Wang Chengqing. / "November 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Gu Ying. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. [111]-117). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Yuen, Kin Pong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 93-95). / Yuen, Kin Pong. / Contents --- p.i / Abstract --- p.iv / Acknowledgement --- p.v / List of Figures --- p.vi / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Optically Bistable Behavior --- p.5 / Chapter 2.1 --- Bistable behavior of two component composites --- p.5 / Chapter 2.1.1 --- Formalism --- p.6 / Chapter 2.1.2 --- Results and Discussion --- p.7 / Chapter 2.1.3 --- Stability analysis --- p.9 / Chapter 2.2 --- Bistable behavior of three component composites: Nonlinear dielec- tric core embedded in a metallic shell --- p.11 / Chapter 2.2.1 --- Spectral representation of the local field --- p.11 / Chapter 2.2.2 --- The onset of bistable behavior --- p.20 / Chapter 2.2.3 --- The extinction coefficient and reflectance at normal incidence --- p.24 / Chapter 2.2.4 --- Discussion and Conclusion --- p.28 / Chapter 2.3 --- Bistable behavior of three component composites: Metallic core em- bedded in a nonlinear dielectric shell --- p.30 / Chapter 2.3.1 --- Linear response of spherical inclusions and concentric spheres --- p.31 / Chapter 2.3.2 --- Onset of bistable behavior --- p.35 / Chapter 2.3.3 --- Results and Discussion --- p.41 / Chapter 2.4 --- Possible development of the spectral representation --- p.44 / Chapter Chapter 3. --- Optical Repsonse of a Nonlinear Composite Film --- p.45 / Chapter 3.1 --- Enhanced nonlinear response of coated spheres --- p.46 / Chapter 3.2 --- Solution of nonlinear wave equation --- p.48 / Chapter 3.3 --- Results and Discussion --- p.49 / Chapter 3.4 --- Conclusion --- p.52 / Chapter 3.5 --- Transfer matrix formalism for transmittance: Possible control over the size of a photonic band gap --- p.52 / Chapter 3.5.1 --- Transfer matrix method --- p.54 / Chapter Chapter 4. --- Bounds and Estimates for Nonlinear Composites --- p.59 / Chapter 4.1 --- Linear response of spherical inclusions --- p.60 / Chapter 4.2 --- Strongly nonlinear response of spherical inclusions --- p.61 / Chapter 4.3 --- Linear response of concentric spheres --- p.64 / Chapter 4.4 --- Strongly nonlinear response of concentric spheres --- p.66 / Chapter 4.5 --- Some exactly solvable cases --- p.68 / Chapter 4.6 --- Concentric spheres with nonlinear shell embedded in a linear dielec- tric host --- p.71 / Chapter 4.7 --- Discussion and Conclusion --- p.73 / Chapter 4.8 --- Small contrast expansion --- p.75 / Chapter 4.9 --- Hashin-Shtrikman microgeometry --- p.78 / Chapter 4.10 --- Exact bounds for linear composites --- p.79 / Chapter 4.11 --- Variational approach for Hashin-Shtrikman microstructure --- p.82 / Chapter 4.12 --- Improved variational approach --- p.85 / Chapter 4.13 --- Discussion and Conclusion --- p.87 / Appendix A. Derivation of the Energy Functional --- p.88 / Chapter A.1 --- The energy functional --- p.88 / Chapter A.2 --- Effect of higher order terms to the energy functional --- p.91 / Bibliography --- p.93

Digitized by Kansas Correctional Industries

This project involves the study of optical properties of polymers doped with TRIMM (transparent refractive index matched micro-particles), and their uses in light guides. The refractive index difference between dopant and host material is small (0.02), so forward transmittance is high, and losses due to backscattering are negligible. Flexible polymer optical fibre (POF) and polymethylmethacrylate (PMMA) rods are being incorporated into an increasing range of lighting and light mixing applications. For energy efficient mixing of red, green and blue (RGB) light-emitting diodes (LEDs) to produce white light and a range of other colours, light is transmitted from the end of a light guide ('endlight'). A major problem here is solved, namely the achievement of uniform illumination, simultaneously with low losses from scattering. Light output from RGB LEDs is shown to be completely mixed by short TRIMM-doped light guides. Alternatively, long lengths of TRIMM-doped POF can be used for 'side-light'. The concentration of TRIMM for these is chosen such that light is emitted from the side walls of the guide to give even illumination along its length. A geometrical method of ray tracing in particle-doped rectangular and cylindrical light guides is derived, and Monte Carlo ray tracing simulations performed for undoped and TRIMM-doped light guides. The evolution of the distribution of ray angles, internal and external to a light guide, with propagation distance are studied. Computer simulations of angular distribution of light emitted from the wall of POF agree with measurements performed using a photogoniometer. Simulations and measurements of light output intensity and colour from RGB LED arrays when projected from the end of a mixing rod, are also presented. Colour calculations agree with photometric measurements of RGB LED output from clear and TRIMM-doped PMMA mixing rods. Results of transmittance measurements and computer simulations show that light losses are almost entirely due to Fresnel reflectance from the entrance and exit surfaces of the rods. Photogoniometer measurements of the angular distribution of light from LEDs are used as a basis for LED source models used in ray tracing simulations. Results of an investigation comparing the effect of using a smoothed LED source model instead of measurement-based models on simulated light output distributions are presented. The light output from LEDs can have sudden peaks in intensity at certain angles, resulting in distinctive patterns with clear colour separation, after mixing in clear polymer mixing rods. These caustic patterns are eliminated by using TRIMM-doped mixing rods, with a transmittance of 90% after Fresnel losses, which can be readily reduced.

<p> </p><p><p> </p></p><p><p><p> </p></p></p><p>MAX-phase materials are a new type of material class. These materials are potentiallyt echnologically important as they show unique physical properties due to the combination of metals and ceramics. In this project, spectroscopic ellipsometry in the spectral range of 0.06 eV –6.0 eV was used to probe the linear optical response of MAX-phases in terms of the complexd dielectric function <em>ε(ω) = ε1(ω) + iε2(ω<em>). </em></em>Measured data were fit to theoretical models using the Lorentz and generalized oscillator models. Data from seven different samples of MAX-phase materials were obtained using two ellipsometers. Each sample dielectric function was determined, including their infrared spectrum.</p>

Graduation date: 1967

Graduation date: 1996

Graduation date: 1994

Because the bulk optical properties of dust are largely dependent on their chemical composition, published reports from numerous dust field studies enabled us to compile observation data sets to derive the effective complex refractive indices of Saharan and Asian dust. We considered the individual mineral components as aggregates and used the Bruggeman approximation to derive the effective refractive indices. Using the results, we calculated the single-scattering properties, including phase matrix, single-scattering albedo and asymmetry factor, with a combination of the T-matrix method and an improved geometric optics method (IGOM). The single-scattering properties were averaged by the measured particle size distribution to provide bulk optical properties for radiative transfer simulations. Using a Rapid Radiative Transfer Model (RRTM), the radiative forcing of mineral dust was computed at both the top of the atmosphere and the surface. By analyzing samples from various in-situ measurements, we assumed the Saharan and Asian dust to have average volume compositions and average aspect ratios. The effective refractive indices for Saharan and Asian dust were derived based on the assumed composition models. Bulk optical properties were integrated using the modified log-normal particle size distributions. The aspect ratio assumed in this study is 1.6 for both Saharan and Asian dust. The longwave radiative (IR) forcings at the top of the atmosphere (TOA) and at the surface were found to be positive and sensitive to wavelength. The shortwave (solar) radiative forcing at TOA, was also positive, but may possibly have been due to the strong absorption components considered in the composition models.