No description available.

<p> A well characterized titanate system, Nd1_xTi03, has been studied by temperature dependent reflectance spectroscopy between 50 and 40 000 cm-1 at three different doping levels, x = 0.019, 0.046, and 0.095, which yield a Matt-Hubbard insulator, a semiconductor and a correlated metal, respectively. Two main issues are discussed regarding the optical properties of the current system. The first is the variation of the low-lying electronic structure with hole concentration. The doping-dependent optical conductivity of Nd1_xTi03 shows several obvious differences when compared to the superconducting cuprates. We observed mid-infrared absorption bands in the doped samples, suggesting that mid-gap states develop inside the Hubbard gap with hole doping in the context of a two-component model. A quantitative analysis of the spectral weight below 1.2 e V as a function of doping indicates that the evolution rate of the optical excitations below 1.2 eV is related to the electron correlation strength of the parent insulator, which has been observed in other titanates as well. The second issue addressed in this thesis is the temperature-dependent optical features of the correlated metallic sample with x = 0.095, a composition close to the metal-insulator transition at x '"'-~ 0.08. The optical conductivity shows an anomalous enhancement of spectral weight below leV, in both the Drude and midinfrared part, that develops with decreasing temperature. The dynamical mean field theory (DMFT) may explain this feature. Meanwhile, the metallic sample displays a Fermi-liquid like behavior in the low-frequency limit, which can be established from the spectra of the scattering rate as a function of both frequency and temperature. We found a good agreement between the experimental results extracted from the scattering rate and the Fermi-liquid theory. </p> / Thesis / Master of Science (MSc)

Nonlinear optics is a field with new applications being regularly discovered, which leads to a growing interest in computing these properties. In this work, we attempt to determine new methods of computationally determining the properties of biologically relevant systems. We do so through testing a novel finite-field method to compute these properties. To facilitate the computation of molecular energies required for finite-field calculations, we tested a hypergeometric resummation scheme. Together, these projects form a strong step into being able to compute the nonlinear optical properties for larger systems of biological relevance. / Thesis / Master of Science (MSc)

For each of 24 grains of low plagioclase with ‘Inferred An' contents 4.1, 6.8, 16.6, 27.7, 30.2, 35.8, 36.6, 37.6, 38.7, 43.1, 44.2, 48.0, 50.8, 51.9, 55.0, 56.5, 56.6, 57.9, 61.8, 62.1, 64.5, 76.8, 78.2, and 90.4 the following properties were measured: (1) y*, (2) location of the crystallographic axes, (3) separation of the non-Bragg e-diffractions from precession photographs, (4) refractive indices α, β, and γ, (5) the location of the optic axes, (6) the location of the principal vibration directions X, Y, and Z, (7) and a value of 2V. Plots of y* versus the product, αβγ, which correlates linearly to anorthite content, confirm the presence of two structural discontinuities in the low plagioclase series. The angular attitude of the two optic axes and of the principal vibration directions plotted stereographically relative to b* (at S = 0, E= 0) andc (at S = 90, E = 90) for each grain follow the classic migration curves of Reinhart (1931) with slight revision. The orientation of the principal vibration axes X, Y, and Z is related quantitatively to crystallographic directions b*, c, and A by means of Euler angles Φ, θ, and ψ introduced by Burri et al. (1967) and to the crystallographic axes a, b*, and C by a set of new Euler angles θ₁, θ₂, and θ₃. / Master of Science

No description available.

Raman scattering and ultraviolet-visible reflectivity have been used to characterize the structural and electronic changes that occur in GaAs during ion implantation and subsequent annealing. In this work, the damaged structure is modelled as an amorphous GaAs matrix embedded with GaAs microcrystals. The longitudinal-optic (LO) Raman-line characteristics were monitored to determine the amorphous volume fraction, the average microcrystal diameter and, for the annealed samples, the carrier concentration. An oscillator analysis of the reflectivity spectra, along with the effective medium approximation, was carried out to determine the linewidths of the interband peaks and the amorphous volume fraction in the damage layer. To determine damage depth profiles, spectra were taken as a function of the amount of material removed via chemical etch. A new method of interpreting reflectivity spectra was developed to deal with the etchant-induced roughness. This roughness reduced the reflectivity by a constant factor in the region between 4.5 and 5 eV. The ratio between reflectivities at 4.55 and 4.75 eV was monitored to determine qualitatively the amount of damage. The annealing studies show that structural recovery occurs at a lower temperature than that for which electrical activation occurs. The depth profile of a sample annealed at 400°C reveals that nucleation takes place not only at the boundary between the damaged and undamaged layers (i.e., "epitaxial regrowth") but also at the microcrystal/amorphous interfaces within the damage layer. The oscillator analysis of the dielectric properties was further developed, and a connection was established between the Strengths, positions, and linewidths of the interband oscillators and the shift in position of the LO Raman line. The results indicate that the static dielectric constant is independent of microcrystal size. A comparison between (211) and (100) oriented Si-implanted GaAs was done as well, showing greater near surface damage and a shallower total damage layer for the (211) samples. Finally, a method for characterizing damage, based on the observed shifts of the two-phonon ("2LO") Raman peak as the incident photon energy is varied around the E₁ interband energy (2.9 eV), has been developed. The results suggest that the total mass of the electron-hole pair involved in the scattering process increases even for large (>400 Å) microcrystals. The 525°C annealed sample had little damage, and was studied with this technique. / Ph. D.

