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1
Norrie, Callum. "Holosteric Nd:YAG lasers." Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/13755.
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A miniature Nd:YAG laser that was transversely pumped by a quasi-cw laser-diode array has been designed and constructed. This laser was injection seeded by a continuous wave single-frequency Nd:YAG laser that was also pumped by a laser- diode array. This was the first reported holosteric, or all-solid-state, laser that was capable of generating single frequency pulses in a high quality single transverse mode beam which it achieved at peak powers up to 7 kW. Two different types of laser-diode array were used in this work, and both have been characterised with respect to their use as pump sources for solid-state lasers. A fibre-coupled type SDL-2430-H2 laser-diode array, which emitted 100 mW from the end of a 100 mum core diameter fibre at the Nd:YAG absorption wavelength of 809 nm, was used to longitudinally pump a continuous wave Nd:YAG laser. Spatial hole-burning encouraged this laser to operate on several longitudinal modes, with an output power of up to 31 mW. With the addition of an etalon and a Brewster angled plate to the cavity of this laser, single longiuidinal mode operation was achieved at an output power level of 10 mW. The frequency from this laser was stabilised against thermal drift by phase sensitive locking to the resonance of an external reference cavity. The pump source for the transversely pumped Nd:YAG laser was an SDL-922-J quasi-cw laser-diode bar, which emitted from its 1 cm wide aperture pulses of 200 mus duration with energies up to 5 mJ at reperition rates between 10 - 100 pps. The characteristics of this laser-bar that were measured include a frequency chirp of 5 nm through the pulse, which was found to have a significant effect on the pumping of the Nd:YAG medium. An analysis of the pump-rate distribution throughout the Nd:YAG laser-rod was undertaken with reference to the transverse mode structure of this laser. This was used as the basis of a full rate-equation-based model of the transversely pumped laser. Fundamental transverse mode pulses with energies of 1.1 mJ were generated when the aperture provided by the Nd:YAG rod itself was used to suppress higher order modes. Upon Q-switching the transversely pumped laser using an acousto-optic modulator, single transverse mode pulses with peak power of up to 13 kW were produced. This laser was induced to operate on a single longitudinal mode by injection seeding with the single frequency diode-pumped laser. Operating at a peak power of 7 kW, this holosteric laser was particularly "well-behaved" with a pulse-to-pulse intensity stability of 6% over 100 pulses. A LiNbO3 electro-optic Q-switch configuration was implemented as optical damage to the acousto-optic component had limited the intracavity flux intensity. Development of these lasers towards higher peak power microlaser systems for applications including range-finding and surgery is continuing.
2
Bergström, David. "The absorptance of metallic alloys to Nd:YAG and Nd:YLF laser light." Licentiate thesis, Luleå tekniska universitet, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18217.
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In Laser Material Processing of metals, an understanding of the fundamental absorption mechanisms plays a vital role in determining the optimum processing parameters and conditions. The absorptance, which is the fraction of the incident laser light which is absorbed, depends on a number of different parameters. These include laser parameters such as intensity, wavelength, polarisation and angle of incidence and material properties such as composition, temperature, surface roughness, oxide layers and contamination. The vast theoretical and experimental knowledge of the absorptance of pure elements with smooth, contamination-free surfaces contrasts with the relatively sparse information on the engineering materials found in real processing applications. In this thesis a thorough investigation of the absorption mechanisms in engineering grade materials has been started. The Licentiate thesis consists of 5 papers. Paper 1 is a short review of some of the most important mathematical models used in describing the interaction between laser light and a metal. Paper 2 is a review of a few experimental methods of measuring the absorptance of an opaque solid such as a metal. Papers 3 and 4 are experimental investigations of the absorptance of some of the most frequently found metallic alloys used in Laser Material Processing today. Paper 5 is a co-authored paper on the cleaning of copper artefacts with the use of second harmonic generated Nd:YAG laser light.Godkänd; 2005; 20061213 (haneit)
3
Bergström, David. "The absorptance of metallic alloys to Nd:YAG and Nd:YLF laser light /." Luleå : Luleå University of Technology, 2005. http://epubl.ltu.se/1402-1757/2005/89/.
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Quetschke, Volker Marcel. "Korrelationen von Rauschquellen bei Nd:YAG-Lasersystemen." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969654669.
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Udaiyan, Darren. "Novel self-adaptive Nd:YAG laser resonators." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300857.
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Wu, Fushun. "Nd:YAG and excimer lasers application aspects." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395661.
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Forsman, Tomas. "Nd:YAG laser welding of aluminium alloys." Licentiate thesis, Luleå tekniska universitet, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25956.
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Archilla, Jose Ricardo de Freitas. "Ação do laser de Nd:YAG intracanal sobre endotoxinas na dentina radicular." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-02012008-113553/.
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As endotoxinas são responsáveis por importantes reações sistêmicas e locais, podendo comprometer o sucesso do tratamento endodôntico. O hidróxido de cálcio, mesmo com limitações, mostra-se como opção única efetiva entre as soluções irrigadoras e as medicações intracanal na redução das endotoxinas nos túbulos dentinários. O experimento realizado avaliou a eficiência do laser de Nd:YAG frente à uma endotoxina inoculada no canal radicular pela utilização de duas cinemáticas de irradiação. Após um período de incubação, confirmada a passagem da endotoxina inoculada no canal radicular através da dentina e do cemento radicular, a irradiação foi realizada ou com cinemática oscilatória ou com cinemática helicoidal, para posterior leitura e comparação com os grupos controle. Os parâmetros utilizados na irradiação com o laser de Nd:YAG de comprimento de onda de 1064 nm foram: 100mJ, 15 Hz, 1,5 W, diâmetro do núcleo da fibra 320 ?m, fluência do pulso 124 J/cm2, largura do pulso 120 ?s e intervalo de relaxação térmica 30 s. Os dados foram comparados pelo método ANOVA, complementado pelo teste de Tukey. As concentrações de endotoxina nos espécimes dos grupos irradiados (helicoidal e oscilatório) foram similares. Além disso, elas também foram similares às dos espécimes controle negativo e significantemente menores (p=0,0271) que as do controle positivo, que não sofreram irradiação. A irradiação com laser de Nd: YAG, nas condições deste experimento é efetiva na inativação da endotoxina da dentina radicular.The endotoxins are responsible for important systemic and local reactions that could compromise the endodontic success. The calcium hydroxide even with limitations is the only effective option among the irrigant solutions and intracanal medications on the endotoxin reduction in the dentinal tubules. This experiment evaluated the Nd:YAG laser efficacy regarding the inoculated endotoxin in the root canal with two cinematic irradiation procedures. The irradiation was accomplished using an oscillatory and helicoidal technique after an incubation period where the passage of the inoculated endotoxin inside the root canal through dentin and cement was confirmed. Following this the analysis and comparison among the groups was performed. The Nd:YAG laser (?=1064 nm) irradiation, used parameters were: 100mJ, 15 Hz, 1,5 W, core fiber diameter of 320 ?m, pulse fluency of 124 J/cm2, pulse width of 120 ?s and relaxation time interval of 30 s. The data were statistically compared by ANOVA complemented by the Tukey\'s test (p<=0,005). The endotoxin concentration at the irradiated samples, regardless the techniques applied were similar. Moreover these concentrations were also similar to those of negative controls and significantly smaller than those of positive controls that were not irratiated (p=0,0271). The Nd:YAG laser irradiation under this experiment conditions was effective on the root canal endotoxin inactivation.
9
Montgomery, D. J. "The physics of pulsed Nd:YAG laser welding." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638225.
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Lasers have been in use to weld materials together for over 30 years, beginning with the ruby lasers. With the recent introduction of compact high average power Nd:YAG lasers with fibre optic delivery, the applications of lasers in welding has considerably increased and is continuing to do so at an expanding rate. A particular example is in the use of fibre optically delivered Nd:YAG laser beams in applications where the flexibility and ease of control of the light beam can be very useful in confined or hazardous areas, for example, inside a nuclear reactor. This thesis has three purposes; firstly, to determine methods through which characterisation of the weld process can be achieved. Two active and three passive systems were designed and built. Of the active systems, it was found that the paramagnetic system was too complicated for accurate use. The laser deflection system required a comparison experiment for interpretation of the weld results, achieved using simulated water "weldpools". The technique gives good information regarding the quality and penetration state of the weld. Of the passive systems, a dual wavelength monitor system and an acoustical monitoring system were built also giving good results regarding weld conditions. Spectroscopic measurements show that plasma conditions in the weld can be neglected to 1 part in 108. The second purpose is to use the results from these characterisation techniques to serve as data for a theoretical description of the welding phenomenon and the lack of a plasma serves to make a simple, practical theory possible. Finally, to identify possible systems that can be of use for on-line monitoring and control of a practical laser system for remote welding.
10
Kudesia, Sean Swarup. "Precision Nd:YAG laser drilling of aerospace materials." Thesis, Heriot-Watt University, 2003. http://hdl.handle.net/10399/387.
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Lámfalusi, Tamás [Verfasser]. "Bohrstrategien mit dem Nd:YAG Festkörperlaser / Tamas Lamfalusi." Aachen : Shaker, 2007. http://d-nb.info/1166510948/34.
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Beedell, James. "Nd:YAG based laser sources for targeting applications." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2742.
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The aim of the research is to improve laser system products manufactured at Selex ES which are used primarily for airborne targeting applications. This is achieved by developments to the design that prevent failures during manufacture or improve beam parameters such as divergence. A Q-switched diode-side-pumped Nd:YAG zig-zag geometry slab laser within a cross Porro prism resonator is investigated. This perturbation insensitive resonator design is used in laser systems operating over the full military environment of vibration and temperature. A number of aspects of the design are computer modelled with experimental verification, such as the effects of thermal lensing in the Nd:YAG slab, and the polarisation states in the resonator. These were used to analyse a number of issues encountered during manufacture, such as the lack of control over the polarisation state for output coupling, pre-lase causing damage to optical elements, and thermal lensing producing variations in beam quality. A number of design changes were made and, after experiments to verify improved performance, they were successfully integrated into a number of laser production programmes. The beam quality of laser systems was found to be affected by thermal lensing. A number of novel solutions were tested experimentally, which affected the thermal lens. Results of the alteration of the pump distribution in the Nd:YAG slab and the profile of conduction cooling are presented. 885 nm pumping instead of the traditional 808 nm pumping produced a reduction of the thermal lens by a factor of two from -0.1 D to -0.05 D, producing an improvement in the laser beam quality from M2 6.5 to 3.5. An enhancement in brightness of 2.2 was demonstrated using a laser resonator incorporating a deformable bimorph mirror. A new concept for a targeting laser source, which incorporated an eye-safe wavelength, was demonstrated using a common resonator intracavity OPO design. A conversion efficiency of 40% was achieved for 36 mJ output of 1573 nm eye-safe light from a 90 mJ laser at 1064 nm. The relative pointing directions of the two wavelength beams was measured to be within 250 μRad angular separation, which will be unaffected by ambient temperature variation. This level of performance is challenging to achieve in the current laser system design incorporating an extracavity OPO.
13
Lizarelli, Rosane de Fátima Zanirato. "Lasers de Nd:YAG nos regimes de nano e de picossegundos em esmalte e em dentina-análises morfológica e química." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-09042008-152816/.
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Vários experimentos têm demonstrado que pulsos ultra curtos no domínio de subpicossegundos promovem uma combinação de efeitos termomecânicos que superam algumas das objeções ao uso de um laser como instrumento removedor. Usando os parâmetros apropriados de operação, lasers com pulsos ultra curtos podem se comportar melhor do que instrumentos convencionais, incluindo alguns dos lasers pulsados comercialmente já disponíveis na Odontologia. A exploração e otimização nos parâmetros dos lasers disponíveis podem promover a remoção de certas objeções ao amplo uso dos lasers. O uso de lasers de pulsos ultra-curtos para ablação de dentes previne o superaquecimento e é uma alternativa para a remoção mecânica de material; além de minimizar o volume desse material removido. Através de estudos morfológicos e químicos, são apresentadas as características de interação laser pulsado - tecido duro dental, com relação a sua largura de pulso - nano ou picossegundos. O objetivo principal é dar início a um novo sistema para ablação de esmalte e dentina humanos: o laser de Nd:YAG no regime de picossegundos. A eficiência da ablação com laser através de um regime de picossegundos minimiza a destruição do material adjacente devido a formação de plasma e ataque. Isso previne a geração excessiva de ondas de choque e promove uma considerável diminuição nos efeitos mecânicos. A diminuição das ondas de choque provavelmente também poderá reduzir a vibração e conseqüentemente a sensação de dor, se aplicado clinicamente. Apesar da baixa taxa de ablação, os resultados mostram a real possibilidade para usar um sistema laser comercial relativamente simples para pulsos em picossegundos que poderia promover a Dentística Operatória Puntual e Seletiva, em outras palavras, seria possível tratar apenas o tecido alterado com seletividade e sem remover tecido sadio ou mesmo promover danos aos tecidos ao redor. Na maioria dos experimentos aqui apresentados, o laser de pulso ultra-curtos apresentou aumento na proporção Ca/P, melhorando a resistência química da superfície irradiada. Além disso, os cortes precisos resultam em superfícies mais lisas, que é importante para prevenir a colonização do biofilme. Outros estudos in vitro são necessários, mudando os parâmetros de energia e simulando situações clínicas para propor o uso efetivo desse sistema in vivo, mas, de fato, o sistema laser em picossegundos pode melhorar a qualidade da Dentística Operatória num futuro breve.In several already demonstrated experiments, ultrashort laser pulses on the subpicosecond range have been shown to produce a strong thermo-mechanical effect, in several different situations. Even been out side dentistry, the general aspects of subpicosecond pulses interaction with matter are of broad applications on can be used as general references. This strong thermo-mechanical effect has created objections toward the use of such lasers as a material removal too1. On the other hand, using the appropriated parameters of operation, ultra short laser pulses of subnanosecond duration could present better performance than conventional lasers operating at nanosecond regime in several aspects. Through chemical and morphological studies, they are presented the main features from interaction between pulsed laser and dental hard tissue, considering pulse width - nano or picosecond pulse. The main objective is starting to use a new system to ablate human enamel and dentin: Nd:YAG picosecond laser system. Efficient laser ablation in the picosecond regime minimizes destruction of adjacent material due to a plasma formation and etching. This avoids an excessive generation of shock waves and promotes a considerable decrease in mechanical effects. The decreasing of shock waves also reduces vibration and consequently the sensation of pain, if clinically used. Despite the small ablation rate, our results show the real possibility to use a relative simple commercial laser system for picosecond pulses to be use effectively in Dentistry. The real clinical use of a picosecond laser system could promote the Punctual and Selective Operative Dentistry, in other words, we could treat just the decayed tissue with selectivity without remove sound tissue or even promote damage to tissues around. Besides, the precise cuts maybe give us a smoother surface, which is important to prevent biofilm colonization. We need to evaluate more in vitro studies, changing parameters and simulating clinical situations to propose the effective use of this system in vivo, but in fact, we believe that the picosecond laser system can improve the quality of Operative Dentistry in a brief future.
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Lange, Falk. "Stabilisierung der Ausgangsleistung eines resonatorintern frequenzverdoppelten Nd:YAG-Lasers." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967557119.
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Salehi, Dariush, and ds_salehi@yahoo com. "Sensing and control of Nd:YAG laser cladding process." Swinburne University of Technology, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20050915.142812.
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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.
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Kearns, Aileen. "The effect of wavelength in Nd:YAG laser cleaning." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399131.
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Maeda, Fernando Akio. "Uso dos lasers de Er:YAG e Nd:YAG no controle da progressão de lesões erosivas em dentina radicular." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/58/58133/tde-26032010-162029/.
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Quando os túbulos dentinários ficam expostos ao meio bucal, sendo a erosão o principal fator etiológico, estímulos aplicados na dentina provocam movimentação rápida do fluido desencadeando a hipersensibilidade dentinária. O objetivo desse estudo foi avaliar, através modelo crossover 2x2 in situ, se o efeito da irradiação a laser seria capaz de controlar a permeabilidade da dentina radicular erodida submetida a subseqüentes desafios erosivos. Fragmentos de dentina (3x3 mm) foram ciclado por desafio erosivo (ácido cítrico 0.3%, 2h) para induzir lesões erosivas, seguido por um período de remineralização em saliva artificial (24 h). Os espécimes foram irradiados com laser de Nd:YAG (1W/15Hz) ou Er:YAG (100mJ/3Hz) ou não irradiado. Doze voluntários participaram utilizando dispositivos intra-oral, em duas fases de 5 dias cada. No primeiro período, metade dos voluntários expôs os espécimes a episódios erosivos, enquanto a outra metade não expôs a nenhum tipo de desafio. Seguido de um período de 2 dias de washout, os voluntários submeteram os espécimes ao procedimento alternado. No final de cada fase, os espécimes foram removidos e preparados para avaliação da permeabilidade. Após a coloração com soluções de sulfato de cobre e ácido rubêanico, os espécimes foram seccionados e digitalizados sob microscopia óptica A permeabilidade relativa foi quantificada através da relação entre a profundidade de penetração de íons cobre e a espessura da dentina. ANOVA e o teste de Tukey demonstraram que o grupo não irradiado exposto a desafios subseqüentes produziu os maiores valores de permeabilidade (Er:YAG: 4,2%a; Nd:YAG: 4,6%a; Ct: 14,6%b). Os resultados obtidos mostraram que os lasers podem controlar a progressão da erosão na dentina radicular.When the dentinal tubules are exposed to the oral environment, the erosion the main etiological factor, stimuli applied to the dentin causing rapid movement of the fluid causing the hypersensitive dentin. The aim of this investigation was to evaluate, through a crossover 2x2 in situ trial, whether the effect of laser irradiation would be capable to control the permeability of eroded root dentin subjected to further acid challenges. Dentin slabs (3x3 mm) were cycled through erosive challenges (0.3% citric acid 2h) to induce erosion-like lesions, followed by a remineralizing period in artificial saliva (24 h). Specimens were laser-irradiated with Nd:YAG (1W/15Hz) or Er:YAG (100mJ/3Hz) or nonirradiated. Twelve volunteers participated using intraoral devices, in two phases of 5 days each. In the first period, half of participants exposed the specimens to erosive episode, while the other half did not perform any erosive challenge. Followed a 2-day washout period, volunteers submitted the slabs to the alternative procedure. In the end of each phase, specimens were prepared for permeability evaluation. After staining with solutions of copper sulfate and rubianic acid, the specimens were sectioned and scanned under light microscopy. Relative permeability was quantified by the relationship between the depth of penetration of copper ions and the thickness of dentin. ANOVA and Tukey´s test demonstrated that the nonirradiated group exposed to further erosion episodes produced the highest permeability (Er:YAG: 4,2%a; Nd:YAG: 4,6%a; Ct: 14,6%b). The obtained results showed that lasers can control the erosion progression in root dentin.
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Eryilmaz, Ertan. "Design And Construction Of A Cw Mode Nd:yag Laser Prototype." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605521/index.pdf.
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In this thesis a theoretical background of Nd:YAG lasers has been
presented and key parameters of a design have been stated. Both
pulsed mode and CW mode designs have been madea 500mJ xenon flash lamp has been investigated as the pulsed light source and a 500W tungsten halogen lamp has been used as the continuous light source for optical pumping. Closed cooling system has been constructed. De-ionized water has been used as coolant. The goal has been acomplished by constructing a CW mode prototype. The output power has been calculated. Dependence of output power to the reflectivity of output coupler is simulated and optimum reflectivity is calculated. Theoretical emission bands of Nd:YAG have been observed experimentally.
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Adamonis, Jonas. "High power Nd:YAG laser for pumping of OPCPA systems." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093516-33211.
