This thesis presents theoretical studies of the optical and electronic properties of defects in diamond and of the mechanisms of doping graphene. The birefringence of the four petalled defect commonly observed in CVD diamond is explained by four linear arrays of dislocations along ⟨110⟩ directions with ⟨110⟩ Burgers vectors. Such an arrangement of dislocations reproduces the extension and the features of the birefringence patterns observed experimentally. Density functional theory via the AIMPRO code was used to study the electronic and optical properties of different nitrogen-related point defects in diamond. It was found that the zero-phonon luminescence line of the NV− defects can split in the presence of a surface or other NV− defects. Since VNH and VN2 are expected to have similar optical properties, the optical transi- tions for VN2 were used to correct the transitions for VNH calculated by local density approximation. The absorption band at 2.38 eV (520 nm) observed in CVD diamond is then attributed to an internal transition of VNH. The weak zero-phonon line and broad vibronic sidebands for VN− and VN−2 and its absence for VNH− is explained by the large structural change when the defect is excited. Finally, different mechanisms for doping graphene were considered. The calculations predict the electropositive metals, such as Ti and Cr, act as donors, while molecules with strong electron affinity, such as F4-TCNQ, act as acceptors in graphene. An unexpected mechanism of doping graphene was shown by Au which dopes bilayer graphene but not single layer. In the presence of water, electrochemical reactions on the graphene can also lead to p or n-type doping.

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.

The birefringence of one-dimension PMMA surface gratings on a gold film substrate is investigated. The grating served as a coupler to facilitate the incoming light coupled to surface plasmon wave (SPW) which possesses high propagation wave vector. Since surface plasmon waves(SPWs) have a special dispersion relation, the birefringence £Gneff (£Gneff =nx-ny, where grating k-vector is along x axis) of this structure is relatively large and can be changed from positive to negative by changing the operation wavelength. The obtained the four Stokes parameters at 515nm and 633nm are marked on the Poincare sphere. £Gneff is 2£k/7 and -£k/8 at 515nm and 633nm respectively. Further, by changing the form factor of PMMA gratings, we found that the maximum £Gneff occurred when PMMA stripe width : air gap=1:1.

Fiber coils had been widely investigated as optical current sensors for a long time. In this thesis we have fabricated the LMA-10 PCF coils. By using the Sagnac fiber loop, we can obtain the transmission spectrum of the PCF coils. The measured birefringence of the SMF coil and the PCF coil are 1.49¡Ñ10^-5 at £f= 959.27 nm and 1.31¡Ñ10^-5 at £f = 1264.3 nm, respectively. The birefringence of the SMF coil agrees well with the theoretical result. The properties of PCF coils for variant fiber turns and cylinder sizes are discussed. As we increase the number of fiber turns, the fringe spacing becomes smaller due to the increasing phase difference. The birefringence of the PCF coil decreases with the increasing cylinder radius. Besides, we also measure the temperature sensitivities of the SMF coil and PCF coil to be 130 pm/oC and 64.55 pm/ oC, respectively. We have also demonstrated the sensing properties of the PCF coils. By introducing a displacement along the cylinder, the bending on the PCF coil can be induced. The measured bending sensitivity is -3.732 nm/m^-1. In addition, the water depth sensing properties are obtained by horizontally and vertically immersing the PCF coils into the water. As we put the PCF coil horizontally into the water, the shift of the measured spectra shows a exponential relation to the water depth. As for the vertically immersed PCF coil, the linear water depth sensitivity is -11.658 nm/cm. Finally, we propose the transverse displacement sensor based on the PCF coil. The measured sensitivity to transverse displacement can be as large as 903.9 nm/cm.

