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Dissertations / Theses on the topic 'Optical phase conjugation'
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Schroeder, W. A. "Optical phase conjugation by stimulated Brillouin scattering." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46505.
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Bor, Sheau-Shong. "Phase conjugation characteristics of Gaussian beam /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262825076392.
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Anikeev, Igorʹ Yu. "Study of limiting factors and methods of optical phase conjugation by stimulated Brillouin scattering." Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pha597.pdf.
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Includes bibliographical references (leaves 205-227) A study of phase conjugation by stimulated Brillouin scattering is presented with emphasis on the limiting factors, such as aperture and polarization losses, spatial coherence and saturation of the incident wave on the quality of phase conjugation, as well as the application of stimulated Brillouin scattering to loop phase-cojugated mirror and intracavity-SBS-cell-phase-conjugated oscillator.
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HOLM, DAVID ALLEN. "QUANTUM THEORY OF MULTIWAVE MIXING (RESONANCE FLUORESCENCE, SATURATION SPECTROSCOPY, MODULATION, PHASE CONJUGATION, QUANTUM NOISE)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187980.
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This dissertation formulates and applies a theory describing how one or two strong classical waves and one or two weak quantum mechanical waves interact in a two-level medium. The theory unifies many topics in quantum optics, such as resonance fluorescence, saturation spectroscopy, modulation spectroscopy, the build up of laser and optical bistability instabilities, and phase conjugation. The theory is based on a quantum population pulsation approach that resembles the semiclassical theories, but is substantially more detailed. Calculations are performed to include the effects of inhomogeneous broadening, spatial hole burning, and Gaussian transverse variations. The resonance fluorescence spectrum in a high finesse optical cavity is analyzed in detail, demonstrating how stimulated emission and multiwave processes alter the spectrum from the usual three peaks. The effects of quantum noise during the propagation of weak signal and conjugate fields in phase conjugation and modulation spectroscopy are studied. Our analysis demonstrates that quantum noise affects not only the intensities of the signal and conjugate, but also their relative phase, and in particular we determine a quantum limit to the semiclassical theory of FM modulation spectroscopy. Finally, we derive the corresponding theory for the two-photon, two-level medium. This yields the first calculation of the two-photon resonance fluorescence spectrum. Because of the greater number of possible interactions in the two-photon two-level model, the theoretical formalism is considerably more complex, and many effects arise that are absent in the one-photon problem. We discuss the role of the Stark shifts on the emission spectrum and show how the Rayleigh scattering is markedly different.
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Devrelis, Vladimyros. "Fidelity of optical phase conjugation using stimulated brillouin scattering /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phd514.pdf.
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Ridley, Kevin Dennis. "Novel phase conjugation techniques based on stimulated Brillouin scattering." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282087.
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Kaczmarek, M. "Dynamics of resonant degenerate four-wave mixing and applications in gaseous media." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291286.
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Smout, A. M. C. "Studies of novel photorefractive behaviour in self-pumped barium titanate." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233022.
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Lindsay, Iain. "Optical phase conjugation in photorefractive materials and its application to image processing." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47541.
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Bach, Tobias. "Optical phase conjugation for laser beam clean-up with Sn₂P₂S₆ crystals /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17826.
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Tang, Xuefeng. "Optical phase conjugation and its application in the compensation of fiber Kerr nonlinearities." Lorient, 2005. http://www.theses.fr/2005LORIS052.
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Avec l'augmentation du débit et du nombre de canaux dans les télécommunications optiques, la non linéarité de la fibre, en particulier l'effet de Kerr, est considérée comme une des limitations les plus importantes de la performance au niveau de la transmission. La conjugaison de phase optique (OPC, optical phase conjugation), une technique optique non-linéaire, reçoit de plus en plus d'attention grâce à sa capacité à compenser la dispersion, ainsi que les effets non linaires. Dans cette thèse, nous étudions le processus de la compensation pour les effets non linéaires, incluant l'auto-modulation de phase, la modulation de phase croisée, l'interaction non-linaire intra canal, l'amplification non-linaire du bruit dans le système OPC. Il est démontré que l'OPC a une capacité de compenser efficacement les effets non linéaires, pourtant sa performance de compensation est influencée considérablement par plusieurs facteurs tels que la symétrie de l'évolution du signal, le régime de la dispersion et la configuration de la liaison. Avec l'optimisation pour la carte de dispersion, la performance de l'OPC peut être fortement améliorée, ce qui facilite la mise en œuvre de schéma de multiplexage soit par TDM ( time-division-multiplexing ), soit par WDM (wavelength-division-multiplexing). De plus, à partir de l'étude de l'effet de réglage de la température sur le processus QPM-DFG (quasi-phase-matching difference-frequency generation) basé sur un cristal de PPLN ( periodically poled LiNbO3), nous proposons une méthode de réglage correspondant aux différentes zones de température du PPLN pour améliorer la performance du QPM-DFG<br>With the increase of the bit rate and channel number in optical fiber communications, the fiber nonlinearity, especially the Kerr nonlinearity, has been reconsidered as one of the most important limitations on the transmission performance. As an important nonlinear optical technique, optical phase conjugation (OPC), has been paid increasing attention due to its ability to compensate for the dispersion and the nonlinear effects in fiber transmissions. In this dissertation, we investigate the compensation process of nonlinear effects, including self-phase modulation (SPM), cross-phase modulation (XPM), intrachannel nonlinear interaction and nonlinear noise amplification in OPC systems, using theoretical analysis and numerical simulations. It is shown that OPC has a very promising ability to compensate for the fiber nonlinearities, while its performance is affected by some factors such as the signal evolution symmetry, the dispersion regime and the fiber-link configuration. With the optimization of the dispersion map design (fiber-link configuration), the compensation performance of OPC can be improved considerably, which shows a very attractive implementation in either time division multiplexing (TDM) or wavelength division multiplexing (WDM) schemes. In addition, we have made a contribution to the study of the temperature tuning effect on the quasi-phase-matching (QPM) difference-frequency-generation (DFG), and a multi-segment temperature tuning method is proposed to optimize the QPM-DFG performance
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KARAGULEFF, CHRIS. "DEGENERATE FOUR WAVE MIXING IN THIN FILM OPTICAL WAVEGUIDES (NONLINEAR OPTICS, INTEGRATED, PHASE CONJUGATION, SIGNAL PROCESSING)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187908.
