The goal of the research reported in this thesis is to establish the feasibility of a novel optical architecture for an optical route & select circuit switch suitable for implementation as a photonic integrated circuit. The proposed architecture combines Optical Phased Array (OPA) switch elements implemented as multimode interference coupler based Generalised Mach-Zehnder Interferometers (GMZI) with a planar Lüneburg lens-based optical transpose interconnection network implemented using graded metamaterial waveguide slabs. The proposed switch is transparent to signal format and, in principle, can have zero excess insertion loss and scale to large port counts. These switches will enable the low-energy consumption high capacity communications network infrastructure needed to provide environmentally-friendly broadband access to all. The thesis first explains the importance of switch structures in optical communications networks and the difficulties of scaling to a large number of switch ports. The thesis then introduces the Talbot effect, i.e. the self-imaging of periodic field distributions in free space. It elaborates on a new approach to finding the phase relations between pairs of Talbot image planes at carefully selected positions. The free space Talbot effect is mapped to the waveguide Talbot effect which is fundamental to the operation of multimode interference couplers (MMI). Knowledge of the phase relation between the MMI ports is necessary to achieve correct operation of the GMZI OPA switch elements. An outline of the design procedures is given that can be applied to optimise the performance of MMI couplers and, as a consequence, the GMZI OPA switch elements. The Lüneburg Optical Transpose Interconnection System (LOTIS) is introduced as a potential solution to the problem of excessive insertion loss and cross-talk caused by the large number of crossovers in a switch fabric. Finally, the thesis explains how a Lüneburg lens may be implemented in a graded ‘metamaterial’, i.e. a composite material consisting of ‘atoms’ arranged on a regular lattice suspended in a host by nano-structuring of silicon waveguide slabs using a single etch-step. Furthermore, the propagation of light in graded almost-periodic structures is discussed. Detailed consideration is given to the calibration of the local homogenised effective index; in terms of the local parameters of the metamaterial microstructure in the plane and the corrections necessary to accommodate slab waveguide confinement in the normal to the plane. The concept and designs were verified by FDTD simulation. A 4×4 LOTIS structure showed correct routing of light with a low insertion loss of -0.25 dB and crosstalk of -24.12 dB. An -0.45 dB excess loss for 2D analysis and an -0.83 dB insertion excess loss for 3D analysis of two side by side metamaterial Lüneburg lenses with diameter of 15 μm was measured, which suggests that the metamaterial implementation produces minimal additional impairments to the switch.

Les automates cellulaires, composes d'un grand nombre de processeurs élémentaires, permettent un traitement rapide et efficace de certaines algorithmes. Le présent travail étudie la possibilité d'une implantation parallèle d'un tel automate sur un circuit intégré avec des entrées optiques en utilisant des photodiodes intégrées et un illuminateur de tableaux et des sorties optoélectroniques avec des modulateurs a puits quantiques multiples. Différents composants ont été étudiés et réalisés dans ce but: illuminateur de tableaux réalisé sur un hologramme en utilisant l'effet d'imagerie de talbot. Une amélioration des aberrations chromatiques est proposée en changeant les conditions d'enregistrement; circuit électronique intégrée VLSI contenant un seul processeur élémentaire avec des photodiodes intégrées pour les entrées optiques et les plots de sortie spéciaux pour les modulateurs; modulateurs opto-électroniques a puits quantiques multiples. Un montage expérimental a été réalisé en éclairant une photodiode avec une diode laser a 999 nm. L'estimation des performances de l'automate propose montre sa haute capacité de calcul et de connexion.

This thesis is an overview of the processes and procedures used in the production of my artistic practice. In my work, I explore notions such as the ambiguity of the photographic image, what constitutes an image or object as photographic, and the unexplored possibilities of the medium through surface and mark making. In addition, I draw inspiration from artists Wolfgang Tillmans, William Henry Fox Talbot, and Marco Breuer as entrance points to my conceptual interests. For viewers, my work generates an internal dialogue about the limits of the photographic medium.

Made available in DSpace on 2016-04-27T17:26:53Z (GMT). No. of bitstreams: 1 Paulo Eduardo Rodrigues Ruiz.pdf: 17241835 bytes, checksum: 3ae3cf02e74bd112c2c13464d3b713ec (MD5) Previous issue date: 2010-11-23 / The aim of this dissertation is to analyze the question of the photographic ambiguity in the 19th century from the theoretical assumption that photography was considered, in its origins, a kind of pencil of nature . This concept was developed by the English researcher and photographer William Henry Fox Talbot, in the work The Pencil of Nature, published between 1844 and 1846. Our discussion is based on the assumption that The Pencil of Nature already presented ambiguities and ambivalences typical of the photographic practice in the 19th century and, to an extent, until today, as regards the technical, scientific, commercial and artistic appeal of an industrial society. We draw examples from the photographic production at the time, using concepts developed by philosophers and theorists of photography such as Martin Heidegger, Walter Benjamin, Roland Barthes, Susan Sontag, Philippe Dubois, André Rouillé and Boris Kossoy, related to some basic notions about the photographic language: the question of technology and photographic verisimilitude, the shift in the perception of reality through photography and the presence of death in the photographic image / O objetivo deste trabalho é refletir a respeito da questão da ambiguidade fotográfica no século XIX a partir do pressuposto teórico de que a fotografia era considerada, em seus primórdios, uma espécie de lápis da natureza . Este conceito foi concebido pelo pesquisador e fotógrafo inglês William Henry Fox Talbot, na obra ThePencilofNature, publicada entre os anos de 1844 e 1846. O fio condutor de nossa discussão parte da hipótese de que ThePencilofNature já apresentava uma série de ambiguidades e ambivalências características da prática fotográfica do século XIX e, em parte, até os dias de hoje, em relação ao apelo técnico-científico, comercial e artístico de uma sociedade industrial. Para tal reflexão, utilizaremos alguns exemplos da produção fotográfica da época, fazendo uso de alguns conceitos de filósofos e de pensadores da fotografia tais como Martin Heidegger, Walter Benjamin, Roland Barthes, Susan Sontag, Philippe Dubois, André Rouillé e Boris Kossoy, relacionados a alguns preceitos básicos sobre a linguagem fotográfica: a questão da técnica e da verossimilhança fotográficas, a transformação da percepção do real por meio da fotografia e a presença da morte no registro fotográfico

La demande en constante progression de sources laser compactes et efficaces conduit à rechercher des architectures nouvelles pour accroître la puissance des diodes laser. La solution la plus prometteuse consiste à utiliser plusieurs lasers identiques de puissance modérée en parallèle. Pour conserver la qualité spatiale du faisceau, il est nécessaire d'induire une relation de phase constante entre les lasers. Nous présentons une étude théorique et expérimentale de la mise en phase passive d'une barrette de diodes laser de puissance. Pour cela, nous exploitons les propriétés de filtrage angulaire et spectral des réseaux de Bragg volumiques dans une cavité externe. Deux solutions ont été étudiées : la première exploite l'effet d'auto-imagerie Talbot et la seconde effectue un filtrage sélectif des composantes angulaires de l'émission de la barrette. Un modèle théorique permettant de déterminer le comportement modal de chacune de ces cavités a été réalisé. Dans le cas de la cavité Talbot, en collaboration avec l'Université de Nottingham, la cavité a également été modélisée en prenant en compte les propriétés internes des diodes laser. Expérimentalement, plusieurs architectures adaptées à des géométries de barrettes différentes ont été étudiées, qui ont toutes donné lieu à une émission cohérente. Nous montrons que l'utilisation d'un réseau de Bragg volumique intra-cavité permet à la fois d'améliorer la cohérence entre les lasers et de stabiliser le spectre d'émission. Enfin, nous présentons une solution originale utilisant des filtres de phase permettant de convertir le faisceau cohérent multilobe provenant de la cavité laser en un faisceau de profil gaussien.

Architect and soldier Sir J.J. Talbot Hobbs was born on 24 August 1864 in London. After migrating from England to Western Australia in the late 1880s, Hobbs designed many buildings that were constructed in Perth, Fremantle, and regional areas of the State. Although Talbot Hobbs has previously been recognised as a significant and influential contributor to architecture in Australia, his development as an architect has not been documented, nor has his design output undergone critical analysis. A number of problems confront attempts to interpret Hobbs' contribution to architecture. One is that a number of his most prominent building designs have been demolished. Another is that national recognition for his achievements as a First World War Army General have overshadowed his extraordinarily productive pre and post-war career as an architect. Military service was intrinsic to his character, and thus is woven in to this architectural biography. The thesis examines Hobbs' life and work, filling the gap in documented evidence of his contributions, and fitting it within the context of Australian architectural and social history. The main proposition to be tested is whether Hobbs' Australian architecture, of English derivation, combined with vast community service, warrants his recognition as an architect and citizen of national significance. Completely new important issues, information, discussion and facts that have resulted from the research for this thesis are: 1. Biographical knowledge about Hobbs' life – including his upbringing, education and training in England, and his fifty years of comprehensive work and community service in and for Australia; 2. The elucidation of the late nineteenth and early twentieth century architectural issues that were relevant to Hobbs and other architects in Western Australia; 3. Examination of the important works of Hobbs' architect predecessors and contemporaries in Perth, and the setting of his own work within this context; 4. Revelation of his primary and pivotal role in war memorial design and organisational work for the far-flung theatres of Australian Army conflicts and selected personal design works within Australia itself during 1919-38; and 5. A chronology and summary of Hobbs' life, with thorough documentation of his output as a sole practitioner in the period 1887-1904 by development of a detailed web-based database - an extremely valuable tool for future researchers.

Abstract The salt print is an important part of photography, both in its historic value and in the tonal range it can provide. This tonal range is greater than any other photographic printing process available to date attributed to the inherent masking ability of the metallic silver. However the intrinsic production problems have made it a 'forgotten' process. There are five key problems. 1. The difficulties in achieving the potential extensive tonal range. 2. The varying colour of the print. 3. Staining that appears in the print, during and after processing. 4. Instability and longevity of the salt print. 5. Contradictory and inaccurate information in material published on the salt print. Although the emphasis of the research is on exploring and controlling the colour and tonal range, the staining problems and stability of the print are also addressed. The materials used for contact negatives today vary in both capture and output, from analogue film processed in the traditional wet darkroom to a variety of transparent film printed from digital files. Inadequate density and tonal range can affect all types of negatives. To provide sufficient exposure time for the salt prints extended tonal range adjustments to the negative were necessary. These long exposures then converted sufficient silver salts to the image making metallic silver, utilising the intrinsic self-masking process. Ultimately this research has uncovered ways to control colour and tonal range and certain aesthetic qualities of the salt print, while simultaneously resolving some of the conflicts in published information. Accurate and consistent methods of processing eliminate staining, providing some stability to the print. The activities and steps carried out to make a salt print are manual; precise duplication is therefore almost unattainable. Nevertheless, although tests on a densitometer may display numeric differences, visual differences are barely noticeable.

This thesis considers new methods that exploit recent developments in computer technology to address three extant problems in the area of Finance and Econometrics. The problem of Asian option pricing has endured for the last two decades in spite of many attempts to find a robust solution across all parameter values. All recently proposed methods are shown to fail when computations are conducted using standard machine precision because as more and more accuracy is forced upon the problem, round-off error begins to propagate. Using recent methods from numerical analysis based on multi-precision arithmetic, we show using the Mathematica platform that all extant methods have efficacy when computations use sufficient arithmetic precision. This creates the proper framework to compare and contrast the methods based on criteria such as computational speed for a given accuracy. Numerical methods based on a deformation of the Bromwich contour in the Geman-Yor Laplace transform are found to perform best provided the normalized strike price is above a given threshold; otherwise methods based on Euler approximation are preferred. The same methods are applied in two other contexts: the simulation of stable distributions and the computation of unit root densities in Econometrics. The stable densities are all nested in a general function called a Fox H function. The same computational difficulties as above apply when using only double-precision arithmetic but are again solved using higher arithmetic precision. We also consider simulating the densities of infinitely divisible distributions associated with hyperbolic functions. Finally, our methods are applied to unit root densities. Focusing on the two fundamental densities, we show our methods perform favorably against the extant methods of Monte Carlo simulation, the Imhof algorithm and some analytical expressions derived principally by Abadir. Using Mathematica, the main two-dimensional Laplace transform in this context is reduced to a one-dimensional problem.

Cette thèse est consacrée à l'étude expérimentale d'atomes piégés<br />et refroidis dans plusieurs types de structures lumineuses. Nous avons utilisé pour caractériser ces milieux des techniques de temps de vol, d'imagerie directe du nuage atomique et de spectroscopie pompe-sonde, afin d'obtenir des informations sur la température et la diffusion spatiale des atomes ainsi que sur leur mouvement dans les puits de potentiel.<br /><br />Nous avons d'abord étudié la dynamique d'atomes de césium dans des<br />réseaux optiques tri-dimensionnels brillants en présence d'un champ<br />magnétique, et nous avons en particulier montré que les réseaux optiques fonctionnant en régime sautant donnent lieu à un refroidissement et un piégeage efficaces, et qu'un mécanisme de rétrécissement par le mouvement y conduit à des raies vibrationnelles étroites sur les spectres de transmission pompe-sonde. Avec des atomes de césium, nous avons également créé et<br />caractérisé un réseau optique tri-dimensionnel brillant obtenu avec<br />seulement deux faisceaux laser grâce à l'effet Talbot, puis un milieu aléatoire engendré à partir d'un champ de tavelures.<br /><br />Enfin, nous avons étudié un ``moteur brownien'' pour des atomes de $^(87)$Rb dans un réseau gris asymétrique. Les résultats de l'étude<br />expérimentale sont en bon accord qualitatif avec des simulations numériques Monte-Carlo semi-classiques.

The widespread adoption of photonic circuits requires the economics of volume manufacturing offered by integration technology. A Complementary Metal-Oxide Semiconductor compatible silicon material platform is particularly attractive because it leverages the huge investment that has been made in silicon electronics and its high index contrast enables tight confinement of light which decreases component footprint and energy consumption. Nevertheless, there remain challenges to the development of photonic integrated circuits. Although the density of integration is advancing steady and the integration of the principal components – waveguides, optical sources and amplifiers, modulators, and photodetectors – have all been demonstrated, the integration density is low and the device library far from complete. The integration density is low primarily because of the difficulty of confining light in structures small compared to the wavelength which measured in micrometers. The device library is incomplete because of the immaturity of hybridisation on silicon of other materials required by active devices such as III-V semiconductor alloys and ferroelectric oxides and the difficulty of controlling the coupling of light between disparate material platforms. Metamaterials are nanocomposite materials which have optical properties not readily found in Nature that are defined as much by their geometry as their constituent materials. This offers the prospect of the engineering of materials to achieve integrated components with enhanced functionality. Metamaterials are a class of photonic crystals includes subwavelength grating waveguides, which have already provided breakthroughs in component performance yet require a simpler fabrication process compatible with current minimum feature size limitations. The research reported in this PhD thesis advances our understanding of the structure-property relations of key planar light circuit components and the metamaterial engineering of these properties. The analysis and simulation of components featuring structures that are only just subwavelength is complicated and consumes large computer resources especially when a three dimensional analysis of components structured over a scale larger than the wavelength is desired. This obstructs the iterative design-simulate cycle. An abstraction is required that summarises the properties of the metamaterial pertinent to the larger scale while neglecting the microscopic detail. That abstraction is known as homogenisation. It is possible to extend homogenisation from the long-wavelength limit up to the Bragg resonance (band edge). It is found that a metamaterial waveguide is accurately modeled as a continuous medium waveguide provided proper account is taken of the emergent properties of the homogenised metamaterial. A homogenised subwavelength grating waveguide structure behaves as a strongly anisotropic and spatially dispersive material with a c-axis normal to the layers of a one dimensional multi-layer structure (Kronig-Penney) or along the axis of uniformity for a two dimensional photonic crystal in three dimensional structure. Issues with boundary effects in the near Bragg resonance subwavelength are avoided either by ensuring the averaging is over an extensive path parallel to boundary or the sharp boundary is removed by graded structures. A procedure is described that enables the local homogenised index of a graded structure to be determined. These finding are confirmed by simulations and experiments on test circuits composed of Mach-Zehnder interferometers and individual components composed of regular nanostructured waveguide segments with different lengths and widths; and graded adiabatic waveguide tapers. The test chip included Lüneburg micro-lenses, which have application to Fourier optics on a chip. The measured loss of each lens is 0.72 dB. Photonic integrated circuits featuring a network of waveguides, modulators and couplers are important to applications in RF photonics, optical communications and quantum optics. Modal phase error is one of the significant limitations to the scaling of multimode interference coupler port dimension. Multimode interference couplers rely on the Talbot effect and offer the best in-class performance. Anisotropy helps reduce the Talbot length but temporal and spatial dispersion is necessary to control the modal phase error and wavelength dependence of the Talbot length. The Talbot effect in a Kronig-Penny metamaterial is analysed. It is shown that the metamaterial may be engineered to provide a close approximation to the parabolic dispersion relation required by the Talbot effect for perfect imaging. These findings are then applied to the multimode region and access waveguide tapers of a multi-slotted waveguide multimode interference coupler with slots either in the transverse direction or longitudinal direction. A novel polarisation beam splitter exploiting the anisotropy provided by a longitudinally slotted structure is demonstrated by simulation. The thesis describes the design, verification by simulation and layout of a photonic integrated circuit containing metamaterial waveguide test structures. The test and measurement of the fabricated chip and the analysis of the data is described in detail. The experimental results show good agreement with the theory, with the expected errors due to fabrication process limitations. From the Scanning Electron Microscope images and the measurements, it is clear that at the boundary of the minimum feature size limit, the error increases but still the devices can function.