Relevant bibliographies by topics / Effet photorefractif

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  3. Books
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Academic literature on the topic 'Effet photorefractif'

Author: Grafiati
Published: 4 June 2021
Last updated: 31 July 2024

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Journal articles on the topic "Effet photorefractif"

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Xu, Lei, and Guanying Chen. "Optimization of Blue Photorefractive Properties and Exponential Gain of Photorefraction in Sc-Doped Ru:Fe:LiNbO3 Crystals." Crystals 12, no. 8 (2022): 1059. http://dx.doi.org/10.3390/cryst12081059.

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Sc:Ru:Fe:LiNbO3 crystals were grown from congruent melt by using the Czochralski method. A series of LiNbO3 crystals (Li/Nb = 48.6/51.4) with 0.1 wt% RuO2, 0.06 wt% Fe2O3 and various concentrations of Sc203 were prepared. RF1 and RF4 refers to the samples containing 0 mol% Sc203 and 3 mol% Sc203, respectively. The photorefractive properties of RF4 were measured by Kr+ laser (λ = 476 nm blue light): ηs = 75.7%, τw = 11 s, M/# = 19.52, S = 2.85 cmJ−1, Γ = 31.8 cm−1 and ∆nmax = 6.66 × 10−5. The photorefractive properties of five systems (ηs, M/#, S, Γ and ∆nmax) under 476 nm wavelength from RF1 to RF4 continually increased the response time, while τw was continually shortened. Comparing the photorefractive properties of Sc (1 mol%):Ru (0.1 wt%):Fe (0.06 wt%): LiNbO3 measured by Kr+ laser (λ = 476 nm blue light) with Sc (1 mol%):Fe (0.06 wt%):LiNbO3 measured by He-Ne laser (633 nm red light), ηs increased by a factor of 1.9, Vw (response rate) increased by a factor of 13.9, M/# increased by a factor of 1.8 and S increased by a factor of 32. The ∆nmax improved by a factor of 1.4. A strong blue photorefraction was created by the two-center effect and the remarkable characteristic of being in phase between the two gratings recorded in shallow and deep trap centers. The photorefractive properties (ηS, τw, M/#, S, ∆nmax) were increased with an increase in Sc3+ ion concentration. Damage-resistant dopants such as Sc3+ ions were no longer resistant to damage, but they enhanced the photorefractive properties at the 476 nm wavelength. The experimental results clearly show that Sc-doped two-center Ru:Fe:LiNbO3 crystal is a promising candidate blue photorefraction material for volume holographic storage. Sc-doped LiNbO3 crystal can significantly enhance the blue photorefractive properties according to the experimental parameters. Therefore, the Sc:Ru:Fe:LiNbO3 crystal has better photorefractive properties than the Ru:Fe:LiNbO3 crystal.
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Palatnikov, Mikhail, Nikolay Sidorov, Sergey Panasjuk, Natalya Teplyakova, and Olga Makarova. "Radiation Modification of Optical Characteristics of LiNbO3:Zn and LiNbO3:Mg Crystals." Crystals 12, no. 5 (2022): 600. http://dx.doi.org/10.3390/cryst12050600.

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The modification of the optical characteristics of LiNbO3:Zn and LiNbO3:Mg crystals grown by the Czochralski method was investigated using β and γ radiation. The photorefractive effect was found to be inhibited by ionizing radiation in the LiNbO3:Zn ([ZnO] ≈ 2.1 mol%) crystal, which belonged to a below-threshold concentration range. The inhibition was attributed to a stepwise radiation annealing of charged defects. Ionizing radiation increased the general optical uniformity of above-threshold crystals LiNbO3:Zn ([ZnO] ≈ 5.9 mol%) and LiNbO3:Mg([MgO] ≈ 5.6 mol%). In addition, we determined that radiation annealing substantially influenced photorefraction dynamics in lightly doped LiNbO3:Zn ([ZnO] ≈ 0.1 mol%) crystals, which widens their application areas.
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Palatnikov, Mikhail, Nikolay Sidorov, Sergey Panasjuk, Natalya Teplyakova, and Olga Makarova. "Radiation Modification of Optical Characteristics of LiNbO3:Zn and LiNbO3:Mg Crystals." Crystals 12, no. 5 (2022): 600. http://dx.doi.org/10.3390/cryst12050600.

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The modification of the optical characteristics of LiNbO3:Zn and LiNbO3:Mg crystals grown by the Czochralski method was investigated using β and γ radiation. The photorefractive effect was found to be inhibited by ionizing radiation in the LiNbO3:Zn ([ZnO] ≈ 2.1 mol%) crystal, which belonged to a below-threshold concentration range. The inhibition was attributed to a stepwise radiation annealing of charged defects. Ionizing radiation increased the general optical uniformity of above-threshold crystals LiNbO3:Zn ([ZnO] ≈ 5.9 mol%) and LiNbO3:Mg([MgO] ≈ 5.6 mol%). In addition, we determined that radiation annealing substantially influenced photorefraction dynamics in lightly doped LiNbO3:Zn ([ZnO] ≈ 0.1 mol%) crystals, which widens their application areas.
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Ljuboje, Zoran. "Some examples of photorefractive oscillators." Electronics ETF 19, no. 2 (2016): 105. http://dx.doi.org/10.7251/els1519105l.

