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Rios, Clauson Sales do Nascimento. "ImplementaÃÃo de portas lÃgicas atravÃs da modulaÃÃo de pulsos por posiÃÃo (PPM) em filtros acÃstico-Ãpticos sintonizÃveis." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2097.
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FundaÃÃo de Amparo à Pesquisa do Estado do CearÃNesta dissertaÃÃo foi estudada a aplicaÃÃo do filtro AcÃstico-Ãptico SintonizÃvel (AOTF), com a ModulaÃÃo de Pulsos por PosiÃÃo (PPM), objetivando implementar, utilizando o mÃtodo de Runge-Kutta de 4a ordem, portas lÃgicas (OR-OU e AND-E) Ãpticas operando com pulsos de luz ultracurtos (2ps). Neste trabalho à investigado o desempenho das portas considerando vÃrios comprimentos do filtro ( L) que integra a sua estrutura interna, com o intuito de obter o comprimento de filtro mais adequado para uma operaÃÃo satisfatÃria, em regime dispersivo, nÃo linear, sem perdas e com modulaÃÃo de fase cruzada (XPM). Esta investigaÃÃo à realizada em duas situaÃÃes: primeiramente, sÃo considerados filtros com automodulaÃÃo de fase (SPM) e GVD (dispersÃo da velocidade de grupo). Em um segundo momento, as mesmas portas sÃo obtidas com efeitos SPM, XPM e GVD agindo juntos no AOTF. Foi observado que para pulsos do tipo sÃliton, os efeitos da dispersÃo, da nÃo linearidade e da modulaÃÃo de fase cruzada exercem juntos uma forte influÃncia na propagaÃÃo do mesmo, provocando a quebra do pulso na saÃda do dispositivo quando utilizamos um comprimento maior para os filtros. Para dispositivos mais curtos, o pulso chaveado apresentou compressÃes e alargamentos temporais e espectrais, bem comodeslocamentos temporais nos dois modo de propagaÃÃo (TE e TM). ApÃs a escolha de um comprimento de filtro adequado, foi selecionado um deslocamento temporal Ãtimo a ser aplicado nos pulsos de entrada para conseguirmos, na saÃda da porta lÃgica, deslocamentos temporais satisfatÃrios (acertos) na aplicaÃÃo da modulaÃÃo PPM. Em seguida, introduzimos fases em um dos pulsos de entrada (TM), provocando um defasamento entre os pulsos TE e TM, reduzindo ainda mais a margem de erro PPM de operaÃÃo das portas. Finalmente, ao analisarmos as fases aplicadas no pulso TM (0 a 2), definirmos o melhor Ãngulo de fase para que as portas operem na regiÃo de acerto da modulaÃÃo PPM.
In this dissertation it was studied the application of the Acoustic Optical Tunable Filter (AOTF), with Pulse Position Modulation (PPM), aiming at to implement, using the method of Runge-Kutta of 4a order, logical gates (OR and AND) optical operating with pulses of light ultra shorts (2ps). In this work the acting of the gates is investigated, considering several lengths of the filter ( L) that integrates your internal structure, with the intention of obtaining the length of more appropriate filter for a satisfactory operation, in dispersion regime, nonlinear, without losses and with Cross Phase Modulation (XPM). This investigation is accomplished in two situations: firstly, filters are considered with Self Phase Modulation (SPM) and GVD (group-velocity dispersion). In a second moment, the same gates are obtained with effects SPM, XPM and GVD, acting together in AOTF. It was observed that for pulses of the type soliton, the effects of the dispersion, of the nonlinearity and of the cross phase modulation exercise together a strong influences in the propagation of the same, provoking the break of the pulse in the exit of the device when we used a larger length for the filters. For shorter devices, the switched pulse presented temporary and spectral compression and spread, as well as, displacement in the time in the two propagation modes (TE and TM). After the choice of a length of appropriate filter, a great temporary displacement was selected to be applied in the input pulses for us to get, in the exit of the logical gate, satisfactory temporary displacements (successes) in the application of the PPM modulation. Soon after, we introduced phases in one of the entrance pulses (TM), provoking a phase displacement among TE and TM pulses, still reducing more the margin of error PPM of operation of the gates. Finally, to the we analyze the applied phases in the pulse TM (0 to 2), we defined the best phase angle for the gates to operate in the success area of the PPM modulation.
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Falkenburg, Grant (Grant E. ). "High-order compensation of self-phase modulation in laser communication systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112845.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 72).
Self-phase modulation (SPM) creates a power and fiber-length dependent spectral broadening that reduces signal-to-noise ratio in free-space laser communication systems which use a fiber to connect their transmitter's high-power optical amplifier to its telescope optics. The effects of SPM can be mitigated by using a phase modulator to down-chirp pulses before passing through the receiver's matched filter. This thesis tests and evaluates a new SPM compensation technique-applying a phase modulation determined from a measurement of the SPM-distorted waveform's optical intensity-and benchmarks it against sinusoidal phase modulation compensation. The spectra and throughput of the compensated signal are calculated and measured to determine the effectiveness of the new technique. It is found that the two techniques perform within 0.2 dB of each other for fiber lengths less than three times the nonlinear length, and it is expected that the new technique will outperform sinusoidal phase modulation for greater fiber lengths.
