[ES] Esta tesis aborda la caracterización de circuitos fotónicos integrados (PIC) usando interferometría óptica en el domino de las frecuencias (OFDI). OFDI tiene una implementación razonablemente simple e interroga al dispositivo bajo test (DUT) proporcionando su respuesta en el dominio del tiempo, en la que los distintos caminos ópticos seguidos por la luz se manifiestan en contribuciones que contienen información de posición, amplitud y fase. Junto con un "setup" OFDI construido en nuestros laboratorios y estructuras de test integradas que involucran anillos resonantes, interferómetros, etc., proponemos e implementamos técnicas para obtener parámetros ópticos cruciales tales como el índice de grupo, dispersión cromática, rotación de polarización y pérdidas de propagación en guías de onda. También para caracterizar acopladores ópticos. Se realizan evaluaciones directas de fase óptica en diferentes experimentos para, entre otras aplicaciones, caracterizar efectos de calor en chips. En la culminación de la tesis, se aborda la integración conjunta de los interferómetros de OFDI junto con el DUT, concibiéndolo como una estructura de caracterización integrada. El uso de guías de onda integradas proporciona una alta estabilidad y adaptación al DUT, además de un mecanismo inherente de compensación de la dispersión. Se realiza un análisis y prueba de concepto experimental caracterizando un "arrayed waveguide grating" en tecnología de nitruro de silicio. Seguidamente, se da un paso adelante proponiendo una arquitectura interferométrica de tres brazos novedosa que permite reducir la complejidad de la medida. Se lleva a cabo una validación experimental amplia usando distintos equipos de laboratorio, acoplamiento horizontal y vertical al chip, y diferentes DUTs en tecnologías de nitruro de silicio y "silicon-on-insulator". / [CAT] Aquesta tesi aborda la caracterització de circuits fotònics integrats (PIC) usant interferometria òptica al domini de les freqüències (OFDI). OFDI té una implementació raonablement simple i interroga el dispositiu sota test (DUT) proporcionant la seva resposta en el domini del temps, en què els diferents camins òptics seguits per la llum es manifesten en contribucions que contenen informació de posició, amplitud i fase. Juntament amb un "setup" OFDI construït als nostres laboratoris i estructures de test integrades que involucren anells ressonants, interferòmetres, etc., proposem i implementem tècniques per obtenir paràmetres òptics crucials com ara l'índex de grup, dispersió cromàtica, rotació de polarització i pèrdues de propagació en guies d'ona. També per caracteritzar acobladors òptics. Es fan avaluacions directes de fase òptica en diferents experiments per, entre altres aplicacions, caracteritzar efectes de calor en xips. A la culminació de la tesi, s'aborda la integració conjunta dels interferòmetres d'OFDI juntament amb el DUT, concebent-ho com una estructura de caracterització integrada. L'ús de guies d'ona integrades proporciona una alta estabilitat i adaptació al DUT, a més d'un mecanisme inherent de compensació de la dispersió. Es realitza una anàlisi i prova de concepte experimental caracteritzant un "arrayed waveguide grating" en tecnologia de nitrur de silici. Seguidament, es fa un pas avant proposant una arquitectura interferomètrica de tres braços nova que permet reduir la complexitat de la mesura. Es du a terme una validació experimental àmplia usant diferents equips de laboratori, acoblament horitzontal i vertical al xip, i diferents DUTs en tecnologies de nitrur de silici i "silicon-on-insulator". / [EN] This PhD thesis covers the characterization of complex photonic integrated circuits (PIC) by using Optical Frequency Domain Interferometry (OFDI). OFDI has a fairly simple implementation and interrogates the device under test (DUT) providing its time domain response, in which the different optical paths followed by light manifest in contributions with position, amplitude and phase information. Together with a working OFDI setup built in our laboratory and integrated test structures involving devices such as ring resonators, interferometers, etc., we propose and implement techniques to get crucial optical parameters such as waveguide group refractive index, chromatic dispersion, polarization rotation, and propagation loss. Also, to characterize optical couplers. Direct optical phase assessment is made in different experiments permitting, amongst others, the characterization of on-chip heat effects. In the culmination of the thesis, the co-integration of the OFDI interferometers with the DUT is addressed, conceiving it as an integrated characterization structure. The use of integrated waveguides provide high stability and adaptation to the DUT, as well as an inherent dispersion de-embedding mechanism. It is provided analysis and experimental proof of concept with an arrayed waveguide grating as DUT in a silicon nitride platform. A considerable leap forward is then taken by proposing a novel three-way interferometer architecture, reducing the measurement complexity. Wide experimental validation is carried out using different laboratory equipment, horizontal and vertical chip coupling, and different DUTs in silicon nitride and silicon-on-insulator. / Bru Orgiles, LA. (2022). Optical Frequency Domain Interferometry for the Characterization and Development of Complex and Tunable Photonic Integrated Circuits [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181635

Optical communications systems operate at the limits of their margins to respond to increasing capacity demands. Some of the signal processing functions required must soon operate at speeds beyond electronic implementation. Optical signal processors are fundamentally analog which requires precise control of the operating state. Programmable optical components are consequently essential. The thesis explores and elucidates the properties of meshes of generalized Mach-Zehnder interferometers (GMZIs) amenable to silicon (Si) photonics integration that are based on multimode interference couplers with programmability achieved via voltage controlled phase-shift elements within the interferometer arms to perform a variety of finite impulse response (FIR) and infinite impulse response (IIR) signal processing functions. The thesis presents a novel class of integrated photonic phased array systems with a single-stage, multistage, and feedback architectures. The designed photonic integrated systems utilize nano-electromechanical-system (NEMS) operated phase shifters of cascaded free suspended slot waveguides that are compact and require a small amount of power to operate. The structure of the integrated photonic phased array switch (IPPAS) elements is organized such that it brings the NEMS-operated phase shifters to the exterior sides of the construction; facilitating electrical connection. The transition slot couplers used to interconnect the phase shifters to the rest of the silicon structure 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 fabric, which is taken as a ground. Phased array processors of 2×2 and 4×4 multiple-input-multiple-output (MIMO) ports are conveniently designed within reasonable footprints native to the current fabrication technologies. The response of the single-stage 4×4 broadband IPPAS element is determined, and its phase synthesis states required for