[EN] Microwave photonics (MWP) is a well-established research field that investigates the use of photonic technologies to generate, distribute, process and analyze RF waveforms in the optical domain. Despite its great potential to solve long-standing problems faced by both the microwave and electronics industries, MWP systems are bulky, expensive and consume a lot of power. Integrated microwave photonics (IMWP) is an emerging area of research that promises to alleviate most of these drawbacks through the use of photonic integrated circuits (PIC). In this work, we have aimed at further closing the gap between the worlds of MWP and integrated optics. In particular, we have focused on the design and experimental characterization of PICs with reconfigurable, ring-assisted Mach-Zehnder interferometer filters (RAMZI), and demonstrated its potential use in different IMWP applications. These filters consist of a symmetric MZI loaded with ring resonators, which are coupled to the MZI branches by different optical couplers. The contributions of this thesis can be split into two sections. In the first one, we demonstrate integrated optical couplers and reflectors with variable power splitting and reflections ratios. These exploit the well-known properties of tapered multimode interference couplers (MMI), and their inherent robustness makes them highly suitable for the implementation of both RAMZI and reflective filters. Besides, we study in detail the impact of manufacturing deviations in the performance of a 4x4 MMI-based 90º hybrid, which is a fundamental building block in coherent optical communication systems. In the second section, we demonstrate the use of integrated RAMZI filters for three different IMWP applications, including instantaneous frequency measurement (IFM), direct detection of frequency-modulated signals in a MWP link, as well as in tunable, coherent MWP filters. A theoretical analysis of the limits and trade-offs that exist in photonics-based IFM systems is also provided. Even though these are early proof-of-concept experiments, we hope that further technological developments in the field will finally turn MWP into a commercial reality. / [ES] La fotónica de microondas (MWP) es un campo de investigación que estudia el uso de tecnologías ópticas para generar, distribuir, procesar y analizar señales de RF. A pesar de su gran potencial para resolver algunos de los problemas a los que se enfrentan las industrias electrónica y de microondas, estos sistemas son voluminosos, caros y consumen mucha potencia. La fotónica de microondas integrada (IMWP) es un área emergente que promete solucionar todos estos inconvenientes a través de la utilización de circuitos ópticos integrados (PIC). En esta tesis, hemos pretendido avanzar un poco más en el acercamiento entre estas dos disciplinas. En concreto, nos hemos centrado en el diseño y caracterización experimental de PICs con filtros reconfigurables basados en interferómetros Mach-Zehnder cargados con anillos (RAMZI), y demostrado su potencial uso en diferentes aplicaciones de IMWP. Los filtros RAMZI están hecho básicamente de un MZI simétrico cargado con anillos, los cuales a su vez se acoplan a las ramas del interferómetro a través de distintos acopladores ópticos. Las contribuciones de este trabajo se pueden dividir en dos partes. En la primera, hemos demostrado acopladores y reflectores ópticos integrados con coeficientes de acoplo y reflexión variables. Éstos explotan las propiedades de los acopladores por interferencia multimodal (MMI), y su robustez les hace muy atractivos para la implementación de filtros RAMZI y de tipo reflectivo. Además, hemos analizado el impacto que las tolerancias de fabricación tienen en el rendimiento de un híbrido óptico de 90º basado en un MMI 4x4, el cual es un elemento fundamental en los sistemas de comunicaciones ópticas coherentes. En la segunda parte, hemos demostrado el uso de filtros RAMZI en tres aplicaciones distintas de IMWP. En concreto, hemos utilizado dichos filtros para implementar sistemas de medida de frecuencia instantánea (IFM), detección directa de señales moduladas en frecuencia para enlaces fotónicos, así como en filtros coherentes y sintonizables de MWP. También hemos desarrollado un análisis teórico de las limitaciones y problemas que existen en los sistemas IFM. A pesar de que todos los experimentos realizados han consistido en prototipos para una prueba de concepto, esperamos que futuros avances tecnológicos permitan que la fotónica de microondas