Yes / Finding a path towards a more accurate prediction of light propagation in human skin remains an aspiration of biomedical scientists working on cutaneous applications both for diagnostic and therapeutic reasons. The objective of this study was to investigate variability of the optical properties of human skin compartments reported in literature, to explore the underlying rational of this variability and to propose a dataset of values, to better represent an in vivo case and recommend a solution towards a more accurate prediction of light propagation through cutaneous compartments. To achieve this, we undertook a novel, logical yet simple approach. We first reviewed scientific articles published between 1981 and 2013 that reported on skin optical properties, to reveal the spread in the reported quantitative values. We found variations of up to 100-fold. Then we extracted the most trust-worthy datasets guided by a rule that the spectral properties should reflect the specific biochemical composition of each of the skin layers. This resulted in the narrowing of the spread in the calculated photon densities to 6-fold. We conclude with a recommendation to use the identified most robust datasets when estimating light propagation in human skin using Monte Carlo simulations. Alternatively, otherwise follow our proposed strategy to screen any new datasets to determine their biological relevance. / European Marie-Curie Actions Programme, Grant agreement no. 607886

MSc., Faculty of Science, University of the Witwatersrand, 2011 / Atmospheric aerosols have direct and indirect impacts on the earth’s radiation budget and the radiative forcing on the climate system. A large uncertainty exists regarding aerosols and the effect they have on the earth’s radiation budget and global change. The distribution, concentration and types of aerosols are therefore of great importance regarding global warming and climate change. The purpose of this study is to present the atmospheric aerosol characteristics found over the South Atlantic, Southern Ocean and Antarctic continent as well as identify their origin. The aerosol optical properties over the South Atlantic and Southern Ocean region is analysed during the South African National Antarctic Expedition 2007/2008 (SANAE 47) take over cruise on board the M/V S.A. Agulhas. Very low aerosol optical thickness (AOT) values were obtained for the Antarctic Coastal region with a mean AOT500nm of 0.03 and a mean Angstrom exponent of 1.78. The South Atlantic region showed a mean AOT500nm of 0.06 and a mean Angstrom exponent of 0.72. AOT values for the South African coastal region had a mean AOT500nm of 0.07 and a mean Angstrom exponent of 0.76. Data comparisons confirm that the data acquired during the study are consistent with previous research from the study region. Comparisons were made between the dataset and the MODIS satellite aerosol product. A discrepancy was shown to exist between the MODIS aerosol product and the acquired dataset using the Microtops II Sunphotometer. Both MODIS TERRA and AQUA overestimate AOT at 550nm.

Zhao, Lei = 介孔材料的光學應用和表面等離子體-熒光分子之間相互作用 / 趙磊. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Zhao, Lei = Jie kong cai liao de guang xue ying yong he biao mian deng li zi ti - ying guang fen zi zhi jian xiang hu zuo yong / Zhao Lei.

