Thesis (Ph. D.)--University of Chicago, Department of Chemistry, December 2002. / Includes bibliographical references. Also available on the Internet.

[ES] A día de hoy, las redes de comunicaciones de fibra óptica están alcanzando su capacidad límite debido al rápido crecimiento de la demanda de datos en la última década, generado por el auge de los teléfonos inteligentes, las tabletas, las redes sociales, la provisión de servicios en la nube, las transmisiones en streaming y las comunicaciones máquina-a-máquina. Con el fin de solventar dicho problema, se ha propuesto incrementar la capacidad límite de las redes ópticas mediante el reemplazo de la fibra óptica clásica por la fibra óptica multinúcleo (MCF, acrónimo en inglés de multi-core fiber), la cual es capaz de integrar la capacidad de varias fibras ópticas clásicas en su estructura ocupando prácticamente la misma sección transversal que éstas. Sin embargo, explotar todo el potencial de una fibra MCF requiere entender en profundidad los fenómenos electromagnéticos que aparecen en este tipo de fibras cuando guiamos luz a travésde ellas. Así pues, en la primera parte de la tesis se analizan teóricamente estos fenómenos electromagnéticos y, posteriormente, se estudia la viabilidad de la tecnología MCF en distintos tipos de redes ópticas de transporte, específicamente, en aquellas que hacen uso de transmisiones radio-sobre-fibra. Estos resultados pueden ser de gran utilidad para las futuras generaciones móviles 5G y Beyond-5G en las próximas décadas. Adicionalmente, con el fin de expandir las funcionalidades básicas de las fibras MCF, esta tesis explora nuevas estrategias de diseño de las mismas utilizando la analogía existente entre las ecuaciones que rigen la mecánica cuántica y el electromagnetismo. Con esta idea en mente, en la segunda parte de la tesis se propone diseñar una nueva clase de fibras MCF usando las matemáticas de la supersimetría, surgida en el seno de la teoría de cuerdas y de la teoría cuántica de campos como un marco teórico de trabajo que permite unificar las interacciones fundamentales de la naturaleza (la nuclear fuerte, la nuclear débil, el electromagnetismo y la gravedad). Girando en torno a esta idea surgen las fibras MCF supersimétricas, las cuales nos permiten procesar la información de los usuarios durante la propia propagación de la luz a través de ellas, reduciendo así la complejidad del procesado de datos del usuario en recepción. Finalmente, esta tesis se completa introduciendo un cambio de paradigma que permite diseñar dispositivos fotónicos disruptivos. Demostramos que la supersimetría de mecánica cuántica no relativista, propuesta como una serie de transformaciones matemáticas restringidas al dominio espacial, se puede extender también al dominio del tiempo, al menos dentro del marco de trabajo de la fotónica. Como resultado de nuestras investigaciones, demostramos que la supersimetría temporal puede convertirse en una plataforma prometedora para la fotónica integrada ya que nos permite diseñar nuevos dispositivos ópticos versátiles y ultra-compactos que pueden jugar un papel clave en los procesadores del futuro. Asimismo, con el fin de hacer los resultados principales de esta tesis doctoral lo más generales posibles, se detalla cómo poder extrapolarlos a otros campos de la física como acústica y mecánica cuántica. / [CAT] Avui en dia, les xarxes de comunicacions de fibra òptica estan aconseguint la seua capacitat límit a causa del ràpid creixement de la demanda de dades duante l'última dècada, generat per l'auge dels telèfons intel·ligents, les tablets, les xarxes socials, la provisió de servicis en la núvol, les transmissions en streaming i les comunicacions màquina-a-màquina. Per a resoldre el dit problema, s'ha proposat incrementar la capacitat límit de les xarxes òptiques per mitjà del reemplaçament de la fibra òptica clàssica per la fibra òptica multinúcleo (MCF, acrònim en anglés de multi-core fiber), la qual és capaç d'integrar la capacitat de diverses fibres òptiques clàssiques en la seua estructura ocupant pràcticament la mateixa secció transversal que estes. Tanmateix, explotar tot el potencial d'una fibra MCF requereix entendre en profunditat els fenòmens electromagnètics que apareixen en aquestes fibres quan guiem llum a través d'elles. Així, doncs, en la primera part de la tesi analitzem teòricament aquests fenòmens electromagnètics i, posteriorment, estudiem la viabilitat de la tecnologia MCF en distints tipus de xarxes òptiques de transport, específicament, en aquelles que fan ús de transmissions ràdio-sobre-fibra. Estos resultats poden ser de gran utilitat per a les futures generacions mòbils 5G i Beyond-5G en les pròximes dècades. Addicionalment, a fi d'expandir les funcionalitats bàsiques de les fibres MCF, esta tesi explora noves estratègies de disseny de les mateixes utilitzant l'analogia existent entre les equacions que regixen la mecànica quàntica i l'electromagnetisme. Amb aquesta idea en ment, en la segona part de la tesi proposem dissenyar una nova classe de fibres MCF usant les matemàtiques de la supersimetria, sorgida en el si de la teoria de cordes i de la teoria quàntica de camps com un marc teòric de treball que permet unificar les interaccions fonamentals de la natura (la nuclear forta, la nuclear feble, l'electromagnetisme i la gravetat). Al voltant d'aquesta idea sorgeixen les fibres MCF supersimètriques, les quals ens permeten processar la informació dels usuaris durant la pròpia propagació de la llum a través d'elles, reduint així la complexitat del processament de dades de l'usuari a recepció. Finalment, esta tesi es completa introduint un canvi de paradigma que permet dissenyar dispositius fotónicos disruptius. Demostrem que la supersimetria de mecànica quàntica no relativista, proposta com una sèrie de transformacions matemàtiques restringides al domini espacial, es pot estendre també al domini del temps, almenys dins del marc de treball de la fotónica. Com resultat de les nostres investigacions, demostrem que la supersimetria temporal pot convertir-se en una plataforma prometedora per a la fotònica integrada ja que ens permet dissenyar nous dispositius òptics versàtils i ultracompactes que poden jugar un paper clau en els processadors del futur. Per tal de fer els resultats principals d'aquesta tesi doctoral el més generals possibles, es detalla com poder extrapolar-los a altres camps de la física com ara la acústica i la mecànica quàntica. / [EN] To date, communication networks based on optical fibers are rapidly approaching their capacity limit as a direct consequence of the increment of the data traffic demand in the last decade due to the ubiquity of smartphones, tablets, social networks, cloud computing applications, streaming services including video and gaming, and machine-to-machine communications. In such a scenario, a new class of optical fiber which is able to integrate the capacity of several classical optical fibers approximately in the same transverse section as that of the original one, the multi-core fiber (MCF), has been recently proposed to overcome the capacity limits of current optical networks. However, the possibility of exploiting the full potential of an MCF requires to deeply understand the electromagnetic phenomena that can be observed when guiding light in this optical medium. In this vein, in the first part of this thesis, we analyze theoretically these phenomena and, next, we study the suitability of the MCF technology in optical transport networks using radio-over-fiber transmissions. These findings could be of great utility for 5G and Beyond-5G cellular technology in the next decades. In addition, the close connection between the mathematical framework of quantum mechanics and electromagnetism becomes a great opportunity to explore ground-breaking design strategies of these new fibers that allow us to expand their basic functionalities. Revolving around this idea, in the second part of this thesis we propose to design a new class of MCFs using the mathematics of supersymmetry (SUSY), emerged within the context of string and quantum field theory as a means to unify the basic interactions of nature (strong, electroweak, and gravitational interactions). Interestingly, a supersymmetric MCF will allow us, not only to propagate the light, but also to process the information of users during propagation. Finally, we conclude this thesis by introducing a paradigm shift that allows us to design disruptive optical devices. We demonstrate that the basic ideas of SUSY in non-relativistic quantum mechanics, restricted to the space domain to clarify unsolved questions about SUSY in string and quantum field theory, can also be extended to the time domain, at least within the framework of photonics. In this way, it is shown that temporal supersymmetry may serve as a key tool to judiciously design versatile and ultra-compact optical devices enabling a promising new platform for integrated photonics. For the sake of completeness, we indicate how to extrapolate the main results of this thesis to other fields of physics, such as acoustics and quantum mechanics. / Macho Ortiz, A. (2019). Multi-Core Fiber and Optical Supersymmetry: Theory and Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124964 / TESIS

Les micro-résonateurs à modes de galerie, qu'ils soient déclinés sous forme de disques, anneaux ou hippodromes, sont devenus les éléments constitutifs clés de nombreux composants photoniques de haute performance. Les réalisations exploitant les semiconducteurs III-V sont particulièrement attrayantes car elles ouvrent la possibilité d'intégrer conjointement des sections actives et passives et donc de diversifier les fonctionnalités sur une même puce photonique. Au niveau technologique, l'intégration verticale du résonateur au-dessus de ses guides d'accès permet de distribuer les fonctions actives et passives sur des plans distincts et de faciliter la réalisation des composants grâce à des procédés mieux maitrisés. Une technique de fabrication récemment introduite dans l'équipe et basée sur la filière AlGaAs/AlOx a ainsi permis de réaliser, à l'aide d'étapes simples, des micro-disques couplés verticalement à leur guide d'accès. Les performances de ces composants restent toutefois limitées en raison de leur architecture, complexifiée par les empilements multicouches qui les constituent.Les travaux de recherche menés au cours de cette thèse ont porté sur la faisabilité d'émettre un peigne de fréquences optiques à partir de ces résonateurs. Pour cela, les composants doivent être conçus de manière à présenter un facteur de qualité suffisamment élevé tout en maximisant la puissance circulant dans la cavité, afin de pouvoir déclencher les processus non-linéaires à la base de la génération du peigne. Pour un composant monomode transverse, la puissance intracavité est maximale lorsque le système opère en régime de couplage critique, c'est-à-dire lorsque les pertes internes à la cavité sont égales aux pertes externes (ou pertes par couplage). Nous avons donc développé un outil semi-analytique basé sur une expansion modale afin de réaliser une modélisation paramétrique large bande des performances des systèmes couplés verticalement, encore peu étudiés, tant au plan théorique que pratique. Notre modèle générique exploite la théorie des modes couplés (CMT) et les relations universelles régissant les propriétés spectrales des micro-résonateurs couplés. Nous l'avons étendu en étudiant l'influence spectrale de différents paramètres opto-géométriques sur la fonction de transfert de la cavité couplée et avons, en particulier, mis en évidence par une approche variationnelle, deux conditions théoriques permettant d'obtenir un régime critique achromatique lorsque la cavité et son guide d'accès sont désaccordés en phase. Ce modèle à d'abord été appliqué à la simulation de résonateurs en hippodromes exploitant la filière Si3N4/SiO2 car plusieurs études ont déjà démontré la génération de peignes avec cette plateforme technologique. Ces travaux ont abouti au dessin de structures désaccordées en phase et technologiquement réalisables dont la bande passante critique est augmentée d'un ordre de grandeur par rapport au cas plus répandu de guides accordés en phase. Nous avons ensuite initié une évaluation numérique de la génération de peignes de fréquences, basée sur la résolution itérative de l'équation de Schrödinger non-linéaire prenant en compte les variations des propriétés spectrales et dispersives de ces hippodromes. Le modèle générique a enfin été appliqué aux micro-disques AlGaAs/AlOx. Pour cela, nous avons introduit un critère permettant d'utiliser la CMT dans le cas de coupleurs asymétriques présentant une zone de séparation multicouche. Les résultats, en bon accord avec l'expérience, nous ont permis de mieux appréhender les limitations des dispositifs réalisés et de proposer de nouvelles structures pour en améliorer les performances. Le dessin d'une nouvelle structure AlGaAs/AlOx multicouche permettant d'améliorer les facteurs de qualité des résonateurs jusqu'à deux ordres de grandeurs a ainsi été proposé. La validation expérimentale des dessins proposés tant pour la filière Si3N4/SiO2 que AlGaAs/AlOx est en cours. / Whispering-gallery -mode micro-resonators, whether in the form of disks, rings or racetracks, have become the key building blocks of many high-performance photonic components. The embodiments exploiting the III-V semiconductors are particularly attractive for they open the possibility of integrating active and passive sections together and therefore diversify the functionalities on the same photonic chip. Furthermore, the vertical integration of the resonator above its access waveguide(s) makes it possible to distribute the active and passive functions on distinct planes and makes the realization of the components easier by using better-controlled methods. A fabrication technique recently introduced in the team and based on the AlGaAs / AlOx technological platform, allowed us to realize, by means of simple steps, vertically-coupled microdisks. The performance of these components, however, is limited due to their architecture, complicated by their constitutive multilayer stack. The research carried out during this PhD thesis focused on the feasibility of emitting an optical frequency comb from these resonators. For this purpose, the components must be designed so as to present a sufficiently high quality factor while maximizing the power circulating in the cavity in order to be able to trigger the non-linear processes required for the comb generation. For a transverse single-mode component, the intracavity power is maximal when the system operates in critical coupling regime, i.e .when the losses inside the cavity are equal to external losses (or coupling losses). As a first step, we have developed a semi-analytical tool based on a modal expansion in order to carry out a broadband parametric study of the performances of vertically coupled systems. Up to now, this coupling layout has indeed been little studied, both theoretically and practically. Our generic model, based on the coupled mode theory (CMT) and the universal relations governing the spectral properties of coupled micro-resonators, reveals two theoretical conditions for obtaining an achromatic critical-coupling regime when the cavity and its access waveguide are phase-mismatched. We first applied it to the simulation of single- mode racetrack resonators made of Si3N4 / SiO2 since several studies have already demonstrated comb generation using this technological platform. Our work resulted in the design of phase-mismatched and technologically feasible structures with critical-copuling bandwidths being increased by one order of magnitude compared to the reference case of phase- matched waveguides. We subsequently initiated a numerical evaluation of frequency comb generation, based on the iterative resolution of the non-linear Schrödinger equation taking into account the variations of the spectral and dispersive properties of these racetracks. The generic model has finally been applied to AlGaAs / AlOx microdisks. For this purpose, we have introduced a criterion allowing an unambiguous implementation of CMT in the case of asymmetric couplers having a multi-layer separation zone. The results, in good agreement with experimental data, allowed us to better understand the limitations of the fabricated devices and to propose new structures AlGaAs / AlOx with improved performances. The experimental validation of the proposed designs for both the Si3N4 / SiO2 and AlGaAs / AlOx components is currently in progress.

During the DARPA SCENICC program, J. Ford, et al., demonstrated that CFBs provide a compelling route to compact, wide angle imagers. Monocentric lenses readily provide diffraction-limited images over wide field but onto a hemispherically curved image surface. They demonstrated visible CFBs can be tapered, cut and polished to relay curved images to flat sensors. We have shown that this provides a volumetric imaging efficiency a hundredfold larger than bulk optics can produce; a hundred times the resolution in the same volume or a hundred times less volume for the same resolution. Ford's work leveraged commercial fiber bundles available for the visible spectrum based on silica. We have developed hybrid fiber bundles using step-index confinement between chalcogenide glass cores and polymer cladding with high index-contrast. The high contrast is necessary to provide tight confinement to the high-index As-Se core with minimal crosstalk between closely spaced cores. Tight confinement also minimizes absorption losses in the PEI polymer cladding. The high contrast of this system also provides a large NA to optimize coupling into the CFB from fast lenses. We introduce disorder into the core radius as a mechanism to further decouple adjacent cores, reduce crosstalk and increase fill-factor. We present coupled-mode theory, modal crosstalk superposition, and finite-element modelling to quantify coupling losses and crosstalk as a function of geometry and disorder. We fabricated preforms, drew small fiber bundles and characterized optical properties of the bundles to aid scale-up to megapixel MWIR CFBs.

The integration of high-quality (Q)-factor 3-D filters with highly efficient antennas is addressed in this dissertation. Integration of filters and antennas into inseparable units eliminates the transitions between the otherwise separate structures resulting in more compact and efficient systems. The compact, highly efficient integrated 3-D filter/antenna systems, enabled by the techniques developed herein, allow for the realization of integrated RF front ends with significantly- reduced form factors. Integration of cavity filters with slot antennas in a single planar substrate is first demonstrated. Due to the high Q factor of cavity resonators, the efficiency of the integrated filter/antenna system is found to be the same as that of a reference filter with the same filtering characteristics. This means a near 100% efficient slot antenna is achieved within this integrated filter/antenna system. To further reduce the footprint of the integrated systems, vertically integrated filter/antenna systems are developed. We then demonstrate the integration of cavity filters with aperture antenna structures which enable larger bandwidths compared with slot antennas. The enhanced bandwidths are made possible through the excitation and radiation of surface waves. To obtain omnidirectional radiation patterns , we integrate cavity filters with monopole antennas. Finally, the integration of filters with patch antennas is addressed. Unlike the other filter/antenna integration examples presented, in which the antenna is utilized as an equivalent load, the patch antenna provides an additional pole in the filtering function. The presented techniques in this dissertation can be applied for filter/antenna integration in all microwave, and millimeter-wave frequency regions

Le but de cette thèse est d'étudier d'une façon expérimentale et théorique le comportement synchrone d'un groupe d'oscillateurs contrôlés par la lumière (LCOs). Ces LCOs sont très simples du point de vue électronique et ont la propriété d'imiter le comportement des lucioles puisqu'ils interagissent par des impulsions de lumière. En même temps, les LCOs sont une bonne approche pour étudier d'autres systèmes qui agissent comme des oscillateurs d'intégration et de tir car un LCO est un oscillateur de relaxation à deux échelles de temps :un long processus de charge alterné avec un très court processus de décharge. Une série d'expériences a été menée pour pouvoir comprendre le processus de synchronisation des LCOs. Nous avons trouvé que l'acquisition de la synchronisation est due aux effets de la perturbation à savoir: le raccourcissement de la charge et l'allongement de la décharge. Les mesures expérimentales ainsi que la physique liée aux LCOs nous ont permis de formuler un modèle qui a été utilisé pour trouver d'une façon analytique la courbe de réponse de phase (PRC) qui caractérise un LCO.<p><p>Le modèle a ensuite été validé en comparant les résultats expérimentaux et théoriques. Le modèle reproduit même, le phénomène de bifurcation qui apparaît lorsque trois LCOs sont couplés et disposés en ligne :deux états stables différents apparaissent selon les conditions initiales. L'accord trouvé entre théorie et expérience nous permet d'utiliser le modèle pour étudier d'autres situations qui ne sont pas facilement abordables du point de vue expérimental.<p><p>Nous avons étudié analytiquement deux LCOs identiques couplés. Même pour ce cas idéal, nous étions obligés de faire des simplifications pour pouvoir trouver des solutions exactes. On a trouvé pour ce système deux états possibles qui dépendent des conditions initiales, la synchronisation (stable) et l'anti-synchronisation (instable). Nous avons également montré que le temps de synchronisation augmente avec la distance entre LCOs. La construction des langues d'Arnold (régions de synchronisation) nous a permis de distinguer des régions de synchronisation pure d'ordre n:m et des régions de superposition synchronisation--modulation.<p><p>Nous avons travaillé numériquement avec des systèmes de LCOs affectés de bruits uniforme et Gaussien. Le comportement synchrone de ce système a été caractérisé en utilisant des paramètres statistiques simples tels que la moyenne de la différence de phase linéaire et la variance de la différence de phase cyclique. Nous avons démontré que le bruit, bien qu'il puisse perturber la synchronisation, peut aussi la favoriser entre deux LCOs qui ne se synchroniseraient pas en conditions normales, surtout quand le bruit est Gaussien et que les variances du bruit ne sont pas égales.<p><p>Nous avons étudié en termes statistiques la synchronisation de LCOs couplés localement et arrangés en ligne, en anneau et en réseau. Nous avons montré que la synchronisation totale se produit plus facilement pour des LCOs disposés en anneau. Concernant le temps de synchronisation, il est imprédictible. Les résultats analytiques et numériques suggèrent que la synchronisation totale est le phénomène le plus probable quand le nombre d'oscillateurs n'est pas très grand.<p><p>Finalement, nous avons étudié des LCOs statiques et mobiles couplés globalement. Dans les deux cas, nous avons trouvé que la synchronisation est moins probable quand le nombre d'oscillateurs augmente. Pour la condition statique, en considérant un couplage du type champ moyen, nous avons observé que le temps de synchronisation diminue avec le nombre de LCOs. Cependant, pour la situation plus réaliste dans laquelle l'interaction entre LCOs dépend de la distance les séparant, le temps de synchronisation devient à nouveau imprédictible. Enfin, nous avons étudié l'influence de la mobilité sur la synchronisation, problème qui est important en biologie et en robotique.<p><p>Notre système, de par ses caractéristiques et sa base expérimentale, est beaucoup plus proche de la réalité que ceux considérés d'habitude dans la littérature. Les résultats obtenus peuvent s'appliquer à des systèmes biologiques (lucioles, cellules cardiaques, neurones, …), mais également à la robotique, où la communication à longue portée par la lumière et l'émergence de patterns de synchronisation pourraient être très utiles dans le but d'effectuer des tâches spécifiques. / Doctorat en sciences, Spécialisation physique / info:eu-repo/semantics/nonPublished

Due to its inherent stability and compactness, integrated optics can allow for experimental complexity not currently achievable with bulk optics. This opens up the possibility for large-scale quantum technological applications, such as quantum communication networks and quantum information processing. Quantum information processing relies on efficient sources of entangled photon pairs. Most demonstrations in integrated photonics so far have featured the on-chip manipulation of photon states using a free-space bulk-optic source of photons. This has the drawback of introducing loss due to the spatial mode mismatch between waveguide modes of the chip and modes of the produced photons. In this way, loss limits the number of photons that are simultaneously carried in the integrated optical device, and thus limits the number of qubits. One way to avoid this loss is to generate the photons in another waveguide device. This can be done through, for example, spontaneous four-wave mixing (SFWM). In this third-order nonlinear process, two pump photons spontaneously scatter off each other to create two photons of two new frequencies, satisfying momentum and energy conservation. This has been studied in birefringent optical fibers and photonic crystal fibers. In this work, we investigate the SFWM generation of photons in a waveguide coupler comprised of two touching tapered optical fibers, which we call a microcoupler. The two silica fibers are kept in contact and tapered to be 1 micron in diameter in the 10 cm long uniform interaction region. This device has three main advantages over a standard telecom 2x2 fiber coupler. 1) The small mode area enhances the photon generation rate; 2) The microcoupler supports four modes which is the minimum number required for two-photon entanglement. So in principle the device should be able to produce polarization-entangled photon pairs; 3) The strong waveguide-waveguide coupling and waveguide dispersion (due to the tapering) forces the photons to be far in wavelength from the background light around the pump. We present the 28 allowed phasematching processes for the microcoupler, as well as predict the frequencies of the generated photons. We report the first experimental observation of photon pairs produced via SFWM in a microcoupler. We also analyze the polarization state of the observed photons to figure out which phasematching processes are responsible for generating the photons. We expect to observe more photon pairs in future devices, with the ultimate goal being the generation of polarization-entangled photon pairs for integrated optics.

To be able to harness more power from the wind, wind turbine blades are getting longer. As they get longer, they get more flexible. This creates issues that have until recently not been of concern. Long flexible wind turbine blades can lose their stability to flow induced instabilities such as coupled-mode flutter. This type of flutter occurs when increasing wind speed causes a coupling of a bending and a torsional mode, which create limit cycle oscillations that can lead to blade failure. To be able to make the design of larger blades possible, it is important to be able to predict the critical flutter and post critical flutter behaviors of wind turbine blades. Most numerical research concerning coupled-mode wind turbine is focused on predicting the critical flutter point, and less focused on the post critical behavior. This is because of the mathematical complexities associated with the coupled, nonlinear wind turbine blade systems. Here, a numerical model is presented that predicts the critical flutter velocity and post critical flutter behavior for 3D airfoils with third order structural nonlinearities. The numerical model can account for the attached flow and separated flow region by using the ONERA dynamic stall model. By retaining higher-order structural nonlinearities, lateral and torsional displacements can be predicted, which makes it possible to use this model in the future to control wind turbine blade flutter. Furthermore, by using a dynamic stall model to simulate the flow, the solver is able to predict accurate limit cycle oscillations when the effective angle of attack is larger than the stall angle. The coupled, nonlinear equations of motion are two coupled nonlinear PDEs and are determined using Hamilton’s principle. In order to solve the equations of motion, they are discretized using the Galerkin technique into a set of ODEs. The motion of the airfoil is used as an input to ONERA. The airfoil is sectioned with the lateral position and angle of attack known as well as the velocity and acceleration of the section at an instance of time. This information is used by ONERA to calculate lift and moment coefficients for each section which are then used to calculate the total lift and moment forces of the airfoil. Then, a Fortran code solves the system by using Houbolt’s finite difference method. A theoretical NACA 0012 airfoil has been designed to define the parameters used by the equations of motion. Third bending and first torsional coupling occurs after the critical flutter point and dynamic lift and moment coefficients were observed. Dynamic stall was also observed at wind velocities farther away from the bifurcation point. Bifurcation diagrams, time histories, and phase planes have been created that represent the flutter behavior.

Plasmonic nanostructures can enhance light-matter interactions in the subwavelength domain, which is useful for photodetection, light emission, optical biosensing, and spectroscopy. However, conventional plasmonic devices are optimized to operate in a single wavelength band, which is not efficient for wavelength-multiplexed operations and quantum optical applications involving multi-photon nonlinear processes at multiple wavelength bands. Overcoming the limitations of single-resonant plasmonics requires development of plasmonic devices that can enhance the optical interactions at the same locations but at different resonance wavelengths. This dissertation comprehensively studies the theory, design, and applications of such devices, called "multiresonant plasmonic systems with spatial mode overlap". We start by a literature review to elucidate the importance of this topic as well as its current and potential applications. Then, we briefly discuss the fundamentals of plasmonic resonances and mode hybridization to thoroughly explore, classify, and compare the different architectures of the multiresonant plasmonic systems with spatial mode overlap. Also, we establish the black-box coupled mode theory to quantify the coupling of optical modes and analyze the complicated dynamics of optical interactions in multiresonant plasmonic systems. Next, we introduce the nanolaminate plasmonic crystals (NPCs), wafer-scale metamaterials structures that support many (>10) highly-excitable plasmonic modes with spatial overlap across the visible and near-infrared optical bands. The enabling factors behind the NPC's superior performance as multiresonant systems are also theoretically and experimentally investigated. After that, we experimentally demonstrate the NPCs application in simultaneous second harmonic generation and anti-Stokes photoluminescence (ASPL) with controllable nonlinear emission properties. By designing specific non-linear optical experiments and developing advanced ASPL models, this work addresses some important but previously unresolved questions on the ASPL mechanism as well. Finally, we conclude the dissertation by discussing the potential applications of out-of-plane plasmonic systems with spatial mode overlap in wavelength-multiplexed devices and presenting some preliminary results. / Doctor of Philosophy / Emergence of electronic devices such as cellphones and computers has revolutionized our lifestyles over the past century. By manipulating the flow/storage of electrons at the nanometer scale, electronic components can be very compact, but their speed and energy performance is ultimately limited due to ohmic losses and finite velocity of the electrons. In parallel, photonic devices and circuits have been proposed that by molding the flow of light can overcome the mentioned limitations but are not as integrable as their electronic counterparts. Plasmonics is an emerging research field that combines electronics and photonics using nanostructures that can couple the light waves to the free electrons in metals. By confining the light at deep subwavelength scales, plasmonic devices can highly enhance the light-matter interactions, with applications in ultrafast optical communications, energy-harvesting, optical sensing, and biodetection. Conventionally, plasmonic devices are optimized to operate with a single light color, which limits their performance in wavelength-multiplexed operations and ultrafast non-linear optics. For such applications, it is far more efficient to use the more advanced "multiresonant plasmonic systems with spatial mode overlap" that can enhance the optical interactions at the same locations but for multiple light colors. This dissertation comprehensively studies these systems in terms of the fundamental concepts, design ideas, and applications. Our work advances the plasmonic field from both science and technology perspectives. In particular, we explore and classify the strategies of building multiresonant plasmonic systems with spatial mode overlap for the first time. Also, we establish the black-box coupled mode theory, a novel framework for analysis and design of complicated plasmonic structures with optimized performance. Furthermore, we introduce the "nanolaminate plasmonic crystals" (NPCs), large area and cost-effective devices that can enhance the optical processes for both visible and near-infrared lights. Finally, we demonstrate NPCs ability in simultaneous frequency-doubling and broadband emission of light and come up with advanced theoretical models that can explain the light generation and color conversion in plasmonic devices.

Orientador: Gustavo Silva Wiederhecker / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-02T10:33:51Z (GMT). No. of bitstreams: 1 Luiz_GustavoDeOliveira_D.pdf: 5507367 bytes, checksum: 506db63a5a93a33d67a84dbb1f7b33ce (MD5) Previous issue date: 2017 / Resumo: Nas últimas décadas a optomecânica de microcavidades chamou a atenção de cientistas e engenheiros, que encontraram na interação entre luz e ondas acústicas aplicações que variam de sensores de massa com resolução atômica, até a preparação de estados quânticos de osciladores harmônicos mesoscópicos, passando por simuladores quânticos, filtros ópticos controláveis opticamente, criação de estados topológicos para luz e fônons, apenas citando alguns exemplos. Apesar das diversas demonstrações de vários dispositivos, sendo discos e cristais fotônicos os formatos mais comuns, há ainda um grande esforço no sentido de aperfeiçoá-los reduzindo perdas ópticas e mecânicas e suprimindo outros fenômenos de óptica não-linear, como absorção de dois fótons, que podem impedir seu funcionamento apropriado. Como ressonadores ópticos e mecânicos tipicamente compartilham a mesma estrutura nestes dispositivos, seus projetos são acoplados, dificultando o aprimoramento independente de cada um. Nesta tese usamos dispositivos optomecânicos de campo próximo, cuja interação entre modos mecânicos e ópticos se dá através do campo evanescente do último, para desacoplar o projeto mecânico do óptico, o que nos permitiu estudar a otimização do ressonador mecânico sem qualquer efeito sobre a cavidade óptica. Com um ressonador mecânico de silício composto por dois osciladores acoplados, pudemos demonstrar que o correto equilíbrio das massas de cada oscilador é um método simples e eficiente para suprimir as perdas devido à radiação de energia mecânica para o substrato na escala de frequência de 50 MHz. Este processo permitiu que fatores de qualidade limitados por perdas relacionadas ao material e à superfície, da ordem de 10 mil à temperatura ambiente e de 50 mil a aproximadamente 25 K, fossem obtidos. Também observamos nestes dispositivos o fenômeno de auto-pulsação, que apresenta uma dinâmica própria tão interessante quanto a optomecânica, apesar de impedir a operação apropriada dos osciladores optomecânicos. Estudamos este fenômeno separadamente e demonstramos que estes pulsos, ocorrendo em duas cavidades ópticas acopladas por seus campos evanescentes, podem sincronizar com o campo óptico sendo o único intermediador. Ambas as demonstrações têm implicações importantes, abrindo caminho para o desenvolvimento de novas plataformas de interesse tanto científico quanto tecnológico, como estruturas para o estudo de estados topológicos para a luz e para ondas acústicas e geradores de sinal de radio-frequência de alto desempenho. Além disso, os dispositivos foram todos produzidos em uma fábrica comercial, o que também demonstra que sua fabricação está pronta para ser escalada para produção em massa / Abstract: Cavity optomechanics in the micro-scale has attracted the attention of scientists and engineers on the last few decades, who encountered applications to the interaction of light and acoustic waves ranging from atomic resolution mass sensors to the preparation of quantum states of mesoscopic harmonic oscillators, passing by quantum simulators, optically controllable optical filters, formation of topological states for both photons and phonons, just to mention a few examples. Although various devices have been demonstrated, with disks and photonics crystals being the most common designs, there is still a large effort to improve them by reducing optical and mechanical losses and suppressing other non-linear phenomena, such as two-photon absorption, that may affect their proper operation. Because optical and mechanical resonators typically share the same structure in these devices, their designs are coupled, which complicates the independent improvement of each one. In this thesis we used near-field optomechanical devices, whose mechanical modes interact with the optical through the latter¿s evanescent field, to decouple the mechanical design from the optical, what allowed us to focus all attention on the mechanical resonator. With a silicon mechanical resonator composed of two coupled oscillators, we could demonstrate that the correct balance of the masses of the oscillators is an efficient and simple way to suppress losses due to energy radiation to the substrate at the 50 MHz frequency range. This strategy led to material and surface limited quality factors close to 10k at room temperature and 50k at approximately 25 K. We also observed the phenomenon of self-pulsing in these devices, which presents dynamics as interesting as the optomechanical interactions do, in spite of being a problem for the proper operation of the optomechanical devices. We studied this phenomenon separately and demonstrated that these pulses, when occurring in two evanescently coupled optical cavities, may synchronize with the optical field being the sole intermediary. These two demonstrations have important implications, paving the way for new platforms of scientific and technological interest, such as structures for the study of topological states for both light and acoustic weaves as well as high efficiency radio-frequency signal generators. Moreover, these devices were all fabricated in a commercial foundry, which also demonstrates that the fabrication of such technology is ready to be scaled up to mass production / Doutorado / Física / Doutor em Ciências / 153044/2013-6 / CNPQ