"This material is based upon work supported under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001"--Title page.
by Grant Falkenburg.
M. Eng.
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Slagle, Jonathan E. "Degenerate Frequency Two Beam Coupling in Organic Media Via Phase Modulation." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1417798867.
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Zhou, Renjie. "DEVELOPMENT OF HIGH POWER FIBER LASER TECHNOLOGIES." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271970621.
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Carns, Jennifer. "Semiconductor Optical Amplifier as a Phase Modulator for Short-Pulse Synthetic Aperture Ladar and Vibrometry." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335278035.
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Lee, Kwan-Seop. "Studies on the decay and recovery of higher-order solitons, initiated by localized channel perturbations." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04122004-143924/unrestricted/Lee%5FKwanseop%5F200405%5FPhD.pdf.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004.John A. Buck, Committee Chair ; Stephen E. Ralph, Committee Member ; Gee-Kung Chang, Committee Member ; Rick Trebino, Committee Member ; Glenn S. Smith, Committee Member. Includes bibliographical references (leaves 102-104).
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Shahin, Shiva. "Engineering the performance of optical devices using plasmonics and nonlinear organic chromophores." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333214.
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In this work, two optical devices, organic photovoltaics (OPVs) and optical fibers, are introduced. Each of these devices have performance drawbacks. The major drawbacks of organic photovoltaics is their low absorption rate due to bandgap mismatch with the solar spectrum as well as poor charge carrier mobility and short exciton diffusion length. In order to overcome some of these drawbacks and increase the efficiency of OPVs, we use plasmonic gold nanoparticles (AuNPs). We report 30% increase in the efficiency of bulk-heterojunction OPV after incorporation of 50 nm AuNPs. The optical, electrical, and thermal impacts of AuNPs on the performance of PVs have been investigated experimentally and using Lumerical Solutions and COMSOL Multiphysics® simulation packages. The major contributions of AuNPs is causing near field enhancement and increasing the absorption of the structure by 65%, decreasing the extracted carrier density by quenching the excitons, changing the workfunction of the structure, as well as increasing the temperature of their surrounded medium when exited at their plasmon resonance frequency. Furthermore, one of the challenges in devices made from optical fibers such as wavelength division multiplexing systems, is self-phase modulation (SPM) which is a nonlinear phenomenon. We introduce a novel method to remove the SPM in liquid core optical fibers (LCOF) using nonlinear organic chromophores with a negative third-order susceptibility. The idea of this work is to eliminate the effective nonlinear refractive index that the optical pulses are experiencing while propagating through the LCOF. Further, a novel method is introduced to characterize the third-order optical nonlinear susceptibility of organic chromophores in LCOF system. The presented method is simple, and can be extended to the characterization of other nanoscale particles such as quantum dots and plasmonic metal nanoparticles in solutions. Finally, a convenient method is presented that enables researchers to investigate the mechanisms behind photobleaching of various materials. The photostability of materials is of great importance for their acceptance in commercial systems such as organic photovoltaics, electro-optic (EO) modulators and switches, etc. This method is based on the simultaneous detection of different signals such as second-, and third-harmonic generations as well as two-, and three-photon excitation fluorescence using multi-photon microscopy.
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Simões, Fábio Donati. "Estudo do impacto do gorjeio (chirp) de transiente sobre o desempenho de sistemas de transmissão óptica com pulsos NRZ." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-04072008-090547/.
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Formatos de modulação com capacidade de ajuste às condições variáveis de propagação são de interesse para uso em redes ópticas reconfiguráveis. Alterações nos níveis de potência e no mapa de dispersão afetam o desempenho de sistemas de transmissão, limitando o alcance e a capacidade de reconfiguração da rede. Fornecer capacidade de ajuste dinâmico ao sinal transmitido, sem usar sistemas complexos de modulação ou de compensação variável de dispersão, é uma solução eficaz para se obter rendimento ótimo nas diversas condições de propagação na rede. Esta característica também é útil na instalação de redes convencionais, poupando tempo e reduzindo custos. Neste trabalho é proposto o formato de modulação NRZ com gorjeio sincronizado com o sinal como alternativa para sobrepujar as limitações impostas pelas redes reconfiguráveis. O sistema proposto tem o atrativo de permitir, além da capacidade de adaptação, a possibilidade de integração dos componentes ópticos do modulador num mesmo substrato. O desempenho do formato de modulação proposto foi analisado em diversas condições de propagação para sistemas a 10 Gbit/s, tanto em sistemas ponto-a-ponto como de longas distâncias. Esta análise foi feita por meio de modelagem matemática, simulações numéricas e experimentos em laboratório. Foi demonstrada a capacidade de ajuste a diversos mapas de dispersão e seus limites, bem como a compensação de efeitos da automodulação de fase causados por alterações no nível da potência do sinal.Modulation formats with adjustment capability to the variable propagation conditions are of interest in reconfigurable optical networks. Changes in optical power levels and dispersion compensation map affect the transmission system performance, limiting the range and the network reconfiguration capability. To provide dynamical adjustment capability to the transmitted signal, using neither complex modulation systems nor variable dispersion compensation, is an effective solution to obtain optimal performance within the diverse network propagation conditions. This characteristic is also useful during conventional networks installation, saving time and reducing costs. In this work it is proposed the NRZ modulation format with signal synchronized chirp as an alternative to overcome the limitations imposed by the reconfigurable networks. The proposed system has the benefit of allowing, more than adaptation capability, the possibility of integration of the optical modulator\'s components in the same substrate. The proposed modulation format was analyzed under diverse propagation conditions for 10 Gbit/s, in point-to-point as well as long-haul systems. This analyses war performed by mathematical modeling, numerical simulations and laboratorial experiments. It was demonstrated the adjustment capability for diverse dispersion compensation maps and its limits as well as the compensation of the self-phase modulation effects due to changes in optical power levels.
