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Jukna, Vytautas. "Conical wave triggered transient spatio-temporal effects in Kerr media". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121001_093530-53415.
Pełny tekst źródłaDisertaciją sudaro įvadas, penki pagrindiniai skyriai ir išvados. Įvade aiškinamas sudėtingas šviesos gijų formavimosi procesas. Paaiškinami fizikiniai reiškiniai, lemiantys šviesos gijų generacijos bei evoliucijos ypatybes, supažindinama su įvairiais šviesos gijų susidarymo ir sklidimo modeliais. Antrajame skyriuje nagrinėjama pradinio pluošto diametro įtaka superkontinuumo spektrui. Trečias skyrius, skirtas šviesos gijų generacijos sklaidančioje terpėje tyrimui, apima atlikto eksperimento bei sukurtos naujos skaitmeninio modeliavimo schemos pristatymą, ir, galiausiai, skaitmeninio modeliavimo ir eksperimentinių rezultatų palyginimą. Ketvirtame skyriuje nagrinėjama daugelio gijų generacija elipsiniais pluoštais. Trumpai paaiškinta kaskadinio keturbangio maišymo įtaka šviesos gijų periodiškumui. Ištirta šviesos gijų periodo priklausomybė nuo bangos intensyvumo, ir atskleista daugelio gijų generacijos dinamika. Moduliacinio nestabilumo analizė ir jos įtaka taip pat pateikiama ketvirtame skyriuje. Penktajame skyriuje nagrinėjama ekstremalių įvykių tūrinėje Kerro terpėje atsiradimas. Palyginami plataus spektro generacijos kompiuterinio modeliavimo ir eksperimento metu surinkti statistiniai duomenys. Pabaigoje pateikti pagrindiniai darbo rezultatai ir išvados.
Liu, Jingtian. "Shaping Strategies to Embrace Nonlinear Effects in Optical Fiber Communications". Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAT007.
Pełny tekst źródłaThe main impediment in long-distance communications is nonlinear interference (NLI), stemming from nonlinear effects in optical fibers. While Digital signal processing algorithms offer partial mitigation, the inherent nonlinear nature of the fiber, coupled with predominant dispersion effects, continues to challenge the increase of transmission throughputs. Addressing nonlinearity at the information source through signal modulation technology is at the heart of our research. Traditional modulation schemes, as spectral efficiency climbs, such as QAM, become increasingly susceptible to NLI while their Mean Squared Euclidean Distance (MSED) diminishes. While multi-dimensional (MD) modulation yields improved linear and partial nonlinear gains, it has not yet demonstrated tangible benefits. On the other hand, the emergence of probabilistic constellation shaping (PCS), preferred for its enhanced linear gain and compatibility with conventional modulation hardware and software, introduces additional NLI. Consequently, the design of nonlinear-tolerant PCS is emerging as a pivotal research direction. Our thesis begins with a novel MD modulation for uniformly distributed signals. Then, we propose a novel approach combining MD with PCS to examine performance variations. Delving into PCS, we investigate the enumerative sphere shaping distribution matcher (DM), initially from an MD stance, and design a DM optimized for nonlinear tolerance over shorter distances. Subsequently, we introduce a new NLI measurement technique, accounting for dispersion effects. Integrating this with the sequence selection framework of PCS, we achieve successful long-distance transmission with notable nonlinear gains
Becerra, Castro Emilio Manuel 1977. "Efeitos óticos não-lineares transversais a baixas intensidades de luz". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278228.