single-throw, double-throw and broadcast routing operations are predicted. The transmission responses of the single-stage wavelength division multiplexing (WDM) processors of 2×2 and 4×4 MIMO ports are simulated. The wavelength steering capability of the transmission interferograms by applying progressive phase shifts through the array of NEMS-operated phase shift elements of the single-stage 4×4 WDM (de)multiplexer is demonstrated. The advantages of cascading broadband and WDM phased array sections are articulated through several study cases. Five different cascaded phased array architectures are trialed for the construction of non-blocking 4×4 IPPAS broadband switches that are essential elements in the construction of universal photonic processors. A cascaded 2×2 WDM (de)multiplexer that can set the bandwidth of the (de)multiplexed cyclic channels into a binary number of programmable values is demonstrated. The envelope and wavelength modulations of the transmission responses utilizing a cascaded forward structure of three 2×2 sections that can be utilized for the (de)multiplexing of different bandwidth channels are demonstrated providing individual wavelength steering capability of the narrowband and wideband channels and the individual wavelength steering capability of the slow envelope and wavelength modulating functions. Innovative universal 2×2 and 4×4 cascaded phased array processors of advanced high-order architectures that can function as both non-blocking broadband routers and tunable WDM (de)multiplexers with spectrum steering and bandwidth control of the (de)multiplexed demands are introduced. The multimode interference (MMI) coupler is utilized for the construction of several IIR feedback photonic processors. Tunable photonic feedback processors have the advantage of using less number of MMI couplers compared to their counterparts of FIR forward-path processors saving on the footprint and loss merits. A passive feedback 2×2 (de)multiplexer made of a 4×4 MMI coupler and two loopback paths is proposed. The inclusion of an imbalance in the lengths of the loopback paths of the same symmetrical feedback (de)multiplexer is demonstrated to achieve wavelength modulation of the (de)multiplexed transmission responses that are useful for the (de)multiplexing of different bandwidth channels. Several newly introduced IIR feedback architectures are demonstrated to function similarly as their counterparts of FIR forward-path processors as binary bandwidth variable (de)multiplexers, envelope and wavelength modulation (de)multiplexers, and universal feedback processors. The investigation provided in this thesis is also supported with dynamic zero-pole evolution analysis in the complex plane of analysis of the studied FIR and IIR photonic processors to enhance understanding the principle of operation. This research expands the prospective for constructing innovative silicon-on-insulator (SOI) based optical processors for applications in modern optical communication systems and programmable elastic optical networks (EONs).

Ce travail de thèse présente une étude sur les propriétés de nanostructures de type bâtonnets quantiques et de leur application pour les télécommunications optiques. Durant la dernière décennie, ces nanostructures, ont démontré des propriétés optiques et électroniques intéressantes en raison notamment d’un fort confinement quantique dans les trois dimensions d'espace. Cette thèse porte sur la conception et la fabrication d'émetteurs optiques intégrés à base de ce matériau et de leur implémentation dans des systèmes de communication. La première partie de ce travail analyse les propriétés de ces nanostructures, théorique et expérimentale. Elles sont utilisées comme matériau actif de lasers modulés directement en amplitude. Les propriétés dynamiques de ces lasers sont ensuite évaluées et des transmissions sur fibre optique entre 0 et 100 km sont ensuite démontrées en utilisant un filtre étalon permettant d’augmenter en particulier le taux d’extinction dynamique. En s’appuyant sur cette démonstration basée sur des éléments discrets, une version monolithique intégrant un laser et un résonateur en anneaux a été réalisée. La dernière partie de ce travail porte sur des lasers à blocage de mode à base de ce matériau et en particulier sur les méthodes d’intégration sur substrat InP. En particulier, un design de miroir de Bragg innovant a été développé à cet effet et une démonstration d'un laser a blocage de mode intégré avec un amplificateur optique à semi-conducteur a finalement été réalisée / This PhD dissertation presents a study on the properties of the novel quantum dash nanostructures and their properties for application in optical telecommunications. Over the last decade, scientific community has gained considerable interest over these nanostructures and several demonstrations have been made on their interesting optical and electronic properties, notably owing to their strong quantum confinement. This dissertation focuses on conception, fabrication and system demonstration of integrated optical transmitters based on quantum dash material. A first part of this work analyses the properties of qdashes theoretically and experimentally for their use as an active material in directly modulated lasers. The dynamic properties of this material are then evaluated leading to an optical transmission distances in range of 0-100km under direct modulation. The transmission is particularly studied with a passive optical filter to enhance the dynamic extinction ratio, the use of such passive filters is studied in detail. An innovative and fully integrated optical transmitter is finally demonstrated by integrating a ring-resonator filter to a distributed feedback laser. The second part of this work focuses on mode locked lasers based on this material and in particular the methods of integration of such devices on InP are explored. Thus an innovative Bragg mirror design is developed leading to a mode locked laser integrated with a semiconductor optical amplifier

Integrated quantum photonics show monolithic waveguide chips to be a promising platform for realizing the next generation of quantum optical circuits. This work proposes the implementation of quantum page Rank algorithm on a photonic waveguide lattice. Our contributions are as follows: Continuous-time quantum stochastic walk(QSW)-an alternate paradigm of quantum computing, is a hybrid quantum walk that incorporates both unitary and non-unitary effects. We propose the use of QSW which necessitates the hopping of the quantum crawler on a directed graph, for the quantum page Rank problem. We propose the implementation of quantum page Rank on a photonic waveguide lattice, where we allow the density matrix to evolve according to the Lindblad-Kossakowski master equation, the diagonal of which gives the quantum page Rank. We have also shown the use of the metric of positional Kolmogorov Complexity as an efficient tool for determining whether or not the quantum channel has been compromised. We appositionally encode multi-photon decoy pulses within the stream of single photon pulses. This positional encoding is chosen in such a way as to have low Kolmogorov complexity. The PNS attack on the multi-photon decoy pulses causes a dip in the ratio of the transmittance of the decoy pulses to the signal pulses in the conventional analysis.

