by Kwok Chi Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references. / Abstract / Acknowledgements / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Basic Concepts of Lasers and Simple Survey of Laser Theories --- p.4 / Chapter 2.1 --- Introduction --- p.4 / Chapter 2.1.1 --- Basic Structure of a Laser --- p.4 / Chapter 2.1.2 --- "Concepts of "" Mode"" arid "" Mode-Locking""" --- p.6 / Chapter 2.2 --- Brief Review of Laser Theories --- p.9 / Chapter 2.3 --- Other Simple Models --- p.12 / Chapter 2.4 --- Review of the Maxwell-Bloch Equations --- p.17 / Chapter 2.4.1 --- Derivation of Maxwell-Bloch Equations --- p.17 / Chapter 2.4.2 --- Continuous-Wave Operation --- p.23 / Chapter 2.4.3 --- Mean-Field Approximation and Lorenz-Haken Instability --- p.24 / Chapter 2.4.4 --- Adiabatic Elimination of Fast Variables --- p.26 / Chapter 2.4.5 --- Thin-Sheet-Gain Approximation for Multimode Lasers --- p.30 / Chapter 2.4.6 --- Self-Mode-Locking Predicted by Using Maxwell-Bloch Equations --- p.33 / Chapter 2.4.7 --- Hysteresis Phenomena in Switching the Cavity Detuning --- p.35 / Chapter 3. --- "Moving-Mirror ""Mode-Locking""" --- p.41 / Chapter 3.1 --- Conventional Laser Mode-Locking --- p.41 / Chapter 3.1.1 --- Preliminaries： What is Mode-Locking (Conventional) ？ --- p.41 / Chapter 3.1.2 --- Active Mode-Locking and Passive Mode-Locking --- p.43 / Chapter 3.1.3 --- Spectra of Conventional Mode-Locked Lasers --- p.49 / Chapter 3.2 --- Moving-Mirror Mode-Locking --- p.50 / Chapter 3.2.1 --- Historical Notes --- p.50 / Chapter 3.2.2 --- Previously Proposed Explanations --- p.54 / Chapter 3.3 --- MMML Mechanism: our Proposal --- p.59 / Chapter 3.3.1 --- Relation between MMML Lasers and FSFC Lasers --- p.60 / Chapter 3.3.2 --- Concept of Moving Modes --- p.62 / Chapter 3.3.3 --- How are the Moving Modes Locked ？ --- p.64 / Chapter 3.4 --- Numerical Simulations ´ؤ Method and Results --- p.68 / Chapter 3.4.1 --- Description of Our Numerical Model --- p.68 / Chapter 3.4.2 --- Tests on the Simulation Method --- p.71 / Chapter 3.4.3 --- Ultrashort Pulses Generation of a MMML Laser --- p.73 / Chapter 3.4.4 --- Modulation of the Pulses --- p.74 / Chapter 3.4.5 --- Broadband or Discrete Spectra ？ --- p.75 / Chapter 3.4.6 --- Different Operation Regimes in MMML Lasers --- p.79 / Chapter 3.4.7 --- Why Period-T/2 Pulses --- p.84 / Chapter 3.4.8 --- Auto-Correlation Function of the Electric Field --- p.86 / Chapter 3.4.9 --- FSFC Laser with Injection Signal --- p.87 / Chapter 3.4.10 --- MMML in Class C Laser: d = 1.0 --- p.88 / Chapter 3.4.11 --- Exciting the Relaxation Oscillation Resonance --- p.89 / Chapter 4. --- Discussion and Conclusion --- p.92 / Chapter 4.1 --- Limitation of (Conventional) Thin-Sheet-Gain Approximation --- p.92 / Chapter 4.1.1 --- Problem with the Conventional Thin -Sheet-Gain Approximation --- p.92 / Chapter 4.1.2 --- Modified Thin-Sheet-Gain Approximation --- p.93 / Chapter 4.2 --- Concluding Remarks; Possibilities of Further Research --- p.97 / References and Notes / Appendix: Source Codes of the Fortran Program

by Lam King Shun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [40-41]). / by Lam King Shun. / Acknowledgement --- p.i / Biographical Sketch --- p.ii / Abstract --- p.iii / Table of Contents --- p.iv / Chapter Chapter One --- Introduction --- p.1 / Chapter Chapter Two --- The Sol-Gel Derived Silica / Chapter 2.1 --- Introduction to the so-gel science --- p.3 / Chapter 2.2 --- The procedure of the silica formation --- p.5 / Chapter 2.3 --- During the sol-gel process --- p.7 / Chapter 2.4 --- The silica characterization --- p.12 / Chapter 2.4.1 --- Physical properties --- p.12 / Chapter 2.4.2 --- Optical properties --- p.13 / Chapter 2.5 --- Sample preparation --- p.15 / Chapter Chapter Three --- Laser Experiments / Chapter 3.1 --- Basic principle of dye laser --- p.16 / Chapter 3.2 --- Experimental procedure --- p.20 / Chapter 3.3 --- Data and discussion --- p.23 / Chapter 3.3.1 --- Spectral and temporal behaviour --- p.2 3 / Chapter 3.3.2 --- The performance of the sol-gel silica laser --- p.37 / Chapter Chapter Four --- Conclusions and Suggestions for Further Work --- p.39 / References

