No description available.

Recent advances in experimental laser cooling have shown the possibility of stopping an atomic beam using the light pressure force of a counter-propagating laser wave. As an application to laser cooling, it is proposed to build a single frequency cesium laser that has a narrow linewidth. Laser cooling techniques are used to cool an atomic beam of cesium to an average velocity of 5 m/s, corresponding to a temperature of 0.2°K. Expressions of the basic forces that a laser wave exerts on atoms are derived according to a semi-classical approach. The experimental problems and methods of avoiding these problems are treated in detail. A computer Monte-Carlo simulation is used to discuss the feasibility of building the proposed laser. This simulation was done for an ensemble of 10,000 atoms of cesium, and it included the effects of the gravitational force and the related experimental variables. The possibility of building single frequency lasers that use a cooled medium of noble gases, and many other applications of laser cooling are briefly discussed at the end of this work.

by Chan Che Ping. / Chinese title: / Bibliography : leaf 132 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1982

Tsui Wan-lam. / Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 75-76.

Hui Sze-man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 66-69). / Text in English; abstracts in English and Chinese. / Hui Sze-man. / Abstract --- p.iii / Acknowledgement --- p.v / Table of contents --- p.vi / List of tables --- p.viii / List of Figures --- p.ix / Chapter Chapter I --- Introduction --- p.1 / Chapter Chapter II --- Thermoluminescence --- p.5 / Chapter 2.1 --- What is thermoluminescence? --- p.5 / Chapter 2.2 --- Thermoluminescence Mechanism --- p.5 / Chapter 2.3 --- Simple model by Randall and Wilkins --- p.9 / Chapter Chapter II --- I Laser induced thermoluminescence emission --- p.18 / Chapter 3.1 --- Concept of laser heating --- p.18 / Chapter 3.1.1 --- Advantages for using laser heating technique --- p.18 / Chapter 3.1.2 --- Power law heating profiles --- p.19 / Chapter 3.1.3 --- Energy transfer from laser beam to TL sample --- p.20 / Chapter 3.2 --- Zero-Dimensional for temperature profile of Thermoluminescence emission --- p.22 / Chapter Chapter IV --- Experiment and Modeling Results --- p.31 / Chapter 4.1 --- Sample Preparation --- p.31 / Chapter 4.1.1 --- Characteristics of TL material ´ؤ Lithium Fluoride (LiF) --- p.31 / Chapter 4.1.2 --- Effect of defects in LiF --- p.32 / Chapter 4.1.3 --- Sample Preparation --- p.32 / Chapter 4.2 --- TL Instrumentation and its measurements --- p.34 / Chapter 4.2.1 --- TL Instrumentation and Experimental Set-Up --- p.34 / Chapter 4.2.2 --- Measurement of sample thickness --- p.36 / Chapter 4.3 --- Laser stimulation thermoluminescence --- p.38 / Chapter 4.3.1 --- Effect of substrate on TL signal --- p.39 / Chapter 4.3.2 --- Effect of different laser's power on TL signals --- p.39 / Chapter 4.3.3 --- Effect of different irradiation duration on TL signals --- p.41 / Chapter 4.3.4 --- Effect of various sample thickness on TL signals --- p.42 / Chapter Chapter V --- Conclusion --- p.64 / Chapter 5.1 --- Conclusion --- p.64 / Chapter 5.2 --- Further Study --- p.65 / Reference --- p.66

