This thesis is concerned with the characterisation of sub-millimetre sized solid-state lasers. These 'microchip lasers' are examined in two forms; one as monolithic devices where the dielectric mirrors forming the laser cavity are directly deposited onto two near parallel faces of the laser gain crystal, and the second where the microchip gain material is used in combination with a nonlinear crystal to form a composite device. A range of neodymium doped crystals, operating continuous wave and in gain-switched mode at 1064nm, are compared as potential microchip laser gain materials, including Nd:YVO₄, Nd:YOS, Nd:SFAP and Nd:SVAP. With the exception of Nd:SVAP, slope efficiencies exceeding 40% and thresholds of less than 100mW were measured for all these lasers. A comparison of the 1064nm and 1342nm transitions in Nd:YVO₄ is also carried out showing similar performance for both transitions. The formation of the cavity within these monolithic lasers is described in detail, in particular for the thermal and gain guiding effects in Nd:YVO₄. Both analytical and numerical modelling of these effects are compared with experimental measurement of the cavity formation. When used in conjunction with a saturable absorber, these sub-millimetre sized lasers can be used to produce short, high-intensity pulses. This is demonstrated using Cr:YAG as a saturable absorber for Nd:YVO₄ at 1064nm to produce pulses as short as 1.38ns and peak powers of up to 1kW, and V:YAG to Q-switch Nd:YVO₄ at 1342nm to produce pulses with durations as short as 9.5ns and peak powers up to 360W. Active control for generating pulses is also demonstrated using a novel range of deflective Q-switches. These low cost, low loss, compact devices produced pulses of up to 12kW peak power and pulses duration of less than 1.1ns on demand. The continuous wave, intracavity frequency doubling of the three main ND³⁺ transitions, to give red, green and blue light is described. Up to 220mW of green light, with an efficiency approaching 40%, 33mW of blue light and 10mW of single-frequency red light were produced.

No description available.

Call number: LD2668 .T4 1986 F46 / Master of Science / Mechanical and Nuclear Engineering

Q-switched operation of a holmium-doped fluoride fiber laser at 1.2 mu m wavelength induced by a semiconductor saturable absorber mirror (SESAM) is reported. 650 ns pulses with 0.13 mu J pulse energy at a repetition rate of 260 kHz were obtained.

Neste trabalho, são apresentados os detalhes do projeto, da construção e do desenvolvimento de um laser de CO2 de alto fluxo. O trabalho surgiu de necessidades específicas do Laboratório de Desenvolvimento de Aplicações de Laser e Óptica (DedALO) da Divisão de Fotônica do IEAv, onde é necessário um laser de CO2 contínuo, com potência da ordem de 1 kW e que possa ser operado como amplificador de um oscilador pulsado de baixa potência, para aplicações em processamento de materiais, propulsão a laser e evaporação de metais utilizados nos projetos de separação isotópica. Por meio de estudos teóricos e observações práticas, procurou-se reunir o maior número de dados disponíveis para a montagem de lasers de CO2 de alto fluxo. São apresentados os detalhes de projeto da cavidade ressonante, do trocador de calor, resistor ballast, sistema de vácuo, sistema elétrico e sistema de fluxo. São também descritos os componentes, a sua montagem, técnicas de alinhamento de espelhos, medição de potência e de fluxo. Com o primeiro protótipo foram obtidos 200 W de potência contínua, uma eficiência de conversão de energia elétrica em óptica de 13%, quando operando com uma pressão ótima de 24 Torr (3200 Pa) de uma mistura padrão de 10% de CO2, 10% de N2, 80% de He, com uma vazão de 0,121 m3/s. Estes resultados são comparados com os previstos pelos modelos utilizados e é verificada uma boa concordância entre eles.

by Ip Tak-wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 62-64.

by Chan, Siu Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 65.

