Typescript. Includes bibliographical references.

Recent experiments with optical fibers have reached a remarkable development for optical communication spectroscopy as well as a medical technology. Hollow optical fibers are required for optical communications. The measurement of the transmission of light through fibers can provide information about the fiber quality and about the far-field energy which radiates from the fiber end. We used five flexible hollow fused quartz fibers to study laser beam propagation down the fiber axis. Five different refractive index fluids were prepared and inserted into the fiber core to measure the transmitted intensity as a function of core property. The plots of the normalized, relative transmitted intensity measured as a function of the beam insertion point show the dependence of the transmitted intensity as a function of fiber diameter and refractive index fluid.

This thesis describes a detailed investigation into the process of laser-wakefield acceleration (LWFA) for the generation of high-energy electron beams using the hydrogen-filled capillary discharge waveguide. In only the second experiment to be performed using the newly commissioned Astra-Gemini laser at the Rutherford Appleton Laboratory, electron beams were accelerated to energies greater than 0.5 GeV by laser pulses of energy 2.5J and peak power of 30T\~T. The injec- tion and acceleration of electron beams was seen to depend on the state of the plasma channel for axial electron densities less than 2.5 x 1018 cm -3. With the aid of simulations performed using the code WAKE it was found that the plasma channel allows the laser pulse to maintain its self-focussed spot size along the length of the capillary even below the critical power for self-guiding. It was found that the threshold laser energy required for the production of elec- tron beams was reduced by the use of an aperture placed early in the laser system. This was attributed to the increased energy contained in the central part of the focal spot of the laser. A short paper on this work was published in Physical Review Special Topics - Accelerators and Beams and a longer paper was published in the New Journal of Physics. Transverse interferometry was used to measure the electron density of the plasma channel used in the Astra-Gemini experiments. An imaging system was devised which used cylindrical optics to increase the field of view of the capillary longitudinally, whilst maintaining the trans- verse resolution. The measured properties were consistent with previous measurements made by Gonsalves et al. [J]. The observed longitudinal variations in the plasma channel parameters were not found to be significant enough to affect the injection process.

Hui Yat Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 106-108). / Acknowledgments / Abstract / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Theory / Chapter 2.1 --- Optical Waveguide --- p.4 / Chapter 2.1.1 --- Optical Waveguide Classification / Chapter 2.1.2 --- Theoretical Analysis of 2-dimensional Step Index Waveguides / Chapter 2.2 --- Optical Waveguides Measurement --- p.18 / Chapter 2.2.1 --- Refractive Index Measurement / Chapter 2.2.2 --- Loss Measurement / Chapter 2.3 --- Ion Implantation and Annealing --- p.36 / Chapter 2.4 --- Refractive Index Change --- p.40 / Chapter 3. --- Equipments and Their Experimental Setup / Chapter 3.1 --- Light Source-Laser Diode --- p.42 / Chapter 3.2 --- Ellipsometry Measurement System --- p.45 / Chapter 3.2.1 --- Ellipsometry Measurement System and its Existing Problems / Chapter 3.2.2 --- Improvement of the Original System / Chapter 3.2.3 --- System Calibration / Chapter 3.3 --- Reflectance Measurement System --- p.51 / Chapter 3.3.1 --- System Design and Setup / Chapter 3.3.2 --- System Calibration / Chapter 3.4 --- End-Coupling Measurement System --- p.56 / Chapter 3.4.1 --- System Setup / Chapter 3.4.2 --- System Calibration / Chapter 4. --- Experiment / Chapter 4.1 --- Samples Preparation --- p.77 / Chapter 4.2 --- Refractive Index Measurement by Ellipsometer --- p.80 / Chapter 4.3 --- Refractive Index Measurement by Reflectance --- p.84 / Chapter 4.4 --- Waveguide Measurement --- p.88 / Chapter 4.4.1 --- Fiber-Waveguide Coupling / Chapter 4.4.2 --- Lens-Waveguide Coupling / Chapter 5. --- Results and Discussion / Chapter 5.1 --- Refractive Index Change and Waveguide Formation --- p.94 / Chapter 5.2 --- Mechanism of Refractive Index Change --- p.100 / Chapter 6. --- Conclusion --- p.103 / Chapter 7. --- Improvement and Extension --- p.105 / Reference --- p.106 / Appendices / Chapter A. --- Thick.m --- p.VI / Chapter B. --- Distrib.m --- p.IX

by Choi Kup Sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references. / Acknowledgement / Abstract / Chapter 1. --- Introduction --- p.1-1 / Chapter 1.1 --- Introduction --- p.1-1 / Chapter 1.2 --- References --- p.1-6 / Chapter 2. --- Theory of Optical Waveguides --- p.2-1 / Chapter 2.1 --- Theory of Planar Slab Waveguides --- p.2-2 / Chapter 2.2 --- Theory of Channel Dielectric Waveguides --- p.2-13 / Chapter 2.2.1 --- Marcatili's Method --- p.2-13 / Chapter 2.2.2 --- Effective Index Method --- p.2-20 / Chapter 2.3 --- References --- p.2-24 / Chapter 3. --- A Numerical Method for Optical Waveguides --- p.3-1 / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- two-dimensional Fourier Series Expansion Method --- p.3-2 / Chapter 3.3 --- References --- p.3-13 / Chapter 4. --- Theory of Directional Couplers --- p.4-1 / Chapter 4.1 --- Dual-Channel Coupler --- p.4-1 / Chapter 4.2 --- Multi-channel Directional Coupler --- p.4-8 / Chapter 4.3 --- References --- p.4-9 / Chapter 5. --- Waveguide Formation by Ion Implantation --- p.5-1 / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Physics of Ion Implantation --- p.5-3 / Chapter 5.3 --- Lattice Damage and Annealing --- p.5-5 / Chapter 5.3.1 --- Lattice Damage --- p.5-5 / Chapter 5.3.2 --- Annealing --- p.5-6 / Chapter 5.4 --- Index Change due to Implantation --- p.5-8 / Chapter 5.5 --- Waveguide Processing Techniques --- p.5-10 / Chapter 5.5.1 --- Photolithography --- p.5-10 / Chapter 5.5.2 --- Processing Techniques --- p.5-11 / Chapter 5.6 --- References --- p.5-13 / Chapter 6. --- Optical Loss in Waveguides --- p.6-1 / Chapter 6.1 --- Loss Mechanisms in Optical Waveguides --- p.6-1 / Chapter 6.2 --- Principle of Propagation Loss Measurement --- p.6-4 / Chapter 6.2.1 --- Cut-back Method --- p.6-5 / Chapter 6.2.2 --- Scattering Light Method --- p.6-7 / Chapter 6.2.3 --- Fabry-Perot Interference Technique --- p.6-9 / Chapter 6.3 --- References --- p.6-16 / Chapter 7. --- Fabrication and Measurement of Optical Waveguides --- p.7-1 / Chapter 7.1 --- Fabrication of Optical Waveguides --- p.7-1 / Chapter 7.1.1 --- Fabrication of waveguides in GaAs by MeV oxygen ion implantation --- p.7-1 / Chapter 7.1.2 --- Waveguide End Facet Preparation --- p.7-4 / Chapter 7.2 --- Measurement of Optical Waveguides --- p.7-7 / Chapter 7.2.1 --- Laser Sources --- p.7-7 / Chapter 7.2.2 --- Guided Wave Excitation --- p.7-10 / Chapter 7.2.3 --- Intensity Profile Measurement --- p.7-17 / Chapter 7.2.4 --- Coupling Coefficient Measurement --- p.7-20 / Chapter 7.2.5 --- Propagation Loss Measurement --- p.7-25 / Chapter 7.3 --- References --- p.7-34 / Chapter 8. --- Results and Discussions --- p.8-1 / Chapter 8.1 --- Near Field Pattern Measurement --- p.8-1 / Chapter 8.2 --- Discussion on the Index Change of the Implanted GaAs --- p.8-5 / Chapter 8.3 --- Propagation Loss Measurement --- p.8-8 / Chapter 8.4 --- Observation of Optical Coupling in Directional Coupler --- p.8-14 / Chapter 8.5 --- References --- p.8-19 / Chapter 9. --- Conclusion --- p.9-1 / Chapter 10. --- Improvement and Extension --- p.10-1 / Appendix 1 Evaluation of the product〈n2 φuvφu'v'〉 --- p.A1-1 / Appendix 2 Transmission of Lossy Fabry-Perot Cavity --- p.A2-1 / Appendix 3 Effective Index versus Index Difference --- p.A3-1 / Appendix 4 Effect of Temperature on the Transmission of a Fabry-Perot Cavity --- p.A4-1 / Appendix 5 Evaluation of An from the Near Field Pattern --- p.A5-1