Hybrid waveguides based on antiresonant reflecting optical waveguide (ARROW) structure on Si substrates is investigated. The core layer of the waveguide is separated from the Si substrate by interference cladding which consists of a high index first cladding layer and a low index second cladding layer. The Ta2O5 first cladding layer was grown by rf magnetron sputtering system. The SiON second cladding layer was deposited by plasma-enhanced chemical vapor deposition (PECVD) based on the reaction of SiH4/N2O mixtures. Typical propagation losses of the waveguides using this SiON material system are less than 0.15 dB/cm. The high quality cladding layers are prepared to form the Fabry-Perot cavities to ensure low loss operation of the ARROW device at antiresonant conditions. Two methods were proposed to demonstrate the enormous applications of hybrid ARROW waveguides. First, polyimide/Ta2O5/SiON ARROWs were fabricated to achieve high extinction ratio waveguide polarizers. This is accomplished by tuning the operating point of the TM0 mode from antiresonant condition toward high-order antiresonance of the second cladding layer utilizing birefringence of the waveguide core. The measured extinction ratio and insertion loss of a 2-cm-long ARROW polarizer are 40 dB and 2.2 dB, respectively. In addition, the temperature dependence of refractive index of organic-inorganic sol-gel glasses was measured by Mach-Zehnder interferometry using the ARROW waveguides. The Sol-gel/Ta2O5/SiO2 ARROWs were fabricated to characterize index-to-temperature coefficients (dn/dT) of the sol-gel glasses because the optical confinement factor of the ARROW is very close to 1. The measured index-to-temperature coefficients of the sol-gel glasses with different compositions are negative and are on the order of 10-4.

In a continuing effort to develop a noninvasive means of monitoring glucose levels using the aqueous humor of the eye, a dual wavelength system has been developed in order to show that varying birefringence, similar to what is seen with a moving cornea, can be compensated. In this paper a dual wavelength, closed-loop, system was designed and a model was developed to extract the glucose concentration information. The system and model were tested using various concentrations of glucose in a birefringent test cell subject to motion artifact. The results show that for a static, non-moving sample, glucose can be predicted to within 10 mg/dl for the entire physiologic range (0-600mg/dl) for either laser wavelength (523nm or 635nm). In the presence of moving birefringence, each individual wavelength produced standard errors on the order of a few thousand mg/dL. However, when the two wavelengths are combined into the developed model, this error is less than 20mg/dL. The approach shows that multiple wavelengths can be used to drastically reduce the error in the presence of a moving birefringent sample. This research also shows promising preliminary results that the error is less than 25mg/dl in presence of a motion induced cornea birefringence artifact in NZW rabbits’ eyes.

It is widely recognised that the development and optimisation of industrial processes such as extrusion or injection moulding significantly benefit from accurate polymer processing simulations. Such simulations can lead to enormous cost savings, time to market and product improvements. The development of suitable constitutive models and a robust numerical algorithm are required for successful application of such tool to these processes. Appropriate material characterisation is also imperative to select the constitutive model parameters. Despite the importance and maturity of the polymer processing industry, the constitutive modelling of the rheological behaviour of long chain branched polymers presents still fascinating questions that need some answers. A breakthrough in this area was the design of a constitutive equation based on molecular arguments and known as the pom-pom model. The key feature of this model is the presence of separate relaxation times for the orientation and stretch mechanisms. The pompom model has been proved to be very accurate for the modelling of long chain branched polymers in rheometrical flows. Although very promising, this model suffers from numerical and rheological defects that hinder its use in complex flow simulations. To overcome these issues, the Double Convected pom-pom (DCPP) model is proposed. Its predictive capabilities are first analysed in various rheometrical flows including reverse multi-step shear strain and large amplitude oscillatory shear experiments. For complex flow simulation, the DCPP model is implemented in the commercial package POLYFLOW.Model predictions are compared to experimental birefringence data in planar contraction flows. In all cases, a satisfactory agreement is found between numerical simulation and experiments, demonstrating the potential of this model for the simulation of polymer processing operations. The simulations are then extended to three-dimensional geometries. The influence of non-perfectly two-dimensional flows on birefringence data is analysed. It is shown that the impact of these imperfections is strongly dependent on the flow rate. Is is commonly believed that increasing the geometry aspect ratio tends to decrease three-dimensional influence. It is demonstrated that this is verified only if the zero-order fringe does not disappear at any time during the experiment. Finally, a pragmatic approach is introduced to reformulate constitutive equations to explicitly express them in terms of orientation and stretch variables. This procedure is applied to the Phan-Thien Tanner and Giesekus models and both modelsare compared to the DCPP model. Comparing the models in this form, highlights their differences, and allows one to adopt the best features of each. This almost naturally leads to a proposal of a number of modifications to each of these models. The modified models are then assessed in rheometrical flows by comparing model predictions to experimental data. Significant improvements are demonstrated for in particular the Modified Giesekus model and the Modified DCPP: both models perform remarkably well in a range of non-linear rheometric flows, and are therefore promising candidates for predicting industrial flow problems.