by So-kuen C. Liew. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [40-45, 3rd gp.]) and index. / Abstract --- p.ii / Acknowledgments --- p.iv / Table of Contents --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Distributed Feedback Lasers --- p.1 / Chapter 1.2 --- Computer Model --- p.6 / Chapter 1.3 --- Analyses --- p.8 / Chapter 1.4 --- Organization of Thesis --- p.11 / Chapter 2 --- Computer Model --- p.13 / Chapter 2.1 --- Comparison of Theoretical Models --- p.15 / Chapter 2.2 --- Assumptions and Approximations --- p.17 / Chapter 2.2.1 --- Longitudinal Spatial Hole Burning --- p.17 / Chapter 2.2.2 --- Spontaneous Emission --- p.18 / Chapter 2.2.3 --- Nonlinear Gain Saturation --- p.19 / Chapter 2.2.4 --- Carrier-Induced Index Change --- p.20 / Chapter 2.2.5 --- Single-mode Operation Assumption --- p.22 / Chapter 2.2.6 --- Otbers --- p.22 / Chapter 2.3 --- Theories and Approaches --- p.25 / Chapter 2.3.1 --- Coupled Wave Theory --- p.25 / Description --- p.25 / Stop-Band --- p.29 / Second-Order DFB Laser --- p.30 / DFB Designs To Improve SMSR --- p.30 / Chapter 2.3.2 --- Transfer Matrix Approach --- p.32 / Chapter 2.4 --- Above-Threshold Model --- p.34 / Chapter 2.4.1 --- Introduction --- p.34 / Chapter 2.4.2 --- Formalism --- p.36 / Facet Output Power and Optical Spectrum --- p.39 / Photon Density Distribution --- p.41 / Variance of Photon Density Distribution --- p.42 / Nearfield Distribution --- p.42 / Surface Emission --- p.43 / Power-Current Characteristics --- p.44 / Optical spectrum --- p.45 / Subthreshold Analysis --- p.47 / Linear Yield Analysis --- p.47 / Chapter 2.4.3 --- Computer Implementation --- p.48 / Flowchart --- p.48 / Subroutines --- p.52 / "Runtime, Numerical Stability" --- p.56 / Chapter 2.5 --- "Discussion,Summary and Future Work" --- p.59 / Chapter 2.5.1 --- Validation of the DFB Model --- p.59 / Chapter 2.5.2 --- Summary --- p.67 / Chapter 2.5.3 --- Topics for Future Work in Theoretical Modeling --- p.68 / Chapter 3 --- Analysis of DFBDBR Laser --- p.72 / Chapter 3.1 --- Introduction --- p.72 / Chapter 3.2 --- Subthreshold Analysis --- p.78 / Chapter 3.2.1 --- Introduction --- p.78 / Chapter 3.2.2 --- Results --- p.81 / Symmetric End-Sections --- p.81 / Asymmetric End-Sections --- p.85 / Chapter 3.3 --- Above-threshold Analysis --- p.88 / Chapter 3.3.1 --- Analysis --- p.89 / Chapter 3.3.2 --- Length Ratio --- p.92 / Chapter 3.3.3 --- Design Plot --- p.99 / Chapter 3.3.4 --- Longitudinal Spatial Hole Burning --- p.102 / Chapter 3.3.5 --- Effective Linewidth Enhancement Factor --- p.104 / Chapter 3.3.6 --- Asymmetric DFBDBR --- p.107 / Chapter 3.4 --- Conclusion --- p.109 / Chapter 4 --- Analysis of Complex-Coupled DFB --- p.110 / Chapter 4.1 --- Introduction --- p.110 / Chapter 4.2 --- Laser Structure --- p.113 / Chapter 4.2.1 --- Grating Layer --- p.114 / Chapter 4.2.2 --- Parameter Values --- p.119 / Chapter 4.3 --- Above-Threshold Analysis of CCDFB --- p.122 / Chapter 4.3.1 --- Threshold Current --- p.122 / Grating Duty Cycle = 0.36 --- p.122 / Grating Duty Cycle = 0.15 --- p.128 / Chapter 4.3.2 --- Power Efficiency --- p.131 / Grating Duty Cycle = 0.36 --- p.131 / Grating Duty Cycle = 0.15 --- p.136 / Chapter 4.3.3 --- Summary --- p.137 / Chapter 4.4 --- Yield Analysis of LCDFB and QWDFB --- p.138 / Chapter 4.4.1 --- Introduction --- p.138 / Chapter 4.4.2 --- Method --- p.140 / Chapter 4.4.3 --- Results --- p.141 / Facet Phase Angle --- p.141 / Quarterwave Phase-Shifted DFB Laser --- p.144 / Loss-Coupled DFB Laser --- p.148 / Chapter 4.5 --- Conclusion --- p.154 / Chapter 5 --- Summary and Conclusion --- p.157 / Chapter 5.1 --- Summary --- p.157 / Chapter 5.1.1 --- Summary of Major Contributions --- p.157 / Chapter 5.1.2 --- Summary of Modeling and Validation --- p.159 / Chapter 5.1.3 --- Summary of Model Applications --- p.160 / DFBDBR Laser --- p.161 / Loss-Coupled DFB Laser --- p.162 / Chapter 5.2 --- Topics for Future Studies --- p.163 / References --- p.R-l / Appendices --- p.A-l / Chapter A. --- Derivations --- p.A-l / Chapter A.1 --- Noise Power --- p.A-l / Chapter A.2 --- Product of Field Vector and Its Adjoint --- p.A-2 / Chapter A.3 --- Gain-Coupling Coefficient --- p.A-5 / Chapter B. --- Subroutines in Computer Program --- p.A-8 / Chapter B.l --- Subroutines in 'drive.f' --- p.A-8 / Chapter B.2 --- Subroutines in 'Core.f' --- p.A-9 / Chapter B.3 --- Subroutines in 'initiaLf' --- p.A-13 / Chapter B.4 --- Subroutines in ´بmisc.f' --- p.A-14 / Chapter C. --- List of Figures --- p.A-17 / Chapter D. --- List of Tables --- p.A-22 / Chapter E. --- List of Abbreviations and Acronyms --- p.A-23 / Chapter F. --- List of Symbols --- p.A-24 / Chapter G. --- List of Publications --- p.A-27 / Index --- p.I-1