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Fourcade, Dutin Coralie. "Réduction de la durée d’impulsions laser par des techniques extra et intra-cavité : post-compression d’impulsions femtosecondes énergétiques et modulation spectrale des pertes dans un pré-amplificateur Ti˸saphir." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14298/document.
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La course vers les impulsions ultra-courtes et énergétiques est en plein essor avec le développement de nombreuses applications. Dans ce manuscrit, plusieurs méthodes de réduction de la durée d'impulsion énergétique sont étudiées. La mise en oeuvre d’un système de post-compression basé sur le principe de SPM-NER dans une lame de silice a tout d'abord permis de produire, à partir d'impulsions de 50 fs, des impulsions de 16 fs-5mJ. Dans une seconde partie, nous proposons une nouvelle méthode de post-compression efficace basée sur l'ionisation d'un gaz rare dans un capillaire creux. Cette technique a permis d'obtenir à la fois des impulsions ultra-courtes et des énergies importantes (11 fs-13 mJ). Les résultats d'une modélisation réalisée au CEA/SPAM, en bon accord avec les résultats expérimentaux, ont permis d'approfondir la compréhension des divers mécanismes mis en jeu. Afin de produire des impulsions encore plus courtes, il est nécessaire de travailler directement dans les chaînes laser, en amont du système de post-compression. Le rétrécissement spectral par le gain dans leTi:saphir des chaînes laser, limite en général les durées des impulsions à 30 fs. Ce phénomène, étudié lors de cette thèse, a été compensé grâce à une modulation de perte spectrale (filtre) dans le pré-amplificateur (cavité régénérative), localisée au maximum de la courbe de gain. Des impulsions de l’ordre de 20 fs ont été obtenues. Ces études ont été complétées par une modélisation de l'amplification des impulsions qui s'est avérée en très bon accord avec les mesures expérimentales. La possibilité de combiner ces procédés permettra, àcourt terme, la production d'impulsions laser sub-10 fs énergétiques (~10 mJ) pour générer des impulsions XUV attosecondes isoléesHigh energy ultrashort pulses are highly desirable for many applications. In thismanuscript, we described several methods for pulse duration reduction at high energy. A postcompressionsystem, using SPM-NER in a fused silica plate, has firstly provided 16 fs-5mJpulses, from 50 fs pulses. In a second part, we present a new efficient post compressiontechnique, achieved through ionization of gas in a capillary. With this technique, ultrashortand high energy pulses have been reached (11 fs-13 mJ). Results from modeling done atCEA/SPAM, in good agreement with the experimental ones, have been used to understanddeeply all the involved mechanisms. In order to get even shorter pulses, it is incontrovertibleto work on the laser chain, in front of the post-compression systems. In general, due tospectral gain narrowing in Ti:Saphir laser chain, the pulse duration is limited to 30 fs. Thiseffect, investigated in this thesis, has been compensated by modulating the spectral losses(filter) in the pre-amplifier (regenerative cavity), localized at the gain curve maximum. Pulseduration in the order of 20 fs has been obtained. This study has been completed with a pulseamplification model that shows very good agreement with the experimental measurements.The possibility to combine these processes should generate, in the short term, high energy (10mJ) sub-10 fs laser pulses to produce isolated XUV attosecond pulses
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Labaye, François. "Amplification passive d'un laser à fibre optique dans une cavité Fabry-Perot : application à la production de rayonnement gamma par diffusion Compton inverse." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00837822.
