Orientador: Luís Eduardo Evangelista de Araujo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-29T14:34:13Z (GMT). No. of bitstreams: 1 FernandezApolinario_Ulices_D.pdf: 32632596 bytes, checksum: 913293ad92a80bba8b449b4814411610 (MD5) Previous issue date: 2015 / Resumo: Nesta tese, propomos, descrevemos e desenvolvemos um novo mecanismo de clonagem de imagens ópticas baseado no efeito atômico coerente da absorção induzida eletromagneticamente ("EIA"). Estudamos experimentalmente a transferência de uma imagem impressa em um feixe forte de acoplamento para um feixe fraco de prova ressonante em um sistema atômico de rubídio de quatro níveis do tipo N degenerado. Nos experimentos, uma imagem bidimensional correspondente a um padrão de linhas horizontais é aplicada ao feixe de acoplamento e transferida para um feixe de prova, de mesma frequência mas polarização ortogonal ao laser de acoplamento. A clonagem de imagem é estudada em função da potência, dessintonia e grau de coerência espacial do feixe de acoplamento. Nós mostramos experimentalmente que o feixe de prova clonado que carrega a imagem é transmitido sem a difração usual. Apresentamos um modelo teórico, para o caso de um feixe de acoplamento espacialmente coerente, que prevê que as características transversais do feixe de acoplamento são transferidas para o feixe de prova de maneira eficiente, apesar da imagem de controle sofrer distorções devido a difração durante a propagação. De fato, as imagens clonadas podem ser muito melhores do que as imagens de acoplamento originais, com estruturas reduzidas em tamanho por aproximadamente um fator de 2. Experimentalmente, verificamos que quanto menor o grau de coerência da luz, melhor é a imagem clonada quando comparada com a imagem de acoplamento a uma mesma distância de propagação. Uma comparação com outras técnicas de clonagem estudadas na literatura, com luz espacialmente coerente, mostra que o nosso mecanismo apresenta um desempenho similar a elas, com uma transmissão máxima da imagem clonada pelo vapor atômico de aproximadamente 10% / Abstract: In this thesis, we propose, describe and develop a new optical imaging cloning mechanism based on the coherent atomic effect of electromagnetically induced absorption ("EIA"). We experimentally study the transfer of an image imprinted onto a strong coupling beam to a resonant weak probe beam in a rubidium atomic system in a degenerate four-level N configuration. In the experiments, a two-dimensional image corresponding to a pattern of horizontal lines is imprinted onto the coupling beam and transferred to a probe beam of the same frequency, but with orthogonal polarization to the coupling laser. Image cloning is studied as a function of power, detuning and the degree of spatial coherence of the coupling beam. We show experimentally that the cloned probe beam carrying the image is transmitted without the usual diffraction. We present a theoretical model, for the case of a fully spatially-coherent coupling beam, that predicts that the transverse characteristics of the coupling beam are efficiently transferred to the probe beam, in spite of distortions of the control image due to diffraction during propagation. Indeed, the cloned images can be much better than the original images of the coupling beam, with structures reduced in size by approximately a factor of 2. Experimentally, we found that the lower the degree of coherence of the coupling light, the better the cloned image compared to the coupling image for the same propagation distance. A comparison with other cloning techniques studied in the literature, with spatally coherent light, shows that our mechanism has a similar performance, with a maximum cloned image transmission by the atomic vapor of approximately 10% / Doutorado / Física / Doutor em Ciências / 153079/2010 / 0554/15 / CNPQ / Funcamp

"Optical vortices are ubiquitous features of electromagnetic radiation that are often described as a destructive null in a beam of coherent light. Optical vortices may be created by a variety of different methods, one of which is by the use of a diffractive vortex mask, which is a plate of glass that has been etched in a spiral staircase pattern such that the thickness of the mask varies harmonically in the azimuthal direction. Light passing through the mask gains an azimuthal variation in phase due to the index mismatch between the glass substrate and the surrounding medium and thus an optical vortex is created. There is an implicit assumption that the light is spatially coherent, or in other words, that there is a definite phase relationship between each point in the beam. Optical vortices are not believed to occur in completely incoherent light where the term “phase” no longer holds any meaning. Optical vortices are also poorly understood in partially coherent light where statistics must be used to quantify the phase. The purpose of the research presented in this thesis was to determine how spatial coherence affects the transmission properties of the vortex phase mask. This research enabled us to create a coherence filtering technique based upon the vortex diffractive mask. In this dissertation I will demonstrate the usefulness of this filtering technique in two specific applications. First in the detection of forward-scattered light, where the un-scattered probe beam may blind a detector making detection of the scattered light extremely difficult. Second, in the enhanced resolution of two nearby objects, where the signal from one object may be lost in the glare of a brighter companion. This filtering technique has a wide field of possible applications including the detection of extra-solar planets, the detection of defects in laser optics, and improved methods in optical tomography."

