Les accélérateurs de particules hyperfréquences sont au cœur de projets d’envergure aux visées scientifiques (comme l’European Spallation Source) ou énergétiques (comme le réacteur hybride MYRRHA). Pour ces applications, les cavités résonnantes composant ces accélérateurs doivent atteindre des champs accélérateurs très importants. Elles ont alors besoin d’une grande puissance RF. Le coupleur de puissance doit permettre d’injecter cette puissance dans la cavité tout en garantissant une grande fiabilité. L’étude d’un coupleur à 704,4MHz a été réalisée. Les comportements radiofréquences, thermiques et mécaniques ont été modélisés pour une puissance de 50kW en réflexion toutes phases. Les performances simulées permettent d’envisager son utilisation comme coupleur pour les cavités elliptiques de l’ADS MYRRHA. L’industrialisation d’un tel coupleur a également été étudiée. Cette étude a donné lieu à la fabrication de deux prototypes. L’étude d’un coupleur à 352MHz a également été réalisée afin de répondre aux exigences de la cavité SPOKE ESS. Un nouveau processus d’assemblage, impliquant une méthode de précontrainte de la céramique, sera exposé. Ce processus diminue le nombre d’étapes de fabrication et renforce mécaniquement la fenêtre du coupleur. Cette thèse a également permis la validation de l’extension aux ondes progressives d’un logiciel de simulation 3D du multipactor : Musicc3D. Les simulations et les mesures ont été favorablement comparées pour les coupleurs SPIRAL2 et XFEL. / Nowadays, the number of projects aiming at building high intensity proton linear accelerators is increasing thanks to a large field of applications: particles & nuclear physics, spallation sources and some applications in material sciences, biology and nuclear waste reprocessing. All these linear accelerator projects are based on superconducting technology that allows high accelerating gradients in continuous mode. The RF power coupler is one of the main components of the accelerator. It is designed to transmit the radio frequency power from the waveguide at room temperature to the cavity at 4 Kelvin with high reliability. In this thesis, a study of a 704.4MHz power coupler was carried out. The RF, thermal and mechanical behaviors of the coupler were simulated for 50kW full reflection continuous wave. This power coupler could be used as RF injector for MYRRHA elliptical cavities. The fabrication process has been established and two prototypes were build. A study of a 352MHz power coupler was also carried out to fulfill ESS Spoke cavities needs. The obtained design satisfies the specifications and lowers the maximum electric field in the power coupler window compared to existing design. Then a new fabrication process was developed using prestressed ceramic. Brazing operations have halved with this new process. It was shown that the prestressed could enhance the strengths ceramic. The last study in this thesis consisted in validating an extension to progressive waves of 3D simulation software of Multipacting, Musicc3D. The results obtained were favorably compared to the measurements for SPIRAL2 and XFEL power couplers.

