The optical power of a lens is determined by the surface curvature and the refractive index, n. Knowledge of the index is required for accurate lens design models and for examining material variations from sample to sample. The refractive index of glass can be accurately measured using a prism spectrometer, but measuring the index of soft contact lens materials presents many challenges. These materials are non-rigid, thin, and must remain hydrated in a saline solution during testing. Clearly an alternative to a prism spectrometer must be used to accurately measure index.A Dual Interferometer System has been designed, built and characterized as a novel method for measuring the refractive index of transparent optical materials, including soft contact lens materials. The first interferometer is a Low Coherence Interferometer in a Twyman-Green configuration with a scanning reference mirror. The contact lens material sample is placed in a measurement cuvette, where it remains hydrated. By measuring the locations of the multiple optical interfaces, the physical thickness t of the material is measured. A new algorithm has been developed for processing the low coherence signals obtained from the reflection at each optical interface.The second interferometer is a Mach-Zehnder interferometer with a tunable HeNe laser light source. This interferometer measures the optical path length (OPL) of the test sample in the cuvette in transmission as a function of five wavelengths in the visible spectrum. This is done using phase-shifting interferometry. Multiple thickness regions are used to solve 2π phase ambiguities in the OPL.The outputs of the two interferometers are combined to determine the refractive index as a function of wavelength: n(λ) = OPL(λ)/t. Since both t and OPL are measured using a detector array, n is measured at hundreds of thousands of data points. A measurement accuracy of 0.0001 in refractive index is achieved with this new instrument, which is verified using custom glass calibration samples.

This thesis proposes and tests an individually customizable model of the human crystalline lens. This model will be crucial in developing both research on the human eye and driving diagnostic tools to help plan and treat optical issues, such as those requiring refractive surgery. This thesis attempts to meet two goals: first, it will determine whether this new lens model can reproduce the major aberrations of real human eyes using a computational framework. Second, it will use clinical information to measure how well this model is able to predict post-operation results in refractive surgery, attempting to meet clinical standards of error. The model of the crystalline lens proposed within this thesis is shown to be valid, as it is able to both reproduce individual patient's optical information, and correctly predicts the optical results of a refractive surgery of an individual human eye within clinical standards of error.

The aim of this thesis is to quantify the impact of atmospheric turbulence on optical signal used in free space optic communication systems. The first part is associated with atmosphere as transmission medium. Following part deals with interferometry and components of interferometers. Various methods of analysis of trasmission environment for optical beam are introduced theoretically and experimentally. Mathematical apparatus based on Kolmogorov’s cascade theory, Rytov’s variance was used to find value of structural parameter of refraction as a main measure of turbulence intensity. Experimentally obtained data were subjected to statistical analysis. The visualization of interference pattern fluctuations under turbulent conditions is shown in the last section. Interferometric method was realized with Michelson interferometer.

Neutron detection is important in several fields, especially detection of illicit nuclear material. Historically, 3He has been the basis for these technologies. Modern realities have necessitated the development of new technologies and the exploration of new materials to meet this need. One potential solution is known as capture-gating, which is a measurement approach that is good at differentiating between incident neutrons and gamma rays. The key issue is that materials used in current capture-gating devices can suffer from poor optical performance. This is due to the fact that the these detectors, whether composed of a heterogeneous or homogeneous mixture of materials, are made of dissimilar materials. In the homogeneous case, this frequently results in a cloudy material (e.g. lithium-gadolinium-borate crystals), while heterogeneous cases suffer from index mismatch (e.g. glass inside a plastic scintillator). The goal of this thesis is material development and processing toward an index-matched, gadolinium-based glass, heterogeneous capture-gated neutron detector. This involved identifying the refractive index range of known gadolinium glasses and the development of polystyrene (PS) and polyvinyl toluene (PVT) co-polymers with a range of refractive indices. Specifically 1:3, 1:1, and 3:1 PS:PVT ratios were manufactured and their refractive indices were compared to those of pure PS and PVT. Two methods for uniform glass dispersion were explored; the use of a rotisserie oven and the use of centrifugal planetary mixer. Ellipsometry, refractometry, and spectroscopic transmission were all performed to optically evaluate the manufactured polymers and polymer/glass composites. The ability to produce a PS/PVT copolymer with a refractive index in the range of known gadolinium glasses was demonstrated. In addition, the benefit of matching the refractive indices when producing a glass/polymer composite was explored and the effect of index mismatch was observed. The ability to predict the refractive index of a PS/PVT blend was demonstrated but can still be improved upon. While a novel index-matched gadolinium-based heterogeneous capture-gated neutron detector was not developed as part of this work, progress was made on all material aspects to further develop a detector meeting that description. More work still needs to be done in fine tuning the index match of the glass and polymer components, in determining the ideal method of glass dispersion, and in producing larger samples.

