Dissertations / Theses on the topic 'Lasers'
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1
Friart, Gaetan. "Semiconductor laser dynamics: two polarization feedback, quantum cascade lasers, and ring lasers." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/248835.
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Semiconductor lasers (Sls) are very sensitive to external perturbations which may destabilize their steady output. This is particularly striking when the SL is subject to optical feedback, i.e. when part of the light coming out of the laser is reinjected in the cavity after reflection from a distant mirror. For some applications, this is a nuisance that we wish to avoid. But optical feedback may also drive the laser into dynamical regimes which are useful for new applications. In this thesis, we study different problems where an SL is subject to a delayed feedback or to an injected signal. These problems are motivated by recent experiments, technological issues, or particular dynamical phenomena. Specifically, we combine analytical techniques, numerical simulations, and experiments to investigate the bifurcation mechanisms leading to a large variety of oscillatory outputs. The systems that we discuss are an edge-emitting laser with polarization-rotated optical feedback, a two-mode laser with optical injection, a quantum cascade laser with optical feedback, and a semiconductor ring laser with optical feedback. We show that the bifurcations from the steady-states are of primary importance. They not only delimit the stability boundaries of the laser output but they also form the backbone structure of many pulsating waveforms. We investigate these bifurcations in detail in order to find the best operating conditions to observe specific dynamical regimes. Our results highlight laser key parameters that allow their efficient control.Les lasers à semi-conducteur sont sensibles aux perturbations externes et celles-ci peuvent déstabiliser leur faisceau de sortie d’intensité constante. Ceci est particulièrement marquant quand le laser à semi-conducteur est sujet à un feedback optique, c’est-à-dire quand une partie de la lumière sortant du laser est réinjectée dans sa cavité après réflexion par un miroir distant. Pour certaines applications, cela représente une nuisance que l’on souhaite éviter. Mais le feedback optique peut aussi engendrer des régimes dynamiques utiles pour de nouvelles applications. Dans cette thèse, nous étudions différents problèmes où un laser à semi-conducteur est soumis à un feedback retardé ou à un signal injecté. Nos travaux sont motivés par de récentes expériences, des questions technologiques ou des phénomènes dynamiques particuliers. Nous combinons des techniques analytiques, des simulations numériques ainsi que des expériences afin d’analyser les mécanismes de bifurcation menant à une large variété de régimes oscillants.Nous étudions en premier lieu la dynamique d’un laser à semi-conducteur soumis à un feedback avec rotation de la polarisation. Nous examinons, à la fois théoriquement et expérimentalement, la séquence de bifurcations menant à des oscillations sous forme d’ondes carrées. Nous mettons en évidence une multistabilité entre différentes ondes carrées de périodes spécifiques. Nous introduisons alors un mécanisme de contrôle qui nous permet de sélectionner l’onde carrée désirée. Nous analysons ensuite les frontières de stabilité d’un laser à semi-conducteur à deux polarisations soumis à une injection optique. Nous montrons que si les gains des deux modes de polarisation sont suffisamment proches, un état stationnaire mixte stable peut exister. Nous explorons également les conditions permettant une bistabilité entre un état stationnaire pur et un état stationnaire mixte. Les lasers à cascade quantique sont de nouveaux lasers à semi-conducteur prometteurs qui possèdent une forte tolérance au feedback optique. Nous examinons de façon systématique leur stabilité dans la limite des grands retards. Nous montrons que des instabilités oscillantes sont cependant possibles pour de faibles valeurs du courant de pompe. Le dernier dispositif que nous étudions dans cette thèse est le laser à semi-conducteur en anneau soumis à un feedback optique. Nous identifions le mécanisme de bifurcation, appelé pont de bifurcation, responsable des instabilités oscillantes dans le faisceau de sortie du laser. Ces oscillations sont indésirables pour la plupart des applications impliquant de tels lasers. Nous montrons qu’elles peuvent être évitées en contrôlant la phase du feedback.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
2
Wadsworth, W. J. "Copper vapour laser pumped TI:sapphire lasers." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389029.
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Maker, Gareth Thomas. "Diode laser pumped solid state lasers." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/397281/.
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This thesis deals with the development of diode laser pumped solid state lasers. The earliest work presented enabled 125W peak power, single frequency Q-switched pulses to be obtained from a 100mW diode laser pumped Nd:YAG laser. Using a 500mW diode laser as a pump source for C.W. Nd:YAG and Nd:YLF oscillators an Yb:Er fibre laser was pumped, producing 0.75mW C.W. power at a wavelength of 1.56µm. Acousto-optic mode-locking techniques were used to provide C.W. mode-locked pulse durations in Nd:YAG and Nd:YLF of 55ps and 18ps respectively, at repetition rates of 240MHz. Frequency modulation mode-locking was shown to be a superior technique, giving pulse durations of 11.5ps and 10ps in diode laser pumped Nd:YAG and Nd:YLF oscillators respectively. FM operation of diode laser pumped Nd:YAG lasers was investigated, yielding a maximum FM bandwidth of 70GHz. Spatial hole burning was considered to be an important factor in this result. Using a 1W diode laser to pump a mode-locked and Q-switched Nd:YLF oscillator peak power levels of 70kW were obtained at a wavelength of 1.047µm. Frequency doubling this output in MgO:LiNbO3 with an energy conversion efficiency of 47% enabled other tunable lasers to be pumped using the second harmonic. Firstly, a synchronously pumped rhodamine 6G dye laser is described which is capable of producing 3.2ps mode-locked pulses in a Q-switched envelope with peak powers of around 10kW. Secondly, a synchronously pumped doubly resonant optical parametric oscillator tunable between 983nm and 1119nm is described. Lastly, a Ti:Sapphire laser producing 400ns pulses with peak powers of 3W at a wavelength of 755nm is demonstrated. This oscillator could be wavelength tuned between 746nm and 838nm. A highly efficient method of frequency doubling C.W. mode-locked lasers was developed. Using an external resonant cavity a frequency doubling energy conversion efficiency of 61% to 532nm was achieved, giving 87mW average power in 8.5ps pulses.
4
Kapitan, Daniel. "Laser ablation with copper vapour lasers." Thesis, University of Oxford, 1999. https://ora.ox.ac.uk/objects/uuid:a1dc1a3b-602a-4ebb-abe2-734e8e11f15a.
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The use of copper vapour lasers for laser ablation in laser materials processing applications is studied. To this purpose, the generation of near diffraction-limited beam quality output from a single medium-scale oscillator is demonstrated via matching the total buffer gas pressure to the specific electrical input power loading and the degree of insulation of the plasma tube. The design and characterisation of a Master-Oscillator Power-Amplifier system based on a smallbore oscillator is also described, focusing on pulse stretching techniques to provide efficient seeding required for producing 20-50 W high beam-quality output for laser materials processing purposes. Various experimental studies on the fundamental processes of laser ablation of metals are presented. The effect of the background gas properties on shock-wave formation in laser generated plasmas is studied using a ballistic pendulum. The experimental findings are found to be accurately described by a modified Sedov-Taylor-Von Neumann theory which accounts for the effect of the piston-mass. The theory is applied to characterise the fluorination process in the shock-wave, in view of oxygen isotope analysis in geochemistry. Atomic emission spectroscopy is shown to provide some measure of the electron temperature and electron density at the plasma core. The experimental results are discussed in view of existing models to describe the extreme Stark-broadening and self-absorption in dense, cool plasmas. A comparative study of the use of femtosecond and nanosecond pulsed lasers for laser ablation of metals is presented to assess the relative importance of thermal diffusion. Measurement of the recoil momentum due to ejection of molten particulates during ablation in vacuum provides insight into the effect of material properties. Diffusion-limited surface texturing of metals via direct transfer of an optical interference patterns is demonstrated.
