterns created by the interference of specific mode groups in few-mode optical fibers (V < 5.0) can be used to detect strain. A detailed discussion of the modal phenomena responsible for the observed strain induced pattern modulation is given and it is shown that strain detection sensitivities on the order of 10-9 can be expected. Data taken during the evaluation of an actual experimental strain detection system based on the developed theory is also presented. / Master of Science

L'augmentation du trafic de données met énormément de pression sur les systèmes de communications par fibre optique qui doivent répondre à la demande tout en maintenant les coûts d'opération et la consommation énergétique les plus faibles possibles. Pour palier à ce problème, une solution intéressante consiste à utiliser des interconnections optiques reconfigurables ne nécessitant peu ou pas de conversion électro-optique intermédiaire, notamment dans les centres de données. On parle ici de transparence dans les réseaux optiques. Pour concevoir ces dispositifs photoniques, la plateforme intégrée silicon-on-insulator (SOI) est très prometteuse. En effet, elle offre la possibilité de concevoir des composants intégrés qui sont compacts, polyvalents, évolutifs et sophistiqués, le tout en réduisant les coûts de production. Ce mémoire porte sur l'étude, sur la conception et sur la fabrication de filtres à micro-cavités en anneau d'ordre élevé sur SOI et à leur utilisation dans des systèmes de multiplexage en longueur d'onde reconfigurables, transparents et insensibles à la polarisation. L'objectif de ce travail est plus particulièrement d'adresser le défi complexe qui consiste à développer un système de ce type, possédant toutes les caractéristiques visées par les équipements qui sont déployés à grande échelle. La première partie de ce travail a comme objectif de présenter les systèmes de communications optiques et le problème qui est adressé dans son contexte. C'est aussi à ce moment que sera introduite en détails la plateforme SOI qui offre des outils pour répondre au problème. Ensuite, en seconde partie, il sera question des filtres à micro-cavité en anneau et des méthodes de design permettant de les modéliser afin de les intégrer dans des systèmes complexes. Ces filtres sont cependant très sensibles au processus de fabrication et il est donc nécessaire de présenter un méthodologie permettant de corriger leur réponse en post-fabrication, chose qui sera faite en troisième partie. Enfin, la dernière section de ce travail de recherche porte sur l'intégration des concepts développés dans les sections précédentes afin de bâtir un système complet de multiplexage en longueur d'onde reconfigurable, transparent et insensible en polarisation. Enfin, même s'il reste beaucoup de travail d'analyse et de conception devant nous, cette recherche montre de manière non-exhaustive les avantages et les limitations fondamentales que peuvent avoir les filtres à micro-résonateurs en anneau implémentés dans les réseaux transparents reconfigurables. / Increase in data traffic puts a lot of pressure on optical communication systems which must provide for its users while maintaining operation costs and energy consumption as low as possible. A solution to overcome those problems consists in using reconfigurable optical inter-connects which do not require any electro-optical conversion, especially in data centers. This is known as optical network transparency. In order to build the optical components required to implement optical network transparency, the silicon-on-insulator (SOI) platform provides very promising solutions. It offers the possibility to design highly-scalable integrated devices with a small footprint and low fabrication costs. This memoir aims to study the design and fabrication of high-order microring resonator filters on the SOI platform and their usage in reconfigurable, transparent and polarization insensitive wavelength division multiplexing (WDM) optical communications systems. The main goal of this work is to address the complex challenges of designing such components for widespread usage, having all the specifications that are required for their implementation. In the first part of this work, optical communications systems and the problem that will be addressed will be discussed in its context. At this point, the silicon-on-insulator platform which offers helpful tools for responding to the issue will be introduced. Then, in the second part, high-order microring filters will be introduced as a solution and their principles and applications will be discussed. Those filters are unfortunately very sensitive to the fabrication process and it is thus necessary to discuss the methodology required in order to mitigate those effects at the post-fabrication level. This methodology will be discussed in the third part of this work. Then, in the final part of this memoir, all the concepts previously introduced will be consolidated in order to build a complete reconfigurable and transparent WDM system that is insensitive to polarization. There is still a lot of work ahead of us and even though this research is not exhaustive, it shows the advantages as well as fundamental limitations of high-order microring filters when implemented in transparent and reconfigurable optical networks.

