Neste trabalho desenvolvemos um novo método para análise biométrica do olho. Essa análise se compõe de medidas dos parâmetros biomecânicos, ou seja, espessura da córnea, distancia entre a córnea e o cristalino, espessura do cristalino, e distancia entre o cristalino e a retina. Este novo método funciona utilizando o princípio da interferometria com laser de baixa coerência. O conhecimento desses parâmetros e de suma importância para o fornecimento de dados necessários para o implante de lentes intra-oculares, em casos de catarata. Alem disso, eles permitem diagnosticar patologias clinicamente caracterizadas por suas alterações. O instrumento convencionalmente utilizado para essas medidas e o biômetro ultra-sônico. Embora esses biômetros sejam práticos e eficientes, a resolução por análise ultra-sônica esta limitada ao fato do tecido ocular não fornecer ecos satisfatórios em freqüências muito acima de 10 MHz. Uma limitação na resposta de freqüência determina uma subseqüente limitação na precisão de medida, já que esta será tanto maior quanta maior a freqüência. Uma variedade de técnicas diferentes tem sido experimentada nos últimos dez anos visando estabelecer um método mais preciso. Entretanto, várias das alternativas existentes têm sido rejeitadas devido à complexidade operacional e altos custos. A técnica interferométrica, entretanto, reúne alta resolução, simplicidade operacional e baixo custo. Isso pode ser constatado pelos resultados obtidos, os quais revela um enorme potencial aplicativo para futuros trabalhos de pesquisa ou mesmo de diagnose. / In this work we have developed a new method for biometric analysis of the eye. This analysis consists of measurements of biomechanical parameters, like thickness of the cornea, distance between the cornea and the crystalline lens, thickness of the crystalline lens and distance between the crystalline lens and the retina. In this new method we use the interferometric principle with a low coherence laser. The knowledge of these parameters is very important in order to supply the necessary data for the implant of intraocular lenes, in the cases of cataract. Besides of allow the diagnosis of the pathologies, which are characterized by their changes. The instrument used in the measurements is an ultrasonic biometer. However the resolution of this instrument is limited by the ocular tissue, which does not allow satisfactory echos in frequencies above 10 MHz. A variety of the techniques have been used in the last ten years in the order to establish a more accurate method. However most of the existing alternatives have been rejected due to operational complexity and high cost. The interferometric technique unites high resolution, operational simplicity and low cost. This can be concluded by the results obtained in this work, which demonstrate the great potentiality of the method for future in academic research or clinical diagnosis.

Tomografia por Coerência Óptica, ou simplesmente OCT (acrônimo do inglês: Optical Coherence Tomography), é uma técnica para geração de imagens de seções transversais de meios espalhadores ao comprimento de onda utilizado. A OCT é baseada em interferometria óptica e gera imagens comumente correlacionadas às imagens geradas exames histológicos com a vantagem de ser indolor, não invasiva e não utilizar radiação ionizante. Este estudo dividiu-se em dois objetivos distintos, um refere-se à aplicação de sinais interferométricos de autocorrelação para a formação de imagens de amostras com estruturas complexas. O segundo objetivo foi o estudo das estruturas denominadas de harmônicos e sua aplicação no aumento da resolução axial de um sistema OCT. Com relação à primeira parte, constatou-se que o sinal interferométrico de autocorrelação é muitas vezes ignorado ou descartado pela OCT tradicional. Análises mais profundas da teoria de interferometria, juntamente com alguns estudos anteriores, apontaram para a possibilidade de gerar imagens de maior complexidade morfológica utilizando o sinal de autocorrelação, com a vantagem de se utilizar um arranjo óptico mais simples e também possibilitar imagens estáticas de amostras em movimento axial. Para testar os benefícios e as limitações da técnica de autocorrelação (Au-OCT) foi montado em laboratório e foram realizadas imagens de amostras no repouso e em movimento e confrontadas com imagens geradas no sistema OCT convencional. O sistema de Au-OCT foi capaz de gerar imagens de estruturas diversas (dentes, filmes plásticos entre outros), e apesar de possuir uma qualidade de imagem inferior à OCT, ela apresentou vantagens quando a amostra sofre deslocamentos axiais. Já em relação as características harmônicas, que se apresentam em amostras de alta refletividade óptica como falsas estruturas em imagens OCT, todo um estudo para o entendimento do fenômeno foi desenvolvido. Demonstrou-se também a possibilidade de utilização dessas estruturas para aprimorar a resolução axial diferencial (entre estruturas da própria amostra) através de um estudo numérico e experimental. Para isso padrões dimensionais do tipo degrau foram mensurados e os resultados tratados de acordo com procedimentos metrológicos, mostrando que os harmônicos podem ser utilizados para promover o aumento de resolução axial de um fator de aproximadamente dois. Por fim uma análise crítica sobre os resultados e uma discussão sobre perspectivas dos temas abordados, foram realizada. / Optical Coherence Tomography also largely known as the acronym OCT, is a technique developed to generate transversal sections images of light scattering media. Based on optical interferometry, it provides images correlated to histological images with the advantages of being not invasive, painless besides and does not use ionizing radiation. This study was divided into two separate goals; one refers to the application of interferometric autocorrelation signals for forming images of samples with complex structures. The second objective was the study of structures called harmonics and its application in increasing the axial resolution of an OCT system. Regarding the first part, it was found that the interferometric autocorrelation signal is often ignored or discarded by traditional OCT. Further analysis of the theory of interferometry, along with some previous studies have pointed to the possibility of generating images of greater morphological complexity using the signal autocorrelation, with the advantage of using a simplest optical arrangement and also allow static images of samples in axial movement. To test the benefits and limitations of the autocorrelation technique (Au-OCT) a setup was assembled in and images of samples were performed at rest and in motion and compared with images generated in conventional OCT system. The system Au-OCT was able to generate images of several structures (teeth, plastic films etc.), and despite having a lower image quality to the OCT, it presented advantages when the sample undergoes axial motion. Regarding the harmonic characteristics that are present in samples of high optical reflectivity as false structures in OCT images, a whole study to the understanding of the phenomenon was developed. Also demonstrated the possibility of using these structures to enhance the differential axial resolution (structures between the sample itself) using a numerical and experimental study. Dimensional standards step height like were measured and results handled according to metrological procedures, showing that the harmonics can be used to promote the increase of axial resolution by a factor of about two. Finally a critical analysis of the results and a discussion of perspectives of the topics discussed were performed.