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Rabeendran, Nishanthan. "New Approaches to Gyroscopic Lasers." Thesis, University of Canterbury. Physics and Astronomy, 2013. http://hdl.handle.net/10092/8609.
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This thesis presents a study of two aspects of ring laser gyroscopes: Correction of systematic errors due to optical backscatter, and development of solid-state ring laser gyroscopes.
Backscatter at the optical surfaces of ring laser gyroscopes causes systematic measurement errors. These errors were modelled and corrected for in large ring lasers. The model included backscattering, hole burning and dispersion in the gain medium. The model predictions were used in conjunction with measurements of
the intensity modulation of each beam and the phase difference between these modulation to correct the measured Sagnac frequency of the large ring lasers, PR-1 and G-0. Dramatic improvements in the sensitivity of both lasers were achieved.
Most current laser gyroscopes use He-Ne plasma as the gain medium. This makes the devices fragile, the plasma creates UV light that degrades the cavity mirrors and the gas itself degrades over time. As a alternative, solid state materials might be used as the gain medium for the gyroscope. Both neodymium doped and erbium ytterbium co-doped phosphate glass lasers were constructed. Initially linear cavity designs were constructed to test the suitability of the gain media. Both laser systems employed longitudinal laser diode pumping. Thirty six perimeter ring lasers were then developed using both gain media. In both cases successful rotation sensing was achieved on a turntable which provided external rotation. For rotation rates between 0.1 and 0.85 rad/s, the gyroscope built using Er-Yb and Nd phosphate glass are superior to Nd:YAG (the only other material known to have been used in a continuous wave solid state gyroscope). This improvement is due to the use of thin heavily doped gain medium, which decreases the detrimental effect caused by gain gratings.
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Hempler, Nils. "Semiconductor disk laser pumped Cr²⁺:chalcogenide lasers." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=15339.
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Chaaban, Hani. "Etudes et conception de sources lasers. Mise au point de lasers submillimétriques : application à l'analyse des spectres induits." Aix-Marseille 3, 1988. http://www.theses.fr/1988AIX30051.
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Un laser co#2 continu construit au laboratoire est stabilise en puissance et utilise pour pomper un laser moleculaire. L'utilisation du methanol comme milieu amplificateur permet d'apprecier le fonctionnement sur de nombreuses raies irl. Deux lasers co#2 a impulsions balayables et monomodes ont ete perfectionnes, permettant par l'intermediaire d'un cristal non lineaire d'obtenir la generation d'ondes submillimetriques par difference des frequences (voisines) des lasers primaires. Une application est faite a l'etude du spectre induit de l'azote vers quelques cm##1. On calcule les moments spectraux et les temps de relaxation
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Zhu, Xiang. "Tunable diode lasers and their applications in trace gas and liquid detection /." *McMaster only, 1996.
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Serres, Serres Josep Maria. "Continuous-wave and passively Q-switched solid-state microchip lasers in the near-infrared." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/460758.
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Aquest treball tracta de la caracterització de làsers compactes d'estat sòlid, amb un primer enfocament, l'estudi del
concepte microxip aplicat al làser en diversos hostes cristal·lins dopats amb terres rares. Es reporta els resultats sobre
l'estudi de l'efecte de thermal lens, necessari per a l'obtenció de làser amb aquesta configuració, així com pel
funcionament làser amb continu i polsat utilitzant la tècnica Q-switch.
En els experiments, el concepte microxip es defineix com una cavitat làser quasi monolítica. Aquest concepte s'estudia
per a diferents emissions de làser a ~1.06 m d'ions Yb3+ i Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hi ha
~2.05 m del Ho3+.
En el règim d'ona contínua s'examina detalladament per als ions de lantànids trivalents esmentats en diversos hostes
cristal·lins amb l'objectiu de comparar el potencial de cada material. En aquest treball, es demostren eficiències molt
properes al límit teòric.
D'altra banda, també es presenten làsers polsats d'estat sòlid amb la configuració microxip amb diversos absorbidors
saturables. Amb aquest propòsit, s'utilitzen com a absorbidors saturables nous nanomaterials com el MoS2, nanoestructures
de carboni (SWCNT, el grafè d'una i de diverses capes) i un SESA. A més, el més convencional Cr:YAG
(~1.06 m) i el Cr:ZnS (~1.9 m) s'examinen per comparar els seus rendiments.Este trabajo trata de la caracterización de láseres compactos de estado sólido, con primer enfoque, el estudio del concepto microchip aplicado al láser en varios huéspedes cristalinos dopados con tierras raras. Se reporta los resultados sobre el estudio del efecto de la thermal lens, necesario para la obtención de láser con esta configuración, así como para el funcionamiento láser en continuo y pulsado utilizando la técnica Q-switch. En los experimentos, el concepto microchip se define como una cavidad láser casi monolítica. Este concepto se estudia para diferentes emisiones de láser a ~1.06 m de los iones Yb3+ y Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hay ~2.05 m del ion Ho3+. En régimen de onda continua se examina detalladamente para los iones de lantánidos trivalentes mencionados en varios huéspedes cristalinos con el objetivo de comparar el potencial de cada material. En este trabajo, se demuestran eficiencias muy cercanas al límite teórico. Por otra parte, también se presentan láseres pulsados de estado sólido con la configuración microchip con varios absorbedores saturables. Con este propósito, se utilizan como absorbedores saturables nuevos nanomateriales como el MoS2, nano-estructuras de carbono (SWCNT, el grafeno de una y de varias capas) y un SESA. Además, el más convencional Cr:YAG (~1.06 m) y el Cr:ZnS (~1.9 m) se examinan para comparar sus rendimientos
This work deals with the characterization of compact solid state lasers, as a first approach to the study of the microchip laser concept applied to several rare earth-doped crystalline hosts. The results on the study of the thermal lens, required for the microchip laser operation as well as the continuous wave and passive Q-switched laser operation in microchip configuration are reported. In the experiments, the microchip concept is defined as a quasi-monolithic laser cavity. Such a concept is studied for different laser emissions at ~1.06 μm from Yb3+ and Nd3+ ions, at ~1.3 μm from Nd3+, at ~1.95 μm from Tm3+ and at ~2.05 μm from Ho3+. The continuous wave regime is examined in detail for the above mentioned trivalent lanthanide ions embedded in several crystalline hosts with the aim to compare the potential of each gain material. Slope efficiencies very close to the theoretical limit are demonstrated in this work. On the other hand, microchip solid state lasers passively Q-switched with several saturable absorbers are also presented. For this purpose, novel nanomaterials such as MoS2, carbon nanostructures (SWCNTs, single- and multilayer graphene) and a SESA are used as saturable absorbers. Besides, the most conventional Cr:YAG (~1.06 μm) and Cr:ZnS (~1.9 μm) are examined to compare their performance.
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Kifle, Esrom Aschenaki. "Fabrication and characterization of waveguide lasers operating in the infrared spectral range." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/668351.