No description available.

The aim of the present work is to experimentally study the dynamics of the formation of a fiber network formed from the filtration of a fiber suspension. This is relevant for all industrial applications (e.g. papermaking, productions of composite material, etc.) where a suspension of fibers has to flow through narrow gaps, and the quality of the product depends on the distribution of mass and orientation of the fibers. To study the dynamics of network formation, we developed an experimental setup where the filtration of a fiber suspension through a semi-permeable screen can be studied. In the setup, both the fluid and the solid phase can be visualized. The focus of the present thesis is to study the fluid flow generated during the filtration. Index of refraction matching, image processing and particle image velocimetry have been used to measure the velocity field in the proximity of the resulting fiber network. Experiments with varying fiber length and filtration velocity have been performed. The disturbances generated by the screen and the forming network was found to be confined in a region (boundary region), whose extension varies with time: first, after the formation of the first fiber layers, the extent of the boundary region increases; at later times, the boundary region is thinner. The extent appears to be correlated to the gap size either of the screen (at very early times) or of the fiber network, but independent of the filtration velocity. Fluctuations on a scale larger than a fiber length are also observed during the filtration process. These fluctuations are found to be correlated to the nondimensional number Se that relates the sedimentation velocity of a fiber to the filtration velocity. The governing non-dimensional parameters are derived from the equations. The parameters are used to relate the experimental observations to the dewatering process in papermaking. / QC 20101103

Material and structure engineering are increasingly employed in active optical media,in this context defined as media capable of providing laser or/and optical parametric gain. For laser materials, the main aim of the engineering is to tailor the absorption and emission cross sections in order to optimise the laser performance. At the same time, the engineering also results in a collateral modification of the material’s nonlinear response. In the first part of this work, the nonlinear index of refraction is characterised for two crystallographic forms of laser-ion doped and undoped double-tungstate crystals. These laser crystals have broad gain bandwidths, in particular when doped with Yb3+. As shown in this work, the crystals also have large Kerr nonlinearities, where the values vary significantly for different chemical compositions of the crystals. The combination of a broad gain bandwidthand a high Kerr nonlinearity makes the laser-ion doped double tungstates excellent candidates to employ for the generation of ultrashort laser pulses by Kerr-lens modelocking. The second part of the work relates to the applications of engineered second-order nonlinear media, which here in particular are periodically-poled KTiOPO4 crystals. Periodic structure engineering of second-order nonlinear crystals on a submicrometre scale opens up for the realisation of novel nonlinear devices. By the use of quasi-phase matching in these structures, it is possible to efficiently downconvert a pump wave into two counterpropagating parametric waves, which leads to a device called a mirrorless optical parametric oscillator. The nonlinear response in these engineered submicrometre structures is such that the parametric wave that propagates in the opposite direction of the pump automatically has a narrow bandwidth, whereas the parametric wave that propagates with the pump essentially is a frequency-shifted replica of the pump wave. The unusual spectral properties andthe tunabilities of mirrorless optical parametric oscillators are investigated. / QC 20120330

Orientador: Victor Ciro Solano Reynoso / Banca: Cláudio Luiz Carvalho / Banca: Raul Fernando Cuevas Rojas / Resumo: Estudamos o sistema 40P2O5 - 10B2O3 - (50-x)CaO - xTiO2, onde variou-se a composição do TiO2 e CaO, com x=25,20,15,10,05,03 mol%. Neste sistema temos dois formadores de vidros, o P2O5 que pode incorporar na sua rede grande quantidade de Titânio e o B2O3. Dois grupos de amostras foram estudados: um sem polarizar, e outro grupo submetido à polarização eletro térmica a 300oC aplicando 1,5KV e 2,5 KV durante 60 minutos. Foram realizadas medidas de Análise Térmica diferencial e se observa que estes vidros possui transição vítrea entorno de 600ºC, aumentando com maior quantidade de TiO2. A evidência da polarização eletro térmica se observa nos espectros de infravermelho e Uv-Vis, nestas, as bandas de absorção correspondentes sofreram ligeiras mudanças. Para estes vidros são importantes as bandas de absorção na região visível que se estende desde 400nm até 900nm devido à existência de íons Ti3+ e pares Ti3+-T 4+ em estruturas de coordenação tetraedral e octaedral. As medidas da dispersão dos índices de refração utilizando a técnica do ângulo de Brewster mostram variações conforme os comprimentos de onda. Foi avaliado o índice de refração complexo dos espectros de transmitância e refletância. A análise da parte real do índice de refração foi feita através do modelo de um único oscilador de Wemple-Didomenico que está relacionado com a dispersão normal dos vidros. Os parâmetros como energia média e energia de dispersão são baixos quando comparados com outro vidros com TiO2. Os dados da absorção na forma da função dielétrica complexa foram ajustados utilizando funções gaussianas. Os resultados indicam a formação de bandas de absorção de íons Ti3+ com estruturas possivelmente distorcidas e de coordenação tetraedral e octaedral. Temos ainda as bandas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: We studied the system 40 P2O5 - 10 B2O3 - ( 50 - x ) CaO - x TiO2, which has varied the composition of CaO and TiO2, with x = 25, 20, 15, 10, 05, 03 mol%. In this system we have two glass formers, the P2O5 that can incorporate in its network great amount of titanium B2O3. Two groups of samples were studied: one without polarize, and another group submitted to a thermal electric polarization by 300ºC applying 1.5 KV and 2.5 KV for 60 minutes. Measures were made of differential thermal analysis and observed that these glasses have glass transition around 600ºC, increasing with a great amount of TiO2. The evidence of thermal electric polarization is observed in the spectra of infrared and UV-Vis, in the corresponding absorption bands have slightly changes. For these glasses are important the absorption bands in the visible region that extends from 400nm to 900nm due to the existence of ion Ti3+ pairs and Ti3+ - T4+ in co-ordination structures tetraedral and octaedral. The measures of dispersion of the indices of refraction using the technique of Brewster angle showed variations according to wavelengths. We evaluated the complex refractive index of the spectra of transmittance and reflectance. The analysis of the real part of the index of refraction was done by a single oscillator model of Wemple-Didomenico related to the normal dispersion of glass. The parameters such as average energy and energy dispersion are low when compared with other glasses with TiO2. The data of absorption in the form of complex dielectric function were fitted using Gaussian functions. The results indicate the formation of absorption bands of ions Ti3+ with possibly distorted structures and coordination tetraedral and octaedral. We have the bands due to the existence of pairs of ions Ti3+ - Ti4+ and undergo changes as the samples polarized and not polarized. / Mestre

Denna uppsats är en beskrivning på utvecklingen av detta projekt, där fokuset handlar om teorier och fakta på ljus i samband med transparanta medium. Målet med projektet var att testa och experimentera inom det nämna området fast i 3D grafik, där resultatet är renderade bilder med analys, diskussioner och slutsatser. / This essay describes the development of this project, where the focus is on theories and facts about light and transparent mediums. The aim of the project was to test and experiment the mentioned area in 3D graphics, where the results are single rendered images with analysis, discussions and conclusions.

No description available.