by Sui-Pan Yam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Abstract also in Chinese. / Acknowledgements --- p.V / Abstract --- p.VI / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter 1.1) --- Tunable Multi-Wavelength Optical Sources --- p.1 -1 / Chapter 1.2) --- All-Optical Switching --- p.1 -3 / Chapter 1.2.1) --- Nonlinear Effect / Chapter 1.2.2) --- Special Design of the Laser Structure / Chapter 1.2.3) --- Self-Injection Seeding of Fabry-Perot Laser Diode / Chapter 1.3) --- About This Project --- p.1-6 / Chapter Chapter 2 --- Basic Theory --- p.2-1 / Chapter 2.1) --- Mechanism of Gain-Switching --- p.2-1 / Chapter 2.1.1) --- General Description / Chapter 2.1.2) --- "Optical Pulsewidth, Spectra, and Frequency Chirping of Gain-Switched Pulses" / Chapter 2.2) --- Mechanism of Self-Injection Seeding --- p.2-8 / Chapter 2.2.1) --- General Description / Chapter 2.2.2) --- Dynamics of Single-Mode Formation / Chapter 2.2.3) --- Frequency Evolution of the Laser Diode for Cavity Mode Selection / Chapter 2.2.4) --- Turn-On Delay Time Jitter (TOJ) / Chapter 2.3) --- Mechanism of Injection Seeding --- p.2-17 / Chapter 2.3.1) --- General Description / Chapter 2.3.2) --- The Model of Weak Injection / Chapter 2.3.3) --- The Model of Strong Injection / Chapter Chapter 3 --- Single- and Multi-wavelength Optical Pulses Generated by a Diffraction Grating --- p.3-1 / Chapter 3.1) --- Introduction --- p.3-1 / Chapter 3.2) --- Basic Principle --- p.3-2 / Chapter 3.3) --- Experimental Setup --- p.3-5 / Chapter 3.4) --- Results and Discussion --- p.3-7 / Chapter 3.4.1) --- Spectral Characteristics Analysis / Chapter 3.4.2) --- Individually Access of the Four-Wavelength Output / Chapter 3.4.3) --- The Optical Pulsewidth Characteristics / Chapter 3.4.4) --- Discussion / Chapter 3.5) --- Summary --- p.3-14 / Chapter Chapter 4 --- Using a Highly Dispersive Fiber for Tunable Multi-Wavelength Pulse Generation --- p.4-1 / Chapter 4.1) --- Introduction --- p.4-1 / Chapter 4.2) --- Basic Principle --- p.4-2 / Chapter 4.3) --- Experimental Setup --- p.4-5 / Chapter 4.4) --- Experimental Results --- p.4-7 / Chapter 4.4.1) --- Spectral and Temporal Characteristics / Chapter 4.4.2) --- Wavelength Tuning / Chapter 4.4.3) --- Individually Access of Two Wavelength Channels / Chapter 4.4.4) --- Multi-Wavelength Generation / Chapter 4.5) --- Summary --- p.4-13 / Chapter Chapter 5 --- Comparison of Two Self-Seeding Configurations --- p.5-1 / Chapter 5.1) --- Introduction --- p.5-1 / Chapter 5.2) --- Polarization Sensitivity --- p.5-1 / Chapter 5.3) --- Stability --- p.5-2 / Chapter 5.4) --- Tunability --- p.5-2 / Chapter 5.5) --- Simplification --- p.5-3 / Chapter 5.6) --- Summary of the advantages and disadvantages of Two Configurations --- p.5-4 / Chapter Chapter 6 --- All-Optical Wavelength Switching achieved by Self-Seeding and External Injection-Seeding --- p.6-1 / Chapter 6.1) --- Introduction --- p.6-1 / Chapter 6.2) --- Experimental Setup --- p.6-2 / Chapter 6.3) --- Results and Discussion --- p.6-4 / Chapter 6.3.1) --- Spectral Characteristics / Chapter 6.3.2) --- The Optical Pulsewidth / Chapter 6.3.3) --- The Optical Switching Behaviors / Chapter 6.3.4) --- The Detail Information of Switching / Chapter 6.3.5) --- Optical Power / Chapter 6.4) --- Summary --- p.6-10 / Chapter Chapter 7 --- A Novel Self-Injection Seeding Scheme --- p.7-1 / Chapter 7.1) --- Introduction --- p.7-1 / Chapter 7.2) --- Basic Principle --- p.7-2 / Chapter 7.3) --- Experimental Setup --- p.7-9 / Chapter 7.4) --- Results and Discussion --- p.7-11 / Chapter 7.4.1) --- Spectral and Temporal Characterizations of Two-Wavelength Switching / Chapter 7.4.2) --- Different Wavelength Selection / Chapter 7.4.3) --- Operation Frequency Against the Fiber Length / Chapter 7.4.4) --- Multi-Wavelength Generation / Chapter 7.5) --- Discussion --- p.7-20 / Chapter 7.6) --- Summary --- p.7-22 / Chapter Chapter 8 --- Comparison of Switching Methods --- p.8-1 / Chapter 8.1) --- Introduction --- p.8-1 / Chapter 8.2) --- Switching between Self-Seeding and Injection-Seeding --- p.8-1 / Chapter 8.3) --- Switching by Self-Seeding of a F-P Laser Diode --- p.8-2 / Chapter 8.4) --- Summary --- p.8-3 / Chapter Chapter 9 --- Conclusion --- p.9-1 / References / Figure Captions / Appendix 一 Equipment Descriptions / List of Accepted and Submitted Publications

The objectives of this thesis were to develop a methodology for the measurement of laser beam characteristics from a single cavity laser and to establish a preliminary guideline that would determine which crystals were acceptable for use in production of laser devices. These objectives were achieved by developing the experimental procedures and by statistical analysis of the data obtained. However, additional future work is needed to independently confirm the results of this thesis. Efficient and reliable operation of a lamp-pumped Nd:YAG laser is highly dependent on the crystal from which the beam is derived. However little attention is given to the quality of the laser beam produced by each crystal. Although many factors influence the output beam, the power dependent focal length is of particular importance. Unfortunately, direct measurement of the crystal focal length is not possible with a Nd:YAG laser beam. This is because the single cavity laser functions as both a resonator and amplifier simultaneously. Therefore, a method was developed that measured the caustic of the laser beam after it had emerged from the resonator and been focused by means of a focusing element. The caustic of the beam was analyzed utilizing a beam analyzer that calculated the beam focusability factor and the beam waist size. From this information, the waist diameter at the outcoupler mirror was calculated using Gaussian beam propagation principles. A resonator model was developed based on the self-repeating ABCD matrix that allowed for the determination of the induced thermal lens based on the input power. Several approaches to model the thermal lensing effect were taken, each with increasing complexity. As a result, three parameters were evaluated with the intention of using one or more as a means to classify good and bad crystals. They were the crystal sensitivity factor, the beam focusability factor, and the beam waist size at the measurement plane. Calculation of the crystal sensitivity factor, M^-1, was based on the developed resonator model and numerous approximations of the crystal behavior. Thus, after calculating the M-1 factor as a function of input power, no distinguishable pattern was seen. However, the beam focusability factor and the beam size, both showed distinct regions that separate good and bad crystals. Statistical analysis performed on the data supports a preliminary conclusion that these two parameters may be used as a quality control measure. These parameters are measured using existing internationally accepted procedures and are therefore the best currently available tools for determination of the quality of Nd:YAG crystals.