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The incentive for conducting Degenerate Four Wave Mixing (DFWM) within guided wave devices is two-fold: (1) By coupling the optical beams into guided wave devices, the optical power densities can be increased orders of magnitude due to the tight confinement of the beams. Such an increase in power density means a concomitant increase in conversion efficiency of the signal beam. (2) The potential signal processing applications of DFWM (logic gates, switching, correlation/convolution), particularly for ultra-fast serial processing, would be better exploited, and adjoined to existing integrated circuit technology, by such an integrated optic/guided wave approach. In this dissertation we describe experiments and present data confirming the presence of DFWM within a planar glass thin film with carbon disulphide as the nonlinear cover medium. Optical pulses from a Q-switched, frequency doubled Nd:YAG laser are coupled into the glass film. The nonlinear polarization required to produce the desired conjugate signal is generated within the CS₂ by the evanescent tails of the guided input beams as they probe the nonlinear cover medium. The signals measured agree well with theory, but because they were so small in magnitude, signal-to noise ratios were small due to stray background radiation scattering from beamsplitters and other associated optics. Additionally, recent studies (Jain & Lind, 1983) indicate nonlinear responses in semiconductor (CdS/Se) doped glasses, commercially available as color glass filters, that are orders of magnitude higher than corresponding nonlinearities within CS₂, in addition to possessing subnanosecond response times. We have performed experiments upon such glasses in an effort to fabricate nonlinear optical waveguides within them via ion-exchange techniques. We have successfully fabricated single mode planar guides, but they are currently too lossy to allow demonstration of any guided wave nonlinearities. Also, we describe experiments in which we have measured (bulk) DFWM grating lifetimes with greater precision than previously reported. Results indicate a fast (20 to 50 pico-seconds, depending on the particular glass) electronic response, superimposed upon, but clearly distinguishable from, a slower (10's of nanoseconds) thermal response.
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Rousseau, Emmanuel. "Efficient, fast, low power, optical phase conjugation using two-photon-induced Zeeman coherence in rubidium." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/47402.
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Sayano, Koichi Yariv Amnon. "Photorefractive properties of ferroelectric materials for optical phase conjugation, two-beam coupling, and holographic storage /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-11072006-135048.
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Knittle, James Eugene. "Bioanalytical and photophysical applications of sensitive nonlinear wave-mixing spectroscopy based on laser-induced gratings /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3138952.
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Liu, Siuying Raymond. "Spatiotemporal behavior and nonlinear dynamics in a phase conjugate resonator." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40099.
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The work described in this dissertation can be divided into two parts. The first part is an investigation of the transient behavior and stability property of a phase conjugate resonator (PCR) below threshold. The second part is an experimental and theoretical study of the PCR's spatiotemporal dynamics above threshold.
The time-dependent coupled wave equations for four-wave mixing (FWM) in a photorefractive crystal, with two distinct interaction regions caused by feedback from an ordinary mirror, was used to model the transient dynamics of a PCR below threshold. Analytical expressions of the steady state cavity's fields for the case of nondepleted pumps and an absorption free medium were derived and used to determine the self-oscillation conditions. The solutions, through simple frequency domain transformation techniques, were used to define the PCR's transfer function and analyse its stability.
Taking into account pump depletion and medium absorption, the transient buildup and decay times of the cavity's fields as well as the specularly reflected and phase conjugate reflected intensities were numerically calculated as functions of a number of system parameters such as the coupling parameter and the pump and probe ratios. General trends were unveiled and discussed in view of the possible use of the PCR in image storage or processing architectures. Experimental results for the buildup and decay times confirmed qualitatively the predicted behavior.<br>Ph. D.
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Lo, Kanwai Peter. "Iterative image processing using a cavity with a phase-conjugate mirror: possibilities and limitations." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39777.
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An optical image feedback system utilizing a cavity with a phase-conjugate mirror (PCM) has been studied. A new theory, based on operators, is developed to describe the steady-state output of the cavity. The use of operators allows one to describe the various optical operations and transformations needed in the optical implementation of iterative algorithms. The characteristics of the cavity are discussed using an expansion of the cavity fields in the cavity eigenfunctions.
Several image processing applications using a PCM cavity are proposed and are studied using computer simulations. These theoretical studies indicate that a PC11 cavity can be useful in many applications.
Optical phase conjugation was realized using a single crystal of photorefractive BaTi0₃ in a degenerated four-wave mixing geometry. The reflectivity gain from the PCM was optimized experimentally by the geometrical parameters and by the beamintensity ratios. The ability of the PCM to remove phase distortion as predicted theoretically, was demonstrated experimentally.
The output of a PCM cavity can be substantially influenced by self-oscillations of the cavity above threshold. This was experimentally studied by observing the time evolution of the input. To avoid the influence of self-oscillation, the cavity must be operated below threshold. It is found that the cavity decay time constant diverges at and about threshold. This can be used as an indicator to show whether the cavity has crossed the threshold or to measure how close to threshold the cavity operates.
To verify that a PCM cavity can be used in iterative image processing, an experiment was set up to implement an image restoration scheme based on the Gerchberg algorithm. It is shown that an optical implementation of the Gerchberg algorithm is feasible for objects made of few pixels. The experiment confirmed .that image iteration in a PCm cavity is possible. The limitations of the cavity and the technical difficulties are discussed.<br>Ph. D.