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This thesis was aimed to develop, investigate and optimize high power Nd:YAG laser system for OPCPA (Optical Parametric Chirped Pulse Amplifiers) pump. The particular attention is paid for the temporal characteristics of the Nd:YAG amplifies output pulse. Employment of Fabry-Perоt etalons in the cavities of two-stage Nd:YAG regenerative amplifier enables for amplified pulse stretching from 60 fs to ~ 100 ps pulse widths. The modulation of amplified pulse envelope is minimal when ration of thickness of the etalons is around 2. Envelope modulation can be controlled by changing the reflectivity of etalons. In order to improve amplified pulse contrast, we for the first time to our knowledge implemented second order intensity dependent filter, based on the effect of fundamental pulse polarization rotation in unbalanced second harmonic generators. By using this method, the contrast of the output pulses was improved by >102 times. We also demonstrated that Gaussian pulses from the output of Nd: YAG amplifiers can be transformed into flat–top pulses by using cascade second harmonic generation processes. The developed high output energy Nd:YAG amplifiers system for OPCPA pumping is optically synchronized with pulses of Yb:KGW oscillator and features two 532 nm outputs with pulse parameters: a) Gaussian pulse profile, ~ 300 mJ energy, 75 ps pulsewidth; b) hiper- Gaussian pulse profile, ~100 mJ energy, pulse width 100-150 ps.Disertacija yra skirta sukurti, ištirti ir optimizuoti didelės galios Nd: YAG lazerių sistemą efektyviam moduliuotos fazės signalų optinių parametrinių stiprintuvų kaupinimui. Ypatingas dėmesys yra skiriamas Nd:YAG stiprintuvų išvadinių impulsų laikinių parametrų formavimui. Pademonstravome, kad Fabry-Pero interferometrų panaudojimas Nd:YAG dvipakopio regeneracinio stiprintuvo rezonatoriuose leidžia stiprinamų impulsų trukmę padidinti nuo ~ 60 fs iki 100 ps. Tuo tarpu išvadinių impulsų laikinės plėtros mastas bei gaubtinės moduliacijos gylis gali būti valdomas keičiant etalonų atspindžio koeficientą, o jų gaubtinės moduliacijos vertė mažiausia, kai etalonų storio santykis artimas 2. Sustiprintų impulsų kontrasto gerinimui pirmą kartą pritaikėme netiesinį antros eilės filtrą, veikiantį fundamentinės spinduliuotės poliarizacijos sukimo, išderintame antros harmonikos generatoriuje, efekto pagrindu. Tokiu būdu Nd:YAG stiprintuvuose sustiprintų impulsų kontrasto vertė pagerinta apie 102 kartų. Taip pat pademonstruota, kad Nd: YAG stiprinimo sistemos išėjime naudojant pakopinius antros harmonikos generacijos procesus, Gauso formos impulsus galima transformuoti į hipergauso impulsus. Sukurta didelės išvadinės energijos pikosekundinė Nd:YAG stiprintuvų sistema yra optiškai sinchronizuota su užduodančio femtosekundinio Yb:KGW osciliatoriaus impulsais ir turi ~ 300 mJ , 75 ps trukmės Gauso impulsų bei 100 mJ, > 100 ps trukmės hipergauso laikinės formos impulsų išvadus.
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Andrade, Gabriel Giampietro de. "Soldagem a laser Nd:YAG pulsado no aço superaustenítico AISI 904L." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153509.
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A soldagem é um processo de fabricação utilizado em geral para união de peças e quando utiliza o laser como fonte de calor, denomina-se soldagem a laser. Um tipo bem conhecido é a soldagem a laser Nd:YAG pulsado, utilizado em diferentes tipos de materiais. Um dos materiais mais utilizados na engenharia é o aço inoxidável que possui alta resistência à corrosão, como por exemplo o aço AISI 904L, muito utilizado em tanques de armazenamento de ácido sulfúrico e fosfórico além de ampla aplicação na indústria petroquímica. Conduziu-se uma soldagem à laser Nd: YAG pulsado em chapas de aço inoxidável AISI 904L com espessura de 3 mm, variando-se quatro fatores tais como Potência de pico (PP) , Largura temporal (w), Frequência (F) e Velocidade de soldagem (S), todos eles distribuidos em três níveis de variação. Foi feito um Planejamento Experimental através do Método Taguchi, utilizando-se uma matriz ortogonal L9 e portanto realizando-se 9 experimentos em condições diferentes. A soldagem foi executada em atmosfera protetora com gás Argônio com fluxo de gás de 15 l/min, com deslocamento automatizado. A energia de cada pulso variou de 30 a 38,4J e a energia de soldagem entre 1,5 e 3,2 kJ/mm; as taxas de sobreposição variaram de 60 a 83%. As amostras foram preparadas para metalografia e atacadas com Ácido Oxálico 10% eletrolítico, com 6V e 7 segundos. Apesar da maioria das amostras romperem na Zona Fundida (ZF), a resistência mecânica ficou muito próxima do valor encontrado para o Metal Base (MB). Para o MB, ZT e ZF, os valores médios de microdureza obtidos foram 215, 242 e 238 HV respectivamente, indicando uma soldagem praticamente homogênea, em que a zona fundida apresentou em sua microestrutura apenas fase austenitica assim como o metal base, sendo possível observar alguns defeitos característicos de solidificação como bolhas e trincas. Foi feita uma análise pelo Método Taguchi utilizando os valores médio de resposta e razão sinal-ruído em gráficos complementada por ANOVA com teste de Fisher em que as respostas principais foram limite de escoamento, limite de resistência a tração, limite de ruptura e dureza, indicando os parâmetros ótimos para cada caso.
Welding is a manufacturing process used for joing parts and when a laser is utilized as a heat source, its called Laser Welding. A very known type is the pulsed Nd: YAG Laser Welding, that is used in many different kinds of materials. One of the most applied materials in engineering is the stainless steel that is highly corrosion resistant, for example the AISI 904L that is frequent used in sulfuric and phosphoric acid storage tanks, besides the petrochemical industry. Was carried out a pulsed Nd:YAG laser welding in AISI 904L stainless steel sheets with 3 mm of thickness, varying four factors such as Peak Power (PP), Time width (w), Frequency (F) and Welding Velocity (v), all of them distributed in three levels. A Design of Experiment was made through the Taguchi Method, using a L9 ortogonal array and therefore conducting nine experiments in different conditions. The welding was performed in argon gas flow of 15l/min, with automatic displacement. Pulse energy varied since 30 to 38,4J and welding energy from 1,5 to 3,2 kJ/mm; the overlay rates varied between 60 and 83%. Samples were prepared for metallography and etched with Oxalic Acid 10%, eletrolitic in 6v and 7 seconds. Although most of the samples broke in the Weld Zone (WZ), the mechanical resistance stayed very closer to the values found in Base Metal (BM). For BM, TZ and WZ, the mean values of hardness was 215, 242 and 238 HV respectively, pointing a homogeneous welding wherein the WZ presented only austenitic phase as well as the BM, being possible to observe some solidification characteristics defects as bubbles and cracks. An analysis was performed by the Taguchi Method ploting the main responses and the signal-noise ratio with the parameters, supported by an ANOVA with Fisher’s test in wich the main responses was the yield strength, tensile strength, fracture strength and hardness, indicating optimal parameters for each case.
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Adamonis, Jonas. "Didelės galios pikosekundinis Nd:YAG lazeris čirpuotų impulsų parametrinių stiprintuvų kaupinimui." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093301-70429.
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Disertacija yra skirta sukurti, ištirti ir optimizuoti didelės galios Nd: YAG lazerių sistemą efektyviam moduliuotos fazės signalų optinių parametrinių stiprintuvų kaupinimui. Ypatingas dėmesys yra skiriamas Nd:YAG stiprintuvų išvadinių impulsų laikinių parametrų formavimui. Pademonstravome, kad Fabry-Pero interferometrų panaudojimas Nd:YAG dvipakopio regeneracinio stiprintuvo rezonatoriuose leidžia stiprinamų impulsų trukmę padidinti nuo ~ 60 fs iki 100 ps. Tuo tarpu išvadinių impulsų laikinės plėtros mastas bei gaubtinės moduliacijos gylis gali būti valdomas keičiant etalonų atspindžio koeficientą, o jų gaubtinės moduliacijos vertė mažiausia, kai etalonų storio santykis artimas 2. Sustiprintų impulsų kontrasto gerinimui pirmą kartą pritaikėme netiesinį antros eilės filtrą, veikiantį fundamentinės spinduliuotės poliarizacijos sukimo, išderintame antros harmonikos generatoriuje, efekto pagrindu. Tokiu būdu Nd:YAG stiprintuvuose sustiprintų impulsų kontrasto vertė pagerinta apie 102 kartų. Taip pat pademonstruota, kad Nd: YAG stiprinimo sistemos išėjime naudojant pakopinius antros harmonikos generacijos procesus, Gauso formos impulsus galima transformuoti į hipergauso impulsus. Sukurta didelės išvadinės energijos pikosekundinė Nd:YAG stiprintuvų sistema yra optiškai sinchronizuota su užduodančio femtosekundinio Yb:KGW osciliatoriaus impulsais ir turi ~ 300 mJ , 75 ps trukmės Gauso impulsų bei 100 mJ, > 100 ps trukmės hipergauso laikinės formos impulsų išvadus.This thesis was aimed to develop, investigate and optimize high power Nd:YAG laser system for OPCPA (Optical Parametric Chirped Pulse Amplifiers) pump. The particular attention is paid for the temporal characteristics of the Nd:YAG amplifies output pulse. Employment of Fabry-Perоt etalons in the cavities of two-stage Nd:YAG regenerative amplifier enables for amplified pulse stretching from 60 fs to ~ 100 ps pulse widths. The modulation of amplified pulse envelope is minimal when ration of thickness of the etalons is around 2. Envelope modulation can be controlled by changing the reflectivity of etalons. In order to improve amplified pulse contrast, we for the first time to our knowledge implemented second order intensity dependent filter, based on the effect of fundamental pulse polarization rotation in unbalanced second harmonic generators. By using this method, the contrast of the output pulses was improved by >102 times. We also demonstrated that Gaussian pulses from the output of Nd: YAG amplifiers can be transformed into flat–top pulses by using cascade second harmonic generation processes. The developed high output energy Nd:YAG amplifiers system for OPCPA pumping is optically synchronized with pulses of Yb:KGW oscillator and features two 532 nm outputs with pulse parameters: a) Gaussian pulse profile, ~ 300 mJ energy, 75 ps pulsewidth; b) hiper- Gaussian pulse profile, ~100 mJ energy, pulse width 100-150 ps.
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Knoke, Stefan. "Einfrequenzbetrieb von diodengepumpten Nd:YAG-Hochleistungslasern in Stab- und Slabgeometrie." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=956329845.
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Klug, Manuel. "Frequenzstabile kontinuierliche Jodramanlaser gepumpt mit einem frequenzverdoppelten Nd:YAG-Laser." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969336675.
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Mondin, Linda. "Stabilisation de fréquence de laser Nd:YAG pour applications spatiales." Phd thesis, Université de Nice Sophia-Antipolis, 2005. http://tel.archives-ouvertes.fr/tel-00148136.
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Les lasers stabilisés à long terme sont utilisés dans de nombreux domaines en métrologie, leur incursion dans les applications spatiales se précise depuis quelques années, missions de physique fondamentale, géodésie... Ce travail concerne les lasers stables pour le projet LISA (détection spatiale des ondes de gravitation, mission prévue dans 10 ans); en vue de cette application spatiale, les montages doivent satisfaire plusieurs critères: compacité, stabilité mécanique, robustesse et fiabilité. Les références utilisables pour l'asservissement long terme (iode, chapitre 3) et court terme (cavité de Fabry-Pérot, chapitre 4) sont décrites, ainsi que leurs limitations principales. L'analyse et le choix de ces références de stabilisation seront couplés avec le choix des techniques de stabilisation (PDH, Tilt-Locking, Modulation Transfer). Dans les techniques de stabilisation, celle de Pound-Drever-Hall (PDH), un classique en matière de configuration, est comparée au Tilt-Locking, une technique continu et peu consommatrice en énergie, dans le cas d'une référence Fabry-Perot monolithique. Les calcules théorique pour chaque technique et chaque type de référence ammeneront à une description des sources de bruit et à une simulation des signaux d'erreur attendus. Les performances théoriques sur le long terme et les efficacités quantiques sont intercomparées. La deuxième partie, présentera les montages expérimentaux et les résultats obtenus, pour des lasers stabilisés sur Fabry-Perot et sur l'Iode moléculaire. Pour calibrer les dérives de fréquence du Fabry-Perot, sa fréquence de résonance sera mesurée par rapport à celle de la molécule, ce qui permettra de présenter des solutions obtenues analytiquement et numériquement pour l'asservissement en longueur de cette référence mécanique. En appendices, les détails de dimensionnement des bruits de LISA conduisant aux spécifications des lasers, le rappel théorique des ondes de gravitation ainsi que divers simulations de calculs effectués.
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Hill, Timothy J. "Interference of intensity noise in a multimode Nd:YAG laser." Title page, abstract and contents only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phh6484.pdf.
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Includes bibliographical references (leaves 151-163). Investigates the behaviour of the intensity noise in a multimode Nd:YAG laser. The collective modes of oscillation are excited by broadband ambient noise. Because the phase of the excitation is unknown, a cross spectral technique to measure the antiphase dynamics directly and form a picture of the intensity noise interference for two to five mode operation is developed. For three mode operation, the contributions of the longitudinal modes to collective modes is measured.
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Willach, Jens. "Herstellung von konturierten Bohrungen in Mehrschichtsystemen mit Nd:YAG-Laserstrahlung /." Aachen : Shaker, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014833932&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Klinger, Peter [Verfasser]. "Regelung des Nd:YAG-Formabtrags mit optischen Sensoren / Peter Klinger." Aachen : Shaker, 2004. http://d-nb.info/1172612226/34.
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Torre, Fernando Antonio Camargo. "Construção e caracterização de um laser continuo de Nd:YAG." [s.n.], 1991. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277333.