Orientador: Michelle Bianchi de Moraes / Coorientador: Fernando Vagner Raldi / Banca: Andrea Carvalho De Marco / Banca: Fábio da Silva Matuda / Resumo: A exodontia de terceiros molares inferiores é uma prática comum nas clínicas odontológicas, porém o pós-operatório inerente a esta cirurgia apresenta dor, edema e trismo. Algumas das posições de inclusão do terceiro molar podem acarretar comprometimento periodontal nos segundos molares adjacentes. Com isso o presente trabalho buscou desenvolver através deste estudo clínico controlado, um protocolo com o laser de baixa intensidade para aplicação no pós-operatório das exodontias de terceiros molares mandibulares, de modo a minimizar os sinais e sintomas e melhorar os parâmetros periodontais dos segundos molares adjacentes. O laser empregado foi o Photon Laser III - DMC, São Carlos, SP/Brasil - como meio de condução o vermelho, com comprimento de onda 660 nm, potência útil de 30 mW, meio ativo AsGaAl. Sessenta pacientes de ambos os gêneros, com necessidade de exodontia dos terceiros molares, em classificações padrões de posição, foram randomizados em três grupos para análise - Grupo I: 10J/cm2, Grupo II: 30J/cm2 e Grupo III: Sham, e acompanhados pelo período de 6 meses. A análise do trismo e edema facial no pós-operatório e do nível clínico de inserção encontraram diferenças estatísticas significantes entre os grupos que receberam a terapia laser quando comparado ao grupo sham. Portanto, a utilização do laser de baixa intensidade como terapia adjuvante após a exodontia de terceiros molares demonstrou efetividade. Sendo que o Grupo I se destacou, após seis meses de avaliação. / Mestre

by Ka-Suen Lee. / "June 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Le contrôle de la différence de fréquence entre deux lasers est un défi transversal à de nombreux domaines de la photonique, que ce soit dans un but de génération hétérodyne d'un battement micro-onde de grande pureté, ou pour des expériences de métrologie ou de télécommunication. L'avancée des connaissances sur la dynamique de lasers soumis à divers couplages a permis le développement de méthodes de stabilisation basées sur l'injection optique. Nous étudions ici théoriquement et expérimentalement un mécanisme appelé réinjection décalée en fréquence (RDF), qui permet dans des situations variées de contrôler précisément la différence de fréquence entre deux lasers. Dans un premier temps, la méthode RDF est appliquée à un laser à état solide bi-polarisation bi-fréquence Nd:YAG afin de verrouiller en phase ses deux modes de polarisation orthogonaux. Le développement d'un modèle type «rate equations» en bonne adéquation avec les expériences a aussi permis de mettre en lumière un certain nombre de régimes de synchronisation partielle dits de phase bornée. De plus, nous montrons que cet état peut subsister en présence d'oscillations chaotiques de l'intensité et de la phase. Le comportement du laser sous RDF est étudié pour différentes valeurs du désaccord de fréquence, du taux d'injection, du retard éventuel, et du couplage inter-modes. Enfin, la nécessité d'inclure un couplage phase-amplitude (facteur de Henry non-nul) dans le modèle a mené au développement d'une méthode pour mesurer ce coefficient habituellement négligé dans les lasers solides. Le mécanisme de stabilisation par RDF est ensuite appliqué à un composant semiconducteur original contenant deux lasers DFB sur InP. Malgré une plus grand complexité du schéma de couplage, et la présence de retards effectifs importants, il reste possible de synchroniser en phase ces lasers. Des bandes d'accrochages liées au retard sont observées, et reproduites à l'aide d'un modèle numérique. Ce dernier permet aussi de déterminer les conditions de fonctionnement minimisant l'influence de paramètres expérimentaux non maîtrisés. Enfin, ce système, permettant de contrôler une phase micro-onde sur porteuse optique, peut être intégré dans une boucle résonante de type oscillateur opto-électronique (OEO) qui ne nécessite pas de référence externe. On réalise un oscillateur micro-onde sur porteuse optique auto-référencé, à bande latérale unique, ayant des performances encourageantes. Dans ce cadre, il semble que la plupart des techniques développées pour les OEO puissent être réinvesties. / The control of the frequency difference between two lasers is a cross-cutting challenge in many fields of photonics, either for the generation of high-purity heterodyne microwave beatnotes, or in metrology and telecommunication experiments. The advances of the comprehension of laser dynamics under various couplings has allowed to develop stabilization methods based on optical injection. We study here theoretically and experimentally a mechanism called frequency-shifted feedback (FSF), which allows to precisely control the frequency difference between two lasers in several situations.First, the FSF method is applied to a dual-frequency dual-polarization solid-state Nd:YAG laser, in order to lock the phases of its two orthogonal polarization modes. A model of rate equations is used to precisely describe the experiment, and allows to highlight partial "bounded phase" synchronization regimes. Furthermore, we show that in some cases this synchronization can subsist even with chaotic oscillations of the intensity and phase. The behavior of the laser under FSF is studied for varying values of the frequency detuning, injection rate, possible injection delay, and mode coupling in the active medium. Finally, we find that the inclusion of a phase-amplitude coupling (non-zero linewidth enhancement factor) is needed in the model to account for experimental observation. This leads to the development of an ad-hoc technique to measure the low value of this usually neglected factor in solid-laser lasers.The FSF stabilization mechanism is then applied to a custom semiconductor component embedding two DFB lasers overs InP. In spite of a more complex coupling scheme and the large effective delays into play, phase locking of the two lasers is possible. Due to the delay, locking bands appear when the detuning changes, and this behavior can be replicated using a numerical model. This model also permit to determine working conditions minimizing the influence of uncontrolled experimental optical feedback phases. Finally, as this system allows to control a microwave phase over an optical carrier, it can be integrated in a resonant loop not unlike an opto-electronic oscillator (OEO). We realized an oscillator generating a self-referenced, single sideband microwave signal over an optical carrier, with encouraging phase noise performances. In this case, it seems that most of the techniques that exist for standard OEO can be reused.