Chalcogenide glasses are highly nonlinear optical materials which can be used for fabricating active and passive photonic devices. This thesis work deals with the fabrication of buried, three dimensional, channel waveguides in chalcogenide glasses, using ultrafast laser inscription technique. The femtosecond laser pulses are focused into rare earth ions doped and undoped chalcogenide glasses, few hundred microns below from the surface to modify the physical properties such as refractive index, density, etc. These changes are made use in the fabrication of active and passive photonic waveguides which have applications in integrated optics. The first chapter provides an introduction to the fundamental aspects of femtosecond laser inscription, laser interaction with matter and chalcogenide glasses for photonic applications. The advantages and applications of chalcogenide glasses are also described. Motivation and overview of the present thesis work have been discussed at the end. The methods of chalcogenide glass preparation, waveguide fabrication and characterization of the glasses investigated are described in the second chapter. Also, the details of the experiments undertaken, namely, loss (passive insertion loss) and gain measurements (active) and nanoindentation studies are outlined. Chapter three presents a study on the effect of net fluence on waveguide formation. A heat diffusion model has been used to solve the waveguide cross-section. The waveguide formation in GeGaS chalcogenide glasses using the ultrafast laser, has been analyzed in the light of a finite element thermal diffusion model. The relation between the net fluence and waveguide cross section diameter has been verified using the experimentally measured properties and theoretically predicted values. Chapter four presents a study on waveguide fabrication on Er doped Chalcogenide glass. The active and passive characterization is done and the optimal waveguide fabrication parameters are given, along with gain properties for Er doped GeGaS glass. A C-band waveguide amplifier has been demonstrated on Chalcogenide glasses using ultrafast laser inscription technique. A study on the mechanical properties of the waveguide, undertaken using the nanoindentation technique, is presented in the fifth chapter. This work brings out the close relation between the change in mechanical properties such as elastic modulus and hardness of the material under the irradiation of ultrafast laser after the waveguide formation. Also, a threshold value of the modulus and hardness for characterizing the modes of the waveguide is suggested. Finally, the chapter six provides a summary of work undertaken and also discusses the future work to be carried out.

The widespread adoption of photonic circuits requires the economics of volume manufacturing offered by integration technology. A Complementary Metal-Oxide Semiconductor compatible silicon material platform is particularly attractive because it leverages the huge investment that has been made in silicon electronics and its high index contrast enables tight confinement of light which decreases component footprint and energy consumption. Nevertheless, there remain challenges to the development of photonic integrated circuits. Although the density of integration is advancing steady and the integration of the principal components – waveguides, optical sources and amplifiers, modulators, and photodetectors – have all been demonstrated, the integration density is low and the device library far from complete. The integration density is low primarily because of the difficulty of confining light in structures small compared to the wavelength which measured in micrometers. The device library is incomplete because of the immaturity of hybridisation on silicon of other materials required by active devices such as III-V semiconductor alloys and ferroelectric oxides and the difficulty of controlling the coupling of light between disparate material platforms. Metamaterials are nanocomposite materials which have optical properties not readily found in Nature that are defined as much by their geometry as their constituent materials. This offers the prospect of the engineering of materials to achieve integrated components with enhanced functionality. Metamaterials are a class of photonic crystals includes subwavelength grating waveguides, which have already provided breakthroughs in component performance yet require a simpler fabrication process compatible with current minimum feature size limitations. The research reported in this PhD thesis advances our understanding of the structure-property relations of key planar light circuit components and the metamaterial engineering of these properties. The analysis and simulation of components featuring structures that are only just subwavelength is complicated and consumes large computer resources especially when a three dimensional analysis of components structured over a scale larger than the wavelength is desired. This obstructs the iterative design-simulate cycle. An abstraction is required that summarises the properties of the metamaterial pertinent to the larger scale while neglecting the microscopic detail. That abstraction is known as homogenisation. It is possible to extend homogenisation from the long-wavelength limit up to the Bragg resonance (band edge). It is found that a metamaterial waveguide is accurately modeled as a continuous medium waveguide provided proper account is taken of the emergent properties of the homogenised metamaterial. A homogenised subwavelength grating waveguide structure behaves as a strongly anisotropic and spatially dispersive material with a c-axis normal to the layers of a one dimensional multi-layer structure (Kronig-Penney) or along the axis of uniformity for a two dimensional photonic crystal in three dimensional structure. Issues with boundary effects in the near Bragg resonance subwavelength are avoided either by ensuring the averaging is over an extensive path parallel to boundary or the sharp boundary is removed by graded structures. A procedure is described that enables the local homogenised index of a