se convierta algún día en una realidad comercial. / [CAT] La fotònica de microones (MWP) és un camp d'investigació que estudia l'ús de tecnologies òptiques per a generar, distribuir, processar y analitzar senyals de radiofreqüència. A pesar del seu gran potencial per a resoldre alguns dels problemes als que s'enfronten les indústries electrònica i de microones, estos sistemes son voluminosos, cars i consumixen molta potència. La fotònica de microones integrada (IMWP) és un àrea emergent que promet solucionar tots estos inconvenients a través de la utilització de circuits òptics integrats (PIC). En esta tesi, hem pretés avançar un poc més en l'acostament entre estes dos disciplines. En concret, ens hem centrat en el disseny i caracterització experimental de PICs amb filtres reconfigurables basats en interferòmetres Mach-Zehnder carregats amb anells (RAMZI), i demostrat el seu potencial en diferents aplicacions d' IMWP. Els filtres RAMZI estan fets bàsicament d'un MZI simètric carregat amb anells, els quals, al seu torn, s'acoblen a les branques del interferòmetre a través de distints acobladors òptics. Les contribucions d'este treball es poden dividir en dos parts. En la primera, hem demostrat acobladors i reflectors òptics integrats amb coeficients de transmissió i reflexió variables. Estos exploten les propietats dels acobladors per interferència multimodal (MMI), i la seua robustesa els fa molt atractius per a la implementació de filtres RAMZI i de tipo reflectiu. A més a més, hem analitzat l'impacte que les toleràncies de fabricació tenen en el rendiment d'un híbrid òptic de 90 graus basat en un MMI 4x4, el qual és un element fonamental en els sistemes de comunicacions òptiques coherents. En la segona part, hem demostrat l'ús de filtres RAMZI en tres aplicacions diferents de IMWP. En concret, hem utilitzat estos filtres per a implementar sistemes de mesura de freqüència instantània (IFM), detecció directa de senyals modulades en freqüència per a enllaços fotònics, així com en filtres coherents i sintonitzables de MWP. També hem desenvolupat una anàlisi teòrica de les limitacions i problemes que existixen en els sistemes IFM. A pesar de que tots els experiments realitzats han consistit en prototips per a una prova de concepte, esperem que futurs avanços tecnològics permeten que la fotònica de microones es convertisca algun dia en una realitat comercial. / Sánchez Fandiño, JA. (2016). Integrated Optical Filters for Microwave Photonic Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/67690 / TESIS

El silicio es la plataforma más prometedora para la integración fotónica, asegurando la compatibilidad con los procesos de fabricación CMOS y la producción en masa de dispositivos a bajo coste. Durante las últimas décadas, la tecnología fotónica basada en la plataforma de silicio ha mostrado un gran crecimiento, desarrollando diferentes tipos de dispositivos ópticos de alto rendimiento. Una de las posibilidades para continuar mejorando las prestaciones de los dispositivos fotónicos es mediante la combinación con otras tecnologías como la plasmónica o con nuevos materiales con propiedades excepcionales y compatibilidad CMOS. Las tecnologías híbridas pueden superar las limitaciones de la tecnología de silicio, dando lugar a nuevos dispositivos capaces de superar las prestaciones de sus homólogos electrónicos. La tecnología híbrida dióxido de vanadio/ silicio permite el desarrollo de dispositivos de altas prestaciones, con gran ancho de banda, mayor velocidad de operación y mayor eficiencia energética con dimensiones de la escala de la longitud de onda. El objetivo principal de esta tesis ha sido la propuesta y desarrollo de dispositivos fotónicos de altas prestaciones para aplicaciones de conmutación. En este contexto, diferentes estructuras basadas en silicio, tecnología plasmónica y las propiedades sintonizables del dióxido de vanadio han sido investigadas para controlar la polarización de la luz y para desarrollar otras funcionalidades electro-ópticas como la modulación. / Silicon is the most promising platform for photonic integration, ensuring CMOS fabrication compatibility and mass production of cost-effective devices. During the last decades, photonic technology based on the Silicon on Insulator (SOI) platform has shown a great evolution, developing different sorts of high performance optical devices. One way to continue improving the performance of photonic optical devices is the combination of the silicon platform with another technologies like