by Chan Lai Yin, Simon. / "December 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / 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.

Quantum Key Distribution (QKD) employs the laws of quantum mechanics for the purpose of cryptography. Two parties, commonly called Alice and Bob, are able to share a random key which is used to encrypt a message. Any eavesdropper trying to intercept their key will have to make measurements, thereby disturbing the system. This can be detected by Alice and Bob and they will then discard their key. Polarisation encoded QKD protocols use the polarisation of single photons as qubits to generate a cryptographic key. This can be implemented using a fibre optic link between Alice and Bob but the polarisation of light is altered when passed through a fibre due to birefringence caused by asymmetries in the fibre. This causes refractive differences for orthogonal components of the state of polarisation of light, so the polarisation is rotated as the photon is transmitted through the fibre. If the fibre is fixed, the change of polarisation will be unique and constant. This can be compensated by rotating each photon appropriately to its original state. Under typical environmental conditions, such as temperature changes and vibrations, the birefringence effects vary and should be compensated in real time. Therefore, an active polarisation controller is needed in order to maintain the state of polarisation of each qubit. An investigation was done to first track how the state of polarisation changes over time in a natural environment. Both wavelength-division multiplexing and time-division multiplexing were investigated as testing methods for the compensation system. A time-division multiplexed system was developed to compensate the changes in polarisation. Since QKD protocols such as BB84 and B92 utilise two non-orthogonal bases, two polarisation controllers are usually used for compensation. However, by using a search algorithm, one polarisation controller was able to isolate the plane on the Poincaré sphere that passes through both bases, thus compensating non-orthogonal states with one device. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.

by Kit Chan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgment --- p.v / Table of Contents --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Ultrashort Pulses Generation in Semiconductor Lasers and Fiber Lasers --- p.2 / Chapter 1.2 --- Wavelength Tunable Pulse Generation From Semiconductor Laser --- p.4 / Chapter 1.3 --- Wavelength Tunable Pulse Generation from Erbium Doped Fiber Lasers --- p.7 / Chapter 1.4 --- Structure of the thesis --- p.8 / Reference --- p.10 / Chapter 2. --- Principles and Theories --- p.14 / Chapter 2.1 --- Principle of Synchronous Injection Seeding --- p.15 / Chapter 2.2 --- Principle of Compensated Dispersive Tuning in Self-seeding Configuration --- p.18 / Chapter 2.3 --- Principle of Compensated Dispersive Tuning in Actively Mode-Locked Fiber Laser --- p.20 / Chapter 2.4 --- Principle of Wavelength Switching in Actively Mode-Locked Fiber Laser with Fiber Bragg Gratings in Cascaded Configuration --- p.24 / Chapter 3. --- Electrical Wavelength Tunable Pulses Generated From Two-way Synchronous Injection Seeded Fabry-Perot Laser Diodes --- p.26 / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Experimental Details --- p.28 / Chapter 3.3 --- Results and Discussion --- p.31 / Chapter 3.4 --- Summary --- p.38 / Reference --- p.39 / Chapter 4. --- Compensated Dispersive Tuning In Self-Seeding Configuration --- p.41 / Chapter 4.1 --- Introduction --- p.42 / Chapter 4.2 --- Experimental Details --- p.43 / Chapter 4.3 --- Results and Discussion --- p.46 / Chapter 4.4 --- Summary --- p.55 / Reference --- p.56 / Chapter 5. --- Compensated Dispersive Tuning in Actively Mode-Locked Fiber Laser --- p.57 / Chapter 5.1 --- Introduction --- p.58 / Chapter 5.2 --- Experimental Details --- p.59 / Chapter 5.3 --- Results and Discussion --- p.61 / Chapter 5.4 --- Summary --- p.69 / Reference --- p.70 / Chapter 6. --- Compensated Dispersive Tuning in Actively Mode-Locked Fiber Laser Using Linearly Chirped Fiber Bragg Grating --- p.71 / Chapter 6.1 --- Introduction --- p.72 / Chapter 6.2 --- Experimental Details --- p.73 / Chapter 6.3 --- Results and Discussion --- p.75 / Chapter 6.4 --- Summary --- p.77 / Reference --- p.78 / Chapter 7. --- Electrically Wavelength Switching in Actively Mode- locked Fiber Laser Using Fiber Bragg Gratingsin Cascaded Configuration --- p.79 / Chapter 7.1 --- Introduction --- p.80 / Chapter 7.2 --- Experimental Details --- p.81 / Chapter 7.3 --- Results and Discussion --- p.83 / Chapter 7.4 --- Summary --- p.87 / Reference --- p.88 / Chapter 8. --- Conclusion and Future Works --- p.89 / Chapter 8.1 --- Conclusion --- p.89 / Chapter 8.2 --- Possible Future Works --- p.92 / Appendices --- p.A-l / Chapter Appendix A. --- List of Publications --- p.A-l / Chapter Appendix B. --- List of Figures --- p.A-2

