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Lesparre, Fabien. "Amplificateurs impulsionnels à base de fibres cristallines dopées Ytterbium". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLO001/document.
Pełny tekst źródłaIn the last decade ultra-short pulse laser (< 10 ps) have sparked increasing interest for many industrial and scientific applications. Among the geometries used so far for high-power Yb-doped diode-pumped solid-state lasers as slabs, rods and thin disks, the single crystal fiber (SCF) technology was recently shown to have a high potential for the amplification of ultrashort pulses thanks to a very efficient thermal management and high optical efficiencies. This technology combined with the cubic crystal structure of Yb:YAG offers a cylindrical symmetry of the optical and thermo-mechanical properties. Yb:YAG SCFs are therefore well suited for the amplification of cylindrically polarized beams. In the context of a European Project called RAZIPOL, we have developed new laser amplifier architectures using SCF to directly amplify femtosecond pulses to achieve high energy and high average power pulses with radial and azimuthal polarizations without any stretching and recompression of the pulses.We first demonstrate a three-stage diode-pumped Yb:YAG single-crystal-fiber amplifier to generate femtosecond pulses at high average powers with linear or cylindrical (i.e., radial or azimuthal) polarization. At a repetition rate of 20 MHz, 750 fs pulses were obtained at an average power of 85 W in cylindrical polarization and at 100 W in linear polarization. Investigations on the use of Yb:YAG single-crystal fibers with different length/doping ratios and the zero-phonon pumping at a wavelength of 969 nm were conducted in order to optimize the performances of the amplifiers.The second part of the project is focused on pulse energy scaling. In this sense, we demonstrate a two-stage Yb:YAG single-crystal-fiber amplifier designed for high peak power to significantly increase the pulse energy of a low power picosecond laser. The first amplifier stage has been designed for high gain. Using a gain medium optimized in terms of doping concentration and length an optical gain of 32dB has been demonstrated. The second amplifier stage designed for high energy using divided pulse technique allows to generate recombined output pulse energy of 2mJ at 12.5 kHz with a pulse duration of 6 ps corresponding to a peak power 320MW. Average powers ranging from 25W to 55W with repetition rates varying from 12.5 kHz to 500 kHz have been demonstrated.This results has led to the publication of 2 articles in international peer-reviewed journals and have been presented in 7 conferences. Finally this work has inspired the launch of a new line of industrial products by Fibercryst
Cassard, Philippe. "Verrouillage par injection des lasers impulsionnels de grande puissance : le laser TEA CO₂". Paris 11, 1985. http://www.theses.fr/1985PA112338.
Pełny tekst źródłaThis thesis is directed at the study of injection-locking of high power pulsed lasers. Chapter I give a theoretical analysis of injection mode-locking in such lasers. A multimode theory is developed on the basis of the semi-classical treatment in the weak field regime. A detailed investigation of CW injection-locking is reported. It is clearly demonstrated that locking by injection of a weak field in a pulsed multimode laser stems from injection mode-locking whatever is the injection field time history. Thus the generation of short pulses by injection is described as well. Chapter II theoretically overviews the energetic features of the TEA CO₂ laser, with or without injection. Chapter III presents an experimental investigation of CW injection-locking in stable resonator TEA CO₂ lasers. Frequency measurements are performed with a new high frequency heterodyning scheme. The limits of CW injection locking are studied. Moreover, the influence of the transient discharge electron density on injection-locking is demonstrated. Chapter IV gives an experimental evidence of high order transverse mode injection-locking in unstable resonator TEA CO₂ lasers
Ouslimani, Hana. "Intégration de lasers impulsionnels monofréquences sur verre phosphate dopé ytterbium". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT100/document.
Pełny tekst źródłaVarious optical sensors, such as LIDARs, need laser sources both powerful and narrow-linewidth. In this context, the aim of this project is the realization of integrated pulsed laser sources with a Fourier Transform Limited (FTL) spectrum. To do so, we propose a passively Q-switched DFB laser structure. Ion-exchange technology is used to realize amplifier waveguides on Ytterbium-doped phosphate glass. The DFB cavity is made by dry etching of a Bragg grating on the waveguides surface. The Q-Switched behavior is obtained by depositing a BDN-doped cellulose acetate coating layer, acting as a saturable absorber. This structure allowed us obtaining FTL single-frequency pulsed lasers. When studying the impact of BDN concentration, we observe pulses ranging from 2,5 ns with 40 W peak power, to 100 ns with 14 W peak power. Thus, our device FWHM linewidth goes down to 9 MHz. These results pave the way for the realisation of compact laser sources for embedded lidar systems
Rotger, Maud. "Contribution à l'étude d'un laser Nd-YAG industriel de puissance : réalisation d'un lambdamètre pour lasers impulsionnels". Dijon, 1990. http://www.theses.fr/1990DIJOS013.
Pełny tekst źródłaOrtac, Bülend. "Développement d'un laser à fibre double-gaine dopée à l'ytterbium femtoseconde et caractérisation des régimes multi-impulsionnels". Rouen, 2004. http://www.theses.fr/2004ROUES031.
Pełny tekst źródłaThe work reported in this thesis is devoted to study and the realization of femtosecond ytterbium-doped double-clad fiber laser and characterisation of multiple pulsing regimes. The results obtained demonstrate that high power femtosecond fiber lasers with exceptional qualities in terms of the noise can be realized. In addition, the availability of high pump power with the V-groove technique enabled us to demonstration the richness and the diversity of multiple-pulsing operation
Pallas, Florent. "Etude théorique et expérimentale du fonctionnement bifréquence de microlasers continus et impulsionnels pour la génération d'ondes RF et THz". Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00877894.
Pełny tekst źródłaCarrer, Evelyne. "Etude des effets thermomécaniques induits sur les particules lors de la propagation dans l'atmosphère de faisceaux lasers impulsionnels". Aix-Marseille 2, 1986. http://www.theses.fr/1986AIX22009.
Pełny tekst źródłaLecourt, Jean-Bernard. "Etude et réalisation de lasers à fibre auto-impulsionnels àbase d'absorbants saturables". Phd thesis, Université de Rouen, 2006. http://tel.archives-ouvertes.fr/tel-00130694.
Pełny tekst źródłaDans une deuxième partie, nous avons réalisé une source laser fonctionnant en régime de verrouillage de modes. Notre laser s'articule autour d'une fibre erbium et d'un absorbant saturable ultra-rapide (~ ps) InGaAs/InP dopé Fer. Dans cette configuration un régime auto-démarrant d'impulsions de durée 700 fs a été démontré grâce à l'utilisation conjointe d'un absorbant saturable et d'effets de polarisation.
La troisième partie de ce travail de thèse a été consacrée à une autre structure non-linéaire ultra-rapide (500 fs) utilisée comme miroir de cavité. Nous avons obtenu des impulsions dont la durée est de 300 fs. Avec la même cavité, un absorbant saturable à base de nanotubes de carbone (NTC) nous a permis d'obtenir un régime de verrouillage de modes présentant une grande stabilité aussi bien en régime de dispersion anormale qu'en régime de dispersion normale. Les performances obtenues sont des impulsions d'énergies supérieures à 150 pJ avec des durées allant de 700 fs (régime anormal) jusqu'à quelques picosecondes (régime normal).
Enfin nous avons réalisé une source laser à fibre à haute énergie fonctionnant en régime déclenché grâce à un absorbant saturable semiconducteur GaAs. Le milieu à gain est une fibre double-gaine dopée ytterbium. Nous avons obtenus des impulsions énergétiques (7 µJ) d'une durée d'environ 1 µs. Ce régime est obtenu sur un domaine d'accord d'environ 30 nm autour de 1,07 µm en restant spatialement monomode.
Mager, Loic. "Correction de fronts d'onde de faisceaux lasers impulsionnels par mélange d'ondes photoréfractif". Phd thesis, Université Paris-Nord - Paris XIII, 1994. http://pastel.archives-ouvertes.fr/pastel-00716165.
Pełny tekst źródłaGiraud, Marie-Annick. "Propagation en atmosphère marine de rayonnements laser impulsionnels : application au cas de sources Nd:YAG à décalage Raman". Aix-Marseille 3, 1997. http://www.theses.fr/1997AIX30060.
Pełny tekst źródłaPatin, Benjamin. "Matériaux et Dispositifs optoélectroniques pour la génération et la détection de signaux THz impulsionnels par photocommutation à 1,55µm". Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00954635.
Pełny tekst źródłaKemiche, Malik. "Ingénierie de dispersion dans les cristaux photoniques pour la réalisation de micro-lasers compacts impulsionnels". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC022.
Pełny tekst źródłaWith the development of cloud computing and video streaming, the amount of data transmitted across the Internet has skyrocketed during the last decade. It now represents between 6 % and 10 % of the global energy consumption, and is expected to keep rising with the emergence of Internet of Things applications. However, the limits of the current infrastructure are already becoming apparent. Integrated photonics has brought new concepts to overcome the limitation of electronics such as all-optical signal processing or optical interconnects. In particular, silicon photonics has enabled the realisation of photonic integrated circuits able to perform these complex tasks on a chip and compete with their electronic counterparts. Moreover, integrated designs benefit from better robustness, stability and compactness as well as a reduced energy consumption. Integrated light sources have been developed to drive these photonic integrated circuits. Integrated mode-locked lasers are especially interesting since they provide both a regular pulse train and a stable mode comb. These lasers rely on the combination of a multimode laser and a saturable absorber to phase-lock the modes of the cavity. Despite some progress towards their integration on a chip, their size is still in the millimetre to the centimetre range. Since the quality of the generated pulse train is related to the effective length of the cavity, which is the product of the group index of the guided mode and the actual length of the cavity, their miniaturisation remains a challenge.In this PhD work, a novel design based on the use of slow-light (high ng) in photonic crystals to achieve further miniaturisation of integrated mode-locked lasers is studied. Indeed, slow light allows us to keep the effective length of the cavity high in a compact design with group indices one order of magnitude higher than in standard cavities. In order to reach mode-locking, a wide regular mode comb must be present in the cavity spectrum. Nonetheless, the strong dispersion of slow light modes in photonic crystals limits the spectral width of the regular mode comb. Using dispersion engineering, the bandwidth of the mode comb can be drastically improved. Photonic crystal cavities exploiting dispersion-engineered slow light in active III-V materials on silica were designed using numerical simulations, then fabricated and characterised to demonstrate the validity of this approach and study its potential limitations. We show that in spite of the effect of fabrication-induced disorder, regular mode combs can be generated in cavities as long as 45,5 µm with a group index around 30. These cavities may allow for an 8-fold size reduction of mode-locked lasers compared to standard waveguide designs. In the future, a saturable absorber such as graphene could be introduced onto the cavities in order to achieve mode-locking
Jaffres, Anael. "Matériaux laser dopés terres rares impulsionnels dans la gamme spectrale 1 um et 1.5 um: efforts sur la montée en puissance et en cadence". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://pastel.archives-ouvertes.fr/pastel-00973878.
Pełny tekst źródłaJaffres, Anaël. "Matériaux laser dopés terres rares impulsionnels dans la gamme spectrale 1 μm et 1,5 μm : efforts sur la montée en puissance et en cadence". Paris 6, 2013. http://www.theses.fr/2013PA066799.
Pełny tekst źródłaThis work is devoted to the study of diode-pumped rare-earth doped solid-state lasers emitting in the infrared spectral range: at 1 μm for high-power laser and ultra-short pulses and at 1,5 μm in the eye-safe domain. The first part of this work describes the study of two kinds of defects occurring in Yb:CALGO crystals: diffusing centres and colour centres. The non-stoechiometric compositions and the growth parameters we investigated do not eliminate the diffusing centers, whereas a solid solution Ca2+-Sr2+ does but presents another type of defects (bubbles). The colour centres are attributed to polaronic holes, which is confirmed by fitting the related absorption band. The study of codoped materials Yb3+, X4+:CALGO tends to show a positive effect of the tetravalent codopant on the decoloration. The second part studies Er, Yb codoped materials for eye-safe laser applications. After crystal growth of the selected Er, Yb codoped hosts (Ca2Al2SiO7, SrGdGa3O7, Y2SiO5, CaGdAlO4), thermal, spectroscopic and laser properties are evaluated. In CW regime, Er, Yb, Ce: CAS generates output power of 200-300 mW at 1555 nm. In Q-Switch regime, pulses of 1,4 mJ energy and 40 ns-duration are obtained in Er, Yb, Ce:CAS for the first time. Hence this crystal appears as a possible alternative to the commercial phosphate glass
Mekemeza, Ona Keshia. "Photonic spiking neuron network". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2023. http://www.theses.fr/2023UBFCD052.
Pełny tekst źródłaToday, neuromorphic networks play a crucial role in information processing,particularly as tasks become increasingly complex: voice recognition, dynamic image correlation, rapid multidimensional decision- making, data merging, behavioral optimization, etc... Neuromorphic networks come in several types; spiking networks are one of them. The latter's modus operandi is based on that of cortical neurons. As spiking networks are the most energy-efficient neuromorphic networks, they offer the greatest potential for scaling. Several demonstrations of artificial neurons have been conducted with electronic and more recently photonic circuits. The integration density of silicon photonics is an asset to create circuits that are complex enough to hopefully carry out a complete demonstration. Therefore, this thesis aims to exploit an architecture of a photonic spiking neural network based on Q-switched lasers integrated into silicon and an ultra-dense and reconfigurable interconnection circuit that can simulate synaptic weights. A complete modeling of the circuit is expected with a practical demonstration of an application in solving a mathematical problem to be defined
Chauvat, Dominique. "Innovation et optimisation d'une méthode de polarimétrie pompe-sonde avec des faisceaux laser impulsionnels en vue d'une mesure précise de violation de la parité dans l'atome de césium". Phd thesis, Université Paris Sud - Paris XI, 1997. http://tel.archives-ouvertes.fr/tel-00011914.
Pełny tekst źródłaCHAUVAT, DOMINIQUE. "Innovation et optimisation d'une methode de polarimetrie pompe-sonde avec des faisceaux laser impulsionnels en vue d'une mesure precise de violation de la parite dans l'atome de cesium". Paris 11, 1997. http://www.theses.fr/1997PA112257.
Pełny tekst źródłaHaboucha, Adil. "Interaction d'un grand nombre de solitons dans un laser à fibre : du "gaz" au "cristal" de solitons". Angers, 2008. http://www.theses.fr/2008ANGE0058.
Pełny tekst źródłaA passively mode-locked erbium doped fiber laser with dispersion-managed cavity exploiting the nonlinear polarization rotation was set up. The laser is operated in both anomalous and normal path-averaged dispersion regimes. When the pump power increase a large variety of pulse behavior is accessible : multistability and hysteresis phenomena ; phase transition of the multisolitons (evolution from a ‘gas' to a ‘crystal' of solitons) ; generation of a bound state of hundreds of pulses. . . Etc. We identify the spectral gain filtering as a mechanism of multiple pulse formation in the fiber laser operating in the normal dispersion regime. A correlation is theoretically established between the spectral gain bandwidth and the possibility for the laser to deliver several pulses by cavity round-trip: narrow spectrum favours multiple pulsing. We give a detailed theoretical analysis of spontaneous periodic pattern formation in fiber lasers. The pattern consists in a bound state of hundreds of pulses in a ring fiber laser passively mode- locked by nonlinear rotation of the polarization. The phenomenon is described theoretically using a multiscale approach to the gain dynamics: the fast evolution of a small excess of gain is responsible for the stabilization of a periodic pattern, while the slow evolution of the mean value of gain explains the finite length of the quasi-periodic soliton train. The resulting model is well adapted to the experimental observations in our Er:Yb doped double-clad fiber laser
Faïz, Radouan. "Commande optimale d'un laser impulsionnel chirurgical". Lille 1, 1992. http://www.theses.fr/1992LIL10112.
Pełny tekst źródłaA cet effet, un modèle mathématique a été développé. Il décrit l'évolution de la température. A partir de ce modèle «markovien», on a pu résoudre le problème de la commande optimale par application de la programmation dynamique. Celui-ci a pour avantage de fournir une commande optimale du laser en boucle fermée. En d'autres termes cet algorithme consiste à trouver, à tout instant, une commande optimale tenant compte d'une part, des perturbations liées à l'état du tissu et d'autre part, des contraintes imposées par le constructeur du laser. L'algorithme de commande optimale dépend des paramètres tissulaires. Une procédure d'adaptation paramétrique est associée à la loi de commande optimale afin de l'adapter aux changements des paramètres tissulaires qui surviennent pendant le traitement. La nouvelle loi de commande formée par la commande optimale et l'adaptation paramétrique constitue ce qu'on peut appeler la commande auto-ajustable. Cette loi de commande a fait ses preuves en simulation en montrant une excellente adaptabilité au problème
Haboucha, Adil. "INTERACTION D'UN GRAND NOMBRE DE SOLITONS DANS UN LASER A FIBRE : DU "GAZ" AU "CRISTAL" DE SOLITONS". Phd thesis, Université d'Angers, 2008. http://tel.archives-ouvertes.fr/tel-00429782.
Pełny tekst źródłaDUBOUCHET, CATHERINE. "Traitements thermomecaniques de surfaces metalliques a l'aide de lasers co#2 continus et de laser impulsionnel". Paris 11, 1993. http://www.theses.fr/1993PA112360.
Pełny tekst źródłaGirard, Karen. "Etude de la création de défauts volumiques générés pendant la solidification de soudures réalisées par faisceau laser Nd : YAG impulsionnel - application au soudage du tantale". Dijon, 1999. http://www.theses.fr/1999DIJOS067.
Pełny tekst źródłaCharton, Stephane. "Contribution à l'étude du contrôle en ligne des opérations de soudage par laser ND : Yag impulsionnel". Dijon, 1999. http://www.theses.fr/1999DIJOS047.
Pełny tekst źródłaLeclerc-Perron, Jérôme. "Laser à miroirs de Bragg à excitation impulsionnelle". Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26485.
Pełny tekst źródłaThe emergence of erbium doped glasses has allowed the development of many technologies. However, applications such as LIDAR, infrared spectroscopy and infrared sources for optical parametric oscillators all benefit from having a wide gain bandwidth farther in the infrared than what erbium doped glasses allow. Thulium has shown to be a good candidate for such applications due to its wide gain bandwidth ranging from 1.7 μm to 2.1 μm. Inspired by the success in laser pulse generation from erbium doped media, many researchers decided to apply the knowledge acquired from erbium doped laser sources to thulium doped laser sources. We chose to use a linear distributed Bragg reflector cavity, which allows us to implement a monolithic laser of a very small size. Depending on the pumping scheme, it is possible to operate this laser in a CW regime as well as in a pulsed regime. This document details the implementation of a thulium doped fiber laser in a linear cavity with distributed Bragg reflectors. We first develop the theoretical model used for the simulation of our laser’s dynamics. This model allows us to implement numerical simulations able to treat pulsed pumping, dispersive effects induced by the fiber Bragg grating and intrinsic nonlinear effects. We then characterize the erbium-ytterbium doped phosphate fiber amplifier used to generate pump pulses, along with the other components of the thulium doped fiber laser cavity. The numerical model is then validated by comparing numerical simulations to experimental results obtained from our thulium doped laser.
Le, Galès Germain. "Evaluation de la fiabilité de diodes Laser 1064nm en régime impulsionnel critique pour des applications "seed" de laser à fibre forte puissance". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0562.