plasmonics or CMOS compatible materials with unique properties. Hybrid technologies can overcome the current limits of the silicon technology and develop new devices exceeding the performance metrics of its counterparts electronic devices. The vanadium dioxide/silicon hybrid technology allows the development of new high-performance devices with broadband performance, faster operating speed and energy efficient optical response with wavelength-scale device dimensions. The main goal of this thesis has been the proposal and development of high performance photonic devices for switching applications. In this context, different structures, based on silicon, plasmonics and the tunable properties of vanadium dioxide, have been investigated to control the polarization of light and for enabling other electro-optical functionalities, like optical modulation. / El silici és la plataforma més prometedora per a la integració fotònica, assegurant la compatibilitat amb els processos de fabricació CMOS i la producció en massa de dispositius a baix cost. Durant les últimes dècades, la tecnologia fotònica basada en la plataforma de silici ha mostrat un gran creixement, desenvolupant diferents tipus de dispositius òptics d'alt rendiment. Una de les possibilitats per a continuar millorant el rendiment dels dispositius fotònics és per mitjà de la combinació amb altres tecnologies com la plasmònica o amb nous materials amb propietats excepcionals i compatibilitat CMOS. Les tecnologies híbrides poden superar les limitacions de la tecnologia de silici, donant lloc a nous dispositius capaços de superar el rendiment dels seus homòlegs electrònics. La tecnologia híbrida diòxid de vanadi/silici permet el desenvolupament de dispositius d'alt rendiment, amb gran ample de banda, major velocitat d'operació i major eficiència energètica en l'escala de la longitud d'ona. L'objectiu principal d'esta tesi ha sigut la proposta i desenvolupament de dispositius fotònics d'alt rendiment per a aplicacions de commutació. En este context, diferents estructures basades en silici, tecnologia plasmònica i les propietats sintonitzables del diòxid de vanadi han sigut investigades per a controlar la polarització de la llum i per a desenvolupar altres funcionalitats electró-òptiques com la modulació. / Sánchez Diana, LD. (2016). High performance photonic devices for switching applications in silicon photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/77150 / TESIS

Les travaux de cette thèse portent sur le développement des Circuits Photoniques Intégrés issus de la plateforme d’intégration hétérogène de matériaux III-V sur silicium. Les avantages proposés par cette approche, dans laquelle le gain optique des matériaux III-V se marie aux faibles pertes de propagation des guides d’onde silicium, sont notamment les coûts réduits de fabrication, un haut degré de compacité, et une grande flexibilité dans les fonctionnalités réalisables. Dès lors, notre approche est basée sur l’exploitation de cette technologie pour la réalisation de dispositifs hybrides d’émission laser adressant les objectifs de performance à débits élevés des nouveaux réseaux de télécommunication à fibres optiques. Nous rappelons tout d’abord les transformations récentes amorcées dans les réseaux de télécommunication en vue de répondre à l’accroissement du trafic mondial de données, et présentons alors deux solutions techniques étudiées durant cette thèse. En premier lieu, nous détaillons l’architecture et les éléments de conception d’un émetteur à multiplexage en longueur d’onde (WDM) à 4 longueurs d’onde DFB et 4 Modulateurs à Electro-absorption intégrés dans un circuit photonique hybride III-V sur silicium. Ce circuit est destiné aux transmissions courtes distances (<2km) à 100Gb/s au sein des centres de données (datacenter). Nous avons plus particulièrement étudié l’optimisation de la transition modale entre la section de gain III-V de la cavité laser et le circuit passif de propagation en silicium, que ce soit pour des structures à base de puits ou de boîtes quantiques. L’emploi de ces architectures pour la conception de dispositif à N sources DFB, directement modulées, et à gestion du chirp intégrée, a également été abordé. Nous présentons alors les résultats des caractérisations statiques et dynamiques de ces sources lasers à 1,3µm ainsi que des modulateurs à électro-absorption (MEA) modulés jusqu’à 32Gb /s, et discutons des améliorations structurales que nous avons apportées en vue de renforcer les performances globales du