In this thesis, miniaturized wavelength interrogators based on planar lightwave circuits (PLCs) are investigated and developed for the optical fiber sensing applications in the aircraft structural health monitoring (SHM) and optofluidic analysis. Two interrogation systems based on an arrayed waveguide grating (AWG) and an Echelle diffractive grating (EDG) are developed and used to convert the optical sensing signals into strain, temperature, vibration, damage, and humidity information for the aircraft SHM. A fiber Bragg grating (FBG) sensing system using developed interrogators is then demonstrated in a field test for aircraft SHM applications. For optofluidic analysis, a PLCs based optofluidic device consisting of two on-chip lens sets is built to enhance the optical manipulation capability of particles. Then, a solution to a multi-functional Lab-on-a-Chip platform for optofluidic analysis is proposed, which integrates the developed particle maneuvering device, grating-structured sensors, and miniaturized interrogators.

Ces trois années de thèse balayent la conception, la fabrication et la caractérisation de lasers III V sur silicium à 1.31 µm pour les data-communications. Le design des sources englobe notamment l’optimisation du couplage entre l’empilement III V et le silicium, effectué grâce à un taper adiabatique, ainsi que l’étude de la cavité laser inscrite, comme le taper, dans le silicium. Trois types de cavités à base de réseaux ont été étudiées: les cavités à contre-réaction distribuée (DFB pour distributed feedback), celles à réseaux de Bragg distribuées (DBR pour distributed Bragg reflector) et enfin celles à réseaux de Bragg échantillonnées (SGDBR pour sampled-grating DBR). Deux solutions ont été abordées concernant les lasers DFB: le réseau, inscrit dans le guide silicium sous la zone de gain, est soit gravé au-dessus du guide Si, soit sur les côtés. La seconde possibilité, appelée ‘DFB lasers couplés latéralement’, simplifie la fabrication et élargit les possibilités de design.Les lasers DFB fabriqués sont très prometteurs en terme de puissance (avec jusque 20 mW dans le guide) ainsi que pour leur pureté spectrale (avec une différence de plus de 50 dB entre le mode principal et le mode suivant). Une accordabilité spectrale de plus de 27 nm a été obtenue en continu avec les lasers SGDBR tout en conservant une très bonne pureté spectrale et une puissance de plus de 7 mW dans le guide. / This 3 years work covers the design, the process and the characterization of III-V on silicon lasers at 1.31 µm for datacommunication applications. In particular, the design part includes the optimization of the coupling between III V and Si using adiabatic tapers as well as the laser cavity, which is formed within the Si. Three types of lasers were studied, all of them based on cavities which consist of gratings: distributed feedback (DFB) lasers, distributed Bragg reflector (DBR) lasers and finally sampled-grating DBR (SGDBR) lasers. Regarding the DFB lasers, two solutions have been chosen: the grating is either etched on top or on the edges of the Si waveguide to form so called vertically or laterally coupled DFB lasers. The latter type, quite uncommon among hybrid III V on Si technologies, simplifies the process fabrication and broadens the designs possibilities.Not only the lasers demonstrated show high output powers (~20 mW in the waveguides) but also very good spectral purities (with a side mode suppression ratio higher than 50 dB), especially for the DFB ones. The SGDBR devices turn out to be continuously tunable over a wavelength range higher than 27 nm with a good spectral purity as well and an output power higher than 7 mW in the waveguide with great opportunities of improvement.

In this thesis, miniaturized wavelength interrogators based on planar lightwave circuits (PLCs) are investigated and developed for the optical fiber sensing applications in the aircraft structural health monitoring (SHM) and optofluidic analysis. Two interrogation systems based on an arrayed waveguide grating (AWG) and an Echelle diffractive grating (EDG) are developed and used to convert the optical sensing signals into strain, temperature, vibration, damage, and humidity information for the aircraft SHM. A fiber Bragg grating (FBG) sensing system using developed interrogators is then demonstrated in a field test for aircraft SHM applications. For optofluidic analysis, a PLCs based optofluidic device consisting of two on-chip lens sets is built to enhance the optical manipulation capability of particles. Then, a solution to a multi-functional Lab-on-a-Chip platform for optofluidic analysis is proposed, which integrates the developed particle maneuvering device, grating-structured sensors, and miniaturized interrogators.

