Lei, Kin Pang. / 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.

Hui Yuen Yung. / Thesis submitted in: August 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 70-73). / Text in English; abstract also in Chinese. / Hui Yuen Yung. / Acknowledgements --- p.vi / Abstract --- p.vii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Second harmonic generation --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- Maxwell's equations in dielectric media --- p.6 / Chapter 2.3 --- Second harmonic generation --- p.7 / Chapter 2.4 --- Phase matching --- p.8 / Chapter 2.5 --- Quasi phase matching --- p.10 / Chapter 2.6 --- Inversion symmetry --- p.11 / Chapter 3 --- Third order nonlinear optical processes in optical fibers --- p.14 / Chapter 3.1 --- Introduction --- p.14 / Chapter 3.2 --- Optical fibers --- p.15 / Chapter 3.3 --- Third order interaction between waves of same frequency --- p.16 / Chapter 3.4 --- Third order interaction between waves of different frequencies --- p.19 / Chapter 4 --- Multiphoton ionization interference effect --- p.23 / Chapter 4.1 --- Historical development --- p.23 / Chapter 4.2 --- Multiphoton ionization interference effect --- p.26 / Chapter 4.3 --- Periodic ionization --- p.27 / Chapter 4.4 --- Periodic electric field --- p.28 / Chapter 4.5 --- Physical interpretation --- p.29 / Chapter 5 --- Experimental setup --- p.32 / Chapter 5.1 --- Introduction --- p.32 / Chapter 5.2 --- Laser system --- p.32 / Chapter 5.3 --- Optical fibers --- p.33 / Chapter 5.4 --- Coupling light into fibers --- p.34 / Chapter 5.5 --- Detection system --- p.36 / Chapter 5.6 --- Optical layout --- p.36 / Chapter 6 --- Second harmonic generation in optical fibers --- p.40 / Chapter 6.1 --- Introduction --- p.40 / Chapter 6.2 --- Self-preparation in optical fibers --- p.41 / Chapter 6.3 --- Polarization dependence --- p.42 / Chapter 6.4 --- Seeding optical fibers --- p.42 / Chapter 6.5 --- Seeding by varying green light intensity --- p.45 / Chapter 6.6 --- Square dependence of second harmonic generation in optical fibers --- p.46 / Chapter 7 --- Erasure of x(2) grating in optical fibers --- p.56 / Chapter 7.1 --- Introduction --- p.56 / Chapter 7.2 --- Experiment --- p.58 / Chapter 7.3 --- Results --- p.59 / Chapter 7.3.1 --- Erasure by different propagating mode --- p.59 / Chapter 7.3.2 --- Erasure in germanium-doped fiber --- p.60 / Chapter 7.3.3 --- Erasure in erbium-doped fiber --- p.61 / Chapter 7.4 --- Discussion --- p.61 / Chapter 8 --- Conclusion --- p.68 / Chapter 8.1 --- Summary of our work --- p.68 / Chapter 8.2 --- Outlook --- p.69 / Chapter 8.2.1 --- Multiphoton ionization in polymer --- p.69 / Chapter 8.2.2 --- Erasure by blue light --- p.69 / Bibliography --- p.70

Song Liang = 向列液晶中激光束感应的取向重联非线性光学效应和取向性光折变光栅形成 / 宋亮. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Song Liang = Xiang lie ye jing zhong ji guang shu gan ying de qu xiang zhong lian fei xian xing guang xue xiao ying he qu xiang xing guang zhe bian guang zha xing cheng / Song Liang. / Abstract --- p.i / 论文摘要 --- p.iii / Acknowledgement --- p.iv / Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / References --- p.5 / Chapter Chapter 2 --- Brief review of liquid crystals and nonlinear optics of liquid crystals --- p.9 / Chapter 2.1 --- Brief review of liquid crystals --- p.9 / Chapter 2.1.1 --- General description --- p.9 / Chapter 2.1.2 --- Types of liquid crystals --- p.11 / Chapter 2.1.3 --- Order parameter --- p.14 / Chapter 2.1.4 --- Liquid crystal alignment --- p.14 / Chapter 2.1.5 --- Continuum theory of liquid crystals --- p.16 / Chapter 2.2 --- Nonlinear optics of liquid crystals --- p.20 / Chapter 2.2.1 --- Basic mechanism of nonlinear optics --- p.20 / Chapter 2.2.2 --- Self-phase modulation --- p.23 / Chapter 2.2.3 --- Orientational photorefractive effects --- p.29 / Chapter 2.3 --- Sample preparation --- p.34 / Chapter 2.4 --- Conclusion --- p.37 / References --- p.39 / Chapter Chapter 3 --- Domain formation in homeotropic nematic liquid crystal cell --- p.42 / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Domain formation under applied dc and ac electric fields --- p.44 / Chapter 3.3 --- Light scattering of domains under applied dc and ac electric fields --- p.49 / Chapter 3.4 --- Conclusion --- p.53 / References --- p.54 / Chapter Chapter 4 --- Laser induced self-phase modulation and effects of applied electric field --- p.56 / Chapter 4.1 --- Introduction --- p.56 / Chapter 4.2 --- Self-phase modulation without applied electric field --- p.58 / Chapter 4.2.1 --- Experimental setup --- p.58 / Chapter 4.2.2 --- Experimental results and discussions --- p.59 / Chapter 4.3 --- Effects of applied electric field --- p.67 / Chapter 4.3.1 --- Effects of applied dc electric field --- p.67 / Chapter 4.3.2 --- Effects of applied ac electric field --- p.72 / Chapter 4.4 --- Conclusion --- p.75 / References --- p.77 / Chapter Chapter 5 --- Orientational photorefractive grating in nematic liquid crystals --- p.80 / Chapter 5.1 --- Introduction --- p.80 / Chapter 5.2 --- Orientational photorefractive grating under dc electric field --- p.82 / Chapter 5.2.1 --- Experimental setup --- p.82 / Chapter 5.2.2 --- Experimental results and discussion --- p.84 / Chapter 5.3 --- Orientational photorefractive grating under ac electric field --- p.90 / Chapter 5.3.1 --- Raman-Nath grating --- p.90 / Chapter 5.3.2 --- Quasi-Bragg grating --- p.96 / Chapter 5.4 --- Conclusion --- p.98 / References --- p.100 / Chapter Chapter 6 --- Summary and future outlook --- p.103 / List of Publications and Conference Presentations --- p.107

Lee Sim Heung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEGEMENT --- p.vi / LIST OF FIGURES --- p.xi / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- New challenges in telecommunication --- p.2 / Chapter 1.2. --- Introduction to optical non-linearity and its impact to optical network --- p.3 / Chapter 1.3. --- Applications of optical nonlinearity --- p.5 / Chapter 1.3.1. --- Extinction ratio enhancement and wavelength conversion --- p.5 / Chapter 1.3.2. --- All optical ASK to DPSK converter --- p.6 / Chapter 1.3.3. --- All-optical RZ to NRZ format converter --- p.8 / Chapter 1.3.4. --- RF clock component enhancement for NRZ data --- p.10 / Chapter 1.3.5. --- Multi-wavelength converter with multi-channel broadcasting --- p.11 / Chapter 1.4. --- Overview --- p.12 / Chapter 2. --- PRINCIPLES AND THEORIES --- p.18 / Chapter 2.1. --- Optical nonlinearity --- p.19 / Chapter 2.2. --- Self-phase modulation (SPM) --- p.21 / Chapter 2.3. --- Cross-phase modulation (XPM) --- p.25 / Reference: --- p.28 / Chapter 3. --- EXTINCTION RATIO ENHANCEMENT AND WAVELENGTH CONVERSION USING CROSS-PHASE MODULATION IN A DISPERSION-SHIFTED FIBER --- p.29 / Chapter 3.1. --- Introduction --- p.30 / Chapter 3.2. --- Experimental details of extinction ratio enhancement --- p.31 / Chapter 3.3. --- Result and Discussions --- p.32 / Chapter 3.4. --- Conclusion --- p.36 / References: --- p.37 / Chapter 4. --- ALL-OPTICAL ASK TO DPSK FORMAT CONVERSION --- p.38 / Chapter 4.1. --- All Optical ASK to DPSK Format Conversion Using Cross-Phase Modulation in a Non-linear Fiber --- p.39 / Chapter 4.1.1. --- Introduction --- p.40 / Chapter 4.1.2. --- Experimental Details of ASK to DPSK format conversion by XPM in DSF --- p.42 / Chapter 4.1.3. --- Results and Discussion --- p.44 / Chapter 4.1.4. --- Experimental Details of ASK to DPSK format conversion by XPM in PCF --- p.47 / Chapter 4.1.5. --- Result and Discussion of XPM in PCF --- p.49 / Chapter 4.1.6. --- Comparison of DSF and PCF --- p.51 / References: --- p.54 / Chapter 4.2. --- All Optical ASK to ASK/DPSK Orthogonal Code Format Conversion Using Cross-Phase Modulation in a Dispersion-Shifted Fiber --- p.56 / Chapter 4.2.1. --- Introduction --- p.57 / Chapter 4.2.2. --- Experimental Details of ASK to ASK/DPSK format conversion --- p.58 / Chapter 4.2.3. --- Results and Discussion --- p.60 / Chapter 4.2.4. --- Conclusion --- p.63 / References: --- p.64 / Chapter 5. --- ALL-OPTICAL RZ TO NRZ FORMAT CONVERSION --- p.65 / Chapter 5.1. --- Introduction --- p.65 / Chapter 5.2. --- All-Optical RZ to NRZ Data Format Conversion Using Spectral Broadening Effect in a Dispersion-Shifted Fiber --- p.67 / Chapter 5.2.1. --- Principle of RZ-to-NRZ format conversion using SPM --- p.68 / Chapter 5.2.2. --- Experiment Details --- p.71 / Chapter 5.2.3. --- Results and Discussion --- p.72 / Chapter 5.2.4. --- Conclusion --- p.77 / Chapter 5.3. --- Spectral Filtering from a Cross-Phase Modulated Signal for RZ to NRZ Format and Wavelength Conversion --- p.78 / Chapter 5.3.1. --- Principle of RZ to NRZ format conversion by XPM --- p.79 / Chapter 5.3.2. --- Experiment --- p.81 / Chapter 5.3.3. --- Results and Discussion --- p.83 / Chapter 5.3.4. --- Conclusions --- p.87 / References: --- p.88 / Chapter 6. --- ALL-OPTICAL CLOCK COMPONENT EXTRACTION FROM NRZ DATA SIGNALS USING SELF-PHASE MODULATION IN A DISPERSION-SHIFTED FIBER --- p.90 / Chapter 6.1. --- Introduction --- p.91 / Chapter 6.2. --- Experimental Details --- p.92 / Chapter 6.3. --- Results and Discussion --- p.93 / Chapter 6.4. --- Conclusion --- p.96 / References: --- p.97 / Chapter 7. --- ALL-OPTICAL WAVELENGTH MULTICASTING USING SELF- PHASE MODULATION IN A NONLINEAR PHOTONIC CRYSTAL FIBER --- p.98 / Chapter 7.1. --- Introduction --- p.99 / Chapter 7.2. --- Simulation results --- p.100 / Chapter 7.3. --- Experimental Details --- p.103 / Chapter 7.4. --- Result and Discussion --- p.104 / Chapter 7.5. --- Conclusions --- p.109 / References: --- p.110 / Chapter 8. --- CONCLUSION AND FUTURE WORK --- p.111 / Chapter 8.1. --- Conclusion --- p.111 / Chapter 8.2. --- Possible Future Work --- p.114 / References: --- p.116 / APPENDIX --- p.117 / List of Publications --- p.117

This thesis investigates two thematic lines of research, both underpinned by non-Markovian system-reservoir interactions in quantum optics. The overarching focus is on modelling the open system dynamics in a non-perturbative fashion, broadly on - though not restricted to - instances when the environment is structured. A theory is developed by means of enlarging the open system over environmental degrees of freedom to include memory effects in its dynamics. This is achieved using an established technique that involves mapping a bosonic environment onto a 1D chain of harmonic oscillators. Within this setting, we apply a Heisenberg equation-of-motion approach to derive an exact set coupled differential equations for the open system and a single auxiliary oscillator of the chain. The combined equations are shown to have their interpretation rooted in a quantum Markov stochastic process. Including the auxiliary chain oscillator as part of the original system then enables us to obtain an exact master equation for the enlarged system, avoiding any need for the Born-Markov approximations. Our method is valid for a dissipative two-state system, with cases of multiple excitations and added driving discussed. Separately, we apply the framework of quantum Darwinism to an atom-cavity system, and, subsequently, to a more general multiple-environment model. In both cases, the time-dependent spread of correlations between the open system and fractions of the environment is analysed during the course of the decoherence process. The degree to which information is redundant across different fractions is checked to infer the emergence of classicality. In the second case, we go further and present a decomposition of information in terms of its quantum and classical correlations. A quantitative measure of redundancy is also studied with regard to its ability to witness non-Markovian behaviour. Besides fundamental interest, our results have application to quantum information processing and quantum technologies, keeping in mind the potential beneficial use of non-Markovian effects in reservoir engineering.

The objective of this thesis is to develop the quantum theory of the motional degrees of freedom of a charged particle in a Penning trap. The theory is treated within the formalism of quantum optics, and explores the use of dressed-atom methods by exploiting the threefold SU(N) algebraic structure of the problem. The quantum form of the experimental techniques of sideband coupling and driving to the ultra-elliptical regime are examined in this context, and resulting future applications considered. Interpretation of the quantum dynamics of the separate x and y motions of an electron is discussed, motivated by the desire to modify the trapping potential without changing the basic experimental configuration. A detailed discussion of operator methods which exploit the algebraic structure of the problem is given. This results in a clearer understanding of the physical manifestations of a range of unitary transformations upon a general three-dimensional system, and a novel interpretation of the mapping between canonical angular momentum components of isotropic and anisotropic trapping systems. The results highly promote future use of these methods in Penning trap theory, detailing a robust formulation of unitary operations which can be used to prepare the quantum state of a charged particle. The majority of the results can be applied to any Penning trap, but the theory is based throughout upon the “Geonium Chip" trap at Sussex; the scalability and planar design of this trap promotes it as natural candidate in experimental quantum optics and Gaussian quantum information studies. The work in this thesis aims to provide framework for such future applications.

The development of compact and low-cost coherent sources in visible and infrared wavelength range can provide indispensible tools for a variety of scientific, technological and industrial applications. Great progress over the last years in material science, crystal growth and semiconductor material processing in combination with recent advances in some of the more traditional technologies, in particular nonlinear frequency conversion and parametric sources, have led to the realisation of a new generation of laser sources. Furthermore, the advent of a new generation of quasi-phase-matched, waveguided and semiconductor nonlinear materials together with novel semiconductor lasers have led to the development of new frequency conversion and parametric sources with previously unattainable performance capabilities. The research described in this thesis relates to the development and characterisation of novel semiconductor based laser sources tunable in the broad spectral ranges which are unattainable for conventional lasers due to a lack of suitable laser gain materials. In the first part of the thesis the subject matter is concerned with the direct emission from laser devices. In particular, a broadly tunable InGaAs/InP strained multi-quantum well external cavity diode laser, operating in the spectral range of 1494 nm – 1667 nm with a maximum CW output power in excess of 81 mW and side-mode suppression ratio higher than 50 dB is demonstrated. This represents the highest output power and side-mode suppression ratio ever to be generated in this spectral region. A record broadly tunable high-power external cavity InAs/GaAs quantum-dot diode laser with a tuning range of 202 nm (1122 nm - 1324 nm), a maximum output power of 480 mW and a side-mode suppression ratio greater than 45 dB, is also demonstrated. This represents a promising achievement for the development of a high-power fast swept tunable laser and compact nonlinear frequency generation schemes for the green-yellow-orange-red spectral range. The second part of the thesis relates to induced nonlinear processes, focusing on frequency doubling and optical parametric oscillation. In particular, an all-room-temperature CW second harmonic generation at 612.9 nm and 591.5 nm in periodically poled potassium titanyl phosphate waveguides pumped by a broadly-tunable quantum-dot external cavity diode laser with a conversion efficiency of 10.5% and 7.9%, respectively, is demonstrated. For the first time, a green-to-red tunable laser source with tunability of over 60 nm (567.7 nm – 629.1 nm) based on frequency doubling in a single periodically poled potassium titanyl phosphate waveguide pumped by a single broadly-tunable quantum dot laser is demonstrated. These results are an important step towards a compact tunable coherent visible light source, operating at room temperature. The possibility of nonlinear frequency conversion in orientation-patterned GaAs waveguides is also investigated. The technology of low-loss periodically poled GaAs waveguided crystals is developed and such crystals are fabricated. Second harmonic generation at 1621 nm in low-loss periodically poled GaAs waveguide is demonstrated. An optical parametric oscillator system used as the pump source for GaAs devices and based on the periodically poled 5 mol% MgO-doped Congruent Lithium Niobate crystal, generating light in the wavelength range between 1430 nm and 4157 nm, is presented. The obtained results show a great promise for realisation of efficient quasi-phase-matched optical parametric oscillator devices based on orientation-patterned GaAs waveguides, which enables the extending generated wavelength up to 16 µm.

In this thesis, the spectral behavior of the fundamental and sum-frequency waves, generated from the surface of a thin metal film in the Kretschmann configuration, is theoretically studied with coherent ultrashort pulses. As a first exploration of considering spectral response in nonlinear plasmonics, it is shown that the spectra of reflected sum-frequency waves exhibit pronounced shifts for the incident fundamental waves close to the plasmon coupling angle, whereas meanwhile those of reflected fundamental waves display energy holes. We also demonstrate that the scale of discovered plasmon-enhanced spectral changes is strongly influenced by the magnitude of the incidentce angle and the source pulse duration, and at a certain angle a spectral switch is observed. The appearance of large sum-frequency wave shifts can serve as an unambiguous plasmon signatur in nonlinear surface spectroscopy. Also, the discovered spectral switch can trigger extremely surface-sensitive nonlinear plasmonic sensors.

Interference has long been used for precision measurement of path-length changes. Since the advent of the laser, interference has become one of the most versatile tools in metrology. Specifically, ultra-short laser pulses allow unprecedented resolution in absolute length measurements. While ultra-short laser pulses lead to high resolution, for example in white-light interferometry, they are very susceptible to dispersion. Quantum resources have been proposed to overcome some of the problems related to distortions in the interferometric signal. For example, the Hong-Ou-Mandel (HOM) interferometer relies on frequency-entangled photon pairs and features automatic even-order dispersion cancellation and high interference visibility resilient to unbalanced loss. Quantum-OCT is a technique based on HOM interferometry, that promises to overcome Optical Coherence Tomography (OCT) a classical imaging technique based on low coherence light. Furthermore, straightforward modifications of the HOM interferometer can display several different interferometric signals, including the HOM peak, quantum beating, and phase super-resolution. However, the quantum resources required are hard to produce and dim, leading to long integration times and single-photon counting. In this thesis, we introduce the theory behind Chirped-Pulse Interferometry (CPI), a new technique that combines all the advantages of Q-OCT, including even-order dispersion cancellation, but without the need for any quantum resources. We then experimentally implement CPI and demonstrate all the important characteristics shared by the HOM interferometer, but at dramatically larger signal levels. We show how CPI can be used to measure dispersion cancelled axial profiles of an optical sample and show the improvement in resolution over white-light interferometry. Finally, we show that by modifying CPI in analogous ways to HOM, CPI can also be made to produce interferometric signal identical to the HOM peak, quantum beating, and phase super-resolution.

Interference has long been used for precision measurement of path-length changes. Since the advent of the laser, interference has become one of the most versatile tools in metrology. Specifically, ultra-short laser pulses allow unprecedented resolution in absolute length measurements. While ultra-short laser pulses lead to high resolution, for example in white-light interferometry, they are very susceptible to dispersion. Quantum resources have been proposed to overcome some of the problems related to distortions in the interferometric signal. For example, the Hong-Ou-Mandel (HOM) interferometer relies on frequency-entangled photon pairs and features automatic even-order dispersion cancellation and high interference visibility resilient to unbalanced loss. Quantum-OCT is a technique based on HOM interferometry, that promises to overcome Optical Coherence Tomography (OCT) a classical imaging technique based on low coherence light. Furthermore, straightforward modifications of the HOM interferometer can display several different interferometric signals, including the HOM peak, quantum beating, and phase super-resolution. However, the quantum resources required are hard to produce and dim, leading to long integration times and single-photon counting. In this thesis, we introduce the theory behind Chirped-Pulse Interferometry (CPI), a new technique that combines all the advantages of Q-OCT, including even-order dispersion cancellation, but without the need for any quantum resources. We then experimentally implement CPI and demonstrate all the important characteristics shared by the HOM interferometer, but at dramatically larger signal levels. We show how CPI can be used to measure dispersion cancelled axial profiles of an optical sample and show the improvement in resolution over white-light interferometry. Finally, we show that by modifying CPI in analogous ways to HOM, CPI can also be made to produce interferometric signal identical to the HOM peak, quantum beating, and phase super-resolution.