Coherent X-ray diffraction and X-ray Intensity Fluctuation Spectroscopy (XIFS) are ideal methods and techniques to perform measurements on the dynamics of fluctuations in condensed matter materials. To investigate more systems and faster fluctuations by being able to tune the coherence length, we use a zone plate to change the coherence length and beam size but keep most of the intensity. Using the zone plate, experiments were carried out to measure the properties of the focused beam. We applied a formalism to calculate the effect of optics on coherence. We tested our results by doing measurement at Advanced Photon Source. We measured the focal properties of the zone plate, speckle sizes and contrast, obtained by using coherent X-ray diffraction from an disordered Fe3Al crystals. Our theoretical calculations are compared with the experimental results.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [197]-201).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 140-147).

Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Janata, Jiri; Committee Member: Lyon, Andrew; Committee Member: Weissburg, Marc.

A particle counting instrument, the Coherent Optical Particle Spectrometer (COPS) has been developed for measuring particles in aerosol systems. It optically counts and sizes single particles one at a time as they pass through an optically defined inspection region so particle size distributions can be directly measured. COPS uses the coherent nature of light available in a laser beam to measure the phase shift in the scattered light, which is fundamentally different from previous intensity based techniques. The Van-Cittert-Zernike theorem shows that scattered light from small particles will be coherent if viewed upon at the focal point of a gathering lens. Optical homodyne detection can then be used to measure the extent of the phase shift due to the particle. Scattering mechanisms can relate the phase shift to particle diameter so particle size can be determined. An optical inspection region is given by the resolution limited blur spot diameter and depth of focus of the gathering lens. Particles scattering outside this zone will not contribute to measured phase signals. Calculations show that COPS can count in concentrations of 10('9) particles per cubic centimeter with 5% coincidence error. Mie scattering calculations, coupled with homodyne theory, predict a minimum detectable particle diameter ranging from 0.03 to 0.3 micrometers, depending on optical configuration. Theory shows that small, strongly absorbing particles impart a much larger phase shift than refractive particles so a lower detection limit is predicted for particles such as soot and silicon. Particles above one micrometer show classic resonance typical of Mie calculations. An experimental COPS system verified the predicted results from the model. Resolution of particle size ranged from 25 to 60 percent of particle diameter. Preliminary experiments showed that COPS has in situ sampling possibilities and will work for liquid systems as well. Coherent detection of scattered light shows promise for in situ measurement of submicrometer aerosols in high particle laden streams with maximum sensitivity for strongly absorbing particles.

An electrochemical sensor array can provide information about the spatial and temporal distribution of chemicals in liquid turbulent plumes. Planar laser induced fluorescence (PLIF) and amperometric sensor arrays were used to record signals from modulated chemical plumes released into a recirculating aquatic flume. Coherence analysis was applied to extract the frequency components contained in the sensor response. Effects due to release distance, modulation frequency, and array orientation were investigated. This study has demonstrated that frequency encoded information can be extracted from a turbulent chemical plume using an array of amperometric sensors with optimized three-dimensional geometry and tuning.

This thesis is concerned with exploiting the native optical coherence tomography (OCT) contrast mechanism in new ways and with a new contrast mechanism, in both cases to enhance the information content of the tomographic image. Through experiments in microsphere solutions, we show that static speckle contains information about local particle density when the effective number of scatterers in the OCT resolution volume is less than about five. This potentially provides contrast enhancement in OCT images based on local scatterer density, and we discuss the experimental conditions suited to utilising this in biological tissue. We also describe the corrupting effects of multiple scattering, a ubiquitous phenomenon in OCT, on the information content of the static speckle. Consequently, we detail the development of polarisation-based metrics for characterising multiple scattering in OCT images of solid biological tissues. We exploit a detection scheme used for polarisation-sensitive contrast for a new purpose. We present experiments demonstrating the behaviour of these metrics in liquid phantoms, and in biological tissues, ranging from homogeneous non-birefringent to highly heterogeneous and birefringent samples. We discuss the conditions under which these metrics could be used to characterise the relative contribution of single and multiple scattering and, thus, aid in the study of penetration depth limits in OCT. We present a study of a new contrast mechanism - dynamic elastography which seeks to determine the dynamic mechanical properties of tissues. We present a framework for describing the OCT signal in samples undergoing vibrations, and perform experiments at vibration frequencies in the order of tens to hundreds of Hertz, to confirm the theory, and demonstrate the modes of measurement possible with this technique. These modes of measurement, including acoustic amplitude-sweep and frequency-sweep, could provide new information about the local mechanical properties of a sample. We describe a technological advancement enabling, in principle, measurements of local tissue refractive index contrast much deeper within a sample, than is possible with conventional OCT imaging. The design is based on measurement of the optical path length through tissue filling a fixed-width channel situated at the tip of a needle. The needle design and calibration is presented, as well as measurements of scattering phantoms and various biological tissues. This design potentially enables the use of refractive index-based contrast enhancement in the guidance of breast biopsy procedures.

Orientador: João Marcos Travassos Romano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-17T02:34:02Z (GMT). No. of bitstreams: 1 Rosa_EduardodeSouza_M.pdf: 927396 bytes, checksum: 97e57986c5309fbfd62a2edb8c63a482 (MD5) Previous issue date: 2010 / Resumo: A multiplexação de polarização é uma técnica promissora que permite dobrar a capacidade de transmissão das próximas gerações de sistemas de comunicações ópticas operando a 40 Gb/s. Tais sistemas são dependentes de processamento digital de sinais, tanto para efetuar a separação dos sinais multiplexados em polarização, quanto para combater degradações impostas pelo canal óptico. Em geral, técnicas não supervisionadas como o algoritmo do módulo constante (CMA - Constant Modulus Algorithm) multiusuário são utilizadas para realizar a separação e a equalização simultaneamente. No entanto, este método apresenta algumas desvantagens, em especial a possibilidade de perda de um dos sinais transmitidos quando o sistema apresenta perda dependente de polarização. Este trabalho propõe uma nova estrutura de demultiplexação usando uma técnica de separação conhecida como análise de componentes independentes em conjunto com um equalizador adaptado pelo algoritmo do módulo constante. A técnica proposta é avaliada por meio de simulações, confirmando-se um bom desempenho diante das principais distorções lineares presentes em sistemas de comunicação óptica e verificando-se uma maior robustez em termos de perda dependente de polarização / Abstract: Polarization multiplexing is a promising technique, able to double the capacity of next generation optical communication systems working at 40 Gb/s. Such systems are dependent of digital signal processing, both to separate the signals in multiplexed polarization, and to combat impairments imposed by optical channel. In general, unsupervised techniques such as multiuser CMA (Constant Modulus Algorithm) are used to perform the separation and equalization simultaneously. However, this method has some drawbacks, in particular the possibility of losing one of the signals when the system has polarization dependent loss. This work proposes a new structure for demultiplexing employing a separation technique known as independent component analysis in conjunction with an equalizer adapted by the Constant modulus algorithm. The proposed technique is evaluated through simulations, confirming the good performance in front of the main linear distortions present in optical communication systems and being more robust in terms of polarization dependent loss / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica