Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

In the last few years research has identified Photonic Crystals (PhCs) as promising material that exhibits strong capability of controlling light propagation in a manner not previously possible with conventional optical devices. PhCs, otherwise known as Photonic Bandgap (PBG) material, have one or more frequency bands in which no electromagnetic wave is allowed to propagate inside the PhC. Creating defects into such a periodic structure makes it possible to manipulate the flow of selected light waves within the PhC devices outperforming conventional optical devices. As the fabrication of PhC devices needs a high degree of precision, we have to rely on accurate numerical modelling to characterise these devices. There are several numerical modelling techniques proposed in literature for the purpose of simulating optical devices. Such techniques include the Finite Difference Time Domain (FDTD), the Finite Volume Time Domain (FVTD), and the Multi-Resolution Time Domain (MRTD), and the Finite Element (FE) method among many others. Such numerical techniques vary in their advantages, disadvantages, and trade-offs. Generally, with lower complexity comes lower accuracy, while higher accuracy demands more complexity and resources. The Complex Envelope Alternating Direction Implicit Finite Difference Time Domain (CE-ADI-FDTD) method was further developed and used throughout this thesis as the main numerical modelling technique. The truncating layers used to surround the computational domain were Uniaxial Perfectly Matched Layers (UPML). This thesis also presents a new and robust kind of the UPML by presenting an accurate physical model of discretisation error. iv This thesis has focused on enhancing and developing the performance of PhC devices in order to improve their output. An improved and new design of PhC based Multiplexer/Demultiplexer (MUX/DEMUX) devices is presented. This is achieved using careful geometrical design of microcavities with respect to the coupling length of the propagating wave. The nature of the design means that a microcavity embedded between two waveguides selects a particular wavelength to couple from one waveguide into the adjacent waveguide showing high selectivity. Also, the Terahertz (THz) frequency gap, which suffers from a lack of switching devices, has been thoroughly investigated for the purpose of designing and simulating potential PhC based switching devices that operate in the THz region. The THz PhC based switching devices presented in this thesis are newly designed to function according to the variation of the resonant frequency of a ring resonator embedded between two parallel waveguides. The holes of the structures are filled with polyaniline electrorheological fluids that cause the refractive index of the holes to vary with applied external electric field. Significant improvements on the power efficiency and wavelength directionality have been achieved by introducing defects into the system.

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Lead halide perovskites are attractive material systems for both classical and quantum light emission because of their facile and diverse synthetic techniques, broad tunability in bandgap energy, high emission quantum efficiencies, and the possibility strong light-matter coupling. Despite extensive research into lead halide perovskites, there remain extensive debates into the mechanisms behind various light emission processes. This thesis has three objectives. First, to understand the properties of perovskite nanowire lasers as well as the underlying photophysics. Second, to differentiate between behavior in the weak versus strong light matter coupling regimes. Finally, to understand where perovskites in distributed Bragg reflector microcavities fall in these regimes. A combination of static, time, and angle resolved spectroscopy is used to study nanowire and microcavity systems in combination with numerical methods to interpret the results. Perovskite nanowire emission is shown to arise from stimulated emission from an electron-hole plasma and coupling with bulk plasmons, while perovskite microcavities offer the possibility of strong coupling and emission from a polariton condensate. The spatial confinement of the photonic structure and quasi-spin orbit coupling in perovskite cavities are discussed as powerful tools which could extend the coherence time of polariton condensates in these systems.

No description available.

A study of photon production in multi-hadronic final states has been made at center-of-mass energies from 55 to 58 GeV with the AMY detector at the KEK e+e- storage ring TRISTAN. / Ph. D.

Les corrélations de photons sont à la base d'un certain nombre d'expériences et d'applications (spectroscopie de corrélation de photons, profilométrie haute résolution, cryptographie quantique, téléportation). L'évaluation de ces propriétés de corrélation revêt dès lors une importance toute particulière et correspond à la thématique dans laquelle s'inscrit ce travail de thèse de Doctorat. Tout d'abord, les concepts de compteur de photons par absorption à deux photons ont été (ré)évalués expérimentalement dans différents semiconducteurs et nous ont conduits à établir les bases d'un modèle quantique du comptage à deux photons. Par la suite, l'absorption à deux photons dans les semiconducteurs est appliquée dans une nouvelle technique qui permet la mesure du degré de cohérence d'ordre deux de sources optiques continues de faibles puissances (0,1 µW au minimum) avec une bande passante allant de 1,1 à 1,7 µm et une résolution de l'ordre de la femtoseconde. Expérimentalement, le montage est conceptuellement proche d'un interféromètre de Hanbury Brown et Twiss où, dans notre cas, les deux sous-faisceaux décalés dans le temps sont recombinés sur un compteur à deux photons. Grâce à la très large bande passante à deux photons, les corrélations de sources larges spectralement sont caractérisées au moyen de ce montage qui permet la mesure du degré de cohérence d'ordre deux de sources chaotiques aussi bien que d'un générateur paramétrique à la dégénérescence ou hors de la dégénérescence. Pour la première fois, le phénomène de bunching des photons issus d'un corps noir a été vérifié par une mesure directe. Pour ce qui est de la lumière paramétrique, après avoir développé une source de photons jumeaux, nous avons démontré que notre montage expérimental était à même de mesurer les coïncidences exactes des photons issus d'une même paire aussi bien que les coïncidences accidentelles entre photons de paires différentes en contrôlant les phénomènes de dispersion chromatiques à l'aide d'une paire de prismes. Enfin, deux modèles théoriques originaux de corrélation de photons jumeaux ont été développés, basées sur les approches quantique et classique, et sont en excellent accord avec l'ensemble de nos résultats expérimentaux.

No description available.

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy