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<p dir="ltr">Quantum networking holds tremendous promise in transforming computation and communication. While matter-based systems excel as memory nodes, photons are ideal for long-distance transmission. Hence, a hybrid network combining both becomes essential. Moreover, developing entangled photon pair sources is critical for quantum repeaters and network implementation. The realization of these capabilities on integrated photonic circuits is vital for miniaturization and scalability. In this dissertation, we focus on two key aspects: establishing efficient photon-to-memory interfaces and generating and manipulating entangled states within integrated platforms.</p><p dir="ltr">One research direction involves developing an efficient interface between photons and matter-based memory, requiring spectral and temporal mode matching. Spectral compression is inevitable to realize low-loss interconnection between intrinsically narrowband memories and broadband photons. We proposed a novel approach using electro-optic time-varying cavities for spectral compression. Currently, we are working toward realizing this approach on the thin film lithium niobate platform.</p><p dir="ltr">In the other research focus, we encode quantum information as a coherent superposition of multiple optical frequencies; this approach is favorable due to its simplicity in generating high-dimensional entanglement and compatibility with fiber transmission. We successfully generated and reconstructed the density matrix of biphoton frequency combs from integrated silicon nitride microrings, achieving an 8x8 two-qudit dimensionality, the highest to date for frequency-bin qudits. Moreover, we employ Vernier electro-optic phase modulation methods to perform time-resolved measurements of biphoton correlation functions. Currently, we are exploring bidirectional pumping of microrings to generate indistinguishable entangled pairs in both directions, aiming to demonstrate key networking operations such as entanglement swapping and GHZ state generation in the frequency domain. We are also pursuing bidirectional pumping in a Sagnac configuration to generate simultaneous entanglement in both polarization and frequency, with the goal of deployment in a wavelength-multiplexed</p><p dir="ltr">network.</p>

The fundamental components for processing all-optically represented data, namely optical switches and logic gates are investigated. Improved techniques for fabricating nonlinear Fabry-Perot etalons containing GaAs have brought a proliferation of GaAs optical bistable devices. These devices show significant improvements in speed, power requirements, operating temperature and thermal stability. Experiments verify predictions that one can operate a single nonlinear etalon as optical logic gates or two such etalons as a flip-flop. Optimization of the logic gates is then discussed from a systems approach.

Building complex quantum systems has the potential to reveal phenomena that cannot be studied using classical simulation. Photonics has proven to be an effective test-bed for the investigation of such quantum-enhanced technologies, however, the proliferation of bulk optical components is unlikely to be a scalable route towards building more complex devices. Instead, the miniaturisation, inherent phase stability and trivial alignment afforded by integrated photonic systems has been shown to be a promising alternative. In the first half of this thesis, we describe experiments exploiting the quantum interference of three single photons on a reconfigurable integrated photonic chip. We develop a low-loss source of single photons and introduce a low-loss silica-on-silicon waveguide architecture which enables us to show the first genuine quantum interference of three single photons on an integrated platform. A loss-tolerant, element-wise characterisation scheme is developed along with a statistical test to verify that this multi-photon circuit behaves as expected. We then make use of this three-photon interference to detail the first proof-of-principle demonstration of a new intermediate model of quantum computation called boson sampling. Finally, we perform an on-chip demonstration of the quantum teleportation protocol where all key parts --- entanglement preparation, Bell-state analysis and quantum state tomography --- are performed on a reconfigurable photonic chip. The element-wise characterisation scheme developed earlier is shown to be critical to mitigate fabricated component errors. We develop a theoretical model to account for all sources of possible error in the circuit and find good agreement with the measured teleported state fidelities, which exceed the average teleportation fidelity possible with a classical device. We identify the elements of this error budget relevant to scaling and propose improvements to chip characterisation and fabrication in order to achieve high fidelity operation. In the second half, we discuss the use of high efficiency superconducting transition edge sensors in enabling quantum experiments using more photons. We detail the installation and characterisation of these detectors in a new lab in Oxford. We achieve good photon number-resolution and high-efficiency operation. Work to integrate these detectors on the silica-on-silicon waveguide architecture is discussed and we detail the optical and thermal device modelling performed to optimise the on-chip detection efficiency. New, on-chip detectors, fabricated according to this design are shown to operate as expected and achieve high-efficiency and good energy resolution.