Integration of complex optical functionalities with high performance will lead to a huge development in the field of nanophotonics for a broad range of applications. Silicon photonics is currently the leading technology for the implementation of low-cost photonic integrated devices. The great potential of this technology relies on its compatibility with the mature silicon integrated circuits manufacturing based on complementary metal-oxide semiconductor (CMOS) processes widely used in microelectronic industry and the availability of high quality silicon-on-insulator wafers, an ideal platform for creating planar waveguide circuits that offers strong optical confinement due to the high index contrast between silicon (n=3.45) and silicon dioxide (n=1.45). In order to keep improving the performance of photonic devices on silicon, the integration of CMOS compatible materials with unique properties shows up as an excellent opportunity to overcome the current limitations in silicon while offering unprecedented and novel capabilities to the silicon platform. In this way, barium titantate (BaTiO3) stands out as one of the most disruptive candidates. The work developed in this thesis is essentially focused on the design, fabrication and characterization of an electro-optic modulator based on a hybrid BaTiO3 on silicon structure for the implementation of high performance electro-optic functionalities with beyond state-of-the art performance that currently cannot be afforded in silicon photonics technology. / La integración de funcionalidades ópticas con alto rendimiento llevará a un gran desarrollo en el campo de la nanofotónica para un amplio abanico de aplicaciones. Actualmente, la fotónica de silicio es la tecnología líder para la implementación de dispositivos fotónicos integrados a bajo coste. El gran potencial de esta tecnología reside en su compatibilidad con las maduras técnicas de fabricación de circuitos integrados de silicio basadas en los procesos "complementary metal-oxide semiconductor" (CMOS) ampliamente utilizados en la industria microelectrónica y la disponibilidad de disponer de obleas de silicio sobre aislante de alta calidad, una plataforma ideal para crear circuitos de guía de ondas planas que ofrecen un fuerte confinamiento óptico debido al alto contraste índices entre el silicio (n=3,45) y el dióxido de silicio (n=1,45). Para poder mejorar el rendimiento de dispositivos fotónicos en silicio, la integración de materiales con propiedades excepcionales y compatibles con los procesos de fabricación CMOS surge como una excelente oportunidad para superar las actuales limitaciones de la tecnología de silicio al mismo tiempo que ofrece oportunidades novedosas y sin precedentes en la plataforma de silicio. En este sentido, el material titanato de bario (BaTiO3) se postula como uno de los candidatos más prometedores. El trabajo desarrollado en esta tesis está esencialmente enfocado en el diseño, fabricación y caracterización de un modulador electro-óptico basado en una estructura híbrida de BaTiO3 en silicio para la implementación de funcionalidades electro-ópticas de alto rendimiento más allá del estado del arte de las que no se puede disponer actualmente en la tecnología de fotónica de silicio. / La integració de funcionalitats òptiques amb alt rendiment portarà a un gran desenvolupament en el camp de la nanofotònica per a un ampli ventall d'aplicacions. Actualment, la fotònica de silici és la tecnologia capdavantera per a la implementació de dispositius fotònics integrats a baix cost. El gran potencial d'aquesta tecnologia resideix en la seva compatibilitat amb les madures tècniques de fabricació de circuits integrats de silici basades en els processos "complementary metal-oxide semiconductor" (CMOS) amplament utilitzats en la indústria microelectrònica i la disponibilitat de disposar d'hòsties de silici sobre aïllant d'alta qualitat, una plataforma ideal per crear circuits de guia d'ones planes que ofereixen un fort confinament òptic a causa de l'alt contrast d'índexs entre el silici (n=3,45) i el diòxid de silici (n=1,45). Per poder millorar el rendiment de dispositius fotònics en silici, la integració de materials amb propietats excepcionals i compatibles amb els processos de fabricació CMOS sorgeix com una excel·lent oportunitat per superar les actuals limitacions de la tecnologia de silici al mateix temps que ofereix oportunitats noves i sense precedents en la plataforma de silici. En aquest sentit, el material titanat de bari (BaTiO3) es postula com un dels candidats més prometedors. El treball desenvolupat en aquesta tesi està essencialment enfocat en el disseny, fabricació i caracterització d'un modulador electro-òptic basat en una estructura híbrida de BaTiO3 en silici per a la implementació de funcionalitats electro-òptiques d'alt rendiment més enllà de l'estat de l'art de les quals no es pot disposar actualment a la tecnologia de fotònica de silici. / Castera Molada, P. (2017). Development of new photonic devices based on barium titanate in silicon [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86197 / TESIS