Xu Chicheng = 光折变掺铁铌酸锂晶体中的二波耦合和光伏空间孤子 / 徐赤诚. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 113-114). / Text in English; abstracts in English and Chinese. / Xu Chicheng = guang zhe bian shan tie ni suan li jing ti zhong de er bo ou he he guang fu kong jian gu zi / Xu Chicheng. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background --- p.5 / Chapter 2.1 --- Band Transport Model --- p.5 / Chapter 2.2 --- Two-wave Mixing --- p.9 / Chapter 2.3 --- Fanning --- p.12 / Chapter 2.4 --- Photovoltaic Effect --- p.16 / Chapter 2.5 --- Spatial Solitons --- p.19 / References --- p.22 / Appendix Refractive Index perturbation in LiNb03 crystal --- p.25 / Chapter Chapter 3 --- Single Laser Beam Interactions with Fe:LiNb03 Crystals / Chapter 3.1 --- Fe:LiNb03 Crystals --- p.30 / Chapter 3.2 --- Interferometric Studies of Refractive Index Perturbations --- p.32 / Chapter 3.3 --- Fanning --- p.47 / Chapter 3.4 --- Self-defocusing --- p.53 / Chapter 3.5 --- Surface Charge Recombination --- p.58 / References --- p.67 / Chapter Chapter 4 --- Photovoltaic Spatial Soliton in Fe:LiNb03 Crystal --- p.69 / Chapter 4.1 --- Introduction --- p.69 / Chapter 4.2 --- Experimental Setup --- p.73 / Chapter 4.3 --- Results and Discussion --- p.75 / Chapter 4.4 --- Conclusion --- p.82 / References --- p.83 / Chapter Chapter 5 --- Two-wave Mixing in Fe:LiNbO3 Crystals --- p.84 / Chapter 5.1 --- Introduction --- p.84 / Chapter 5.2 --- Experimental Setup --- p.87 / Chapter 5.3 --- Results and Discussion I - Without Background Beam --- p.89 / Chapter 5.4 --- Result and Discussion II - With Background Beam --- p.96 / Chapter 5.5 --- Origin of Temporal oscillations during TWM in Fe:LiNb03 Crystal --- p.100 / Chapter 5.6 --- Conclusion --- p.108 / References --- p.109 / Chapter Chapter 6 --- Conclusion and Future Outlook --- p.111

Surface engineering provides solutions to wear and corrosion degradation of engineering components. Laser cladding is a surfacing process used to produce wear and corrosion resistant surfaces by covering a particular part of the substrate with another material that has superior properties, producing a fusion bond between the two materials with minimal dilution of the clad layer by the substrate. The advantages of laser cladding compared to conventional techniques include low and controllable heat input into the workpiece, a high cooling rate, great processing flexibility, low distortion due to the low heat input to the workpiece and minimal post-treatment. The main processing parameters of laser cladding include laser power, laser spot size, processing speed, and powder feed rate. Within an optimized operational window, all these variables have some effect on the temperature of the clad interaction zone. The laser cladding technique is very complicated because it involves metallurgical and physical phenomena, such as laser beam-materials interaction, heat transfer between the clad and the substrate, and the interdiffusion of the clad and the substrate materials. Laser cladding is currently an open-loop process, relying on the skills of the operator and requiring dedication to specialty to make it successful. Unless the required expertise is provided, attempts to make the process successful will be futile. The objective in conducting the project was to investigate and develop prototype sensors to monitor and control Nd:YAG laser cladding process. Through a LabVIEW software based monitoring program, real-time process monitoring of optical emissions in the form of light and heat radiation was carried out, and correlated with the properties of the produced clad layers. During various experiments, single- and multiple-track laser cladding trials were performed. The responses of such sensors to the selected conditions were examined and an in depth analysis of detected heat and optical radiation signals was carried out. The results of these experiments showed the ability of such sensors to recognize changes in process parameters, and detected defects on layer surfaces along with the presence of oxides. A multi-function closed-loop laser power and CNC motion table feed rate control interface based on a LabVIEW platform has been designed and built, which is capable of accepting and interpreting sensors� data and adjusting accordingly the laser power and CNC motion table feed rate to produce sound clad layers. The developed dual control strategy utilized in this study forms a relatively inexpensive and less-complicated system that allows end-users to achieve lower failure rates during laser cladding (within its own limitations) and, therefore, through successful concurrent control of melt pool temperature and motion table feed rate provide better productivity and quality in the experimentally produced clad layers.

Thesis (Ph. D.)--Oregon Graduate Center, 1974.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 97-103). Available also in a digital version from Dissertation Abstracts.

No description available.