dispositif. La seconde solution approfondie durant cette thèse porte sur les sources lasers accordables intégrant des résonateurs en anneaux, centrées à 1,55µm et directement modulables, en vue d’un déploiement au sein de la nouvelle génération de réseaux optiques passifs d’accès (NG-PON2). Après l’étude de la structure de ces composants, nos travaux sur les problématiques du comportement thermique, ainsi que sur la caractérisation des fonctionnalités d’accord en longueur d’onde et du comportement dynamique de ces cavités hybrides, sont développés. Ainsi, nous rapportons les performances d’un dispositif en boitier de démonstration que ces travaux ont permis de réaliser, pour des transmissions à 10Gbit/s en modulation directe jusqu’à 40km. Enfin, cette thèse s’achève par une conclusion générale et propose un aperçu des possibilités, à court et moyen termes, ouvertes par ces recherches. / The work conducted in this thesis focuses on the development of Photonic Integrated Circuits based on the technological platform of heterogeneous integration of III-V materials on silicon. The benefits brought by this approach, in which the optical gain from III-V materials is coupled with the low propagation losses of silicon waveguide, are in particular a low manufacturing cost, high compacity and scalabity, and a wide range of achievable functionalities. In this way, we aim to exploit this technology to develop hybrid laser devices which meet the performance objectives of high-bit-rate optical fiber transmission networks. From the recent transformations initiated in transmission networks to face the data global traffic increase, two technical solutions have been investigated during this thesis. First, we detail the architecture and the design elements of a WDM emitter with 4 DFB lasers and 4 Electro-Absorption Modulators integrated in a III-V on silicon hybrid Photonic Circuit. This circuit addresses short-distances 100Gb/s transmissions challenges (<2km) in datacenters applications. We specifically studied the optimization of modal transition from the III-V on silicon optical gain section of the laser cavity to the passive silicon circuit, for both quantum wells and quantum dots structure. The use of this architecture for the design of devices including N directly modulated DFB sources with integrated chirp management is also introduced. Static and dynamic characterization results of this laser source emitting at 1,3µm as well as the electro-absorption behavior at modulation rate up to 32Gb/s is reported . The improvement routes of the structure are also discussed to enhance device global performances. The second solution studied in this thesis is a directly modulated tunable laser source, emitting around 1.55µm with integrated ring resonators, for the deployment in the Next-Generation Passive Optical access Networks (NG-PON2). After the description of the structure, thermal problematic, wavelength tunability, and dynamic behavior of these hybrid cavities are presented. Finally, we report the performances of a packaged device for direct modulation transmissions at 10Gb/s over 40km. The thesis ends up with general conclusions, and provides an overview of the short and medium terms possibilities offered by this research.

In this paper, we present the design guidelines for a tunable optical isolator in an SOI-based ring resonator with two small time-modulated regions. By considering a physical model, the proper geometrical and modulation parameters are designed, based on a standard CMOS foundry process. The effect of the variation of the key parameters on the performance of the isolator is explained by two counter-acting mechanisms, namely the separation between the resonance frequencies of counter-rotating modes and energy transfer to the side harmonic. We show that there is a trade-off between these parameters to obtain maximum isolation. Consequently, by applying the quadrature phase difference one can obtain the maximum separation between the resonance frequencies and hence the minimum insertion loss, while the maximum isolation is obtained at the modulation phase difference of −0.78π , which leads to a higher insertion loss. Robustness of the design is investigated through a sensitivity analysis for the fabrication variations in the distance and width of the modulated regions. We demonstrate that there is a trade-off between isolation and insertion loss, and by varying the modulation parameters, we can achieve isolation of 18 (5) dB with 7 (1.8) dB insertion loss.