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Faulkner, Helen Mary Louise. "Studies in phase and inversion problems for dynamical electron diffraction." Connect to thesis, 2003. http://repository.unimelb.edu.au/10187/2880.
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This thesis examines problems in electron diffraction and related areas of theoretical optics. It begins with a study of the phase of a quantum mechanical wave function and the behaviour of phase vortices and vortex cores. Several rules for vortex core evolution are given and simulated vortex trajectories are studied. These simulations show that in electron microscopy at atomic resolution and in other similar situations, vortices occur in the wave functions very frequently. This means any image processing methods which deal with the wave function phase must permit vortices to occur. In this context a number of methods of phase retrieval are compared and evaluated. The criteria of evaluation are the accuracy of the phase retrieval, its ability to cope with vortices, its numerical stability and its required computational resources. The best method is found to be an iterative algorithm similar in approach to the Gerchberg-Saxton method, but based on a through focal series of images.<br>Using this phase retrieval method as an essential tool, the thesis continues with a study of inverse problems in electron optics. The first problem considered is that of using a set of images taken to characterise the coherent aberrations present in a general imaging system. This problem occurs in many areas of optics and is studied here with a focus on transmission electron microscopy. A method of using software to simultaneously determine aberrations and subsequently remove them is presented and tested in simulation. This method is found to have a high level of accuracy in aberration determination. The second inverse problem studied in this thesis is the inversion problem in dynamical electron diffraction. This problem is solved for a periodic object, giving an accurate and unique solution for the projected potential in the multiple scattering case. An extension of this solution to objects which are non-periodic in the direction of the incident wave is investigated. Finally a model computation solving the general inversion problem for dynamical diffraction in an aberrated transmission electron microscope is performed, illustrating this and previous material and summing up the advances presented in this work.
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Karsaklian, dal Bosco Andreas. "Chaos and high-frequency self-pulsations in a laser diode with phase-conjugate feedback." Phd thesis, Supélec, 2013. http://tel.archives-ouvertes.fr/tel-00963630.
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This thesis is a theoretical and experimental study of the dynamics of an edge-emitting laser diode (850 nm) with phase-conjugate feedback. The experimental device is designed to see the dynamical range of the laser through the temporal and spectral properties while the feedback rate varies. Phase-conjugate feedback is performed through four-wave mixing in a photorefractive crystal. The propagation time of the laser beam in the external cavity is termed external time delay. Under the effect of the feedback, the system shows a wide dynamical range including chaos and self-pulsing states which characteristic properties are determined by the length of the external cavity. For the first time self-pulsing states at frequencies multiples of the fundamental frequency of the external cavity are evidenced. Simulations carried out based on the commonly-used Lang-Kobayashi laser rate equations provide theoretical confirmations to the experimental observations. The main topics tackled here are chaos crisis and bistability of pulsing solutions, self-pulsing regimes (through their stabilization and destabilization) and the transitions between them, characterization of extreme events of two kinds along with their statistical distribution and delay-induced deterministic coherence resonance of low frequency fluctuations. Beyond the fundamental interest of these results and the many comparisons that can be made with other laser systems, applications in the field of all-optical signal generation and control of chaos are direct consequences of this study.
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Leggatt, Jonathan Stewart. "Phase conjugation using COâ†2 lasers." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292686.
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Fahmi, Abdelilah. "Contrôle des effets non linéaires dans des liquides en mélange d'ondesApplication à la mesure de la susceptibilité non linéaire et à la conjugaison de phase." Angers, 1995. http://www.theses.fr/1995ANGE0022.
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La mesure des susceptibilités non linéaires d'ordre 3 dans des matériaux nécessite une bonne maitrise de l'ensemble des non-linéarités apparaissant dans ces matériaux en particulier dans les expériences faites en mélanges d'ondes. L'étude présentée est consacrée à la maitrise des non-linéarités dans des matériaux de référence. Nous avons montré la présence d'une diffusion Rayleigh stimulée des cs#2 et des absorptions linéaire et non linéaire dans c#6h#5no#2. Ces effets diminuent considérablement la réflectivité de conjugaison de phase par mélange quatre ondes dégénéré. L'analyse théorique et la démonstration expérimentale de ces processus sont présentées. On a observé que les effets de couplages pompe/sonde dans le cas de la diffusion Rayleigh stimulée dépendent de l'angle entre l'onde pompe et l'onde sonde. On a de plus montre l'effet des gradients transverses de champ dans les mesures. Les absorptions linéaire et non linéaire observées produisent un échauffement du matériau qui conduit à la formation d'une onde acoustique. Nous avons analysé les répercussions de cette onde acoustique sur les mesures de la susceptibilité non linéaire. Les résultats obtenus permettent d'envisager, par exemple, des applications a la mesure de la partie réelle de la susceptibilité non linéaire par mélange d'ondes dans des matériaux organiques nouveaux qui peuvent être absorbants ou diffusants et ou l'ordre de grandeur de la non-linéarité d'indice est inconnu à l'avance.
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Martel, Gilles. "Etude de l'effet photoréfractif dans la tellure de cadmium : application à l'interconnexion en espace libre par double miroir à conjugaison de phase." Rouen, 1996. http://www.theses.fr/1996ROUES076.
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Cette thèse traite des propriétés électroniques et optiques, ainsi que des applications en holographie dynamique (photoréfractivité) du tellure de cadmium et de ses alliages à base de zinc. La caractérisation s'est orientée vers l'alliage photoréfractif le plus prometteur : le Cd1-xZnxTe dopé V avec 0x%)4. La croissance retenue pour la réalisation de ces matériaux fut la méthode Bridgman verticale asymétrique. La caractérisation photoréfractive par la technique du mélange à deux ondes nous a permis de sélectionner les matériaux qui autorisent les rendements de diffraction les plus favorables à la conjugaison de phase. Nous avons pu mettre en évidence différents types de comportements photoréfractifs sous champ électrique externe nul, continu ou alternatif (jusqu'à 14 kV/cm). L'existence de ces différents comportements est assujetti à la présence ou non de zinc. Deux modelés considérés comme des extensions de la théorie photoréfractive classique, et dont la limite de validité fut précisément définie par les analyses spectroscopiques des défauts profonds dans un cristal (DLTS, DLOS, PICTS, ODMR, MCD, RPE, effet Hall, photoluminescence et absorption), ont été développés afin de proposer une explication claire des différents processus détectés. Parallèlement à cette étude sur la compréhension du matériau, un démonstrateur de commutateur optique reconfigurable a été développé entre fibres monomodes. Basé sur l'utilisation d'un double miroir à conjugaison de phase (DPCM), ce commutateur a été réalisé à la longueur d'onde de 1. 5 m. Des temps de reconfiguration (cycle effacement-écriture d'un réseau holographique de Bragg photoinscrit) de l'ordre de 10 millisecondes ont été mesurés pour ce démonstrateur à commutation lente. De nombreux problèmes dynamiques (instabilités, franges mobiles) ont été mis en évidence au sein de ce matériau en configuration DPCM et également en configuration miroir à conjugaison de phase en anneau (ring PCM). Une théorie basée sur les ondes couplées a permis de rendre compte de l'aspect fondamental et donc général de la dynamique (franges mobiles) qui existe au sein d'un grand nombre de miroirs à conjugaison de phase.
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Le, Bihan Eric. "Mélange à deux ondes et mélange à quatre ondes dans la vapeur de sodium : effets d'auto-oscillation." Paris 6, 1986. http://www.theses.fr/1986PA066235.
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Lamb, Robert Andrew. "The application of phase conjugation to high power lasers using stimulated Brillouin scattering." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262650.
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Korwan, Daniel R. "Spatiotemporal dynamics of a photorefractive phase-conjugate resonator." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-152143/.
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Catunda, Tomaz. "Conjugação de fase e modulação transversal de fase em cristais dopados com Cr+3." Universidade de São Paulo, 1989. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-21052007-100620/.
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Neste trabalho estudamos teórica e experimentalmente o efeito de Conjugação de Fase por Mistura Degenerada de Quatro Ondas (CFMD40) e Modulação Transversal de Fase em cristais dopados com Cr+3. Estudamos a CFMD40 em Al2O3:Cr+3 (rubi) e GdAlO3:Cr+3 com um laser de Ar (em λ=514nm) obtendo um bom acordo entre os resultados experimentais e os teóricos (nestes cálculos usamos os valores de n2 de um trabalho anterior [1]). O modelo teórico que fizemos explica muito bem o comportamento de saturação da eficiência da CFMD40 que não era compreendido em trabalhos anteriores [47,48.2]. Usando os mesmos valores de n2 obtivemos um bom acordo entre os resultados experimentais e teóricos para o efeito de Modulação Transversal de Fase. Também fizemos um modelo teórico para o efeito de Modulação Transversal de Fase em CFMD40 que explica nossas observações [2]. A não linearidade destes materiais foi investigada usando-se três técnicas experimentais diferentes [1.2] e por dois outros grupos [61.62] (para o rubi) através de mistura de duas ondas não degeneradas. Todas estas medidas estão em bom acordo. Na alexandrita (BeAl2O 4:Cr+3) estudamos o espectro de χ(3) (ou n2) em ressonância das linhas R. Nos atribuímos a forma assimétrica do espectro como sendo oriunda de duas contribuições para susceptibilidade, onde um termo é devido a interação ressonante com o sistema de dois níveis e o outro devido a mudança de polarizabilidade causada pela população do estado excitado (esta é a primeira vez que este efeito foi observado).<br>In this work we studied theoretical and experimentally the effects of Phase Conjugation by Degenerate Four Wave Mixing and Transversal Phase (PCD4WM) Modulation in Cr+3 doped crystals. We studied the PDC4WM in Al2O3:Cr+3 (ruby) and GdAlO3:Cr+3 with on Ar laser (at λ= 514 nm) and obtained a good agreement between our experimental and theoretical results (in these ca1culations we used the nonlinear refractive index n 2 values from a previous paper [1]. The theoretical model that we developed explains very well the saturation behaviour of the PDC4WM efficiency that was not understood in previous papers [47.48,2]. These values of n2 are also in good agreement with our results in Transverse Phase Modulation. We also developed a theoretical model for the effect of Transverse Phase Modulation in PCDFWM that explains our observations [2]. The nonlinearity ?n IND.2? from these materials was investigated by us using three different techniques [1.2], by other two groups [61.62] (for the ruby) in nondegenerate two-wave mixing and all those measurements are in good agreement. In alexandrite (BeAl2O4:Cr +3) we studied the χ(3) (or n2) spectrum in resonance with the R lines. We attributed the asymetric shape of the spectrum by the effect of two differents contributions, one term due to the resonant interaction of the two-level system and the other due to the polarizability change caused by excited state population (this is the first observation of this kind of effect.
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Souza, Paulo Cesar de. "Estudo de Efeitos Transientes na Conjugação de Fase em Cristais Dopados com \'Cr POT. 3+\': Modelo e Experiência." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-05082013-115037/.
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Nós estudamos experimentalmente e teoricamente Efeitos Transientes em conjugação de Fase por Mistura Degenerada de Quatro ondas em cristais dopados com Cr POT. 3+. Estudamos os efeitos transientes na conjugação de fase em Al IND 2 O IND. 2 : Cr POT. 3+ (Rubi) e GdAl O IND. 3 Cr POT. 3+ (aluminato de gadolíneo) com um laser de Ar POT. + (em =514,5nm). Um novo modelo teórico é apresentado que explica razoavelmente os resultados experimentais cuja compreensão anterior pela literatura era devido somente pela parte absortiva do índice de refração[12] pois em cristais dopados com Cr POT. 3+ (Al IND. 2 O IND. 3: Cr POT. 3+ e GdAl O IND. 3 : Cr POT. 3+ a parte dispersiva do índice de refração não-linear n IND. 2 é pelo menos uma ordem de grandeza maior que a parte absortiva [15,28].<br>We have studied experimentally and theoretically Transient Effects in Degenerate Four-Wave Mixing by Phase Conjugation in ion-doped crystals with Cf3+. We have studied transient effects in phase conjugation in Al2O3:Cf3+ (Ruby) and GdAlO3:Cr3+ Gadolinium Aluminate) with an Argon laser (at =514.5nm). A new theoretical model is presented that reasonably explains our experimental results whose understanding in previous papers was due to the imaginary part of the refraction index [12] because in crystals doped with cr3+ (Al2O3:Cr3+ and GdAIO3:Cr3+) the real part of the nonlinear refraction index n2 is at least one order of magnitude greater than the imaginary part [15,28].
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Er-Rhaimini, Salih. "Reconstruction d'image par rétrodiffusion stimulée Raman et amélioration du rendement de conversion." Angers, 1995. http://www.theses.fr/1995ANGE0007.
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La rétrodiffusion Raman stimulée peut être utilisée pour différentes applications, en particulier la fabrication des fréquences laser nouvelles et conjugaison de phase. Dans notre travail, nous montrons qu'il est possible de transférer sur le rayonnement Raman stimule l'image d'un objet éclairé par un faisceau laser avec de bons rendements de conversion. Nous améliorons d'abord le rendement de rétrodiffusion en choisissant des matériaux actifs (exemple : l'acétone) et des conditions géométriques d'excitation convenables. Nous trouvons les conditions géométriques et énergétiques pour un bon transfert d'image et montrons que deux phénomènes jouent un rôle important dans la reconstruction d'image : l'amplification Raman, et la relation de phase entre ondes laser et Raman. Nous montrons le rôle possible des variations non linéaires de l'indice de réfraction qui peut accompagner l'effet Raman. Nous proposons des applications en particulier à la visualisation d'objets de phase et a l'étude de la cohérence de la diffusion Raman.
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Lavoine, Jean-Pascal. "Role de la dynamique d'un milieu non lineaire en melange a quatre ondes." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13223.
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Etude du role de la dynamique des materiaux en optique non lineaire et analyse de la formation et de la propagation de l'onde conjuguee lors d'une experience de conjugaison de phase realisee avec des champs impulsionnels. Description theorique des melanges a quatre ondes dans le formalisme de la matrice densite. Celle-ci est obtenue par un traitement en perturbation, le milieu etant modelise par n systemes a deux niveaux. Cette etude est le point de depart de l'analyse du melange a quatre ondes en termes de reseaux. Apres avoir donne une expression analytique de l'onde conjuguee, les conditions optimales pour obtenir un reversement d'enveloppe ont ete etablies
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Huang, Yi-An, and 黃奕安. "PSTD analysis of optical phase conjugation." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/17720021234908478675.
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碩士<br>國立臺灣大學<br>光電工程學研究所<br>100<br>In the thesis, we show the development of a simulation tool for optical phase conjugation (OPC) phenomenon. We use the pseudospectral time-domain (PSTD) algorithm to implement our OPC simulation. The PSTD simulation is computationally efficient and memory-economic, enabling accurate modeling of the OPC phenomenon of light penetration through large-scale turbid media.
In PSTD algorithm, however, we have a few problems to cope with, including the construction of a light source and an OPC mirror. To avoid the hard-source artificial reflection, a light source is implemented by soft sources. Also, the Gibbs’ phenomenon causes overshoots on the boundary of a soft source. Therefore, we broaden the width of the soft source to reduce the spatial frequency of the input signal. The overshoot noises are eliminated. With these problems solved, the PSTD simulation of OPC phenomenon is robust and error-controllable.
The PSTD simulation of OPC phenomenon is divided into two parts as the OPC experiment: the forward and playback scenarios. In the forward scenario, we record the phasor of light scattered by turbid media; in the playback scenario, we emit the recorded scattered light with its phase conjugated and Poynting vectors inverted. The phase-conjugated light penetrates through the turbid media and focus at the location of the original source.
By increasing the simulation scale, we can apply the OPC phenomenon to a macroscopic, biological tissue. To speed up the macroscopic simulation, we develop an PSTD simulation of OPC phenomenon with parallel computation, distributing the computation work and data to different CPUs and computer memories, respectively. The time consumption of the OPC simulation reduces as the number of CPUs increases.
We develop an efficient simulation technique to model the OPC phenomenon using the PSTD analysis. In the simulation, the phasors of light scattered by turbid media are recorded by the OPC mirror. With these phasors, the OPC mirror emits phase-conjugated light. The light penetrates through the turbid media and focuses at where it originated. As for future applications, our goal is to deliver light to arbitrary location within the turbid media by the OPC simulation. With the progressive tomography of a biological tissue, the development of a non-invasive OPC treatment is promising.
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Jayanth, P. "Photorefractive Crystals : Optical Phase Conjugation And Phase Conjugate Interferometry." Thesis, 1996. https://etd.iisc.ac.in/handle/2005/1590.
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Jayanth, P. "Photorefractive Crystals : Optical Phase Conjugation And Phase Conjugate Interferometry." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1590.
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Dung, Jeng-Cherng, and 董正成. "Optical soliton transmission with filters and optical phase conjugation." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/39684676006729537597.
Full textAbstract:
博士<br>國立交通大學<br>光電工程研究所<br>84<br>In this thesis, we mainly study the optical soliton
transmission system with filters and optical phase
conjugation. The four wave mixing effect in a wavelength-
division-multiplexing soliton transmission system is also
presented as an additional contribution.
Both methods can be used to improve the soliton transmission.
One is touse a filter after each optical amplifier. The filter
with fixed centerfrequency stabilizes the carrier frequency of
the soliton and the maximumbit rates limited by the stability,
soliton interaction, and Gordon-Haus effect are obtained in
different distance. Furthermore, we show the effectsof the up-
sliding and down-sliding frequency filter on the soliton
interactionand propose the most effective zigzag-sliding
frequency guiding filter ofwhich the center frequency is
alternatively up-sliding and down-sliding alongthe fiber.
Finally, we will compare the sliding frequency Butterworth
filterand Fabry- Perot filter. The other is to use the optical
phase conjugation.When the neighboring solitons with phase
difference larger than 90o, theundoing of the soliton
interaction is well. In fact, the filter and opticalphase
conjugation can be combined to control the soliton transmission.
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Ting, Wei-Lun, and 丁偉倫. "Simulation and Analysis of Digital Optical Phase Conjugation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/86812521498990438018.
Full textAbstract:
碩士<br>國立臺灣大學<br>光電工程學研究所<br>101<br>Wavefront of the light propagating through a turbid medium would be distorted severely due to the scattering phenomenon and hence we can barely see objects behind the turbid medium. To overcome that challenge, we introduce the optical phase conjugation (OPC) to suppress the distortion caused by incoherent scattering of a turbid medium. However, conventional OPC is limited due to its minute phase conjugation reflectivity, which is defined as the power ratio of the phase conjugate signal to the input signal, and the requirements of specialized light sources and nonlinear materials. To improve the conventional OPC, digital optical phase conjugation (DOPC) proposed by Yang’s research team is applied. Basically, DOPC is identical with DOPC except it utilizes digital signal processing to generate the phase-conjugate wave to modify the performance of its phase conjugation reflectivity.
In this thesis, we simulate the macroscopic light scattering phenomenon of the DOPC phenomena in two-dimensional cases by using the finite-difference time-domain (FDTD) method and total-field / scattered-field (TF / SF) technique. Also, we analyze our DOPC simulation results and investigate the factors to optimize the reconstruction efficiency. The reported simulation results enable qualitative and quantitative characterization that can provide important information for further improvement of the DOPC technique and explore the possibility in noninvasive biomedical imaging approaches.
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Jang, Mooseok. "Optical Phase Conjugation and Its Applications in Biology." Thesis, 2016. https://thesis.library.caltech.edu/9771/1/Mooseok_Jang_2016_Thesis.pdf.
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<p>Optical phase conjugation is a process where an incoming electromagnetic wave is reflected with a reversed phase. The propagation direction of an incoming beam (equivalently, local phase gradient) can thereby be precisely reversed by the phase conjugate beam. This intriguing effect, so called "time-reversal of electromagnetic waves," allows cancellation of spatial distortion introduced into the incoming beam. Recently, this concept has provided a new avenue to overcome or utilize random scattering in the field of biophotonics.</p>
<p>This thesis discusses a number of interrelated topics regarding optical phase conjugation and its applications in biology. First, two examples of exploiting optical phase conjugation for light focusing are presented. The first example shows that the axial resolution can be improved based on the counter-propagating property of the phase-conjugate beam, and the second example demonstrates how the random scattering media can be used to enhance the flexibility in focusing range. We then discuss a new class of techniques that involves the use of guidestars in the phase conjugation process for deep tissue (> 1mm) light focusing and imaging. In the context of <i>in vivo</i> application, we model and estimate the penetration depth limit of one prominent example of this approach, time-reversed ultrasonically encoded (TRUE) optical focusing. Based on the analysis, we show that the iteration of phase conjugation operation can improve the contrast and resolution of the focal spot created inside deep tissue. We also present a new kind of guidestar-assisted method, time-reversed ultrasound microbubble encoded (TRUME) light focusing, which can focus light with sub-ultrasound wavelength resolution. At last, the effect of dynamic scatterers on time-reversal fidelity is studied to explore the possibility of applying the optical phase conjugation techniques in living tissue.</p>
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Chen, Wei-Hsin, and 陳瑋鑫. "The Study of Digital Optical Phase Conjugation and Novelty Filtering Based on Kitty Self-Pumped Phase Conjugator." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/96328607411606473263.
Full textAbstract:
碩士<br>國立中央大學<br>光電科學與工程學系<br>101<br>In this thesis, we propose a new method for the alignment of a digital optical phase conjugator (DOPC) and the design of a phase conjugate novelty filter based on the Kitty self-pumped phase conjugate mirror (Kitty-SPPCM). Kitty-SPPCM has advantages such like short response time and insensitivity to the environment. Our method of DOPC alignment includes all benefits for DOPC from various literature methods. Additionally, we design a phase conjugate novelty filter with Kitty-SPPCM and electro-optic modulator (EOM). In this research, we apply the phase conjugate novelty filter to do self-tracking and produce a focal point inside diffuse objects.
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Ryan, James R. "Optical phase conjugation via four-wave mixing in barium titanate." Thesis, 1986. http://hdl.handle.net/10945/22015.
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Morton, Kenneth Patterson. "Optical phase conjugation via stimulated Brillouin scattering in carbon disulfide." Thesis, 1985. http://hdl.handle.net/10945/23452.
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Lee, Chiang-Suo, and 李將碩. "Analyzing Diffraction Limit and Optical Phase Conjugation via FDTD Method." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/93298775921764050725.
Full textAbstract:
碩士<br>臺灣大學<br>光電工程學研究所<br>98<br>In this thesis, the finite-difference time-domain (FDTD) technique is applied to analyze the relationship of evanescent wave and diffraction limit. We employ 2D FDTD to simulate sub-wavelength single slit diffraction and observe the instantaneous Poynting vector in steady-state. We find that the magnitude of the instantaneous Poynting vector varies periodically, while the direction remains unchanged. By comparing the result with the instantaneous Poynting vector of total internal reflection evanescent wave, we think that the diffracted waves of sub-wavelength single slit diffraction are all propagating waves rather than evanescent waves. We simulate the playback of the sub-wavelength (slit width is 2λ/5) single slit diffraction via 3-sided phase conjugate mirror and the phase conjugate waves re-focus back onto the spot with dimension below the diffraction limit. Furthermore, the cross-sectional shape of slit is modified from a rectangular to a Gaussian function. For the slit width is 2λ, a perfect re-focusing profile is generated.
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Kai-ShengChen and 陳楷升. "Practical Phase Conjugation for Compensating Fiber Nonlinearity over Optical Communication Systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/43584492187984950124.
Full textAbstract:
碩士<br>國立成功大學<br>電腦與通信工程研究所<br>100<br>Self-phase modulation (SPM) and cross-phase modulation (SPM) are leading nonlinear transmission penalty in optical communication systems. In nonlinear optical media, an interesting phenomenon of the intensity dependence of the refractive index occurs through SPM or XPM, which leads to spectral broadening of optical pulses and therefor degrade system performance.
A novel scheme for fiber nonlinearity compensation based on the principles of optical phase conjugation (OPC) is proposed to reduce the phase distortion in optical communications. A phase modulator is used to modulate the phase of the data pulses in the middle of fiber spans. The magnitude of the phase modulation is proportional to the detected pulse intensity, and the sign is opposite to that of the nonlinear phase shift caused by self-phase modulation. Thus, the nonlinear phase noise induced by amplitude fluctuation and SPM in the first-half fiber is partially compensated for in the second-half fiber.
Using an optimum value of the phase deviation of the optical phase modulator, we show by numerical simulations that a non-return-to-zero (NRZ) format transmission for 720 km in dispersion-managed system at 40 Gb/s with such nonlinearities compensation can provide greater than 2 dB increase in launch power .
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Jaatinen, Esa. "Using photorefractive oscillators to obtain single mode radiation from multi-mode fields." Phd thesis, 1993. http://hdl.handle.net/1885/138445.
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CHEN, ZHI-MING, and 陳志明. "Recovery of an optical wave in a turbulent medium by phase conjugation." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/01728261097544547306.
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Yeh, Ming-Yu, and 葉明瑜. "Analysis of Digital Optical Phase Conjugation byUsing Finite-Difference Time-Domain Method." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/57266338074551852449.
Full textAbstract:
碩士<br>臺灣大學<br>光電工程學研究所<br>98<br>Due to the complex structure of biological tissues, wave propagateing through turbid medium generates interference and diffraction, generally the image is scattered and blurred. However, in nonlinear optics, with the technique of optical phase conjugation (OPC), for wave propagating through OPC, the wave refocuses to initial emanating point. Digital optical phase conjugation (DOPC) combines electro optical modulator (EOM) and spatial light modulator (SLM), which records forward scattering wave information and digitally reverses the phase information.
In this thesis, we apply the Finite-Difference Time-Domain (FDTD) technique, with additional techniques, to simulate DOPC refocusing phenomenon. Not only we simulate the basic property of DOPC, like placing an object in the simulation area to observe DOPC refocusing phenomenon, altering the width of simulation area to compare the profile of DOPC wave and the profile of incident wave; we also alter the DOPC recording time interval and spatial resolution to find the most efficient wave for DOPC refocusing. Moreover, we make use of these results to simulate DOPC refocusing through turbid medium.
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"System applications of optical phase modulation in optical metropolitan and access networks." Thesis, 2004. http://library.cuhk.edu.hk/record=b6074770.
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For packet-switched metro networks, one of the key functional blocks is the transmission, extraction and update of in-band packet control information, which is commonly known as packet label swapping. The use of phase modulation to carry the control information can facilitate easy swapping process. By combining phase modulated label with intensity modulated optical packets in non-overlapping manners, we demonstrated that optical packet label swapping using differential phase-shift keyed labels could be achieved without any sacrifices in packet signal quality.<br>In packet-switched optical networks, packets are routed using IP-based distributed routing algorithms. Inconsistencies in routing information among routing nodes may result in routing loop formation in the network and may cause severe impact on the network performance. We proposed a novel packet routing loop mitigation scheme based on the principle of packet 'time-to-live' value countdown. This scheme enables loop mitigation to be performed asynchronously in optical domain, causing little packet processing delay. Two implementations were proposed. One was based on differential optical phase shift keying and the other was based on self-phase modulation in semiconductor optical amplifier.<br>The continuous increase in Internet-bound data traffic in recent years has placed higher requirement on network bandwidth and flexibility. In view of this, packet-switched metro networks and broadband passive optical access networks have emerged as the promising network solutions in the near future. The focus of this thesis is on the improvement of functionality and reliability as well as the reduction of system complexity in optical metro area and access networks with the use of optical phase modulation techniques. In access network, constant-intensity optical phase modulation formats were studied for their applications in wavelength-division-multiplexed passive optical networks with centralized light source. Using them as downstream modulation formats, the downstream optical carrier can be utilized to carry upstream intensity-modulated data. It can greatly simplify upstream transmission and facilitate network management. Experimental and numerical analyses shows promising upstream re-modulation performance with a simple optical network unit (ONU) configuration.<br>Hung Wai.<br>Adviser: Lian-Kuan Chen.<br>Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: .<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2004.<br>Includes bibliographical references (leaves 130-135).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Abstracts in English and Chinese.<br>School code: 1307.
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GUO, ZHEN-LONG, and 郭振隆. "Nonlinear optics of nematic liquid crystals:degenerate four-wave mixing and optical phase conjugation." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/02762015993334516767.
Full textAbstract:
博士<br>國立交通大學<br>光電工程研究所<br>79<br>Properties of degenerate four7 wave mixing process, including both the
forward7 and backward7 wave interaction geometries, in homeotropically
aligned nematic liquid7 crystal films are extensively studied in theis
dissertation. The optimization of electric bias, material and geometric
parameters on the diffraction efficiency as well as the influence of
optical and electric fields on the quality of optical phase conjugation
are analyzed in a detailed manner.
The third7 order nonlinearity of liquid crystals originates from the
laser7 induced molecular reorientation which can lead to a nonlinear
refractive7 index change. A theoretical model is derived to describe the
periodically distorted structure of molecular reorientation, the formation
of a phase grating and its associated diffraction. Both the basic and
analytical solutions are obtained by taking into account all possible
elastic deformations （i.e., splay, twist and bend types）in nematic
liquid crystals at the same time. It is pointed out that the determination
of optimal biasing field is crucially influenced by the twistdeformation
in the reorientational grating and is also subjected to the competing
influences of splay and of bend elastic torqures on the molecular
reorientation, while the diffraction efficiency is concerned. If the
maximum amplitude of phase grating is large enough, double diffraction
peaks of the same efficiency can be obtained at two distinct voltages. It
is shown both by numerical calculations and analytic predictions that the
optimal amplitude of the induced phase grating is a monotonically
increasing function of the grating period, the optical intensity, and the
ratio of the bend elastic constant to that of twist. However, the
dependence of the phase amplitude on the sample thickness is quite unique.
There always exists an optimal thickness for the peak phase amplitude. The
numerical calculations are carefully checked and are shown to be valid as
compared with the applicability limit of Raman7 Nath theory.
In the experiments, a CW argon7 ion laser was used to pump a
room7 temperature nematic substance, N7 （47 methoxybenzylidene）7 47
butylaniline （MBBA）. A the measurement was automatically carried out by
utilizing a home7 made computerized system. The experimental results are
good agreement with the numerical predictions.
The efficiency and fidelity of optical phase conjugation in nematics are
also investigated by using a spatial7 filtering technique. It is shown in
the experimental results that the fidelity is improved by an applied
electric field, but is degraded with the increment of optical intensity.
The background scattering noise, due to the thermal fluctuation of NLC
directors, and the accompanying nonlinear self7 phase modulation effect
are supposed to have the most important influences on the beam quality and
this explanation agrees well the observed phenomena.
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You, Min-Lun, and 游旻倫. "Simulation of detune wavelength analysis for light focusing scattering medium via optical phase conjugation." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/apxgva.
Full textAbstract:
碩士<br>國立臺灣大學<br>光電工程學研究所<br>105<br>By employing the optical phase conjugation (OPC) phenomenon, light can be guided through and focus inside the scattering medium. In this thesis, we investigate the effect of wavelength detune on the focusing of light inside a scattering medium. We implement the pseudospectral time-domain simulation technique (PSTD) to model the focusing of OPC light with the wavelength detuned: from 99.5% to 100.5%. By modeling light propagation through various geometrical conditions, we analyze the effect of wavelength detune on the focusing of CW light through a scattering medium. The simulation findings may provide helpful information for the focusing of OPC light with detuned wavelength.
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"Photophysics and nonlinear optics based on dye-doped sol-gel silica." 1998. http://library.cuhk.edu.hk/record=b6073111.
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Lam Sio Kuan.<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 1998.<br>Includes bibliographical references (p. 111-116).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Mode of access: World Wide Web.<br>Abstracts in English and Chinese.
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Yu, Wenqian. "Applications of the photorefractive effect in mutually pumped phase conjugators and planar waveguides." Phd thesis, 1998. http://hdl.handle.net/1885/144736.
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Hou, Zhi-Shun, and 侯智舜. "The study of digital optical phase conjugation which enlarges the power of reconstructed object light." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/g56neu.
Full textAbstract:
碩士<br>國立中央大學<br>光電科學與工程學系<br>103<br>In this thesis, we improve the digital optical phase conjugation ( DOPC ) based on Kitty self-pumped phase conjugate mirror ( Kitty-SPPCM ) to enlarge the power of the object light and synchronize the reconstruction light with the record of object light. Then we try to design an in-time DOPC, use the reconstructed object light to scan, reconstruct different time’s object light, and compute the other reconstruction phase distribution. The enlarged power of the object light and the reconstruction which synchronizes with the record by our DOPC, will improve the optics-related applications of biomedical field.
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Tseng, Chia-Ta, and 曾家達. "Simulation of controlling focus spot in the scattering medium by using optical phase conjugation technique." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/u85r6n.
Full textAbstract:
碩士<br>國立臺灣大學<br>光電工程學研究所<br>103<br>Focusing light through the scattering medium is the optical application due to penetration of biomedical optics. In this thesis, we introduce the novel method of optical phase conjugation (OPC) to focus light inside the scattering medium. In order to observe this phenomenon, we provide the numerical method of pseudospectral time-domain (PSTD) technique to simulate the OPC focusing. PSTD simulation technique is employed to obtain numerical solutions of Maxwell’s equations. PSTD technique is good for simulating large space problems and reducing the computer storage. In this thesis, we demonstrate the derivative of PSTD algorithm and the simulation of OPC focusing. In the OPC theory, amplitude and phase of the outgoing light is recorded and later used to generate phase-conjugated light which back-propagates through the scattering medium, and focuses inside. Then, we introduce the application of OPC theory which called time-reversed ultrasonically encoded (TRUE). TURE is the novel technique which use the light and ultrasound to focus inside the scattering medium. In our results, by changing the angular span of phase conjugate mirror (PCM) which generates the phase-conjugated light, we can analyze back-propagation of light for different angular spans. The simulation results may help determine the optimal angular span for practical back-propagation of light. In addition, we also analyze the influence of the resolution to the focusing phenomenon. In this simulation, we understand property of light focusing through the scattering medium.