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Orientador: Antonio G. J. Baldin VillaverdeDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Foi construída uma fonte trifásica com potência elétrica máxima de 6KW e um fator de ruído menor que 0,5% extremamente estável, a qual foi utilizada para controlar uma lâmpada de Kriptônio da EG&G, a FK-111C-3 capaz de suportar corrente elétrica máxima de 50A em 115V. Bombeamos então um bastão de Nd:YAG de 3" de comprimento por 1/4" de diâmetro, o qual foi colocado inicialmente em um cavidade comercial da ILC e depois em uma cavidade por nós desenvolvida. Para caracterizarmos estas duas cavidades foram utilizados espelhos circulares de 1" de diâmetro com 100%, 90% e 80% de reflectividade, bem como "pin-holes" intracavidade para garantirmos saída monomodo (TEM00)
Abstarct: Not informed.
Mestrado
Física
Mestre em Física
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Greses-Juan, Jose. "Plasma/plume effects in CO₂ and Nd:YAG laser welding." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/284019.
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Bronski, Mark T. "Development of a process for characterization of Nd:YAG crystals." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0409103-104942.
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Reinefeld, Vanessa. "Rhinoresistometrische und akustisch-rhinometrische Untersuchungen zur Effektivität der Nd:YAG-Lasermuschelkaustik." [S.l.] : [s.n.], 2003. http://www.diss.fu-berlin.de/2003/69/index.html.
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Zawischa, Ivo. "Injektionsgekoppelte diodengepumpte Nd:YAG- und Nd:YVO4-Laser für terrestrische interferometrische Gravitationswellendetektoren." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970650302.
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Brodie, Lyn. "Welding of skin using Nd:YAG laser with bipolar contact applicators." University of Southern Queensland, Faculty of Engineering and Surveying, 2003. http://eprints.usq.edu.au/archive/00001412/.
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[Abstract]: This thesis investigates the feasibility of closing wounds in skin tissue by laser welding as a substitute for suturing. Such a process would provide advantages in some surgical procedures. The investigation revised available theory on the action of lasers on skin tissue as a basis for the experimental program. The results of experiments using rat skin are then reported. In addition a thorough investigation of the normal (uninjured) tensile strength of rat skin was undertaken to provide a base line comparison. Laser systems permit very high-energy radiation of a single wavelength to be focused on a tiny spot, and have found application in many areas of engineering. They are also currently used in many branches of medicine including ophthalmology, gynaecology, dermatology, otolaryngology, and gastroenterology. These medical applications employ argon, YAG, and carbon dioxide type lasers. In many cases, lasers have been found to be more effective than conventional treatment methods with advantages including reduced blood loss, more accurate removal of unwanted tissue, shorter operating times and less postoperative pain and care (Gibson and Kernohan, 1993). Tissue welding using laser energy represents a small but growing area of medical research and is largely focused on anastomosis. This thesis investigates, using a specific experimental program, the feasibility of the bipolar contact Nd:YAG laser to weld cutaneous tissue. No similar published research has been identified in this area. The available literature focuses on non-contact lasers of various types and settings and mainly in the area of anastomosis. The experimental methodology and the specific technique for the bipolar contact laser is developed, tested and evaluated as part of this project. The welding techniques developed in this project overcome the previous difficulties of tissue alignment. The use of the bipolar laser probes substantially improves the ability to align the tissue edges to be joined. The probes give tactile feedback to the user and the pressure effect of the probes may assist with the welding process. The developed technique was no faster or easier than suturing. Viable welds and a useable technique for welding skin on rats were developed and tested. The resultant healing was comparable with published literature and both sutured and welded wounds returned to full strength as compared with the baseline data collected. All wounds had returned to full strength within 91 days. At 75 days there was not significant difference between laser welded and sutured wounds and they had achieved approximately 90 percent of full strength. Time to half strength was approximately 42 days and there was a larger standard deviation for both laser welded and sutured wounds. The most significant increase in strength and therefore healing occurred in the first 42 days. Simhon et al, 2001 states that a tensile strength of 0.6 N plus/minus 0.4 N was sufficient to hold tissue together. By day 7 the strength of the wound (laser welded) was more than twice the strength needed to maintain closure. There may have been sufficient healing for this to occur earlier but there were insufficient animals to allow for testing of this theory. In conclusion this experimental program and investigation has reviewed the available literature on the current use of lasers in medicine and their specific laser-tissue interaction which leads to tissue welding. It has provided a large database of tensile strength measurements collected with a reproducible methodology and reported in a standardised format. The developed technique for laser tissue welding using a bipolar contact Nd:YAG laser has been established and verified. It produces viable welds comparable in strength and healing rates to sutures.
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Klages, Kilian. "Laserstrahl-Mikroschweissen ungleicher Metalle durch Nahtschweissen mit gepulsten Nd:YAG-Lasern /." Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016030450&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Helten, Stephan [Verfasser]. "Qualifizierung des Nd:YAG-MIG-Hybridschweissverfahrens für den Aluminiumkarosseriebau / Stephan Helten." Aachen : Shaker, 2003. http://d-nb.info/1170543588/34.
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Dobson, Helen Louise. "The interaction of pulsed Nd:YAG laser irradiation with human enamel." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/4312/.
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The aim of the work presented in this thesis was to investigate the interaction of pulsed Nd:YAG laser irradiation with both sound and artificially carious human enamel. More specifically, the aims were to characterise the effect of Nd:YAG laser irradiation on artificially created white spot enamel lesions (to simulate the effect of lasing carious enamel); to quantify the effects of pulsed Nd:YAG laser irradiation on enamel demineralisation; to investigate whether there is synergy between the action of pulsed Nd:YAG laser irradiation and fluoride in terms of impairing acid resistance to enamel; and finally to clarify the mechanism by which pulsed Nd:YAG laser irradiation physically interacts with enamel to induce acid resistance. Laser irradiation of artificial white spot lesions, at 50 mJ and 100 mJ (10 pps, 2 or 5 sec), was found to ablate tissue, causing crater formation. Ablation depth, as determined by microdensitometry, was correlated only with the power used, being greater at 100 mJ than at 50 mJ. SEM examination of the surface morphology of lased enamel, and the surrounding unlased area, was consistent with a process of melting and recrystallisation. It is evident, from this investigation, that in order to remove carious enamel selectively, while leaving sound enamel intact, successive applications of low power irradiation (50 mJ) are the most suitable. The work presented in this thesis has indicated the versatility of the Nd:YAG laser as a dental instrument. The laser can be used to ablate carious enamel and has potential as a prophylactic treatment for caries. The most significant aspect of the laser as a strategy to prevent caries, is that it seems to physically alter the structure of enamel so may, therefore, be a method of permanently increasing tooth resistance to decay.
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Peters, Christopher N. D. "In process monitoring and control for Nd:YAG laser material processing." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399233.
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BERRETTA, JOSE R. "Solda laser em materiais dissimilares com laser de Nd:YAG pulsado." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11293.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Beacco, Claire. "Volatilisation tissulaire au laser nd:yag continu : etude experimentale et modelisation." Lille 2, 1995. http://www.theses.fr/1995LIL2P255.
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Ayyalasomayajula, Narasimha Rao. "Nd:YAG mini slab laser hybrid integration and Raman sensor application /." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10437.
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Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xiv, 170 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 159-164).
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Azevedo, Danielle Torres. "Avaliação in vitro da resistência ácida e da permeabilidade do esmalte dental decíduo irradiado com laser Nd:Yag associado ou não ao flúor." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/58/58135/tde-09062011-085649/.
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A eficiência dos lasers associado ou não a fluoretos no aumento da resistência ácida e na redução da solubilidade do esmalte dentário tem sido confirmada em diversos estudos. Diversos comprimentos de onda têm sido utilizados com esta finalidade, apresentando bons resultados e representando uma abordagem preventiva simples e não invasiva. Apesar do emprego do laser Nd:YAG ter sua ação preventiva bem conhecida, são escassos os estudos em dentes decíduos, principalmente estudos que estabeleçam parâmetros seguros e eficientes, seja associado ao flúor ou isoladamente. Desta forma, o objetivo do presente estudo foi avaliar a resistência ácida e a permeabilidade do esmalte decíduo. Para tanto, foram selecionados 69 molares decíduos humanos, resultando em 132 corpos-de-prova. As variáveis de resposta quantitativa foram a microdureza longitudinal, profundidade da desmineralização e permeabilidade do esmalte, e as variáveis de resposta qualitativa foram morfologia da superfície, presença de íons flúor e análise dos componentes químicos do esmalte. Foram utilizados 60 fragmentos vestibular/lingual para a análise de resistência ácida e midrodureza (n=10), e após preparados e tratados, estes espécimes foram submetidos ao ciclo de desremineralização para formação de lesão de cárie artificial. Para análise da permeabilidade (48 fragmentos n=8), para a análise de MEV e EDX (18 fragmentos n=3) e para DRX (6 dentes n=1) foi realizado apenas o tratamento da superfície em 6 níveis: C- Controle: sem tratamento; FA: aplicação de gel flúor fosfato acidulado 1,23%; FAL: aplicação de gel flúor fosfato acidulado + Laser Nd:YAG 0,5W/10Hz no modo contato; VF: aplicação de verniz fluoretado 5%; VFL: aplicação de verniz fluoretado 5% + Laser Nd:YAG; L: aplicação do Laser Nd:YAG. Os dados de microdureza (%VM) foram avaliados pelo teste de Kruskal-Wallis e os dados de profundidade da desmineralização (PD) e Permeabilidade (P) foram avaliados pelos testes ANOVA e Fisher′s LSD (α=5% para todos os testes). Observou-se que os grupos FAL e FA apresentaram a menor variação de dureza em relação aos outros grupos; menor extensão de desmineralização foi observada nos grupos FA, FAL, VF, VFL e L e menor permeabilidade foi verificada nos grupos FA, FAL, VF, VFL e L em relação ao grupo controle (C). Na MEV observouse ausência de fissuras, crateras ou qualquer alteração indesejável na superfície. Na EDX observou-se incorporação de flúor em todos os grupos experimentais (FA, FAL, VF, VFL), exceto no grupo laser (L). Nenhum composto novo foi encontrado na análise de DRX após a associação do flúor com o laser. O laser utilizado isoladamente ou associado ao flúor levou a alterações ultra-estruturais na superfície do esmalte, o que pode ter sido responsável pelo aumento da resistência ácida e redução da permeabilidade, indicando que o laser isoladamente ou associado ao flúor, nas condições desta pesquisa, foi capaz de inibir a desmineralização do esmalte dental decíduo.The efficiency of lasers associated or not with fluorides, in increasing the acid resistance and decrease of enamel solubility of dental enamel has been confirmed by several studies. Several wavelengths have been used for such purpose, providing good results and representing a simple and non-invasive preventive approach. Although the preventive action of Nd:YAG laser is well known, studies on primary teeth are scarce, especially those that establish safe and efficient parameters, when the laser is either associated with fluoride or used alone. Therefore, the aim of this study was to evaluate the acid resistance and permeability of primary tooth enamel. Sixty-nine human primary molars were used, providing 132 specimens. The quantitative response variables were enamel longitudinal microhardness, demineralization depth and permeability, while the qualitative response variables were surface morphology, presence of fluoride ions and analysis of the chemical components of enamel. Sixty buccal/lingual fragments were used for analysis of acid resistance and microhardness (n=10). After being prepared and treated, thee specimens were subjected to a des-remineralization cycle for artificial caries lesion formation. For analysis of permeability (48 fragments, n=8), SEM and EDX (18 fragments, n=3) and DRX (6 teeth, n=1), only surface treatment was performed in 6 levels: C- Control: no treatment; APF: application of 1.23% acidulated phosphate fluoride gel; APFL: application of 1.23% acidulated phosphate fluoride gel + Nd:YAG laser 0.5W/10Hz in mode contact; FV: application of 5% fluoride varnish; FVL: application of 5%fluoride varnish + Nd:YAG laser; L: application of Nd:YAG laser. Microhardness data (%VM) were analyzed by the Kruskal-Wallis test and demineralization depth (DD) and permeability (P) were analyzed by ANOVA and Fisher′s LSD test (α=5% for all tests). APFL and APF presented the lowest microhardness variation of all groups; lower extension of demineralization was observed in groups APF, APFL, FV, FVL and L, and lower permeability was observed in groups APF, APFL, FV, FVL and L compared to group C. The SEM analysis revealed absence of fissures, craters or any other undesirable surface alteration. The EDX analysis revealed fluoride incorporation in all experimental groups (APF, APFL, FV, FVL), except for the group L. No new compound was found in the DRX analysis when fluoride was associated with the laser. Laser alone or associated with fluoride produced ultrastructural alterations on enamel surface, which might have caused the increase of acid resistance and decrease of permeability, thus indicating that, under the conditions of this study, the Nd:YAG laser used alone or associated with fluoride was capable of inhibiting the demineralization of primary tooth enamel.
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Pinto, Regiane de Souza. "Laser de Nd:YAG de alta potência, estabilidade e qualidade de feixe." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-04092014-145713/.
