Littérature scientifique sur le sujet « Cristaux photoréfractifs »
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Articles de revues sur le sujet "Cristaux photoréfractifs"
Roosen, G., G. Le Saux, G. Pauliat, M. Allain, J. M. C. Jonathan et A. Brun. « Effet photoréfractif dans les cristaux d'oxyde de bismuth et de silicium (Bi12SiO20) ou de germanium (Bi12GeO20) ». Revue de Physique Appliquée 22, no 10 (1987) : 1253–67. http://dx.doi.org/10.1051/rphysap:0198700220100125300.
Texte intégralAmara, M. K., et C. Özkul. « Vélocimétrie par imagerie de particules holographique : enregistrement simultané de plusieurs nappes par codage de cohérence dans un cristal photoréfractif Holographic particle image velocimetry : simultaneous recording of several light sheets by coherence encoding in a photorefractive crystal ». Journal of Optics 28, no 4 (août 1997) : 173–80. http://dx.doi.org/10.1088/0150-536x/28/4/005.
Texte intégralThèses sur le sujet "Cristaux photoréfractifs"
Tascu, Sorin. « Étude en champ proche optique de guides optiques, de luminescence et d'effets photoréfractifs dans des cristaux ». Lyon 1, 2003. http://www.theses.fr/2003LYO10250.
Texte intégralGrappin, Florence. « Capteur multicanal à grand champ pour la détection d'ultrasons : matériaux pour l'adaptation dynamique de front d'onde : étude et implantation du capteur ». Paris 11, 2004. http://www.theses.fr/2004PA112038.
Texte intégralUltrasonic waves are often used by industrials to test the structure of parts. Most of time, they work with piezoelectric transducers to generate and detect these waves but this technique needs a contact between the object to test and the transducers whereas optics allows to have non-contact and non-destructive systems (“laser-ultrasonic”). The optical detection of ultrasonic waves consists in the demodulation of the phase modulation carried by the laser beam that is backscattered by the part in which ultrasonic waves propagate. An interferometer operates this demodulation. Because of the roughness of the object’s surface, the interferometer has to be speckle insensitive. The holographic ultrasonic sensor is an interferometer that demodulates the phase in real time thanks to dynamical gratings written in a photorefractive material. The presented work can be divided into two parts. First, we studied photorefractive materials to improve the results achieved by the sensor. We compared experimental measurements for semi-conductors crystals (InP, CdTe) with the theoretical model describing their photorefractive properties. We also created a new method to characterize photorefractive multiquantum wells at a fixed wavelength and compared their efficiency in the sensor with the one obtained with bulk crystals. Second, we developed the multichannel photorefractive ultrasonic sensor. We studied the means to implement the imaging systems necessary to work with several testing points on the object, and the consequences on the eventual presence of cross-talk. Then, we implemented the experimental setup and demonstrated the simultaneous demodulation of different ultrasonic signals
Danielyan, Anush. « Propriétés photoréfractives et électro-optiques des cristaux de niobate de lithium dopés aux ions métalliques ». Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0256.
Texte intégralLithium niobate (LN) is attractive material for the frequency mixers and doublers, integrated optical devices, electro-optical modulators, holographic data recording and storage thanks to the acousto-optical, non-linear optical, piezo-electrical, electro-optical and photorefractive properties. However, the overall understanding of certain phenomena that is photorefractive effect occurring in the crystal is still under heavy discussion. The mentioned plays a key role: on one side it substantially restricted the main part of the wavelength conversion applications as when illuminated by visible light or near infrared, there are changes semi-permanent in the refractive index of the crystal, causing a distortion of the beam, greatly reducing the efficiency of the device, on the other hand it need to improve for holographic applications. The dissertation is devoted to the investigation of the photorefractive, structural, electro-optical (EO) and dielectrical properties depending on the intrinsic and extrinsic (introduced by incorporation of non photorefractive (〖Zr〗^(4+),〖In〗^(3+)) and photorefractive (〖Fe〗^(2+/3+)) ions) defects in LN crystals resulting to the purposeful control the photorefractive effect taking into account the features of the applications of LN crystals. The aim of the thesis is a development of a vision on advanced photorefractive and electro-optic properties in lithium niobate crystals doped with the transition metal and non-photorefractive ions on the basis of a full investigation of the structural, compositional, electro-optical, photorefractive properties of the mentioned crystals, to work out the parameters of a strong control of the photorefractive properties of this material and optimal conditions for the growth of high quality mentioned crystal with controlled physical properties and to grow this crystals as well
Bouldja, Nacera. « Slow Light in a SPS Photorefractive Crystal ». Electronic Thesis or Diss., CentraleSupélec, 2020. http://www.theses.fr/2020CSUP0005.
Texte intégralSlow light is the science domain that focuses on the physical nonlinear processes that canreduce the group velocity of a light pulse as it propagates in the medium. This discoveryhas been a great deal of recent interest for a wide range of applications such as opticalbuffering, nonlinear photonics and various types of spectroscopic.The slow light performance is typically measured through two key parameters: the valueof the delay or the group delay and the bandwidth of the output light pulse. This lastone is generally defined by the so-called fractional delay, which is the ratio between theoptical delay and the width of the output pulse. It is important to know that the opticaltelecommunication needs a slow light system that is able to slowdown short input lightpulses with therefore a large value of the fractional delay (FD).In the last years, numerous studies of slow light have been performed in several dispersivematerials at different wavelengths. In 1999, group velocities smaller than 17 m/s [1] havebeen experimentally measured by Hau et al. in an ultra-cold gas using ElectromagneticallyInduced Transparency. More recently, the deceleration of the light pulses has been alsosuccessfully observed in solid-state materials such as in optical fibers [2] and in photoniccrystals [3]. On the other hand, several studies have shown that photorefractive (PR)crystals can also be used to reduce the light propagation velocity at room temperature.As a matter of fact, the smallest group velocity of 0.025 cm/s has been achieved using therecording of refractive index gratings in a BaTiO3 photorefractive crystal [4]. This methodconsists of the coupling of a continuous pump beam and a probe signal to increase therefractive index dispersion and leads the generation of a photorefractive gain. However,this small group velocity is often accompanied by the output pulse distortion which reducesthe value of the fractional delay (FD of the order of 0.4 in [4]).This thesis focuses on the study of the methods which allow in addition to the decelerationgroup velocity, the limitation of the distortion of the pulse in a photorefractive (PR) media.First, using the two-wave mixing (TWM) method, the PR crystal with a response time of10 ms can slow down bright or dark pulses with duration of the order of ms. It is shownthat the value of the time delay and the width of the transmitted pulse can be controlledby the photorefractive gain and the input pulse duration. By improving the TWM setup,we measure a fractional delay of 0.79 and 1 respectively, for the bright and the dark pulseswith a duration close to the response time of the crystal. The beam fanning in a PRcrystal has also been used to slow down a single light pulse. The coupling between thebeam fanning and the input beam leads both to the modulation of the noisy refractiveindex gratings and to the slowing down of the output pulse. The use of beam fanning forlight slow down is new and significantly simplifies the slow light setup.Slow light with the TWM and the beam fanning can be observed for long pulses, typicallyfor a pulse of the order of the milliseconds and the seconds. In other words, only pulseswith durations around the crystal response time are slowed down. In this thesis, we showfor the first time that the use of the TWM at the nanosecond regime and a high laserintensity can reduce the photorefractive response time of the crystal and the slowdown ofa shorter pulse (with a width of ns). The results achieved in a PR crystal with a thicknessof 1 cm are similar to those achieved in slow light systems using a km-long optical fiberand for the same pulse durations
Bouchet, Thomas. « Non linear interaction of self-accelerating light beams ». Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0312.
Texte intégralIn this thesis we present results concerning the propagation of an Airy beam in a photorefractive crystal. The Airy beam is a multi-lobed beam that keeps the same shape while propagating along a curved trajectory. It can also regenerate its profile while propagating if it is partially blocked. The photorefractive crystal is a nonlinear media. Light can imprint its intensity distribution inside the crystal and a light beam can create its own waveguide. The Airy beam propagation is changed When going through the crystal. The parabolic trajectory changes partially or completely to a solitary straight beam. Furthermore, this propagation behavior is imprinted inside the crystal and this creates a complex waveguiding structure. By changing the Airy beam parameters and the nonlinear response of the crystal, different waveguiding configurations can be obtained. We can therefore create and control an all-optical routing device with potential applications in the field of telecommunications
Bahsine, Saïda. « Caractérisation optique et électro-optique des cristaux photoréactifs BaTiO3 dopés Rh (BaTiO3:Rh) et BaxCa1-xTiO3 dopés rhodium ». Metz, 2002. http://www.theses.fr/2002METZ032S.
Texte intégralIsmaili, Mimoun. « Effet Frederiks optique dans les nématiques : contributions thermique et diélectrique à la photoréfractivité ». Lille 1, 1993. http://www.theses.fr/1993LIL10131.
Texte intégralImbert, Béatrice. « Étude et applications de l'effet photoréfractif dans les semi-conducteurs GaAs ». Paris 11, 1988. http://www.theses.fr/1988PA112325.
Texte intégralThe compound semiconductors such as GaAs are very suitable for photorefractive applications in the near infra-red spectral region. A spatially modulated light beam incident on such a photo-conducting material produces a spatial modulation of free charges which in turn generates a space-charge field in the volume of the material. Since these semiconductors are electro-optic, the space-charge field modifies the refractive index and gives rise to a phase grating. When a pump beam and a signal beam write a phase grating in a GaAs : Cr crystal, there is an exchange of energy between the beams and under optimal conditions of operation, the signal beam can be significantly amplified. The GaAs : Cr optical amplifier has found many applications, for example, coherent image amplification, self-oscillating cavities and phase conjugation with amplification
Victori, Stéphane. « Etude de l'affinement spectral d'un oscillateur paramétrique optique (OPO) en régime nanoseconde par insertion d'un cristal photoréfractif : Modélisation des OPO monomodes ». Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://pastel.archives-ouvertes.fr/pastel-00714252.
Texte intégralGorram, Mohamed. « Génération et étude de guides d'onde dynamiques et reconfigurables induits par illumination latérale ». Thesis, Metz, 2009. http://www.theses.fr/2009METZ013S/document.
Texte intégralThe realization transparent achievement of optical networks that do not need electronic components for the temporary detection and regenration of signals asks for optical routing and interconnection elements which are reconfigurable in short time, in the order of milliseconds in the case telecommunications networks. The use of optical waveguides in active materials made of active materials by conventional techniques, such as ion-indiffusion, proton exchange or ion implantation is badly suitable for this goal. These techniques give rise only to static waveguides close to the material surface and they are not easily modified. The technique of light inducing waveguides by lateral illumination developed in this work allows to cross an important step towards purely optical devices in which light is used to guide and manipulate light without resorting to complex manufacturing steps. The main advantage is that this effect can be erased, giving rise to dynamic structures that do note cause a permanent damage of the material. Another advantage is the versatility with respect to the form of the waveguides, that is defined by the structure imposed to control the illumination perpendicular to the direction of propagation. The feasibility of reconfigurable 1-dimensional waveguides has been experimentally demonstrated in the electro-optic ferroelectric crystals SrxBa1xNb2O6 (SBN, x=0.61) and Sn2P2S6 (SPS). The illuminating wavelengths used were 514 nm for SBN and 633 nm for SPS. Response and reconfiguration times of the order of 1 ms are shown to be possible in the case of SPS. The dynamics of the waveguides has been studied on the basis of theoretical treatment and numerical simulations. The evolution of light induced one-dimensional waveguides when the sustaining electric field is switched off leads to a novel kind of dynamic light deflection. We have studied this effect in detail using SBN and LiTaO3 crystals. Simulations of the beam propagation in the split waveguide on the base of a simple model lead to a good agreement with the experimental observations. Light modulation by the help of this effect has been demonstrated as well. Finally, we realized for the first time, the recording of dynamically reconfigurable bulk channel waveguides confined in two dimensions using lateral illumination technique. The experimental studies of the dependence of the output probe wave profile on the intensities of two control waves and on the applied electric field were found to be in good agreement with the expectations based on a simplified step profile for the photorefractive by induced refractive index change and on mode calculations
Actes de conférences sur le sujet "Cristaux photoréfractifs"
Delaye, Philippe, et Gérald Roosen. « Matériaux photoréfractifs ». Dans Élaboration et caractérisation des cristaux massifs et en couches minces pour l'optique. Les Ulis, France : EDP Sciences, 2003. http://dx.doi.org/10.1051/bib-sfo:2002817.
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