Integrated microwave photonics changes the scaling laws of information and communication systems offering architectural choices that combine photonics with electronics to optimize performance, power, footprint and cost. Application Specific Photonic Integrated Circuits, where particular circuits/chips are designed to optimally perform particular functionalities, require a considerable number of design and fabrication iterations leading to long-development times and costly implementations. A different approach inspired by electronic Field Programmable Gate Arrays is the programmable Microwave Photonic processor, where a common hardware implemented by the combination of microwave, photonic and electronic subsystems, realizes different functionalities through programming. Here, we propose the first-ever generic-purpose Microwave Photonic processor concept and architecture. This versatile processor requires a powerful end-to-end field-based analytical model to optimally configure all their subsystems as well as to evaluate their performance in terms of the radiofrequency gain, noise and dynamic range. Therefore, we develop a generic model for integrated Microwave Photonics systems. The key element of the processor is the reconfigurable optical core. It requires high flexibility and versatility to enable reconfigurable interconnections between subsystems as well as the synthesis of photonic integrated circuits. For this element, we focus on a 2-dimensional photonic waveguide mesh based on the interconnection of tunable couplers. Within the framework of this Thesis, we have proposed two novel interconnection schemes, aiming for a mesh design with a high level of versatility. Focusing on the hexagonal waveguide mesh, we explore the synthesis of a high variety of photonic integrated circuits and particular Microwave Photonics applications that can potentially be performed on a single hardware. In addition, we report the first-ever demonstration of such reconfigurable waveguide mesh in silicon. We demonstrate a world-record number of functionalities on a single photonic integrated circuit enabling over 30 different functionalities from the 100 that could be potentially obtained with a simple seven hexagonal cell structure. The resulting device can be applied to different fields including communications, chemical and biomedical sensing, signal processing, multiprocessor networks as well as quantum information systems. Our work is an important step towards this paradigm and sets the base for a new era of generic-purpose photonic integrated systems. / Los dispositivos integrados de fotónica de microondas ofrecen soluciones optimizadas para los sistemas de información y comunicación. Generalmente, están compuestos por diferentes arquitecturas en las que subsistemas ópticos y electrónicos se integran para optimizar las prestaciones, el consumo, el tamaño y el coste del dispositivo final. Hasta ahora, los circuitos/chips de propósito específico se han diseñado para proporcionar una funcionalidad concreta, requiriendo así un número considerable de iteraciones entre las etapas de diseño, fabricación y medida, que origina tiempos de desarrollo largos y costes demasiado elevados. Una alternativa, inspirada por las FPGA (del inglés Field Programmable Gate Array), es el procesador fotónico programable. Este dispositivo combina la integración de subsistemas de microondas, ópticos y electrónicos para realizar, mediante la programación de los mismos y sus interconexiones, diferentes funcionalidades. En este trabajo, proponemos por primera vez el concepto del procesador de propósito general, así como su arquitectura. Además, con el fin de diseñar, optimizar y evaluar las prestaciones básicas del dispositivo, hemos desarrollado un modelo analítico extremo a extremo basado en las componentes del campo electromagnético. El modelo desarrollado proporciona como resultado la ganancia, el ruido y el rango dinámico global para distintas configuraciones de modulación y detección, en función de los subsistemas y su configuración. El elemento principal del procesador es su núcleo óptico reconfigurable. Éste requiere un alto grado de flexibilidad y versatilidad para reconfigurar las interconexiones entre los distintos subsistemas y para sintetizar los circuitos para el procesado óptico. Para este subsistema, proponemos el diseño de guías de onda reconfigurables para la creación de mallados bidimensionales. En el marco de esta tesis, hemos propuesto dos nuevos nodos de interconexión óptica para mallas reconfigurables, con el objetivo de obtener un mayor grado de versatilidad. Una vez escogida la malla hexagonal para el núcleo del procesador, hemos analizado la configuración de un gran número