by Ho Hing Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Table of Contents --- p.v / Chapter 1 --- Introduction / Chapter 1.1 --- Background of optical generation of millimeter-waves --- p.1 -1 / Chapter 1.2 --- Application of the two-section DFB laser on optical generation of millimeter-waves --- p.1 -4 / Chapter 1.3 --- Analysis --- p.1-4 / Chapter 1.4 --- Organization of Thesis --- p.1 -5 / References --- p.1-6 / Chapter 2 --- Techniques of Optical Generation of Millimeter-waves / Chapter 2.1 --- Direct modulation and mode-locking of lasers --- p.2-1 / Chapter 2.2 --- Beating of two optical waves --- p.2-3 / References --- p.2-11 / Chapter 3 --- Experimental Results and Discussions / Chapter 3.1 --- Device structure and experimental setup --- p.3-1 / Chapter 3.2 --- Light-Current Characteristics of the two-section laser --- p.3-3 / Chapter 3.3 --- Spectral behaviours of the two-section DFB laser --- p.3-5 / Chapter 3.3.1 --- Linewidth of the two-section DFB laser --- p.3-5 / Chapter 3.3.2 --- Wavelength tuning of the two-section DFB laser --- p.3-5 / Chapter 3.3.3 --- Biasing conditions for the dual-mode oscillations --- p.3-16 / Chapter 3.4 --- Optical generation of millimeter-waves --- p.3-17 / Chapter 3.4.1 --- Mechanism of beating --- p.3-17 / Chapter 3.4.2 --- Generation of millimeter-waves by optical beating --- p.3-20 / Chapter 3.5 --- Optical Transmission of the millimeter-waves --- p.3-22 / References --- p.3-24 / Chapter 4 --- Theory of DFB Laser / Chapter 4.1 --- Development of DFB laser --- p.4-1 / Chapter 4.2 --- Structure of DFB laser --- p.4-2 / Chapter 4.3 --- Model of one-section DFB laser --- p.4-4 / Chapter 4.4 --- Analysis of two-section DFB laser --- p.4-10 / Chapter 4.4.1 --- Introduction of transfer matrix method --- p.4-11 / Chapter 4.4.2 --- Formulation of transfer matrix --- p.4-12 / Chapter 4.4.3 --- Application of the transfer matrix --- p.4-13 / References --- p.4-17 / Chapter 5 --- Numerical Analysis of the Spectral Behaviours of the Two-Section DFB Laser / Chapter 5.1 --- Solving the Transcendental Equation --- p.5-1 / Chapter 5.2 --- Simulation of the spectral behaviour of the two-section DFB laser --- p.5-4 / Chapter 5.2.1 --- Assumptions and Approximations --- p.5-4 / Chapter 5.2.2 --- Parameters --- p.5-5 / Chapter 5.2.3 --- Computer Implementation --- p.5-6 / Chapter 5.2.4 --- Results and Discussion --- p.5-7 / References --- p.5-14 / Chapter 6 --- Conclusion / Chapter 6.1 --- Summary --- p.6-1 / Chapter 6.2 --- Future works --- p.6-2 / Appendices / Appendix A Source code for simulation of spectral behaviours of the two-section DFB laser --- p.A-1

