Дисертації з теми "Diffusion Brillouin stimulée"
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Masson-Laborde, Paul-Edouard. "Modélisation réaliste de l'instabilité de diffusion brillouin stimulée." Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00001913.
Mihelic, François. "Diffusion Brillouin stimulée dans les fibres optiques : amplification Brillouin large bande et laser Brillouin." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10146/document.
As part of this thesis several studies will be presented. The first presentes the problem of preservation of information in a Brillouin amplification process. The second focuses on the achievement of a Brillouin amplifier with a broad bandwidth. The last part concerns the achievement of Brillouin lasers of high coherence. An experimental study of the transition between Brillouin generator and Brillouin amplifier in a state of saturation is performed. It highlights the transfer of energy from the generator to the probe. We have proven that even in a regime of powerful generator, the spectral qualities of the probe are preserved when the resonance is reached. The qualities of the Brillouin amplifier lead us in a second part to try to increase its bandwidth as narrow band gain is a limitation for many applications, especially in the field of telecommunications. We explore the possibility of working with a large-band pump to achieve broad band amplification. We prove a bandwidth above 10 GHz. We demonstrate a monomode laser, with a spectral width below one kHz, stable in frequency and intensity, in which the threshold is reached by commercial DFB laser diodes. The set-up is compact, robust and cost effective. The cavity can also be used separately, ie without pump assigned, to applications of spectral narrowing or filtering. Finally, the application of the device to spectral characterization of coherent lasers is proved and discussed
Mihelic, François. "Diffusion Brillouin stimulée dans les fibres optiques : amplification Brillouin large bande et laser Brillouin." Electronic Thesis or Diss., Lille 1, 2008. http://www.theses.fr/2008LIL10146.
As part of this thesis several studies will be presented. The first presentes the problem of preservation of information in a Brillouin amplification process. The second focuses on the achievement of a Brillouin amplifier with a broad bandwidth. The last part concerns the achievement of Brillouin lasers of high coherence. An experimental study of the transition between Brillouin generator and Brillouin amplifier in a state of saturation is performed. It highlights the transfer of energy from the generator to the probe. We have proven that even in a regime of powerful generator, the spectral qualities of the probe are preserved when the resonance is reached. The qualities of the Brillouin amplifier lead us in a second part to try to increase its bandwidth as narrow band gain is a limitation for many applications, especially in the field of telecommunications. We explore the possibility of working with a large-band pump to achieve broad band amplification. We prove a bandwidth above 10 GHz. We demonstrate a monomode laser, with a spectral width below one kHz, stable in frequency and intensity, in which the threshold is reached by commercial DFB laser diodes. The set-up is compact, robust and cost effective. The cavity can also be used separately, ie without pump assigned, to applications of spectral narrowing or filtering. Finally, the application of the device to spectral characterization of coherent lasers is proved and discussed
Picholle, Éric. "Dynamique de la diffusion brillouin stimulee dans les fibres optiques." Nice, 1991. https://hal.archives-ouvertes.fr/tel-01424930.
Küng, Alain. "L'émission laser par diffusion Brillouin stimulée dans les fibres optiques /." [S.l.] : [s.n.], 1997. http://library.epfl.ch/theses/?nr=1740.
Saïd, Hussein. "Etude asymptotique d'un systeme semi-lineaire modelisant la diffusion brillouin stimulee." Paris 11, 1990. http://www.theses.fr/1990PA112385.
Neuville, Cedric. "Etude expérimentale des effets multi-faisceaux sur l'instabilité de diffusion Brillouin stimulée." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX046/document.
The laser facilities designed to realize laser inertial confinement thermonuclear fusion experiments use numerous laser beams in order to meet irradiation symmetry constraints and to deposite enough energy in matter. Unfortunately, the crossing of laser beams in plasmas modifies their propagations. When a beam is propagating in plasmas, it can interact with ion acoustic waves and scatter its energy by stimulated Brillouin scattering. Not only the directions but also the levels of these scatterings are modified when beams are crossing one another in plasmas. This manuscript is about the experimental study of two kinds of multiple-beam modification:- the flexibility of the LULI2000 laser facility (Laboratoire d'Utilisation de Lasers Intenses, Palaiseau, France) enabled us to study crossed-beam energy transfer between two and three beams;- the sixty laser beams available on the OMEGA facility (Laboratory for Laser Energetics, Rochester, United-States) enabled us to observe scattering of collective Brillouin instabilities produced in planar geometries and at the entrance hole of cavities of fusion experiments.These two mecanisms can highly modify the initial laser irradiation by transferring up to 30% of the laser energy between beams and by scattering more than 10% of the laser energy in unusual directions
Steinhausser, Bastien. "Laser à fibre multimode avec remise en forme de faisceau par diffusion Brillouin stimulée." Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00864743.
Lewis, Kévin. "Etude expérimentale et numérique de la distribution d'intensité laser dans un plasma et de son infkuence sur la diffusion Brillouin stimulée." Palaiseau, Ecole polytechnique, 2008. http://www.theses.fr/2008EPXX0060.
Le, FLoch Sébastien. "Étude de la diffusion Brillouin stimulée dans les fibres optiques monomodes standard : application aux capteurs de température et de pression." Brest, 2001. https://tel.archives-ouvertes.fr/tel-00008526.
Mauger, Sarah. "Couplage entre auto-focalisation et diffusion Brillouin stimulée pour une impulsion laser nanoseconde dans la silice." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00638962.