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The photorefractive effect presents a periodical change of the refractive index of an optical environment under the influence of a coherent light. An interesting phenomenon which occurs at this effect is optical phase conjugation (PC). Photorefractive oscillators, that is photorefractive mirrors present important decides in photorefractive optics and their function is based on photorefractive effect. In these oscillators, a phase-conjugated light beam occurs. The basic characteristics of photorefractive oscillators, such as reflectivity, the existance of the oscillation threshold and the threshold of the coupling strength are explained by the so-called grating-action method. This is analysed on a ring oscillator, semilinear mirror and linear mirror.
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GU, C., and P. YEH. "APPLICATIONS OF PHOTOREFRACTIVE VOLUME HOLOGRAPHY IN OPTICAL COMPUTING." Journal of Nonlinear Optical Physics & Materials 03, no. 03 (1994): 317–37. http://dx.doi.org/10.1142/s0218199194000195.

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After a brief review of the photorefractive effect, we describe three examples of the applications in optical computing using photorefractive volume holography. These are 3-dimensional optical storage, parallel optical matrix processor, and multiwavelength optical half-adder. For the 3-dimensional optical storage, we consider some fundamental issues in photorefractive memory, including the storage capacity and the dynamic range. We also discuss the photorefractive noise gratings formed during a multiple exposure schedule. These fundamental issues in photorefractive storage are important in understanding the potentials and limitations of optical memory systems. For parallel optical matrix processing, we propose and demonstrate a novel method of matrix-matrix application using grating degeneracy in photorefractive media in conjunction with incoherent laser source arrays. For multiwavelength optical half-adder, we describe photorefractive logic gates and their application in the summation of binary numbers.
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YEH, POCHI, and CLAIRE GU. "PHOTOREFRACTIVE MEDIA FOR OPTICAL INTERCONNECTIONS." Journal of Nonlinear Optical Physics & Materials 01, no. 01 (1992): 167–201. http://dx.doi.org/10.1142/s0218199192000108.

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The photorefractive effect and its applications in optical interconnections are described. The fundamental limit, the dynamics of grating formation, and the two-wave mixing (TWM) process are discussed. Reconfigurable interconnections for parallel optical computing is demonstrated using photorefractive holograms. Neural network interconnections with photorefractive media are also presented.
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Xue, Liyun, Hongde Liu, Dahuai Zheng, et al. "The Photorefractive Response of Zn and Mo Codoped LiNbO3 in the Visible Region." Crystals 9, no. 5 (2019): 228. http://dx.doi.org/10.3390/cryst9050228.

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We mainly investigated the effect of the valence state of photorefractive resistant elements on the photorefractive properties of codoped crystals, taking the Zn and Mo codoped LiNbO3 (LN:Mo,Zn) crystal as an example. Especially, the response time and photorefractive sensitivity of 7.2 mol% Zn and 0.5 mol% Mo codoped with LiNbO3 (LN:Mo,Zn7.2) crystal are 0.65 s and 4.35 cm/J at 442 nm, respectively. The photorefractive properties of the LN:Mo,Zn crystal are similar to the Mg and Mo codoped LiNbO3 crystal, which are better than the Zr and Mo codoped LiNbO3 crystal. The results show that the valence state of photorefractive resistant ions is an important factor for the photorefractive properties of codoped crystals and that the LN:Mo,Zn7.2 crystal is another potential material with fast response to holographic storage.
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Liu, Wei, Haitao Yang, Wenbo Wu, et al. "Calix[4]resorcinarene-based branched macromolecules for all-optical photorefractive applications." Journal of Materials Chemistry C 4, no. 45 (2016): 10684–90. http://dx.doi.org/10.1039/c6tc04062d.

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Kostritskii, Sergey. "Peculiarities of Photorefractive Response in Planar Waveguides Fabricated by Combined Proton and Copper Exchange." Journal of Nonlinear Optical Physics & Materials 06, no. 03 (1997): 321–31. http://dx.doi.org/10.1142/s0218863597000241.

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In this work a photorefractive effect in proton-exchanged planar waveguides on LiNbO 3 crystals is discussed. These waveguides are doped by copper with the aid of a new technique using the low-temperature ionic exchange. The experimental investigation has revealed the anomalous character of the photorefractive response in strongly doped waveguides. Photorefractive measurements are made over a wide range of H +, Cu + and Cu 2+ concentrations, altered by a seriesof oxidation treatments caused by back ionic exchange. Fabrication parameters allowing the realization of high photorefractive sensitivity either in visible or near infra-red ranges are identified.
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Chen, Xiaoxiao, Xiuqin Feng, Zuolin Tian, and Zhihai Yao. "Controlling and synchronizing the spatiotemporal chaos of photorefractive ring oscillators with coupling." Modern Physics Letters B 30, no. 18 (2016): 1650236. http://dx.doi.org/10.1142/s0217984916502365.