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-22Bitstream added on 2014-06-13T19:29:26Z : No. of bitstreams: 1 shimizu_fm_me_bauru_prot.pdf: 2503731 bytes, checksum: 27862595949ca55dc6df971eb795c314 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Foram estudadas as monocamadas de Langmuir, filmes Langmuir-Blodgett (LB) e filmes finos preparados pela técnica de casting (filmes auto-sustentados) usando vários tipos de moléculas de azocoroa de éter. Os filmes foram caracterizados por espectroscopia de UV-Vis, FTIR e espalhamento Raman. O composto 29-diazocoroa de éter com dois substituinte n-octil foi a única molécula de azocoroa de éter que permitiu a preparação de filmes LB de alta qualidade e com propriedades ópticas adequadas para uso no estudo de birrefringência fotoinduzida. Nas medidas de birrefringência foram empregados os filmes preparados do composto 29-diazocoroa de éter pela técnicas LB e casting, variando-se os seguintes parâmentros experimentais: número de monocamadas do filme LB, espessura de filme auto-sustentado, intensidade da luz de excitação e temperatura. A dinâmica de formação e decaimento de birrefringência mostrou ser muito mais rápida para os filmes LB do que para os filmes auto-sustentados. As curvas experimentais da dinâmica da birrefringência fotoinduzida para os filmes LB foram ajustadas usando as equações de Debye e de Kohlrausch-Williams-Watts (KWW), enquanto que as curvas experimentais dos filmes auto-sustentados foram ajustados usando as equações de Sekkat e de KWW. Usando as constantes de tempo obtidas dos ajustes das curvas experimentais de birrefringência, foi possível calcular as energias de ativação de Arrheniu dos processos de foto orientação. Os resultados obtidos para a energia de ativação e da dinâmica de formação e decaimento das medidas de birrefringência para os diferentes filmes foram comparadas e discutidas. / Langmuir monolayers, Langmuir-Blodgett (LB) films and thin filmes prepared by casting (auto standing films) from a series of azocrown ethers molecules were studied. Films were characterized using UV-Vis and FTIR spectroscopy and Raman scattering techniques. The compound 29-diazocrown ether with n-octyl substituent was the only azocrown ether molecule that allowed us to prepare high quality LB films having suitable optical properties for photo induced birefringence studies. On birefringence measurements using LB films and standing films of 29-diazocrown ether several experimental parameters were varied: number of monolayer of BL films, thickness of the auto standing film, excitation light intensity and temperature. It was found for the dynamics of formation and decay of the birefringence is much faster for LB films when compared with the auto standing films. The experimental curves of birefringence signals for LB films were fitted using the Debye and Kohlrausch-Williams-Watts (KWW) functions while the experimental curves for the auto standing films were fitted using the Sekkat and KWW functions. From the obtained time constants of fittings the Arrehnius activation energy and the dynamics of the formation and decay of the birefringence for the films were compared and discussed.

