Revestimentos superficiais são aplicados à muitas ferramentas de usinagem na indústria metalúrgica com o intuito de melhorar a eficiência de corte e aumentar sua vida útil. Neste trabalho foram realizados testes para remoção do recobrimento de nitreto de titânio alumínio (TiAlN) em pastilhas de carboneto de tungstênio (WC-Co), utilizando um feixe laser de pulsos ultracurtos. Após a determinação dos limiares de dano do filme e do substrato foram ablacionados na superfície do recobrimento, traços utilizando duas condições de ablação. Inicialmente operou-se no regime de baixa fluência do filme, e posteriormente no regime de baixa fluência do substrato, muito abaixo do limiar do filme, aplicando-se alta sobreposição de pulsos. Um sistema de espectroscopia de emissão atômica induzida por laser (LIBS) foi montado para monitoramento dos materiais presentes no plasma gerado pelo laser, porém o sistema não apresentou sensibilidade suficiente para leitura da baixa intensidade do plasma proveniente do processo e não foi utilizado. Após a análise dos traços por microscopia eletrônica, perfilometria óptica e espectroscopia por fluorescência de Raios-X, não foi possível determinar um processo seguro para realizar a remoção seletiva do filme em questão, porém, devido aos dados obtidos e observações dos resultados em alguns traços, novas possibilidades foram levantadas, abrindo a discussão para a realização de trabalhos futuros. / Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work.

A texturização por microusinagem a laser é uma importante alternativa para que se consiga melhorar a ligação de aderência entre materiais compósitos e o titânio, aplicados em componentes estruturais na indústria aeronáutica. A execução de texturização em chapas de titânio deve-se ao fato de que a técnica de junção preferida para muitos materiais compósitos é a ligação adesiva. Neste trabalho foram realizadas texturizações em chapas de titânio utilizando laser com pulsos ultracurtos de largura temporal da ordem de femtossegundos. Tal processo resultou em mínima transferência de calor para o material, evitando assim deformação superficial da chapa de titânio bem como a formação de material ressolidificado na região ablacionada. Estes inconvenientes ocorreram na utilização do laser chaveado com pulsos de nanossegundos. Foram executadas três tipos de texturizações utilizando laser com pulsos de femtossegundos, com variações nas distâncias entre as linhas usinadas. Pela análise das superfícies obtidas, detectou-se que a molhabilidade aumenta quando há o aumento da distância entre as linhas da texturização. Avançando nas análises, pela perfilometria óptica das superfícies texturizadas observou-se que há sensível aumento do volume disponível para penetração do adesivo estrutural quando são diminuídas as distâncias entre as linhas texturizadas. Nos ensaios de tração realizados observou-se que há o aumento da resistência ao cisalhamento da junta adesiva com a diminuição da distância entre as linhas texturizadas. / The texturing laser micromachining is an important alternative to improve the bonding adhesion between composites and titanium, which are applied to structural components in the aerospace industry. The texturing running on titanium plates is due to the fact that the preferred joining technique for many composite materials is the adhesive bonding. In this work, titanium plates were texturized using laser ultrashort pulses temporal widths of femtoseconds. This process resulted in minimal heat transfer to the material, avoiding deformation of the titanium plate surface as well as the formation of resolidified material in the ablated region. These drawbacks have occurred with the use of nanoseconds pulses. Were performed three types of texturing using laser with femtosecond pulses, with variations in the distances between the machined lines. The analysis of the obtained surfaces found that the wettability increases when there is the increased distance between the texturing lines. Advancing in the analysis by optical profilometry of textured surfaces was observed that there is substantial increase in the volume available for penetration of structural adhesive when the distances between the textured lines are diminished. In tensile tests conducted it was observed that there is an increase in shear strength of the adhesive joint by reducing the distance between the textured lines.

Foi desenvolvida e construída uma cavidade bombeadora para um meio de ganho de Cr:LiSAF na forma de bastão, bombeado por duas lâmpadas, visando sua operação como amplificador de pulsos ultracurtos a taxas de repetição elevadas, e com redução da carga térmica sobre o meio de ganho. A cavidade e o meio de ganho foram caracterizados sob operação como laser e como amplificador de pulsos ultracurtos. Atuando como laser, obtivemos 30 Hz de taxa de repetição e 20 W de potência média, resultado inédito, e ganho máximo de 1,5 por passagem. Alterando as características do bombeamento, foi possível operar o laser a 8 Hz e 16 W de potência média, com ganho máximo de 3,6 por passagem. A cavidade bombeadora, na configuração de maior ganho, foi integrada e sincronizada a um sistema Chirped Pulse Amplification baseado em cristais de Ti:Safira, concebido e construído visando a sua conjugação com o amplificador de Cr:LiSAF. O amplficiador introduziu um fator de amplificação de 150 em pulsos de 20 ps, produzindo pulsos com potência de pico de 0,5 TW. Também foi apresentada uma nova técnica para medida do limiar de ablação por pulsos ultracurtos, e sua teoria analítica foi desenvolvida. Esta técnica foi utilizada na determinação do limiar de ablação de cristais de Cr:LiSAF no regime de 20 ps. / We have developed and built a pumping cavity for a Cr:LiSAF rod, pumped by two flashlamps, in order to operate it as an ultrashort laser pulse amplifier at the highest possible repetition rate, under reduced thermal load. The pumping cavity and the gain medium were characterized under laser and ultrashort pulse amplifier operation. Operating as a laser, 30 Hz repetition rate and 20 W average power were obtained for the first time at a maximum gain per pass of 1.5. Changing the pumping characteristics, the laser provided 16 W at 8 Hz repetition rate, at a maximum gain of 3.6. The cavity, in the highest gain configuration, was integrated and synchronized to a Ti:Sapphire Chirped Pulse Amplification system, conceived and built to comprise the Cr:LiSAF amplifier. The amplifier provided amplification by a factor 150 to the 20 ps stretched pulses, resulting in pulses with 0.5 TW of peak power. Also, a new technique to measure ultrashort pulses ablation threshold was presented, and its analytical theory was developed. This technique was used to determine the ablation threshold for Cr:LiSAF crystals in the 20 ps regime.

by Chan Lai Yin Simon. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references. / Chapter Chapter 1: --- Introduction / Chapter 1.1 --- Background --- p.1-2 / Chapter 1.2 --- Properties of the InGaAsP quaternary alloy on InP substrate --- p.2 / Chapter 1.2.1 --- Physical Properties of In1-xGaxASyP1-y on InP substrate --- p.3-4 / Chapter 1.2.2 --- Optical Properties of In1-xGaxASyP1-y on InP substrate --- p.4-7 / Chapter 1.2.3 --- Nonlinear Optical Property of InGaAsP --- p.7-9 / Chapter 1.3 --- Fabrication of InGaAsP/InP rib waveguide / Chapter 1.3.1 --- Epitaxial Growth of In1-xGaxASyP1-y on InP substrate by MOCVD --- p.9 / Chapter 1.3.2 --- Etching of the five layer In1-xGaxASyP1-y slab waveguide --- p.9-12 / Chapter 1.4 --- Overview of the thesis --- p.12-13 / References --- p.13-15 / Chapter Chapter 2: --- Modal analysis of the single mode III-V semiconductor waveguidesin multi-layer rib structure by Effective Index Method / Chapter 2.1 --- Introduction --- p.16-17 / Chapter 2.2 --- Modal analysis of the rib waveguides --- p.17-27 / Chapter 2.3 --- Optical Confinement in rib waveguide --- p.28-30 / Chapter 2.4 --- Conclusions and discussions --- p.30-31 / References --- p.31-33 / Chapter Chapter 3: --- Ultrashort Pulsewidth Measurement Part I / Chapter 3.1 --- Introduction --- p.34 / Chapter 3.2 --- Pulsewidth measurement by streak camera --- p.34-37 / Chapter 3.3 --- Pulsewidth measurement by nonlinear autocorrelation --- p.37-40 / Chapter 3.3.1 --- Second Harmonic Generation Autocorrelator --- p.40-43 / Chapter 3.3.2 --- Two Photon Fluorescence Autocorrelator --- p.43-44 / Chapter 3.4 --- Two Photon Absorption Waveguide Autocorrelator --- p.45 / Chapter 3.4.1 --- TPA theory --- p.45-48 / Chapter 3.4.2 --- Autocorrelation Measurement by TPA in InGaAsP Waveguide --- p.48-51 / Chapter 3.4.3 --- The Estimated performance of the TPA Waveguide Autocorrelator --- p.52 / References --- p.52-57 / Chapter Chapter 4: --- Ultrashort Pulsewidth Measurement Part II: High Sensitivity Two Photon Absorption InGaAsP Waveguide Autocorrelator for Low Power Pulsewidth Measurement of 1.55μm Waveguide Pulses / Chapter 4.1 --- Introduction --- p.58-60 / Chapter 4.2 --- Waveguide structures --- p.60 / Chapter 4.3 --- Practical Implementation of the TPA Waveguide Autocorrelator / Chapter 4.3.1 --- Mirror arrangement for the delay system --- p.61 -63 / Chapter 4.3.2 --- Alignment and Coupling of the InGaAsP/InP Waveguide --- p.63-64 / Chapter 4.3.3 --- TPA photocurrent detection --- p.64-65 / Chapter 4.4 --- Experimental results --- p.65-67 / Chapter 4.4.1 --- Pulsewidth measurement of the TPA InGaAsP waveguide autocorrelator --- p.67-71 / Chapter 4.4.2 --- Spectral analysis by the TPA InGaAsP waveguide autocorrelator --- p.71 -73 / Chapter 4.5 --- Conclusions and discussions --- p.73-75 / References --- p.75-78 / Chapter Chapter 5: --- Picosecond Pulses Generation by Colliding-Pulse Mode-locking of a Fabry-Perot Laser Diode with an Intra-cavity Gradual Degradation Defect / Chapter 5.1 --- Introduction --- p.79-80 / Chapter 5.2 --- Gain-switching --- p.80-84 / Chapter 5.3 --- Colliding Pulse Mode-locking --- p.84-85 / Chapter 5.3.1 --- Degradation of diode laser --- p.85-86 / Chapter 5.3.2 --- CPM Theory --- p.86-89 / Chapter 5.3.3 --- Experimental results --- p.89-92 / Chapter 5.4 --- Conclusions and discussions --- p.92-93 / References --- p.94-98 / Chapter Chapter 6: --- Conclusions / Chapter 6.1 --- Summary of the Research / Chapter 6.1.1 --- Theoretical Results --- p.99-100 / Chapter 6.1.2 --- Experimental Results --- p.101-104 / Chapter 6.2 --- Future Development / Chapter 6.2.1 --- Improvement of the TPA InGaAsP waveguide autocorrelator --- p.105 / Chapter 6.2.2 --- Future development of III-V semiconductor waveguides --- p.105-107 / References --- p.107-108 / Appendix --- p.109-121

by Chow Kin Kee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgment --- p.v / Table of Contents --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Ultra-short Pulse Generation in Semiconductor Lasers --- p.2 / Chapter 1.2 --- Wavelength Selection and Switching in Short Pulses Generated from Semiconductor Laser --- p.4 / Chapter 1.3 --- Structure of the Thesis --- p.6 / Reference --- p.8 / Chapter 2. --- Principles and Theories --- p.10 / Chapter 2.1 --- Principle of Wavelength Switching in Self-Seeded Laser --- p.11 / Chapter 2.2 --- Principle of Synchronous Injection Seeding of two Lasers --- p.15 / Chapter 2.3 --- Principle of Fast Spectral Improvement in DFB Laser with Optical Feedback --- p.17 / Chapter 2.4 --- Principle of Spectrally Resolved Analysis --- p.19 / Reference --- p.24 / Chapter 3. --- Switching Dynamics between Single-Mode and Dual-Mode Pulse Emissions from a Self-Seeded Laser Diode --- p.25 / Chapter 3.1 --- Introduction --- p.26 / Chapter 3.2 --- Experimental Details and Discussion --- p.28 / Chapter 3.3 --- Summary --- p.37 / Reference --- p.38 / Chapter 4. --- Spectrally Resolved Analysis of Fast Tuning in Single-Mode Pulses Generated from Mutually Injection-Seeded Fabry- Perot Laser Diodes --- p.40 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Experimental Details and Discussion --- p.42 / Chapter 4.3 --- Summary --- p.51 / Reference --- p.52 / Chapter 5. --- Fast Spectral Improvement in Gain-Switched Pulses Generated from a Distributed Feedback Laser with Weak Optical Feedback --- p.54 / Chapter 5.1 --- Introduction --- p.55 / Chapter 5.2 --- Experimental Details and Discussion --- p.57 / Chapter 5.3 --- Summary --- p.65 / Reference --- p.66 / Chapter 6. --- Conclusion and Future Work --- p.67 / Chapter 6.1 --- Conclusion --- p.67 / Chapter 6.2 --- Future Works --- p.69 / Reference --- p.71 / Appendices --- p.A-l / Appendix A. List of Publications --- p.A-l / Appendix B. Modeling of Self-Seeded Fabry-Perot Laser --- p.A-2 / Appendix C. List of Figures --- p.A-4

by Anhui Liang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (p. D1-D4). / 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.

Lee Ka-lun. / "September 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / 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.

Tang Wing-Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Table of contents --- p.v / List of figure --- p.viii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Introduction to ultrashort optical pulse generation --- p.2 / Chapter 1.2. --- Introduction to wavelength-tunable pulse generation --- p.5 / Chapter 1.3. --- Introduction to chapters --- p.7 / Chapter 2. --- Principles and Theories --- p.11 / Chapter 2.1. --- Principle of dispersion tuning --- p.12 / Chapter 2.2. --- SOA nonlinear optical loop mirror --- p.16 / Chapter 2.3. --- Principle of dispersion tuning in harmonically mode-locked fiber laser using nonlinear optical loop mirror --- p.19 / Chapter 2.4. --- Principle of re-configurable multi-wavelength pulses generationin a self-seeded laser diode incorporating SOA loop mirror --- p.22 / Chapter 3. --- Rational harmonic mode-locking of an optically triggered fiber laser incorporating a non-linear optical loop modulator --- p.25 / Chapter 3.1. --- Introduction --- p.26 / Chapter 3.2. --- Experiment --- p.27 / Chapter 3.3. --- Result and discussion --- p.30 / Chapter 3.4. --- Summary --- p.37 / Chapter 4. --- Generation of amplitude-equalized optical pulses from a rational harmonic mode-locked fiber laser incorporating a SOA loop modulator --- p.40 / Chapter 4.1. --- Introduction --- p.41 / Chapter 4.2. --- Experiment --- p.42 / Chapter 4.3. --- Result and discussion --- p.44 / Chapter 4.4. --- Summary --- p.47 / Chapter 5. --- Optically controlled dispersion-tuning in harmonically mode-locked erbium doped fiber laser using SOA nonlinear loop modulator --- p.49 / Chapter 5.1. --- Introduction --- p.50 / Chapter 5.2. --- Experiment --- p.51 / Chapter 5.3. --- Result and discussion --- p.54 / Chapter 5.4. --- Summary --- p.58 / Chapter 6. --- Alternate method of constructing harmonically mode-locked fiber laser incorporating SOA nonlinear loop modulator --- p.60 / Chapter 6.1. --- Introduction --- p.61 / Chapter 6.2. --- Experiment --- p.62 / Chapter 6.3. --- Result and discussion --- p.65 / Chapter 6.4. --- Summary --- p.69 / Chapter 7. --- Optically re-configurable multi-wavelength pulse source constructed from a self-seeded laser diode --- p.71 / Chapter 7.1. --- Introduction --- p.72 / Chapter 7.2. --- Experiment --- p.74 / Chapter 7.3. --- Result and discussion --- p.77 / Chapter 7.4. --- Summary --- p.82 / Chapter 8. --- Tunable alternating multi-wavelength pulse source constructed using non-linear optical control of wavelength switching in a self-seeded laser diode --- p.85 / Chapter 8.1. --- Introduction --- p.86 / Chapter 8.2. --- Experiment --- p.87 / Chapter 8.3. --- Result and discussion --- p.89 / Chapter 8.4. --- Summary --- p.92 / Chapter 9. --- Conclusion and future works --- p.94 / Chapter 9.1. --- Conclusion --- p.94 / Chapter 9.2. --- Possible future works --- p.98 / Appendix / List of publications --- p.A-1

A texturização por microusinagem a laser é uma importante alternativa para que se consiga melhorar a ligação de aderência entre materiais compósitos e o titânio, aplicados em componentes estruturais na indústria aeronáutica. A execução de texturização em chapas de titânio deve-se ao fato de que a técnica de junção preferida para muitos materiais compósitos é a ligação adesiva. Neste trabalho foram realizadas texturizações em chapas de titânio utilizando laser com pulsos ultracurtos de largura temporal da ordem de femtossegundos. Tal processo resultou em mínima transferência de calor para o material, evitando assim deformação superficial da chapa de titânio bem como a formação de material ressolidificado na região ablacionada. Estes inconvenientes ocorreram na utilização do laser chaveado com pulsos de nanossegundos. Foram executadas três tipos de texturizações utilizando laser com pulsos de femtossegundos, com variações nas distâncias entre as linhas usinadas. Pela análise das superfícies obtidas, detectou-se que a molhabilidade aumenta quando há o aumento da distância entre as linhas da texturização. Avançando nas análises, pela perfilometria óptica das superfícies texturizadas observou-se que há sensível aumento do volume disponível para penetração do adesivo estrutural quando são diminuídas as distâncias entre as linhas texturizadas. Nos ensaios de tração realizados observou-se que há o aumento da resistência ao cisalhamento da junta adesiva com a diminuição da distância entre as linhas texturizadas. / The texturing laser micromachining is an important alternative to improve the bonding adhesion between composites and titanium, which are applied to structural components in the aerospace industry. The texturing running on titanium plates is due to the fact that the preferred joining technique for many composite materials is the adhesive bonding. In this work, titanium plates were texturized using laser ultrashort pulses temporal widths of femtoseconds. This process resulted in minimal heat transfer to the material, avoiding deformation of the titanium plate surface as well as the formation of resolidified material in the ablated region. These drawbacks have occurred with the use of nanoseconds pulses. Were performed three types of texturing using laser with femtosecond pulses, with variations in the distances between the machined lines. The analysis of the obtained surfaces found that the wettability increases when there is the increased distance between the texturing lines. Advancing in the analysis by optical profilometry of textured surfaces was observed that there is substantial increase in the volume available for penetration of structural adhesive when the distances between the textured lines are diminished. In tensile tests conducted it was observed that there is an increase in shear strength of the adhesive joint by reducing the distance between the textured lines.

This thesis details the development of ultra-short, single-walled carbon nanotubes (US-tubes) for use as nanocapsules to contain and deliver medical agents for both imaging (Gd3+ ) and therapeutic (211 At) purposes. In particular, Gd3+ -loaded US-tubes, known as gadonanotubes, operate as high-performance MRI contrast agents with relaxivities (image enhancement efficacy) a factor of 40-100 greater than current clinical contrast agents. Furthermore, gadonanotube relaxivities are highly pH-dependent, with image intensity nearly tripling from pH 7.5 to 6.8. Coupled with their high efficacies and targeting potential, these agents are promising candidates for next-generation targeted imaging probes for the early detection of cancer. Single gadonanotubes have also been encapsulated in a polymer shell for use as an intravenous MRI contrast agent. In addition, a new functionalization scheme has been developed to covalently attach a variety of amino acids in high quantity to the outer surface of the gadonanotubes and to attach a small peptide sequence for targeting breast cancer cells. The gadonanotubes have also been used as magnetic cell labeling agents, while also demonstrating efficacy in vivo as contrast agents. In addition to functioning as an imaging agent platform, the US-tubes have demonstrated efficacy as nanocapsules for radiotherapeutic agents. Astatine-211 (At-211), an α-emitting radionuclide, can be loaded inside the US-tube with excellent containment stability for the targeted delivery of an α-radiotherapeutic agent to micrometastatic and single-cell cancers. The loading levels for At-211 are comparable to, or better than, other known compounds. At-211, existing as the mixed-halogen compound 211 AtCl, is retained in the US-tube nanocapsules due to van der Waals forces between the 211AtCl and the interior sidewalls of the nanotube. Finally, the US-tubes have been shown to induce few health risks in mammalian experiments. Acute toxicity tests were conducted on mice with both raw and purified full-length carbon nanotubes (SWNTs), as well as US-tubes, using large doses (up to 1 g/kg of bodyweight). Even at these large doses, no animal death was recorded, although in a few cases behavioral changes were observed. Nanotubes were observed to be eliminated from the liver and kidneys through the urine and feces. It is believed that any toxicity at high doses can be attenuated (and prevented) by properly formulating the administered dose.