Les futurs calculateurs de haute performance (HPC) devront faire face à deux défis majeurs : la densité de la bande passante d'interconnexion et les problématiques de consommation d'énergie. La photonique silicium est aujourd’hui perçue comme une solution solide pour aborder ces questions, tant du fait de ses performances que de sa viabilité économique en raison de sa compatibilité directe avec la microélectronique CMOS. Actuellement, une tendance de fond conduit à remplacer les interconnexions métalliques par des liens optiques ; cette évolution a été initiée sur des liaisons grandes distances mais atteint actuellement le niveau des liaisons entre cartes électroniques et pourrait conduire à moyen terme à l’intégration de liens optiques au sein mêmes des circuits intégrés électroniques. La prochaine étape est en effet envisagée pour l'interconnexion des processeurs au sein de puces multi-cœurs en positionnant les liens photoniques sur un même support de silicium (« interposer »). Plusieurs travaux ont démontré la possibilité d'intégrer tous les éléments nécessaires pour la réalisation de liaisons optiques sur un substrat de silicium ouvrant des perspectives de co-intégration optique et électronique très riches.Dans ce contexte, la première contribution de cette thèse est l'optimisation d'un lien de photonique de silicium en terme d'efficacité énergétique par bit (à minimiser). L'optimisation que nous avons conduite a pris en compte une modélisation de la consommation d'énergie pour le laser de la liaison, celle de l’étape dé-sérialisation des données, du résonateur en anneau considéré comme modulateur optique et des circuits de réception (« front-end ») et de décision. Les résultats ont montré que les principales contributions à la consommation de puissance au sein d’un lien optique sont la puissance consommée par le laser et les circuits d’alimentation du modulateur électro-optique. En considérant des paramètres de consommation extraits de simulations numériques et de travaux publiés dans des publications récentes, le débit optimal identifié se trouve dans la plage comprise entre 8 Gbits/seconde et 22 Gbits/seconde selon le nœud technologique CMOS utilisé (65nm à 28nm FD SOI). Il est également apparu qu’une diminution de la consommation de puissance statique du modulateur utilisé pourrait encore ramener ce débit optimal en-dessous de 8 Gbits/seconde.Afin de vérifier ces résultats, un circuit intégré récepteur de liaison optique a été conçu et fabriqué en se basant sur un débit de fonctionnement de 8 Gbits/seconde. Le récepteur utilise une technique d’entrelacement temporel destinée à réduire la vitesse d'horloge nécessaire et à éviter potentiellement l’étape de dé-sérialisation dédiée des informations. / Future high performance computer (HPC) systems will face two major challenges: interconnection bandwidth density and power consumption. Silicon photonic technology has been proposed recently as a cost-effective solution to tackle these issues. Currently, copper interconnections are replaced by optical links at rack and board level in HPCs and data centers. The next step is the interconnection of multi-core processors, which are placed in the same package on silicon interposers, and define the basic building blocks of these computers. Several works have demonstrated the possibility of integrating all elements needed for the realization of short optical links on a silicon substrate.The first contribution of this thesis is the optimization of a silicon photonic link for highest energy efficiency in terms of energy per bit. The optimization provides energy consumption models for the laser, a de- and serialization stage, a ring resonator as modulator and supporting circuitry, a receiver front-end and a decision stage. The optimization shows that the main consumers in optical links is the power consumed by the laser and the modulator's supporting circuitry. Using consumption parameters either gathered by design and simulation or found in recent publications, the optimal bit rate is found in the range between 8 Gbps and 22 Gbps, depending on the used CMOS technology. Nevertheless, if the static power consumption of modulators is reduced it could decrease even below 8 Gbps.To apply the results from the optimization an optical link receiver was designed and fabricated. It is designed to run at a bit rate of 8 Gbps. The receiver uses time interleaving to reduce the needed clock speed and aleviate the need of a dedicated deserialization stage. The front-end was adapted for a wide dynamic input range. In order to take advantage of it, a fast mechanism is proposed to find the optimal threshold voltage to distinguish ones from zeros.Furthermore, optical clock channels are explored. Using silicon photonics a clock can be distributed to several processors with very low skew. This opens the possibility to clock all chips synchronously, relaxing the requirements for buffers that are needed within the communication channels. The thesis contributes to this research direction by presenting two novel optical clock receivers. Clock distribution inside chips is a major power consumer, with small adaptation the clock receivers could also be used inside on-chip clocking trees.