Le, Floch Sébastien. "Etude de la diffusion Brillouin stimulée dans les fibres monomodes standard. Application aux capteurs de température et de pression." Phd thesis, Université de Bretagne occidentale - Brest, 2001. http://tel.archives-ouvertes.fr/tel-00008526.
Stepien, Lionel. "Diffusion Brillouin stimulée dans les fibres optiques : bruit d'intensité du laser et brûlage de trou spectral dans le générateur et l'amplificateur." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2002. http://tel.archives-ouvertes.fr/tel-00002296.
Agaisse, Romain. "Auto-affinement spectral laser assisté par effet Brillouin." Electronic Thesis or Diss., Université de Rennes (2023-....), 2023. http://www.theses.fr/2023URENS091.
The frequency stability of lasers is a sought-after property in many fields such as optical communications, spectroscopy and time-frequency metrology. In this context, the Foton Institute has developed a principle making it possible to spectrally self-narrow a laser at extremely low levels. For this we pump a non-reciprocal Brillouin resonator which generates a spectrally pure Stokes wave. The addition of a phase-locked loop which counter-reacts to the pump then makes it possible to avoid mode hops of the Brillouin resonator while spectrally narrowing the pump laser, thus producing a cascaded self-narrowing effect. In this manuscript, we theoretically and experimentally study the Brillouin assisted laser spectral self-narrowing system. The modeling of all of its constituents using the formalism of transfer functions is supported by experimental validations. These transfer functions account for the response of the different elements of the system to phase and amplitude fluctuations. The expression of the transfer function of the complete system is then validated experimentally by comparing the theoretical predictions to the open-loop transfer function measurements as well as in step response. Exploitation of the model and its adjustable physical parameters then makes it possible to further reduce frequency fluctuations for a solid-state pump laser emitting at 1.54 μm. This allows us in particular to highlight the fact that the Brillouin resonator in these phase-locking conditions plays the role of an optical reference. The performance of the system is then evaluated by duplicating it and measuring the beat between the two independent systems in the microwave domain. Finally, the “buffer reservoir” principle is added to the spectral narrowing system. This principle based on the insertion of a non-linear absorption mechanism in the pump laser makes it possible to reduce excess amplitude noise at relaxation oscillations by 32 dB. This eliminates the main source of amplitude noise converted into phase noise in the system
Lewis, Kevin. "Etude expérimentale et numérique de la distribution d'intensité laser dans un plasma, et de son influence sur la diffusion Brillouin stimulée." Phd thesis, Ecole Polytechnique X, 2008. http://tel.archives-ouvertes.fr/tel-00387125.
Nous étudions la modification de la distribution d'intensité laser au cours du temps, et en différents plans de propagation, à partir de l'imagerie résolue en temps et en espace de cette distribution d'intensité, en champ proche et en champ lointain.
Nous présentons notamment la première observation expérimentale de l'instabilité de filament, l'éclatement du faisceau fonction du temps, de l'espace, du gradient de vitesse.
Nous donnons enfin la première et unique observation d'images de la localisation transverse de la rétrodiffusion Brillouin stimulée.
Fresnel, Schadrac. "Lasers à fibre Brillouin multi-stokes : cohérence et caractérisation en bruit." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S032/document.
Brillouin scattering is the inelastic scattering of light by the acoustic waves of a medium. In an optical fiber, stimulated Brillouin scattering occurs, from a certain incident light intensity (pump), for generating a backscattered "Stokes" wave, whose frequency is shifted from that of the pump by a value directly proportional to the acoustic wave propagation velocity in the fiber. The Brillouin shift has a high sensitivity to all effects that can change the speed of the acoustic wave. This property makes it possible to study the composition of the fibers and gives to the SBS the potential for the production of optical fiber sensors. The SBS process is also accompanied by a gain for the backscattered Stokes wave since almost all the power of the Pump wave is transferred there. It can, therefore, be used for the production of optical fiber amplifiers and lasers. As part of this thesis work, we experimentally studied static and dynamic properties of the Brillouin fiber lasers (BFLs). Depending on the damping rate of the acoustic wave and the loss rate of the cavity, the BFL can be very coherent and less noisy, thus promoting its use in multiple fields such as defense, metrology, and telecommunications. When the Pump makes only one turn in the Brillouin cavity, the studied BFL has a frequency noise 10,000 times lower than that of the Pump laser while keeping a similar intensity noise. When the Pump is resonant, it is possible to obtain a BFL with multiple Stokes waves by cascading the Brillouin non-linear effect in the optical fiber. Restricted by our measurement benches, we measured a frequency noise 1000 times lower than that of the Pump and an intensity noise more than 100 times lower
Sebastian, Ananthu. "Noise dynamics in multi-Stokes Brillouin laser." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S068.
Stimulated Brillouin Scattering (SBS) is a coherent interaction process in which light is scattered from optically generated acoustic waves. It is a powerful tool for microwave and optical signal processing, distributed sensing and spectroscopy. Brillouin lasers are attracting a lot of interest for their ability to produce ultra coherent linewidths. This thesis is devoted to the understanding of noise properties of Brillouin fiber ring lasers, operating with multiple Stokes orders. First, we present a technique based on the cavity ring-down method, which allows to characterize the Brillouin gain coefficient directly from probing the laser cavity. Its advantages are to obtain parameters from a single experiment with low optical powers (some 10 milliwatts) for short cavities (a few meters long, or integrated cavities). Secondly, it is shown that an intrinsic linewidth of a few tens of mHz can be easily obtained by cascading two non-resonant Brillouin lasers (for which the pump performs a single pass inside the cavity). In order to obtain these results, the long-term stability has been improved by using a Pound-Drever-Hall servo loop, which allows us to compare our analytical and experimental results. Unfortunately, we were unable to explore the fundamental limits of noise reduction due to the noise floor of our bench. Thirdly, one of the major works of this thesis is the theoretical and experimental study of the noise properties, including frequency noise and relative intensity noise, of a resonant Brillouin laser (for which pump and Stokes waves are resonant inside the cavity). In particular, the impacts of the fiber-ring-cavity quality factor, Brillouin gain detuning, are evaluated very precisely on the laser RIN features such as amplitude noise reduction and relaxation frequency. We emphasize the fact that many characteristics of the frequency noise are related to the RIN properties by a coupling between intensity and phase. We show that the cascade process modifies the dynamics of the Brillouin laser when compared to those of a single-mode Brillouin laser with a single first-order Stokes component. Our experimental results are in excellent agreement with our numerical simulations, obtained thanks to our non-linear system describing the operation of a multi-Stokes Brillouin laser. This good match is mainly due to our ability: to obtain very precise values of the cavity parameters and the Brillouin gain coefficient using the CRDM technique ; to achieve long-term stability (hours); to finely control the detuning between the laser Stokes resonance and the frequency of the Brillouin gain maximum. We demonstrate experimentally for the first time that frequency noise is degraded in the presence of anti-Stokes Brillouin scattering. We also show that a gain detuning of the order of a few hundred kHz can degrade the intensity noise reduction or also increase the linewidth by amplitude-phase coupling. All these very fine observations thus allow us to set the fundamental limits of such laser systems such as: the increase in noise due to anti-Stokes orders; the role of pump noise and its possible interrelation with cavity finesse; the effect of the detuning inherent to higher Stokes orders. All these conclusions are key to the design and engineering of these Brillouin fiber lasers, which are currently attracting a great deal of interest as evidenced by the work in progress in the scientific community. This PhD thesis contributes to a better understanding of multi-Stokes Brillouin lasers
Lombard, Laurent. "Méthodes non linéaires de remise en forme de faisceau pour amplificateur de puissance à fibre multimode." Paris 11, 2005. https://pastel.archives-ouvertes.fr/tel-00160884.
The recent development of quasi-singlemode large mode area fibers has led to a quick rise in fiber laser power. Indeed, the large core prevents nonlinear effects and increases damage threshold. In order to further increase the core diameter, we propose an alternative approach using a very large core multimode fiber amplifier followed by a nonlinear beam cleanup interaction to restore a diffraction limited beam profile. Two concepts have been studied:- in the first one the beam quality is restored by two-wave mixing in a Rh:BaTiO3 photorefractive crystal. An original scheme has been proposed and experimentally validated. This mode converter can change any depolarized, aberrated and coherent laser beam into a diffraction-limited beam,- the second one is a result of a detailed theoretical and experimental study of stimulated Brillouin backscattering (SBS) in multimode fibers. It is well known that both phase conjugation and beam cleanup behavior are observed by SBS in multimode fibers, but the reasons why each effect occur are not clear. The study defines the conditions in which phase conjugation (short step index fibers) or beam cleanup (gradient index fibers) are more likely to occur. An original geometry has been proposed and experimentally demonstrated. We obtain efficient and highly stable beam cleanup in a multimode gradient index fiber by using a self-aligned loop geometry. Beam cleanup is achieved by efficient reflection of the multimode beam to the fundamental gradient index fiber mode
Yahia, Vincent. "Etude expérimentale de la modification des instabilités paramétriques en plasmas multiples." Phd thesis, Ecole Polytechnique X, 2014. http://pastel.archives-ouvertes.fr/pastel-01057855.
Duluc, Maxime. "Étude des propriétés statistiques d'une tache focale laser lissée et de leur influence sur la rétrodiffusion brillouin stimulée." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0118/document.
In the context of inertial confinement fusion (ICF), optical smoothing is a technique used to obtain the most homogeneous laser irradiation possible, by modifying the temporal and spatial coherence properties of the laser beams. The use of optical smoothing is a necessity on high-power lasers such as the Laser Mégajoule (LMJ) to limit the development of parametric instabilities resulting from laser-plasma interaction, and among them, stimulated Brillouin backscattering (SBS). These instabilities lead to target irradiation defects and can also be a source of damage in the optical lines. However, these techniques can lead to other problems in the laser lines, such as the conversion of phase modulation to amplitude modulation (FM-to-AM), which is harmful to the proper conduct of the experiments and can also damage the laser optics.It is therefore a necessity to find a compromise around optical smoothing. The evolution of the smoothing compromise is however complicated because the quantification of gains and losses is very difficult to establish. Thus, as long as quantification is not done, the compromise does not evolve: the laserist always wants less smoothing and the experimentalist always more smoothing, but neither of them can bring enough quantitative elements to tip the balance. This thesis therefore proposes to lay the first groundwork for reaching this compromise for the LMJ, using theoretical and numerical studies.We carefully compare longitudinal (LSSD) and transverse (TSSD) smoothing by spectral dispersion in an ideal smoothing configuration for each case. With 3D codes, we simulated SBS in a gold plasma, typical of ICF experiments and favourable to the development of SBS. We show that, contrary to popular belief, the temporal evolution of SBS shows some differences between the two smoothing schemes. First, the asymptotic values of saturation levels are not quite the same. With a simple description using light rays and the calculation of the SBS gain for each ray, we were able to explain this difference. In addition, the dynamics of SBS are also somewhat different. We have shown that the SBS dynamics is determined by the temporal evolution of the properties of the hot-spots and in particular by the effective interaction length between the Brillouin backscattered light and the hot-spots. This effective interaction length depends on both the longitudinal velocity and the length of the hot-spots. Indeed, the synchronization of the effective interaction lengths of the two smoothing schemes also synchronizes the growth of the backscatter curves before saturation.We also show that it is possible to change the smoothing parameters of the LMJ by illustrating a new way to reduce the FM-to-AM conversion inevitably present in high-power lasers. By splitting the total spectrum usually used by a quadruplet (grouping of 4 beams) into two parts of smaller identical spectra on the left and right beams, the FM-to-AM conversion is significantly reduced from 30% to 5% while maintaining the smoothing performance for SBS. We have also shown that the resulting coherence time of the laser has no effect on the maximum level of SBS achieved. Similarly, the impact of these developments on other instabilities such as stimulated Raman scattering or crossed beam energy transfer will also need to be investigated
Carminati, François-Régis. "Étude expérimentale des phénomènes de transport dans les réseaux optiques d'atomes froids." Paris 6, 2002. https://tel.archives-ouvertes.fr/tel-00001556.
Sanchez-Palencia, Laurent. "ETUDE THEORIQUE DE LA DYNAMIQUE NON LINEAIRE D'ATOMES FROIDS DANS UN RESEAU OPTIQUE DISSIPATIF : TRANSPORT SPONTANE ET TRANSPORT STIMULE." Phd thesis, Ecole Polytechnique X, 2003. http://tel.archives-ouvertes.fr/tel-00003425.
Nous distinguons deux classes d'atomes, respectivement piégés et non-piégés dans les puits de potentiel, aux comportements très différents. Cette distinction permet de comprendre précisément le comportement des distributions de vitesse ainsi que les propriétés du transport spontané (diffusion spatiale) dans un domaine de paramètres allant du régime sautant au régime oscillant.
Des phénomènes de transport stimulés sont étudiés dans le régime intermédiaire entre les régimes sautant et oscillant où les temps typiques du mouvement hamiltonien et des phénomènes dissipatifs sont comparables. Nous caractérisons les modes de propagation Brillouin ainsi que leurs mécanismes d'excitation. Nous montrons que ceux-ci donnent lieu au phénomène de résonance stochastique qui correspond à la synchronisation du mouvement hamiltonien et des processus dissipatifs. Nous étudions enfin un rochet atomique temporel correspondant à un mouvement dirigé induit par la brisure de la symétrie temporelle.
Gangolf, Thomas. "Intense laser-plasma interactions with gaseous targets for energy transfer and particle acceleration." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX110.
Laser-matter interaction is studied mostly with near-infrared (NIR) lasers as they can generate the most intense pulses. For these lasers, targets between 0.05 to 2.5 times the critical density are challenging to create but offer interesting prospects. In this thesis, novel high-density Hydrogen gas jet targets with densities in this range are used in view of two applications:First, ions are accelerated by collisionless shock acceleration (CSA). Upon interaction of a NIR laser with a slightly overcritical gas jet target, a collimated, quasi-monoenergetic proton beam is generated in forward direction. Simulations indicate the formation of a collisionless shock and acceleration of protons both by the shock and target normal sheath acceleration (TNSA) on the target rear surface under these conditions. These directed, monoenergetic particle bunches are more suitable for many applications than the broadband particle beams already generated routinely.Second, at densities between 0.05 and 0.2 times the critical density, energy is transferred from one laser pulse (pump) to a counterpropagating pulse (seed), via Stimulated Brillouin Backscattering in the strongly-coupled regime (sc-SBS). For the case of broad- band (60 nanometers) pulses, the role of the preionization for pulse propagation and both spontaneous and stimulated Brillouin backscattering are studied, including the influence of the chirp. It is shown that for narrower bandwidths, the seed pulse is ampli- fied by tens of millijoules, and signatures of efficient amplification and pump depletion are found. This concept aims at amplifying laser pulses to powers above the damage thresholds of solid state amplifiers
Rolle, Jérémie. "Étude de la dynamique plasma dans la filamentation laser induite dans les verres de silice en présence de rétrodiffusion Brillouin stimulée et dans les cristaux de KDP." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112195/document.
In this thesis, we study the role of an inertial plasma reponse produced by laser pulses in self-focusing regime. Self-focusing is coupled with Brillouin nonlinearities for nanosecond pulses in silica glasses. For femtosecond pulses propagating in KDP crystals, self-focusing excites various ionization chanels. First of all, we derive the propagation equations for the pump and Stokes waves, subjected to filamentation due to optical Kerr effect, stimulated Brillouin scattering and plasma generation. In the second part, we present numerical results on the nonlinear propagation of LIL laser beams. These results show that temporal distribution of the pump pulse play a key role in the competition between self-focusing and stimulated Brillouin scattering. These preliminary results valide the anti-Brillouin system opted on the MegaJoule laser (LMJ) on the basis of milimetric-size laser beam.In a third part, we present numerical and theoretical results on the filamentation in fused silica of nanosecond light pulses operating in ultraviolet and infrared range. Emphasis is put on the action of a dynamical plasma reponse on two counterpropagating waves. For a single wave, we develop a variational analysis which reproduces global propagation features for a quasistationary balance between self-focusing and plasma defocusing. However, such a quasistionary balance ceases to clean up modulational instabilites induced by plasma retroaction on the pump wave. We show that phase modulations supress both simulated Brillouin scattering and plasma instabilities. The robustness of phase modulations is evaluated in presence of random fluctuations in the input pump pulse profile.Finally, we study numerically the nonlinear propagation of femtosecond pulses in fused silica and KDP. First, we show that the presence of defects involving less photons for exciting electrons from the valence band to the conduction band promotes higher filamentation intensity levels. Then, we compare the filamentation dynamic in silica and KDP crystal. The ionization model for KDP crystal takes into account the presence of defects and the electron-hole dynamics. We show that the propagation dynamics in silica and KDP are almost identical at equivalent ratios of input power over the critical power self-focusing.The summary of this thesis recalls the original results obtained and discusses the possibility of future developments
Diallo, Souleymane. "Utilisation des non-linéarités Kerr et Brillouin dans les résonateurs à mode de galerie cristallins pour la synthèse de micro-ondes." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2028/document.
Whispering galery mode resonators are dielectric cavities that support modes with ultra-high quality factor and small volume that remain confined in their inner periphery for time duratioons that can be as long as few microseconds. The strong confinement of these modes for such long durations strongly enhances nonlinear effect suchs as Kerr effect or Brillouin effect. These resonators can therefore be used for several applications such as spectroscopy, telecommunications or microwave generation. The objective of this thesis is to use Kerr and Brillouin nonlinearities in these resonators at the laser wavelength of 1550 nm, in order to generate high spectral purity microwave signals with frequencies rangong fros 5 to 30 GHz. The first chapter oh the thesis intriduces the theory, fabrication, coupling and characterisation of whispering gallery mode resonators. The second chapter is about the generation of Kerr optical frequency combs in these resonators and their application to the generation of microwave signals. We present our experimental resuktsdn the numerical modelling of Kerr combs, the analysis of oscillatory instabilities (due to thermal effect) observed during our experiments, and conclue. The third chapter concerns photon-phonon interactions via stimulated Brillouin scattering in these resonators and their application to the generation of microwave signals. We present our experimental results and the temporal model that we developed to track the dynamics of the forward and backscattered fields. The last chapter conclude the thesis. The research presented in this thesis has benne funded by the European Research Council through the project Nextphase
El, Mansouri Ibrahim. "Sources impulsionnelles picosecondes tout optique à très haut débit : applications aux télécommunications optiques." Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS064/document.
This thesis presents the work carried out on the realization of fibered 40-GHz picosecond optical pulse sources in the telecommunications C-band. In the first part, we present a numerical and experimental study of the generation of 40-GHz pulse trains thanks to the nonlinear compression of an initial beat-signal by multiple Four-Wave Mixing process. Enhanced temporal stability is achieved by generating the sinusoidal beating thanks to a Mach-Zehnder modulator driven at its zero-transmission working point. In order to improve the quality of the generated pulses, we also demonstrate the suppression of stimulated Brillouin back-scattering by inserting several optical isolators into the compression line. In the next part, we present the generation of low duty-cycle pulse trains by using a nonlinear compressor line based on 4 segments of fiber. The generated pulse trains have been encoded and then multiplexed to achieve a high bit rate signal (160 Gb/s). In the last part, we present the technology transfer steps of this optical source, such as creating a prototype of the source, prior art search and market research
DIZIER, FREDERIC. "Conjugaison de phase par effet brillouin stimule et application a une source laser solide." Paris 11, 1992. http://www.theses.fr/1992PA112409.
Olmedo, Herrero Elena. "Étude des effets non linéaires dans les lasers et amplificateurs de puissance à fibre double gaine dopée Er3+/Yb3+." Phd thesis, Télécom ParisTech, 2003. http://pastel.archives-ouvertes.fr/pastel-00000743.
Vedadi, A. "Etude et applications des amplificateurs paramétriques à fibre optique." Phd thesis, Université de Franche-Comté, 2008. http://tel.archives-ouvertes.fr/tel-00544865.
Lombard, Laurent. "Méthodes non linéaires de remise en forme de faisceaux pour amplificateur de puissance à fibre multimode." Phd thesis, Université Paris Sud - Paris XI, 2005. http://tel.archives-ouvertes.fr/tel-00160884.
- le premier réalise la remise en forme par effet photoréfractif dans un cristal de Rh:BaTiO3. Un schéma original a été proposé et validé expérimentalement. Ce convertisseur de mode transforme tout faisceau laser cohérent, dépolarisé et aberrant en un faisceau polarisé et limité par la diffraction,
- le second est issu d'une étude théorique et expérimentale détaillée de la rétrodiffusion Brillouin stimulée (SBS) dans des fibres multimodes. S'il est bien connu que des effets de conjugaison de phase ou de nettoyage de faisceau peuvent être observés par SBS dans les fibres multimodes, leurs conditions d'observation le sont moins. Cette étude permet de définir les conditions dans lesquelles les effets de conjugaison de phase (fibre à saut d'indice courte) ou de nettoyage de faisceau (fibres à gradient d'indice) sont attendus. Le schéma original proposé et validé expérimentalement est une cavité Brillouin auto-alignée contenant une fibre multimode à gradient d'indice. La remise en forme est effectuée par réflexion efficace du faisceau multimode vers le mode fondamental de la fibre à gradient d'indice.
Beugnot, Jean-Charles. "La diffusion Brillouin dans les fibres optiques microstructurées." Phd thesis, Université de Franche-Comté, 2007. http://tel.archives-ouvertes.fr/tel-00296632.
Tchahame, Nougnihi Joel Cabrel. "Diffusion Brillouin dans des fibres optiques étirées et microstructurées." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2049/document.
This PhD thesis focuses on the fundamental aspects of Brillouin scattering in chalcogenidemicrofibers and silica photonic crystal fibers with wavelength-scale solid core. Through experimentalinvestigations and numerical simulations, we have demonstrated that the Brillouin gain inchalcogenide microfiber can reach a value 150 to 250 times higher than in conventional opticalfibers. Moreover, we have reported the generation of multipeaked Brillouin spectra in a long taperedbirefringent photonic crystal fiber. A further investigation of these spectra shows that the multiresonantbehavior arises both from the excitation of hybrid acoustic waves and the fiber tapering.Another significant work of this thesis is the evidence of surface acoustic waves in small-core photoniccrystal fibers with large air filling fraction. Our results show specifically that this new type of scatteringis extremely sensitive to the air-hole microstructure geometry. Finally, these works contribute toa better understanding of Brillouin scattering in ultrathin optical fiber, paving the way towards therealization of new optoacoustic components for telecommunications and sensors
Tran, Trung Hieu. "Élasticité des verres silicatés sous pression : étude par diffusion Brillouin." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20181.
We study the elastoplastic response of silicate glasses at high stresses with Brillouin light scattering. 3D micro-Brillouin mapping residual density field are obtained in the plastic region left by a Vickers indentation. Maps are compared with finite element modeling. The joint analysis of new high-pressure measurements in a diamond anvil cell on silica in the elastic domain and literature data revealed that the abnormal hardening of elastic moduli with temperature is of dynamical origin. The onset temperature of the hardening increases with increasing applied hydrostatic pressure. We also observe that densification of silica strongly reduces the amplitude of the maximum in internal friction observed at 2 GPa as well as it suppresses the compressibility anomaly
Ivanov, Mikhaïl. "Propagation confocale et diffusion Brillouin de faisceaux acoustiques conjugués en phase." Ecole Centrale de Lille, 2008. http://www.theses.fr/2008ECLI0003.
Confocal propagation and Brillouin scattering of phase conjugated acoustical beams using the method of parametrical magneto-acoustics wave phase conjugation (WPC) is experimentally and theoretically studied. In numerical model the matching layer of 1 mm thickness with smooth variation of impedance is proposed to increase acoustic emission. The output of conjugator increasing (8. 1dB) was numerically obtained by such acoustic matching. The existence of accumulative effects in the case of the nonlinear interaction such as Brillouin scattering of the phase conjugated acoustical beams moving in the same direction was shown. The amplitude of the wave of differential frequency (WDF) in the resonant interaction of plane waves exceed the amplitude of WDF in non-resonant interaction more than three orders. Experimental results show that due to local interaction in a confocal system, the amplitude of WDF can be increase by two orders. The phase super sensitivity of WDF according to the position of the object disposed in the focal plan of a confocal system of Brillouin scattering of phase conjugated acoustical waves were shown. Presented results show the possibility to realize a parametric antenna based on the principle of the phase conjugation Stokes component of Brillouin scattering of the ultrasound waves. Developing methods can be used for the creation of ultrasound diffractive tomography devices based on WPC and meant for the detection of local non homogeneities of medium
Stiller, Birgit. "La diffusion Brillouin dans les fibres à cristaux photoniques : fondements et applications aux capteurs optiques." Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00690640.
Niklès, Marc. "La diffusion Brillouin dans les fibres optiques : étude et application aux capteurs distribués /." [S.l.] : [s.n.], 1997. http://library.epfl.ch/theses/?nr=1674.
Calderon, Quintero Ernesto. "Stabilité du quartz-α sous haute pression : étude par ultrason et diffusion Brillouin". Paris 6, 2008. http://www.theses.fr/2008PA066559.
Yindoula, Philippe-José. "Étude des réactions chimiques par diffusion de la lumière." Bordeaux 1, 1988. http://www.theses.fr/1988BOR10559.
Yaacoub, Lama. "Nano-sondes Raman-Brillouin intégrées : étude d'oxydes ultra-fins." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2411/.
The aim of this thesis is to develop a new tool for the characterization of materials at the nanometer scale. We rely on a novel approach using sound, in the THz range, as a probe of nanostructures. Acoustic phonons involved in the process of Raman-Brillouin (RB) scattering are generated and detected in a semiconductor ultrathin layer acting as a built-in probe. Inelastic light scattering occurs as a result of photon-electron and electron-phonon interactions. The built-in probe is sensitive to the structural parameter (thickness) and physical properties (refractive index, density and sound velocity) of the surround layers. We perform RB spectrometry experiments. A good understanding and interpretation of experimental data require a comparison with simulations. In order to achieve a development of the tool, we have implemented a strategy where transmission electron microscopy plays a crucial role. It allows to locally probe the structural and chemical organization of matter. We focus our attention to multilayer systems with thicknesses in the nanometric range. The high sensitivity of the response of the built-in probe to the properties of the surrounding layers as well as to their structural parameters up the sub-nanometer scale is highlighted. The concept of the built-in probe has been implemented for two systems: alumina / silicon and germanium oxide / germanium. With the first model system, we demonstrated that we can determine the sound velocity in a nano-layer of alumina by systematic comparison between experimental and simulated RB spectra. The consideration of the presence of a nanometric interfacial layer between silicon and alumina is essential to describe correctly the stack. With the second system of technological interest in particular in microelectronics, we also evidenced the presence of an ultrathin layer at the interface between germanium and his native oxide. We determined its thickness. Furthermore, we could differentiate between the kinetics of the re-oxidation of the Ge surface after a treatment by deionized water and hydrofluoric acid and we quantified the consumption of Ge during this proces. This thesis work demonstrated the interest and the effectiveness of built-in Raman-Brillouin nano-probes for the determination of physical properties of nano-layers. It allows in particular to tackle, in a relevant way, some issues related to surfaces and interfaces
Roussigne, Yves. "Diffusion brillouin dans des couches et multicouches minces magnétiques de cobalt : Etude des anisotropies et des couplages inter-couches." Paris 13, 1995. http://www.theses.fr/1995PA132010.
Stiller, Birgit. "Brillouin scattering in photonic crystal fiber : from fundamentals to fiber optic sensors." Thesis, Besançon, 2011. http://www.theses.fr/2011BESA2019/document.
Brillouin scattering is a fundamental nonlinear opto-acoustic interaction present in optical fibers with important implications in fields ranging from modern telecommunication networks to smart optical fiber sensors. This thesis is aimed at providing a comprehensive theoretical and experimental investigation of both forward and backward Brillouin scattering in next generation photonic crystal fibers in view of potential applications to above mentioned fields. We show in particular that these micro-structured optical fibers have the remarkable ability to either suppress or enhance photon-phonon interactions compared to what is commonly observed in conventional fibers. Firstly, this thesis provides a complete experimental characterization of several photonic crystal fibers using a novel highly-resolved distributed sensing technique based on Brillouin echoes. We perform distributed measurements that show both short-scale and long-scale longitudinal fluctuations of the periodic wavelength-scale air-hole microstructure along the fibers. Our mapping technique is very sensitive to structural irregularities and thus interesting for fiber manufacturers to characterize and improve the fiber uniformity during the drawing process. With this technique, we also report the first experimental observationof the acoustic decay time and the Brillouin linewidth broadening in both standard and photonic crystal fibers. Furthermore, we experimentally demonstrate a simplified architecture of our Brillouin echoes-based distributed optical fiber sensor with centimeter spatial resolution. It is based on differential phase-shift keying technique using a single Mach-Zehnder modulator to generate a pump pulse and a _-phase-shifted pulse with an easy and accurate adjustment of delay. These sensing techniques are also applied to distributed strain measurement. Another aspect of this thesis is the investigation of a novel method for suppressing stimulated Brillouin scattering that is detrimental to optical fiber transmissions and fiber lasers. We experimentally study several fibers and a demonstrate 4 dB increase of the Brillouin threshold in a photonic crystal fiber by varying periodically the core diameter by only7%. The efficiency of this passive technique is verified by use of our distributed sensing technique where the oscillating Brillouin frequency shift is clearly observed.Lastly, we present experimental and numerical results demonstrating the simultaneous vi Abstract frequency-selective excitation of several guided acoustic Brillouin modes in a photonic crystal fiber with a multi-scale structure design. These guided acoustic modes are identified by using a full vector finite-element model to result from elastic radial vibrations confined by the air-silica microstructure. We further show the strong impact of structural irregularities of the fiber on the frequency and modal shape of these acoustic resonances
Bourges, Philippe. "Etude par diffusion brillouin, raman et inelastique de neutrons de la transition structurale de l'anthracene-tetracyanobenzene." Rennes 1, 1989. http://www.theses.fr/1989REN10089.
Hey, Tow Kenny. "Laser Brillouin à fibre microstructurée en verre de chaleogénure." Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00860216.
Belafhal, Abdelmajid. "Etude de la dynamique des fluides atomiques à hautes pressions : cas du xénon." Bordeaux 1, 1986. http://www.theses.fr/1986BOR10538.
HE, JIANJUN. "Diffusion raman-brillouin par les phonons acoustiques dans les superreseaux semiconducteurs et extension a l'interaction lumiere-ultrason." Paris 6, 1989. http://www.theses.fr/1989PA066236.
Godet, Adrien. "Spectroscopie Brillouin des micro et nanofils optiques de silice." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD067/document.
This thesis reports the design and fabrication of subwavelength-diameter silica optical fibers, also known as optical micro and nanowires. These hair-like slivers of glass, manufactured by tapering optical fibers down to a size hundred times smaller than a strand of human hair, have a number of optical and mechanical properties that make them very attractive for both fundamental physics and technological applications. In addition to providing strong light confinement and enhanced nonlinear optical effects, they exhibit a large evanescent field, enabling applications not currently possible with comparatively bulky optical fibers.We here explore their elastic properties through Brillouin spectroscopy. We specifically provide a complete description, both theoretically and experimentally, of the backward Brillouin spectra including the observation of both bulk hybrid and surface acoustic waves with many anti-crossings. A very good agreement is found between numerical simulations of the elastodynamics equation and the experimental Brillouin spectra for a wide range of wire diameters. From this study, we demonstrate a simple and non-destructive in-situ technique for measuring the diameter of these ultra-thin fibers and their uniformity with a high sensitivity of only a few nanometers. A distributed measurement of both the surface and hybrid acoustic waves along an optical microwire was then performed using Brillouin optical correlation technique. We further investigate the tensile strain dependence of Brillouin scattering in optical microwires and report, for the first time to our knowledge, evidence of a strong elasticity and non-linearity of the elastic constants of silica. This thesis therefore demonstrates that optical microwires can find various potential applications for strain optical sensing
De, Clermont-Gallerande Jonathan. "Synthèse, structure, et étude mécanique de matériaux tellurites visant des applications en optique non-linéaire." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0082.
This work aims to comparatively study three systems aimed at nonlinear optical application, TeO2-TiO2-ZnO (TTZ); TeO2-TiO2-Nb2O5 (TTN) and TeO2-GeO2-ZnO (TGZ). The goal is to highlight correlations between structural and mechanical properties of the studied glasses at room temperature but also as a function of temperature, and in particular around the glass transition temperature (Tg). The structural study of the glasses showed that in the TTZ system, the zinc had a coordination and hence a behavior change in the tellurite matrix as a function of the concentration. Those results were correlated to the elastic properties of the glasses, the Young modulus, the shear modulus and the Poisson ratio, who presented nonlinear evolutions as a function of the ZnO concentration. In the TGZ system, in contrary to the TTZ system, these singular evolutions were not highlighted. It was hypothesized that the germanium oxide is preventing the change in comportment of the zinc polyhedra. For the TTN system, no major structural changes were observed as a function of niobium oxide concentration, which was translated with a linear increase of the elastic properties of those glasses. The temperature dependent studies showed that before the glass transition temperature (Tg), the Boson peak frequency (Raman spectroscopy) and the elastic properties evolutions are in accordance with the vitreous network relaxation idea. After Tg, the structural and mechanical evolution showed a transition toward a viscous liquid state. At last, it was possible to evidence a correlation after Tg of the evolution of the Boson peak frequency and the elastic properties, thus allowing a prediction of the mechanical properties thanks to the low frequency vibrational study in tellurite glasses. These information are key parameters needed to help the glass shaping mastery of these types of glasses
Belkadi, Miâd. "Effets de la température sur l'étude des réactions chimiques du type A->B, par diffusion Rayleigh-Brillouin." Bordeaux 1, 1990. http://www.theses.fr/1990BOR10589.
Alevizaki, Athina. "Analysis and control of elastic waves in phononic structures of poroelastic inclusions in a fluid." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMLH24/document.
In the present thesis, an extension of the layer multiple scattering computational methodology to phononic structures of fluid-saturated poroelastic spherical bodies, combining Biot's theory with multiple scattering techniques, is developed. The method is applied to the theoretical study, beyond the long wavelength effective-medium approximation, of the acoustic response of double-porosity liquid-saturated granular materials consisting of close-packed hard or soft porous spheres. It is shown that variations of the pore size and/or the porosity within the millimeter and submillimeter-sized spherical grains signicantly alters the transmission, reflection, and absorption spectra of finite slabs of these materials. The calculated spectra are analyzed by reference to the acoustic modes of the constituent porous spherical grains as well as to relevant dispersion diagrams of correspondingly infinite crystals, and a consistent interpretation of the underlying physics is presented. Our results provide evidence for the occurrence of novel, unprecedented modes, localized in the sphere, which arise from slow longitudinal waves that are peculiar to poroelastic media. These modes induce some remarkable features in the acoustic behavior of these double-porosity materials under study, such as broad or narrow dispersionless absorption bands and/or directional transmission gaps. The acoustic properties of phononic (sub)micro structures, in the hypersonic (GHz) regime, can be probed, in general, by Brillouin light scattering experiments. In the present thesis we undertake a rigorous full elasto-optic theoretical approach to inelastic light scattering due to phonon induced spatiotemporal variations of the refractive index of a medium, based on Green's functions, and derive analytical expressions for the intensities of the scattered light beams by single spherical particles in vacuum, thus improving the computational efficiency and accuracy of previous calculations. The above framework provides, also, the basis for a rigorous description of the effect for phononic crystals of colloidal spherical particles
Lou, Nelson. "Couches supportées et membranes ultraminces à base de silicium : fabrication et spectrométrie raman-brillouin." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/557/.
The improvements in Micro and now Nanoelectronic lead to the shrinking of the devices and at the same time the need to develop suitable and effective methods of characterization. Following this motion, we focused our interest on the use of terahertz sound as a matter probe at nanometric scale in inelastic scattering of light experiments. To that end, we studied Raman-Brillouin scattering of ultra thin layers of silicon which implies the interaction between localized electronic states and acoustic phonons with wavelengths in nanometric range. In the aim to study the effect of its surrounding on the Raman-Brillouin scattering of an ultra thin silicon layer, we made model systems composed of nanometric layers stacks of different materials (silicon, silicon nitride and silicon dioxide) on substrate or in membrane configuration. A high-performance Raman spectrometer, in low frequency range and coupled with an original optical input, enabled us to study the Raman-Brillouin scattering of these model systems. We systematically compared the experimental spectrums to simulations based on photo elastic model. That systematic comparison enabled us to identify of the optical and acoustic cavity functions and some criteria and a methodology to be able to analyse quantitatively the experimental data. The developed approach shows to be particularly sensitive in the face of oxide and interfacial layers whose thicknesses don't exceed two nanometres. .