Pełny tekst źródłaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
Made available in DSpace on 2018-08-21T04:46:52Z (GMT). No. of bitstreams: 1 BecerraCastro_EmilioManuel_D.pdf: 3066640 bytes, checksum: 3e7ff0e58dae7364f9f6d0b5f37924eb (MD5) Previous issue date: 2012
Resumo: Neste tese apresentamos um estudo teórico dos efeitos de coerência atómica em vapor atómico com o propósito de estudar teoricamente efeitos óticos não-lineares transversais a baixas intensidades de luz. Sob a condição da transparência induzida eletromagneticamente, um meio atómico pode desenvolver não-linearidades óticas gigantes, possibilitando a observação de efeitos óticos não-lineares a baixas intensidades. Investigamos três efeitos transversais: emissão cónica, focalização induzida e feixes de vórtices induzidos eletromagneticamente. Todos estes três efeitos têm origem na modulação de fase cruzada entre um laser de prova e um laser sinal, ambos fracos, com intensidades abaixo da intensidade de saturação das transições às quais estão acopladas. Em emissão cónica, descrevemos a formação de anéis ao redor de um feixe de prova fraco. No estudo de focalização induzida, descrevemos como que a aplicação de uma máscara de intensidade ao feixe sinal pode levar à formação de lentes GRIN no vapor atómico, induzindo à focalização do laser de prova. Por último, estudamos a conversão do feixe de prova em um feixe de vórtice ótico pela aplicação de uma máscara de intensidade espiral ao feixe sinal
Abstract: In this thesis we present theoretical study of the effects of atomic coherence in atomic vapor for the purpose of studying theoretically transverse nonlinear optical effects at low light levels. Under the conditions of electromagnetically induced transparency, an atomic medium can develop giant optical nonlinearities, allowing the observation of nonlinear optical effects to low intensities. We investigate three transverse effects: conical emission, induced focusing and electromagnetically induced vortices. All three of these effects stem from cross-phase modulation between probe and a signal laser, both weak with intensities below the saturation intensity the transitions to they coupled. In conical emission, we describe the formation of rings around a weak probe beam. In the study of induced focusing, we describe how applying an intensity mask to the signal beam can lead to the formation of GRIN lenses the atomic vapor, leading to focusing of the probe laser. Finally, we studied the conversion of the probe beam into an optical vortex beam by applying a spiral intensity mask to the signal beam
Doutorado
Física
Doutor em Ciências
Kaassamani, Shatha. "Polarization Spectroscopy of High Order Harmonic Generation in Semiconductors Orbital angular momentum from semiconductor high-order harmonics All semiconductor enhanced highharmonic generation from a single nanostructured cone". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP091.
Pełny tekst źródłaSince its first observation, a decade ago, high harmonic generation (HHG) in crystals has proved to be an efficient, controllable and compact source of coherent XUV radiation. In this thesis, we investigate HHG in 2D materials, particularly graphene, and in different semiconductor crystals mainly zinc oxide, silicon, gallium arsenide and magnesium oxide. We find that the laser properties, such as its intensity, polarization and ellipticity, and the crystal properties are interrelated. Moreover, we shed the light on the role of the linear and nonlinear propagation effects mainly the Kerr effect, upon laser interaction with the crystal, which can significantly influence the high harmonic generation efficiency. Although this presents major limitations, we show that in some cases it turns out to be an advantage. Finally, we demonstrate the manipulation of the harmonic radiation at the source of the emission by patterning nanostructures to confine and enhance nanojoule laser pulses, and generate harmonic beams carrying orbital angular momentum. Lastly, we successfully image a micrometer-sized sample by the coherent diffractive imaging (CDI) technique based on solid-state harmonics
Balakireva, Irina. "Nonlinear dynamics of Kerr optical frequency combs". Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2043.
Pełny tekst źródłaThis thesis is dedicated to the study of the Kerr optical frequency combs in whispering gallery moderesonators, where the light can be excited by the extern pump. Due to the Kerr effect existing in theseresonators, the quasi-equidistant lines in the spectral domain are generated around the excited mode,that is the frequency comb. This thesis is devided in three chapters. The first one is dedicated to theintroduction of the Kerr comb generation and their applications.The second one presents the analysisof the Lugiato-Lefever equation used for the analytical study of the system, leading to the constructionof two bifurcation diagrams for the normal and anomalous dispersions. They are plotted for twoparameters, which can be controlled during experiments once the resonator has been fabricated,which are the pump power of the laser and its frequency detuning. These diagrams show the areas ofthe parameters for which one, two, or three solutions exist and their stability. The additional numericalsimulations show the exact type of the solution in each area (such as the bright and dark solitons,the breathers, the primary and secondary Kerr combs and chaotical regimes), finally these diagramsshow the parameters of the laser needed to be choosen for the generation of the desired solution.The third chapter is dedicated to the secondary Kerr combs, which are the additional lines generatedbetween the lines of the primary comb. They appear in the anomalous dispersion regime, when thequantity of the pump photons crosses the second-order threshold, which has been found numerically
Rasekh, Payman. "Kerr Effect at the THz Frequencies". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41085.
Pełny tekst źródłaSquire, Anthony. "Incoherent laser light as a probe of ultrafast nonlinear optics". Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296168.
Pełny tekst źródłaLaban, Dane Edward. "Highly Nonlinear Optical Phenomena with Few-Cycle Light Pulses". Thesis, Griffith University, 2014. http://hdl.handle.net/10072/365337.
Pełny tekst źródłaThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text
Zhang, Weiya. "Effect of a thin optical Kerr medium on a Laguerre-Gaussian beam and the applications". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/W_Zhang_121306.pdf.