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La nécessité de prouver l'existence de nouvelles particules comme les quarks et le boson de Higgs a entrainé le développement de deux nouveaux pans de la recherche : la physique des hautes énergies ou physique des particules, dédiée à prouver expérimentalement l'existence de ces particules puis à étudier leurs propriétés et la physique des accélérateurs, dédiée au développement de nouveaux instruments pour la physique des hautes énergies.Dans ce contexte, des collisionneurs linéaires électrons/positrons polarisés de forte luminosité dont l'énergie serait connue et accordable pourrait permettre d'étudier plus finement des particules se situant dans des énergies autour du TeV telles que le Boson de Higgs. C'est dans ce sens que le projet International Linear Collider (ILC) est conçu et c'est dans le cadre du développement de ce collisionneur linéaire de particules que cette thèse de doctorat se situe. Un des points critiques de l'ILC est la source de positrons polarisés. Sans entrer dans des explications sur la physique du processus de création de positrons polarisés, nous précisons simplement que ceux-ci sont créés lorsque des rayons gamma polarisés circulairement interagissent avec la matière. Le point critique est donc la source de rayons gamma polarisés circulairement. Une alternative pour cette source est la diffusion Compton inverse et c'est finalement dans le cadre de la recherche et du développement de systèmes lasers de fortes puissances moyennes asservis à des cavités Fabry-Perot pour la production de rayons gamma polarisés par diffusion Compton inverse que se situe cette thèse.Dans un premier temps, nous posons plus précisément le contexte de cette thèse, le principe de la diffusion Compton inverse ainsi que le choix d'une architecture optique basée sur un laser fibré et une cavité Fabry-Perot. Nous finissons sur une énumération des différentes applications possibles de la diffusion Compton inverse montrant que les travaux présentés pourraient bénéficier de transfert technologique vers d'autres domaines. Dans un second temps, nous présentons les différentes architectures d'amplification laser fibrée étudiées ainsi que les résultats obtenus. Dans un troisième temps, nous faisons un rappel du principe de fonctionnement d'une cavité Fabry-Perot et présentons celle utilisée pour notre expérience ainsi que ses spécificités. Dans un quatrième temps, nous abordons l'expérience de diffusion Compton inverse qui nous a permis de présenter pour la première fois à notre connaissance l'utilisation conjointe d'un laser à fibre optique et d'une cavité Fabry-Perot dans le cadre d'un accélérateur de particules pour générer des rayons gamma. Le dispositif expérimental ainsi que les résultats obtenus sont alors présentés. Finalement, nous résumons les résultats présentés dans ce manuscrit et proposons différentes possibilités d'évolution pour le système dans une conclusion générale.
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Talisa, Noah Brodzik. "Laser-Induced Damage and Ablation of Dielectrics with Few-Cycle Laser Pulses." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1609243476481238.
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Boughdad, Omar. "Fluides de lumière dans un milieu non-linéaire photoréfractif." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4014.
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L’objet de cette thèse est l’étude expérimentale des comportements hydrodynamiques d’un faisceau laser se propageant dans un milieu à réponse non-linéaire. Pour un milieu presentant un indice de réfraction qui depend de l’intensité du laser, ainsi que dans le cadre de l’approximation paraxiale, l’intensité du faisceau est assimilée à une densité de fluide. L’axe de propagation représente le temps d’évolution du fluide, le gradient de phase du faisceau définit sa vitesse d’écoulement et la variation de l’indice de réfraction permet de définir une vitesse du son dans le fluide. Dans le cadre de cette analogie, nous appelons le faisceau qui se propage, fluide de lumière. Dans cette thèse, nous étudions la notion de superfluidité de la lumière dans un régime non linéaire auto-défocalisant (self-defocusing). Cette notion est définie par l’absence de diffraction lorsque le fluide de lumière se propage en présence d’un obstacle. Les paramètres permettant de contrôler la transition superfluide sont : la vitesse du fluide de lumière ainsi que la vitesse du son. La première est pilotée par la direction du vecteur d’onde, ainsi que la deuxième est contrôlée par l’intensité du laser. Nous étudions aussi dans le cadre de cette analogie, le régime d’émission de vortex quantifiés suite à l’interaction entre le fluide de lumière et l’obstacle, considéré dans ce cas comme étant fort. Quand deux fois la vitesse d’écoulement aux pôles de l’obstacle dépasse la vitesse du son, des paires de vortex/anti-vortex sont émises, démontrant ainsi un comportement hydrodynamique de la lumière. Dans le but de comprendre l’effet non linéaire mis en jeu, nous présentons également dans cette thèse, une étude de l’effet photoréfractif non-linéaire en exploitant l’effet de l’automodulation de phase (self-phase modulation)This thesis presents an experimental study of hydrodynamical phenomena of a laser propagating nonlinearly. For a medium presenting an intensity-dependent refractive index, and in the frame of the paraxial approximation, The intensity of the laser beam is equivalent to a density of a fluid, the propagation direction is seen as a time evolution of the fluid as well as the phase gradient of the laser beam defines a flow velocity and the nonlinear refractive index change allows defining a sound velocity of the fluid. Under this analogy, we call the propagating laser beam a fluid of light. In this thesis, we provide a study of the superfluidity concept of a fluid of light in a selfdefocusing regime of the nonlinearity. It is defined as the absence of diffraction when the fluid of light encounters an obstacle. The parameters which control the superfluid transition are: the flow velocity as well as the sound velocity. They are controlled respectively through the wave vector and the intensity of the laser beam. In the frame of this analogy, we also present in this thesis a study of vortex shedding regime as a result of the interaction between the fluid of light and the obstacle. Here, the obstacle is considered to be strong. When twice the flow velocity at the poles of the obstacle is larger than the sound velocity, pairs of vortex/anti-vortex are emitted demonstrating a hydrodynamical behaviour of the fluid of light. In order to underline the nonlinear refractive index change, we also report in this thesis a study of the photorefractive effect using the self-phase modulation effect
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Huang, Tzu-Yen, and 黃子彥. "Implement phase-modulation duobinary modulation system (PMDBM) using single one modulator with high SPM tolerance." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/86603547541861370710.