A Microscopia Holográfica Digital (MHD) é uma poderosa ferramenta para análise não destrutiva de superfícies e caracterização morfológica e estrutural de materiais. Várias técnicas microscópicas têm sido utilizadas com esses objetivos, mas, em todas elas, a visualização de campo completo não é permitida em uma única aquisição da informação do sistema analisado, além disso, a necessidade de uso de corantes, o processo de varredura, entre outros fatores, dificulta a aquisição das imagens. A Microscopia Holográfica Digital permite contornar essas dificuldades através de um método simples e rápido. Com uma modificação em seu arranjo original, é possível revelar as diferenças na absorção e nos índices de refração experimentados por um campo transmitido por um material anisotrópico. Este método, neste trabalho, foi nomeado como Microscopia Holográfica de Polarização, o qual permite medir as diferenças de fase e de intensidade relacionadas com a birrefringência e com o dicroísmo do material, respectivamente. Dessa forma, A MHD se mostra uma ferramenta promissora na análise de problemas em diversas áreas, pois possibilita, através de uma única captura, obter informações sobre as propriedades ópticas e estruturais dos sistemas de interesse. O objetivo desse trabalho foi, além do desenvolvimento instrumental, analisar variações nas propriedades ópticas e morfológicas de eritrócitos através da quantificação dos índices de refração e perfis topográficos destes quando submetidos aos principais agentes de fixação de amostras. Essas variações são determinantes na escolha do método de análise, já que estes podem alterar significativamente os resultados, assim como a sua interpretação. Também foi descrito um novo método, baseado na técnica holográfica, de análise do dicroísmo linear através de uma varredura executada sobre os padrões de difração das componentes ortogonais do campo transmitido pela amostra. A aplicação da MHD ao estudo de processos dinâmicos também foi realizada, utilizando células cardíacas vivas e proteínas em solução. Somados, estes resultados demonstraram a possibilidade de se utilizar as técnicas holográficas como métodos de estudo amplo de microssistemas biológicos. / The Digital Holographic Microscopy (DHM) is a powerful tool for nondestructive analysis of surfaces and for morphological and structural characterization of materials. Several microscopic techniques have been used with these purposes, but in all cases, the complete field reconstruction is not allowed in a single acquisition of information of the analyzed system, moreover, the requirements of staining and scanning procedures, among other factors, difficult the image acquisition. Digital Holographic Microscopy allows to overcome these difficulties through a simple and quick method. With a modification in its original setup, is possible to reveal the differences in absorption and refractive index experienced by a wavefield transmitted by an anisotropic material. This method, in this thesis, is named Polarization Holographic Microscopy, which allows to measure differences in phase and intensity related to the birefringence and the dichroism of the material, respectively. Thereby, the DHM is shown as a promising tool for the study of problems in several fields, because it allows, through a single capture, to obtain information related to optical and morphological properties of the systems of interest. The objective of this work was, besides instrumental development, to evaluate changes in optical and morphological properties of erythrocytes through quantification of their refractive index and topographic profiles when submitted to the main fixating agents. These changes are crucial once the method of analysis is chosen, as they can significantly alter the results, as well as their interpretation. A new method was also described based on the holographic technique, for analysis of linear dichroism, through scans performed on the diffraction patterns of the orthogonal components of the field transmitted by the sample. The application of the DHM to the study of dynamic processes was also performed, using live cardiac cells and proteins in solution. Together, these results demonstrate the possibility of using holographic techniques such as extensive methods for studying biological microsystems.

