Graduation date: 1978

The entire sixteen element scattering matrix for two parallel dielectric fibers over an angular range of θ = 5°-170° as measured from the forward θ = 0 direction has been experimentally measured using the polarization modulation technique. Experimental results were in good agreement with theory for light scattering from two parallel fibers. Measurements were made for both endside and broadside illuminations at normal incidence for fibers at various separations from 2 μm to 70 μm. Laser wavelengths used were 632.8 nm and 441.2 nm, and fiber radii were 0.400±0.002 μm, 0.370±0.002 μm, 0.428±0.002 μm, and 0.406±0.002 μm. Special care was taken to measure the fiber radii, fiber separation, and to establish the parallelism between the two fibers. Electrostatic attraction between the fibers prevented the investigation for separation below 2 μm. A vibration detection device based on two-fiber light scattering has also been suggested.

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by Lee Hon Shing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 105-106). / Text in English; abstracts in English and Chinese. / by Lee Hon Shing. / Acknowledgements --- p.i / Abstract --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Theory --- p.4 / Chapter 2.1 --- Radiation pressure on a microdroplet --- p.5 / Chapter 2.2 --- Mie scattering theory --- p.8 / Chapter 2.3 --- Laser levitation of a microdroplet --- p.11 / Chapter Chapter 3 --- Dual wavelength experiment --- p.14 / Chapter 3.1 --- Introduction --- p.15 / Chapter 3.2 --- Experiment --- p.16 / Chapter 3.2.1 --- Dual wavelength experiment --- p.16 / Chapter 3.2.2 --- Measurement of the levitating laser beam waist --- p.20 / Chapter 3.2.3 --- Measurement of the levitating laser beam profile --- p.22 / Chapter 3.3 --- Data analysis and results --- p.25 / Chapter 3.3.1 --- Deducing the size of a microdroplet by exploiting Ib(t) and Ig(t) --- p.27 / Chapter 3.3.2 --- Intensity as functions of size parameter --- p.32 / Chapter 3.3.3 --- Vertical position as a function of size parameter --- p.39 / Chapter 3.3.4 --- Comparison between experimental and theoretical results --- p.43 / Chapter 3.3.5 --- Broadening of MDRs --- p.55 / Chapter 3.3.6 --- Fine correction factor --- p.60 / Chapter Chapter 4 --- Deformation of a laser-levitated water microdroplet --- p.63 / Chapter 4.1 --- Introduction --- p.64 / Chapter 4.2 --- Experiment --- p.65 / Chapter 4.2.1 --- Dual wavelength experiment --- p.65 / Chapter 4.2.2 --- Double-slit experiment --- p.65 / Chapter 4.3 --- Data analysis and results --- p.68 / Chapter 4.3.1 --- """Cross-talk"" in dual wavelength experiment" --- p.69 / Chapter 4.3.2 --- MDR-induced oscillation of a laser-levitated water mircodroplet in dual wavelength experiment --- p.74 / Chapter 4.3.3 --- MDR-induced oscillation of a laser-levitated water mircodroplet in double-slit experiment --- p.81 / Chapter Chapter 5 --- Step-function levitation force experiment --- p.85 / Chapter 5.1 --- Introduction --- p.86 / Chapter 5.2 --- Step-function levitation force experiment --- p.87 / Chapter 5.3 --- Data analysis and results --- p.90 / Chapter 5.3.1 --- Deducing the size of the microdroplet by its vertical position --- p.91 / Chapter 5.3.2 --- Intensity curves of the step-function levitation force experiment --- p.95 / Chapter Chapter 6 --- Conclusion and future outlook --- p.99 / Chapter 6.1 --- Conclusion --- p.99 / Chapter 6.2 --- Future outlook --- p.101 / Appendix A --- p.103 / Appendix B --- p.104 / References --- p.105

Fu Pengpeng. / Thesis submitted in: August 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 98-98). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Table of Contents --- p.vii / List of Figures --- p.xii / List of Tables --- p.xiii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- A Simple 2-D Mie Scattering Model --- p.2 / Chapter 1.3 --- Topics in the Following Chapters --- p.7 / Chapter 2 --- Beam-shape Coefficients for 2-D Monochromatic Laser Beam --- p.9 / Chapter 2.1 --- General Case --- p.9 / Chapter 2.2 --- Plane Wave Case --- p.13 / Chapter 2.3 --- General Case of An Arbitrary Beam --- p.15 / Chapter 3 --- "Modified Explicit Asymptotic Formulas for the Positions, Widths of Resonances in 2-D Mie Scattering" --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.1.1 --- Positions --- p.19 / Chapter 3.1.2 --- Widths --- p.20 / Chapter 3.2 --- Positions of Resonances --- p.21 / Chapter 3.2.1 --- Derivation --- p.21 / Chapter 3.2.2 --- Numerical Comparison --- p.28 / Chapter 3.2.3 --- Separation --- p.30 / Chapter 3.2.4 --- Conclusion --- p.32 / Chapter 3.3 --- LineWidth --- p.32 / Chapter 3.3.1 --- TE Mode --- p.34 / Chapter 3.3.2 --- TM Mode --- p.36 / Chapter 3.3.3 --- Conclusion --- p.38 / Chapter 3.4 --- Conclusion --- p.39 / Chapter 4 --- Effects of Surface Perturbation of 2-D Mie Scattering --- p.42 / Chapter 4.1 --- Experimental Background --- p.42 / Chapter 4.2 --- Theoretical Derivation --- p.44 / Chapter 4.3 --- Numerical Results --- p.57 / Chapter 5 --- Conclusions and Discussions --- p.79 / Appendix --- p.81 / Chapter A --- Approximate Solution to One Matrix Equation with Pertur- bation --- p.82 / Chapter B --- Airy Functions --- p.87 / Chapter C --- Bessel Functions --- p.89 / Chapter C.1 --- Basic Properties of the Bessel Functions --- p.89 / Chapter C.2 --- Numerical Evaluation of The Bessel Functions --- p.91 / Bibliography --- p.94

An ultrasound spectrometer was designed, constructed and used to measure the frequency dependence of forward-scattered ultrasound from biological specimens. A piezoelectric transducer was continuously tuned through the frequency range of 150 to 400 MHz, producing ultrasound of the same frequency. Pulse modulation of the input signal permitted a frequency resolution of 2 MHz. The received pulse was detected at various temporal positions of its amplitude, thereby allowing measurement of the interference of the scattered and unscattered ultrasound radiation. Because of system nonlinearities all received signals were calibrated with respect to the attenuation of ultrasound in water over the system frequency range. The attenuation of water over the frequency range of 150 to 400 MHz was consequently measured and the values agreed very well with figures given in the literature. Forward-scattering experiments were performed with both physical objects and biological specimens. Sapphire spheres and plastic cylinders exhibited the expected Mie scattering resonant structure. Planar glass plates showed the commonly observed Fabry-Perot resonant structure. Measurement of the resonant frequencies agreed well with theoretically-predicted values. The biological specimens consisted of various cell suspensions of densities on the order of 100 million cells per milliliter. Because of the high cell densities necessary for signal measurement, only signal attenuation was measured. No resonant structure was observed. Synchronized growth colonies of mouse leukemia cells were investigated at both the plateau and log stages of cell growth. The attenuation of melanoma cells was measured with and without melanin. Also, various lines of tumor cells were investigated. For all of these cell suspensions, the attenuation in dB/mm increased linearly with the logrithm of frequency. Though the slope of the attenuation-frequency curves varied from cell line to cell line, the variation for the same cells under different biological conditions was not appreciable. For all of the above cell lines, no attenuation fell out of the range of 5 to 55 dB/mm.

Exact and distance-independent expressions for beam-shape coefficients (BSC's) in various cases are obtained. For a weakly focused beam in the two-dimensional (three-dimensional) case, the expression is shown equal (linearly related) to the value of the beam field at the distance of m/k ( ll+1 /k) from the origin, where m( l) is the azimuthal (principal) angular momentum number and k is the wavenumber. This provides a rigorous foundation for and a better understanding of the localization principle of van de Hulst. Furthermore, it gives corrections to the principle if the beam is more focused. With the knowledge of the asymptotic behavior of the positions and widths (or quality value) for the morphology-dependent resonances (MDR's) in Mie's scattering, the results are applied to discuss and answer questions regarding the excitation of high-Q MDR's by good collimated wave beams focused at positions essentially off the surface of the sphere. / Fu, Pengpeng = 波東形狀係數、局域化原理及米氏散射中的共振激發 / 傅芃芃. / Adviser: Hon Meng Lai. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 75-81). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Fu, Pengpeng = Bo dong xing zhuang xi shu, ju yu hua yuan li ji Mi shi san she zhong de gong zhen ji fa / Fu Pengpeng.

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A system consisting of a sphere sitting on a clean mirror was modeled as a two particle system: the real sphere and its image sphere, treating the mirror as a conducting plane. When the system was irradiated with a plane-polarized collimated laser beam with varying angles of incidence, the scattering from each particle was assumed to follow Mie's solution for light scattering by a sphere. Phase difference between the scattering by the real sphere and the one by its image sphere was assessed by the geometry of the model. The far field solutions from each of the spheres were added to yield a phase dependent intensity function. Another model assumed no phase correlation between the two and the intensities from each spheres were added. Also discussed is the Double Interaction Mode, which takes the mirror-sphere separation into consideration. These theoretical results were converted to Bidirectional Reflectance Distribution Functions (BRDF). The theoretical as well as the empirical surface scattering from a good quality optical surface was introduced. The BRDF values thus calculated were added to the background scattering by the mirror since no interaction was assumed between the spheres and the rough metallic surface of the mirror. The test sample was prepared with polystyrene spheres with the nominal diameter of 0.984 μm on a high quality aluminum mirror. The BRDF data from this sample with 6328Å and 4416Å were compared with the one obtained with the model described above. The comparison strongly indicated that there existed no phase correlation between the scatterings by the two spheres. Determination of the sphere size and practical applicability for estimating the sphere number density on the surface are also discussed.

The objectives of this study were to implement a system to measure mixing in nonreacting flows and to study the mass transfer characteristics of two actively excited turbulent jets. This thesis describes the acquisition and analysis of phase-locked concentration field data using planar Mie scattering from smoke particles and planar laser-induced fluorescence of acetone. Both techniques were shown to be effective in providing information for the actively excited nozzles. However, the laser-induced fluorescence technique was superior for revealing detail in the flowfield structure. Spatial mode control techniques were applied to a triangular nozzle with vibrating actuators as the three sides and a swirl nozzle with pulsating tangential air jets. The effect of the different spatial modes on jet column development and the far fields of both nozzles is presented. Two- and three-dimensional iso-intensity contours, showing the relative intensity of light scattered by the nozzle fluid marker, were generated to show the flow structure. The areas inside the iso-intensity contours in the far field were also measured to determine relative effectiveness of nozzle fluid transport. Large scale structures were visible in the three-dimensional iso-intensity contours from both nozzles. In addition, the transport of seeded nozzle fluid was enhanced by the spatial mode excitation for both nozzles. Spatial mode excitation was also able to affect the shape of the far field contour. In particular, the first counterrotating helical mode, m=±1, generated the greatest effect on nozzle fluid transport and the most pronounced elliptical contour shape in the far field. / Master of Science