Whispering gallery modes (WGM) microcavity have played an ubiquitous role due to their high quality factor Q and small effective mode volume $V_{eff}$. They are suitable for a broad range of applications and scientific research including cavity quantum electrodynamics (c-QED), sensing, parametric oscillation, frequency comb and so forth. The major nonlinear effect in silica is the Kerr nonlinearity that arises from the dependence of refractive index on the signal intensity. In this thesis, we focus on the theoretical analysis of Kerr and Raman nonlinear effects in a silica spherical microcavity. We derive several analytical models for various nonlinear effects, including self phase modulation (SPM), cross phase modulation (XPM) and stimulated Raman scattering (SRS). The first part of this thesis develops a theoretical framework to describe the impact of Kerr nonlinearity, especially SPM on WGM. First a mathematical formulation to express $\chi^{(3)}$ in spherical co-ordinates is developed. We define the effective mode volume $V_{eff}$ for the the first time to analyze SPM effects by taking $\chi^{(3)}$ tensor in spherical co-ordinates and it is found that the effective mode volume is always smaller than the physical volume of the microsphere. Simulation results show that whispering gallery mode undergoes a negative frequency shift proportional to the injected energy due to SPM. Later, we extended the analysis to describe the nonlinear interaction between two WGMs. An analytical model is developed to describe the XPM effect in microsphere. Expressions for effective mode volumes and effective nonlinear coefficients to describe XPM are derived analytically. It is found that, when the effective mode volume increases, effective nonlinear coefficient becomes smaller and hence, we achieve a lower frequency shift. An analytical expression for the coupling of whispering gallery mode is derived. The resonant frequency of a weak probe mode can be shifted by a strong pump mode due to XPM and the frequency shift of the probe is proportional to the pump energy. Also, An analytical expression for describing the Raman effect in a spherical microcavity is developed by including the delayed Raman response. The results show that the signal power is amplified due to the SRS effect. / Thesis / Master of Applied Science (MASc)

Pillar-array based optical cavities have unique properties, e.g., having a large and connected low dielectric index space (normally air space), exhibiting a large band gap for transverse magnetic modes, having a large percent of electric field energy in air and standing on a substrate. These properties make them well suitable for applications such as optical sensing and terahertz quantum cascade lasers. However there has been rare research in it due to the common belief that pillar arrays have excessive leakage to the substrate. With careful design, we provided several methods to reduce such a leakage and experimentally proved a high quality factor (Q) pillar-array based cavity is practical. We also explored the usage of such a cavity for optical sensing. Numerical methods such as finite-difference time-domain and plane-wave expansion were used in the design of the cavity. Then in microwave spectrum, cavities consisting of dielectric rods were used to test the validity of the theory. Additionally, we observed that a high-Q cavity for modes above light line is feasible and it is very suitable to measure the optical absorption of materials introduce inside the mode volume. Finally in the optical domain, pillar arrays were fabricated in Si/SiO2 material system and measured. Q as high as 27,600 was shown and when applying accurate refractive indices, for every delta n = 0.01, the peak wavelength shifted as large as 3.5 nm, testifying the ultra sensitivity of the cavity to the environmental dielectric change.

Pillar-array based optical cavities have unique properties, e.g., having a large and connected low dielectric index space (normally air space), exhibiting a large band gap for transverse magnetic modes, having a large percent of electric field energy in air and standing on a substrate. These properties make them well suitable for applications such as optical sensing and terahertz quantum cascade lasers. However there has been rare research in it due to the common belief that pillar arrays have excessive leakage to the substrate. With careful design, we provided several methods to reduce such a leakage and experimentally proved a high quality factor (Q) pillar-array based cavity is practical. We also explored the usage of such a cavity for optical sensing. Numerical methods such as finite-difference time-domain and plane-wave expansion were used in the design of the cavity. Then in microwave spectrum, cavities consisting of dielectric rods were used to test the validity of the theory. Additionally, we observed that a high-Q cavity for modes above light line is feasible and it is very suitable to measure the optical absorption of materials introduce inside the mode volume. Finally in the optical domain, pillar arrays were fabricated in Si/SiO2 material system and measured. Q as high as 27,600 was shown and when applying accurate refractive indices, for every delta n = 0.01, the peak wavelength shifted as large as 3.5 nm, testifying the ultra sensitivity of the cavity to the environmental dielectric change.

