El silicio es un material de suma importancia en microelectronica y en fotonica. Las propiedades semiconductoras del silicio estan detras de los conceptos que gobiernan el funcionamiento de la mayoría de los dispositivos electronicos como los diodos y los transistores. El concepto de integracion ha permitido procesar dispositivos muy pequeños, llegando a alcanzar un tamaño nanometrico. El alto indice de refraccion del silicio permite confinar la luz en estructuras de tamaño micrometrico. Este es el caso de dispositivos fotonicos tales como las guias de onda y las cavidades. Usualmente, tanto los dispositivos fotonicos como los electronicos estan basados en la tecnologia planar, es decir poseen una topologia plana, siendo esto una fuente de perdidas. Es bien conocido que las cavidades esfericas confinan la luz con mas eficiencia que las cavidades planares. Esta tesis trata sobre el desarrollo de un nuevo tipo de microparticulas esfericas que llamamos Coloides de Silicio. Debido a su forma esferica, su alto indice de refraccion y su suave superficie, estas particulas funcionan como microcavidades opticas con modos resonantes bien definidos en el infrarrojo cercano. La tesis reporta sobre la sintesis, y las propiedades estructurales y opticas de los coloides de silicio con diametro entre 0.5 y 3.5 micrometros. Los coloides de silicio pueden facilitar el desarrollo de microcavidades de alto factor de calidad con alta eficiencia de confinamiento de la luz, y permitir la integracion de dispositivos electronicos y fotonicos tales como una union p-n en una sola particula coloidal. Esta tesis reporta tambien sobre los coloides de silicio como elementos integrantes de las Esponjas Fotonicas, las cuales estan formadas por una red desordenada de microesferas de silicio de diferentes tamaños, e interaccionan con la luz fuertemente en un ancho rango de longitudes de onda. / Tymczenko, MK. (2010). Photonic microcavities and photonic sponges based on silicon colloids [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8425 / Palancia

RF and microwave applications represent one of the fastest-growing segments of the high performance electronics market, where ongoing innovation is critical. Manufacturers compete intensively to meet market needs with reduced cost, size, weight and many other performance criteria demands. Under this scenario, transmission lines based on metamaterial concepts can be considered a very interesting alternative to the conventional transmission lines. They are more compact (compatible with planar manufacturing processes) and present higher degrees of design flexibility. Furthermore, metamaterial transmission lines can also provide many other unique properties not achievable with ordinary transmission lines, such as dispersion or impedance engineering. Nevertheless, the impact in the industry is still not relevant, mostly due to the complexity of the related synthesis and design procedures. These procedures are mainly based on the engineer’s experience, with the help of costly full-wave electromagnetic (EM) simulators and parameter extraction methods. The aim of this thesis is to contribute to simplify and speed up the synthesis and design procedures of artificial transmission lines. In particular, the lines obtained by periodically loading a conventional transmission line with electrically small resonators, such as split ring resonators (SSRs) or its complementary particle (CSRR). The design procedure is automated by using Space Mapping techniques. In contrast to other alternative methods, real synthesis is found from the circuit schematic (that provides a given target response) and without need of human intervention. Some efforts to make the method practical and useful have been carried out. Given a certain target response, it is determined whether it can be physically implemented with a chosen technology, and hence proceeding next to find the synthesis, or not. For this purpose, a two-step Aggressive Space Mapping approach is successfully proposed. In contrast to other methods, the real synthesis is found from certain target circuit values (corresponding to the equivalent circuit model that characterizes the structure to be synthesized). Different efforts have been carried out in order to implement a useful and practical method. Some of them were focused to determine if, given certain circuit parameters (which determine the target response) and certain given technology specifications (permittivity and height of the substrate, technology limits), that response is physically realizable (convergence region). This technique was successfully formulated and it is known as “Two-Step Aggressive Space Mapping Approach”. In this work, the latest improvements made till date, from the synthesis of basic unit cells until different applications and kinds of metamaterial-based circuits, are presented. The results are promising and prove the validity of the method, as well as its potential application to other basic cells and more complex designs. The general knowledge gained from these cases of study can be considered a good base for a coming implementation in commercial software tools, which can help to improve its competitiveness in markets, and also contribute to a more general use of this technology. / Rodríguez Pérez, AM. (2014). Synthesis of Planar Microwave Circuits based on Metamaterial Concepts through Aggressive Space Mapping [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48465 / TESIS

L’imagerie effectuée avec des rayons X est largement utilisée de nos jours dans de nombreuses disciplines telles que la physique du solide, les sciences du vivant et la médecine. Les sources de rayons X basées sur la diffusion Thomson d’un faisceau laser par des paquets d’électrons permettent d’obtenir des faisceaux de bonnes qualités pour un faible coût et un faible encombrement. Plusieurs instituts de recherche académiques se sont récemment lancés dans la construction de telles sources qui sont constituées d’un anneau des stockage d’électrons et d’un résonateur optique. Le résonateur optique permet de stocker des impulsions laser focalisées au point d’interaction laser-électron à des fréquences de plusieurs dizaines de méga Hertz. Des flux de rayons X dépassants 10^{11} ph/s peuvent ainsi être obtenus. Dans ce travail de thèse un modèle de stockage d’impulsion a été développé. Ce modèle prend en compte les effets de la phase CEP (carrier-envelope phase) et des décalages temporels permettant d’obtenir des résonances secondaires. Ces résonances sont observées couramment et nous avons pu calculer les gains et finesses équivalentes. Nous avons aussi calculé les corrections non-paraxiales des modes propres d’une cavité non-planaires. Nous avons résolu les équations perturbatives de Lax pour des faisceaux gaussiens elliptiques généralisés. Nous avons pu ainsi décrire qualitativement des résultats expérimentaux obtenus avec une cavité non-planaire constituée de quatre miroirs. Nous avons aussi modélisé l’effet des déformations thermoélastiques des miroirs de cavité en utilisant le modèle simplifié de Winkler. Sur le plan expérimental, nous avons effectué des études sur le résonateur optique prototype du projet EQUIPEX THOMX. Nous avons tout d’abord proposé une nouvelle méthode d’asservissement laser-cavité basée sur l’utilisation d’une possible différence de phase induite par la réflexion des ondes s et p. Comparée à la méthode de Pound-Drever-Hall, notre méthode ne nécessite pas de modulation et démodulation de fréquence. Nous avons effectué les calculs de modélisation ainsi qu’une démonstration expérimentale. En parallèle, nous avons effectué des expériences de stockage de puissance dans la cavité prototype de finesse 26000 et nous avons obtenu une puissance moyenne de 383 kW correspondant à un gain de 10000. Nous avons atteint un niveau de puissance pour laquelle des instabilités modales induites par les déformations thermoélastiques des miroirs de notre cavité deviennent dominantes et perturbent l’asservissement laser-cavité. Une machine à rayon X Thomson, TTX, existe aussi à l’université de Tsinghua. Celle-ci est basée sur un accélérateur linéaire et une source laser femtoseconde terawatt. Un nouveau projet basé sur un anneau de stockage compact d’électrons, TTX2, voit actuellement le jour à l’université de Tsinghua. Nous présentons le design du système optique de ce futur projet. / At present, X-rays imaging is widely applied in solid-state physics, in the life sciences, in medical applications and in other disciplines. An X-ray source based on laser-electron interaction, that is, a Thomson scattering X-ray source, can be used to produce high-quality X-rays at a low cost and small footprint. The construction of compact laser electron sources, consisting of an electron storage ring and an optical enhancement cavity, has recently attracted the interest of many institutions. The optical enhancement cavity is mainly used to amplify the injected power, circulate the pulses at a high repetition frequency (tens of megahertz) and produce a beam with a small waist at the interaction point. When introduced into the electron storage ring, the laser pulses produced in the high-average-power cavity scatter off high-energy electrons at a high repetition frequency. Thus, a high X-ray flux of more than 10^{11} ph/s can be obtained.In order to study the physical process inside a high-power resonator a model has been developed. As a first step, we establish a precise transient model of the laser pulse stacking technique considering the CEP (carrier-envelope phase) effect and time detuning leading to secondary resonances. The results of this model in the time and frequency domains match very well. A cavity with a given finesse and no detuning has a narrower linewidth than a detuned cavity with a higher finesse if both cavities have the same gain; consequently, it is easier to lock a laser to the latter cavity. Next, for the first time, we derived the non-paraxial corrections for general astigmatic beams so as to explain the S-shaped cavity mode observed in a non-planar four-mirror cavity. We solved Lax perturbation series of the wave equation for general elliptic Gaussian beams and S-shaped beam modes appear as the beam propagates away from the cavity symmetry point. This feature agrees qualitatively with observations made on a highly divergent non-planar four-mirror cavity. In addition, we study the thermal effect by using Winkler’s deformation model. The cavity gain is very sensitive to the mirror deformation in open loop. A strong feedback and ultra-low expansion mirrors are indispensable to reach a high power stored in the cavity.Several significant experiments were performed on a prototype cavity of the EQUIPEX project THOMX. Firstly, we proposed a new frequency stabilization method based on the polarization of a folded cavity and tuning of the cavity mirror reflectivity. Sufficient s- and p-wave phase detuning can be obtained by special design of the cavity mirrors’ coatings, which gives rise to an error signal that can be used for locking. Compared to the traditional Pound-Drever-Hall method, this technique is simpler without need for frequency modulation and demodulation. Theoretical calculations and experimental results demonstrate the feasibility of the proposed method. Meanwhile, high-power experiments on the prototype cavity for ThomX were demonstrated. A cavity finesse of approximately 26,000 is measured using four different methods, and the deposition of dust on the cavity mirrors is found to have an enormous effect on the finesse. We achieved a stable average power as high as 383 kW with a cavity gain of 10,000. In addition, modal instabilities which limit this power were observed. We believe that this effect originates from cavity modal frequency degeneracy induced by thermal effect.Tsinghua University hosts a compact, low-repetition-frequency X-ray source knownas TTX, which is based on a linac system and a terawatt femtosecond laser system. The next step is to upgrade TTX to a high-repetition-frequency X-ray machine called TTX2, consisting of an optical cavity and an electron storage ring. We present the complete design of a prototype optical cavity for TTX2.

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Práce se zabývá buzením vyšších módů v kvádrových a válcových dielektrických rezonátorových anténách pro účely zvýšení zisku. Pomocí numerických simulací jsou studovány vlastnosti a limity anténních prvků. Je zkoumáná vzájemní vazba mezi dielektrickými rezonátorovými anténami pracujícími s vyššími vidy a na základě výsledků je možno usuzovat o vhodnosti těchto prvků k popužití v anténních řadách. V práci je popsán analytický model efektivní permitivity perforovaných dielektrik, který respektuje anizotropní povahu tohoto materiálu. Model je založen na Maxwell Garnettové aproximácií nehomogenních materiálů. Dále jsou studovány povrchové vlny na perforovaných substrátech a je ověřena použitelnost teoretického modelu i v tomto případě. Nakonec jsou studovány dielektrické rezonátorové antény vytvořené pomocí perforací v dielektrickém substrátu a je demonstrováno zhoršení určitých vlastností takových antén.

Práce je zaměřena na výzkum nové struktury umožňující charakterizaci fyzikálních vlastností grafenu při přesně řízených podmínkách. Návrh spojuje MEMS piezoelektrický rezonátor spolu s Hall Bar/FET strukturou. Tento přístup umožňuje měnit vlastnosti grafenu odděleně nebo společně dvěma metodami. Mechanický způsob je založen na relativní deformaci způsobené rezonátorem, na kterém je umístěna grafenová monovrstva. Navrhovaná struktura umožňuje měřit vlastnosti grafenu vyvolané pouze změnou mechanického pnutí a frekvencí nucených kmitů bez vlivu vnějšího elektrického pole. Druhý přístup přidává možnost ovládat fyzikální vlastnosti grafenu pomocí elektrického pole FET struktury. Tato technika využívá grafenovou monovrstvu jako laditelný sensor pro molekulární detekci. Měření koncentrace v jednotkách ppb není konstrukčně ničím limitováno. Realizované frekvenčně laditelné piezoelektrické MEMS rezonátory s monovrstvou grafenu budou využitelné v mnoha oblastech pro detekci na molekulové úrovni. Výsledné struktury budou vyrobeny v souladu s požadavky na bio- a CMOS kompatibilitu.

The following work deals with basics of fiber optics, history of fiber optics, and methods of measuring physical quantities with the use of fiber optic sensors. The work includes facts about physics, chemistry and biology - these elements are necessary for a full understanding of the issue. In order to create an optical fiber temperature sensor based on Fabry Perot resonator principle, several methods of manufacturing the optical cavity are investigated. A practical part of paper consist in the manufacturing of the miniature fiber thermometer, its coating and testing.

The diploma thesis deals with pressure pulsations in pipeline system with dynamic muffler. There is presented original geometry of side-branch resonator. Pressure pulsations are solved by a created mathematical model, numerical simulations and verified by an experimental approach. The influence of dynamic and bulk viscosity is involved in derived governing equations. A system of nonlinear equations is solved by genetic algorithm and frequency dependent relationship of bulk viscosity of air is determined afterwards. The correct function of used pressure sensors is tested. The processing of experimental data is performed by the fast Fourier transform with coherent sampling. Finally, a comparison of analytical, numerical and experimental approaches is introduced for different geometric variants of presented muffler.

The thesis deals with microwave resonators synthesis in Matlab environment. Due to the multi-objective optimization, the shape of the resonátor is subsequently changed to fit requested frequency properties. Particle swarm optimization and frequency domain finite element method are used. Accuracy of the different number of elements was tested. Values of several optimization parameters were balanced to reach the maximal efficiency of the optimization.

This thesis deals with design of synchronized sources of time signal. The first part of the thesis deals with the theory the crystal resonators, crystal oscillators and PLL. The second part of the thesis deals with the crystal oscillator with 10MHz frequency. In the oscillator is use of SC cut crystal. The third part of the work deals with method of synchronization. To synchronization is use of PLL.