Thesis (MA. (Archaeology))-University of Pretoria, 2005. / Includes bibliographical references (leaves 124-139). Available on the Internet via the World Wide Web.

Efficient and high light amplification of optical resonator in organic laser is one of the critical factors for high performance organic laser. It can be achieved by using microcavity and DFB structures, which are commonly adopted methods to enhance light amplification in specific wavelength. Both of them are the more widely used structures in inorganic and organic lasers. In this work, we employed nearly 100% reflection (at 450 nm) DBR and Al to act as reflected mirror inside the microcavity device. The function of microcavity has been examined to show the ability of device in tuning laser emission wavelength and overcoming the loss of organic-metal interface. DFB structure was used to demonstrate different laser emissions with respect to different grating periods. The finding clarifies the role of the structure in enhancement of light amplification leading to lower threshold, which was half of that of amplified spontaneous emission from single layer of PFO. As designed laser mode is also an important factor to get a high performance organic laser, those laser modes of structures have been designed and estimated by simulations and consistent with the experimental results. Color tunable light source has great potential for display, lighting and bio-imaging. Current broadband light sources, however, have their own limitations in beam divergence and device size. In this work, we demonstrated a spatially variant light source with tunable color emission property by using two cascaded organic thin films, which emit blue and green ASE respectively under optical pumping. By spatially selecting the overlapping of the directional ASE from the cascaded films, we show that the color of light emission can be continuously tuned from blue, white to green.

A pair of high-stability optical frequency references has been developed. The devices are based on room temperature Fabry-Perot cavities with mirrors spaced apart by a hollow single-crystal sapphire element. The sapphire element delivers mechanical sti ness that provides improved immunity to vibrational perturbations compared with the more common spacers made from ultra-low expansion glass. The system is housed in an vacuum chamber designed to provide isolation from environmental perturbations through the use of an active thermal control system, suspension legs and a unique beam alignment system. The dimensional stability of the Fabry-Perot was translated into a highly stable laser frequency by frequency locking a 1064nm Nd:YAG laser to the centre of a mode of the cavity. This frequency lock was implemented by the Pound-Drever-Hall scheme. By careful design, this control system was able to hold the frequency of the laser to within parts in 1016 of the frequency of the fundamental cavity mode. The minimum fractional frequency stability of the laser frequency was measured at 2.1x10[-]14 for integration times of 0.8 s, limited by the residual instability of the Fabry-Perot cavity. The experimental methods used to measure the performance of the system have also been considered in depth. For example, the most common way of characterizing the frequency stability of a frequency standard is the Allan variance. It is demonstrated that, without care, data taken with modern frequency counters can produce erroneous and distorted results when their output is supplied to this algorithm. The method to avoid or account for these errors is also presented. The Fabry-Perot cavity performance is limited on long timescales by residual temperature uctuations, which can be ameliorated in future by enhancing the design of the thermal control system. At short timescales, the system is limited by vibration-induced uctuations together with a white noise source, that is yet to be identi ed, but may relate to fundamental thermodynamic temperature uctuations of the sapphire spacer. This system was used to measure the stability of an optical signal synthesised from a cryogenic microwave sapphire oscillator using an wide-band optical frequency comb. This was the rst demonstration of a multiplication of an ultra-stable signal from the microwave frequency domain into the optical frequency domain, without loss of delity at the level of 2x10[-]14.

Thesis (Ph.D.)--University of Melbourne, School of Earth Sciences, 2007. / Typescript. Includes bibliographical references (leaves 211-240).

Thesis (Ph.D.)--University of Melbourne, School of Chemistry, 2007. / Typescript. Includes bibliographical references (leaves 103-109).

xviii, 213 p. / A print copy of this title is available through the UO Libraries under the call number: SCIENCE QC476.5 .F67 2006 / We investigate models describing two classes of microresonators: those having the shape of a dome, and those having an oval (deformed circle or sphere) shape. We examine the effects of dielectric interfaces in these structures. For the dome cavity, we derive efficient numerical methods for finding exact electromagnetic resonances. In the dome consisting of a concave conductor and a planar, dielectric Bragg mirror, we discover a phenomenon which we call paraxial mode mixing (PMM) or classical spin-orbit coupling. PMM is the sensitive selection of the true electromagnetic modes. The true modes are generally mixtures of pairs of vectorial Laguerre-Gauss modes. While each member of an LG pair possesses definite orbital angular momentum and spin (polarization), the mixed modes do not, and exhibit rich, non-uniform polarization patterns. The mixing is governed by an orthogonal transformation specified by the mixing angle (MA). The differences in reflection phases of a Bragg mirror at electric s and p polarization can be characterized in the paraxial regime by a wavelength-dependent quantity εs - εp. The MA is primarily determined by this quantity and varies with an apparent arctangent dependence, concomitant with an anticrossing of the maximally mixed modes. The MA is zero order in quantities that are small in the paraxial limit, suggesting an effective two-state degenerate perturbation theory. No known effective Hamiltonian and/or electromagnetic perturbation theory exists for this singular, vectorial, mixed boundary problem. We develop a preliminary formulation which partially reproduces the quantitative mixing behavior. Observation of PMM will require both small cavities and highly reflective mirrors. Uses include optical tweezers and classical and quantum information. For oval dielectric resonators, we develop reduced models for describing whispering gallery modes by utilizing sequential tunneling, the Goos-H¨anchen (GH) effect, and the generalized Born-Oppenheimer (adiabatic) approximation (BOA). While the GH effect is found to be incompatible with sequential tunneling, the BOA method is found to be a useful connection between ray optics and the exact wave solution. The GH effect is also shown to nicely explain a new class of stable V-shaped dome cavity modes. / Adviser: Dr. Jens Noeckel.

Standard optical microscopes cannot resolve images below 200 nm within the visible wavelengths due to optical diffraction limit. This Thesis reports an investigation into super-resolution imaging beyond the optical diffraction limit by microsphere optical nano-scopy (MONS) and submerged microsphere optical nano-scopy (SMON). The effect of microsphere size, material and the liquid type as well as light illumination conditions and focal plane positions on imaging resolution and magnification have been studied for imaging both biological (viruses and cells) and non-biological (Blu-ray disk patterns and nano-pores of anodised aluminium oxide) samples. In particular, sub-surface imaging of nano-structures (data-recorded Blu-ray) that cannot even be seen by a scanning electron microscope (SEM) has been demonstrated using the SMON technique. Adenoviruses of 75 nm in size have been observed with white light optical microscopy for the first time. High refractive index microsphere materials such as BaTiO3 (refractive index n = 1.9) and TiO2-BaO-ZnO (refractive index n = 2.2) were investigated for the first time for the imaging. The super-resolution imaging of sub-diffraction-limited objects is strongly influenced by the relationship between the far-field propagating wave and the near-field evanescent waves. The diffraction limit free evanescent waves are the key to achieving super-resolution imaging. This work shows that the MONS and SMON techniques can generate super-resolution through converting evanescent waves into propagating wave. The optical interactions with the microspheres were simulated using special software (DSIMie) and finite different in time domain numerical analysis software (CST Microwave Studio). The optical field structures are observed in the near-field of a microsphere. The photonic nanojets waist and the distance between single dielectric microsphere and maximum intensity position were calculated. The theoretical modelling was calculated for comparisons with experimental measurements in order to develop and discover super-resolution potential.