Neste trabalho, apresentamos um novo processo de fabricação para a obtenção de canaletas em V em substratos de silício monocristalino (100) para um acoplamento óptico utilizando siliceto de níquel como material de máscara. O filme de siliceto de níquel (10nm de espessura para 200 nm de nickel) foi obtido por processos de evaporação térmica e posterior recozimento a baixas temperaturas ( 200 e 250°C). As canaletas em V (com profundidade de 60 mm) foram fabricadas através do processo de corrosão anisotrópica, utilizando uma solução de KOH (27%-60°C). Durante este processo, a taxa de corrosão do substrato de silício pela solução de KOH foi estimada como sendo 33.1 micrômetros/h. A composição da camada de siliceto de níquel obtida foi investigada utilizando a técnica RBS, que nos forneceu a estequiometria Ni2Si. A rugosidade de filmes de níquel e de Ni2Si foi medida pela técnica AFM. Uma análise SEM foi feita com as canaletas e guias de onda obtidos. Após o processamento das canaletas em V, elas foram alinhadas com um guia de onda simples de teste para um futuro acoplamento óptico. / In this work, we present a new fabrication process to obtain V-grooves on monocrystaline silicon substrates (100) for optical coupling using nickel silicides as mask material. The nickel silicide film 10 nm thick for 200 nm of nickel thick) was obtained using thermal evaporation and annealing processes at low temperatures (200 and 250°C) as mask for alkaline solutions. Vgrooves (60 mm deep) were fabricated by anisotropic etching process, using a KOH (27%-60°) solution. During this process, the etch rate of the silicon substrate by the KOH solution was measured as 33.1 micrometers/h. The composition of the obtained nickel silicide layer was investigated using RBS technique, which supplied us the stoichiometric Ni2Si. The roughness of nickel and Ni2Si layers was measured by AFM technique. A SEM analysis was made with the obtained Vgrooves and waveguides. After processing the V-grooves, they were aligned with a simple waveguide for a future optical coupling.

Les futurs systèmes de communication utiliseront des porteuses de fréquences d'ondes millimétriques (mm) (30 GHz - 300 GHz) et au-delà pour surmonter la saturation des différentes bandes de fréquence et atteindre des débits élevés. Les systèmes radio sur fibre (RoF) ont attiré l'attention grâce à leur faible coût et à la faible atténuation des fibres. Dans le cadre de cette thèse, différentes configurations et plusieurs conceptions de lasers ont été proposées pour la génération de fréquences radio par voie optique. L’amélioration du processus de fabrication de laser développé au laboratoire a permis d’obtenir des sources monomodes émettant autour du pic d'erbium (1534 nm) jusqu'à des puissances optiques de sortie de 41 mW avec une efficacité de 9,8%. Leurs largeurs de raie optiques ont été mesurée égales à 2 kHz et leur bruit d’intensité relatif (RIN) égal à -145 dB/Hz après 50 MHz. Avec ces lasers, des signaux électriques à des fréquences millimétriques de largeur de raie de quelques kHz ont été générés. Trois configurations hétérodynes ont été proposées pour améliorer la stabilité thermique des signaux générés afin de répondre aux normes IEEE. Des lasers co-intégrés ont été de plus fabriqués pour générer des porteuses comprises entre 5GHz et 165GHz. Une étude comparative a montré que les comportements des porteuses ainsi générées étaient indépendants de la fréquence produite. Enfin, les conceptions de structures intégrant coupleur, adaptation de modes et de plusieurs lasers sur verre pompés par une unique source ont été étudiées. En utilisant les porteuses générées par ces dernières réalisations, des transmissions de données ont été accomplies répondant aux normes requises. / Future communication systems will use millimeter-wave (mm) (30 GHz - 300 GHz) frequency carriers and beyond to overcome the saturation of different frequency bands and achieve high data rates. Radio-over-Fiber (RoF) systems have gained attention thanks to their low cost and low fiber attenuation. In this thesis, different configurations and several laser designs have been proposed for radio frequency generation by photonic based technique. The Improvement of the laser fabrication process developed in the laboratory resulted in single-mode sources emitting around the erbium peak (1534 nm) up to 41 mW optical output power with 9.8% efficiency. Their optical linewidths were measured equal to 2 kHz and their relative intensity noise (RIN) equal to -145 dB/Hz after 50 MHz. Using these lasers, electrical signals at millimeter frequencies having linewidths of few kHz have been generated Three heterodyning configurations have been proposed to improve the thermal stability of the generated signals in order to meet the IEEE standards. Co-integrated lasers have been further manufactured to generate carriers between 5GHz and 165GHz. A comparative study showed that the behaviors of the carriers thus generated were independent of the produced frequency. Finally, the designs of structures integrating coupler, tapers and several lasers on glass pumped by a single source were studied. By using the carriers generated by these latest implementations, data transmissions have been accomplished meeting the required standards.

O presente trabalho tem como objetivo principal a produção e estudo de filmes de nitreto de alumínio (AlN) depositados por pulverização catódica (sputtering) reativa e a fabricação e caracterização de guias de onda tipo pedestal utilizando o AlN como núcleo. Inicialmente, filmes de AlN foram fabricados por pulverização catódica reativa (sputtering) de rádio frequência (RF) utilizando um alvo de alumínio (Al) com 99,999% de pureza, e nitrogênio (N2) como gás reativo. Subsequentemente, os filmes foram caracterizados mediante as técnicas de elipsometria, difração de raios X (DRX), espectroscopia de absorção por transformada de fourier na região do infravermelho (FTIR) e espectroscopia de absorção na região do ultravioleta e do visível (UV-VIS). Tendo as melhores condições ópticas e físicas para a deposição de filmes de AlN, foram fabricados neste trabalho guias de onda tipo pedestal utilizando estes filmes como núcleo. O guia de onda pedestal traz um processo de fabricação alternativo, em que a geometria do guia de onda determina-se na camada anterior ao do núcleo, assim já não é necessário delinear as paredes laterais da camada de núcleo facilitando desta forma, o processo de fabricação do dispositivo. Os guias de tipo pedestal fabricados neste trabalho foram definidos através da corrosão parcial do óxido de silício (SiO2) mediante a técnica de RIE (Reactive Ion Etching) usando gases trifluorometano (CHF3) e oxigênio (O2) como gases reativos. Uma vez definido o pedestal, um filme de nitreto de alumínio é depositado sobre o SiO2 com a finalidade de constituir o núcleo do guia de onda. O ar foi utilizado como revestimento superior, cujo índice de refração (n = 1) aumenta o confinamento da luz no núcleo e também para poder possibilitar a caracterização das perdas ópticas do dispositivo. Para esta caracterização usamos a técnica de vista superior que permitiu a análises das perdas ópticas de propagação para diferentes alturas de pedestal e diferentes espessuras de núcleo tanto para filmes de AlN orientado no plano cristalino (002) quanto para filmes de AlN amorfos. / The main objective of this work is the production and study of Aluminum Nitride (AlN) films deposited by reactive sputtering and the fabrication and characterization of pedestal optical waveguides using AlN as core. Initially, aluminum nitride films were produced by reactive sputtering using a 99.999% aluminum (Al) purity target, and nitrogen (N2) as the reactive gas. Subsequently, the films were characterized by ellipsometry, X-ray Diffraction, Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-visible spectroscopy (UV-VIS). Once the best optical and physical conditions for the deposition of AlN films were obtained, pedestal waveguides using these films as a nucleus were fabricated in this work. The pedestal waveguide provides an alternative manufacturing process where the geometry of the waveguide is determined in the pre-core layer, so it is no longer necessary to delineate the side walls of the core layer thereby facilitating the device fabrication process. The pedestal waveguides fabricated in this work were defined by the partial corrosion of SiO2 by the RIE (Reactive Ion Etching) technique using CHF3 and O2 gases as reactive gases. Once the pedestal is completed, an aluminum nitride film is deposited onto the SiO2 layer as the waveguide core. The air was used as an upper cladding, whose refractive index (n ? 1) increases the confinement of the light in the core and also allows the optical loss characterization. For this characterization, we used the superior view technique that allowed the analysis of optical propagation losses for different pedestal heights and different core thicknesses for both highly (002) oriented and amorphous AlN films.

Neste trabalho, foram fabricados guias de onda ARROW (Anti-Resonant Reflecting optical waveguides), através da utilização de filmes finos, de materiais amorfos, obtidos pelas técnicas de Deposição Química a vapor assistida por plasma (PECVD) e Sputtering. Pelo fato de o funcionamento destes guias ser bastante dependente da geometria e das propriedades ópticas dos materiais, foram realizadas simulações utilizando o Método de Matrizes de Transferência (TMM) e o Método de Diferenças Finitas com Reticulado Não Uniforme (NU-FDM) para a determinação dos parâmetros geométricos destas estruturas. Na fabricação, foram utilizados filmes de oxinitreto de silício (SiOxNy) e carbeto de silício amorfo hidrogenado (a-SiC:H), depositados por PECVD, à temperatura de 320°C, e filmes de TiOx depositados por Sputtering, para a fabricação das camadas que compõem os guias de onda. Os filmes de a-SiC:H e TiOx foram utilizados como primeira camada anti-ressonante, possuindo espessuras de 0,322 µm e 86,3 nm, respectivamente. A definição das paredes laterais dessas estruturas foi feita através da Corrosão por Plasma Reativo (RIE) utilizando técnicas fotolitográficas convencionais. Os guias de onda ARROW foram caracterizados em termos de perdas por propagação, para o comprimento de onda de 633 nm, utilizando a técnica de clivagem e a técnica de vista superior. As perdas em função do comprimento de onda para a faixa que vai desde o ultravioleta até o infravermelho próximo (200 nm a 1100 nm) também foram medidas utilizando fonte de luz branca, monocromador e medidor de potência óptica. Além disso, a análise modal dos guias de onda foi feita através de imagens obtidas através de uma objetiva de microscópio e de uma câmera CCD (Charge Coupled Device). Os resultados mostram que é possível obter guias monomodo, com baixas atenuações, tendo se conseguido valores entre 0,8 e 3 dB/cm, para o comprimento de onda de 633 nm. Isso possibilita, no futuro, a fabricação de diversos dispositivos, como sensores interferométricos, sensores químicos baseados em absorção óptica, redes de Bragg, entre outros. / In this work, Anti-Resonant Reflecting Optical Waveguides (ARROW) were fabricated using thin amorphous films, obtained by Plasma Enhanced Chemical Vapor Deposition (PECVD) and Sputtering techniques. Since these waveguides are highly dependent on its geometry and on the optical properties of the materials used, simulations using the Transfer Matrix Method (TMM), and the Non-Uniform Finite Difference Method (NU-FDM), were necessary, for the determination of the geometric parameters of these structures. Silicon oxynitride films (SiOxNy), amorphous hydrogenated silicon carbide films (a-SiC:H), both deposited at a temperature of 320°C, and TiOx films, deposited by Sputtering technique, were used in the fabrication of the layers of the waveguides. The a-SiC:H and the TiOx films were used as first ARROW layer, having thicknesses of 0,322 µm and 86,3 nm, respectively. Also, the definition of the sidewalls of the waveguide was achieved using Reactive Ion Etching (RIE) and conventional lithographic techniques. The waveguides were characterized in terms of propagation losses, for working wavelength of 633 nm, by using the cut-back and the top view techniques. The losses as a function of working wavelength, for the ultraviolet, visible and near infrared regions (200 nm to 1100 nm), were also measured using a white light source, a monocromator and an optical power meter. Furthermore, modal analysis was achieved by using images captured by a Charge Coupled Device (CCD) camera, using a microscope objetctive. Results proved the possibility of obtaining single-mode waveguides with relatively low losses, with values around 0.8 and 3 dB/cm, for working wavelength of 633 nm. This are promising results which indicate the possibility of using these waveguides for the fabrication of many devices such as interferometric sensors, chemical sensors based on optical absorption, Bragg gratings, among others.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Peter Vickers Wright. / Ph.D.

A análise de um sensor óptico de pressão foi realizada neste trabalho. O sensor baseia-se no deslocamento de um diafragma composto por camadas de silício, dióxido de silício e vidro. O deslocamento do diafragma causa a alteração do índice de refração do guia óptico do ramo sensor de um interferômetro de Mach-Zehnder, formado por guias do tipo \"rib\" na camada de vidro. A diferença de fase entre os sinais ópticos dos ramos sensor e de referência causa variação da intensidade luminosa na saída deste interferômetro. A simulação do deslocamento do diafragma foi feita empregando-se o Método das Diferenças Finitas, que também foi, utilizado no cálculo da alteração do índice de refração no guia óptico. O diafragma de três camadas foi substituído, nos cálculos, por outro composto de uma camada equivalente. A análise da propagação da luz no guia tipo \"rib\" foi feita por intermédio do Método do Índice Efetivo. Para a distribuição dos campos elétrico (para o modo TE) e magnético (para o modo TM) admitiu-se uma variação gaussiana na direção y, e a formulação clássica para um guia planar assimétrico, na direção x. O resultado final deste trabalho apresentou melhor aproximação com os dados experimentais do trabalho realizado por OHKAWA [23] do que a própria previsão teórica daquele. São apresentados gráficos do deslocamento do diafragma em função da pressão aplicada, da variação do índice de refração do guia do ramo sensor em função das dimensões geométricas do guia, da distribuição da componente de campo elétrico no guia óptico em função das suas dimensões geométricas, da defasagem entre os sinais dos ramos sensor e de referência em função da pressão aplicada e da pressão de meia-onda em função do comprimento do diafragma. / An integrated optical pressure sensor was analysed in this work. The sensor is based on the deflection of a multilayered diaphragm and operates as a Mach-Zehnder interferometer. A pressure difference between the upper and lower faces of the diaphragm induces a strain and produces a refractive index change in the sensor arm of the interferometer. As a consequence, a phase-shift is established between both arms of the sensor and light intensity modulation is observed at the device output. The Finite Difference Method was used in order to calculate the diaphragm deflection and the refractive index change. In the formulation the multilayered diaphragm was replaced by a single-layered one, with an equivalent bending rigidity. The light propagation in the rib-type waveguide sensor arm was analysed by the Effective lndex Method. A gaussian variation was assumed for the y-component of the electric (TE mode) and magnetic (TM mode) field distributions. In the x-direction the classical formulation was used. Results for the diaphragm deflection dependence on the applied pressure, the refractive index change as a function of the device geometry, phase shift versus applied pressure, as well as halfwave pressure as a function of diaphragm lenght are presented. The final model yield a better agreement to experimental data than the formulations previously available in the literature.