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碩士國立清華大學
通訊工程研究所
93
In recent years, optical duobinary transmission (DBT) system is very attractive because of its narrow spectral width and high chromatic dispersion tolerance. In linear regime, a 10 Gb/s optical duobinary signal can be transmitted over 200 km of standard single-mode fiber (SMF) without any compensation device. However, in the nonlinear regime with self-phase modulation (SPM), the improvement in dispersion tolerance of DBT decrease rapidly duo to SPM limit. In order to improve the SPM effect, the method is inducing the chirp signal to maintain the balance between SPM and dispersion effect but the traditional chirped duobinary transmission (CDBT) scheme has complex transmitter because of using two modulators. In this paper, we experimentally demonstrate a cost-effective phase-modulation duobinary modulation scheme for improving self-phase modulation (SPM) tolerance using a single modulator. Successful transmission over 230 km of standard single mode fiber (SSMF) was achieved without any power penalty.
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Le, Blanc Stephen Paul. "Plasma-induced self-phase and cross-phase modulation of femtosecond laser pulses." Thesis, 1994. http://hdl.handle.net/1911/16750.
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The spectral, temporal, and spatial characteristics of plasma-induced self-phase and cross-phase modulation in rare gases have been investigated using a femtosecond KrF excimer laser focused to peak intensities of 10$\sp{14}$-10$\sp{15}$ W cm$\sp{-2}.$ The quiver energy of a free electron under these conditions is less than the ionization potential of all rare gases, ensuring that ionization occurs only by optical field-induced processes. Spectral blueshifts of up to 2 nm have been observed, and the blueshifted spectra show an oscillatory structure. The blueshifted spectra are shown to be the result of plasma-induced self-phase modulation and can be modeled by assuming tunneling ionization and one dimensional pulse propagation. The newly discovered oscillatory structure in the spectra is related to that observed in earlier experiments on self-phase modulation in optical fibers.
To investigate the temporal behavior of the field ionization process, pump-probe experiments have been performed with a 100 fs probe pulse at 497 nm and a 400 fs pump pulse at 248 nm. Under conditions of weak ionization (Z $\ll$ 1), pump-probe experiments and theoretical calculations show that the ionization rate of the field ionized gas is maximum at the peak of the laser pulse and that the degree of ionization changes over a time equal to about half of the pump pulse width. By observing changes in the transmission of the probe pulse caused by plasma absorption, the electron temperature of a field ionized rare gas is determined to be on the order of 1 eV. The time varying electron density in the pump-probe experiments also causes plasma-induced cross-phase modulation, or spectral blueshifting of the probe pulse spectrum of up to 15 nm.
The pump-probe experiments show that plasma defocusing causes the spectral blueshifting to be spatially dependent. Experimental results and a two dimensional pulse propagation model indicate that the most defocused beam components also show the maximum spectral blueshift. Plasma-induced cross-phase modulation has also been used to characterize the amplitude and phase of a 1 ps chirped pulse at 497 nm and the pulse width of a 400 fs pulse at 147 nm generated by four wave frequency mixing in xenon.
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Chu, Chia-Wei, and 朱家葦. "Studies of Self-Phase Modulation in Azo Dye-doped Liquid Crystals." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/93678152022657054387.
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碩士國立成功大學
物理學系碩博士班
97
Abstract In this thesis, we study the photo-induced reorientation of liquid crystals doped with azo dyes (D2) by observing the diffraction patterns resulting from self-phase modulation. Self-phase modulation results from that the pump laser induces the change of refractive index of the sample, which influences the phase of the pump laser itself, and then causes a diffraction pattern in the far field. The number of diffraction ring is proportional to the change of refractive index in the central part of illuminated region. The more change of refractive index is, the larger phase shift is resulted in the central part of illuminated region. Experiments consist of two parts; the first part is performed using a green laser, and the second part is performed with pumping a red and a green laser simultaneously. The experimental results of the first part show that the change of refractive index of the sample caused by a pump green laser is a function of the intensity of the green laser (IG). At intensities of green laser IG =0~ 0.7 W/cm2, IG=0.7~1.1 W/cm2 and IG>1.1W/cm2, we observe different phenomena in these three intensity intervals. Initially, the maximum phase shift increases (IG =0~ 0.7 W/cm2), and then decreases almost to zero at IG=1.1 W/cm2, and finally, increases again with IG being less than 3.1 W/cm2. The azo dye transits from trans to cis by absorbing green light. The transition causes the liquid crystals tend to reorient to the direction perpendicular to the polarization of pump light. Such a transition contributes to a negative torque . The torque is proportional to the number of dyes transiting from trans to cis. The azo dye transits from cis to trans by absorbing red light and heat. The transition causes the liquid crystals tend to reorient to the direction parallel to the polarization of pump light. This transition contributes to a positive torque . The torque is proportional to the number of dyes transiting from cis to trans. The total torque is summation of these two torques. The greater the total torque is, the larger the reoriented angle of liquid crystals is. At IG=0~0.7 W/cm2, the number of transition of trans to cis is larger than that of cis to trans which represents . The total torque is negative and increases with increasing intensity of pump light, so the number of diffraction ring increases with increasing intensity of the pump light. At IG=0.7~1.1 W/cm2, because more dyes transit from cis to trans, is larger than that at IG=0~0.7 W/cm2. The total torque is negative and decreases with increasing intensity of pump light. The number of diffraction ring decreases with increasing intensity of pump light. At IG>1.1W/cm2, more cis-state isomers transit to trans isomer by absorbing heat, and lead to be larger than . The total torque is positive and increases with increasing intensity of pump light. The number of diffraction ring becomes more. Illuminating only green light on the liquid crystals doped with azo dye with IG>3.1 W/cm2, the transition from trans to cis is so fast which causes the temperature in the center of illumination is higher than the nematic-isotropic temperature. The liquid crystals is isotropic in the center of illumination, and a Fraunhofer diffraction in the far field is observed. Illuminating a red laser and a green laser simultaneously on liquid crystals doped with azo dye, the red light speeds up the transition of dyes from cis to trans and causes the larger positive torque . If the positive torque is larger than negative torque , the total torque is positive and then the liquid crystals and azo-dye molecules tend to reorient to the direction parallel to the polarization of pump light.
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KE, ZHI-REN, and 柯智仁. "One dimension spatial self-phase modulation effect in liquid crystal films." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/08193392599236823214.
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Chu, Kuan-Yu, and 朱冠宇. "A Three Dimensional Measurement Method Using the Technology of Laser self-mixing Sinusoidal Phase Modulation." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/93rm3s.
Full textAbstract:
碩士國立中興大學
機械工程學系所
105
This research develop and utilize a laser diode self-mixing based three dimensional sensor, and apply to the contact probe for trigger signal measurement. The components of the three dimensional sensor system are including a laser diode, a quadrant photodiode, a beam splitter and a glass ball lens. The glass ball lens is combined with a contact probe mechanism, and placed at the straight front of the laser diode, and through measuring with the contact probe mechanism, the reflected laser light spot of the glass ball lens will cause voltage variation on the quadrant photodiode. The X and Z axis can be determined by the voltage and displacement signal trend equation from the quadrant photodiode. On the other hand, an amount of laser which is released from the laser diode reflected or scattered back from the glass ball lens will re-enter the laser cavity. The fraction of light will interfere with the original laser light inside the laser cavity, and by utilizing the property of how it react with the laser beams for the displacement signal, then the Y axis can be calculated. And write the sine phase modulation method of modulation and demodulation, so that the development of the field to a smaller measurement range development.
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Jyh-Wei, Lin, and 林智偉. "Self-Phase Modulation and Fast Switching Enhanced Pulse Generation in an Actively Mode-Locked Nd:YLF Laser." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/63493350454865970615.
Full textAbstract:
碩士國立中山大學
光電工程學研究所
86
Synthesized high-speed pulse generator was employed to drive an acousto-optic modulator in an AM mode-locked Nd:YLF laser. The result shown that pulsegenerated shorter than 10 ps at a repetition rate of 200 MHz with an average output power of 600 mW. A close form model based on gaussian approximation was built toestimate pulse width. A complete time domain model was used to study pulseevolution in AM mode-locked laser with self-phase modulation. Both self-phase modulation and fast switching enhanced pulse-shaping ability were primary causes for the low ratio between pulse-width and repetition rate. Using these effects we canreduce pulse width without increasing modulation frequency. This indicates that the laser provides an useful application for time domain optoelectronic samplingmeasurement on microwave/millimeter-wave circuits and devices.
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Shen, T. L., and 沈宗麟. "Laser heating and spatial self-phase modulation effect in nematic liquid crystal film with Nd:YAG laser light." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/18231851517899518999.
Full textAbstract:
碩士國立交通大學
電子物理學系
83
We disscuss that the laser heating effect can add the maximun rotion angle of liquid crystal within 1.06 micron metter Nd:YAG laser. By the measurement of the diffraction patterns induced by the spatial sefl-phase modulation effect it can help us to realize the temperature icrement of the sample. We found that there was Freederiscksz transition and the threshold insity consistent with our calculation. The number of rings that we measured was fewer then we calculated.
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"Multi-wavelength all-optical regeneration based on self-phase modulation and inter-channel walk-off control in fiber." 2009. http://library.cuhk.edu.hk/record=b5894074.
Full textAbstract:
Chong, Kin Man.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (p. 58-63).
Abstract also in Chinese.
Acknowledgement --- p.i
Abstract --- p.ii
摘要 --- p.iv
Table of contents --- p.vi
List of figures and tables --- p.viii
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1. --- Overview of optical regeneration --- p.1
Chapter 1.1.1. --- O-E-O regeneration --- p.3
Chapter 1.1.2. --- All-optical regeneration --- p.5
Chapter 1.2. --- Motivation of this thesis --- p.7
Chapter 1.3. --- Outline of this thesis --- p.9
Chapter Chapter 2 --- Previous schemes of all-optical regeneration --- p.10
Chapter 2.1. --- Introduction --- p.10
Chapter 2.2. --- Fiber-based all-optical regeneration --- p.12
Chapter 2.2.1. --- SPM-based regeneration --- p.12
Chapter 2.2.2. --- FWM-based regeneration --- p.15
Chapter 2.3. --- Semiconductor-based all-optical regeneration --- p.18
Chapter 2.3.1. --- XGM-based regeneration --- p.18
Chapter 2.3.2. --- XAM-based regeneration --- p.20
Chapter 2.4. --- Multi-wavelength regeneration --- p.22
Chapter 2.5. --- Summary --- p.23
Chapter Chapter 3 --- Multi-wavelength optical 2R regeneration utilizing self-phase modulation and inter-channel walk-off control in fiber --- p.25
Chapter 3.1. --- Introduction --- p.25
Chapter 3.2. --- System architecture of the regenerator --- p.27
Chapter 3.3. --- Experimental setup --- p.28
Chapter 3.4. --- Results and discussions --- p.32
Chapter 3.4.1. --- Effects of the improper inter-channel walk-off --- p.35
Chapter 3.4.2. --- Effects of the improper filter offset --- p.36
Chapter 3.5. --- Summary --- p.39
Chapter Chapter 4 --- Investigation of the scalability and cascadability of our proposed multi-wavelength regeneration scheme --- p.40
Chapter 4.1. --- Introduction --- p.40
Chapter 4.2. --- Simulation models and results --- p.41
Chapter 4.2.1. --- 10x10-Gb/s scenario --- p.41
Chapter 4.2.2. --- 4x40-Gb/s scenario --- p.47
Chapter 4.3. --- Discussions --- p.51
Chapter 4.4. --- Summary --- p.53
Chapter Chapter 5 --- Conclusion and future works --- p.54
Chapter 5.1. --- Summary of the thesis --- p.54
Chapter 5.2. --- Future works --- p.55
List of publications --- p.57
Bibliography --- p.58
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Chu, Hsuan-Hao, and 褚軒豪. "High loss budget and high capacity employing self-phase modulation in long-reach passive optical networks OFDM system." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/69556824276803935472.
Full textAbstract:
碩士國立交通大學
光電工程研究所
102
In order to meet the demand of broadband in the future, the FSAN (Full Service Area Networks) will set the standard for next-generation passive optical network (NGPON), which is named as the NGPON2. The NGPON2 provides 40-Gbps capacity to support 1-Gbps data rate for optical network unit (ONU), and cover the distance from 20-km to 100-km. Consequently, the Optical OFDM PON with intensity modulation and direction (IMDD) is very suitable for NGPON2 system because the method offer high spectral efficiency and flexible bandwidth allocation. However, the Optical IMDD OFDM system will face some challenges which include RF power fading, Subcarrier-to-Subcarrier-Intermixing Interference (SSII), and lower power budget. Therefore, in my work, we take the self-phase modulation into consideration to solve the RF power fading and employ the SSII compensation to create the better data rate. Finally, we experimentally demonstrate the 60-km OFDM transmission to show 32-dB loss budget without inline and pre-amplifier. Employing 10-GHz electro-absorption modulator (EAM) and positive intrinsic negative (PIN), the system is economic to support 32ONUs with >1-Gbps/ONU capacity.
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Chiu, Jin-Chen, and 邱金城. "Study on Nonlinear Self-Phase Modulation Enhancement in Passive Mode Locked Fiber Laser with Single-Wall Carbon Nanotube Saturable Absorber." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/22147616970849188470.