graded structure to be determined. These finding are confirmed by simulations and experiments on test circuits composed of Mach-Zehnder interferometers and individual components composed of regular nanostructured waveguide segments with different lengths and widths; and graded adiabatic waveguide tapers. The test chip included Lüneburg micro-lenses, which have application to Fourier optics on a chip. The measured loss of each lens is 0.72 dB. Photonic integrated circuits featuring a network of waveguides, modulators and couplers are important to applications in RF photonics, optical communications and quantum optics. Modal phase error is one of the significant limitations to the scaling of multimode interference coupler port dimension. Multimode interference couplers rely on the Talbot effect and offer the best in-class performance. Anisotropy helps reduce the Talbot length but temporal and spatial dispersion is necessary to control the modal phase error and wavelength dependence of the Talbot length. The Talbot effect in a Kronig-Penny metamaterial is analysed. It is shown that the metamaterial may be engineered to provide a close approximation to the parabolic dispersion relation required by the Talbot effect for perfect imaging. These findings are then applied to the multimode region and access waveguide tapers of a multi-slotted waveguide multimode interference coupler with slots either in the transverse direction or longitudinal direction. A novel polarisation beam splitter exploiting the anisotropy provided by a longitudinally slotted structure is demonstrated by simulation. The thesis describes the design, verification by simulation and layout of a photonic integrated circuit containing metamaterial waveguide test structures. The test and measurement of the fabricated chip and the analysis of the data is described in detail. The experimental results show good agreement with the theory, with the expected errors due to fabrication process limitations. From the Scanning Electron Microscope images and the measurements, it is clear that at the boundary of the minimum feature size limit, the error increases but still the devices can function.

Le contexte de cette thèse couvre les dispositifs photoniques hybrides III-V sur silicium. L’étude porte sur l’intégration par collage de matériau à base d'InP sur le silicium, puis la conception d’un guide optique comportant une nanostructuration qui permettra la sélection en longueur d’onde dans un laser DFB hybride. Enfin, on étudie les étapes technologiques de fabrication d’un laser hybride injecté électriquement fonctionnant dans le domaine spectral 1.55µm, et on caractérise les dispositifs. Pour associer les matériaux III-V sur Si, nous avons développé le collage sans couche intermédiaire que l’on nomme collage hétéroépitaxial ou oxide-free. Ce collage est reporté dans la littérature comme présentant une meilleure qualité électrique. Nous avons établi les conditions de préparation permettant d’obtenir des surfaces parfaitement désoxydées, et les conditions de recuit conduisant à une interface hybride sans oxyde et sans dislocation. Mais ce recuit est réalisé à température assez élevée (~450-500°C). Nous avons alors développé le collage avec une fine couche intermédiaire d’oxyde réalisé à plus faible température -300°C- qui présente l'avantage d'être compatible avec la technologie CMOS. Nous avons étudié différentes approches pour élaborer et activer une couche d’oxyde très fine (~3nm), de façon à obtenir une surface collée sans zones localement non collées. Le collage est dans les deux cas réalisé sous vide dans un équipement de type Bonder Suss SB6e. La qualité structurale de l’interface a été observée par STEM et la qualité mécanique du joint de collage a été caractérisée par indentation. Une méthode originale de mesure quantitative et locale de l’énergie du joint de collage a été développée. La qualité optique des couches collées a été étudiée par la mesure de la photoluminescence de puits quantiques placés proches du joint d’interface. En conséquence du collage sans couche intermédiaire ou avec une couche très fine, le design du mode optique est de type double-cœur, qui ne nécessite pas de taper. Le guide optique Si est de type shallow ridge, le confinement latéral étant assuré par un matériau nanostructuré à une période sub-longueur d’onde. Ce matériau fonctionne comme un matériau effectif uniaxe pour lequel on a calculé les indices optiques ordinaire et extraordinaire selon la géométrie de la nanostructuration. On peut rajouter sur cette nanostructuration une super-périodicité qui conduit à un fonctionnement sélectif en longueur d’onde. Le comportement modal du guide est simulé à l'aide du logiciel COMSOL Multiphysics, le comportement spectral est simulé par FTDT 3D. Nous avons validé la pertinence de ce design en mesurant la transmission de guides hybrides. Ce design sera inclus dans un laser et permettra d’obtenir une émission monofréquence de type DFB. Nous avons développé les étapes technologiques nécessaires à la fabrication d’un laser hybride à base d'InP sur Silicium fonctionnant en injection électrique. Nous avons mis en oeuvre de nombreuses techniques, et développé plusieurs procédés spécifiques, en particulier, des procédés de gravure sèche de type Inductive Coupled Plasma Reactive Ion Etching ICP-RIE pour la gravure de la nanostructuration dans le silicium, et pour la gravure du mésa du laser. La présence des 2 matériaux III-V et Si dans le dispositif hybride rend ces étapes complexes. Les premiers résultats peuvent être améliorés en optimisant la technologie des contacts. Un design permettant de s’affranchir de la pénalité thermique présenté par tous les dispositifs ayant les 2 contacts électriques du coté du matériau III-V a été proposé, exploitant le passage du courant à l’interface hybride III-V / Si, ce qui est possible dans le cas du collage oxide-free. Cette approche ouvre des perspectives d’intégration au-delà de la photonique. / This work contributes to the general context of III-V materials on Silicon hybrid devices for optical integrated functions, mainly emission/amplification at 1.55µm. Devices are considered for operation under electrical injection, reaching performances relevant for data transfer application. The main three contributions of this work concern: (i) bonding InP-based materials on Si, (ii) nanostructuration of the Si guiding layer for spatial and spectral control of the guided mode and (iii) technology of an hybrid electrically injected laser, with a special attention to the thermal budget. Bonding has been investigated following two approaches. The first one we call heterohepitaxial or oxide-free bonding, is performed without any intermediate layer at a temperature ~450°C. This approach has the great advantage allowing electrical transport across the interface, as reported in the literature. We have developed oxide-free surface preparation for both materials, mainly InP-based layers, and established bonding parameter processing. An in-depth STEM and RX structural characterization has demonstrated an oxide-free reconstructed interface without any dislocation except on one or two atomic layers which accommodate the large lattice mismatch (8.1%) between InP and Si. Photoluminescence of quantum wells intentionally grown close to the interface has shown no degradation. We have also developed an oxide-based bonding process operated at 300°C in order to be compatible with CMOS processing. The original ozone activation of the very thin (~5nm) oxide layer we have proposed demonstrates a bonding surface without any unbonded area due to degassing under annealing. We have developed an original method based on nanoindentation characterization in order to obtain a quantitative and local value of the surface bonding energy. Related to the absence or to the very thin intermediate layer between the two materials, our modal design is based on a double core structure, where most of the optical mode is confined in the Si guiding layer, and no taper is required. The Si waveguide on top of the SOI stack is a shallow ridge. A nanostructured material on both sides of the waveguide core ensures the lateral confinement, the nanostructuration geometry being at a sub-wavelength period in order to operate this material well below its photonic gap. It behaves as an uniaxial material with ordinary and extraordinary indices calculated according to the structuration geometry. Such a structuration allows modal and spectral control of the guided mode. 3D modal and spectral simulation have been performed. We have demonstrated, on a double-period structuration, a wavelength selective operation of hybrid optical waveguides. Such a double-period geometry could be included in a laser design for DFB operation. This nanostructuration has larger potential application such as coupled waveguides arrays or selective resonators. We have developed all the technological processing steps for an electrically injected hybrid laser fabrication. Main developments concern dry etching, performed with the Inductive Coupled Plasma Reactive Ion Etching ICP-RIE technique of both the nanostructuration of the Silicon material, and the mesa of the hybrid laser. Efficient electrical contacts fabrication is also a complex step. First lasers operating performances could be improved. We have investigated a specific design in order to overcome the thermal penalty encountered by all the hybrid devices. This penalty is due to the thick buried oxide layer of the SOI stack that prevents heating related to the current flow to be dissipated. Taking advantage of the electrical transport we have shown at the oxide-free interface, we propose a design where the n-contact is defined on the guiding Si layer, suppressing thermal heating under electrical operation. Such an approach is very promising for densely packed hybrid devices integrated with associated electronic driving elements on Si.

[ES] La tomografía por difracción surge para mejorar las técnicas de imagen al considerar la naturaleza ondulatoria de la luz. Mientras que los primeros sistemas de imagen médica se basaban únicamente en fuentes sin difracción, este enfoque consigue mejorar la reconstrucción del índice de refracción de los objetos, lo que permite, por ejemplo, el estudio de estructuras subcelulares. Del mismo modo, la demanda de redes de telecomunicaciones cada vez más rápidas y seguras ha propiciado la aparición de la fotónica. Hace dos décadas, la combinación de estos dos campos dio lugar a los primeros sistemas de tomografía por difracción óptica (ODT), los cuáles han evolucionado rápidamente durante este siglo. En esta tesis, presentamos dos nuevas aplicaciones de la ODT. La primera está relacionada con el concepto del microscopio tomográfico de fase (TPM), una versión de la ODT que permite el estudio de células aisladas, con muchas aplicaciones biomédicas, como el diagnóstico y la prognosis del cáncer. Sin embargo, los sistemas TPM actuales son caros, pesados y complejos. Para resolver estos problemas, proponemos el concepto de TPM en chip. Con este fin, diseñamos una hoja de ruta hacia el primer dispositivo tomográfico integrado en el marco de la tecnología lab-on-a-chip (LoC), y desarrollamos los primeros pasos para ello: 1) Hasta ahora, sólo se han utilizado detectores planos para obtener los mapas de índice de refracción de los objetos estudiados en TPM, basados en la detección del campo difractado hacia delante. Sin embargo, los principios físicos fundamentales indican que medir también el campo difractado hacia detrás debería mejorar la resolución de las imágenes. Además, un detector plano no es la configuración óptima para el TPM en chip. En esta línea, hemos explorado la posibilidad de usar detectores circulares en este escenario, como una técnica más adecuada para las configuraciones en chip, demostrando al mismo tiempo que este enfoque proporciona una mejor resolución que el lineal. 