de circuitos fotónicos integrados y de funcionalidades de fotónica de microondas. El trabajo se ha completado con la demonstración de la primera malla reconfigurable integrada en un chip de silicio, demostrando además la síntesis de 30 de las 100 funcionalidades que potencialmente se pueden obtener con la malla diseñada compuesta de 7 celdas hexagonales. Este hecho supone un record frente a los sistemas de propósito específico. El sistema puede aplicarse en diferentes campos como las comunicaciones, los sensores químicos y biomédicos, el procesado de señales, la gestión y procesamiento de redes y los sistemas de información cuánticos. El conjunto del trabajo realizado representa un paso importante en la evolución de este paradigma, y sienta las bases para una nueva era de dispositivos fotónicos de propósito general. / Els dispositius integrats de Fotònica de Microones oferixen solucions optimitzades per als sistemes d'informació i comunicació. Generalment, estan compostos per diferents arquitectures en què subsistemes òptics i electrònics s'integren per a optimitzar les prestacions, el consum, la grandària i el cost del dispositiu final. Fins ara, els circuits/xips de propòsit específic s'han dissenyat per a proporcionar una funcionalitat concreta, requerint així un nombre considerable d'iteracions entre les etapes de disseny, fabricació i mesura, que origina temps de desenrotllament llargs i costos massa elevats. Una alternativa, inspirada per les FPGA (de l'anglés Field Programmable Gate Array), és el processador fotònic programable. Este dispositiu combina la integració de subsistemes de microones, òptics i electrònics per a realitzar, per mitjà de la programació dels mateixos i les seues interconnexions, diferents funcionalitats. En este treball proposem per primera vegada el concepte del processador de propòsit general, així com la seua arquitectura. A més, a fi de dissenyar, optimitzar i avaluar les prestacions bàsiques del dispositiu, hem desenrotllat un model analític extrem a extrem basat en els components del camp electromagnètic. El model desenrotllat proporciona com resultat el guany, el soroll i el rang dinàmic global per a distintes configuracions de modulació i detecció, en funció dels subsistemes i la seua configuració. L'element principal del processador és el seu nucli òptic reconfigurable. Este requerix un alt grau de flexibilitat i versatilitat per a reconfigurar les interconnexions entre els distints subsistemes i per a sintetitzar els circuits per al processat òptic. Per a este subsistema, proposem el disseny de guies d'onda reconfigurables per a la creació de mallats bidimensionals. En el marc d'esta tesi, hem proposat dos nous nodes d'interconnexió òptica per a malles reconfigurables, amb l'objectiu d'obtindre un major grau de versatilitat. Una vegada triada la malla hexagonal per al nucli del processador, hem analitzat la configuració d'un gran nombre de circuits fotónicos integrats i de funcionalitats de fotónica de microones. El treball s'ha completat amb la demostració de la primera malla reconfigurable integrada en un xip de silici, demostrant a més la síntesi de 30 de les 100 funcionalitats que potencialment es poden obtindre amb la malla dissenyada composta de 7 cèl·lules hexagonals. Este fet suposa un rècord enfront dels sistemes de propòsit específic. El sistema pot aplicarse en diferents camps com les comunicacions, els sensors químics i biomèdics, el processat de senyals, la gestió i processament de xarxes i els sistemes d'informació quàntics. El conjunt del treball realitzat representa un pas important en l'evolució d'este paradigma, i assenta les bases per a una nova era de dispositius fotónicos de propòsit general. / Pérez López, D. (2017). Integrated Microwave Photonic Processors using Waveguide Mesh Cores [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/91232 / TESIS

[EN] Optical technologies are the backbone of modern communication systems providing high-speed access to the Internet, efficient inter and intra-data center interconnects and are expending towards growing research fields and new markets such as satel- lite communications, LIDARs (Laser Imaging Detection and Ranging) applications, Neuromorphic computing, and programable photonic circuits, to name a few. Be- cause of its maturity and low-cost, silicon photonics is being leveraged to allow these new technologies to reach their full potential.As a result, there is a strong need for innovative, high-speed and energy-efficient photonic integrated building blocks on the silicon platform to increase the readiness of silicon photonic integrated circuits. The work developed and presented in this thesis is focused on the design and char- acterization of advanced passive and active devices, for photonic integrated circuits. The thesis consists of three main chapters as well as a motivation and concluding sections exposing the rationale and the accomplishments of this work. Chapter one describes the design and characterization of an electro-optical Mach-Zehnder mod- ulator embedded in highly efficient vertical pn junction exploiting the free-carrier dispersion effect in the O-band.. Chapter two is devoted to the design and charac- terization of a novel geometry of asymmetrical multimode interference device and its implementation in a Mach-Zehnder modulator. Chapter three is dedicated to the design and characterization of innovative 1-dimensional photonic crystal designs for slow- lightmodulation applications. An extensive analysis of the main trade-off arising from the use of slow light is presented. / [ES] Las tecnologías ópticas son el eje vertebrador de los sistemas de comunicación mod- ernos que proporcionan acceso de alta velocidad a la Internet, interconexiones efi- cientes entre centros de datos y dentro de ellos. Además, se están expandiendo hacia campos de investigación crecientes y nuevos mercados como son las aplicaciones de comunicaciones por satélite, los LIDAR (Laser Imaging Detection and Ranging), la computación neuromórfica y los circuitos fotónicos programables, por nombrar algunos. La fotónica de silicio está considerada y aceptada ampliamente como una de las tecnologías clave para que dichas aplicaciones puedan desarrollarse. Como resultado, hay una fuerte necesidad de estructuras fotónicas básicas integradas que sean innovadoras, que soporten altas velocidades de transmisión y que sean más eficientes en términos de consumo de potencia, a fin de aumentar la capacidad de los circuitos integrados fotónicos de silicio. El trabajo desarrollado y presentado en esta tesis se centra en el diseño y la car- acterización de dispositivos avanzados pasivos y activos, para circuitos fotónicos integrados. La tesis consta de tres capítulos principales, así como de sendas sec- ciones de motivación y conclusiones que exponen los fundamentos y los logros de este trabajo. El capítulo uno describe el diseño y la caracterización de un modulador electro-óptico Mach-Zehnder incorporado en una unión pn vertical altamente eficien- ciente que explota el efecto de dispersión de plasma en banda O. El capítulo dos está dedicado al diseño y caracterización de una nueva geometría de dispositivo de interferencia multimodo asimétrico y su aplicación en un modulador Mach-Zehnder. El capítulo tres está dedicado al diseño y caracterización de innovadores cristales fotónicos unidimensionales para aplicaciones de modulación con luz lenta. Se pre- senta un amplio análisis de los principales retos derivados del uso de la misma. / [CA] Les tecnologies òptiques són l'eix vertebrador d'aquells sistemes de comunicació moderns que proporcionen accés d'alta velocitat a la Internet, així com intercon- nexions eficients inter i entre centres de dades. A més a més, s'estan expandint cap a camps d'investigació creixents i nous mercats com són les aplicacions de co- municacions per satèl·lit, els LIDAR (Laser Imaging Detection and Ranging), la computació neuromòrfica i els circuits fotònics programables, entre d'altres. La fotònica de silici és considerada i acceptada àmpliament com una de les tecnologies clau i necessàries perquè aquestes aplicacions puguen desenvolupar-se. Per aquest motiu, es fa necessària l'existència d'estructures fotòniques bàsiques integrades que siguen innovadores, que suporten altes velocitats de transmissió i que siguen més eficients en termes de consum de potència, a fi d'augmentar la capacitat dels cir- cuits integrats fotònics de silici. El treball desenvolupat i presentat en aquesta tesi se centra en el disseny i la caracterització de dispositius avançats passius i actius, per a circuits fotònics integrats. La tesi consta de tres capítols principals, així com d'una secció de motivació i una altra de conclusions que exposen els fonaments i els assoliments d'aquest treball. El capítol u descriu el disseny i la caracterització d'un modulador electro-òptic Mach-Zehnder incorporat en una unió pn vertical d'alta efi- ciència que explota l'efecte de dispersió de plasma en la banda O. El capítol dos està dedicat al disseny i caracterització d'una nova geometria de dispositiu d'interferència multimode asimètric així com a la seua aplicació en un modulador Mach-Zehnder. El capítol tres està dedicat al disseny i caracterització d'innovadors cristalls fotònics unidimensionals per a aplicacions de modulació amb llum lenta. S'inclou també una anàlisi detallada dels principals reptes derivats de l'ús d'aquest tipus de llum. / I want to thank you the Generelitat Valenciana and the European Project L3MATRIX for the funding, without them my doctorate would not taken place. / Zanzi, A. (2020). Passive and active silicon photonics devices at TLC telecommunication wavelengths for on-chip optical interconnects [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149377 / TESIS

No description available.

The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands. Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems. A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W). The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering. Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler. <b>Keywords:</b>silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.

The last two decades have witnessed a large increase in capacity in telecommunication systems, thanks to the development of high bandwidth, fiber optic based networks. Nevertheless the continuing growth of Internet data traffic, fuelled by the development of numerous services like on-line commerce, video on demand, large audio/video files downloads, demands for a significant increase in the ability of the network nodes to manage incoming and outcoming data streams effectively and fast. The different functionalities that are needed include add/drop channel multiplexing, routing, signal reshaping and retiming, electrical/optical and optical/electrical conversion. This has stimulated a large effort towards the investigation of technologies for opto-electronic integration at a wafer level, in order to cope with all the required operations, while limiting overall costs. Among the different approaches proposed, one of the most promising is the “Silicon optical bench”, which relies on the well established VLSI technology for the microelectronics part and on planar lightwave circuits (PLCs) made either with silica-on-silicon waveguide technology (low index contrast) of amorphous silicon technology (high index contrast) on the integrated optics side. This thesis presents the development of new techniques and methodologies utilized in photonic device fabrication, which can be used to facilitate integration of temperature sensitive elements. The process is based on low temperature, plasma assisted, thick film deposition. First, a low temperature (300°C) deposition process based on Plasma assisted Chemical Vapour Deposition (PACVD) for the fabrication of silica based Planar Lightwave Circuits (PLC) is developed. The low thermal budget lends itself to monolithic integration with devices fabricated with different technologies. Absorption bands at around the wavelengths 1.48µm and 1.51µm caused by N-H and Si-H bonds within the material, respectively, had previously been thought to be intrinsic to the PACVD deposition method, when using N2O as oxidant gas of SiH4 and the other dopant precursors. The traditional method to eliminate these absorption bands was high temperature (&gt;1000°C) annealing that seriously hinders device integration. An important achievement in this thesis is the improved suppression of these two absorption bands while keeping the whole fabrication temperature below 300°C and also having a high deposition rate. A complete fabrication process for silica planar lightwave circuits was also developed, by optimising the photolithography and etching step. Finally the effect of dopants like Ge and B on the optical properties of the deposited silica glass was investigated, with particular emphasis to the photosensitive properties of the material upon illumination in the near UV. UV trimming is shown to be a versatile method to selectively control polarization birefringence of devices. Transmission dips of above 50dB were achieved in photo-induced gratings in low temperature deposited B-Ge codoped waveguide cores, without the need for hydrogen loading or other sensitisation techniques. The application of a high refractive index like amorphous silicon is addressed for the realization of efficient Bragg reflectors, either as vertical cavity laser mirrors or as dispersive element for planar waveguides used in highly selective co-directional coupler filters. Applications of amorphous silicon as core material for photonic crystal devices are also shown. The investigations carried out in this thesis show that PACVD technology can provide low-loss and UV sensitive material suitable for realizing a variety of low cost integrated devices for future all optical networks. / QC 20101004

<p>The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands.</p><p>Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems.</p><p>A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W).</p><p>The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering.</p><p>Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler.</p><p><b>Keywords:</b>silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.</p>