Over the last several years considerable efforts have been made to develop Bose-Einstein condensate (BEC) based devices for a number of applications including fundamental research, precision measurements, and navgation systems. These devices, capable of complex functionality, can be built from simpler components which is currently done in both optics and microelectronics. These components include cold atom equivalents of beamsplitters, mirrors, waveguides, diodes, and transistors. The operation of the individual components must be fully understood before they can be assembled into a more complex device. The primary goal of this dissertation is to present a theoretical analysis of these components. It begins with a theoretical analysis of several different types of cold-atom beamsplitters in the context of BEC interferometry. Next, the dynamics of an interferometer that uses optical pulses to control the dynamics of the BEC will be presented. Finally, a proposal for a BEC based component that has behavior that is similar to an electronic transistor is introduced.

In this thesis we present a theoretical analysis of the instability in a cold atom interferometer. Interferometers are often used to split a signal (e.g. optical beam, matter wave), where each part of the signal evolves separately, then the interferometer recombines the signal. Interference effects from the recombination can be used to extract information about the different environments the the split signal traversed. The interferometer considered here splits a matter wave, the wave function of a Bose-Einstein Condensate, by using a guiding potential and then recombines the matter wave. The recombination process is shown to be unstable and the nature of the instability is characterized.

Tomografia por Coerência Óptica, ou simplesmente OCT (acrônimo do inglês: Optical Coherence Tomography), é uma técnica para geração de imagens de seções transversais de meios espalhadores ao comprimento de onda utilizado. A OCT é baseada em interferometria óptica e gera imagens comumente correlacionadas às imagens geradas exames histológicos com a vantagem de ser indolor, não invasiva e não utilizar radiação ionizante. Este estudo dividiu-se em dois objetivos distintos, um refere-se à aplicação de sinais interferométricos de autocorrelação para a formação de imagens de amostras com estruturas complexas. O segundo objetivo foi o estudo das estruturas denominadas de harmônicos e sua aplicação no aumento da resolução axial de um sistema OCT. Com relação à primeira parte, constatou-se que o sinal interferométrico de autocorrelação é muitas vezes ignorado ou descartado pela OCT tradicional. Análises mais profundas da teoria de interferometria, juntamente com alguns estudos anteriores, apontaram para a possibilidade de gerar imagens de maior complexidade morfológica utilizando o sinal de autocorrelação, com a vantagem de se utilizar um arranjo óptico mais simples e também possibilitar imagens estáticas de amostras em movimento axial. Para testar os benefícios e as limitações da técnica de autocorrelação (Au-OCT) foi montado em laboratório e foram realizadas imagens de amostras no repouso e em movimento e confrontadas com imagens geradas no sistema OCT convencional. O sistema de Au-OCT foi capaz de gerar imagens de estruturas diversas (dentes, filmes plásticos entre outros), e apesar de possuir uma qualidade de imagem inferior à OCT, ela apresentou vantagens quando a amostra sofre deslocamentos axiais. Já em relação as características harmônicas, que se apresentam em amostras de alta refletividade óptica como falsas estruturas em imagens OCT, todo um estudo para o entendimento do fenômeno foi desenvolvido. Demonstrou-se também a possibilidade de utilização dessas estruturas para aprimorar a resolução axial diferencial (entre estruturas da própria amostra) através de um estudo numérico e experimental. Para isso padrões dimensionais do tipo degrau foram mensurados e os resultados tratados de acordo com procedimentos metrológicos, mostrando que os harmônicos podem ser utilizados para promover o aumento de resolução axial de um fator de aproximadamente dois. Por fim uma análise crítica sobre os resultados e uma discussão sobre perspectivas dos temas abordados, foram realizada. / Optical Coherence Tomography also largely known as the acronym OCT, is a technique developed to generate transversal sections images of light scattering media. Based on optical interferometry, it provides images correlated to histological images with the advantages of being not invasive, painless besides and does not use ionizing radiation. This study was divided into two separate goals; one refers to the application of interferometric autocorrelation signals for forming images of samples with complex structures. The second objective was the study of structures called harmonics and its application in increasing the axial resolution of an OCT system. Regarding the first part, it was found that the interferometric autocorrelation signal is often ignored or discarded by traditional OCT. Further analysis of the theory of interferometry, along with some previous studies have pointed to the possibility of generating images of greater morphological complexity using the signal autocorrelation, with the advantage of using a simplest optical arrangement and also allow static images of samples in axial movement. To test the benefits and limitations of the autocorrelation technique (Au-OCT) a setup was assembled in and images of samples were performed at rest and in motion and compared with images generated in conventional OCT system. The system Au-OCT was able to generate images of several structures (teeth, plastic films etc.), and despite having a lower image quality to the OCT, it presented advantages when the sample undergoes axial motion. Regarding the harmonic characteristics that are present in samples of high optical reflectivity as false structures in OCT images, a whole study to the understanding of the phenomenon was developed. Also demonstrated the possibility of using these structures to enhance the differential axial resolution (structures between the sample itself) using a numerical and experimental study. Dimensional standards step height like were measured and results handled according to metrological procedures, showing that the harmonics can be used to promote the increase of axial resolution by a factor of about two. Finally a critical analysis of the results and a discussion of perspectives of the topics discussed were performed.

As the number of known exoplanetary systems has grown, it has become increasing apparent that our current understanding of planet formation is insufficient to explain the broad but distinct distributions of planets and planetary systems we observe. In particular, constructing a coherent model of planetary formation and migration within a circumstellar disc which is capable of producing both hot Jupiters or Solar System-like planetary system is high challenging. Resolved observations of where planets form and how they influence their parent discs provides essential information for tackling this important question. A promising technique for detecting close-in companions is Sparse Aperture Masking (SAM). The technique uses a mask to transform a single aperture telescope into a compact interferometric array capable of reliably detecting point sources at the diffraction limit or closer to a bright star with superior contrasts than extreme AO systems at the cost of smaller fields of view. Applying image reconstruction techniques to the interferometric information allows an observer to recover detailed structure in the circumstellar material. In this thesis I present work on the interpretation of SAM interferometry data on protoplanetary discs through the simulation of a number of scenarios expected to be commonly seen, and the application of this technique to a number of objects. Analysing data taken as part of a SAM survey of transitional and pre-transitional discs using the Keck-II/NIRC2 instrument, I detected three companion candidates within the discs of DM\,Tau, LkH\alpha\,330, and TW\,Hya, and resolved a gap in the disc around FP\,Tau as indicated by flux from the disc rim. The location of all three of the companions detected as part of the survey are positioned in interesting regions of their parent discs. The candidate, LkH\alpha\,330\,b is a potentially cavity opening companion due to its close radial proximity to the inner rim of the outer disc. DM\,Tau\,b is located immediately outside of a ring of dusty material largely responsible for the NIR comment of the disc SED, similar to TW\,Hya\,b located in a shallow gap in the dust disc outside another ring of over-dense dusty material which bounds a deep but narrow gap. Both of these companion candidates maybe migrating cores which are feeding from the enriched ring of material. I conducted a more extensive study of the pre-transitional disc, V1247\,Ori, covering three epochs and the H-, K- and L-wavebands. Complementary observations with VLT/SPHERE in H\alpha and continuum plus SMA observations in CO (2-1) and continuum were performed. The orientation and geometry of the outer disc was recovered with the SMA data and determine the direction of rotation. We image the inner rim of the outer disc in L-band SAM data, recovering the rim in all three epochs. Combining all three data sets together we form a detailed image of the rim. In H- and K-band SAM data we observe the motion of a close-in companion candidate. This motion was found to be too large to be adequately explained through a near-circular Keplerian orbit within the plane of the disc around the central star. Hence an alternate hypothesis had to be developed. I postulated that the fitted position of the companion maybe influenced by the emission from the disc rim seen in the L-band SAM data. I constructed a suite of model SAM data sets of a companion and a disc rim and found that under the right conditions the fitted separation of a companion will be larger than the true separation. Under these conditions we find the motion of the companion candidate to be consistent with a near-circular Keplerian orbit within the plane of the disc at a semi-major axis of \sim6\,au. The H\alpha data lack the necessary resolution to confirm the companion as an accreting body, but through the high contrast sensitivities enabled by the state of the art SPHERE instrument I was able to rule out any other accreting body within the gap, unless deeply embedded by the sparse population of MIR emitting dust grains previously inferred to reside within the gap. Through the combination of SAM and SMA data we constrain the 3-D orientation of the disc, and through multi-wavelength SAM observation identify a close-in companion potentially responsible for the gap clearing and asymmetric arm structures seen in previous observations of this target. During my PhD I have contributed to the field of planet formation through the identification of four new candidate protoplanets observed in the discs of pre-main sequence stars. To do so I have quantified the confidence levels of companion fits to SAM data sets and formed synthetic data from models of asymmetric structures seen in these discs. I have described for the first time the effects of extended sources of emission on the fitted results of companion searches within interferometric data sets. I have combined SAM data sets from two separate telescopes with different apertures and masks to produce reconstructed image of an illuminated disc rim with superior uv-coverage. I have used the expertise I have developed in this field to contribute to a number of other studies, including the study of the young star TYC\,8241\,2652\,1, resulting in the rejection of a sub-stellar companion as the cause of the rapid dispersal of the star`s disc. The companion candidates I have identified here should be followed up to confirm their presence and nature as accreting protoplanets. Objects such as these will provide the opportunity for more detailed study of the process of planet formation in the near future with the next generation of instruments in the JWST and E-ELT.