Wong, Chi Yan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 134-149). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Animals have evolved diverse strategies to control solar and thermal radiations so that they can better adapt to their natural habitats. Structured materials utilized by these animals to control electromagnetic waves often surpass analogous man-made optical materials in both sophistication and efficiency. Understanding the physical mechanism behind these structured materials of nature inspires one to create novel materials and technologies. Our optical and thermodynamic measurements of insects (Saharan silver ants and cocoons of the Madagascar comet moth) living in harsh thermal environments showed their unique ability to simultaneously enhance solar reflectivity and thermal emissivity, and to maintain a cool body temperature. Saharan silver ants, Cataglyphis bombycina, forage on the desert surface during the middle of the day. The ants’ conspicuous silvery glance is caused by a coating of hairs with unique triangular cross-sections. The hair coating enhances not only the reflectivity of the ant’s body surface in the visible and near-infrared range of the spectrum, where solar radiation culminates, but also the emissivity of the ant in the mid-infrared. The latter effect enables the animals to efficiently dissipate heat back to the surroundings via blackbody radiation under full daylight conditions. The fibers produced by the wild comet moth, Argema mittrei, are populated with a high density of air voids that have a random distribution in the fiber cross-section but are invariant along the fiber. These filamentary air voids strongly back-scatter light in the solar spectrum, which, in combination with the fibers’ intrinsic high emissivity in the mid-infrared, enables the cocoon to function as an efficient radiative-cooling device, preventing the pupa inside from overheating. The reduced dimensionality of the random voids leads to strong optical scattering in the transverse direction of the cocoon fibers. This enables tightly confined optical modes to propagate along the fibers via transverse Anderson localization. We made the first observation of transverse Anderson localization in a natural fiber and further demonstrated light focusing and image transport in the fibers. This discovery opens up the possibility to use wild silk fibers as a biocompatible and bioresorbable material for transporting optical signals and images. Drawing inspirations from these discoveries, we designed and developed high-throughput fabrication processes to create coatings and fibers with passive radiative-cooling properties. The radiative-cooling coatings consist of various nanoparticles imbedded within a silicone thin film. The sizes and materials of the nanoparticles were chosen to provide simultaneously high solar reflectivity and thermal emissivity. The coating has been implemented in two site studies on real roofs and has demonstrated reduced roof temperature by up to 30oC in the summer and associated reduction of electricity usage by up to 30%. We also made biomimetic fibers from regenerated silk fibroin and a thermoplastic using wet spinning. Spectroscopic measurements showed that these man-made fibers exhibit exceptional optical properties for radiative-cooling applications.

石墨烯，由單層碳原子緊密排列成蜂巢狀的晶體結構，擁有卓越的電學性能和光學性能。這些優異的性能包括：極高的電子遷移率，超寬的吸收光譜，栅電壓調控光躍遷性質，飽和吸收性質。石墨烯的獨特光學性質已經被用來製造多種高性能的光電器件，包括光電探測器， 飽和吸收器， 光調製器和四波混頻的介質。同時，石墨烯的製造工藝可以與現代半導體標準製造工藝相兼容， 加上它穩定的化學性質， 石墨烯非常有潛力在未來半導體工業發展中發揮重要作用。 / 單層石墨烯可以透過97.7% 垂直入射的光，吸收2.3% 左右，並且吸收的光頻非常寬。雖然對於單層碳原子結構，這個吸收率很大，但是在一些器件中，我們需要更高的光吸收率。爲了突破單層石墨烯光吸收的極限，一種可行的辦法是延長石墨烯與光相互作用的長度。將單層石墨烯轉移到長的硅波導上，可以延長石墨烯與光作用的長度。除了線性光吸收特性，石墨烯的飽和吸收特性也有廣泛的應用。很多脉衝激光發生器是利用被動鎖模的原理，即激光器中的飽和吸收器將連續的光波轉變成頻率固定的脉衝。石墨烯已經被證明是恢復速度快、調製範圍大的飽和吸收器。 但是，石墨烯和硅波導結合作為飽和吸收器的特性和它們的應用還從來沒有被研究過。 / 在論文中，我們研究了石墨烯轉移到硅波導后的線形光學性質和飽和吸收特性。首先我們討論了石墨烯轉移的方法，然後我們通過實驗調查了石墨烯在貴波導上的線形光學性質和飽和吸收特性。爲了研究石墨烯/硅波導在被動鎖模光纖激光器中的作用，我們利用石墨烯/硅波導作為飽和吸收器製造了一個光纖激光器。之後，通過在激光腔體中加入可调滤波器， 我們用成功的演示了波長可調製被動鎖模光纖激光器。 / 多脉衝激光光源在光纖通信，測量學和光學器件性能鑒定中有重要作用。所以研究緊湊、穩定並且價格實惠的多脉衝鎖模激光器非常有意義。爲了實現多脉衝鎖模光纖激光器，我們將硅基濾波器和石墨烯/硅波導集成在一起. 在論文中，我們設計并優化了能被應用於多脉衝鎖模激光器的寬帶寬濾波器凹凸光栅。 / Graphene, a single 2D sheet of carbon atoms arranged in a honeycomb lattice, has superior electrical and optical properties including extremely high charge-carrier mobility, broadband optical absorption, gate-variable optical transitions and saturable absorptions. Its unique optical properties have led to a range of promising optoelectronic devices, such as photo detectors, saturable absorbers, optical modulators and nonlinear media for four-wave mixing. Graphene’s complementary metal-oxide-semiconductor (CMOS) integration processes at wafer scale and its electrochemical stability make it a promising candidate for post CMOS electronics. / Monolayer grapheme transmits 97.7% of the normal incident light and absorbs 2.3%, independent of wavelength. In order to overcome the challenge of limited absorption of a monolayer and better exploit graphene optical properties, a long interaction length is needed. By integrating graphene directly on top of silicon waveguides, longer light/graphene interactions can be achieved. In addition to the linear optical properties of the graphene, its saturable absorption also finds useful applications. Many ultra-short pulse lasers are based on passive mode-locking, where a saturable absorber turns continuous wave output of the laser into a train of optical pulses. And graphene has been shown to make an excellent saturable absorber. However, the saturable absorption behavior of graphene-silicon wavguides and their applications have never been studied. / In this thesis, the linear and saturable absorption of monolayer graphene films transferred onto silicon waveguide are investigated. The transfer process of monolayer graphene to silicon waveguides is studied and linear and saturable absorption measurements are carried out. To investigate applications of graphene-silicon waveguides, a passive mode-lock fiber lasers in which graphene-silicon waveguides act as saturable absorbers to mode-lock pulses is constructed. By adding a tunable filter in cavity, a tunable mode-locked fiber laser based on graphene-silicon waveguide is demonstrated. / Multi-wavelength pulse sources are important for applications including optical fiber communication, instrumentation, and photonic component characterization. The availability of compact, reliable and cost effective multi-wavelength mode-locked lasers is of great importance. We also hope to build multiwavelength mode-locked fiber lasers by integrating CWDM silicon filters with graphene-silicon waveguides. The design process and optimization of a silicon filter called echelle grating is demonstrated. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Shi, Zerui. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Abstracts also in Chinese. / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Photonic Integrated Circuit (PIC) --- p.1 / Chapter 1.2 --- Silicon on Insulator (SOI) Photonics --- p.3 / Chapter 1.2.1 --- SOI Waveguides --- p.5 / Chapter 1.2.2 --- SOI Waveguide Based Wavelength Division Multiplexing --- p.6 / Chapter 1.3 --- Graphene Photonics --- p.9 / Chapter 1.3.1 --- Band Structure of Monolayer Graphene --- p.9 / Chapter 1.3.2 --- Optical Absorption of Graphene --- p.13 / Chapter 1.3.3 --- Graphene Based Passive Mode-Locked Fiber Lasers --- p.18 / Chapter 1.4 --- Motivation --- p.22 / Chapter 1.5 --- Thesis Outline --- p.23 / Chapter 1.6 --- Reference --- p.24 / Chapter Chapter 2: --- Optical Properties of Graphene-Silicon Waveguides --- p.27 / Chapter 2.1 --- Fabrication and Transfer Process of Graphene-Silicon Waveguides --- p.28 / Chapter 2.1.1 --- Fabrication of SOI Waveguides --- p.28 / Chapter 2.1.2 --- Transfer Process of Monolayer Graphene onto SOI Waveguides --- p.29 / Chapter 2.2 --- Linear Optical Absorption of Graphene-Silicon Waveguides --- p.35 / Chapter 2.2.1 --- Introduction to Photoexcitation in Monolayer Graphene --- p.35 / Chapter 2.2.2 --- Experimental Results of Linear Absorption --- p.37 / Chapter 2.3 --- In-Plane Saturable Absorption of Graphene-Silicon Waveguides --- p.38 / Chapter 2.3.1 --- Experimental Result of In-Plane Saturable Absorption of Graphene-Silicon Waveguides --- p.39 / Chapter 2.3.2 --- Mechanism of Saturable Absorption of Graphene-Silicon Waveguides --- p.42 / Chapter 2.4 --- Summary --- p.44 / Chapter 2.5 --- Reference --- p.45 / Chapter Chapter 3: --- Hybrid Graphene-Silicon Waveguides Based Mode-Locked Fiber Lasers --- p.47 / Chapter 3.1 --- Background of Graphene Based Mode-Locked Fiber Lasers --- p.47 / Chapter 3.1.1 --- Passive Mode-Locked Lasers Fundamentals --- p.47 / Chapter 3.1.2 --- Review of Recent Works of Graphene Based Mode-Locked Fiber Lasers . --- p.52 / Chapter 3.2 --- Hybrid Graphene-Silicon Waveguides Based Mode-Locked Fiber Lasers --- p.55 / Chapter 3.2.1 --- Experimental Set Up and Results --- p.55 / Chapter 3.2.2 --- Discussion --- p.59 / Chapter 3.3 --- Tunable Graphene-Silicon Waveguides Based Mode-Locked Fiber Lasers --- p.62 / Chapter 3.4 --- Summary --- p.66 / Chapter 3.5 --- Reference --- p.66 / Chapter Chapter 4: --- Conclusion and Future Work --- p.68 / Chapter 4.1 --- Conclusion --- p.68 / Chapter 4.2 --- Future Work --- p.69 / Chapter 4.2.1 --- Design and Simulation Results of Echelle Grating --- p.69 / Chapter 4.2.2 --- Optimization and Experiment Results of Echelle Gratings --- p.77 / Chapter 4.2.3 --- Integration of Echelle Grating with SOI Waveguides --- p.82 / Chapter 4.3 --- Summary --- p.84 / Chapter 4.4 --- Reference --- p.85 / Chapter APPENDIX A: --- PUBLICATION LIST --- p.86 / Chapter APPENDIX B: --- LIST OF FIGURES --- p.87 / Chapter APPENDIX C: --- LIST OF TABLES --- p.91 / Chapter APPENDIX D: --- atlab Code of Simulation of Echelle Grating --- p.92

Shi Lei = 溶凝膠分佈反饋波導激光器之光學性質的研究 / 石蕾. / "September 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 150-171) / 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. / Shi Lei = Rong ning jiao fen bu fan kui bo dao ji guang qi zhi guang xue xing zhi de yan jiu / Shi Lei.

Zhang Ailing. / "September 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.