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Modal birefringence and stress distribution measurement in doubt-clad rare-earth-doped fibers are reported. For example, doubt ¡Vclad ytterbium-doped fiber and doubt ¡Vclad neodymium -doped fiber. In this paper, I am interested in the effect of fabrication on birefringence of Cr4+: YAG double-clad crystal fiber. A knowledge of stress distribution in the fiber would indicate the origin of birefringence.Since fiber birefringence can be produced by different mechanisms.For example,stress-induced birefringence,geometrical anisotropy of a non-circular fiber core and inner-cladding, intrinsic birefringence, fiber bending and twist.To understand the origin of birefringence, I have obtained the stress distribution pattern in Polarization Optical Microscopy.Using scanning wavelength method (Phase Retardation), I set-up the system successfully and measured the group modal birefringence of bulk:YVO4 crystal and Cr4+ :YAG double-clad crystal fiber. I also used Jones matrix, Mueller matrix,stress optics law, photoelastic and mathematical formulas on the estimated modal birefringence to calculate the stress intensity distribution and interference light conditions and estimate the modal birefringence ,and then compared with other rare earth-doped fiber.

A new, high-speed, fiber-based Mueller-matrix optical coherence tomography system with continuous source-polarization modulation is presented. For in vivo experimentation, the sample arm optics are integrated into a hand-held probe. The system’s parameters were verified through imaging standard optical elements. A unique feature of polarization-sensitive Mueller optical coherence tomography is that by measuring Jones or Mueller matrices, it can reveal the complete polarization properties of biological samples, even in the presence of diattenuation. Presented here for the first time are mapped local polarization properties of biological samples obtained by using polar decomposition in combination with least-squares fitting to differentiate measured integrated Jones matrices with respect to depth. In addition, a new concept of dual attenuation coefficients to characterize diattenuation per unit infinitesimal length in tissues is introduced. The algorithm was experimentally verified using measurements of a section of porcine tendon and the septum of a rat heart. The application of the system for burn imaging and healing monitoring was demonstrated on porcine skin because of its similarity to the human skin. The results showed a clear localization of the thermally damaged region. The local birefringence of the intravital porcine skin was mapped by using a differentiation algorithm. The burn areas in the OCT images agree well with the histology, thus demonstrating the system’s potential for burn-depth determination and post-injury healing monitoring. Another major application of the fiber-based Mueller-matrix optical coherence tomography system with continuous source-polarization modulation covered here is in vivo imaging of early stages of skin cancer. The OCT images of SENCAR mice skin affected by the tumorigenesis show the structural changes in skin resulting from precancerous papilloma formations that are consistent with histology, which proves the system’s potential for early skin cancer detection.

Polarization-maintaining fibers (PMFs) have been widely studied and discussed. Nowadays, a novel polarization-maintaining photonic crystal fiber (PMPCF) is proposed with many advantages, such as the large mode area and the single-mode transmission in a wide frequency range. In this thesis, we propose the birefringent liquid-filled PCF with the liquid asymmetrically infiltrated in the cladding region. The Yee-mesh-based finite-difference frequency-domain (FDFD) method is utilized to analyze the birefringent properties of the liquid-filled PCFs. Compared with traditional PMFs, our proposed PCF possesses larger birefringence about 7.1 ¡Ñ 10-3 at 1.55 £gm with useful tunable properties. In the experiment, we have successfully fabricated the birefringent liquid-filled PCF by using the selective blocking technique. The elliptical far field can be observed for our birefringent PCF. We also demonstrate the experiment setup for estimating the birefringence of our birefringent liquid- filled PCF.