Orientador: José Alberto Giacometti / Banca: Marystela Ferreira / Banca: Elisabeth Andreoli de Oliveira / - O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Foram estudadas as monocamadas de Langmuir, filmes Langmuir-Blodgett (LB) e filmes finos preparados pela técnica de casting (filmes auto-sustentados) usando vários tipos de moléculas de azocoroa de éter. Os filmes foram caracterizados por espectroscopia de UV-Vis, FTIR e espalhamento Raman. O composto 29-diazocoroa de éter com dois substituinte n-octil foi a única molécula de azocoroa de éter que permitiu a preparação de filmes LB de alta qualidade e com propriedades ópticas adequadas para uso no estudo de birrefringência fotoinduzida. Nas medidas de birrefringência foram empregados os filmes preparados do composto 29-diazocoroa de éter pela técnicas LB e casting, variando-se os seguintes parâmentros experimentais: número de monocamadas do filme LB, espessura de filme auto-sustentado, intensidade da luz de excitação e temperatura. A dinâmica de formação e decaimento de birrefringência mostrou ser muito mais rápida para os filmes LB do que para os filmes auto-sustentados. As curvas experimentais da dinâmica da birrefringência fotoinduzida para os filmes LB foram ajustadas usando as equações de Debye e de Kohlrausch-Williams-Watts (KWW), enquanto que as curvas experimentais dos filmes auto-sustentados foram ajustados usando as equações de Sekkat e de KWW. Usando as constantes de tempo obtidas dos ajustes das curvas experimentais de birrefringência, foi possível calcular as energias de ativação de Arrheniu dos processos de foto orientação. Os resultados obtidos para a energia de ativação e da dinâmica de formação e decaimento das medidas de birrefringência para os diferentes filmes foram comparadas e discutidas. / Abstract: Langmuir monolayers, Langmuir-Blodgett (LB) films and thin filmes prepared by casting (auto standing films) from a series of azocrown ethers molecules were studied. Films were characterized using UV-Vis and FTIR spectroscopy and Raman scattering techniques. The compound 29-diazocrown ether with n-octyl substituent was the only azocrown ether molecule that allowed us to prepare high quality LB films having suitable optical properties for photo induced birefringence studies. On birefringence measurements using LB films and standing films of 29-diazocrown ether several experimental parameters were varied: number of monolayer of BL films, thickness of the auto standing film, excitation light intensity and temperature. It was found for the dynamics of formation and decay of the birefringence is much faster for LB films when compared with the auto standing films. The experimental curves of birefringence signals for LB films were fitted using the Debye and Kohlrausch-Williams-Watts (KWW) functions while the experimental curves for the auto standing films were fitted using the Sekkat and KWW functions. From the obtained time constants of fittings the Arrehnius activation energy and the dynamics of the formation and decay of the birefringence for the films were compared and discussed. / Mestre