Titre de l'écran-titre (visionné le 29 juin 2023) / Le polydiméthylsiloxane (PDMS) est un matériau polyvalent en raison de sa biocompatibilité, de son inertie, de sa durabilité, de son élasticité, de sa transparence, de son faible coût, de sa grande disponibilité et de sa facilité de fabrication. Ce matériau a prouvé son importance dans de nombreux domaines en agissant comme matériau hôte pour les nanoparticules et le milieu de gain pour produire un système laser aléatoire largement ajustable. La photosensibilité des matériaux est un paramètre clé pour la fabrication de dispositifs pour une variété d'applications telles que les télécommunications, la détection et les lasers. Par conséquent, cette thèse porte sur une méthodologie expérimentale de fabrication de nouveaux matériaux photosensibles à base de PDMS ainsi que sur l'élaboration d'un laser aléatoire élastomère stable (SERL) composé en combinaison avec un matériau inorganique, Nd:YAB (NdxY1-xAl₃B₄O₁₂), les intégrer dans des guides d'ondes photoniques en silicone et explorer leurs applications. Tout d'abord, des stratégies ont été développées pour rendre le PDMS photosensible pour l'écriture femtoseconde (fs). Nous avons utilisé un laser femtoseconde pour écrire directement dans les PDMS, ainsi que de matériaux vitreux photosensibles sous la forme de PDMS chargés de nouveaux dérivés de germanium (Ge) et d'autres initiateurs pouvant agir en tant que photosensibilisateurs, afin d'obtenir le changement d'indice de réfraction le plus élevé sans compromettre de manière significative, conduisant à une écriture optimale de guides d'ondes ou de dispositifs photoniques dans un tel hôte souple. De plus, des réseaux de diffraction de Bragg hautement accordables ont été intégrés à l'intérieur des PDMS. Pour le développement de futurs dispositifs, nous avons exploré l'effet de l'écriture laser fs sur la structure du polymère ainsi que de leurs propriétés mécaniques et optiques. Ensuite, dans la deuxième approche de cette étude de doctorat, un système de laser aléatoire élastomère (SERL) très stable composé de deux matériaux stables : nanoparticules inorganiques Nd:YAB (NdₓY₁₋ₓ Al₃(BO₃)₄) et polydiméthylsiloxane (PDMS) a été fabriqué. Ce RL très stable est le premier système élastomère, donc accordable, qui permet l'étude systématique de la stabilité. Nous avons pu explorer les aspects d'adaptabilité du système RL en étirant le composite PDMS et en explorant l'aspect multidirectionnel du laser. En tant qu'application nécessitant un fonctionnement à long terme, un comportement statistique de type Lévy a également été démontré. / Polydimethylsiloxane (PDMS) is a versatile material due to its biocompatibility, inertness, durability, elasticity, transparency, low cost, wide availability, and ease of manufacture. This material has proved its importance in many fields by acting as a host material for nanoparticles and gain medium to produce a widely tunable random lasing system. Photosensitivity of materials has been shown to be a key parameter for the fabrication of devices for a variety of applications such as in telecommunications, sensing and lasers. Hence, this thesis involves the experimental methodology for fabricating novel photosensitive materials based on PDMS as well as the realization of a Stable Elastomeric Random Laser (SERL) composed in combination with an inorganic material, Nd:YAB (NdₓY₁₋ₓAl₃B₄O₁₂), for integration into silicone photonic waveguides and exploration of potential applications. Firstly, a strategy has been developed to render PDMS photosensitive for femtosecond (fs) writing. We then used a femtosecond laser to write directly into PDMS, as well as into a new photosensitive glassy material in the form of PDMS loaded with novel germanium (Ge)-derivatives and other initiators as photosensitizers. This combination yielded a higher refractive index material for optimal writing of waveguides or photonic devices in a very soft host. In addition, for the first time to the best of our knowledge, highly tunable Bragg diffraction gratings were embedded inside the bulk PDMS. For future device engineering, the effect of fs laser writing on the polymer structure, mechanical and optical properties has been explored. Then, in the second approach of a very stable elastomeric random laser (SERL) system composed of two stable materials: inorganic Nd:YAB (NdₓY₁₋ₓ Al₃(BO₃)₄)-nanoparticles and polydimethylsiloxane (PDMS) has been fabricated. This very stable RL is the first elastomeric system, hence tunable, which allows the systematic investigation of stability. The tunability aspects of the RL system has been investigated by stretching the PDMS composite and explored the multi-directionality of lasing. As an application which requires long term operation, Levy-like statistical behavior were also demonstrated.

Attenuated total reflection techniques have been used extensively as analytical tools for the analysis of thin films and analytes imbedded in complex scattering matrices. However they have not been commonly utilized as detectors in common analytical techniques such as Flow Injection Analysis because of their relatively low sensitivity. The feasibility of using a thin film planar waveguide as an absorption sensor in the Flow Injection Analysis of Urea was investigated. Urea was hydrolyzed to ammonia and carbon dioxide with the enzyme Urease. The ammonia produced was quantitated colorimetrically using Berthelot’s reaction. The reaction product, indophenol blue, was detected using the combination planar waveguide 9.2 microliter flow cell sensor. The planar waveguides used had 2 to 3 orders of magnitude greater sensitivity than typical internal reflection elements. The analytical working range obtained for urea determinations was from 0 to 20 mM urea at a rate of 30 samples per hour. A description of the investigation and the various factors involved in designing and optimizing a planar waveguide for absorption spectrometry is included. / Ph. D.

The scattering of acoustic waves by boundary discontinuities in waveguides is analyzed using the Method of Matched Asymptotic Expansions (MAE). Existing theories are accurate only for very low frequencies. In contrast, the theory developed in this thesis is valid over the entire range of frequencies up to the first cutoff frequency. The key to this improvement lies in recognizing the important physical role of the cutoff cross-modes of the waveguide, which are usually overlooked. Although these modes are evanescent, they contain information about the interaction between the local field near the discontinuity and the far-field. This interaction has a profound effect on the far-field amplitudes and becomes increasingly important with frequency. The cutoff modes also present novel mathematical problems in that current asymptotic techniques do not offer a rational means of incorporating them into a mathematical description. This difficulty arises from the non-Poincare form of the cross-modes, and its resolution constitutes the second new result of this thesis. We develop a matching scheme based on block matching intermediate expansions in a transform domain. The new technique permits the matching of expansions of a more general nature than previously possible, and may well have useful applications in other physical situations where evanescent terms are important. We show that the resulting theory leads to significant improvements with just a few cross-mode terms included, and also that there is an intimate connection with classical integral methods. Finally, the theory is extended to waveguides with slowly varying shape. We show that the usual regular perturbation analysis of the wave regions must be completely abandoned. This is due to the evanescent nature of the cross-modes, which must be described by a WKB approximation. The pressure field we so obtain includes older results. The new terms account for the cutoff cross-modes of the variable waveguide, which play a central role in extending the dynamic range of the theory. / Ph. D.