Orientador: Sergio Roberto Peres Line / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-10T17:02:28Z (GMT). No. of bitstreams: 1 Frozoni_MarcosRobertodosSantos_M.pdf: 11548696 bytes, checksum: f731de9d3b6f95185faf5cab3e19d566 (MD5) Previous issue date: 2008 / Resumo: A biossíntese do esmalte dentário inicia-se pela secreção, processamento proteolítico e auto-agregação de uma complexa mistura de proteínas, sintetizadas pelos ameloblastos, conhecida como matriz orgânica do esmalte. A formação desta matriz ocorre em três estágios: secreção (inicial), transição e maturação e parece ser fundamental para o controle da orientação e morfologia dos cristais de hidroxiapatita, que constituem a fase mineral do esmalte em desenvolvimento. No estágio de secreção da amelogênese, a matriz orgânica do esmalte apresenta uma organização supramolecular birrefringente, dessa forma, a referida matriz pode ser observada e quantificada por meio de microscopia de luz polarizada. Alterações genéticas e ambientais podem induzir a distúrbios na organização molecular da matriz orgânica extracellular do esmalte (MOECE) dentário no estágio secretório, gerando modificações em sua birrefringência, tais distúrbios podem contribuir para alterações na estrutura do esmalte maduro. Altos níveis de ingestão de flúor causam mudanças na estrutura e concentração das proteínas da matriz orgânica do esmalte, induzindo a falhas na mineralização e formação desorganizada dos cristais do esmalte. Estas alterações caracterizam a fluorose de esmalte e incluem aumento da porosidade, redução do conteúdo mineral e diminuição da microdureza do esmalte maduro. O objetivo deste estudo foi analisar os efeitos do flúor sobre a birrefringência da MOECE no estágio secretório. Quinze camundongos da linhagem A/J foram divididos em 3 grupos e submetidos a um tratamento de 30 dias com dieta exclusiva de ração e água deionizada ad libitum. A água ingerida continha 0, 25, e 50 ppm de flúor (NaF) nos grupos A/J-Controle, A/J-Flúor 25 ppm e A/J-Flúor 50 ppm, respectivamente. Os mesmos procedimentos foram aplicados a quinze camundongos da linhagem NOD (Non Obese Diabetic), caracterizando os grupos NOD-Controle, NOD-Flúor 25 ppm e NOD-Flúor 50 ppm. Após o período acima mencionado, todos os animais foram perfundidos com uma mistura de paraformaldeído 2% com glutaral deído 0,5% em tampão fosfato 0,2 M e suas hemimaxilas foram extraídas e mantidas na mesma solução fixadora por 16h, as amostras foram então descalcificadas em mistura de ácido nítrico 5% com formaldeído 4 % por 6 h sob agitação. Após desidratação e inclusão em parafina, obtive-se cortes longitudinais de 5µm de espessura que foram desparafinizados, hidratados, montados em solução aquosa de glicerina 80% e analisados em microscopia de luz polarizada. Realizou-se a análise da matriz orgânica dos incisivos superiores de modo a se determinar o retardo óptico em nanômetros (nm) na área de maior birrefringência no estágio de secreção da amelogênese. Os valores de retardo ótico foram submetidos à análise estatística (Kruskal-Wallis) e os grupos A/J e NOD foram comparados separadamente. Observou-se um aumento, estatisticamente significante, dos valores de retardo ótico nos grupos A/J-Flúor 25 ppm e A/J-Flúor 50 ppm, quando comparados ao grupo A/J-Controle (p<0,01). O mesmo aconteceu com os grupos NOD-Flúor 25 ppm e NOD-Flúor 50 ppm que mostraram aumento, estatisticamente significante, dos valores de retardo ótico quando comparados ao grupo NOD-Controle (p<0,01). Os grupos A/J-Flúor apresentaram valores semelhantes (p>0,05) o que também ocorreu com os grupos NOD-Flúor. Os resultados do presente estudo mostram que o flúor induz a um aumento da birrefringência da MOECE no estágio de secreção, podendo estar associado ao mecanismo de desenvolvimento da fluorose de esmalte / Abstract: Dental enamel biosynthesis begins with secretion, proteolytic processing and self-assembly of a highly complex mixture of proteins, synthesised by ameloblast, which is known as the enamel organic matrix. This matrix formation occurs at three stages: secretion (initial), transition and maturation and seems to be essential for controlling orientation and morphology of the hydroxyapatite crystals that comprise mineral phase of developing enamel. In the secretory stage of amelogenesis, the enamel organic matrix presents a birefringent supramolecular organization. Therefore, it can be observed and quantified by polarizing microscopy. Genetic and environmental alterations may induce disturbances in the molecular organization of the secretory-stage enamel organic extracellular matrix (EOECM), producing birefringence changes, these disturbances may contribute to mature enamel alterations. High levels of ingested fluoride cause modifications in the structure and concentration of proteins of the enamel organic matrix inducing failures in the mineralization and disorganized enamel crystals formation. These alterations characterize enamel fluorosis, include increased porosity, mineral content reduction and diminished mature enamel micro hardness. The aim of the present study was to analyse the effects of fluoride on the birefringence of secretory stage EOECM. Fifteen A/J inbred mice strain were divided into 3 groups and submitted to a treatment during 30 days with exclusive diet of food and deionized water ad libitum. The ingested water contained 0, 25 and 50 ppm fluoride (NaF) in the groups A/J Control, A/J 25 ppm fluoride and A/J 50 ppm fluoride, respectively. The same procedures were applied to fifteen NOD (Non Obese Diabetic) mice, which formed the groups NOD Control, NOD 25 ppm fluoride and NOD 50 ppm fluoride. After the abovementioned period, all the animals were perfused with 2% paraformaldehyde, 0.5% glutaraldehyde in 0.2 M phosphate buffered solution. Its hemimaxillae were then extracted and maintained in the same fixative solution for 16 h, the samples were decalcified under stirring in 5% nitric acid, 4% formaldehyde for 6 h. After dehydration and embedded in paraffin, longitudinal 5-µm-thick sections were obtained and deparaffined, hydrated and mounted with aqueous 80% glycerine as imbibing medium and analyzed with polarizing microscopy. Optical retardation (nm) of the area that showed the highest birefringence brightness in the EOECM of upper incisors was determined. Optical retardation values were submitted to statistical analysis (Kruskal-Wallis) and A/J and NOD groups were separately compared. An statistically significant increase in optical retardations values was observed in A/J 25 ppm Fluoride and A/J 50 ppm Fluoride, when compared to A/J Control group (p<0.01). The same happened with NOD 25 ppm Fluoride and NOD 50 ppm Fluoride groups which exhibited statistically significant increase in optical retardations values when compared to NOD Control group (p<0.01). A/J Fluoride groups presented similar optical retardation values (p>0.05) which occurred with NOD fluoride groups. The results presented here show the fluoride induces an increase in the birefringence of secretory stage EOECM, which may be associated with enamel fluorosis development. Key words: Enamel, Amelogenesis, Enamel Organic Matrix, Birefringence, Fluoride / Mestrado / Histologia e Embriologia / Mestre em Biologia Buco-Dental

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Birefringence has been used to study transparent materials since 1815, and is based on the decomposition of a polarized ray of light into two distinct rays when passing through an optically anisotropic material. This thesis uses this phenomenon in a study of phase retardation in crystalline materials. Single and multicrystalline silicon was chosen as the model material. Silicon is an interesting and important material in its own right, and the use of photoelasticity to determine stresses at linear and planar defects can have important consequences in the electrical performance of devices such as electronics and photovoltaic cells. This thesis presents the results of an experimental investigation of residual stresses in multicrystalline silicon wafers using near-infrared (NIR) transmission photoelasticity. NIR transmission through multicrystalline silicon is found to vary with crystallographic orientation and relate to planar atomic density, enabling the assignment of appropriate stress-optic coefficients to different grains. Noise in the data is reduced with the Ramji and Ramesh 10-step phase shifting algorithm when compared to the Patterson and Wang process. Normal stresses at points of zero maximum shear stress can be characterized based on isoclinic behavior around the point. Points at which all normal stresses are zero serve as boundary conditions for shear difference integration and allow for stress separation from a point that is not a free boundary. The second part of this work focuses on residual stresses in silicon wafers subjected to known physical damage such as indentations. Residual stress fields around Vickers indentations in silicon are found to be larger in size than predicted by contact mechanics. Placing Vickers indentations in close proximity creates a secondary stress field surrounding the entire indentation array, and a relationship is developed to explain this behavior. High residual stresses measured at grain boundaries are found to be consistent with models of atomic displacement. Placement of Vickers indentations near grain boundaries results in a change in stress state at the grain boundaries. The results of this study demonstrate the capacity of birefringence as a non-destructive evaluation tool and describe the effects of residual stress concentrations in silicon wafers.

This thesis concerns polarization mode dispersion (PMD) in optical fiber communications. Specifically, we study fiber birefringence, PMD stochastic properties, PMD mitigation and the interaction of fiber birefringence and fiber nonlinearity. Fiber birefringence is the physical origin of polarization mode dispersion. Current models of birefringence in optical fibers assume that the birefringence vector varies randomly either in orientation with a fixed magnitude or simultaneously in both magnitude and direction. These models are applicable only to certain birefringence profiles. For a broader range of birefringence profiles, we propose and investigate four general models in which the stochastically varying amplitude is restricted to a limited range. In addition, mathematical algorithms are introduced for the numerical implementation of these models. To investigate polarization mode dispersion, we first apply these models to single mode fibers. In particular, two existing models and our four more general models are employed for the evolution of optical fiber birefringence with longitudinal distance to analyze, both theoretically and numerically, the behavior of the polarization mode dispersion. We find that while the probability distribution function of the differential group delay (DGD) varies along the fiber length as in existing models, the dependence of the mean DGD on fiber length differs noticeably from earlier predictions. Fiber spinning reduces polarization mode dispersion effects in optical fibers. Since relatively few studies have been performed of the dependence of the reduction factor on the strength of random background birefringence fluctuations, we here apply a general birefringence model to sinusoidal spun fibers. We find that while, as expected, the phase matching condition is not affected by random perturbations, the degree of PMD reduction as well as the probability distribution function of the DGD are both influenced by the random components of the birefringence. Together with other researchers, I have also examined a series of experimentally realizable procedures to compensate for PMD in optical fiber systems. This work demonstrates that a symmetric ordering of compensator elements combined with Taylor and Chebyshev approximations to the transfer matrix for the light polarization in optical fibers can significantly widen the compensation bandwidth. In the last part of the thesis, we applied the Manakov-PMD equation and a general model of fiber birefringence to investigate pulse distortion induced by the interaction of fiber birefringence and fiber nonlinearity. We find that the effect of nonlinearity on the pulse distortion differs markedly with the birefringence profile.