Orientador: Alexandre Augusto Zaia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-17T13:51:39Z (GMT). No. of bitstreams: 1 Moreira_DannaMota_D.pdf: 2298709 bytes, checksum: 74c928e8904a305bd8054a46f8c5d001 (MD5) Previous issue date: 2011 / Resumo: Dentre os protocolos de irrigação mais utilizados mundialmente, a associação do hipoclorito de sódio (NaOCl) e o EDTA merece destaque. Entretanto, estes agentes químicos podem causar efeitos deletérios nas propriedades químicas e físicas da dentina, além da ação oxidativa do NaOCl interferir no comportamento de materiais restauradores. O uso de agentes redutores tem demonstrado minimizar os efeitos deletérios do NaOCl previamente a procedimentos restauradores. No primeiro estudo que compõe esta tese teve-se como objetivo avaliar os efeitos do ácido ascórbico 10% e/ou ascorbato de sódio 10% após a irrigação com NaOCl 5,25%, EDTA 17% ou cloreto de sódio 0,9% no colágeno presente na matriz orgânica da parede dentinária do canal radicular de incisivos bovinos. Foram utilizados oitenta incisivos bovinos aleatoriamente divididos em oito grupos (n=10): G1(Controle): cloreto de sódio 0,9%; G2: NaOCl 5,25% + EDTA 17%; G3: NaOCl 5,25% + EDTA 17% + ácido ascórbico 10%; G4: NaOCl 5,25% + EDTA 17% + ascorbato de sódio 10%; G5: NaOCl 5,25%; G6: EDTA 17%; G7: ácido ascórbico 10%; G8: ascorbato de sódio 10%. Os espécimes foram submetidos à instrumentação e irrigação com as diferentes substâncias químicas auxiliares e em seguida submetidos ao processamento histológico para análise em microscopia de polarização. Os grupos que demonstraram alteração no padrão de birrefringência foram submetidos à análise de absorbância para a confirmação da perda de proteína. Foi possível concluir que o uso do ácido ascórbico 10% e/ou ascorbato de sódio 10% conseguiu restabelecer os valores de retardo óptico antes diminuídos pelo uso de NaOCl 5,25%, associado ou não ao EDTA 17%. Já no segundo estudo, este teve como objetivo avaliar os efeitos do ácido ascórbico 10% e/ou ascorbato de sódio 10% após a irrigação com NaOCl 5,25%, EDTA 17% ou cloreto de sódio 0,9% na microdureza Knoop e resistência flexural da dentina radicular bovina. A distribuição dos grupos foi feita de forma similar ao primeiro estudo. Foram utilizados 80 dentes bovinos para o teste de microdureza Knoop e 120 barras de dentina para o ensaio de flexão de 3-pontos. O NaOCl 5,25% reduziu de forma significativa os valores de microdureza Knoop, chegando a afetar a dureza mesmo em grandes profundidades na dentina radicular bovina. A aplicação de ascorbato de sódio conseguiu revertes os valores previamente reduzidos de microdureza. Ficou comprovado que o NaOCl 5,25% afeta de forma negativa a resistência flexural, mas ao se fazer uso do ácido ascórbico após o protocolo de irrigação com NaOCl e EDTA, os valores de resistência flexural foram restabelecidos, chegando mesmo a equiparar-se ao grupo controle / Abstract: Among the auxiliary chemical substances used in Endodontics during chemical-mechanical preparation, sodium hypochlorite (NaOCl) and EDTA have been the most widely recommended. However, irrigant solutions used in endodontic therapy might yield changes in the chemical and physical properties of dentin. Besides, these reagents compromised the bond strengths of some adhesives on root dentin. The aim of the first study was to evaluate the effect of 10% acid ascorbic or 10% sodium ascorbate on organic matrix collagen of bovine dentin root canal walls after irrigation with 5.25% sodium hypochlorite, 17% EDTA or 0.9% sodium chloride. Eighty bovine incisors were randomly divided into eight groups (n=10) according to: G1(Control): 0.9% Sodium Chloride; G2: 5.25% NaOCl + 17% EDTA; G3: 5.25% NaOCl + 17% EDTA + 10% ascorbic acid; G4: 5,25% NaOCl + 17% EDTA + 10% sodium ascorbate; G5: 5.25% NaOCl; G6: 17% EDTA; G7: 10% ascorbic acid; G8: 10% sodium ascorbate. Teeth were chemomechanically prepared and submitted to histological processing to be analyzed under polarized light microscopy. Absorbance assay was also performed to confirm the loss of collagen. It is possible to conclude that groups treated with 5.25% NaOCl (G2 and G5) presented a significantly different birefringence pattern compared with the control group (p<0.05).The birefringence values reduced could be reversed by the application of either 10% ascorbic acid or 10% sodium ascorbate after 5.25% NaOCl and 17% EDTA irrigation. The absorbance assay of G2 and G5 confirmed the loss of collagen (p<0.05). The second study aimed to evaluate the effect of 10% ascorbic acid or 10% sodium ascorbate application after 5.25% NaOCl, 17% EDTA or 0.9% sodium chloride irrigation in the Knoop microhardness and flexural strength on root dentin. Eighty bovine incisors were randomly divided into eight groups (n=10): G1 (Control): 0.9% Sodium Chloride; G2: 5.25% NaOCl + 17% EDTA; G3: 5.25% NaOCl + 17% EDTA + 10% ascorbic acid; G4: 5.25% NaOCl + 17% EDTA + 10% sodium ascorbate; G5: 5.25% NaOCl; G6: 17% EDTA; G7: 10% ascorbic acid; G8: 10% sodium ascorbate. Teeth were chemomechanically prepared and submitted to Knoop microhardness. Standardized plano-parallel dentin bars were prepared and randomly divided into the same eight groups (n=15) cited above. The dentin bars were then loaded to failure in a three-point bend test. Root canal irrigation with 5.25% NaOCl reduced the microhardness of dentin in all distances tested. The microhardness values increased in all distances when sodium ascorbate was used after 5.25% NaOCl and 17% EDTA irrigation. By exposing the dentin bars to 5.25% NaOCl, whether it was associated or not to 17% EDTA, the flexural strength decreased. However, values increased when 10% ascorbic acid or 10% sodium ascorbate were used after 5.25% NaOCl and 17% EDTA irrigation / Doutorado / Endodontia / Doutor em Clínica Odontológica