2) Proponemos un esquema de TPM en chip basado en el uso de nanoantenas dieléctricas como fuente de luz y píxeles detectores ODT, y caracterizamos experimentalmente su comportamiento mediante microscopía óptica de campo cercano. En cuanto a la segunda aplicación, estudiamos el potencial de la ODT como nuevo paradigma en la detección de capas de invisibilidad realistas, una de las aplicaciones más importantes de los metamateriales. Hasta ahora, el scattering cross section (SCS) se ha utilizado como modelo de referencia para diseñar y observar la eficacia de estos dispositivos para ocultar objetos. En nuestro estudio, demostramos que la ODT puede detectar las capas de invisibilidad prácticas con una sensibilidad superior a la que ofrece el SCS, incluso a las frecuencias de trabajo óptimas. Además, es posible obtener una imagen representativa del tamaño y la forma de la capa, revelando claramente su existencia. Finalmente, se discuten las conclusiones extraídas de los resultados obtenidos. Además, se detallan las futuras líneas de trabajo para abordar los retos que no se han completado en esta tesis doctoral. / [CA] La tomografia per difracció sorgeix per millorar les tècniques d'imatge anteriors en considerar la naturalesa ondulatòria de la llum. Mentre que els primers sistemes d'imatge mèdica es basaven únicament en fonts sense difracció, aquest enfocament aconsegueix millorar la reconstrucció de l'índex de refracció dels objectes, la qual cosa permet, per exemple, l'estudi d'estructures subcelulars. De la mateixa manera, la demanda de xarxes de telecomunicacions cada vegada més ràpides i segures ha propiciat l'aparició de la fotònica. Fa dues dècades, la combinació d'aquests dos camps va portar als primers sistemes de tomografia per difracció òptica (ODT), els quals han evolucionat ràpidament durant aquest segle. En aquesta tesi, presentem dues noves aplicacions de la ODT. La primera està relacionada amb el concepte del microscopi tomogràfic de fase (TPM), una versió de la ODT que permet l'estudi de cèl·lules aïllades, amb moltes aplicacions en biomedicina, com el diagnòstic i prognosi del càncer. No obstant això, els sistemes TPM actuals són cars, pesats i complexos. Per resoldre aquests problemes, proposem el concepte de TPM en xip. Per fer-ho, dissenyem un full de ruta cap al primer dispositiu tomogràfic integrat en el marc de la tecnologia lab-on-a-chip (LoC), i desenvolupem els primers passos a aquest efecte: 1) Fins ara, només s'han utilitzat detectors plans per a obtindre els mapes d'índex de refracció dels objectes estudiats en TPM, basats en la detecció del camp difractat cap avant. No obstant això, els principis físics fonamentals indiquen que mesurar també el camp difractat cap endarrere hauria de millorar la resolució de les imatges. A més, un detector pla no és la configuració òptima per al TPM en xip. En aquesta línia, hem explorat la possibilitat d'usar detectors circulars en aquest escenari, com una tècnica més adequada per a les configuracions en xip, demostrant al mateix temps que aquest enfocament proporciona una millor resolució que el lineal. 2) Proposem un esquema de TPM en xip basat en l'ús de nanoantenes dielèctriques com a font de llum i píxels detectors ODT, i caracteritzem experimentalment el seu comportament en camp pròxim mitjançant microscòpia òptica de camp pròxim. Pel que fa a la segona aplicació, estudiem el potencial de la ODT com a nou paradigma en la detecció de capes d'invisibilitat realistes, una de les aplicacions més importants dels metamaterials. Fins ara, el scattering cross section (SCS) s'ha utilitzat com a model de referència per a dissenyar i observar l'eficàcia d'aquests dispositius per a ocultar objectes. En el nostre estudi, vam demostrar que la ODT pot detectar les capes d'invisibilitat pràctiques amb una sensibilitat superior a la que ofereix el SCS, fins i tot a les freqüències de treball òptimes. A més, és possible obtindre una imatge representativa de la grandària i la forma de la capa, revelant clarament la seua existència. Finalment, es discuteixen les conclusions extretes dels resultats obtinguts i es detallen les futures línies de treball per a abordar els reptes que no s'han completat en aquesta tesi doctoral. / [EN] Diffraction Tomography arises to improve previous imaging techniques by considering the wave nature of light. Whereas the first medical imaging systems relied only on non-diffracting sources, this approach results in an enhanced reconstruction of the object's refractive index distribution, allowing, for example, the study of subcellular structures. Likewise, the demand for increasingly faster and secure telecommunication networks led to the advent of photonics. Two decades ago, the combination of these two fields gave rise to the first optical diffraction tomography (ODT) systems, which have rapidly evolved during this century. In this thesis, we present two novel applications of ODT. The first one is related to the concept of tomographic phase microscopy (TPM), a version of ODT that enables the study of isolated cells, with many applications in biomedicine, such as the diagnosis and prognosis of cancer. Nevertheless, current TPM systems are expensive, heavy, and cumbersome. To solve these issues we propose the concept of on-chip TPM. For this purpose, we design a roadmap towards the first integrated tomographic device in the frame of lab-on-a-chip (LoC) technology and develop the first steps to this end: 1) Until now, only flat detectors have been used to obtain the refractive index maps of the objects studied in TPM, based on the detection of the forward scattering. However, fundamental physical principles indicate that measuring also the backscattered field should improve the resolution of the images. Moreover, a flat detector is not the optimal configuration for on-chip TPM. In this vein, we have explored the possibility of using circular detectors in this scenario as a more suitable technique for on-chip configurations, demonstrating at the same time that this approach provides a better resolution than the linear one. 2) We propose a TPM on-chip scheme based on the use of dielectric nanoantennas as the ODT light source and detector pixels, and experimentally characterize their near-field behavior via scanning near-field optical microscopy. As for the second application, we study the potential of ODT as a new paradigm in the detection of realistic invisibility cloaks, one of the most important applications of metamaterials. Up to now, the scattering cross section (SCS) has been used as the gold standard to design and observe the effectiveness of these devices in hiding objects. In our study, we show that ODT can detect practical invisibility cloaks with a higher sensitivity than that offered by the SCS, even at the optimal working frequencies. Moreover, it is possible to obtain an image depicting the size and shape of the cloak, clearly revealing their existence. Finally, the conclusions drawn from the obtained results are discussed. In addition, future lines of action to address the challenges that have not been completed in this doctoral thesis are detailed. / Díaz Fernández, FJ. (2021). Novel Applications of Optical Diffraction Tomography: On-chip Microscopy and Detection of Invisibility Cloaks [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180125