Lee Ka-lun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgment --- p.v / Table of contents --- p.vi / List of figure --- p.viii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Generation of picosecond pulses from semiconductor laser and fiber laser --- p.2 / Chapter 1.2. --- Wavelength tunable pulse generated from semiconductor laser --- p.5 / Chapter 1.3. --- Wavelength tunable pulse generated from erbium doped fiber laser --- p.7 / Chapter 1.4. --- Structure of the thesis --- p.8 / Chapter 2. --- Principles and Theories --- p.13 / Chapter 2.1. --- Principle of dispersion tuning --- p.15 / Chapter 2.1.1. --- Dependence on the strength of dispersion --- p.16 / Chapter 2.1.2. --- Wavelength selection in time domain --- p.18 / Chapter 2.1.3. --- Compensated dispersion tuning in a dispersion balanced fiber ring --- p.20 / Chapter 2.2. --- Optical gating using Nonlinear Optical Loop Mirror (NOLM) incorporated with nonlinear element --- p.22 / Chapter 2.3. --- Principle of compensated dispersion tuning in harmonically mode- locked fiber laser incorporated with linearly chirped fiber grating (LCFG) --- p.26 / Chapter 2.4. --- Principle of compensated dispersion tuning in self-seeding configuration --- p.29 / Chapter 2.5. --- Principle of dual-wavelength operation in harmonically mode-locked fiber laser --- p.31 / Chapter 3. --- Preliminarily experimental study --- p.33 / Chapter 3.1. --- Wavelength selection using strong and weak dispersive medium --- p.34 / Chapter 3.2. --- NOLM as a fast optical modulator --- p.38 / Chapter 4. --- Self-compensated dispersion-tuning in mode-locked fiber laser using bi- directional transit in a linearly chirped fiber grating --- p.41 / Chapter 4.1. --- Introduction --- p.42 / Chapter 4.2. --- Experimental Details --- p.43 / Chapter 4.3. --- Results and discussion --- p.47 / Chapter 4.4. --- Summary --- p.54 / Chapter 5. --- Generation of wavelength tunable pulses from a self-seeded semiconductor laser using an optically controlled Nonlinear Optical Loop Modulator (NOLM) incorporated with a Semiconductor Optical Amplifier (SOA) --- p.56 / Chapter 5.1. --- Introduction --- p.57 / Chapter 5.2. --- Experimental Details --- p.58 / Chapter 5.3. --- Results and discussion --- p.64 / Chapter 5.4. --- Summary --- p.71 / Chapter 6. --- Alternate and Simultaneous Generation of 1 GHz Dual-Wavelength Pulses from an Electrically-Tunable Harmonically Mode-locked Fiber Laser --- p.74 / Chapter 6.1. --- Introduction --- p.75 / Chapter 6.2. --- Experimental Details --- p.76 / Chapter 6.3. --- Results and discussion --- p.80 / Chapter 6.4. --- Summary --- p.87 / Chapter 7. --- Conclusion and Future works --- p.89 / Chapter 7.1. --- Conclusion --- p.89 / Chapter 7.2. --- Future works --- p.93 / Appendix --- p.A-l / List of Publication --- p.A-l

by Sui-Pan Yam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Abstract also in Chinese. / Acknowledgements --- p.V / Abstract --- p.VI / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter 1.1) --- Tunable Multi-Wavelength Optical Sources --- p.1 -1 / Chapter 1.2) --- All-Optical Switching --- p.1 -3 / Chapter 1.2.1) --- Nonlinear Effect / Chapter 1.2.2) --- Special Design of the Laser Structure / Chapter 1.2.3) --- Self-Injection Seeding of Fabry-Perot Laser Diode / Chapter 1.3) --- About This Project --- p.1-6 / Chapter Chapter 2 --- Basic Theory --- p.2-1 / Chapter 2.1) --- Mechanism of Gain-Switching --- p.2-1 / Chapter 2.1.1) --- General Description / Chapter 2.1.2) --- "Optical Pulsewidth, Spectra, and Frequency Chirping of Gain-Switched Pulses" / Chapter 2.2) --- Mechanism of Self-Injection Seeding --- p.2-8 / Chapter 2.2.1) --- General Description / Chapter 2.2.2) --- Dynamics of Single-Mode Formation / Chapter 2.2.3) --- Frequency Evolution of the Laser Diode for Cavity Mode Selection / Chapter 2.2.4) --- Turn-On Delay Time Jitter (TOJ) / Chapter 2.3) --- Mechanism of Injection Seeding --- p.2-17 / Chapter 2.3.1) --- General Description / Chapter 2.3.2) --- The Model of Weak Injection / Chapter 2.3.3) --- The Model of Strong Injection / Chapter Chapter 3 --- Single- and Multi-wavelength Optical Pulses Generated by a Diffraction Grating --- p.3-1 / Chapter 3.1) --- Introduction --- p.3-1 / Chapter 3.2) --- Basic Principle --- p.3-2 / Chapter 3.3) --- Experimental Setup --- p.3-5 / Chapter 3.4) --- Results and Discussion --- p.3-7 / Chapter 3.4.1) --- Spectral Characteristics Analysis / Chapter 3.4.2) --- Individually Access of the Four-Wavelength Output / Chapter 3.4.3) --- The Optical Pulsewidth Characteristics / Chapter 3.4.4) --- Discussion / Chapter 3.5) --- Summary --- p.3-14 / Chapter Chapter 4 --- Using a Highly Dispersive Fiber for Tunable Multi-Wavelength Pulse Generation --- p.4-1 / Chapter 4.1) --- Introduction --- p.4-1 / Chapter 4.2) --- Basic Principle --- p.4-2 / Chapter 4.3) --- Experimental Setup --- p.4-5 / Chapter 4.4) --- Experimental Results --- p.4-7 / Chapter 4.4.1) --- Spectral and Temporal Characteristics / Chapter 4.4.2) --- Wavelength Tuning / Chapter 4.4.3) --- Individually Access of Two Wavelength Channels / Chapter 4.4.4) --- Multi-Wavelength Generation / Chapter 4.5) --- Summary --- p.4-13 / Chapter Chapter 5 --- Comparison of Two Self-Seeding Configurations --- p.5-1 / Chapter 5.1) --- Introduction --- p.5-1 / Chapter 5.2) --- Polarization Sensitivity --- p.5-1 / Chapter 5.3) --- Stability --- p.5-2 / Chapter 5.4) --- Tunability --- p.5-2 / Chapter 5.5) --- Simplification --- p.5-3 / Chapter 5.6) --- Summary of the advantages and disadvantages of Two Configurations --- p.5-4 / Chapter Chapter 6 --- All-Optical Wavelength Switching achieved by Self-Seeding and External Injection-Seeding --- p.6-1 / Chapter 6.1) --- Introduction --- p.6-1 / Chapter 6.2) --- Experimental Setup --- p.6-2 / Chapter 6.3) --- Results and Discussion --- p.6-4 / Chapter 6.3.1) --- Spectral Characteristics / Chapter 6.3.2) --- The Optical Pulsewidth / Chapter 6.3.3) --- The Optical Switching Behaviors / Chapter 6.3.4) --- The Detail Information of Switching / Chapter 6.3.5) --- Optical Power / Chapter 6.4) --- Summary --- p.6-10 / Chapter Chapter 7 --- A Novel Self-Injection Seeding Scheme --- p.7-1 / Chapter 7.1) --- Introduction --- p.7-1 / Chapter 7.2) --- Basic Principle --- p.7-2 / Chapter 7.3) --- Experimental Setup --- p.7-9 / Chapter 7.4) --- Results and Discussion --- p.7-11 / Chapter 7.4.1) --- Spectral and Temporal Characterizations of Two-Wavelength Switching / Chapter 7.4.2) --- Different Wavelength Selection / Chapter 7.4.3) --- Operation Frequency Against the Fiber Length / Chapter 7.4.4) --- Multi-Wavelength Generation / Chapter 7.5) --- Discussion --- p.7-20 / Chapter 7.6) --- Summary --- p.7-22 / Chapter Chapter 8 --- Comparison of Switching Methods --- p.8-1 / Chapter 8.1) --- Introduction --- p.8-1 / Chapter 8.2) --- Switching between Self-Seeding and Injection-Seeding --- p.8-1 / Chapter 8.3) --- Switching by Self-Seeding of a F-P Laser Diode --- p.8-2 / Chapter 8.4) --- Summary --- p.8-3 / Chapter Chapter 9 --- Conclusion --- p.9-1 / References / Figure Captions / Appendix 一 Equipment Descriptions / List of Accepted and Submitted Publications