Photonic crystals (PhCs) are structures periodic in thedielectric constant. They exhibit a photonic bandgap, i.e., arange of wavelengths for which light propagation is forbidden.Engineering of defects in the PhC lattice offers new ways toconfine and guide light. PhCs have been manufactured usingsemiconductors and other material technologies. This thesisfocuses on two-dimensional PhCs etched in InP-based materials.Only recently, such structures were identified as promisingcandidates for the realization of novel and advanced functionsfor optical communication applications. The primary focus was on fabrication and characterization ofPhC structures in the InP/GaInAsP/InP material system. Thedemands on fabrication are very high: holes as small as100-300nm in diameter have to be etched at least as deep as 2µm. Thus, different etch processes had to be explored andspecifically developed for InP. We have implemented an etchingprocess based on Ar/Cl2chemically assisted ion beam etching (CAIBE), thatrepresents the state of the art PhC etching in InP. Different building blocks were manufactured using thisprocess. A transmission loss of 10dB/mm for a PhC waveguide, areflection of 96.5% for a 4-row mirror and a record qualityfactor of 310 for a 1D cavity were achieved for this materialsystem. With an etch depth of 4.5 µm, optical loss wasfound to be close to the intrinsic limit. PhC-based opticalfilters were demonstrated using (a) a Fabry-Pérot cavityinserted in a PhC waveguide and (b) a contra-directionalcoupler. Lag effect in CAIBE was utilized positively to realizehigh quality PhC taper sections. Using a PhC taper, a couplingefficiency of 70% was demonstrated from a standard ridgewaveguide to a single line defect PhC waveguide. During the course of this work, InP membrane technology wasdeveloped and a Fabry-Pérot cavity with a quality factorof 3200 was demonstrated. Keywords:photonic crystals, photonic bandgap materials,indium phosphide, dry etching, chemically assisted ion beametching, reactive ion etching, electron beam lithography,photonic integrated circuits, optical waveguides, resonantcavities, optical filtering, finite difference time domain,plane wave expansion.

<p>Photonic crystals (PhCs) are structures periodic in thedielectric constant. They exhibit a photonic bandgap, i.e., arange of wavelengths for which light propagation is forbidden.Engineering of defects in the PhC lattice offers new ways toconfine and guide light. PhCs have been manufactured usingsemiconductors and other material technologies. This thesisfocuses on two-dimensional PhCs etched in InP-based materials.Only recently, such structures were identified as promisingcandidates for the realization of novel and advanced functionsfor optical communication applications.</p><p>The primary focus was on fabrication and characterization ofPhC structures in the InP/GaInAsP/InP material system. Thedemands on fabrication are very high: holes as small as100-300nm in diameter have to be etched at least as deep as 2µm. Thus, different etch processes had to be explored andspecifically developed for InP. We have implemented an etchingprocess based on Ar/Cl₂chemically assisted ion beam etching (CAIBE), thatrepresents the state of the art PhC etching in InP.</p><p>Different building blocks were manufactured using thisprocess. A transmission loss of 10dB/mm for a PhC waveguide, areflection of 96.5% for a 4-row mirror and a record qualityfactor of 310 for a 1D cavity were achieved for this materialsystem. With an etch depth of 4.5 µm, optical loss wasfound to be close to the intrinsic limit. PhC-based opticalfilters were demonstrated using (a) a Fabry-Pérot cavityinserted in a PhC waveguide and (b) a contra-directionalcoupler. Lag effect in CAIBE was utilized positively to realizehigh quality PhC taper sections. Using a PhC taper, a couplingefficiency of 70% was demonstrated from a standard ridgewaveguide to a single line defect PhC waveguide.</p><p>During the course of this work, InP membrane technology wasdeveloped and a Fabry-Pérot cavity with a quality factorof 3200 was demonstrated.</p><p><b>Keywords:</b>photonic crystals, photonic bandgap materials,indium phosphide, dry etching, chemically assisted ion beametching, reactive ion etching, electron beam lithography,photonic integrated circuits, optical waveguides, resonantcavities, optical filtering, finite difference time domain,plane wave expansion.</p>

This thesis presents an introduction to the design and simulation of a novel class of integrated photonic phased array switch elements. The main objective is to use nano-electromechanical (NEMS) based phase shifters of cascaded under-etched slot nanowires that are compact in size and require a small amount of power to operate them. The structure of the switch elements is organized such that it brings the phase shifting elements to the exterior sides of the photonic circuits. The transition slot couplers, used to interconnect the phase shifters, are designed to enable biasing one of the silicon beams of each phase shifter from an electrode located at the side of the phase shifter. The other silicon beam of each phase shifter is biased through the rest of the silicon structure of the switch element, which is taken as a ground. Phased array switch elements ranging from 2×2 up to 8×8 multiple-inputs/multiple-outputs (MIMO) are conveniently designed within reasonable footprints native to the current fabrication technologies. Chapter one presents the general layout of the various designs of the switch elements and demonstrates their novel features. This demonstration will show how waveguide disturbances in the interconnecting network from conventional switch elements can be avoided by adopting an innovative design. Some possible applications for the designed switch elements of different sizes and topologies are indicated throughout the chapter. Chapter two presents the design of the multimode interference (MMI) couplers used in the switch elements as splitters, combiners and waveguide crossovers. Simulation data and design methodologies for the multimode couplers of interest are detailed in this chapter. Chapter three presents the design and analysis of the NEMS-operated phase shifters. Both simulations and numerical analysis are utilized in the design of a 0º-180º capable NEMS-operated phase shifter. Additionally, the response of some of the designed photonic phased array switch elements is demonstrated in this chapter. An executive summary and conclusions sections are also included in the thesis.