Full textAbstract:
博士國立中山大學
光電工程學系研究所
99
The dependence of thickness and concentration product (TCP) of single-wall carbon nanotubes saturable absorber (SWCNTs SA) on stabilizing and shortening pulse width in passively mode-locked erbium-doped fiber ring laser (MLEDFL) was investigated and measured. The TCP represented the amounts of SWCNTs, which the optical beam encountered when passing through the SWCNTs SA. If the TCP was smaller than 8.25 (μm x wt%), the spectral bandwidth was below 2 nm. The pulse shaping was dominated by its own self amplitude modulation (SAM) of SWCNTs SA. With further increasing TCP, the soliton-like ML operation was achieved and the spectral bandwidth was expanded to 6 nm. For soliton-like mode locking (ML) operation, the area theorem dominated the pulse shaping. Through area theorem analysis, the estimation of SPM increased as the TCP increased. The adequate enhanced SPM for balancing the slight negative GVD was provided to generate soliton-like ML pulses shorten the pulse width. However, as the TCP increased, the soliton pulse energy decreased. The decreasing soliton pulse energy restricted the further pulse shortening. The results showed that the dependence of the pulse energy and nonlinear self phase modulation (SPM) on TCP enabled to determine the shortest pulse width in MLEDFL based on the area theorem. At optimized TCP of 70.93 (μm x wt%), it was found that the shortest pulse width of 418 fs. In addition, based on the estimated SPM from area theorem, the nonlinear refractive index n2 was calculated at the level of 0.4 - 1 x 10^-15 m^2/W that was close to the literature values of 10^-15 - 10^-16 m2/W. It provides another way to estimate the nonlinear refractive index except for the Z-scan measurement. We could also estimate the SPM if an active Z-scan measurement was taken to obtain the nonlinear refractive index of the sample. We realized the trend of pulse energy through few samples in MLEDFL, the behavior of pulse width could be theoretically simulated based on area theorem. Hence, with the area theorem analysis, the optimized TCP of SWCNTs SA could be simulated and estimated to generate the shortest pulse width from the trends of pulse energy and estimated SPM. The significant effect of TCP on pulse energy, SPM, pulse width, and spectral bandwidth of MLFLs suggests that the TCP represents the total amount of SWCNTs in SA, which can be used as one of key parameters for characterizing the passive MLFL pulse width. Through the study of the dependence of TCP on ML pulses in MLEDFL, it may provide a guideline to fabricate an effective SWCNTs SA to generate the shortest pulse width of the MLEDFL.
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CHUNG, SUNG HAN. "Wavelength-Preserving Polarization-Insensitive All-Optical 3R Regenerator Based on Self- and Cross-Phase Modulation and Offset Filtering Utilizing Raman Amplification." Thesis, 2009. http://hdl.handle.net/1974/5278.
Full textAbstract:
Optical regeneration has the potential to significantly increase the reach of long-haul transmission systems. In this thesis, wavelength-preserving polarization-insensitive all-optical 3R regeneration is investigated and demonstrated for 10 and 40 Gb/s signals. The all-optical regenerator utilizes a self-pulsating laser for clock recovery, cross-phase modulation (XPM) based spectral broadening in a highly nonlinear fiber (HNLF) and offset filtering for retiming, and self-phase modulation based spectral broadening in a HNLF and offset filtering for reshaping. Raman amplification is used to increase the XPM-based spectral broadening and thus allow a design that meets the tradeoffs involved in simultaneously achieving good retiming and reshaping performance. The regenerator is shown to reduce amplitude noise and timing jitter while not causing a BER penalty. To fully validate the regeneration scheme, the cascadability is demonstrated using a recirculating loop. For a 10 Gb/s signal, with a regenerator spacing of 240 km, a return-to-zero, on-off-keyed (RZ-OOK) signal was transmitted over 18,000 km (75 loops) with a power penalty of 1.6 dB at a BER of 1E-9 compared to the back-to-back case. For a 40 Gb/s signal, with a regenerator spacing of 80 km, a RZ-OOK signal was transmitted over 8,000 km (100 loops) with a power penalty of 1.2 dB. In addition, all-optical 3R regeneration is demonstrated using a multimode quantum-dot Fabry Petot laser with ultra-low timing jitter.Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-10-19 14:11:53.826
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Li, Baolei. "Novel Nonlinear Microscopy Techniques Based on Femtosecond Laser Pulse Shaping and Their Applications." Diss., 2013. http://hdl.handle.net/10161/7099.
Full textAbstract:
Nonlinear optical microscopy serves as a great tool for biomedical imaging due to its high resolution, deep penetration, inherent three dimensional optical sectioning capabilities and superior performance in scattering media. Conventional nonlinear optical microscopy techniques, e.g. two photon fluorescence and second harmonic generation, are based on detecting a small light signal emitted at a new wavelength that is well separated from the excitation light. However, there are also many other nonlinear processes, such as two-photon absorption and self-phase modulation, that do not generate light at new wavelengths and that have not been extensively explored for imaging. This dissertation extends the accessible mechanisms for contrast to the later nonlinear optical processes by combining femtosecond laser pulse shaping and homodyne detection. We developed a rapid pulse shaper with a relatively simple and compact instrument design that modifies the spectrum of individual laser pulses from an 80 MHz mode-locked laser. The pulse shaper enables simultaneous two-photon absorption and self-phase modulation imaging of various nanoparticles in-vitro with high sensitivity. We also applied this imaging technique to study the nonlinear optical response in graphene. Because our technology detects the nonlinear signature encoded within the laser pulse itself, we achieve intrinsic contrast of biological and non-biological samples in highly scattering media. These capabilities have significant implications in biomedical imaging and nanophotonics.
Dissertation