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Aquest treball de tesi ha tractat la fabricació i la caracterització de làsers de guia d’ona compactes i eficients que funcionen en règims d’ona contínua i Q-commutat de forma passiva al voltant dels 2 micròmetres en l’espectre electromagnètic. Per aconseguir-los, es van utilitzar materials cristal•lins basats en tungstats dobles d’estructura monoclínica dopats amb erbi (Er3+), tuli (Tm3+) o holmi (Ho3+). Aquests materials làser es van escollir per les seves propietats òptiques d’emissió i absorció que els fan aptes per aconseguir dispositius compactes. Per a la fabricació i l'estructuració de les guies d'ona, es va utilitzar la combinació dels següents mètodes: creixement cristal•lí en solució a alta temperatura, creixement d’epitàxies en fase líquida, tall amb serra micromètrica de diamant i escriptura directa per làser de femtosegons. A més, es van implementar diferents tècniques de caracterització com la microscòpia confocal, μ-Raman i μ-luminescència per avaluar la qualitat i la idoneïtat de les guies d'ones. En el règim d’ona Q-commutat de forma passiva, es va estudiar la idoneïtat de diferents absorbidors saturables, com ara cristalls de ZnSe o ZnS dopats amb Cr2+, MoS2 i nanoestructures de carboni (grafè i els nanotubs de carboni) dipositats sobre un substrat transparent o directament a la superfície de la mostra que contenia les guies d'ones. La fabricació d’una guia d’ona acanalada superficial mitjançant creixement epitaxial va donar com a resultat una eficiència làser rècord gairebé aproximada al límit teòric. Es van fabricar i estudiar guies d'ones soterrades (canals) fabricades mitjançant un làser de femtosegon. Igualment, es van fabricar i estudiar guies d'ona acanalades en superfície (forma d'anell) i separadors en forma de Y. Finalment, es van demostrar làsers de guia d’ona capaços d’oferir una potència de sortida de nivell de watts, així com làsers de guia d’ona en règim Q-commutat de forma passiva molt estable.Este trabajo de tesis ha tratado la fabricación y caracterización de láseres de guía de onda compactos y eficientes que funcionan en los regímenes de onda continua y Q-conmutado de forma pasiva alrededor de los 2 micrómetros en el espectro electromagnético. Para lograrlos, se emplearon materiales cristalinos basados en tungstatos dobles de estructura monoclínica dopados con erbio (Er3+), tulio (Tm3+) u holmio (Ho3+). Los medios de ganancia fueron elegidos debido a sus propiedades ópticas de emisión y absorción que los hacen adecuados para lograr dispositivos compactos. Para la fabricación y estructuración de las guías de onda se utilizó una combinación de los métodos: crecimiento cristalino en solución a alta temperatura, crecimiento epitaxial en fase líquida, corte con sierra micrométrica de diamante y escritura directa por láser de femtosegundo. Además, se implementaron diferentes técnicas de caracterización, como la microscopía confocal, μ-Raman y μ-luminiscencia para evaluar la calidad y la idoneidad de las guías de onda. En el régimen de operación Q-conmutado pasivo, se estudió la idoneidad de diferentes absorbentes saturables, como los cristales de ZnSe o ZnS dopados con Cr:2+, el MoS2 y las nanoestructuras de carbono (grafeno y los nanotubos de carbono) depositados sobre un sustrato transparente o directamente sobre la superficie de la muestra que contiene las guías de onda. La fabricación de una guía de onda acanalada superficial mediante crecimiento epitaxial resultó en una eficiencia láser récord muy próximo al límite teórico. Se fabricaron y estudiaron guías de onda enterradas fabricadas mediante escritura con láser de femtosegundo. Se fabricaron y estudiaron guías de onda acanaladas en superficie (revestimiento en forma de anillo) y divisores en forma de Y. Finalmente, se demostraron láseres de guía de onda capaces de generar una potencia de salida de vatios, así como láseres de guía de onda en régimen Q-conmutado pasivamente muy estable.
This thesis work has dealt with the fabrication and the characterization of compact and efficient waveguide lasers operating in the continuous wave and passively Q-switched operation regimes around 2 μm in the spectral range. To achieve those, erbium (Er3+), thulium (Tm3+) or holmium (Ho3+) doped monoclinic double tungstate crystalline materials were employed. The gain media were chosen due to their ability to generate polarized laser emission and their large gain cross-sections which make them suitable for achieving compact devices. The combination of the top-seeded solution growth, liquid phase epitaxy, diamond saw dicing and femtosecond direct laser writing methods were employed for fabricating and structuring the waveguides. Furthermore, different characterization techniques such as confocal microscopy, μ-Raman, and μ-luminescence mapping were implemented to assess the quality and suitability of the fabricated waveguides for lasing application. In the passively Q-switched operation regime, the suitability of different saturable absorbers such as transition-metal-doped chalcogenide crystals (Cr2+:ZnSe or ZnS), few-layer transition metal dichalcogenide (MoS2) and carbon nanostructures such as graphene and single-walled carbon nanotubes deposited on a transparent substrate or directly onto the surface of the sample containing the waveguides were tested. The fabrication of an epitaxially grown surface channel waveguide resulted in a record slope efficiency almost approaching the theoretical limit. Femtosecond laser written buried channel waveguides (with circular and hexagonal optical-lattice-like cladding), surface channel waveguides (with half-ring-shaped cladding) and Y-branch splitters were fabricated and studied. Waveguide lasers capable of delivering a watt-level output power as well as those with a stable passive Q-switching operation were demonstrated.
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Stetler, Aaron M. "Active vibration control for free electron lasers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FStetler.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2003.Thesis advisor(s): Bruce C. Denardo, Thomas J. Hofler. Includes bibliographical references (p. 81). Also available online.
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SANTOS, ROBERTO de B. "Microfuracao com laser pulsado." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10900.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Hönninger, Clemens. "Ultrafast ytterbium-doped bulk lasers and laser amplifiers /." [S.l.] : [s.n.], 1998. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12952.
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Edwards, Matthew. "Characterisation and laser applications of X-ray lasers." Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428485.
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Roth, Peter. "Directly diode-laser-pumped titanium-doped sapphire lasers." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18125.
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Titanium-doped sapphire is one of the most versatile laser gain materials. Tunable between 0.7 m and 1.1 m and capable of generating femtosecond pulses, the Ti:sapphire laser has become an important tool for many applications. Its ubiquitous use across many scientific disciplines is increasingly complemented by commercial applications including imaging, spectroscopy, micro-processing of materials and the generation of terahertz radiation. However, today's Ti:sapphire lasers are complex, bulky and expensive, leaving many applications unaddressed, particularly where lower costs and smaller footprints are vital. The biggest hurdle to smaller and cheaper Ti:sapphire lasers is the pump light source - typically a frequency-doubled, multi-watt neodymium or optically pumped semiconductor laser. Ideally, such intricate and expensive pump lasers would be replaced by compact, robust and cheap diode lasers. Two factors have prevented this: first, Ti:sapphire has a broad but relati vely weak absorption in the blue-green region of the spectrum where high-power diode lasers are not currently available; and second, the very short upper laser level lifetime of Ti:sapphire and relatively large parasitic losses result in a high intrinsic laser threshold. Combined, these factors strongly favour high-brightness pump sources. The recent progress in diode lasers based on gallium nitride materials now opens the way to challenge the perceived wisdom that Ti:sapphire cannot be diode-pumped. In this work diode-laser pumping of Ti:sapphire lasers has been shown to be possible. The world's first diode-laser-pumped Ti:sapphire laser has been developed, enabling drastic reductions in cost and size over current systems. Using innovative approaches to exploit gallium nitride diode lasers as the pump source, both continuous-wave operation and generation of femtosecond pulses have been demonstrated. As a result, some of the unrivalled performance of today's high-cost, lab- bound Ti: lasers may soon be available at a fraction of the current cost and footprint.
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Gallaher, Nigel R. "Narrow linewidth, diode laser pumped, solid state lasers." Thesis, University of St Andrews, 1994. http://hdl.handle.net/10023/13717.
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The design, construction, evaluation and development of an all solid state, narrow linewidth laser source is presented. The narrow linewidth laser system was based on a miniature standing wave Nd:YAG laser cavity, end-pumped with 100mW of 809nm light from a fibre coupled GaAlAs diode laser array. This basic CW laser generated up to 30mW at 1064nm in a single, diffraction limited transverse mode (TEM00) but multi-longitudinal mode output beam. The laser had a pump power threshold of 24mW and an optical to optical slope efficiency of 39%. A simple rate equation based numerical model of this laser was developed to allow various design parameters such as length of Nd:YAG gain medium and amount of output coupling to be optimised. Excellent agreement between the numerical model predictions of the output power as a function of input pump power and experimental data from the optimised multi-longitudinal mode laser was obtained. To restrict this laser to operate on a single longitudinal mode, twisted cavity mode and intracavity etalon, mode selecting techniques were investigated. Both methods were found to produce reliable single mode laser operation and resulted in output powers at the 10mW level. The relative free running frequency stability between a pair of single longitudinal mode diode laser pumped Nd:YAG lasers was investigated. By isolating these lasers from environmental noise using a small, custom built anechoic chamber the linewidth of the optical heterodyne signal between the two free running lasers was reduced from tens of megahertz to around 10kHz measured on a millisecond time scale. Further improvement in linewidth was achieved by actively locking the laser frequency to a novel ultra high finesse (F~12,500, free spectral range ~500MHz) spherical mirror Fabry-Perot reference interferometer using the technique of Pound-Drever locking. The locked laser displayed a maximum frequency deviation of only 1kHz from the centre of the reference cavity transmission and a frequency noise spectral density of ~20Hz/ √Hz at 1kHz. In one of the first reported demonstrations of an all solid state injection seeded laser system, this single frequency laser was used to injection seed a diode laser array, transversely pumped, Q-switched Nd:YAG laser to produce 0.25mJ, 35ns pulses in a single longitudinal, single transverse mode beam. Preliminary results on injection locking between two single frequency diode laser pumped Nd:YAG laser are also reported. A novel frequency stabilisation scheme based on resonant optical feedback locking iproposed and some preliminary experimental work on this technique is presented.
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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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De, Kock Trevor Neil. "The development and evaluation of a Nd:YAG laser incorporating an unstable resonator." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1008566.
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Introduction: For approximately the last eight years the Laser Section of the National Physical Research Laboratory (NPRL) has been interested in inter alia, pulsed solid-state lasers and in particular, Nd:YAG. Investigations of various resonator types were undertaken with a view to the improvement of the laser parameters such as output energy, pulse width, beam quality and sensitivity to mirror misalignment. In 1980 a Nd: YAG laser employing a rotating prism Q-switch was constructed (Preussler (1980)). It involves rotating one of the two cavity reflectors so that they are parallel for only a brief instant in time. Typically the prism must rotate at a speed of 20 000 r.p.m. to ensure a single pulse output. Such lasers suffer from the tendency to emit multiple pulses, they are very noisy and they require frequent maintenance because of the short lifetime of the bearings. A resonator employing conventional curved mirrors and an electro-optical Q-switch was constructed in 1980 (Robertson & Preussler (1982)). In 1981 an electro-optically Q-swi tched laser making use of a crossed Porro-prism resonator was investigated due to its relative insensitivity to misalignment of the reflectors compared with the conventional mirror resonator (Nortier (1981)). Improvements in terms of output power, beam divergence and beam quality can be achieved by making use of a so-called unstable resonator. Such a laser has been investigated and is reported on in this study. Chapter 2 provides some background into laser theory and operation while chapter 3 deals with the theory of the unstable resonator. Chapter 4 provides details of the experimental equipment and techniques used in the work and chapter 5 discusses the evaluation of the project and results obtained.
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Musaev, Omar Wróbel Jerzy. "UV laser assisted processing of InP at different ambient conditions with variable number of pulses and fluences." Diss., UMK access, 2006.
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Thesis (Ph. D.)--Dept. of Physics and School of Computing and Engineering. University of Missouri--Kansas City, 2006."A dissertation in physics and telecommunications networking." Advisor: Jerzy Wrobel. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 1, 2007. Includes bibliographical references (leaves 185-190). Online version of the print edition.
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Zhu, Shiqun. "Statistical fluctuations in laser transients." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/30993.
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Chardonnet, Christian. "Spectroscopie de saturation de haute précision et sensibilité en champ laser fort : applications aux molécules OSO4, SF6 et CO2 et à la métrologie des fréquences." Paris 13, 1989. http://www.theses.fr/1989PA132026.
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Ce mémoire présente des résultats théoriques et experimentaux obtenus à partir de l'étude des structures hyperfines dans la bande nu3 de la molécule oso4. L'observation à l'aide de lasers à co2 ultrastables et d'un spéctromètre à tres haute résolution et l'analyse de structures hyperfines de 189oso4 et 187oso4 ont conduit à la détermination tres précise de toutes les constantes hyperfines importantes des niveaux v3=0 et v3=1, grâce à l'observation de croisements de niveaux hyperfins. Une relation entre constantes de spin-rotation et de spin-vibration a étè montrée et interpretée. La difference avec sf6 a étè expliquée. Les diverses contributions à l'interaction quadrupolaire électrique dans 189oso4 ont étè dégagées; en particulier, le rôle de l'interaction de coriolis a étè mis en évidence. Une analyse détaillée de la signification des constantes hyperfines a étè menée et la comparaison avec les valeurs experimentales a mis en lumière certaines difficultès et ouvert un nouveau champ d'investigation. La première observation d'une raie de saturation de co2 avec une résolution de 2 khz a étè effectuée et la fréquence absolue d'une telle raie a étè mesurèe a 50 hz pres grâce à la mise au point d'une technique de compensation de la derivé du laser de réference qui a fortement amélioré les performances métrologiques du spectromètre; ceci reprèsente un gain de 2 ordres de grandeur. Par ailleurs, une intercomparaison avec le système laser+fabry-perot du lptf a révelé un accord au hz pres (3. E(14)) des deux systèmes, démontrant ainsi leurs qualités métrologiques inegalées a 10 microns. Lors de l'étude des croisements de niveaux hyperfins, il est apparu que les raies de saturation en présence d'un champ laser tres intense présentaient une distorsion très spectaculaire. Il a étè montré sur le plan experimental et théorique le rôle essentiel joué par la courbure des fronts d'
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Jacquet, Joel. "Évolution des diodes lasers pour les télécommunications optiques : Lasers accordables, Lasers à émission par la surface, Lasers bas coûts." Habilitation à diriger des recherches, Université Montpellier II - Sciences et Techniques du Languedoc, 2004. http://tel.archives-ouvertes.fr/tel-00922621.
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Les travaux présentés ci-après reprennent mes activités depuis le début de ma thèse en 1986. Ils ont été entièrement réalisés dans le centre de recherche d'Alcatel à Marcoussis dans le but de concevoir, réaliser et tester des composants optoélectroniques à semi-conducteurs pour des applications en télécommunications optiques. Ces composants sont à base de Phosphure d'Indium (InP) et sont destinés à émettre ou détecter de la lumière à des longueurs d'ondes proches de 1300 ou 1550 nm suivant l'application. J'ai pu bénéficier de toute l'infrastructure nécessaire au développement et à l'aboutissement des projets couvrant aussi bien les moyens technologiques (épitaxie et structuration des matériaux) que les moyens de caractérisation jusqu'aux expérimentations système grâce à l'utilisation de plate-formes de test disponibles à Alcatel. Les résultats présentés ici sont par conséquent le fruit d'un travail d'équipe ; je m'attacherai en fin de chaque paragraphe à préciser ma contribution personnelle aux résultats.
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Guionie, Marie. "Lasers à fibres bifréquences bipolarisations : stabilisation et montée en fréquence du battement." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S059.
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Cette étude porte sur les lasers à fibres bifréquences bipolarisations. Le contrôle de la différence de fréquence de ces lasers représente un enjeu important en photonique microonde. En effet, maîtriser le battement permettrait la réalisation de sources compactes et à faible bruit visant des applications de métrologie ou télécom. Nous travaillons ici sur des sources émettant à 1,5 μm, de type DFB ou DBR, soit dopés Er soit co-dopés Er-Yb. Ils présentent une fréquence de battement d'environ 1 GHz pour les DFB, et 100 MHz pour les DBR. Les objectifs de la thèse ont été, d'abord de stabiliser le battement, puis d'explorer différentes méthodes pour modifier la biréfringence de la fibre et ainsi accroître la fréquence de battement. Nous avons d'abord utilisé la méthode de stabilisation par boucle à verrouillage de phase pour asservir le battement sur une fréquence de référence. En nous servant de la diode de pompe comme actuateur, nous avons réussi à stabiliser des battements entre 300 MHz et 10 GHz pendant plusieurs jours. Ensuite, nous avons mis en place une méthode de stabilisation par réinjection optique décalée en fréquence. Un modèle théorique basé sur des équations-bilan couplées a été utilisé et a permis de retrouver les observations expérimentales. En stabilisant le battement sur une référence extérieure, différents régimes dynamiques ont été observés. Dans la zone stable, on réduit le bruit de phase jusqu'à −100 dBc/Hz à 1 kHz de la porteuse. Puis, nous avons couplé le montage de la réinjection optique a une ligne à retard, afin de stabiliser efficacement le battement sur lui-même. Enfin, nous avons étudié plusieurs pistes pour augmenter la fréquence de battement des lasers DBR pour répondre aux besoins des applications. Nous avons pu suivre en temps réel la modification de biréfringence photo-induite par un faisceau UV. Nous avons aussi étudié une méthode de modification réversible de la biréfringence, en exploitant l'effet élasto-optique. Quelque soit la méthode employée, nous avons observé un accroissement de la fréquence de battement depuis 100 MHz jusqu'à plus de 10 GHz dans le meilleur des casThis work is about dual-polarization dual-frequency fibers lasers. The control of the frequency difference of these lasers is a major challenge in microwave photonics. Controlling the beat frequency could allow compact and low-noise sources, in order to develop applications in metrology or telecom. Here, we focus on 1.5 μm sources, in either DFB or DBR configurations, made of Er-doped or co-doped Er:Yb silica fibres. Their beat frequency is about 1 GHz for DFB lasers, and 100 MHz for DBR lasers. This thesis investigates several methods to stabilize the beat note, then to modify the fiber birefringence, to increase the beat frequency. First, an optical phase-locked loop method is used to lock the beat note on a frequency reference. By using the pump diode as an actuator, we have successfully stabilized beat frequencies between 300 MHz and 10 GHz for days. We then study a stabilization method by frequency-shifted optical feedback. A theoretical model based on rate equations model is used and allows to retrieve the experimental observations. We observe different dynamical regimes by locking the beat note on a reference frequency. In the stable area, we reduce the phase noise to −100 dBc/Hz at 1 kHz from the carrier. Next, we have mixed the set-up of the injection-locking to a delay line, in order to effectively stabilize the beat note on itself. Finally, various approaches have been explored to increase the beat frequency of DBR lasers, to the needs of applications. It has been possible to continuously monitor the impact of a UV beam on the fiber birefringence. We also studied a method for reversible modification of the birefringence, exploiting the elasto-optical effect. Regardless of the method used, we observed an increase in the beat frequency from 100 MHz to more than 10 GHz in the best case
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Holden, Philip Bernard. "Numerical modelling of laser produced plasmas as XUV lasers." Thesis, University of York, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292556.
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Rossi, Sandro Marcelo. "PC-LASER : um software para simulação de lasers semicondutores." [s.n.], 1994. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258927.
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Orientador: Edson MoschimDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica
Made available in DSpace on 2018-07-23T11:46:05Z (GMT). No. of bitstreams: 1 Rossi_SandroMarcelo_M.pdf: 3646439 bytes, checksum: 44163bb4aef95b7dab797acb883b36ac (MD5) Previous issue date: 1994
Resumo: Devido ao baixo custo e o alto desempenho dos microcomputadores disponíveis hoje no mercado, a simulação em microcomputadores desempenha um papel cada vez mais importante na análise e projeto de componentes e sistemas. Nos últimos anos, um número cada vez maior de programas para simulação de sistemas de comunicação por fibras ópticas foram desenvolvidos e estão sendo utilizados para projetar estes sistemas. Um componente de fundamental importância no projeto destes sistemas de comunicação é a fonte óptica. Este trabalho apresenta o software PC-LASER, um programa desenvolvido para a simulação de alguns tipos de fontes ópticas, especificamente diodos laser de semicondutor, atualmente utilizados em sistemas ópticos de telecomunicação. Também são apresentados uma breve descrição dos fundamentos básicos dos lasers de semicondutor e os modelos matemáticos utilizados no desenvolvimento do programa. No final serão apresentados alguns exemplos, para verificar a validade dos modelos utilizados
Abstract: Today, the technology of PC-computer offers low cost and high performance machine that is possible to use it to simulate components and communication systems. The purpose of this work is to present the development of a specific computer enviroment to simulate and to analyse semiconductor laser diodes for applications in optical fiber telecommunication systems. In this work we present the basic fundamentaIs of these devices, their implemented mathematical models and the general organization and structure of the simulation software called PCLASER. Finnaly we provide some examples of simulation to verify and testing the power of the models proposed.
Mestrado
Mestre em Engenharia Elétrica
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Anderson, Andrew Alan. "Crystalline planar waveguide lasers fabricated by pulsed laser deposition." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394391/.
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This work describes the fabrication and performance characteristics of crystalline planar waveguide lasers produced by the pulsed laser deposition technique. This project was undertaken to establish that the pulsed laser deposition technique could be utilised to manufacture crystalline planar waveguide lasers with both rare earth and transition metal dopants. In the first instance a crystalline layer of neodymium doped Gd3Ga5O12 was grown on a Y3Al5O12, substrate. This structure was made to lase at ~1.06µm when pumped at 808nm using a Ti:sapphire laser. This result constitutes the first report of lasing in a pulsed laser deposited film. Further refinement of the deposition procedures resulted in a much improved set of films with waveguide losses as low as 0.5 dB/cm and absorbed pump power thresholds as low as 2.2mW. In the second case layers of Ti:sapphire (Ti doped a-Al203), of around 10 µm thickness, were grown on undoped sapphire substrates. These layers were examined by ion beam channelling and x-ray diffraction techniques which show that they have a level of crystalline perfection equal to the bulk grown material. The fluorescence. spectrum was also shown to be of the same form as that obtained from the bulk. These layers were also shown to be waveguiding. Finally, one such Ti:sapphire waveguide was made to lase around 800nm, when pumped with an argon ion laser. This was done with an absorbed pump power threshold of 0.56W using high reflectivity mirrors. A maximum quasi-CW output power of 357mW was achieved for an absorbed pump power of 3.44W using an output coupler with 35% transmission. True CW operation was also achieved, the first demonstration of CW lasing in a transition metal doped waveguide produced by pulsed laser deposition.
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Gévaudan, Alain. "Modélisation d'un laser à exciplexe XeCL à décharge par avalanche préionisée par faisceau de rayons X." Aix-Marseille 2, 1986. http://www.theses.fr/1986AIX22052.
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Laser xecl a decharge par avalanche preionisee par faisceau de rayons x, utilisant un circuit de decharge a condensateur de transfert ou a ligne de transmission. Les phenomenes electroniques presents au tout debut de l'avalanche de la decharge preionisee du laser sont etudies dans le but d'etablir les conditions necessaires a la formation homogene d'une decharge dans un grand volume. L'etude parametrique de l'optimisation du depot d'energie dans le milieu est effectuee a l'aide d'une modelisation des circuits de decharge. Le modele complet de laser xecl est ensuite etabli, permettant de simuler le modele experimental
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Sarmani, Abdul Rahman. "Yb-doped femtosecond lasers and their frequency doubling." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/781.
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Reppel, Julie-Ann. "Planar laser polarisation spectroscopy imaging in combustion /." Title page, abstract and table of contents only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phr4259.pdf.
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Chan, Kin Foong. "Pulsed infrared laser ablation and clinical applications /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992765.
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Taylor, Jason Matthew 1977. "Controlling molecules with lasers and lasers with molecules." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38638.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, February 2007.Includes bibliographical references (leaves 140-146).
I investigate quantum control of spin in molecules using shaped ultrafast lasers and the dynamics of those lasers when their cavities are modified to include programmable molecular masks. The ability to control quantum phenomena has had several large successes over the last decade. This field, known as Quantum Control, uses closed loop learning algorithms to shape ultrashort laser pulses in order to produce a desired state or state change. Interesting pulse shapes have been able to break chemical bonds, drive chemical reactions, selectively excite molecular states, and most recently, control photoisomerization in proteins [1, 2, 3]. In this thesis I began by seeking to apply this technique to manipulate spin. In our early work we pursued polarizing electron spins and nuclear spins for NMR Quantum Computation. We studied the electron spin triplet state properties of several molecules. Through this work we recognized that the laser and pulse shaper we were using could be modified to utilize the triplet properties of our molecules. We created a molecular triplet state spatial light modulator (SLM) to be used both outside and inside the laser cavity for ultrafast pulse shaping. The SLM consists of a liquid or thin film sample with a strong triplet state absorption.
(cont.) The molecule is selected to be transparent to the target light before pumping and strongly absorptive when pumped into the triplet state. The sample is exposed to laser light reflected off of a DMD chip to produce a 2D pattern to spatially populate the triplet ground state. This is, to our knowledge, the first triplet state ultrafast pulse shaper and the first all-optical inter-cavity spatial frequency modulator.
by Jason Matthew Taylor.
Ph.D.
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MAZIGHI, KHALED. "Lasers a centres colores pompes par diodes lasers." Caen, 1991. http://www.theses.fr/1991CAEN2038.
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L'amelioration d'un laser a centres colores utilisant le fluorure de sodium dope au magnesium pompe par une diode laser de puissance, a ete accomplie. Ce laser delivre actuellement 35 milliwatts en emission continue sous 480 milliwatts de pompe pour un miroir de sortie de 4 pourcent de transmission, et peut etre accorde entre 1009 et 1175 nanometres pour une transmission de 0,5% de son miroir de sortie; les centres actifs ne sont pas severement blanchis par ce mode de pompage. Le blocage des modes longitudinaux de ce laser a ete realise par deux methodes simples qui ne necessitent l'introduction d'aucun element intracavite. L'une consiste a moduler electriquement la diode laser par un signal sinusoidal haute frequence d'origine externe, et l'autre utilise un systeme de boucle de reaction opto-electronique ou une fraction de la lumiere emise sert a asservir la diode laser de pompe. Un laser a centres colores utilisant le bromure de potassium dope a l'oxygene emettant vers 2 micrometres a ete construit et mise en uvre avec pour source de pompage un autre laser a centres colores. C'est une premiere etape de la realisation d'un laser a centres colores, pompe par une diode laser pulsee a 1,55 micrometres
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Parrotta, Daniele Carmine. "Raman lasers intracavity-pumped by semiconductor disk lasers." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24895.
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Semiconductor disk lasers (SDLs) are efficient and commercially attractive devices as they can emit several Watts in continuous-wave (cw) operation, with good beam quality, low noise and great wavelength flexibility. SDL fundamental emission ranges from red to mid-infrared, while ultraviolet and other visible wavelength can be obtained via harmonic generation. This research shows that Raman conversion is an efficient way to extend the spectral coverage of well-established SDLs. The first experimental work consisted in the demonstration of a KGW Raman laser intracavity-pumped by a 1055 nm InGaAs SDL for laser emission at ~1.14 µm. This work represents the first Raman conversion of an SDL ever reported. Output power up to 0.8 W, broad wavelength tunability and cascaded Raman conversion (with low output coupling) were observed. The following experiment consisted in using synthetic single-crystal diamond as the Raman medium. In the last few years diamond has become a prominent Raman crystal as it provides high Raman gain, large Stokes shift and unrivalled thermal conductivity. A diamond Raman laser intracavity-pumped by an InGaAs SDL emitted up to 4.4 W at 1228 nm and was tuned from 1209-1256 nm. With an optical conversion efficiency exceeding 14%, this laser rivals the optical efficiencies of other cw Raman lasers and, perhaps more importantly, SDLs with direct emission at ~1.2 µm. Orange emission, with maximum output power of 1.5 W at 614 nm and wavelength tuning from 604.5-619.5 nm, was obtained via intracavity second harmonic generation in the Raman laser cavity. Raman conversion of a red-emitting GaInP SDL using a synthetic diamond crystal is also reported. As GaInP SDLs are less efficient than InGaAs SDLs, Raman threshold was more difficult to achieve, despite the Raman gain increasing for decreasing wavelengths. Nonetheless, Raman conversion in the deep red was observed, with output power of few tens of ~W, due to the low output coupling for the Raman laser, and tunable emission from 738-748 nm. This work is still at an early stage, so higher output power and enhanced laser efficiency may be achieved in future experiments.
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Wang, Yuchen, Xiushan Zhu, Jie Zong, Kort Wiersma, Arturo Chavez-Pirson, Robert A. Norwood, and N. Peyghambarian. "SESAM Q-switched fiber laser at 1.2 mu m." IEEE, 2016. http://hdl.handle.net/10150/622787.
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Q-switched operation of a holmium-doped fluoride fiber laser at 1.2 mu m wavelength induced by a semiconductor saturable absorber mirror (SESAM) is reported. 650 ns pulses with 0.13 mu J pulse energy at a repetition rate of 260 kHz were obtained.
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Naylor, G. A. "Recombination lasers." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355788.
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Johnson, Kristie Shureen. "Ce:LiLuf4 lasers." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:6e3f763c-ebb4-4959-974b-aa5ae447c51b.
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The research in this project was directed, firstly towards gaining an understanding of the effect excited-state absorption (ESA) has on gain and lasing in broadly tunable Ce:LiLuF lasers and secondly towards the development of Ce:LiLuF lasers suitable for spectroscopic applications. Detailed measurements of the single-pass, small-signal gain in Ce:LiLuF were undertaken, with a gain coefficient as high as 30±1 cm-1 at 309 nm, with an absorbed pump fluence of 0.46 Jcm-2. Further, the ESA in Ce:LiLuF at 261 nm and 349 nm was measured. Using both the gain and ESA results in a computer model, the effective gain cross-sections at 309 nm and 327 nm and the ESA cross-sections at 261 nm, 309 nm, 327 nm and 349 nm were determined. The ESA cross-sections were found to be of the order of 10-18 cm2. The effective gain cross-section in Ce:LiLuF was found to increase with decreasing temperature. This was proposed to arise from a decrease in the ESA cross-section with decreasing temperature in the Ce:LiLuF. An in-depth parametric study of Ce:LiLuF laser operation and tunability was undertaken. The results of these studies, together with computer modelling, enabled the importance of ESA and other effects on lasing to be established. In particular, the gain competition effects and ESA were found to lead to inefficient laser operation unless σ-polarised lasing was suppressed. With polarisation selection, efficient operation was obtained, with continuous tunability between 305 nm - 335 nm. Narrow bandwidth operation of Ce:LiLuF for use in OH radical detection in the atmosphere was investigated. Narrow bandwidth operation was achieved for the first time in Ce:LiLuF using a Eittrow grating with a telescopic and prism beam expansion system. Tunable lasing between 306.5 nm and 311.5 nm was obtained, with a spectral bandwidth of 0.7 cm-1. Finally, highly efficient Ce:LiLuF lasing was achieved with a new all-solid-state, 289 nm frequency-quadrupled Raman-shifted Nd:YAG laser. Slope efficiencies as high as 62±3% were achieved. This slope is believed to be the highest obtained in any cerium laser to date. The IR-to-UV conversion efficiency was 0.41% and the UV-to-UV conversion efficiency was 41%. These high efficiencies were attributed to high pump beam quality and good mode matching.
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Backes, Sacha Akira. "Microdisk lasers." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624363.
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Hillier, David Ianto. "Holographic lasers." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/65502/.
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This thesis presents the development of CW adaptive solid state lasers which dynamically correct for phase distortions within their cavity by phase conjugation. A fibre based four-wave mixing scheme is investigated but no experimental evidence of any phase conjugation is observed.
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Conroy, Richard. "Microchip lasers." Thesis, St Andrews, 1998. http://hdl.handle.net/10023/531.
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CAVELIER, MARC. "Etude de la dynamique des lasers a semiconducteurs : lasers a puits quantiques et lasers conventionnels." Paris 11, 1992. http://www.theses.fr/1992PA112237.
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Les lasers a puits quantiques constituent des sources remarquables par leur compacite et leurs performances dynamiques sous injection electrique. Par un traitement perturbatif des equations de la matrice densite, nous calculons la susceptibilite electromagnetique du milieu actif, pour des structures a puits quantiques ou massives. Nous montrons les avantages dus a la quantification pour le gain differentiel et le facteur de couplage phase-amplitude. Dans ce modele, la non-linearite du gain, proportionnelle a l'intensite de l'emission stimulee, est independante du type de structure si les temps de relaxation intrabande sont identiques. Les mesures sous seuil et en modulation petit signal des performances dynamiques de lasers a puits quantiques confirment les avantages des structures a puits quantiques quant au gain differentiel et au facteur de couplage phase-amplitude. En revanche, la non-linearite du gain est nettement renforcee et les performances ultimes de modulation ne sont pas ameliorees. D'autre part, la non-linearite du gain depend du nombre de puits dans la region active. Les phenomenes de transport au sein de la region active pourraient en etre a l'origine. Enfin, nous presentons une approche analytique de la commutation de gain qui montre l'influence de la non-linearite du gain sur la dynamique. Cette approche, appliquee aux resultats de mesures impulsionnelles effectuees sur des lasers fabry-perot monodes accordables dans une cavite externe tres longue, tres selective et tres attenuatrice, a montre les tres bonnes performances dynamiques des lasers a puits quantiques contraints. Ces etudes ont aussi confirme les fortes valeurs du gain differentiel et de la non-linearite de gain dans les lasers a puits quantiques
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Resan, Bojan. "DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2907.
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A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.Ph.D.
Other
Optics and Photonics
Optics
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Chan, Mun Kit. "Atmospheric transmission windows for high energy short pulse lasers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FChan%5FMun.pdf.
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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, December 2003.Thesis advisor(s): Donald L. Walters, Alfred W. Cooper. Includes bibliographical references (p. 73-74). Also available online.
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Savels, Tom. "Scattering lasers an exploration of the smallest lasers possible /." [S.l. : Amsterdam : s.n] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/42004.
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Bettaibi, Islam. "Développement et caractérisation des lasers XUV créés par laser femtoseconde." Phd thesis, Ecole Polytechnique X, 2005. http://tel.archives-ouvertes.fr/tel-00179321.
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Les sources XUV cohérentes présentent un potentiel important d'applications scientifiques, médicales et industrielles. Le développement des lasers ultra intenses a permis la réalisation de nouvelles sources XUV cohérentes et brèves, comme la génération d'harmonique d'ordre élevée et les lasers XUV. Ces sources sont compactes, peu coûteuses par rapport aux sources classiques telles que les synchrotrons, et présentent donc un intérêt tout particulier.Cette thèse présente une série d'études sur une nouvelle source laser XUV, pompée par un laser femtoseconde fonctionnant à 10 Hz. Un laser ultra intense est focalisé dans une cellule remplie de xénon ou de krypton et crée une colonne de plasma. Une émission laser à 41,8 nm dans le xénon IX ou à 32,8 nm dans le krypton IX est alors obtenue sur l'axe du laser de pompe. Nous avons réalisé une étude à la fois expérimentale et numérique de ce type de source dans le but de caractériser l'importance de différents paramètres tels que l'intensité et polarisation du laser, la pression du gaz et la longueur de la cellule. Cette thèse présente aussi une étude des profils spatiaux et temporels de l'émission laser.
Afin de compenser la réfraction du laser de pompe, nous avons utilisé deux techniques de guidage qui ont permis un allongement significatif de la zone amplificatrice du plasma. La première repose sur la création d'un canal plasma par décharge électrique et la deuxième sur les réflexions sur les parois internes de tubes diélectriques de saphir ou de verre. Dans les deux cas une amélioration spectaculaire des performances de la source a été observée.
Finalement, nous présentons dans ce manuscrit une étude préliminaire sur un autre schéma de pompage de laser X: par photo ionisation en couches internes d'atomes neutres. Nous avons développé un système optique qui devrait permettre la réalisation d'une onde inhomogène femtoseconde absolument nécessaire pour ce type de laser X.
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Tolchard, J. M. "Doppler free laser spectroscopy of atomic hydrogen using pulsed lasers." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383868.
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Bettaïbi, Islam. "Développement et caractérisation des lasers XUV crées par laser femtoseconde." Palaiseau, Ecole polytechnique, 2005. http://www.theses.fr/2005EPXX0035.
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Les sources XUV cohérentes présentent un potentiel important d'applications scientifiques, médicales et industrielles. Le développement des lasers ultra intenses a permis la réalisation de nouvelles sources XUV cohérentes et brèves, comme la génération d'harmonique d'ordre élevée et les lasers XUV. Ces sources sont compactes, peu coûteuses par rapport aux sources classiques telles que les synchrotrons, et présentent donc un intérêt tout particulier. Cette thèse présente une série d'études sur une nouvelle source laser XUV, pompée par un laser femtoseconde fonctionnant à 10 Hz. Un laser ultra intense est focalisé dans une cellule remplie de xénon ou de krypton et crée une colonne de plasma. Une émission laser, à 41,8 nm dans le xénon IX ou à32,8 nm dans le krypton IX est alors obtenue sur l'axe du laser de pompe. Nous avons réalisé une étude à la fois expérimentale et numérique de ce type de source dans le but de caractériser l'importance de différents paramètres tels que l'intensité et polarisation du laser, la pression du gaz et la longueur de la cellule. Cette thèse présente aussi une étude des profils spatiaux et temporels de l'émission laserCoherent soft x-ray sources have an important potential for scientific, medical and industrial applications. The development of high intensity laser systems allowed the realization of new coherent and fast soft x-ray sources like high order harmonic generation and soft x-ray lasers. These sources are compact, cheaper than traditionnal sources such as synchrotrons, and are thus interesting. This thesis presents the study of a new soft x-ray laser pumped by a femtoseconde laser beam working at 10 Hz. The circularly polarized ultra intense laser is longitudinally focused in a cell filled with xenon or krypton, to obtain the amplification of two lasing lines at 41,8 nm and 32,8 nm in Pd-like xenon and Ni-like krypton respectively. Wecarry out an experimental and numerical study of the source to understand the importance of different parameters such as the laser intensity and polarization, the gas pressure and the cell length. We have also spatially and temporally characterized the soft x-ray laser beam
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Bettaïbi, Islam Sebban Stéphane. "Développement et caractérisation des lasers XUV crées par laser femtoseconde." [S. l.] : [s.n], 2005. http://www.polymedia.polytechnique.fr.
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Piccioni, Máyra Andressa Rodrigues Valinhos [UNESP]. "Resistência de união ao microcisalhamento de sistemas adesivos autocondicionates com graus de acidez distintos: efeito de diferentes tratamentos em substrato dentinário normal e hipermineralizado artificialmente." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110816.
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000794165.pdf: 10547285 bytes, checksum: 527da52509be61f1455018679a53af74 (MD5)O objetivo deste trabalho, dividido em três estudos: foi avaliar a resistência de união de diferentes sistemas adesivos autocondicionantes, com graus de acidez distintos, frente a diferentes tratamentos dentinários: condicionamento ácido, laser e ponta diamantada em dentina normal e hipermineralizada artificialmente. No primeiro estudo, foi realizada uma busca na literatura sobre o uso do laser Er;Cr:YSGG na Odontologia Restauradora. Nos segundo e terceiro, duzentos e vinte e quatro (n = 224) molares humanos hígidos foram selecionados. Os dentes tiveram seu terço oclusal seccionado com o objetivo de expor superfície dentinária plana e foram lixados para a exposição de uma superfície dentinária uniforme e “padronizada”. Os espécimes foram divididos aleatoriamente em dois diferentes grupos, de acordo com o tipo de dentina: normal (N/n=108) e hipermineralizada artificialmente (H/ n=116). O grupo H recebeu tratamento para hipermineralização e oito dentes foram selecionados aleatoriamente e observados em MEV para a confirmação do procedimento de hipermineralização. Os dentes de cada grupo foram divididos aleatoriamente em quatro diferentes subgrupos, de acordo com o sistema adesivo autocondicionante empregado: Clearfil S3 Bond e Optibond All in One – Passo único - (Artigo 2); Clearfil SE Bond e Adhese – Dois Passos – (Artigo 3). Cada subgrupo (n=9) recebeu diferentes tratamentos: (1) condicionamento convencional: aplicação do sistema adesivo autocondicionante segundo recomendações do fabricante; (2) condicionamento da superfície dentinária com laser Er,Cr:YSGG (Waterlase Millennium, Biolaser Technology, San Clement, CA, USA) + aplicação do sistema adesivo segundo recomendações do fabricante; (3) “asperização” da superfície dentinária com ponta diamantada 3098 + aplicação do sistema adesivo segundo recomendações do fabricante. Em seguida, matrizes transparentes...
The aim this work, divided in three studies, was evaluate the bond strength of different adhesive systems with different degrees of acidity, to different dentinal treatments: acid etching, laser and diamond bur in normal dentin and artificially hypermineralized dentin. In the first study, it was performed a literature review on the use of the Er,Cr : YSGG in Restorative Dentistry. In the second and third, two hundred twenty-four (n = 224) human molars were selected. The teeth had their third occlusal sectioned in order to expose flat dentin surface and it were ground to expose dentin surface uniform, standardized. The specimens were randomly divided into two groups according to the type of dentin normal (N /n = 108) and artificially hypermineralized (H / n = 116) . The group H received treatment for hypermineralization and eight teeth were randomly selected and observed by SEM to confirm the hypermineralization procedure. The teeth of each group were randomly divided into four different subgroups, according to the adhesive system used: Clearfil S3 Bond and Optibond All in One – One step- (Article 2 ); Clearfil SE Bond and AdheSE - Two steps - (Article 3). Each subgroup (n = 9) received different treatments: (1) conventional conditioning : application of the adhesive system according to the manufacturer’s recommendations, (2) conditioning of the dentin surface with Er,Cr:YSGG laser (Waterlase Millennium Biolaser Technology, San Clement, CA, USA) + adhesive system according to the recommendations of the manufacturer, (3) roughening of the dentin surface with a diamond tip 3098 + adhesive system according to the recommendations of the manufacturer. Then, cylindrical transparent molds were placed on the dentin surface treated with the adhesives and were filled with composite resin (Z350 XT FiltekTM - 3M ESPE) and light-cured for 40s. The molds were removed to expose the composite resin cylind...
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Panning, Nathan Joel. "Design of a laser doppler velocimeter for measurement of the relative linear velocity of rough surfaces." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/18357.
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Correia, Ricardo Rego Bordalo. "Estudo das bandas difusas do Na2 excitados por laser ultravioleta." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1988. http://hdl.handle.net/10183/149207.
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Neste trabalho foi feito um esforço para analisar o comportamento do perfil das bandas difusas violetas de emissão do dimero de sódio induzida por um laser de nitrogênio, no vapor de sódio produzido dentro de uma célula do tipo Heat-Pipe Oven, variando-se a temperatura e a pressão do gás inerte. Além disso, foi feita uma tentativa de identificação das bandas violetas e ultravioletas produzidas no mesmo sistema por um laser de excímero. Tanto para a emissão induzida pelo laser de nitrogênio, como pelo laser de excímero, um programa de computador desenvolvido por nós para simular estes espectros, a partir da teoria quase-estática para emissóes contínuas moleculares, utilizando as curvas de energia potencial interatômica disponíveis na literatura.In this work, an effort had been made to analyze the violet diffuse bands profile behavior from the induced sodium dimer emission by a nytrogen laser, in the sodium vapor produced inside a Heat-Pipe Oven, varying the temperature and the inert gas pressure. Furthermore had been made an attempt to identify the violet and ultraviolet diffuse bands produced on a similar sistem by an excimer one, a computer program was developed to simulate their emission profile based on the quasistatic theory for molecular continuous emission, using the available theoretical interatomic potencial energy curves.