by Ka-Suen Lee. / "June 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / 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.

The purpose of this study is to determine the relationship of light wave length to tissue differentiation in sunflower seedlings.

by Chow Kin Kee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgment --- p.v / Table of Contents --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Ultra-short Pulse Generation in Semiconductor Lasers --- p.2 / Chapter 1.2 --- Wavelength Selection and Switching in Short Pulses Generated from Semiconductor Laser --- p.4 / Chapter 1.3 --- Structure of the Thesis --- p.6 / Reference --- p.8 / Chapter 2. --- Principles and Theories --- p.10 / Chapter 2.1 --- Principle of Wavelength Switching in Self-Seeded Laser --- p.11 / Chapter 2.2 --- Principle of Synchronous Injection Seeding of two Lasers --- p.15 / Chapter 2.3 --- Principle of Fast Spectral Improvement in DFB Laser with Optical Feedback --- p.17 / Chapter 2.4 --- Principle of Spectrally Resolved Analysis --- p.19 / Reference --- p.24 / Chapter 3. --- Switching Dynamics between Single-Mode and Dual-Mode Pulse Emissions from a Self-Seeded Laser Diode --- p.25 / Chapter 3.1 --- Introduction --- p.26 / Chapter 3.2 --- Experimental Details and Discussion --- p.28 / Chapter 3.3 --- Summary --- p.37 / Reference --- p.38 / Chapter 4. --- Spectrally Resolved Analysis of Fast Tuning in Single-Mode Pulses Generated from Mutually Injection-Seeded Fabry- Perot Laser Diodes --- p.40 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Experimental Details and Discussion --- p.42 / Chapter 4.3 --- Summary --- p.51 / Reference --- p.52 / Chapter 5. --- Fast Spectral Improvement in Gain-Switched Pulses Generated from a Distributed Feedback Laser with Weak Optical Feedback --- p.54 / Chapter 5.1 --- Introduction --- p.55 / Chapter 5.2 --- Experimental Details and Discussion --- p.57 / Chapter 5.3 --- Summary --- p.65 / Reference --- p.66 / Chapter 6. --- Conclusion and Future Work --- p.67 / Chapter 6.1 --- Conclusion --- p.67 / Chapter 6.2 --- Future Works --- p.69 / Reference --- p.71 / Appendices --- p.A-l / Appendix A. List of Publications --- p.A-l / Appendix B. Modeling of Self-Seeded Fabry-Perot Laser --- p.A-2 / Appendix C. List of Figures --- p.A-4