In this thesis by articles, I propose and demonstrate the full design, fabrication and characterization of optical biosensors based on (Bloch) Long Range Surface Plasmon Polaritons (LRSPPs). Gold waveguides embedded in CYTOP with an etched microfluidic channel supporting LRSPPs and gold waveguides on a one-dimensional photonic crystal (1DPC) supporting Bloch LRSPPs are exploited for biosensing applications. Straight gold waveguides embedded in CYTOP supporting LRSPPs as a biosensor, are initially used to measure the kinetics constants of protein-protein interactions. The kinetics constants are extracted from binding curves using the integrated rate equation. Linear and non-linear least squares analysis are employed to obtain the kinetics constants and the results are compared. The device is also used to demonstrate enhanced assay formats (sandwich and inhibition assays) and protein concentrations as low as 10 pg/ml in solution are detected with a signal-to-noise ratio of 20 using this new optical biosensor technology. CYTOP which has a refractive index close to water is the fluoropolymer of choice in current state of the art waveguide biosensors. CYTOP has a low glass transition temperature which introduces limitations in fabrication processes. A truncated 1D photonic crystal can replace a low-index polymer cladding such as CYTOP, to support Bloch LRSPPs within the bandgap of the 1DPC over a limited ranges of wavenumber and wavelength. Motivated by quality issues with end facets, we seek to use grating couplers in a broadside coupling scheme where a laser beam emerging from an optical fiber excites Bloch LRSPPs on a Au stripe on a truncated 1D photonic crystal. Adiabatic and non-adiabatic flared stripes accommodating wide gratings size-matched to an incident Gaussian beam are designed and compared to maximise the coupling efficiency to LRSPPs. The gratings are optimized, initially, through 2D modelling using the vectorial finite element method (FEM). Different 3D grating designs were then investigated via 3D modelling using the vectorial finite difference time domain (FDTD) method. Given their compatibility with planar technologies, gratings and waveguides can be integrated into arrays of biosensors enabling multi-channel biosensing. A multi-channel platform can provide, e.g., additional measurements to improve the reliability in a disease detection problem. Thus, a novel optical biosensor based on Bloch LRSPPs on waveguide arrays integrated with electrochemical biosensors is presented. The structures were fabricated on truncated 1D photonic crystals comprised of 15 period stack of alternating layers of SiO2/Ta2O5. The optical biosensors consist of Au stripes supporting Bloch LRSPPs and integrate grating couplers as input/output means. The Au stripes also operate as a working electrode in conjunction with a neighboring Pt counter electrode to form an electrochemical sensor. The structures were fabricated using bilayer lift-off photolithography and the gratings were fabricated using overlaid e-beam lithography. The planar waveguides are integrated into arrays capable of multichannel biosensing. The wafer is covered with CYTOP as the upper cladding with etched microfluidic channels, and wafer-bonded to a borofloat silica wafer to seal the fluidic channels and enable side fluidic interfaces. The proposed device is capable in principle of simultaneous optical and electrochemical sensing and could be used to address disease detection problems using a multimodal strategy.

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One of the major purposes of this project was to demonstrate optical components which will be used in fibre optic distribution systems. These include the fibre itself, couplers, connectors, splices, sources and detectors. All components used are state-of-the-art, the star coupler and fusion splice technique being developed by the author during the completion of the project. The star coupler has proved to have one of the lowest insertion losses of any such component to date. Although the telephone system demonstrated has only 3 stations, very similar or identical components would be used in an expanded network. / Thesis / Master of Engineering (MEngr)

Данная работа посвящена миниатюризации квадратурных и кольцевых мостовых устройств. Описана процедура проектирования миниатюрных конструкций, основанная на замене отрезка микрополосковой линии передачи на фильтр нижних частот, обладающий таким же фазовым сдвигом, что и заменяемый отрезок. Проведено моделирование предлагаемых конструкций и получены их частотные характеристики. Изготовлены опытные образцы, и измерены их характеристики, которые подтверждают работоспособность устройства. / This work is dedicated to the miniaturization of the quadrature ring and bridge devices. The procedure of designing miniature structures based on replacement of a segment of microstrip transmission line on a low-pass filter, which has the same phase shift that model and cut. The simulation of the proposed designs and obtained their frequency characteristics. Built prototypes of, and measured their characteristics, which confirm the efficiency of the device.

In this dissertation, some multi-function and flexible RF/microwave devices have been studied to solve the issues in the modern microwave system designs. First, a power divider with two functions is proposed. The first function is a zero-phase delay power divider using zero-phase impedance transformer. The second function is a power divider with impedance transforming property. To achieve the first function, the two arms are treated as zero-phase impedance transformers. When the phase requirement is relaxed, the second function is obtained. Shunt transmission line stubs are employed to connect the isolation resistor, which provides great flexibility in the design. Then, a balun with transparent termination impedance and flexible open arms is designed. The design parameters of the balun are independent to the port impedance. This property allows the balun to work with different system impedances. Furthermore, the two output ports of the balun do not need to be connected together, which enables the device to have a very flexible structure. Finally, the continuous research of a tunable/reconfigurable coupler with equal output impedance is presented. In addition to the tunable/reconfigurable responses, unequal output impedance property is added to the microstrip line coupler. To shrink the size at the low frequency and make it easy for fabrication at higher frequency, the coupler is redesigned using lumped components. To validate the design theories, simulations are carried out. Moreover, prototypes of the power divider and the balun are fabricated and characterized. The simulation and measurement results match well with the theoretical calculation.

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The performance of fused fiber couplers is wavelength dependent. Wavelength spectral compensation is a technique to decrease the effect of the wavelength dependence, which is an essential task for many applications in fiber optic communication systems. Fiber devices such as wavelength-flattened couplers (WFCs) can be fabricated using wavelength spectral compensation methods. In this dissertation, wavelength spectral compensation techniques in fused biconical taper (FBT) couplers including both multimode and single-mode fiber couplers are studied in detail. In multimode fiber coupler operation, a novel theoretical model based on frustrated total internal reflection (FTIR) has been developed to effectively describe the power coupling and loss mechanism. Experimental results support the theoretical predictions. In single-mode fiber couplers, the conventional technique of fabricating WFCs is discussed. An alternative analytical model has been developed based upon coupled mode theory, which provides a relatively simple and mathematically sound explanation to the wavelength spectral compensation. Aiming to simplify WFC fabrication, a new way of constructing WFCs is proposed and demonstrated by connecting regular single-mode fiber couplers, some of which serve as wavelength spectral compensators. WFCs of various structures including 2x2, 1x3, 1x2ᴺ, and 4x4 have been developed, and the experimental data agree with theoretical predictions of performance. Potential applications and future research directions in wavelength spectral compensation are also presented. / Ph. D.

As multimedia devices advance, current high-speed wireless standards may soon struggleto support their growing demand for data speeds. This results in limitations in bandwidthfor applications, notably affecting activities like streaming high-definition television andultra-high-definition video. The proposed solution is to go up in frequency (millimeterwaves) allowing for use of greater bandwidths, in new bands. A problem is, however,that the path loss at mmWave frequencies is substantially greater than at frequencies below6GHz, currently the main frequency range used by both cellular and Wi-Fi. In order tocompensate for the increase in pathloss, wireless systems operating at mmWave frequenciesneed to use high gain antennas e.g. antenna arrays. Such arrays operate using digital oranalog beamforming. In this thesis the design, fabrication and verification of an analogbeamforming network connected to a four-antenna element patch array implemented at26GHz on a four-layer printed circuit board is presented. The components of the structuresof the Butler matrix beamforming network were designed and evaluated in simulationsusing CST. The stack up is a four-layer PCB-board with antenna elements and feedingnetwork on opposite outer layers. All structures in the Butler matrix were constructedin micro strip line with characteristic impedance of 50 ohm on Rogers RT-duroid 5880substrate to reduce dielectric losses. The designed 4x4 Butler matrix aimed at four set stateswith progressive phase differences ±45 and ±135 resulting in main lobes with direction -40,-15, 14 and 39 degrees. In the simulation, a progressive phase difference up to a deviationof up to 8.6 degrees was observed for all states. The fabricated Butler matrix was verified onan antenna measurement range to have main lobe directions of -45, -15, 15 and 40 degreesand with half power beam widths (HPBW) of 27.5, 25, 25 and 27.5 degrees respectively.The nulls between each lobe in the radiation pattern had a relative gain compared to peakvalue of -12.2 dBi resulting in similar magnitude as noise floor. The side lobe suppressionwere evaluated to minimum of 6.3 dB. The high directivity and well-defined nulls confirmthe hybrid couplers properties of equal power division as well as phase difference betweenoutput ports. The patch antennas were verified to have a dominant linear polarization butthe peak value for all lobes shows a deviation of -4.1 dB for all measurements comparedto simulation. In conclusion the final patch antenna array and Butler matrix performed asexpected from the simulation. Indicating that the proposed analog beam forming antennadesign is robust and well suited to be used in e.g. Open RAN applications.