This thesis presents an introduction to the design and simulation of a novel class of integrated photonic phased array switch elements. The main objective is to use nano-electromechanical (NEMS) based phase shifters of cascaded under-etched slot nanowires that are compact in size and require a small amount of power to operate them. The structure of the switch elements is organized such that it brings the phase shifting elements to the exterior sides of the photonic circuits. The transition slot couplers, used to interconnect the phase shifters, are designed to enable biasing one of the silicon beams of each phase shifter from an electrode located at the side of the phase shifter. The other silicon beam of each phase shifter is biased through the rest of the silicon structure of the switch element, which is taken as a ground. Phased array switch elements ranging from 2×2 up to 8×8 multiple-inputs/multiple-outputs (MIMO) are conveniently designed within reasonable footprints native to the current fabrication technologies. Chapter one presents the general layout of the various designs of the switch elements and demonstrates their novel features. This demonstration will show how waveguide disturbances in the interconnecting network from conventional switch elements can be avoided by adopting an innovative design. Some possible applications for the designed switch elements of different sizes and topologies are indicated throughout the chapter. Chapter two presents the design of the multimode interference (MMI) couplers used in the switch elements as splitters, combiners and waveguide crossovers. Simulation data and design methodologies for the multimode couplers of interest are detailed in this chapter. Chapter three presents the design and analysis of the NEMS-operated phase shifters. Both simulations and numerical analysis are utilized in the design of a 0º-180º capable NEMS-operated phase shifter. Additionally, the response of some of the designed photonic phased array switch elements is demonstrated in this chapter. An executive summary and conclusions sections are also included in the thesis.

This dissertation documents works on two projects, which are broadly related to photonic integration using III-V semiconductor platform for fiber-based optical communication. Our principal project aims to demonstrate continuous variable quantum key distribution (CV-QKD) with InP-based photonic integrated cir cuit at the 1550 nanometer of optical wavelength. CV QKD protocols, in which the key is encoded in the quadrature variables of light, has generated immense interest over the years because of its compatibility with the existing telecom infrastructure. In this thesis, we have proposed a design of a photonic inte grated circuit potentially capable of realizing this protocol with coherent states of light. From the practical perspective, we have basically designed an optical transmitter and an optical receiver capable of carrying out coherent communi cation via the optical fiber. Initially, we established a mathematical model of the transceiver system based on the optical transfer matrix of the foundry spe cific (Fraunhofer Heinrich Hertz Institute-Germany) building blocks. We have shown that our chip design is versatile in the sense that it can support multiple modulation schemes. Based on the mathematical model, we estimated the link budget to assess the feasibility of on-chip implementation of our protocol. Then we ran a circuit level simulation using the process design kit provided by our foundry to put our analysis on a better footing. The encouraging result from this step prompted us to generate the mask layout for our transceiver chips, which we eventually submitted to the foundry. The other project in the thesis grew out of a collaboration with one of our industry partners. The goal of the project is to enhance the performance of a distributed feedback laser emitting at the 1310 nanometer of optical wavelength by optimizing its design. To that end, we first derived the expression for transmission and reflection spectrum for the laser cavity. Those expressions contained parameters which needed to be obtained from the transverse and the longitudinal mode analysis of the laser. We performed the transverse mode analysis and the longitudinal mode analysis with commercially available numerical solvers. Those mode profiles critically depend on the grating physical parameters. Therefore by tweaking grating dimensions one can control the transmission characteristics of the laser.