Pełny tekst źródłaBree, Carsten. "Self-compression of intense optical pulses and the filamentary regime of nonlinear optics". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16430.
Pełny tekst źródłaThis thesis discusses femtosecond filaments in dispersive dielectric media. In particular, the generation of intense, few-cycle optical pulses due to self-compression in noble gases is analyzed from a theoretical as well as from an experimental viewpoint, clearly isolating the physical mechanisms behind the observed pulse self-compression mechanism. To this end, numerical simulations of high-intensity femtosecond pulses propagating in noble gases were performed, and an analytical model of the processes leading to pulse self-compression was developed. Moreover, a theoretically predicted temporal self-healing property of femtosecond filaments is experimentally proven, demonstrating that few-cycle optical pulses can recover and even benefit from a temporary, non-adiabatic increase of dispersion and nonlinearity of the order of three magnitudes as experienced during the passage from a gaseous medium to a thin silica sample. Filamentation sets in at field strengths that approach the order of inner-atomic binding forces. At these extreme intensities, highly nonlinear effects such as multiphoton ionization or tunneling effects occur. Recent experimental investigations claim a prevalent contribution of a saturation of the optical Kerr effect in filamentation prior to the onset of Drude-contributions from ionization effects. This finding is currently controversially discussed in literature. In this thesis, an independent theoretical approach was pursued, estimating high-order contributions to the all-optical Kerr effect via a Kramers-Kronig transform of multiphoton absorption cross-sections. Quite surprisingly, while only based on first principles with some moderate approximations, the results of this analysis are in strong support of the recently suggested higher-order Kerr model.
Walasik, Wiktor. "Plasmon-soliton waves in metal-nonlinear dielectric planar structures". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284234.
Pełny tekst źródłaEl objetivo de esta tesis es la mejora en el conocimiento de los SP, así como el diseño de estructuras capaces de soportar estas ondas no lineales a bajos niveles de intensidad.En primer lugar, se ha estudiado la configuración correspondiente a un medio no lineal semiinfinito. Para ello se han desarrollado dos modelos semianalíticos basados en las ecuaciones de Maxwell. El primero trata la no linealidad de tipo Kerr de una manera sencilla, pero permite obtener expresiones analíticas para tanto los perfiles de campo como para las relaciones de dispersión no lineales. El segundo considera la no linealidad de un modo exacto. Esto permite obtener una expresión analítica de la mencionada relación de dispersión no lineal; sin embargo, los perfiles de campo han de ser obtenidos numéricamente. Se estudian también por primera vez estructuras de tres láminas (dieléctrico no lineal/metal/ dieléctrico lineal) en las que las constantes dieléctricas lineales del recubrimiento son distintas en ambos lados del metal. En estas estructuras se optimizan los parámetros y se obtienen pequeñas zonas con presencia de SP de baja energía. Puesto que los modelos están desarrollados para estructuras de cuatro láminas, se pueden estudiar por primera vez configuraciones con una lámina dieléctrica adicional situada entre el dieléctrico no lineal y el metal. Se proporcionan a su vez diagramas de dispersión y perfiles de campo para las anteriores estructuras en función de varios parámetros. La formulación semianalítica de los modelos permite hacer un rápido barrido del espacio fásico de los parámetros de la estructura. De este modo, se muestran configuraciones de cuatro láminas con unos parámetros realistas para la creación de los citados SP de baja energía.En segundo lugar, se han estudiado las guías de onda metálicas no lineales (GOMNL), en las que un núcleo dieléctrico no lineal de tamaño finito es intercalado entre dos láminas metálicas. Para ello se han desarrollado de nuevo dos modelos basados en las ecuaciones de Maxwell. El primero trata la no linealidad de tipo Kerr de un modo sencillo, pero proporciona expresiones analíticas para los perfiles de campo y las relaciones de dispersión no lineales mediante funciones elípticas de Jacobi. Por otra parte, el segundo modelo trata la no linealidad de tipo Kerr de un modo exacto y proporciona una condición analítica para la eliminación de una de las dimensiones del espacio fásico en el cual las soluciones son buscadas numéricamente. A su vez se estudian las curvas de dispersión así como sus posibles transformaciones de modo asociadas para las GOMNL. Además de los modos de primer orden típicos en este tipo de estructuras, se muestra la existencia de modos de orden superior. Todos los modos de las GOMNL pueden ser divididos en dos familias: la de los modos simétricos y antisimétricos con nodos que se asemejan a los modos lineales de una guía de onda metálica lineal modificada; y la de los modos simétricos y asimétricos sin nodos y que no se asemejan a ningún tipo de modos lineales. En esta última familia, los modos simétricos aparecen a través de una bifurcación silla-nodo y los asimétricos a través de una bifurcación de Hopf. Se estudian también los efectos producidos sobre los diagramas de dispersión al variar el tamaño del núcleo y el contraste dieléctrico entre el núcleo y el recubrimiento metálico.