In the last fifteen years, a great deal of effort has been put forth, worldwide, for investigating and enhancing various aspects of optical coherence tomography (OCT). This thesis begins with a description of the technique of OCT, and an analysis of its underlying theory. The design and construction of an OCT system is described, with particular emphasis on a novel delay scanning method, and novel signal processing. Application of OCT to non-destructive characterisation of seeds, examination of skin lesions, measurement of fluid flow, and refractive index determination, are then demonstrated. Two technological enhancements to OCT are presented in this thesis. The first, an extended-range Fourier domain optical delay line (FDODL), extends the scan range of the traditional FDODL by a factor of almost 9, by scanning the galvanometer mirror around the region of zero tilt-angle. Polarisation optics are used to prevent light coupling back into the interferometer after only a single pass through the FDODL. A non-coplanar version of the FDODL is also presented, which overcomes the losses associated with the polarisation-based design, but trades off scan range to do so. Both versions of FDODL demonstrated excellent linearity and scan uniformity. The second technology presented here, bifocal optical coherence refractometry (BOCR), affords OCT the ability to measure refractive indices within turbid media. It achieves this by generating two confocal gates within the sample. From knowledge of the system parameters, and measurements of the confocal gate separation, the refractive index within the medium is evaluated to within ±0.01. Refractive index mapping is then demonstrated in a number of turbid samples. Three other applications of OCT are also demonstrated in this thesis. The first is the use of OCT to measure full thickness in lupin seeds. Although OCT could not penetrate the entire thickness of the hull, it is demonstrated that the variation in thickness of the two layers observed with OCT, explained 81% of the variation in thickness of the entire hull measured under a SEM. OCT was then applied, for what is believed to be the first time, in a large scale seed screening program. The second application is a preliminary investigation of the suitability of OCT to aid in the diagnosis of skin lesions. Although our system did not possess sufficient positioning accuracy to enable a direct one-to-one comparison between OCT and histology, a number of correspondences between OCT and histology images were demonstrated. The final application of OCT demonstrated here is a novel phase-locked-loop based demodulation scheme, to perform Doppler OCT. This demodulation scheme demonstrated a dynamic range of 98dB, a velocity range of ±20mm/s, and velocity resolution of 0.5mm/s. Using this system, laminar flow was demonstrated in milk flowing through a capillary tube.

[Truncated abstract] This thesis describes the development, clinical validation and initial application of a technique for taking measurements of the shape and dimensions of the human upper airway, called anatomical optical coherence tomography (aOCT). The technique uses a transparent catheter containing a rotating optical probe which is introduced transnasally and positioned in the airway and oesophagus. Optical coherence tomography is used to take calibrated cross-sectional images of the airway lumen as the probe rotates. The probe can also be advanced or withdrawn within the catheter during scanning to build up three-dimensional information. The catheter remains stationary so that the subject is not aware of the probe motion. The initial application of the system is research into obstructive sleep apnoea (OSA), a serious condition characterized by repetitive collapse of the upper airway during sleep and an independent risk factor for deaths by heart disease, strokes or car accidents. Measurement of upper airway size and shape is important for the investigation of the pathophysiology of OSA, and for the development and assesment of new treatments. . . We have used aOCT to capture three-dimensional data sets of the airway shape from upper oesophagus to the nasal cavity, undertaken measurements of compliance and other airway characteristics, and recorded dynamic airway shape during confirmed sleep apnoea events in a hospital sleep laboratory. We have shown that aOCT generates quantitative, real-time measurements of upper airway size and shape, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology, and aid clinical management and treatment development.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Adaptive-optics optical coherence tomography (AOOCT) is a technology that has been rapidly advancing in recent years and offers amazing capabilities in scanning the human eye in vivo. In order to bring the ultra-high resolution capabilities to clinical use, however, newer technology needs to be used in the image reconstruction process. General purpose computation on graphics processing units is one such way that this computationally intensive reconstruction can be performed in a desktop computer in real-time. This work shows the process of AOOCT image reconstruction, the basics of how to use NVIDIA's CUDA to write parallel code, and a new AOOCT image reconstruction technology implemented using NVIDIA's CUDA. The results of this work demonstrate that image reconstruction can be done in real-time with high accuracy using a GPU.

Indiana University-Purdue University Indianapolis (IUPUI) / Adaptive optics-optical coherence tomography (AO-OCT) is a non-invasive method of imaging the human retina in vivo. It can be used to visualize microscopic structures, making it incredibly useful for the early detection and diagnosis of retinal disease. The research group at Indiana University has a novel multi-camera AO-OCT system capable of 1 MHz acquisition rates. Until this point, a method has not existed to process data from such a novel system quickly and accurately enough on a CPU, a GPU, or one that can scale to multiple GPUs automatically in an efficient manner. This is a barrier to using a MHz AO-OCT system in a clinical environment. A novel approach to processing AO-OCT data from the unique multi-camera optics system is tested on multiple graphics processing units (GPUs) in parallel with one, two, and four camera combinations. The design and results demonstrate a scalable, reusable, extensible method of computing AO-OCT output. This approach can either achieve real time results with an AO-OCT system capable of 1 MHz acquisition rates or be scaled to a higher accuracy mode with a fast Fourier transform of 16,384 complex values.