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We present the control and synchronization of spatiotemporal chaos in the photo-refractive ring oscillator systems with coupling technology. First, we realize the synchronization of spatiotemporal chaos in the two photorefractive ring oscillator systems via mutual coupling by choosing a suitable coupling strength. With the mutual coupling strength enlarging, the two mutual coupling photorefractive ring oscillator systems are controlled into periodic state, period number differs on account of the coupling strength and lattice coordinates. By increasing the coupling strength, the photorefractive ring oscillator is converted into period 8, subsequently it is converted into periods 4 and 2, periodic synchronization of the photorefractive ring oscillator systems is achieved at the same time. Calculation results show that period 1 is impossible by mutual coupling technology. Then, we investigate the influence of noise and parameter deviation on chaotic synchronization. We find that mutual coupling chaotic synchronization method can synchronize two chaotic systems with the weak noise and parameter deviation and has very good robustness. Given that the weak noise and parameter deviation have a slight effect on synchronization. Furthermore, we investigate two dimension control and synchronization of spatiotemporal chaos in the photorefractive ring osillator systems with coupling technology and get successful results. Mutual coupling technology is suitable in practical photorefractive ring oscillator systems.
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Dissertations / Theses on the topic "Effet photorefractif"

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Daniel, Olivier. "Effet photorefractif pour la reconnaissance des formes : modelisation et optimisation." Paris 11, 1995. http://www.theses.fr/1995PA112392.

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Au cours de ce travail de these, j'ai realise un dispositif optique de reconnaissance des formes par transformations de fourier conjointes utilisant un cristal photorefractif. Le point essentiel en est l'etude du comportement du cristal dans les conditions imposees experimentalement et les consequences sur le fonctionnement du dispositif. La premiere partie du document dresse un etat de l'art. Le principe de la reconnaissance par correlation est presente en y incluant le filtrage et les architectures possibles. L'effet photorefractif est egalement brievement decrit. La seconde partie est une description du correlateur naopia. Je detaille les conditions experimentales imposees par le dispositif: contraintes sur le materiau photorefractif, selectivite de bragg, diffraction anisotrope et effet d'un champ electrique externe. Je definis aussi les criteres de selection d'un cristal photorefractif. La troisieme partie modelise les differents phenomenes rencontres. Je compare tout d'abord le correlateur lineaire avec le dispositif photorefractif. Je donne ensuite une expression analytique vectorielle originale du champ de charge d'espace photoinduit valable quel que soit l'eclairement du cristal, puis les conditions d'utilisation pour la diffraction anisotrope. La derniere partie illustre ces resultats: influence du nombre d'objets sur le signal de sortie, invariances du montage, reconnaissances d'objets complexes, recouvrement d'objets
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Safioui, Jassem. "Nouvelle technique de photo-inscription dans LiNbO3 : autofocalisation contrôlée par effet pyroélectrique." Phd thesis, Université de Franche-Comté, 2010. http://tel.archives-ouvertes.fr/tel-00611720.

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Dans ce travail de thèse nous avons exposé une nouvelle méthode simple et efficace basée sur l'autofocalisation de faisceaux qui permet l'induction de guides optiques au cœur de matériaux photoréfractifs, sans tension appliquée. Cette technique de photo-inscription exploite l'effet pyroélectrique des matériaux ferroélectriques qui permet de générer un effet non linéaire focalisant contrôlé par une augmentation de quelques degrés de la température du matériau. La démonstration expérimentale est réalisée dans les échantillons de LiNbO³ non dopé. Une analyse détaillée de la dynamique de focalisation a notamment permis de former des solitons spatiaux dénommés " pyrolitons ". Ces solitons brillants permettent d'induire des guides circulaires à faibles pertes qui restent mémorisés sur de longues périodes dans le matériau. Par ailleurs, des solitons de surface se propageant à l'interface air/LiNbO³ ont également été observés grâce à cet effet non linéaire contrôlé par la pyroélectricité. Ces résultats expérimentaux ont été confirmés par un modèle numérique 3-D qui prend en compte la dynamique de l'effet photoréfractif. La non linéarité optique commandée en température révélée dans ce travail peut faciliter la mise en évidence de nouveaux concepts. En outre, la technique de photo-inscription associée ouvre de nouvelles perspectives pour la fabrication de circuits optiques 3-D dans le LiNbO³, matériau de référence pour la photonique.
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De, Montmorillon Louis-Anne. "Capteur photorefractif d'ultrasons : choix et optimisation d'un matériau holographique ; étude et réalisation d'un prototype. Senseur photorefractif d'ultrasons : choix et optimisation d'un matériau holographique ; étude et réalisation d'un prototype." Phd thesis, Université Paris Sud - Paris XI, 1997. http://pastel.archives-ouvertes.fr/pastel-00716009.

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Les matériaux photorefractifs sont ici mis en oeuvre pour l'analyse sans contact des très faibles vibrations engendrées en surface d'une pièce mécanique brute et donc rugueuse. Nous réalisons un couplage entre un faisceau de référence et un faisceau signal issu de la surface vibrante et construisons, grâce a l'effet photorefractif, un oscillateur local qui va interférer en teinte plate avec le faisceau signal transmis quelle que soit la structure spatiale de ce dernier. De plus, le matériau photorefractif va s'adapter aux phénomènes lents, correspondant a des vibrations parasites ou a des déréglages du système, tout en restant sensible aux vibrations de hautes fréquences (ultrasons). Le cdte:v est le matériau photorefractif que nous avons choisi. Il présente des performances adaptées a notre application sur une plage de longueur d'onde comprise entre un et un virgule cinquante-cinq micromètre. Nous présentons une étude des propriétés photorefractives de ce matériau et en particulier une méthode qui nous a permis de déterminer avec précision la densité effective de pièges des échantillons testés. Nous avons ensuite mis au point un senseur photorefractif qui présente des sensibilités comparables a celles des techniques classiques qui elles ne fonctionnent qu'avec des ondes planes. Pour cela, nous avons applique un champ électrique continu au cristal photorefractif afin de mettre en quadrature le signal transmis et l'oscillateur local. Un avantage de cette technique sous champ est la très faible influence du phénomène de compétition electron-trou, présent dans nos cristaux, permettant une réponse indépendante de la longueur d'onde utilisée. Enfin, nous travaillerons en régime d'atténuation car on évite ainsi un phénomène de résonance gênant tout en accédant a la même sensibilité qu'en régime d'amplification
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Safioui, Jassem. "Nouvelle technique de photo-inscription dans LiNbO3 : autofocalisation contrôlée par effect pyroélectrique." Phd thesis, Besançon, 2010. http://www.theses.fr/2010BESA2018.

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Dans ce travail de thèse nous avons exposé une nouvelle méthode simple et efficace basée sur l'autofocalisation de faisceaux qui permet l'induction de guides optiques au coeur de matériaux photoréactifs, sans tension appliquée. Cette technique de photo-inscription exploite l'effet pyrolélectrique des matériaux ferroélectriques qui permet de générer un effet non linéaire focalisant contrôlé par une augmentation de quelques degrés de la température du matériau. La démonstration expérimentale est réalisée dans des échantillons de LiNbO3 non dopé. Une annalyse détaillée de la dynamique de focalisation a notamment permis de former des solitons spaciaux dénommés "pyrolitons". Ces solitons brillants permettent d'induire des guides circulaires à faibles pertes qui restent mémorisés sur de longues périodes de matériau. Par ailleurs, des solitons de surface se propageant à l'interface air/ LiNbO3 ont également été observés grâce à cet effet nonlinéaire contrôlé par la pyroélectricité. Ces résultats expérimentaux ont été confirmés par un modèle numérique 3-D qui prend en compte la dynamique de l'effet photoréfractif. La non linéarité optique commandée en température révélée dans ce travail peut faciliter la mise en évidence de nouveaux concepts. En outre, la technique de photo-inscription associée ouvre de nouvelles perspectives pour la fabrication de circuits optiques 3-D dans le LiNbO3, matériau de référence pour la photonique<br>In this work a new simple and effective method, based on self-focusing beams which allows the photo-inscription of optical waveguides in the bulk of photorefractive materials, without applied field, is presented. This photo-inscription method uses the pyroelectric effect present in ferroelectric materials to yield a nonlinear focusing effect controlled by sample temperature change. Experimental demonstrations of pyroelectric beam trapping are realized in non intentionally doped lithium niobate crystals. Detailed studies led to spatial solitons formation called "pyrolitons " This spatial solitons induce circular waveguides with low loss which remain memorized for a long time in the material. In addition, propagation of surface solitons at the interface between air and LiNbO3 are also demonstrated thanks to this nonlinear effect controlled by the pyroelectricity. These experimental results are confirmed by a 3D digital model that takes into count the dynamic of the photorefractive effect. The temperature controlled optical revealed in this work can facilitate the demonstration of new concepts. Furthermore, the photo-induced technique associated opens new perspectives for 3D optical circuit in the LiNbO3, key for material photonic
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Fressengeas, Nicolas. "ETUDE EXPERIMENTALE ET THEORIQUE DE L'AUTO-FOCALISATION D'UN FAISCEAU LASER EN MILIEU PHOTOREFRACTIF : CONVERGENCES SPATIALE ET TEMPORELLE VERS UN SOLITON." Phd thesis, Université de Metz, 1997. http://tel.archives-ouvertes.fr/tel-00520187.

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CETTE THESE PROPOSE UNE MISE EN EVIDENCE THEORIQUE ET EXPERIMENTALE DE L'AUTO-FOCALISATION D'UN FAISCEAU LASER DANS PLUSIEURS ECHANTILLONS DE CRISTAL PHOTOREFRACTIF (BI#1#2TIO#2#0, SR#XBA#1#-#XNB#2O#6 ET BATIO#3). ELLE PROPOSE EN OUTRE D'ETUDIER COMMENT ET DANS QUELLES CONDITIONS L'AUTO-FOCALISATION PEUT CONDUIRE A LA PROPAGATION DE FAISCEAU NON-DIVERGENTS, C'EST-A-DIRE DE SOLITONS SPATIAUX. NOUS AVONS PU, GRACE A DES HYPOTHESES ADAPTEES A LA PROPAGATION DE SOLITONS SPATIAUX, DERIVER DU MODELE DE TRANSPORT PAR BANDE DE KUKHTAREV UNE EQUATION DE PROPAGATION DEPENDANT EXPLICITEMENT DU TEMPS. ELLE PERMET DE DECRIRE LA PROPAGATION DE TOUT PROFIL DE FAISCEAU RESPECTANT LES HYPOTHESES. NOUS AVONS ANALYSE CETTE EQUATION EN MONTRANT QU'ELLE PERMETTAIT LA PROPAGATION DE SOLITONS SPATIAUX, DONT NOUS AVONS ETUDIE LE COMPORTEMENT. NOUS AVONS EGALEMENT PU METTRE EN EVIDENCE DIVERS PHENOMENE QUE CETTE EQUATION DECRIT, TELS QUE LE BRANCHEMENT OPTIQUE. GRACE A LA CONCEPTION D'UN BANC EXPERIMENTAL ORIGINAL, NOUS AVONS OBSERVE LE PHENOMENE D'AUTO-FOCALISATION DANS LES TROIS CRISTAUX MENTIONNE CI-DESSUS, AINSI QUE DES PHENOMENE DE BRANCHEMENT OPTIQUE DANS BATIO#3. L'ANLYSE THEORIQUE CONDUITE CI-DESSUS NOUS PERMET D'AFFIRMER QUE NOUS AVONS OBSERVE LA PROPAGATION DE SOLITONS SPATIAUX PHOTOREFRACTIFS : L'EXPERIENCE A PERMIS DE VALIDER NOTRE MODELE THEORIQUE
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Benjelloun, Nadia. "Caracterisation des niveaux profonds dans le materiau photorefractif bi : :(12) geo::(20) par analyse de transitoires de courant photo-induit." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13183.

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La methode est utilisee pour l'etude de la densite d'etats dans la bande interdite du silicium amorphe hydrogene et sur cdin::(2)s::(4). La caracterisation des niveaux ayant des energies d'ionisation thermique entre 0,1 ev et 0,9 ev, le modele de transfert de charge decrivant l'effet photorefractif et l'evaluation du niveau de recombinaison, sont faits dans le materiau photorefractif. Les effets du dopage (fer) et du codopage (fer, vanadium) sur les niveaux sont consideres. Le centre responsable de la capture d'electrons est aussi etudie par absorption optique et photoconductivite photoinduites. Les resultats s'accordent avec ceux des mesures de photorefractivite
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Rouède, Denis. "Contribution a l'etude des reseaux de phase photoinduits dans un cristal de bi : :(12) si o::(20)." Paris 6, 1987. http://www.theses.fr/1987PA066206.

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Etat de polarisation de l'onde diffractee pour deux configurations transverses 110 et 001. On montre que la configuration 110 est tres bien adaptee au traitement d'images, alors que la configuration 001 est bien adaptee au couplage des ondes
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Haas, Helge. "Effet Stark quantique dans les puits de CdTe/CdZnTe et développement d'un dispositif photoréfractif." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10146.

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Nous presentons le developpement et l'etude d'un dispositif photorefractif a puits quantiques ainsi que les mecanismes physiques fondamentaux associes a ce type de composants. La structure de bande de type i pour les trous lourds et de type ii pour les trous legers permet une mesure precise du decalage de bande de valence de cdte/cd#. #7#2zn#0#. #3#8te egal a +11% 2%. Cette situation particuliere produit une degenerescence entre niveaux de trous lourds et trous legers. Dans les puits peu profonds, l'exciton leger est de type i grace au potentiel coulombien exerce par l'electron sur le trou leger. Sous champ electrique, nous mettons en evidence une transition type i-type ii de l'exciton leger. Lorsque l'energie de liaison de l'exciton augmente, la constante dielectrique et l'interaction des excitons avec le reseau diminuent. L'observation de complexes exciton-phonon a basse temperature et leur disparition progressive lorsque l'energie de liaison augmente est favorable a cette interpretation. Une absorption excitonique intense a temperature ambiante est cependant observee lorsque l'energie de liaison est proche ou superieure a l'energie des phonons optiques longitudinaux. En nous fondant sur ces resultats, nous avons developpe un dispositif photorefractif a partir d'une diode schottky et nous avons mesure un rendement de diffraction proche de la valeur theorique. Un maintien du reseau de diffraction inscrit de quelques microsecondes necessite un blocage des porteurs qui ecrantent localement le champ applique. L'introduction de barrieres de potentiel en cdmgznte bloquent efficacement le mouvement perpendiculaire des electrons. Un modele qualitatif et des simulations numeriques permettent de cerner le comportement dynamique du dispositif. La diffusion laterale a l'interface est acceleree par le gradient de potentiel entre zones eclairees et sombres et limite le temps de maintien du reseau. Par des mesures de type pompe-sonde, nous avons determine la diffusion laterale et sa dependance avec le champ applique
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Darracq, Bruno. "Etude de mecanismes de migration d'orientation moleculaire dans des films minces sol-gel : deformation de surface et proprietes optiques non-lineaires quadratiques." Phd thesis, Université Paris Sud - Paris XI, 1999. http://pastel.archives-ouvertes.fr/pastel-00713929.

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Cette these a pour cadre l'optimisation de films minces (1-10 microns) polymeres hybrides pour la realisation de composants passifs et actifs de l'optique integree. Nous avons plus precisement etudie la mobilite de molecules d'azobenzene soumises a des excitations electriques et photoniques dans deux types de matrices sol-gel : - dans une matrice faiblement reticulee, le processus de photo-isomerisation conduit a des phenomenes de migration moleculaire pouvant provoquer des deformations de surface spectaculaires (> 1 micron). Notre etude a porte plus particulierement sur la reponse du materiau vis-a-vis du de l'intensite, de la polarisation et des frequences spatiales de la figure d'illumination (franges d'interferences). On decrit aussi la realisation d'un coupleur a reseau, qui constitue l'un des composants passifs de l'optique integree. - dans une matrice fortement reticulee, l'orientation thermo-assistee des molecules d'azobenzene par un champ electrostatique applique au film permet de briser la centrosymetrie du materiau et de lui conferer des proprietes non-lineaires quadratiques. Les mecanismes d'orientation ont ete plus finement etudies en analysant l'influence de la concentration moleculaire sur l'efficacite du doublage de frequence par le materiau. On montre qu'un moyen d'ecranter les interactions dipolaires et ainsi d'augmenter notablement la mobilite des molecules actives est d'incorporer dans le materiau des groupements steriques passifs. Appliquee a des molecules optimisees par l'ingenierie moleculaire, cette strategie supramoleculaire a permis d'obtenir de forts coefficients electro-optiques stables a temperature ambiante et depassant ceux des meilleurs materiaux inorganiques (> 50 pm/v a 832 nm). Si de plus, les groupements steriques presentent des proprietes de photoconduction, on realise un materiau photorefractif. Nous avons analyse les proprietes originales d'un systeme presentant un effet photorefractif sans champ applique. .
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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.

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Le développement récent des fibres à large cœur quasi-monomodes a permis une montée en puissance rapide des lasers à fibre. En effet, l'utilisation d'un gros cœur permet de limiter les effets non linéaires indésirables et d'augmenter les seuils de dommage. Afin de poursuivre la montée en puissance, nous avons exploré une voie originale utilisant des fibres amplificatrices dopée Ytterbium à très large cœur, donc multimodes, suivies d'interactions non linéaires de remise en forme. Deux concepts ont été étudiés pour la restitution d'un faisceau limité par la diffraction :<br />- 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,<br />- 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.
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Books on the topic "Effet photorefractif"

1

J, Hall T., ed. The Photorefractive effect: A review. New York, 1985.

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Sturman, B. I. The photovoltaic and photorefractive effects in noncentrosymmetric materials. Gordon and Breach Science Publishers, 1992.

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Ryf, Roland. Optical parallel processing based on the photorefractive effect. 2000.

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Brülisauer, Simon. Control of the photorefractive effect in KNbO₃ by ion-implantation. 1998.

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Perreault, Nicki. Temperature dependence of the photorefractive effect in doped cadmium flouride. 1999.

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Nolte, David D., and N. M. Haegel. Photo-Induced Space Charge Effects in Semiconductors: Electro-Optics, Photoconductivity, and the Photorefractive Effect : Symposium Held April 29-May (Materials Research Society symposium proceedings). Materials Research Society, 1992.

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Photo-induced space charge effects in semiconductors: Electro-optics, photoconductivity, and the photorefractive effect : symposium held April 29-May 1, 1992, San Francisco, California, U.S.A. Materials Research Society, 1992.

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Book chapters on the topic "Effet photorefractif"

1

Powell, Andrew K., Trevor J. Hall, Hussain Imam, and David A. Fish. "The Photorefractive Effect." In Nonlinear Optics in Signal Processing. Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1560-5_4.

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Garrett, M. H., G. D. Fogarty, G. D. Bacher, R. N. Schwartz, and B. A. Wechsler. "The Photorefractive Effect in Ferroelectric Oxides." In Photorefractive Effects and Materials. Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-2227-0_2.

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Glass, Alastair M., and Jefferson Strait. "The photorefractive effect in semiconductors." In Topics in Applied Physics. Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/3-540-18332-9_35.

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Blanche, Pierre-Alexandre, and Brittany Lynn. "Introduction to the Photorefractive Effect in Polymers." In Photorefractive Organic Materials and Applications. Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29334-9_1.

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Kitayama, Ken-Ichi, and Fumihiko Ito. "Optical Signal Processing Using Photorefractive Effect." In Optical Signal Processing. Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-4006-9_7.

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Glass, A. M. "The Photorefractive Effect for Optical Processing." In Springer Proceedings in Physics. Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-46580-2_42.

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Klein, M. B. "Physics of the Photorefractive Effect in BaTiO3." In Springer Proceedings in Physics. Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71907-3_20.

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Montemezzani, G., C. Medrano, M. Zgonik, and P. Günter. "The Photorefractive Effect in Inorganic and Organic Materials." In Nonlinear Optical Effects and Materials. Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-540-49713-4_4.

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Smirl, A. L., G. C. Valley, M. B. Klein, K. Bohnert, and T. F. Boggess. "Picosecond Observation of the Photorefractive Effect in GaAs." In Springer Series in Chemical Physics. Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-82918-5_55.

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Wechsler, Barry A., Daniel Rytz, Marvin B. Klein, and Robert N. Schwartz. "Defect Properties and the Photorefractive Effect in Barium Titanate." In ACS Symposium Series. American Chemical Society, 1991. http://dx.doi.org/10.1021/bk-1991-0455.ch026.

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Conference papers on the topic "Effet photorefractif"

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Kamshilin, Alexei A., Hemmo Tuovinen, Victor V. Prokofiev, and Timo Jaaskelainen. "Fanning effect and phase conjugation in Bi12TiO20 photorefractive fiber." In The European Conference on Lasers and Electro-Optics. Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.ctuc7.

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Study of photorefractive phase conjugate mirror is of great importance on account of various practical applications, such as optical implementation of neural network, associative memories, synchronization of several isolated lasers, interferometry, etc. A double phase conjugate mirror (DPCM) offers more advantages because no coherence between laser pump beams is needed. BSO-type crystals represent an important class of photorefractive materials due to their fast response time? Fiber-like samples have several advantages compared to the bulk crystal.2 We present here an experimental investigation of the double phase conjugation and of the fanning effect in fiberlike photorefractive Bi12TiO20 (BTO) crystal supplied by alternating electric field of square-wave form at the wavelength of He-Ne laser (λ = 632.8 nm). It was found that features of photorefraction in fiber-like samples are quite different with bulk crystals.
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Roorda, Austin, William R. Bobier, and Melanie C. W. Campbell. "The Effect of the Eye's Chromatic Aberration on Eccentric Photorefraction." In Ophthalmic and Visual Optics. Optica Publishing Group, 1993. http://dx.doi.org/10.1364/ovo.1993.osac.2.

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Photorefraction describes a family of techniques used to measure the refractive state of the eye. The technique is commonly used for children or uncooperative subjects whose limited attention span prevents accurate measurements using the traditional techniques, such as retinoscopy. The technique can be separated into two methods, eccentric and coaxial photorefraction. All methods employ a small light source at a camera which is directed toward the eye. Some of the light reflected back from the eye enters the camera aperture. The result is a photorefracted pattern whose size is determined by the parameters of the experiment, particularly the refractive state of the eye and the pupil size. Both methods have limited working ranges and a dead zone in which changes in refractive error cannot be measured.
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Kwong, Norman S. K. "Optical Tracking Filter via Transient Energy Coupling Effect." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.thc7.

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Recently there are extensive studies conducted on the phenomenon of steady state two-beam coupling in photorefractive media with the induced index grating π/2 phase shifted from the light interference pattern. However very little attention is paid to the transient energy coupling (TEC) effect in "unshifted" holographic media, such as photorefractive crystal operating in the 'charge drifting' mechanism, and some χ(3) media, etc.. This paper investigates the TEC effect and apply this effect to an optical tracking filter.
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Strohkendl, F. P., P. Tayebati, and R. W. Hellwarth. "A Comparative study of the photorefractive effect in Bi12SiO20 Crystals." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.wb1.

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We perform beam-coupling and erasure experiments in four different nominally undoped Bi12SiO20 (BSO) crystals. We use the theory of electron-hole competition1,2 in photorefractive gratings to analyze our data. We determine the diffusion- lengths Ke−1, Kn−1 for electrons and holes, the ratio S of hole to electron absorption, the Debye screening wavevector ko, the total absorption coefficient and the quantum efficiency.
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Michel-Calendini, F. M., and G. Godefroy. "Possible iron and associated centers responsible of the photorefractive effect in BaTiO3." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.wa5.

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A recent paper by Klein and Schwartz (1) discuss the photorefractive effect mechanisms (PRE) in commercial BaTiO3 samples in terms of Fe2+ and Fe3+ impurities. The results of various experimental techniques (RPE, beam compling, absorption) lead them to conclude that the usual two level model involving the Fe2+ to Fe3+ conversion is sufficient to explain PRE. As their interpretations invoke molecular orbital calculations relevant to iron centers in various perovskite hosts (see ref.2 for instance), a more complete study of the electronic structures of possible centers responsible of PRE in BaTiO3 is presented in this paper. To this end, we report in figure 1 the electronic levels of Fe2+, Fe3+ ions trapped in tetragonal BaTiO3 as well as the ones relevant to neutral and single ionized oxygen vacancies. The calculations are based on the MS-Xx method as described in ref. 2. They assume that iron substitutes exactly Ti4+ in its tetragonal site, without additional relaxation or distortion of the lattice around the impurity ; near a Vo site, Ti4+ is assumed to be displaced by about 0.2A° towards Vo. We concentrate now on the possible centers responsible of PRE.
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Brost, G. A., R. A. Motes, J. R. Rotge’, and J. J. Kim. "A Model for Intensity Dependent Absorption and Photorefractive Effect in BaTiO3 Crystals." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.pd4.

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Intensity dependent absorption and photorefractive effects have recently been observed at low intensities in barium titanate crystals [1, 2]. Also, there is some evidence that recombination centers other than iron impurities exist in BaTiO3 and contribute to the photorefractive effect [3, 4]. The model we present here assumes the existence of primary deep level traps such as iron and secondary shallow traps as shown in Fig. 1. We show that this model predicts the intensity dependence in BaTiO3.
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Krolikowski, W., and M. Cronin-Golomb. "Lead germanate: a new photorefractive material." In OSA Annual Meeting. Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.mcc4.

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We present a new promising photorefractive crystal: lead germanate Pb5Ge3O11. This crystal is ferroelectric and has trigonal symmetry. The crystal itself has been studied before and most of its physical properties are well known. However, to our knowledge, the occurrence of photorefraction in this material has not been reported before. Large (0.9 cm × 0.8 cm × 0.43 cm) samples of Pb5Ge3O11 exhibit absorption of 1.5 cm−1 and optical activity of 8° /mm for green light (514.5 nm). Both parameters are smaller than in commonly used BSO crystal whose optical activity is almost 5 times as large. Since the largest electrooptic coefficient r33 is 15 pm/V compared with 5 pm/V for BSO, this crystal seems to be really interesting as a candidate for holographic recording medium. We studied the photorefractive properties of lead germanate in a conventional two-beam coupling experiment. We found that photorefraction occurs for all argon-ion lines and is strongest for λ = 514.5 nm. Weaker photorefractive sensitivity was found for red light. Therefore we used a He-Ne laser beam to read out the grating written by two green beams. In two-beam coupling measurements we obtained a photorefractive intensity gain coefficient of Γ = 1.46 cm−1. The time constant for grating formation was ~1 s for a total writing beam intensity of 200 mW/cm2. In our experiments we saw the effect of hologram fixing under long illumination. For short exposure the grating was completely erasable. We also studied the influence of external electric dc fields on the grating properties. It was found that an electric field of 5 kV/cm significantly improved the diffraction efficiency (5 times). Switching of this field leads to interesting transient behavior of the diffracted beam intensity (strong oscillations).
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Agranat, A., and Y. Yacoby. "The Dielectric Photorefractive Effect: A New Photorefractive Mechanism." In Sixth IEEE International Symposium on Applications of Ferroelectrics. IEEE, 1986. http://dx.doi.org/10.1109/isaf.1986.201092.

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Agranat, Aharon, Koichi Sayano, and Amnon Yariv. "Photorefractive Diffraction Gratings in KTN:Cr, Fe in the Paraelectric Phase Using the Quadratic Electrooptic Effect." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.pd1.

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Potassium tantalate niobate (KTN) was one of the first photorefractive (PR) crystals to be discovered(1,2,3). However since its discovery, very little has been done in order to explore its PR properties. The chemical composition of KTN is given by KTa1−xNbxO3 where x denotes the niobium concentration. KTN undergoes a ferroelectric phase transition at a temperature Tc which depends on x (roughly 8.5K/1% per mole of Nb). For low Nb concentrations the phase transition is second order and it becomes first order for x ≥ 0.3.(4)
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Jonathan, J. M. C., G. Roosen, and Ph Roussignol. "Time resolved build-up of the photorefractive effect produced in Bi12SiO20 by picosecond light pulses." In Photorefractive Materials. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/prm.1987.tha4.

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Reports on the topic "Effet photorefractif"

1

Ducharme, S., J. C. Scott, R. J. Twieg, and W. E. Moerner. Observation of the Photorefractive Effect in a Polymer. Defense Technical Information Center, 1990. http://dx.doi.org/10.21236/ada231339.

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Anderson, Dana Z. Applications of the Photorefractive Effect and Damage Induced Effects in Fibers. Defense Technical Information Center, 1992. http://dx.doi.org/10.21236/ada264339.

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