xvii, 163 p. ; ill. (some col.) A print copy of this title is available from the UO Libraries, under the call number: SCIENCE QC446.2.C85 2008 / We present experimental and theoretical studies of a hemispherical, high-solid-angle external optical micro-cavity strongly coupled to nanoscale optical centers for cavity-quantum electrodynamics (QED) strong coupling and efficient single-photon sources. Implementations of single-photon sources based on various optical centers have been reported in the last three decades. The need for efficient single-photon sources, however, is still a major challenge in the context of quantum information processing. In order to efficiently produce single photons single optical centers are coupled to a resonant high-finesse optical micro-cavity. A cavity can channel the spontaneously emitted photons into a well-defined spatial mode and in a desired direction to improve the overall efficiency, and can alter the spectral width of the emission. It can also provide an environment where dissipative mechanisms are overcome so that a pure-quantum-state emission takes place. We engineered a hemispherical optical micro-cavity that is comprised of a planar distributed Bragg reflector (DBR) mirror, and a concave dielectric mirror having a radius of curvature 60 μm. Nanoscale semiconductor optical centers (quantum dots) are placed at the cavity mode waist at the planar mirror and are located at an antinode of the cavity field to maximize the coherent interaction rate. The three-dimensional scannable optical cavity allows both spatial and spectral selection to ensure addressing single optical centers. This unique micro-cavity design will potentially enable reaching the cavity-QED strong-coupling regime and realize the deterministic production of single photons. This cavity can also be operated with a standard planar dielectric mirror replacing the semiconductor DBR mirror. Such an all-dielectric cavity may find uses in atomic cavity-QED or cold-atom studies. We formulated a theory of single-photon emission in the cavity-QED strong-coupling regime that includes pure dipole dephasing and radiative decay both through the cavity mirror and into the side directions. This allows, for the first time, full modeling of the emission quantum efficiency, and the spectrum of the single photons emitted into the useful output mode of the, cavity. / Adviser: Michael G. Raymer

xv, 204 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This thesis reports on progress made toward realizing strong cavity quantum electrodynamics coupling in a novel micro-cavity operating close to the hemispherical limit. Micro-cavities are ubiquitous wherever the aim is observing strong interactions in the low-energy limit. The cavity used in this work boasts a novel combination of properties. It utilizes a curved mirror with radius in the range of 40-60 µm that exhibits high reflectivity over a large solid angle and is capable of producing a diffraction limited mode waist in the approach to the hemispherical limit. This small waist implies a correspondingly small effective mode volume due to concentration of the field into a small transverse distance. The cavity assembled for this investigation possesses suitably low loss (suitably low linewidth) to observe vacuum Rabi splitting under suitable conditions. According to best estimates for the relevant system parameters, this system should be capable of displaying strong coupling. The dipole coupling strength, cavity loss and quantum dot dephasing rates are estimated to be, respectively, g = 35µeV, κ = 30µeV, and γ = 15µeV. A survey of two different distributed Bragg reflector (DBR) samples was carried out. Four different probe lasers were used to measure transmission spectra for the coupled cavity-QED system. The system initially failed to display strong coupling due to the available lasers being too far from the design wavelength of the spacer layer, corresponding to a loss of field strength at the location of the quantum dots. Unfortunately, the only available lasers capable of probing the design wavelength of the spacer layer had technical problems that prevented us from obtaining clean spectra. Both a Ti:Al 2 O 3 and a diode laser were used to measure transmission over the design wavelength range. The cavity used here has many promising features and should be capable of displaying strong coupling. It is believed that with a laser system centered at the design wavelength and possessing low enough linewidth and single-mode operation across a wide wavelength range strong coupling should be observable in this system. / Committee in charge: Hailin Wang, Chairperson, Physics; Michael Raymer, Advisor, Physics; Jens Noeckel, Member, Physics; Richard Taylor, Member, Physics; Andrew Marcus, Outside Member, Chemistry