Optical feedback interferometry is a sensing technique with relative recent implementation for the interrogation of fluidic systems. The sensing principle is based on the perturbation of the laser emission parameters induced by the reinjection in the laser cavity of light back-scattered from a distant target. The technique allows for the development of compact and noninvasive sensors that measure various parameters related to the motion of moving targets. In particular, optical feedback interferometers take advantage of the Doppler effect to measure the velocity of tracers in flowing liquids. These important features of the optical feedback interferometry technique make it wellsuited for a variety of applications in chemical engineering and biomedical fields, where accurate monitoring of the flows is needed. This thesis presents the implementation of optical feedback interferometry based sensors in multiple fluidic systems where local velocity or flow rate are directly measured. We present an application-centered study of the optical feedback sensing technique used for flow measurement at the microscale with focus on the reliability of the signal processing methods for flows in the single and the multiple scattering regimes. Further, we present experimental results of ex vivo measurements where the optical feedback sensor is proposed as an alternative system for myography. In addition we present a real-time implementation for the assessment of non-steady flows in a millifluidic configuration. A semi-automatized system for single particle detection in a microchannel is proposed and demonstrated. Finally, an optical feedback based laser sensor is implemented for the characterization of the interactions between two immiscible liquid-liquid flowing at the microscale, and the measurement is compared to a theoretical model developed to describe the hydrodynamics of both fluids in a chemical microreactor. The present manuscript describes an important contribution to the implementation of optical feedback sensors for fluidic and microfluidic applications. It also presents remarkable experimental results that open new horizons to the optical feedback interferometry.

Bibliography : p.221-227. / xxiii, 227 p. : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1994

Be stars are rapidly rotating B-type stars that eject large amounts of material into a circumstellar disk. Evidence of the presence of a disk is found through hydrogen emission lines in their spectra, IR excess flux, and linear intrinsic polarization. In this dissertation, we report the first simultaneous interferometric and spectroscopic observations of circumstellar disks around 24 bright Be stars made using the techniques of long baseline interferometry and moderate resolution spectroscopy in the near infrared. The goal of the project is to characterize the fundamental geometrical and physical properties of the emitting regions that are responsible for the IR flux excesses detected in the K-band in our sample stars. This observational work has been conducted with both the Center for High Angular Resolution Astronomy (CHARA) Array at Mount Wilson Observatory, and the Mimir spectrograph at Lowell Observatory. The visibility measurements were interpreted with different geometrical and physical disk models in order to determine the spatial extension of the disk, the inclination angle, the position angle, and the density profile of the disk. We find that the spatial extension of the circumstellar disk in the K-band is only about a few stellar radii, and that the density structure of the disk is consistent with a radially decreasing function with a density exponent that ranges between 2.5 and 3.5. The resulting disk densities are in a good agreement with those derived from the Infrared Astronomical Satellite (IRAS) measurements, and the resulting disk geometries are consistent with previous polarimetric measurements. We find that the K-band sizes of the emitting regions in the disk are smaller by a factor of two than the Hα sizes, and we show that this is due to the lower opacity of the continuum in the disk. By combining recent measurements of the projected rotational velocities with the disk inclination angles derived from interferometry, we were able to estimate the actual equatorial linear rotational velocities of the Be stars in our sample. The obtained linear rotational velocities indicate that Be stars are rapid rotators with an equatorial velocity that is about 0.7 - 0.9 of their critical velocities.