Chan Jacklynn = 摻近紅外染料溶凝膠薄膜之光學及激光性質研究 / 陳在琳. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 137-152). / Text in English; abstracts in English and Chinese. / Chan Jacklynn = Shan jin hong wai ran liao rong ning jiao bo mo zhi guang xue ji ji guang xing zhi yan jiu / Chen Zailin. / Abstract --- p.i / Acknowledgements --- p.v / Publications --- p.vii / Table of Contents --- p.viii / List of Figures --- p.xi / List of Tables --- p.xiv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Sol-gel Glass Waveguides --- p.3 / Chapter 1.2 --- Ellipsometry --- p.7 / Chapter 1.3 --- Aim of this Research Work and Organization of Thesis --- p.12 / Chapter 2 --- Basics on Ellipsometry --- p.16 / Chapter 2.1 --- Principle of Ellipsometry --- p.17 / Chapter 2.1.1 --- Definition of Ellipsometric Parameters --- p.17 / Chapter 2.1.2 --- Configurations of an Ellipsometer --- p.22 / Chapter 2.2 --- Mathematical Representation of Ellipsometry --- p.26 / Chapter 2.2.1 --- Bulk Material Structure --- p.26 / Chapter 2.2.2 --- Single Layer Structure --- p.28 / Chapter 2.3 --- Parameterization of Optical Functions --- p.31 / Chapter 2.3.1 --- Optical Functions --- p.34 / Chapter 2.3.2 --- Regression Analysis --- p.38 / Chapter 3 --- Modification of Rotating-Polarizer-Analyzer Ellipsometer --- p.40 / Chapter 3.1 --- Principle of RPA System --- p.41 / Chapter 3.2 --- Optical Setup of RPA System --- p.45 / Chapter 3.3 --- Components of the System and Modification for Infrared Measurement --- p.47 / Chapter 3.3.1 --- Light Source --- p.47 / Chapter 3.3.2 --- Monochromator --- p.52 / Chapter 3.3.3 --- Polarizers and Analyzer --- p.53 / Chapter 3.3.4 --- Detector and Data Reduction --- p.54 / Chapter 3.4 --- Optical Alignment --- p.59 / Chapter 3.5 --- Alignment of the Azimuthal Angles of the Polarizers --- p.61 / Chapter 3.6 --- Calibration Procedure --- p.63 / Chapter 3.6.1 --- Calibration by Gold Film on Silicon --- p.63 / Chapter 3.6.2 --- Calibration by Silicon Dioxide Film on Silicon --- p.67 / Chapter 4 --- Near Infrared Dyes in Sol-gel Waveguides --- p.72 / Chapter 4.1 --- Sol-gel Process --- p.73 / Chapter 4.2 --- Near Infrared Dyes in Sol-gel Waveguides --- p.77 / Chapter 4.2.1 --- Development of Near Infrared Dyes --- p.77 / Chapter 4.2.2 --- Studies on Near Infrared Dye Solid State Laser --- p.79 / Chapter 5 --- Optical Properties of Dye-doped Sol-gel Waveguides --- p.83 / Chapter 5.1 --- Experimental Procedure --- p.84 / Chapter 5.1.1 --- Preparation of Samples --- p.84 / Chapter 5.1.1.1 --- Materials --- p.84 / Chapter 5.1.1.2 --- Procedure --- p.86 / Chapter 5.1.2 --- Discussion on Synthesis of Infrared Dye-doped Sol-gel Waveguides --- p.88 / Chapter 5.1.2.1 --- Choice of Solvents --- p.89 / Chapter 5.1.2.2 --- Thermal Treatment and Lifetime --- p.93 / Chapter 5.1.2.3 --- Necessity of Addition of GLYMO --- p.94 / Chapter 5.1.3 --- Sample Characterization --- p.96 / Chapter 5.2 --- Surface Morphology --- p.97 / Chapter 5.3 --- Optical Properties of Dye-doped Zirconia Organically Modified Silicate Waveguides --- p.100 / Chapter 5.3.1 --- Modeling of Ellipsometric Values --- p.101 / Chapter 5.3.2 --- Interpretation of the Modeling Results --- p.107 / Chapter 6 --- Amplified Spontaneous Emission Based on Sol-gel Waveguides --- p.109 / Chapter 6.1 --- Experimental Setup --- p.110 / Chapter 6.2 --- Features of ASE and Fluorescence --- p.112 / Chapter 6.3 --- Prolonged Thermal Treatment Effect on Light Emission --- p.119 / Chapter 6.3.1 --- Difference in Preparation of Samples --- p.121 / Chapter 6.3.2 --- Light Emission of Samples under Extended Thermal Treatment --- p.123 / Chapter 6.3.3 --- Directionality of the Emission --- p.125 / Chapter 6.3.4 --- Some Features of the Emission --- p.127 / Chapter 7 --- Conclusion and Recommendation --- p.133 / Chapter 7.1 --- Conclusion --- p.133 / Chapter 7.2 --- Recommendation --- p.135 / Bibliography --- p.137