Labidi, Tarek. "Amplification sensible à la phase de signaux analogiques sur porteuse optique". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS340/document.
Pełny tekst źródłaMicrowave photonic links are expected to play an important role in future RF systems. Based on low loss optical fibers, analog photonic links (APLs) have become the heart of the emerging field of microwave photonics, in which various functionalities are explored such as the generation and distribution of radar signals and local oscillators, phase shifting, reconfigurable true time delays, or even more complex functions such as spectrum analysis or correlation of RF signals. Unavoidably, microwave photonics systems undergo losses due either to microwave-to-optical conversion or to propagation. Classical amplifiers based on erbium doped fibers, semiconductor amplification, or Raman scattering in fibers, do not allow to compensate for these losses without degrading the signal-to-noise ratio. The aim of this thesis is to address this issue and to theoretically study and experimentally an optical phase-sensitive amplifier based on highly nonlinear fiber (HNLF) in order to amplify an analog signals without adding noise. We experimentally investigate the linearity of a phase sensitive amplifier based on nonlinear optical fiber in the context of microwave photonics. The linearity of the PSA amplifier is assessed by performing third order intermodulation distortion products (IMD3) measurements using two RF tones. The results show that the PSA is, in the explored domain, perfectly linear for the RF modulation, leading to amplification without any increase of distortion, thus proving the compatibility with future microwave photonics applications. In addition, we study the performance of our PSA in terms of noise by taking measurements of the noise figure (NF). Indeed, we measure a noise factor of -2.07 dB in the case where when we detect only the signal, while a 0.2 dB noise factor is obtained when both "signal and idler" are detected
Emms, Rhys Mullin. "Impact of Plasma Dynamics On Femtosecond Filamentation". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35126.
Pełny tekst źródłaSinclair, Gary F. "Cross-phase modulation in rubidium-87". Thesis, St Andrews, 2009. http://hdl.handle.net/10023/735.
Pełny tekst źródłaBesse, Valentin. "Dynamique spatiale de la lumière et saturation de l’effet Kerr". Thesis, Angers, 2014. http://www.theses.fr/2014ANGE0030/document.
Pełny tekst źródłaWe present a study of light dynamics and measurements of the nonlinear optical characteristics of carbon disulphide. In the first part, we calculate using the classical model, the nonlinear susceptibilities up to the fifth order taking into account local field corrections. We express different assumptions that we confirm or refute by measuring the nonlinear absorption coefficient and the nonlinear refractive index. The measurements are performed by means of two nonlinear characterization methods combined with an imaging 4f system. We analyse the experimental data using a newly developed method which numerically inverts the analytical solutions of the differential equations which describe the evolution of the beam, using Newton’s method. In the second part, we observe light filamentation at wavelength 532 nm, in the picoseconds regime. Then we measure the effective third order nonlinear refractive index n2,eff versus the incident intensity. By fitting the curve of the Kerr effect saturation, we develop a new model. Numerically solving this model, allows us to reproducethe experimentally observed filamentation. The last part is dedicated to the study of dissipative solitons dynamics. The complex Ginzburg-Landau equation with cubic-quintic nonlineraties is numerically solved in various configurations : soliton fundamental dipole, quadrupole, vortex and square rhombic
Bergmann, Emeric. "Optique non linéaire quadratique et cubique des nanoparticules d'or uniques". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10291/document.
Pełny tekst źródłaThe manuscript reports a study about the quadratic and cubic nonlinear optical response from gold metallic nanostructures which are deposited onto substrates. The field of this work is more commonly known as nonlinear plasmonics and it consists in trying to understand the interaction between nanostructures and light, in a regime of high incident intensities when the response is no longer linear. The local electromagnetic field enhancement in these structures due to the surface plasmon resonance, the latters being collectives excitations of the conduction band electrons, increase drastically the cross-section for these processes. In the context of a quadratic response, the study has been focused on the Second Harmonic Generation (SHG) process whereby two incident photons at the fundamental wavelength are converted into one photon at twice the harmonic frequency. This process is highly dependent to the metallic nanostructures morphology. For the cubic response, the study has been focused on the optical Kerr effect which describes the optical index variation of nanostructure with the intensity of the incident wave.Specifics considerations have been taken into account about the geometrical illumination conditions which are performed with a large numerical aperture. The electromagnetic incident field cannot be anymore considered within the paraxial approximation
Er-Rhaimini, Salih. "Reconstruction d'image par rétrodiffusion stimulée Raman et amélioration du rendement de conversion". Angers, 1995. http://www.theses.fr/1995ANGE0007.