Active mode locking is one of the simplest ways to generate picosecond pulses at gigahertz repetition rates. In my works, I demonstrate the generation of picosecond pulses with a center-wavelength spanning from 1489nm to 1589nm using a polarization maintaining fiber loop mirror filter (PMF-LMF) in a mode-locked semiconductor optical amplifier (SOA) ring laser. By applying the SOA gain shifting technique and with the help of the controllable transmission ratio of the PMF-LMF, the tuning range of the output wavelength can be extended. By applying the technique of dispersion tuning, electrical wavelength tuning can be achieved across a range of 100nm. / Compared to the active mode-locking method, the regenerative mode-locking is very convenient because it does not require any external source for modulation and is proved to be more robust against fluctuations in ambient temperature. We demonstrate a 10-GHz regeneratively mode-locked fiber laser using a PMF-LMF. The operating frequency is determined by the free-spectral-range of the PMF-LMF and the component is extracted optically from the ring laser output. / In addition, we also demonstrate a simple technique to generate wavelength tunable picosecond pulses at adjustable repetition rate without using electrical or optical RF filter to extract the radio frequency (RF). The RF signal for mode locking is generated from a Fabry-Perot laser diode (FP-LD) under optical injection. The output frequency can be varied by adjusting the biasing current of the FP-LD. (Abstract shortened by UMI.) / Picosecond optical pulse sources with broad tunability and various repetition rates are key elements for applications in wavelength- and time-division multiplexed optical transmission systems. Mode-locking is one of the main techniques for the generation of optical pulses with high repetition rate picosecond pulse trains. This thesis presents our research efforts in high repetition rate optical pulse generation using active and regenerative mode-locking techniques, and a self-starting approach. We also demonstrate the application of harmonic mode locking in all-optical clock recovery from NRZ data. / Tang Wing Wa. / "August 2005." / Adviser: C. T. Shu. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 4015. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Zhu Xiao Lei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 116-121). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Orientador: Jose Luis Lage, Luiz Fernando Milanez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-11-08T18:36:48Z (GMT). No. of bitstreams: 1 Junqueira_SilvioLuizdeMello_D.pdf: 23366873 bytes, checksum: 40ff350275cdc60184b7883f90658798 (MD5) Previous issue date: 1996 / Resumo: O presente trabalho trata do estudo teórico e experimental dos efeitos térmicos causados pela aplicação da radiação laser sobre meios porosos e objetiva a determinação do coeficiente de atenuação de um meio poroso imerso em fluido. O modelamento matemático proposto utiliza a técnica dos volumes finitos, para resolver numericamente a equação do transporte do calor em coordenadas.cilíndricas. Um sistema de aquisição de dados baseado no conceito de instrumentos virtuais é elaborado para analisar o processo de aquecimento pela radiação de um laser de Argônio sobre uma matriz porosa de Alumínio 6101 imersa em quatro fluidos diferentes: ar, água, óleo polialfaolefina e Mercúrio. Uma metodologia inversa, estabelecida pela comparação de resultados numéricos e experimentais, é empregada para obter o coeficiente de atenuação da espuma metálica saturada. A análise inclui o emprego de duas metodologias de cálculo da condutividade térmica equivalente. Uma correlação entre os coeficientes de atenuação e um número de Prandtl equivalente do meio poroso é estabelecida / Abstract: In the present work, an investigation of thermal effects due to laser application is accomplished in order to determine the attenuation coeflicient of a porous matrix immersed in fluido The study included both theoretical and experimental analisys. In the theoretical analisys a numerical mo deI based on control volume method is developed to simulate the lasing process by solving the energy equation in cilindrical coordinates. A data acquisition system based on virtual instruments concept is elaborated to analyse the heating process result,ing from Argon Laser radiation over an Aluminum foam porous medium immersed in four different fluids, namely air, water, polyalphaolefin oil and Mercury. An inverse methodology, estabilished by comparison of numerical and experimental results, is used to obtain the attenuation coeflicient of the saturated metal foam. Calculations also included the use of two models for the effective thermal conductivity. Results indicated the existence of a linear correlation between laser attenuation and a defined equivalent Prandtl number / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica