Thesis (M.S.)--Ohio University, June, 1989. / Title from PDF t.p.

Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 197-201). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948024.

Thesis (Ph. D.)--Texas A & M University, 1993. / Vita. Includes bibliographical references (p. 204-208).

[pt] O modelamento de superfícies refletoras embarcadas em satélites tem se apresentado como uma alternativa eficiente à síntese de conjuntos de alimentadores. Existem várias técnicas disponíveis para a determinação do formato adequado para esta superfície, baseados em aproximações da ótica geométrica ou da ótica física. Neste trabalho, estudamos a aplicação da técnica das Projeções Sucessivas, um método interativo genérico, à síntese de superfície refletora e à síntese da distribuição de fase sobre a abertura. Este método é baseado nas aproximações da Ótica Física, o que garante uma boa precisão. Entre suas principais vantagens, estão a sua simplicidade e a sua eficiência computacional. / [en] The shaping of reflector surfaces for satellites hás been considered na efficient alternative to the available for the determination of the optimum shape for this surface, base don Geometrical Optics or Physical Optics approximations. This work investigates the application of the Technique of Sucessive Projections, a generic interative method, to the synthesis of a single reflector antenna and to the phase distribution on the aperture. This method is based on Physical Optics Techniques, which guarantees a good precision. Among its main advantages are its simplicity and its computational.

The capability of light goes well beyond illumination, yet it is so underused in our lives because the control of light still largely relies on clumsy bulk lenses. Less than 10 years ago, a type of revolutionary devices made of nanometer scale optical elements – metasurfaces – was invented to control the light propagation and its energy dissipation with arbitrary degree of freedom, at unprecedentedly small volumes (although some would argue that the advent of metasurfaces came in the 1990s). Vast diversity of new discoveries has since been made possible, and many more existing applications have seen significant performance enhancement with the aid of metasurfaces.<div><br><div> <div>In the scope of this work, I explore the use of a variety of metasurfaces to address several existing real-world challenges: sensing, optical heating, and data storage. Among these, three metasurfaces involve the world’s first two-dimensional material, graphene. I first investigate the graphene plasmonic resonator, which have been shown to be extremely sensitive single-molecule sensors. Graphene also has many intriguing properties in photodetection applications, such as lightweight, ultra-wide detection band, and ultrafast response speed. I have used two different metasurfaces to enhance the intrinsically low responsivity (sensitivity) of graphene photodetectors. Amidst the discussion of graphene photodetectors, I show the characterization result of plasmonic heating of metasurfaces, an essential process of the graphene photo-responsivity enhancement. Lastly, I present a multi-functional metasurface which can be used in optical steganography, encryption, and data storage. The proposed metasurface is compatible with large scale parallel readout, which outperforms current Blu-ray technology in both storage capacity and readout speed</div></div></div>

<div>In the 1970's, Arthur Ashkin developed a remarkable system called the ``optical tweezer'' which utilizes the radiation pressure of light to manipulate particles. Because of its non-invasive nature and controllability, optical tweezers have been widely adopted in biology, chemistry and physics. In this dissertation, two applications related to optical tweezers will be discussed. The first application is about the demonstration of multiple feedback controlled optical tweezers which let us conduct novel experiments which have not been performed before. For the second application, levitation of a silica nanodumbbell and cooling its motion in five degrees of freedom is executed.</div><div><br></div><div>To be more specific, the first chapter of the thesis focuses on an experiment using the feedback controlled optical tweezers in water. A well-known thought experiment called ``Feynman's ratchet and pawl'' is experimentally demonstrated. Feynman’s ratchet is a microscopic heat engine which can rectify the random thermal fluctuation of molecules to harness useful work. After Feynman proposed this system in the 1960’s, it has drawn a lot of interest. In this dissertation, we demonstrate a solvable model of Feynman’s ratchet using a silica nanoparticle inside a feedback controlled one dimensional optical trap. The idea and techniques to realize two separate thermal reservoirs and to keep them in contact with the ratchet is discussed in detail. Also, both experiment and simulation about the characteristics of our system as a heat engine are fully explored.</div><div><br></div><div>In the latter part of the dissertation, trapping silica nanodumbbell in vacuum and cooling its motion in five degrees of freedom is discussed. A levitated nanoparticle in vacuum is an extraordinary optomechanical system with an exceptionally high mechanical quality factor. Therefore, levitated particles are often utilized as a sensor in various research. Different from a levitated single nanosphere, which is only sensitive to force, a levitated nanodumbbell is sensitive to both force and torque. This is due to the asymmetry of the particle resulting it to have three rotational degrees of freedoms as well as three translational degrees of freedoms. In this dissertation, creating and levitating a silica nanodumbbell will be demonstrated. Active feedback cooling also known as cold damping will be employed to stabilize and cool the two torsional degrees of freedom of the particle along with the three center of mass DOF in vacuum. Additionally, both computational and experimental analysis is conducted on a levitated nanodumbbell which we call rotation-coupled torsional motion. The complex torsional motion can be fully explained with the effects of both thermal nonlinearity and rotational coupling. The new findings and knowledge of a levitated non-spherical particles leads us one step further towards levitated optomechanics with more complex particles.</div>

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No description available.

O Estudo de Materiais Fotorrefrativos e suas Aplicações no Processamento Óptico Holográfico de Informação vêm sendo feitos por diversos Grupos de Pesquisas em vários laboratórios devido aos bons resultados obtidos com esses meios em diversas áreas. Entre outros efeitos foto-induzidos o processo que possibilita essas aplicações é o efeito fotorrefrativo, um fenômeno onde o registro holográfico no meio fotorrefrativo ocorre pela modulação do índice de refração de acordo com a distribuição espacial da intensidade da luz incidente, devido a uma redistribuição foto-induzida de cargas espaciais, e conseqüente, geração de um campo espaço-carga no meio. Neste trabalho, estuda-se a propagação e acoplamento de ondas eletromagnéticas em monocristais elétro-ópticos paraelétricos da Família das Silenitas \'BI IND. 12\'\'SI\'\'O IND. 20\' (BSO) e \'BI IND. 12\'\'TI\'\'O IND. 20\' (BTO) e nos ferroelétricos \'LI\'\'NB\'\'O IND. 3\' puros e dopados. O propósito de estudar esses materiais é caracterizá-los e, principalmente, otimizá-los para aplicação no processamento óptico e holográfico de informação. Utiliza-se técnicas de caracterização de redes holográficas fotorrefrativas e de lentes foto-induzidas para determinação de figuras de mérito e parâmetros fotorrefrativos e termo-ópticos nestes meios fotorrefrativos. Propõe-se também algumas aplicações no processamento óptico e holográfico de informação, nas áreas de pesquisa básica, tecnológicas e biomédicas, que vêm despertando grande interesse nos últimos anos, como holografia em tempo real com mapeamento de fase, interterometria speckle em tempo real e registro não-holográfico no processo de conversão incoerente-incoerente; entre outras no processamento óptico e holográfico de dados. / The Study of Photorefractive Materials and their Applications in Optical and Holographical Information Processing come being made for diverse Groups of Research in some laboratories due to the good results in many areas. Among other photo-induced effects, the process that allows these applications is the photorefractive effect, a phenomenon where the holographic recording in photorefractive medium occurs by means of the refractive index modulation due to the space distribution of the light intensity, producing a space-charge photo-induced redistribution, and consequently, the generation of a space-charge field governed by an electro-optic medium. In this work, we study the propagation and coupling of electromagnetic waves in electro-optic monocrystals of the sillemite family Bi12SiO20 (BSO) and Bi12TiO20 (BTO) and in the pure and dop-ed LiNbO3 crystals. The purpose to study these materials is to characterize them and, mainly, to optimize the conditions of their application in the optical and holographical information processing. We use photorefractive holographic gratings and photo-induced lens techniques for determination of figures of merit and photorefractive and thermo-optic parameters in these photorefractive materials. We also consider some applications in the optical and holographical information processing in the research basic, technological and biomedical areas, that come waken great interest in the last years, as phase- shifting real-time holography, real-time speckle interferometry and non-holographic recording with incoherent-incoherent conversion process; among others in the optic and holographic data processing.

<p>Wave scattering is the phenomenon in which a wave field interacts with physical objects. An incoming wave is scattered at the surface of the object and a scattered wave is produced. Common practical cases are acoustic, electromagnetic and elastic wave scattering. The numerical simulation of the scattering process is important, for example, in noise control, antenna design, prediction of radar cross sections and nondestructive testing.</p><p>Important classes of numerical methods for accurate simulation of scattering are based on integral representations of the wave fields and theses representations require the knowledge of potentials on the surfaces of the scattering objects. The potential is typically computed by a numerical approximation of an integral equation that is defined on the surface. We first develop such numerical methods in time domain for the scalar wave equation. The efficiency of the techniques are improved by analytic quadrature and in some cases by local approximation of the potential.</p><p>Most scattering simulations are done for harmonic or single frequency waves. In the electromagnetic case the corresponding integral equation method is called the method of moments. This numerical approximation is computationally very costly for high frequency waves. A simplification is suggested by physical optics, which directly gives an approximation of the potential without the solution of an integral equation. Physical optics is however only accurate for very high frequencies.</p><p>In this thesis we improve the accuracy in the physical optics approximation of scalar waves by basing the computation of the potential on the theory of radiation boundary conditions. This theory describes the local coupling of derivatives in the wave field and if it is applied at the surface of the scattering object it generates an expression for the unknown potential. The full wave field is then computed as for other integral equation methods.</p><p>The new numerical techniques are analyzed mathematically and their efficiency is established in a sequence of numerical experiments. The new on surface radiation conditions give, for example, substantial improvement in the estimation of the scattered waves in the acoustic case. This numerical experiment corresponds to radar cross-section estimation in the electromagnetic case.</p>