Nonlinear optical properties of passive and active semiconductors are investigated experimentally and theoretically. Improvement of switching cycle time in optical nonlinear etalons to 40 ps is demonstrated, and strained-layer InGaAs/GaAs quantum well material is used in an asymmetric etalon to greatly improve switching power and contrast. Coherent energy transfer (CET) induced by injection of an external light field is demonstrated in a GaAs quantum well vertical-cavity surface-emitting laser (VCSEL). The evolution of CET induced asymmetric gain with increasing injected power is investigated experimentally and theoretically, and it is found that the CET induced effective gain peak and dip are detuned proportionally with injected power as in homogeneously broadened media and in contrast to other multi-wave effects in GaAs which are detuned proportionally with the light field. Transfer of gain modification between orthogonally polarized modes of the VCSEL and cascading of gain modification within a mode is observed and investigated. The approach of a laser to an injection locked state through increased injected power is investigated experimentally and theoretically, showing new emission frequencies produced which evolve to chaos-like behavior before reaching the phase locked state. CET induced gain modification is used to demonstrate low-power high-contrast switching between polarization modes of the VCSEL with differential gain of 3,510. Switching speed and switching bistability is observed and investigated. Injection induced modification of VCSEL transverse modes is studied experimentally and theoretically. Field defects in the resulting field are observed, and their locations are dependent on the frequency of the injected field, in contrast to the temporally evolving defects normally observed. The rich behavior of nonlinear properties, especially in gain media provide interesting results and valuable applications.

No description available.

Computer modeling of prism coupling of pulsed laser irradiation at a wavelength of 1064 nm into an organic polymer waveguide with Kerr Law nonlinearities showed that the prism coupling technique was inherent problems that make it difficult to accurately determine the magnitude of the refractive index change. Uncertainty in knowledge of the gap spacing under the prism leads to errors in any estimates of these nonlinear refractive index changes. Results from prism coupling experiments conducted on a polymer waveguide with a pulsed laser are inconclusive.

<p>The nonlinear interaction between light and atoms is an extensive field of study with a broad range of applications in quantum information science and condensed matter physics. Nonlinear optical phenomena occurring in cold atoms are particularly interesting because such slowly moving atoms can spatially organize into density gratings, which allows for studies involving optical interactions with structured materials. In this thesis, I describe a novel nonlinear optical effect that arises when cold atoms spatially bunch in an optical lattice. I show that employing this spatial atomic bunching provides access to a unique physical regime with reduced thresholds for nonlinear optical processes and enhanced material properties. Using this method, I observe the nonlinear optical phenomenon of transverse optical pattern formation at record-low powers. These transverse optical patterns are generated by a wave- mixing process that is mediated by the cold atomic vapor. The optical patterns are highly multimode and induce rich non-equilibrium atomic dynamics. In particular, I find that there exists a synergistic interplay between the generated optical pat- terns and the atoms, wherein the scattered fields help the atoms to self-organize into new, multimode structures that are not externally imposed on the atomic sample. These self-organized structures in turn enhance the power in the optical patterns. I provide the first detailed investigation of the motional dynamics of atoms that have self-organized in a multimode geometry. I also show that the transverse optical patterns induce Sisyphus cooling in all three spatial dimensions, which is the first observation of spontaneous three-dimensional cooling. My experiment represents a unique means by which to study nonlinear optics and non-equilibrium dynamics at ultra-low required powers.</p> / Dissertation

Lasers are an essential technology enabling countless fields of optics, however, their operation wavelengths are limited to isolated regions across the optical spectrum due to the need for suitable gain media. Parametric frequency conversion (PFC) is an attractive means to convert existing lasers to new colors using nonlinear optical interactions rather than the material properties of the host medium, allowing for the development of high power laser sources across the entire optical spectrum. PFC in bulk χ(2) crystals has led to the development of the optical parametric oscillator, which is currently the standard source for high power light at non-traditional wavelengths in the laboratory setting. Ideally, however, one could implement PFC in an optical fiber, thus leveraging the crucial benefits of a guided-wave geometry: alignment-free, compact, and robust operation. Four-wave mixing (FWM) is a nonlinear effect in optical fibers that can be used to convert frequencies, the major challenge being conservation of momentum, or phase matching, between the interacting light waves. Phase matching can be satisfied through the interaction of different spatial modes in a multi-mode fiber, however, previous demonstrations have been limited by mode stability and narrow-band FWM gain. Alternatively, phase matching within the fundamental mode can be realized in high-confinement waveguides (such as photonic crystal fibers), but achieving the anomalous waveguide dispersion necessary for phase matching at pump wavelengths near ∼1 μm (where the highest power fiber lasers emit) comes at the cost of reducing the effective area of the mode, thus limiting power-handling. Here, we specifically consider the class of Bessel-like LP0,m modes in step-index fibers. It has been shown that these modes can be selectively excited and guided stably for long lengths of fiber, and mode stability increases with mode order ‘m’. The effective area of modes in these fibers can be very large (>6000 μm2 demonstrated) and is decoupled from dispersion, allowing for phase matching within a single mode in a power-scalable platform. Furthermore, step-index fibers can guide many different LP0,m modes, allowing access to a highly multi-moded basis set with which to study FWM interactions between different modes. In this thesis we develop techniques to excite, propagate, and characterize LP0,m modes in order to demonstrate FWM in two regimes: monomode interactions comprising waves all belonging to the same mode, and intermodal interactions between different modes. In the monomode regime we demonstrate parametric sources which operate at near-infrared wavelengths under-served by conventional fiber lasers, including 880, 974, 1173, and 1347 nm. The output pulses for these systems are ∼300 ps in duration and reach peak powers of ∼10 kW, representing, to the best our knowledge, the highest peak power fiber laser sources demonstrated at these wavelengths to date. In the intermodal regime, we demonstrate a cascade of FWM processes between different modes that lead to a series of discrete peaks in the visible portion of the spectrum, increasing monotonically in mode order from LP0,7 at 678 nm to LP0,16 at 443 nm. This cascade underscores the huge number of potential FWM interactions between different LP0,m modes available in a highly multi-mode fiber, which scale as N4 for N guided modes. Finally, we demonstrate a novel intermodal FWM process pumped between the LP0,4 and LP0,5 modes of a step-index fiber, which provides broadband FWM gain (63 nm at 1550 nm) while maintaining wavelength separations of nearly an octave (762 nm) – a result that cannot be replicated in the single-mode regime. We seed this process to generate a ∼10 kW, ∼300-ps pulsed fiber laser wavelength-tunable from 786-795 nm; representing a fiber analogue of the ubiquitous Ti:Sapphire laser.

This thesis presents several advances in the technology and applications of photonic crystal fibres achieved over the last three years. Chapters 1 and 2 give the background material important to understand the results presented in chapters 3, 4 and 5. In chapter 1, linear properties of optical fibres are described. This chapter focuses particularly on how the engineering of the cladding structure of solid core photonic crystal fibres can be used to vary the fibre properties, most importantly the group index and dispersion. Propagation in all-solid photonic bandgap fibres is also discussed in terms of the anti-resonant reflecting optical waveguide model. Chapter 2 introduces the nonlinear optical effects that are important to understand the work presented in chapters 4 and 5. In chapter 3, a method to reduce bend losses in all-solid photonic bandgap fibres is outlined. The reduction of these losses is achieved by redesigning the high-index inclusions in the cladding structure to suppress cladding modes that strongly couple to the fundamental core-guided mode when the fibre is bent. In chapter 4, a method of tapering photonic crystal fibres in order to decrease the dispersion along their length is described. The tapers are used to compress solitons via adiabatic soliton compression and a combination of adiabatic soliton compression and soliton effect compression, achieving a factor of 15 compression of a transform-limited pulse to below 50 fs. Chapter 5 describes how engineering the cladding structure of photonic crystal fibres can be used to generate shorter frequencies in supercontinuum generation. The method by which this achieved is experimentally verified and then exploited to generate a continuum incorporating the entire visible spectrum using low cost, low maintenance pump sources.

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