Orientadores: Ester M. Danielli Nicola, Konradin Metze / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-09-11T20:53:00Z (GMT). No. of bitstreams: 1 Mariuzzo_AdrianadeAzevedoCoutinho_M.pdf: 3799006 bytes, checksum: 0027772915214bb19353e486cceceb9e (MD5) Previous issue date: 1997 / Resumo: o presente trabalho mostra alguns aspectos da interação do laser 1com o tecido. As propriedades fisicas do laser são relatadas com o objetivo de explicar a razão dos seus diversos modos de atuar sobre os diferentes tecidos. o dano tecidual depende de vários parâmetros fisicos e biológicos, como: potência,tempode exposiçãoao laser,distânciafocal,diâmetrodo raio e tipo de tecido. o laser de C02, escolhido para realização deste trabalho, atua como um "bisturi cirúrgico" através da grande eficiência na conversão de sua radiação infravermelha em calor localizado. Tal característica faz com que seja, ainda, o mais utilizado na área médica, principalmente nas cirurgias. Neste estudo são revistas e discutidas diversas características do tecido muscular estriado, no sentido de explicar as peculiaridades das lesões conseqüentes à aplicação do laser C02. Dependendo da forma como os parâmetros do laser forem combinados, os efeitos podem variar, desde cortes profundos até cauterização. Foi demonstrado que ao serem utilizadas potências e tempos diferentes, mesmo mantendo constante energia total em uma dada área de tecido, as lesões causadas apresentam-se morfologicamente diferentes. . Os diferentes conjuntos de lesões resultantes da utilização do laser nas condições acima mencionadas foram analisados morfometricamente, sob microscopia óptica, imediatamente à aplicação, bem como após 1,4, 7, 15 e 21 dias. As alterações histológicas foram avaliadas e discutidas do ponto de vista quantitativo e qualitativo. Comparando o processo de reparação tecidual dos dois conjuntos extremos, constatamos diferenças significativas que permitiram considerar que a reparação de lesões causadas em condições de alta potência e curto tempo evolui de forma mais avançada, superando aquela das lesões conseqüentes à aplicação de baixa potência e longo tempo / Abstract: The aim of our studywas to comparebiologic effects such astissue damageand regeneration in rat skeletal musc1eafter C02 laser application with pulses of constant energy density, but with varying power and exposuretime. We used three different laser conditions: 20W x O.5s,10W x 1.0s and 5.0 W x 2.0s, alI having the sameenergy density (10 joules in a constant area). The animalswere sacrificedimmediatelyafter laser application,and after 1,4, 7, 15 and 21 days. Tissue damage produced by the C02 laser with high power provokes more profound craters with less tissue damage at the margins, as shown by lesser tissue carbonization, fewer foreign body giant cell granulomas and less tissue fibrosis and, on the other hand, an accelerated regeneration of muscle tissue / Mestrado / Mestre em Neurociencias