Pełny tekst źródłaA growing number of Laser applications requires the use of pulsed sources with a large versatility in terms of duration, power and frequency of the generated Laser pulses. Such sources are based on the well-established “Master Optical Power Amplifier” architecture, and integrated into a large variety of optical amplification systems. Generally, it is composed of a “seed” diode, acting as a “source” oscillator, operated in pulse regime in order to produce optical pulses forwarded to an amplification stage (solid or fibered), doped with rare earth elements (ex. Ytterbium). However, the maximum output power delivered by such diodes barely reaches a few hundred mW. In order for the “MOPA” to produce output pulses with a peak power reaching a few tens of kW, it is necessary to design an amplification chain with a high optical gain but on the other hand susceptible to generate non-linear phenomena detrimental to the application. The use of commercialized and ultra-reliable single mode Laser diodes, operating in large overcurrent but under short pulse conditions (under 1μs), appears as an alternative solution, which, however, requires to be validated in terms of electro-optical characterizations as well as in terms of performances robustness under these critical conditions
Valla, Matthieu. "Etude d'un lidar doppler impulsionnel à laser Erbium fibré pour des mesures de champ de vent dans la couche limite de l'atmosphère". Paris, ENST, 2005. http://www.theses.fr/2005ENST0030.
Pełny tekst źródłaA PhD work has been undertaken for the realization of an impulse coherent laser anemometer for the measurement of wind field solved in distance in the lower atmosphere. During its propagation, the pulse gradually probe the atmosphere in the ascending direction. It is thus possible to realize a distance resolved velocity measurement by cutting out the analysis of the signal retrodiffused in multiple temporal windows. The originality of this PhD work is the use of a 1. 55 µm erbium fiber amplifier in a nanosecond pulsed mode, which allows the realization of compact and reliable instruments, with ocular safety. The instrumental simulator calculates the carrier to noise ratio of a mono or bistatic lidar, using configurations of truncated Gaussian beams with or without atmospheric turbulence. In order to account for atmospheric turbulence, the simulator uses a screen phase propagation code. The exact calculation of the Cramér-Rao lower bound allows us to predict the performances of the digital processing associated with the instrument. This part contains a fine model of the spectrum of the lidar signal which highlights a form of "spectral leakage" related to the decorrelation of the signal due to the pulsed nature of the instrument. He availability of a laser able of 20 µJ pulses allowed the realization of a prototype which was able to make three simultaneous measurements at distances up to 130 meters, thus giving us the opportunity to validate by the experiment the spectrum model undertaken during this PhD work
Faraud, Emeric. "Développement et applications de techniques laser impulsionnelles pour l'analyse de défaillance des circuits intégrés". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14677/document.
Pełny tekst źródłaThe fault location based on laser stimulation are now among the most advanced available techniques. They allow thermal or photoelectric stimulation localized without physical contact.This Ph.D works was devoted to the development and application of techniques using pulsed laser for integrated circuits’ analyses.Material development and investigation of analysis methodologies have been held by the motivation of the MADISON project (Methods of Analysis of Failures by Innovative Dynamic Optical Stimulation), which aims to increase the success rate analysis of complex circuits VLSI by laser stimulation.We used high-performance optical systems including fibered pulsed laser sources to explore the capabilities in terms of analysis by photoelectric laser stimulation. An original study of the Latchup phenomenon showed an improving lateral resolution by using nonlinear absorption process
DEVAUX, DAVID. "Caracterisation des plasmas formes par laser impulsionnel en geometrie confinee. Application au choc laser". Paris 11, 1993. http://www.theses.fr/1993PA112323.
Pełny tekst źródłaRoy, Vincent. "Lasers à fibre à synchronisation modale passive par rotation non linéaire de la polarisation : dynamique en régime multi-impulsionnel". Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24719/24719.pdf.
Pełny tekst źródłaThe work presented herein is primarily concerned with the dynamics of passively mode-locked fiber lasers. The mechanism used for achieving pulse emission relies on nonlinear interferometry (i.e. nonlinear polarization rotation). However, the same mechanism acts as a limiter whenever the pulse power is increased above a given amount, i.e. the wings are subject to a higher gain than the peak of the pulse. The pulse train then becomes unstable and the creation of one or more additional pulses follows from this instability. In this new regime, it is not unusual to observe the formation of coherent states of bound pulses. The nature of the interaction responsible for this phenomenon depends on the amount of dispersion experienced by the pulses along the laser cavity. In the case of a cavity that sustains the formation of solitons, the occurrence of pulse bound states was shown to result from the nonlinear interaction between the pulses and the resonant dispersive waves emitted as a result of the periodic perturbations the solitons undergo on successive cavity round trips. In contrast, for the case of a cavity built from positive and negative dispersion fibers such as to reduce the net dispersion, the sidebands related to the resonant dispersive waves are greatly reduced because of the significant frequency chirp the pulses acquire along each fiber segment. Thus we show here that the formation of pulse bound states results instead from the direct interaction between the multiple pulses since the pulses interfere with one another on a significant part of the laser cavity. In addition, in the same regime, we report the observation of collisions occurring between pulse bound states traveling with different group velocities. This process may result in several outcomes, depending on the changes the bound states undergo during the collisions. In fact, energy and momentum need not be conserved in the process since the laser is a dissipative system. Finally, in the case of collisions that repeat periodically, the acquisition of a sequence of autocorrelations allowed us to verify the peculiar dynamics that characterizes the collision process.
Dupont, Arnaud. "Ablation de couches superficielles de matériaux métalliques par rayonnement laser impulsionnel". Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX22064.
Pełny tekst źródłaGuignard, Celine. "Réalisation de sources impulsionnelles pour les télécommunications". Phd thesis, Université Rennes 1, 2005. http://tel.archives-ouvertes.fr/tel-00260197.
Pełny tekst źródłaDILLEMANN, BENOIT. "Comportement dynamique du dioxyde de vanadium sous illumination laser impulsionnelle". Paris 7, 1995. http://www.theses.fr/1995PA077271.
Pełny tekst źródłaZeng, Lei. "Etude théorique et expérimentale de µ-OLEDs en régime impulsionnel à très haute densité de courant". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCD066.
Pełny tekst źródłaThis thesis focus on the estimation of the possibility to achieve the laser threshold in an organic material with electrical pumping. As the ultimate goal is to demonstrate an electrically pumped organic laser, attaining high current density in a working electroluminescent device is pre-required. At first, the response of OLED at high current injection condition is simulated with a theoretical model. And the laser threshold estimation is performed by transfer matrix method. These theoretical studies show that a peak of emissive exciton (singlet) population density should exist at pulse onset, while a population density of 8.7×1016 cm-3 is necessary for lasing. Next, the time-resolved characteristics of μ-OLED based on Alq3 : DCM excited by short (< 100 ns) electrical pulses with low repetition rate (10 Hz) have been studied on the calibrated confocal microscope. The response of μ-OLED is in good agreement with the theoretical simulations. A current density of 3.6 kA/cm² and a luminance peak of 8.4×106 cd/m² have been achieved with 30-ns pulses. This luminance peak corresponds to singlet population density of 3.6×1017 cm-3, which is higher than the smallest laser threshold in literature. We suggest that it is possible to achieve laser effect in the time window of several nanoseconds at pulse onset
Akmansoy, Eric. "Verrouillage par injection des lasers impulsionnels TEA CO₂ : résonateurs stables et instables". Paris 11, 1988. http://www.theses.fr/1988PA112235.
Pełny tekst źródłaThis thesis is divided into three parts. The first part gives the theorical elements of the study respectively related to i) The kinetics C0₂ amplifier medium. Ii) The description of resonator modes. Iii) The CW injection of pulsed lasers. In the second part are reported the realization of a 1-10 J TEA C0₂ laser, its optical and electrical characterization, the injection-locking results for varions configurations and their comparison with theory. As the major point, the performance of stable- and unstable resonator TEA C0₂ lasers are compared in the case of CW single-mode injection. The heterodyne detection of the pulses allows to measure the main characteristics of single-mode injection-locking : the locking band-width and the minimum injection intensity. Other injection schemes are considered. I) The CW single mode injection in a ring resonator. Ii) The two transverse mode injection in a laser with an unstable resonator. The third part of the thesis is a detailed study of intra-pulse frequency variations and the refractive index effects in the amplifier medium. In the course of this work, new performances have been obtained of great interest for LIDAR applications. Lt is the first time that 5 μS 1 J single longitudinal mode pulses are obtained at 10 μm with unstable resonator lasers for injected powers as low as 200nW. Lt is also demonstrated that the frequency chirping can be considerably reduced. Finally it is the first time that two longitudinal mode operation of a high energy laser is controlled with the injection of a weak signal into the laser cavity
Bussière, Benoît. "Etude des mécanismes d'endommagement par laser impulsionnel des cristaux de saphir dopé titane". Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22070/document.
Pełny tekst źródłaThe use of large Ti:Sapphire crystals in ultra fast high peak power laser amplifiers makes crucial the problem of crystal laser induced damage. These works aim to qualify the laser induced damage threshold of Ti:Sapphire crystals under femtosecond, picosecond and nanosecond laser pulse irradiations, which are typically encountered in such laser chains and representative of laser matter interaction regimes. Furthermore, the influence of parameters peculiar to Ti:Sapphire crystals use in laser systems, such a cryogenic conditions, anti-relection coatings, or optical pumping kind (temporally monomode or multimode pulses), has been performed. The results are important to understand the mechanisms leading to the damage, and to reveal the key parameters which will have to be optimized in future high peak power laser chains
Mager, Loïc. "Correction de fronts d'onde de faisceaux lasers impulsionnels par melange d'ondes photorefractif". Paris 11, 1994. http://www.theses.fr/1994PA112354.
Pełny tekst źródłaAkmansoy, Eric. "Verrouillage par injection des lasers impulsionnels CO TEA résonateur stable et instable /". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37611137f.
Pełny tekst źródłaGlachet, Michel. "Etudes théoriques et expérimentales des phénomènes d'initiation d'une chaîne pyrotechnique par laser impulsionnel". Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX22039.
Pełny tekst źródłaGrojo, David. "Mécanismes d'enlèvement de particules par laser impulsionnel : application au nettoyage pour la microélectronique". Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2006. http://tel.archives-ouvertes.fr/tel-00118348.
Pełny tekst źródłaLecourt, Jean-Bernard. "Etude et réalisation de lasers à fibre auto-impulsionnels à base d’absorbants saturables". Rouen, 2006. http://www.theses.fr/2006ROUES035.
Pełny tekst źródłaThis work deals with the impulsionnal fiber laser development. The first part of this thesis consists in the study and the realization of erbium-doped fibre laser passively Q-switched by iron-doped InGaAs/InP multiple quantum well semiconductor saturable absorber. Moreover simple modelling based on the rate equations has been developed and allows the understanding of the main output characteristics of our laser such as the shape of the pulse. Then, we realize a passively mode-locked fibre laser. The amplifyer medium is an erbium-doped fibre and the ultrafast saturable absorber is a iron-doped InGaAs/InP multiple quantum wells structure. In this configuration, self-starting mode-locking is obtained. 700 fs pulses are measured with both saturable absorber and polarization effects. In the third part of this study, we use ultra-fast saturable absorber (500 fs) as a cavity end-mirror. 300 fs optical pulses are obtained. With the same cavity, Saturable Absorber Incorporating NanoTubes (SAINT) can self-start stable mode-locking whatever the dispersion of the cavity (soliton or Stretched-pulse regime). More than 150 pJ pulse energy is obtained and the pulse duration is included between 700 fs (soliton) and few picoseconds (stretched pulse). Finally we have realized a high-energy fibre laser Q-switched by semiconductor saturable absorber GaAs. The amplifyer medium is a double-clad ytterbium-doped fibre. We obtain optical pulses of several micro-joules (7 µJ) with duration of 1 µs. The laser can be tuned over 30 nm around the central wavelength (1,07 µm)
Totems, Julien. "Emission laser impulsionnelle et traitements temps-fréquence en vibrométrie par lidar à détection cohérente". Phd thesis, Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00610531.
Pełny tekst źródłaAstic, Dominique. "Caractérisation par spectroscopie d'émission d'un plasma créé par laser CO2 impulsionnel sur matériaux solides". Aix-Marseille 2, 1990. http://www.theses.fr/1990AIX22052.
Pełny tekst źródłaGhrab, Mounir. "Caractérisation de jets de plasmas créés par laser à CO2 impulsionnel sur matériaux solides". Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX22075.
Pełny tekst źródłaBournazel, Manon. "Dynamique collisionnelle sondée par alignement moléculaire post-impulsionnel". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK011.
Pełny tekst źródłaOver the past thirty years, the development of ultra-short laser sources has accelerated the research on the control of molecular rotational motions by molecular alignment. For field free molecular alignment, when the pulse duration of the laser is shorter than the rotationnal period of the molecule, a periodic reccurence of revivals follows the excitation by the laser pulse. These molecules, interacting with their environment, undergo internal collisions that attenuate the amplitude of these revivals over time. Studying the disappearance of this molecular alignment over time or pressure provides insights into the relaxation of coherences and rotational populations.In this thesis, we investigate the collisional dynamics of various systems, probed through molecular alignment or rotational echoes. First we observe nonsecular and non-Markovian effects in the temporal domain at short timescales. Rotationnal echoes are then used to improve the alignment of acetone which is highly asymmetric and hence challenging to align. In addition, to overcome the dependence of echo amplitude on the delay between the two laser pulses and the intensity of the second pulse, we introduce a new technique involving a spatial light modulator and a learning algorithm to create a bi-pulse. The optimal parameters of the bi-pulse are automatically adjusted to maintain the echo amplitude constant
Reineix, Gwenaël. "Conception de sources optoélectroniques transitoires à formes d'ondes maitrisées". Thesis, Limoges, 2020. http://aurore.unilim.fr/theses/nxfile/default/60bc610a-86d7-4b9d-b388-b0ea4256778e/blobholder:0/2020LIMO0011.pdf.
Pełny tekst źródłaThe work developed in this thesis focuses on two main applications : the generation of signals dedicated to electromagnetic susceptibility tests and the shaping of transient signals applied to spectral shaping for impulse radars. For susceptibility tests, damped sinusoidal signals of a few kilovolts, with frequencies ranging from 20 MHz to 200 MHz, with quality factors between 8 and 12 are considered. In the case of spectral shaping, the generation of several transient signals makes it possible to reproduce an ultrawideband spectrum (300 MHz - 3 GHz) on which frequencies considered undesirable have been rejected.To form the signals useful for these two applications, innovative optoelectronic generators have been developed, the triggering of the signals being controlled by the illumination of photoconductors. The use of photoconductors illuminated by a laser beam generates short pulses (from a few nanoseconds to several hundred nanoseconds) of high voltage (a few kilovolts) with a very low jitter (a few picoseconds).This technique makes it possible to use multiple sources whose signals can be synchronized with each other. A study of the functioning and characterization of photoconductors has been carried out for the optimization of the optoelectronic generators developed. For each application, the designed experimental system is presented
Bouyge, David. "Systèmes lasers impulsionnels compacts et dispositifs hyperfréquences accordables basés sur l'intégration de composants MEMS". Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/ac1d8e2a-01a5-4522-a2a7-f571790878dc/blobholder:0/2007LIMO4054.pdf.
Pełny tekst źródłaIn spite of the large interest provoked by the integration of Micro-Opto-Electro-Mechanical-System (MOEMS) in optic systems, not enough experimentation concerning their capacity to produce short optic impulsions is developed. It is therefore in this direction that we orientated our jobs. First, this manuscript raises the state of art on MOEMS micro-mirrors and then introduces various kinds of pulsed laser systems regimes. The development of MOEMS is displayed across stages of conception, optimization of technology and characterization. We demonstrate a simple technique to produce active Q-switching in various types of fiber amplifiers by active integration MOEMS. We present the realization of a multiwavelength laser system which exploits the achromaticity of micro-mirrors for the generation of tunable radiations in the visible spectre. Finally, we study the development of tunable multipole reject band filters
Montagne, Jean-Eucher. "Laser à exciplexes KrF impulsionnel de grande énergie : effets du rayonnement ultra-violet sur matériaux". Aix-Marseille 2, 1992. http://www.theses.fr/1992AIX22099.
Pełny tekst źródłaAuroux, Sandrine. "Exploration de nouvelles architectures lasers à émetteurs multiples et à verrouillage passif des phases pour le régime impulsionnel déclenché". Limoges, 2011. http://aurore.unilim.fr/theses/nxfile/default/61df3ffe-eff6-44a4-9643-cd163f701184/blobholder:0/2011LIMO4054.pdf.
Pełny tekst źródłaLaser beam combining appears as a solution to overcome the power limitations of a single laser. Two methods of laser coherent combining in a passive way have been explored in this thesis. Their potential for achieving a bulk configuration with multiple emitters operating in pulsed regime was studied. With these two methods, the emitted radiations are superposed only in the far field. The first configuration explored is laser combining by mutual injection. A fraction of the radiation from one laser seeds the neighboring resonator. Laser emissions are thus coupled step by step. Coherence properties of the emissions of lasers coupled by mutual injection have been studied numerically and experimentally. The second method is based on a multi-arm resonator of interferometric configuration. The different emitters self-adjust their relative phases to maximize the energy on the common path of the interferometric cavity. Spectral and spatial properties of emissions are considered experimentally and numerically. Numerical models have been developed for larger number of combined lasers. The last part deals with deterioration of output beams quality under high pumping level and the consequences on combining efficiency
Rivet, Sylvain. "Caractérisation complète d'un faisceau laser impulsionnel femtoseconde : mise en évidence et analyse du couplage spatio-temporel dans la propagation linéaire et non linéaire". Bordeaux 1, 2001. http://www.theses.fr/2001BOR12448.
Pełny tekst źródłaCanat, Guillaume. "Conception et réalisation d'une source impulsionnelle à fibre dopée Erbium-Ytterbium millijoule de grande brillance spectrale". Phd thesis, Ecole nationale superieure de l'aeronautique et de l'espace, 2006. http://tel.archives-ouvertes.fr/tel-00150684.
Pełny tekst źródłaLa dynamique des sources impulsionnelles générant des impulsions nanosecondes à microsecondes a été analysée dans la première partie de cette étude. L'influence des réflexions parasites aux faibles taux de répétition (quelques kilohertz) a notamment été mise en évidence. Les effets thermiques dans les lasers Erbium-Ytterbium à forte puissance de pompe ont également été étudiés. Lorsque l'intensité transportée devient suffisamment importante, l'effet non-linéaire
dominant, la Diffusion Brillouin Stimulée (DBS) limite la puissance extractible des amplificateurs.
Nous avons donc développé dans un deuxième temps un modèle original qui rend compte de la dynamique de la DBS dans les amplificateurs dopés. Le caractère guidé des ondes acoustiques qui interviennent a été pris en compte. Un modèle satisfaisant des modes longitudinaux acoustiques a été introduit. Afin d'élever le seuil de la DBS, des fibres amplificatrices faiblement multimodes peuvent être utilisées. Un compromis entre qualité spatiale et puissance crête transportable doit alors être
trouvé. Grâce à nos modèles, nous avons conçu une source impulsionnelle multi-étages qui a permis
d'atteindre 650 µJ pour des impulsions de l'ordre de la microseconde avec une qualité de faisceau caractérisée par un M2~2.