Ce travail porte sur la réalisation d'un micro-écran OLED haute luminance sur silicium. L'efficacité limitée des structures WOLED associées à des filtres colorés est un frein au développement de cette technologie pour des applications dans des dispositifs de type « see-through ». Nous proposons une approche tirant parti de l'effet de microcavité optique présent dans les écrans OLED à émission vers le haut pour générer des couleurs sans filtres. Les modulations de cavité à l'échelle du sous-pixel étant assurées par l'insertion d'oxyde transparent conducteur entre l'anode et l'OLED.L'étude offre selon un raisonnement cohérent de suivre les différentes phases de la réalisation d'un démonstrateur de ce type. Seront abordées dans la première partie les étapes technologiques de structuration de l'oxyde à l'échelle d'un sous-pixel de 16µm². Nous traiterons ensuite du développement d'un empilement OLED tandem utilisant des émetteurs fluorescent et phosphorescents. Une approche par simulation optique sera utilisée pour l'optimisation de cette architecture à un fonctionnement sur microcavité. Puis la discussion autour de la mise en commun des blocs technologiques précédents permettra d'aborder des écueils spécifiques au micro-écran OLED et de proposer des pistes de résolution. / This study focuses on the realization of a high brightness OLED micro-écran on silicon. The limited efficiency of White-OLED combined with color filters prevents the use of this technology in “see-through” applications. We propose a novel approach getting benefits from the optical micro-cavity effect in Top-Emitting OLED to generate colors without using color filters. Cavity modulations at a sub-pixel scale are realized by using a Transparent Conducting Oxide between the anode and the OLED.Following a step-by-step reasoning the work offers to follow all the phases of the realization of a prototype using this principle. In the first part, the technological steps of the processing of oxide cavities with a surface of 16µm² will be discussed. Then we will work on the development of a tandem OLED structure using both fluorescent and phosphorescent emitters optimized for micro-cavities. To this end optical simulation will be used. The two technological blocs will finally be put together to enlighten some issues specific for micro-écran technology and to give some clues to solve them.

Ce travail de thèse concerne la réalisation et l'analyse des propriétés optiques de nanocristaux de silicium. Ces objets de taille nanométrique possèdent des propriétés optiques remarquables, en particulier de photoluminescence. Les propriétés de confinement quantique qui les caractérisent permettent d'obtenir un signal de luminescence intense dans le domaine du visible. Des composants optoélectroniques et photoniques ont été envisagés à base de nanocristaux de silicium. Les raisons physiques du fort signal de luminescence en revanche sont encore mal comprises. Les nanocristaux de silicium sont élaborés par évaporation. L'élaboration et le recuit thermique de multicouches SiO/SiO2 permet d'obtenir des nanocristaux de silicium de diamètre moyen bien contrôlé. Ceux-ci sont issus de la démixtion de la couche de SiO selon la réaction SiOx --> Si + SiO2. Le contrôle du diamètre des nanocristaux de silicium permet de maîtriser la région spectrale de luminescence dans la région du visible.La première partie de ce travail de thèse vise à isoler un ou quelques nanocristaux de silicium. L'objectif est de remonter à la largeur homogène de ces nano-objets. Dans un premier temps, une étude centrée sur le matériau SiOx est réalisée afin de réduire la densité surfacique de nanocristaux de silicium. Dans un deuxième temps, des moyens de lithographie ultime sont mis en oeuvre afin de réaliser des masques percés de trous de diamètres de l'ordre de la centaine de nanomètre. Des expériences de spectroscopie optique sont réalisées sur ces systèmes.La deuxième partie de ce travail vise à contrôler l'émission spontanée de lumière issue des nanocristaux de silicium. Ceci se fait en couplant les modes électroniques aux modes optiques confinés d'une microcavité optique. Le manuscrit détaille les moyens développés afin d'obtenir une microcavité optique dont les modes optiques puissent se coupler efficacement aux nanocristaux de silicium. Les propriétés optiques de ces systèmes sont finalement analysées. / This work concerns the implementation and analysis of optical properties of silicon nanocrystals. These nanoscaled objects have remarkable optical properties, especially in photoluminescence. The properties of quantum confinement that characterize them allow obtaining an intense luminescence signal in the visible range. Optoelectronic and photonic devices have been proposed based on silicon nanocrystals. The physical reasons of the strong luminescence signal, however, are still poorly understood. The silicon nanocrystals are prepared by evaporation. The preparation and thermal annealing of multilayers SiO/SiO2 leads to silicon nanocrystals with a well controlled average diameter. They are created during the demixing of the SiO layer by the reaction SiO ? Si + SiO2. The control the diameter of the silicon nanocrystals influences directly the spectral region of luminescence in the visible region.The aim of first part of this work is to isolate one or a few silicon nanocrystals. The intent is to trace the homogeneous width of these nano-objects. Initially, a study focusing on the SiOx material is conducted to reduce the surface density of silicon nanocrystals. In a second step, lithography is implemented to make masks with holes with diameters of about one hundred nanometers. Optical spectroscopy experiments were performed on these systems.The second part of this work aims controlling the spontaneous emission of light from silicon nanocrystals. This is done by coupling the electronic transmission to optical modes confined in an optical microcavity. The manuscript describes the methods developed to obtain an optical microcavity whose optical modes can be coupled effectively to the silicon nanocrystals. The optical properties of these systems are finally analyzed

Il est possible de modifier en quelques picosecondes les fréquences de résonance d’une microcavité optique semiconductrice en injectant optiquement des porteurs de charge dans le semiconducteur. Dans cette thèse, nous étudions en détail de tels évènements de commutation tout-optique pour des cavités planaires et des cavités en forme de micropilier à base de GaAs/AlAs, en utilisant l’émission de boîtes quantiques intégrées dans ces cavités comme source interne de lumière pour sonder la fréquence des modes résonnants en fonction du temps. Des décalages en fréquence très conséquents, de l’ordre de 34 fois la largeur du mode considéré, sont obtenus après optimisation. Nous réalisons une commutation différentielle des modes d’un micropilier en injectant les porteurs de manière très localisée, et modélisons les comportements observés en prenant en compte la distribution des porteurs injectés ainsi que leur diffusion et leur recombinaison en fonction du temps. Nous étudions par ailleurs deux applications potentielles importantes de la commutation ultrarapide de cavité. D’une part, nous modélisons le changement de couleur qui est induit sur de la lumière piégée dans un mode de cavité lors d’un évènement de commutation. Nous montrons que pour une cavité planaire optimisée, une telle conversion de fréquence peut être réalisée de façon très efficace. D’autre part, la commutation de cavité peut aussi être employée pour contrôler en temps réel l’émission spontanée d’émetteurs intégrés, et plus généralement tous les effets d’électrodynamique quantique en cavité. Nous présentons la génération d’impulsions de lumière incohérente de quelques picosecondes seulement, en utilisant l’émission spontanée de boîtes quantiques dans un micropilier commuté. Nous montrons aussi par une étude théorique qu’il est possible de donner une forme choisie aux impulsions à un photon émises par une boîte quantique, ce qui ouvre des applications intéressantes dans le domaine des liens optiques quantiques et du traitement quantique photonique de l’information. / The resonance wavelengths of semiconductor optical microcavities can be changed within few picoseconds through the optical injection of free charge carriers. In this PhD thesis, we study in detail such “cavity switching” events for GaAs/AlAs planar and micropillar cavities, using the spontaneous emission of embedded QDs as an internal light source to probe the time-dependent frequencies of the cavity modes. Switching amplitudes as large as 34 mode linewidths are observed for optimized pumping conditions. Differential switching of micropillar modes is achieved by performing a localized injection of charge carriers, and modeled by taking into account their injection profile, diffusion and recombination processes. We investigate two important potential applications of cavity switching in the field of quantum optics. On one hand, we model the frequency conversion of light trapped in a cavity mode, which is induced by a switching event, and show that adiabatic and highly efficient frequency conversion can be achieved in properly designed planar cavities. On the other hand, cavity switching appears as a powerful resource to control in real-time the spontaneous emission of embedded emitters and more generally CQED effects. As a first example, we demonstrate the generation of few picosecond short pulses of incoherent light, using the spontaneous emission of switched QD-micropillars. We also show theoretically that cavity switching can be used to shape the time-envelope of single photon pulses emitted by a single QD, which is highly desirable for quantum-optical links and photonic quantum information processing.

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