[EN] The processing of radiofrequency signals using photonics means is a discipline that appeared almost at the same time as the laser and the optical fibre. Photonics offers the capability of managing broadband radiofrequency (RF) signals thanks to its low transmission attenuation, a variety of linear and non-linear phenomena and, recently, the potential to implement integrated photonic subsystems. These features open the door for the implementation of multiple functionalities including optical transportation, up and down frequency conversion, optical RF filtering, signal multiplexing, de-multiplexing, routing and switching, optical sampling, tone generation, delay control, beamforming and photonic generation of digital modulations, and even a combination of several of these functionalities. This thesis is focused on the application of vector processing in the optical domain to radiofrequency signals in two fields of application: optical beamforming, and photonic vector modulation and demodulation of digital quadrature amplitude modulations. The photonic vector control enables to adjust the amplitude and phase of the radiofrequency signals in the optical domain, which is the fundamental processing that is required in different applications such as beamforming networks for direct radiating array (DRA) antennas and multilevel quadrature modulation. The work described in this thesis include different techniques for implementing a photonic version of beamforming networks for direct radiating arrays (DRA) known as optical beamforming networks (OBFN), with the objectives of providing a precise control in terrestrial applications of broadband signals at very high frequencies above 40 GHz in communication antennas, optimizing the size and mass when compared with the electrical counterparts in space application, and presenting new photonic-based OBFN functionalities. Thus, two families of OBFNs are studied: fibre-based true time delay architectures and integrated networks. The first allow the control of broadband signals using dispersive optical fibres with wavelength division multiplexing techniques and advanced functionalities such as direction of arrival estimation in receiving architectures. In the second, passive OBFNs based on monolithically-integrated Optical Butler Matrices are studied, including an ultra-compact solution using optical heterodyne techniques in silicon-on-insulator (SOI) material, and an alternative implementing a homodyne counterpart in germanium doped silica material. In this thesis, the application of photonic vector processing to the generation of quadrature digital modulations has also been investigated. Multilevel modulations are based on encoding digital information in discrete states of phase and amplitude of an electrical signal to enhance spectral efficiency, as for instance, in quadrature modulation. The signal process required for generating and demodulating this kind of signals involves vector processing (phase and amplitude control) and frequency conversion. Unlike the common electronic or digital implementation, in this thesis, different photonic based signal processing techniques are studied to produce digital modulation (photonic vector modulation, PVM) and demodulation (PVdM). These techniques are of particular interest in the case of broadband signals where the data rate required to be managed is in the order of gigabit per second, for applications like wireless backhauling of metro optical networks (known as fibre-to-the-air). The techniques described use optical dispersion in optical fibres, wavelength division multiplexing and photonic up/down conversion. Additionally, an optical heterodyne solution implemented monolithically in a photonic integrated circuit (PIC) is also described. / [ES] El procesamiento de señales de radiofrecuencia (RF) utilizando medios fotónicos es una disciplina que apareció casi al mismo tiempo que el láser y la fibra óptica. La fotónica ofrece la capacidad de manipular señales de radiofrecuencia de banda ancha, una baja atenuación, procesados basados en una amplia variedad de fenómenos lineales y no lineales y, recientemente, el potencial para implementar subsistemas fotónicos integrados. Estas características ofrecen un gran potencial para la implementación de múltiples funcionalidades incluyendo transporte óptico, conversión de frecuencia, filtrado óptico de RF, multiplexación y demultiplexación de señales, encaminamiento y conmutación, muestreo óptico, generación de tonos, líneas de retardo, conformación de haz en agrupaciones de antenas o generación fotónica de modulaciones digitales, e incluso una combinación de varias de estas funcionalidades. Esta tesis se centra en la aplicación del procesamiento vectorial en el dominio óptico de señales de radiofrecuencia en dos campos de aplicación: la conformación óptica de haces y la modulación y demodulación vectorial fotónica de señales digitales en cuadratura. El control fotónico vectorial permite manipular la amplitud y fase de las señales de radiofrecuencia en el dominio óptico, que es el procesamiento fundamental que se requiere en diferentes aplicaciones tales como las redes de conformación de haces para agrupaciones de antenas y en la modulación en cuadratura. El trabajo descrito en esta tesis incluye diferentes técnicas para implementar una versión fotónica de las redes de conformación de haces de en agrupaciones de antenas, conocidas como redes ópticas de conformación de haces (OBFN). Se estudian dos familias de redes: arquitecturas de retardo en fibra óptica y arquitecturas integradas. Las primeras permiten el control de señales de banda ancha utilizando fibras ópticas dispersivas con técnicas de multiplexado por división de longitud de onda y funcionalidades avanzadas tales como la estimación del ángulo de llegada de la señal en la antena receptora. En la segunda, se estudian redes de conformación pasivas basadas en Matrices de Butler ópticas integradas, incluyendo una solución ultra-compacta utilizando técnicas ópticas heterodinas en silicio sobre aislante (SOI), y una alternativa homodina en sílice dopado con germanio. En esta tesis, también se han investigado técnicas de procesado vectorial fotónico para la generación de modulaciones digitales en cuadratura. Las modulaciones multinivel codifican la información digital en estados discretos de fase y amplitud de una señal eléctrica para aumentar su eficiencia espectral, como por ejemplo la modulación en cuadratura. El procesado necesario para generar y demodular este tipo de señales implica el procesamiento vectorial (control de amplitud y fase) y la conversión de frecuencia. A diferencia de la implementación electrónica o digital convencional, en esta tesis se estudian diferentes técnicas de procesado fotónico tanto para la generación de modulaciones digitales (modulación vectorial fotónica, PVM) como para su demodulación (PVdM). Esto es de particular interés en el caso de señales de banda ancha, donde la velocidad de datos requerida es del orden de gigabits por segundo, para aplicaciones como backhaul inalámbrico de redes ópticas metropolitanas (conocida como fibra hasta el aire). Las técnicas descritas se basan en explotar la dispersión cromática de la fibra óptica, la multiplexación por división de longitud de onda y la conversión en frecuencia. Además, se presenta una solución heterodina implementada monolíticamente en un circuito integrado fotónico (PIC). / [CA] El processament de senyals de radiofreqüència (RF) utilitzant mitjans fotònics és una disciplina que va aparèixer gairebé al mateix temps que el làser i la fibra òptica. La fotònica ofereix la capacitat de manipular senyals de radiofreqüència de banda ampla, una baixa atenuació, processats basats en una àmplia varietat de fenòmens lineals i no lineals i, recentment, el potencial per implementar subsistemes fotònics integrats. Aquestes característiques ofereixen un gran potencial per a la implementació de múltiples funcionalitats incloent transport òptic, conversió de freqüència, filtrat òptic de RF, multiplexació i demultiplexació de senyals, encaminament i commutació, mostreig òptic, generació de tons, línies de retard, conformació de feix en agrupacions d'antenes i la generació fotònica de modulacions digitals, i fins i tot una combinació de diverses d'aquestes funcionalitats. Aquesta tesi es centra en l'aplicació del processament vectorial en el domini òptic de senyals de radiofreqüència en dos camps d'aplicació: la conformació òptica de feixos i la modulació i demodulació vectorial fotònica de senyals digitals en quadratura. El control fotònic vectorial permet manipular l'amplitud i la fase dels senyals de radiofreqüència en el domini òptic, que és el processament fonamental que es requereix en diferents aplicacions com ara les xarxes de conformació de feixos per agrupacions d'antenes i en modulació multinivell. El treball descrit en aquesta tesi inclou diferents tècniques per implementar una versió fotònica de les xarxes de conformació de feixos en agrupacions d'antenes, conegudes com a xarxes òptiques de conformació de feixos (OBFN), amb els objectius de proporcionar un control precís en aplicacions terrestres de senyals de banda ampla a freqüències molt altes per sobre de 40 GHz en antenes de comunicacions, optimitzant la mida i el pes quan es compara amb els homòlegs elèctrics en aplicacions espacials, i la presentació de noves funcionalitats fotòniques per agrupacions d'antenes. Per tant, s'estudien dues famílies de OBFNs: arquitectures de retard en fibra òptica i arquitectures integrades. Les primeres permeten el control de senyals de banda ampla utilitzant fibres òptiques dispersives amb tècniques de multiplexació per divisió en longitud d'ona i funcionalitats avançades com ara l'estimació de l'angle d'arribada del senyal a l'antena receptora. A la segona, s'estudien xarxes de conformació passives basades en Matrius de Butler òptiques en fotònica integrada, incloent una solució ultra-compacta utilitzant tècniques òptiques heterodinas en silici sobre aïllant (SOI), i una alternativa homodina en sílice dopat amb germani. D'altra banda, també s'ha investigat en aquesta tesi tècniques de processament vectorial fotònic per a la generació de modulacions digitals en quadratura. Les modulacions multinivell codifiquen la informació digital en estats discrets de fase i amplitud d'un senyal elèctric per augmentar la seva eficiència espectral, com ara la modulació en quadratura. El processat necessari per generar i desmodular aquest tipus de senyals implica el processament vectorial (control d'amplitud i fase) i la conversió de freqüència. A diferència de la implementació electrònica o digital convencional, en aquesta tesi s'estudien diferents tècniques de processament fotònic tant per a la generació de modulacions digitals (modulació vectorial fotònica, PVM) com per la seva demodulació (PVdM). Això és de particular interès en el cas de senyals de banda ampla, on la velocitat de dades requerida és de l'ordre de gigabits per segon, per a aplicacions com backhaul sense fils de xarxes òptiques metropolitanes (coneguda com fibra fins l'aire). Les tècniques descrites es basen en explotar la dispersió cromàtica de la fibra òptica, la multiplexació per divisió en longitud d'ona i la conversió en freqüència. A més, es prese / Piqueras Ruipérez, MÁ. (2016). Photonic Vector Processing Techniques for Radiofrequency Signals [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63264