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O trabalho experimental aqui apresentado tem como foco o desenvolvimento de um laser de estado sólido cujo desempenho foi otimizado de tal forma que contemple alta potência, alta qualidade de feixe e estabilidade, levando-se em conta os efeitos térmicos sofridos pelo meio ativo em regime de alta potência de bombeamento. Foram testadas cavidades para operação contínua em multimodo com alta potência de saída e cavidades operando em modo único TEM00. Para cavidades operando no modo fundamental, os ressonadores testados serão divididos em grupos de acordo com o seu comportamento no diagrama de estabilidade. A otimização de tais ressonadores foi realizada apenas alterando-se o raio de curvatura dos espelhos de entrada e saída e suas respectivas distâncias ao plano principal do bastão de Nd:YAG. Como resultado foi alcançada a maior eficiência de extração reportada na literatura para um ou dois módulos de Nd:YAG intracavidade. Os resultados dão uma visão geral sobre possíveis projetos de ressonadores para operação dinamicamente estável, com alta potência de saída e qualidade de feixe. Os dados obtidos servem como base para o desenvolvimento de novos lasers de alta potência e eficiência baseados em módulos DPSSL (Diode-Pumped Solid-State Lasers- Lasers de Estado Sólido Bombeados por Diodo) de baixo custo.The experimental work presented here focuses on the development of a solid-state laser whose performance has been optimized for high power output, high beam quality, and high stability, taking into account the thermal effects experienced by the gain medium under high pumping power. Cavities for continuous wave (CW) operation in multimode with high output power and cavities operating in single mode TEM00 were tested. The resonators will be divided in groups according to their stability diagram. The optimization of such resonators was performed only by changing the curvature radius of the mirrors and their distances to the principal plane of the Nd:YAG rod. As a result was achieved the highest extraction efficiency reported in the literature for one or two intra cavity Nd:YAG modules. The results give an overview of possible designs of resonators for dynamically stable operation with high output power and beam quality. The data serve as basis for the development of new high-power lasers based on low cost DPSSL modules.
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Persson, Joakim. "Kvalitetssäkring av lasersvets i karosseriplåt." Thesis, University West, Department of Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-763.
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Silva, Luciana Ventavele da. "Estudos dos mecanismos envolvidos em processos de endurecimento superficial a laser de ligas a base de alumínio." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-17062011-145032/.
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As ligas de Al-Si são amplamente utilizadas na indústria em substituição ao aço e o ferro fundido nos setores de alta tecnologia. A importância comercial dessas ligas deve-se principalmente ao seu baixo peso, excelente resistência à abrasão e à corrosão, alta resistência em temperaturas elevadas, baixo coeficiente de expansão térmica e menor consumo de combustível que proporciona redução considerável de emissão de poluentes. No presente trabalho, uma liga de Al-Si utilizada na indústria automobilística para fabricação de pistões de motores de combustão interna, foi submetida a tratamentos superficiais de refusão a LASER (Nd:YAG, λ = 1,06 m, modo pulsado). A radiação laser possibilita diversas concentrações de energia com precisa transferência dela para o material sem contato físico. A transferência intensa de energia provoca a ocorrência de modificações estruturais na camada superficial do material. Experimentos com pulsos únicos e trilhas foram realizados sob diferentes condições de processamento LASER com o intuito de analisar as mudanças microestruturais resultantes dos tratamentos e seus efeitos sobre a dureza. Para a caracterização da camada endurecida foram utilizadas as seguintes técnicas: microscopia óptica (MO), microscopia eletrônica de varredura (MEV), espectroscopia por energia dispersiva (EDS), mapeamento de raios-X, ensaios de microdureza Vickers e de rugosidade máxima. Após os tratamentos superficiais de refusão a LASER da liga Al-Si, a alta taxa de resfriamento resultante causou mudança na microestrutura devido ao refinamento das partículas de silício eutético primário presentes na liga, resultando em aumento de dureza.The Al-Si alloys are widely used in industry to replace the steel and gray cast iron in high-tech sectors. The commercial importance of these alloys is mainly due to its low weight, excellent wear (abrasion) and corrosion resistance, high resistance at elevated temperatures, low coefficient of thermal expansion and lesser fuel consumption that provide considerable reduction of emission of pollutants. In this work, Al-Si alloy used in the automotive industry to manufacture pistons of internal combustion engines, was undergone to surface treatments using LASER remelting (Nd:YAG, λ = 1.06 m, pulsed mode). The LASER enables various energy concentrations with accurate transfer to the material without physical contact. The intense energy transfer causes the occurrence of structural changes in the superficial layer of the material. Experiments with single pulses and trails were conducted under various conditions of LASER processing in order to analyze microestrutural changes resulting from treatments and their effects on the hardness. For the characterization of hardened layer was utilized the following techniques: optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray mapping, Vickers microhardness and maximum roughness tests. The high cooling rate caused a change in the alloy structure due to the refinement of the primary eutectic silicon particles, resulting in increase of the mechanical properties (hardness) of the Al-Si alloy.
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Bereczki, Allan. "Desenvolvimento de um laser DPSSL polarizado com mais de 100 W de potência e parâmetro de qualidade próximo de um." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-27062016-142722/.
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A operação dinamicamente estável com zonas conjuntas foi obtida para um ressonador laser contendo dois bastões de Nd:YAG com módulos laser comerciais. O ressonador não polarizado gerou 115 W de potência no modo transversal fundamental TEM00. Quando polarizado por lâmina de Brewster atingiu 100,5W de potência de saída com 91% de polarização. Quando o ressonador foi polarizado com um polarizador de filme fino, obteve-se melhora na qualidade de feixe e um aumento na polarização, com o valor de M2 sendo 1,56 e 1,84 nas direções x e y respectivamente com 95,4% de polarização. A potência de saída foi, ao nosso conhecimento, a mais alta obtida para lasers polarizados operando no modo fundamental e usando módulos lasers comerciais de Nd:YAG bombeados lateralmente por diodos sem nenhuma preparação especial.Dynamically stable operation with joined stability zones of a linearly polarized resonator is shown for a laser containing two diode side-pumped Nd:YAG rods with commercial laser modules. The unpolarised resonator provided 115 W of TEM00 output. When polarized by a Brewster plate, it reached 100.5 W of output power with 91% polarization. When the resonator was polarized by a thin film polarizer, an increase in beam quality was obtained with M2 values of 1.56 and 1.84 in the x and y directions, respectively with 95.4% polarization. The output power achieved is, to our knowledge, the highest reported for polarized, fundamental-mode lasers using commercial, diode side-pumped Nd:YAG modules without any special preparation.
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Eichenseer, Mario. "Aufbau und Charakterisierung eines hochstabilen Nd:YAG-Lasers für ein Indium-Frequenznormal." [S.l.] : [s.n.], 2003. http://edoc.ub.uni-muenchen.de/archive/00001672.
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Schöne, Wolfram. "Theoretische und experimentelle Untersuchung thermischer Effekte in diodengepumpten Hochleistungs-Nd:YAG-Stablasern." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=954722914.
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Brozek, Oliver Sascha. "Frequenzstabilisierung eines Nd:YAG-Hochleistungs-Laser-Systems für den Gravitationswellendetektor GEO 600." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=95758041X.
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Eichenseer, Mario. "Aufbau und Charakterisierung eines hochstabilen Nd:YAG Lasers für ein Indium Frequenznormal." Diss., lmu, 2003. http://nbn-resolving.de/urn:nbn:de:bvb:19-16726.
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Brockmann, Rüdiger [Verfasser]. "Beitrag zum Mikronahtschweißen von Edelstahlfolien mittels diodengepumptem Nd:YAG-Laser / Rüdiger Brockmann." Aachen : Shaker, 2003. http://d-nb.info/1179021258/34.
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