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This dissertation is an experimental study of a novel type of interferometry based on the generation of Second Harmonic (SH) light. In this work interferometers are described in which an interference pattern arises when two SH waves are superimposed. These waves come from doubling the fundamental frequency of a laser by means of non-linear crystals. Three interferometers are described that have different applications according to their sensitivity to detect wavefront distortions. One interferometer has low sensitivity and is useful in the contouring of refractive objects that produce large wavefront distortions of the order of hundreds of visible wavelengths. The other two interferometers have high sensitivity and one of them is capable of detecting wavefront distortions as small as 1/20 of wavelength. Special emphasis is placed on development of the first interferometer which is a real-time, common-path, self-referencing interferometer that yields interferograms in the visible. The interferometer is based on the fact that a SH wavefront generated under PM conditions is a faithful replica of the laser wavefront. The two interfering SH wavefronts are produced one before and the other after the object under study, and by virtue of its chromatism, they are very slightly different. Consequently, very low density fringes are produced upon their superposition. In this application, noncritically phase matched crystals perform best, and we have found that Y-cut LiNbO₃ crystals configured for surface acousto-optic applications are very convenient. The conversion efficiencies are very low (of the order of 10⁻⁵) consequently optical damage to the LiNbO₃ due to the SH is no problem. The crystals are phase matched by controlling their temperature and are used with a repetitively pulsed Nd:Yag laser operating at 1.06 μm. The chief limitations of this interferometer come from practical considerations in imaging objects with high spatial frequencies that reduce the contrast of the interferograms. The high sensitivity interferometers make use of the changes of phase and amplitude induced in the SH wavefront by the phase mismatch of angle tuned crystals to provide information. The interferometers are directly sensitive to small wavefront tilts and do not require additional reference wavefronts.

Nonlinear phenomena originating from the distributed coupling process were observed when distributed couplers, such as prisms and gratings, were used to couple light into nonlinear ZnS thin film waveguides. The efficiency of the nonlinear distributed coupling process was found to depend on two independent parameters, the angle of the incident beam and the power of the incident beam. Depending on the detuning of the incident angle, from the optimum incident angle at low powers, either optical limiting, power-dependent switching, or power-dependent bistability of the coupling efficiency, and thereby of the in-coupled power, was observed. At zero detuning, a twenty-fold decrease of the coupling efficiency with increasing powers was measured. At a nonzero detuning of the incident angle, power-dependent switching at milliwatt powers was observed. At larger angular detunings, corresponding to the angular width. FWHM, of the coupling peak at low powers, power-dependent bistability was observed, and the width of the bistability loop was found to increase with increasing detunings. All-optical beam scanning via a nonlinear grating coupler was also demonstrated, utilizing a control-signal beam configuration, where the signal beam scanned through an angle of 0.5° when the power of the control beam was varied. The observed nonlinearity in ZnS was positive and of thermal origin. The power-induced change in the refractive index was found to be 0.01 and a relaxation time of 10 μsec was measured. Problems with the long-term stability of the nonlinear distributed coupling process were traced to the occurrence of desorption and adsorption of water vapor in the ZnS films.

The culmination of a comprehensive experimental study of a number of nonlinear optical materials and their device applications. The optical phenomenology surrounding the interaction of laser radiation with these materials is emphasized. In addition to using interferometric techniques for their investigation and application, the overall theme of the research is the incorporation of interferometric descriptions of these interactions. Interference is commonly regarded to be the domain of linear optics; this work invalidates that notion. Nonlinear optics (NLO) is presented as simply a natural extension of linear optics. After a complete introduction to the general theory and relevant concepts required in the field of NLO, the first half of this manuscript presents a number of studies concerned with second-order nonlinear crystals for laser frequency conversion. The second half of this dissertation presents research on the nonlinear optical properties of semiconductors and semiconductor microstructures for optical-bistability-related applications. Optical bistability and related phenomena made possible using these materials in a nonlinear Fabry-Perot interferometer are stressed.

A dissertation submitted to the Faculty Of Science in partial fulfilment of the requirements for the degree of Master of Science by research only in the School of Physics, University of the Witwatersrand, Johannesburg. July 11, 2017. / A discrete Q-switched laser that gives a side-lobed single pulse as a laser output was implemented; followed by studying energy extraction e ciencies and pulse characterisation. The aim was to help design a passively Q-switched laser that gives a smooth single pulse of optimum energy as a laser output. The smoothness feature in a single pulse is important in some applications such as range nding. The concepts are demonstrated both experimentally and numerically; the latter using Fox-Li approach to modeling resonator modes with the Fresnel's integral for the system under study. In the rst two chapters, fundamentals of how a laser works and the spatial mode development are studied. In chapter 1, the principles of a laser are discussed: absorption, spontaneous and stimulated emission. Also, di erent types of pumping sources and resonator con gurations that can be used are discussed. In chapter 2, the focus is on developing spatial modes of a laser. The fundamental and high order modes are discussed together with their propagation laws. Then a numerical method is used to nd the eigenmodes of an arbitrary resonator con guration. This numerical method is used to simulate propagation of a fundamental mode and the simulation results are compared to analytical propagation laws. Then, this numerical method is used to simulate a laser resonator. The eigenmode of the lowest loss in the resonator was found. In chapters 3 and 4, experimental work is done on a Q-switched laser where the focus is on the overall laser performance. In chapter 3, Q-switched laser output energies are studied for di erent combinations of Q-switch transmission values and output coupler re ectivities. In addition, the in uence of spatial modes on a Q-switched pulse shape and pulse width are studied, taking into account beam divergence. In chapter 4, conclusions and future work are presented. In future work, the knowledge of spatial mode in uence on pulse shape, pulse width and beam divergence from chapter 3 is exploited. Then particular resonator con guration that gives optimised output results (Q-switched laser output energy, beam divergence, pulse shape and pulse width) is chosen. On that particular resonator, di erent Q-switch transmission values are studied, but now looking only at beam divergence and pulse width. Also, some suggestions on further improving laser performance are given. / LG2018

Chan Siu Wai = 利用二次諧波比較應用在非線性光學聚合材料上不同的極化技術 / 陳兆偉. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 105-106). / Text in English; abstracts in English and Chinese. / Chan Siu Wai = Li yong er ci xie bo bi jiao ying yong zai fei xian xing guang xue ju he cai liao shang bu tong de ji hua ji shu / Chen Zhaowei. / Anknowledgements --- p.ii / Abstract --- p.iii / Chinese Abstract --- p.iv / List of figures --- p.v / Contents --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Formulation of nonlinear optics --- p.2 / Chapter 1.2 --- Relationship between microscopic and macroscopic nonlinear susceptibility for a poled polymer --- p.4 / Chapter 1.3 --- Generation of electromagnetic radiation by nonlinear polarization --- p.7 / Figure --- p.9 / Chapter Chapter 2 --- Poling of NLO polymer --- p.10 / Chapter 2.1 --- Doped NLO polymeric system --- p.10 / Chapter 2.2 --- Poling techniques --- p.13 / Chapter 2.2.1 --- Thermal´ؤassisted poling (TAP) --- p.14 / Chapter 2.2.2 --- Photoassisted poling (PAP) --- p.16 / Chapter 2.2.3 --- All-optical poling (AOP) --- p.20 / Chapter 2.3 --- Relaxation studies of poled NLO polymers --- p.22 / Figures --- p.26 / Chapter Chapter 3 --- Experimental methods --- p.32 / Chapter 3.1 --- Laser system --- p.32 / Chapter 3.2 --- Detection system --- p.33 / Chapter 3.3 --- Reference arm --- p.33 / Chapter 3.4 --- Experimental setup --- p.34 / Chapter 3.5 --- Samples preparation --- p.35 / Figures --- p.37 / Chapter Chapter 4 --- Growth and decay of optical nonlinearity In poled polymer --- p.42 / Chapter 4.1 --- Reliability and validity of the data acquisition procedures --- p.42 / Chapter 4.1.1 --- Temperature calibration and the voltage supply --- p.42 / Chapter 4.1.2 --- Possibilities of damage or degradation of the samples during the experiment --- p.43 / Chapter 4.1.3 --- Effect of probing beam intensity and the duration on the growth and decay of x(2) in A〇P --- p.44 / Chapter 4.2 --- Basic features of the different poling techniques --- p.45 / Chapter 4.2.1 --- Below Tg electric poling (EP) in the glassy state --- p.45 / Chapter 4.2.2 --- Thermal assisted poling (TAP) --- p.47 / Chapter 4.2.3 --- Photoassisted poling (PAP) in the glassy state --- p.49 / Chapter 4.2.3.1 --- Effects of polarization of the pumping light on photoinduced poling --- p.50 / Chapter 4.2.3.2 --- Comparison of photoassisted poling at 50°C and 75°C --- p.51 / Chapter 4.2.3.3 --- Can photoassisted poling work on DANS/PMMA sample? --- p.52 / Chapter 4.2.4 --- All-optical poling (AOP) in the glassy state --- p.53 / Chapter 4.3 --- Comparison of the relaxation of X(2) poled by the four poling techniques --- p.54 / Chapter 4.3.1 --- Methods in defining the relaxation curves --- p.54 / Chapter 4.3.2 --- "X(2) relaxation of DR-1/PMMA sample poled by EP, TAP, PAP and AOP" --- p.55 / Chapter 4.3.3 --- Comparison of the fitting of the relaxation data by different models --- p.57 / Figures --- p.59 / Chapter Chapter 5 --- Physical aging and its effect on the Poling stability --- p.73 / Chapter 5.1 --- Aging effect of samples poled by EP --- p.73 / Chapter 5.2 --- Aging effect of samples poled by TAP --- p.74 / Chapter 5.3 --- Aging effect of samples poled by PAP --- p.75 / Figures --- p.78 / Chapter Chapter 6 --- Results and discussions on other Observations --- p.86 / Chapter 6.1 --- Poling with TAP and PAP successively --- p.86 / Chapter 6.2 --- Secondary poling of EP/TAP processed NLO polymer --- p.88 / Chapter 6.3 --- Effect of a pumping green light on NLO polymer (DR-1/PMMA) in the glassy state --- p.90 / Chapter 6.4 --- Depoling effect by a pumping green light --- p.91 / Figures --- p.93 / Chapter Chapter 7 --- Conclusions --- p.102 / References --- p.105

by Chan Sung-Chun = 具有二階非線性光學性質的主體-客體多聚物系統中的載色體的動力學研究 / 陳崇真. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 107-109). / Text in English; abstracts in English and Chinese. / by Chan Sung-chun = Ju you er jie fei xian xing guang xue xing zhi de zhu ti--ke ti duo ju wu xi tong zhong de zai se ti de dong li xue yan jiu / Chen Chongzhen / Acknowledgements --- p.ii / Abstract --- p.iii / Chinese Abstract --- p.iv / Table of Contents --- p.v / List of Figures --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Interaction of light with a medium --- p.2 / Chapter 1.2 --- Tensor properties and Inversion symmetry --- p.3 / Chapter 1.3 --- Relationship between microscopic and macroscopic nonlinear susceptibility for a poled polymer --- p.5 / Chapter 1.4 --- Second Harmonic Generation by nonlinear polarization --- p.9 / Chapter 1.5 --- Outline of this thesis --- p.11 / Figures --- p.13 / Chapter Chapter 2 --- Poling and relaxation of Nonlinear Optical Polymeric systems --- p.14 / Chapter 2.1 --- Guest-Host nonlinear optical polymeric systems --- p.14 / Chapter 2.2 --- Poling of NLOP systems --- p.16 / Chapter 2.2.1 --- Thermal-assisted Electric Poling --- p.17 / Chapter 2.2.2 --- Photo-assisted Electric Poling --- p.19 / Chapter 2.2.3 --- All-Optical Poling --- p.22 / Chapter 2.3 --- Relaxation study of NLOP systems --- p.24 / Figures --- p.29 / Chapter Chapter 3 --- Experimental Method --- p.32 / Chapter 3.1 --- Sample Preparation --- p.32 / Chapter 3.2 --- Poling and Thermal history of samples --- p.35 / Chapter 3.3 --- Experimental Setup --- p.37 / Chapter 3.3.1 --- Laser system --- p.37 / Chapter 3.3.2 --- Data acquisition system --- p.37 / Chapter 3.3.3 --- Reference arm --- p.38 / Chapter 3.3.4 --- Optical Path --- p.39 / Figures --- p.43 / Chapter Chapter 4 --- Poling and relaxation studies of second order optical nonlinearity in a guest-host system --- p.50 / Chapter 4.1 --- Reliability and Reproducibility of the experimental result --- p.50 / Chapter 4.1.1 --- Temperature control --- p.50 / Chapter 4.1.2 --- Poling voltage --- p.51 / Chapter 4.1.3 --- Degradation of the sample --- p.52 / Chapter 4.1.4 --- Possible light induced decay by the probing laser beam --- p.53 / Chapter 4.2 --- Poling and relaxation in the Guest-Host system of DR-1/PMMA --- p.54 / Chapter 4.2.1 --- Poling in DR-l/PMMA --- p.54 / Chapter 4.2.2 --- Relaxation of polar orderin DR-l/PMMA --- p.58 / Chapter 4.3 --- Comparison of different relaxation models --- p.60 / Figures --- p.61 / Chapter Chapter 5 --- Investigation of chromophores dynamicsin poled nonlinear optical polymers by secondary poling --- p.69 / Chapter 5.1 --- Methods for studying the mobility of chromophores at sub-Tg temperature --- p.69 / Chapter 5.2 --- Experimental details --- p.71 / Chapter 5.3 --- Experimental results and discussion --- p.72 / Chapter 5.3.1 --- Free relaxation of chromophores --- p.72 / Chapter 5.3.2 --- Forced decay and further poling of chromophores --- p.73 / Chapter 5.4 --- Model for describing the temporal behavior of secondary poling --- p.76 / Chapter 5.4.1 --- Derivation of the model --- p.76 / Chapter 5.4.2 --- Quantitative description of the experimental results --- p.79 / Figures --- p.83 / Chapter Chapter 6 --- Results and observations on Photo-assisted electric poling --- p.89 / Chapter 6.1 --- Re-poling of the sample after PAP --- p.89 / Chapter 6.2 --- Other observations on Photo-assisted electric poling --- p.92 / Figures --- p.96 / Chapter Chapter 7 --- Conclusions --- p.103 / References --- p.107

No description available.

Thesis (Ph. D.)--Washington State University, December 2007. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 186-200).