Nous nous sommes intéressés à la croissance et la caractérisation de nanofils de silicium (Si) et de germanium (Ge). Les nanofils ont été synthétisés par le mécanisme VLS (Vapeur Liquide Solide) dans un réacteur LPCVD (Low Pressure Chemical Vapor Deposition), en utilisant l'or (Au) comme catalyseur et le silane (SiH4) ou le germane (GeH4) comme gaz précurseur. Pour que ce procédé de croissance conduise à l'obtention de nanofils, le catalyseur Au doit être nano-structuré sous la forme de nanoparticules de diamètre si possible contrôlé. Ceci est fait dans cette étude par « démouillage » d'une couche continue déposée initialement par effet Joule sur le substrat choisi. L'épaisseur de cette couche continue initiale est un paramètre essentiel dans l'étude. Une partie préliminaire de ce travail a concerné l'étude de la façon dont se démouillage s'effectue, en fonction des divers paramètres. Nous avons ensuite effectué une étude exhaustive du rôle de tous les paramètres (nature du substrat, température, pression, épaisseur de la couche continue d'or, temps de croissance, durée et température de démouillage) qui contrôlent le procédé de croissance LPCVD sur les caractéristiques des nanofils de Ge notamment. Nous avons fait varier ces paramètres dans de larges fenêtres de valeurs afin de maîtriser et contrôler leur croissance. La caractérisation structurale des nanofils par microscopie électronique en transmission montre leur structure monocristalline avec une direction de croissance <111> pour les nanofils de Si et <110> pour les nanofils de Ge. Enfin, dans le cas des nanofils de Ge coniques isolés et déposés sur différents substrat, l'analyse micro-Raman nous a permis de mettre en évidence un phénomène de résonance optique à l'intérieur du nanofils et qui dépend fortement du diamètre local du nanofil. L'intensité Raman augmente avec la diminution du volume excité. Ces effets sont expliqués par les modes optiques apparaissant selon le diamètre local du nanofil, la longueur d'onde d'excitation et la nature du substrat utilisé. En plus, Le profil de la fréquence obtenu a montré qu'aucune anomalie particulière n'est observée. Ces profils obtenus en fonction du substrat et de la longueur d'onde utilisés sur différents nanofils montrent une faible variation de la fréquence. Le profil de la largeur à mi-hauteur est constant. Ces résultats montrent l'absence des effets de confinement de modes de phonons dans les nanofils individuels caractérisés. / This work deals with the growth and characterization of silicon (Si) and germanium (Ge) nanowires. The nanowires were synthesized by the growth mechanism VLS (Vapor Liquid Solid) in a LPCVD reactor (Low Pressure Chemical Vapor Deposition) using gold (Au) as the catalyst and silane (SiH4) and germane (GeH4) as precursor gas. In order to grow nanowires, the Au catalyst must be nano-structured in the form of nano-particles with controlled diameter if possible. This is done in this study by “dewetting” of a continuous layer evaporated on the chosen substrate. The thickness of this initial continuous layer is an essential parameter in the study. A preliminary part of this work deals with the problem of how the “dewetting” occurs, depending on various parameters (type of substrate, temperature, pressure, thickness of the continuous gold layer, growth duration and “dewetting” temperature) that control the LPCVD growth process. We varied these process parameters over wide ranges to determine how the influence the properties of Ge nanowires grown. The structural characterization of nanowires by transmission electron microscopy shows their single crystal structure with growth direction along <111> in the case of Si nanowires and along <110> for Ge nanowires. Finally, in the case of conical Ge nanowires isolated and deposited on different substrates, the micro-Raman analysis allowed us identifies an optical resonance phenomenon inside the nanowires which strongly depends on their local diameter. The Raman intensity increases with the decrease of volume excited. These effects are explained by the optical modes appearing according to the local diameter of the nanowire, the excitation wavelength and the nature of the substrate used. In addition, the Raman lines recorded along the same profiles did not show any spectral shift, reinforcing the idea that the behavior of their intensity has to be related to resonances associated with the development of local optical modes. These effects were observed to be dependent upon the type of substrate on which the isolated nanowires were transferred (dielectric versus metallic substrates). No effect of the confinement of phonon mode in our nanowires was observed.