Pełny tekst źródłaSilva, II Gentil Luiz da. "Amplificação de ruído em um meio Kerr com resposta não-linear não-instantânea em pulsos parcialmente coerentes". Universidade Federal de Alagoas, 2014. http://www.repositorio.ufal.br/handle/riufal/1670.
Pełny tekst źródłaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Considerando a não-linearidade não-instantânea do tipo Kerr, a propagacão de um pulso parcialmente coerente é estudado teoricamente através do uso de extensões na equação não linear de Schrödinger. Para isso, levamos em conta um modelo de difusão de fase no pulso parcialmente coerente. Para incorporar o tempo de resposta finito no meio Kerr, utilizamos uma dependência temporal na resposta não linear do meio introduzida na equação não linear de Schrödinger através do modelo de relaxação de Debye. Deduzimos analiticamente também a relação de dispersão e computamos numericamente o espectro de ganho e algumas quantidades estatísticas de segunda ordem relevantes. Neste trabalho realizamos também um estudo detalhado de como estas propriedades estatísticas são influenciadas pelos regimes de dispersão da velocidade de grupo, tanto quanto pelo atraso na resposta não linear do meio em questão. Por fim, enfatizamos as diferentes características para as respostas não lineares rápidas e lentas. Em outra vertente deste trabalho, realizamos estudos teóoricos acerca de tais características estatísticas para o regime de dispersão zero.
Dremetsika, Evdokia. "Nonlinear optics in graphene: Detailed characterization for application in photonic circuits". Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/264211.
Pełny tekst źródłaDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Jenneve, Philippe. "Analyse Expérimentale des Distorsions Non-Linéaires pour la Construction d’un Estimateur de Performances des Réseaux Optiques Cohérents". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLO014.
Pełny tekst źródłaNowadays, high-speed fiber-optic communication networks are the basis of information technology and the subject of intense research. Innovation enables transponders to be flexible and versatile, but fiber optical networks are still configured manually and especially almost never tuned during the life of the network. One of the blocking points toward reconfigurable and automated optical networks is the need of performance prediction for any link of the network in an accurate and fast way. However, the prediction is made even more complex by the diversity of deployed optical fiber types and propagation regimes.During my work, I addressed experimentally the signal distortions coming from nonlinear Kerr effects accumulated on hundreds of kilometers of optical fibers. Based on specific and controlled experiments, I have measured and highlighted the properties of the nonlinear distortions. These analyses allowed me to design a performance model estimator that can be applied to heterogeneous optical links with various optical fiber types and propagation regimes.The flexibility of transponders associated with a performance estimator will optimize and tune the channels dynamically depending on the load and the topology of the network, as well as compute the protection and restoration links
Mauger, Sarah. "Couplage entre auto-focalisation et diffusion Brillouin stimulée pour une impulsion laser nanoseconde dans la silice". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00638962.
Pełny tekst źródłaBoughdad, Omar. "Fluides de lumière dans un milieu non-linéaire photoréfractif". Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4014.
Pełny tekst źródłaThis 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
Beenken, Wichard Johann Daniel. "Theory of nonlinear polarization spectroscopy in the frequency domain (NLPF) with applications to photosynthetic antennae". Doctoral thesis, [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970522789.
Pełny tekst źródłaLefkir, Miloud. "Mesure des susceptibilités non linéaires d'ordre trois par auto-modification de l'état de polarisation d'une onde lumineuse : rôle des gradients transversés du champ". Angers, 1996. http://www.theses.fr/1996ANGE0025.
Pełny tekst źródłaRolle, Jérémie. "Étude de la dynamique plasma dans la filamentation laser induite dans les verres de silice en présence de rétrodiffusion Brillouin stimulée et dans les cristaux de KDP". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112195/document.
Pełny tekst źródłaIn this thesis, we study the role of an inertial plasma reponse produced by laser pulses in self-focusing regime. Self-focusing is coupled with Brillouin nonlinearities for nanosecond pulses in silica glasses. For femtosecond pulses propagating in KDP crystals, self-focusing excites various ionization chanels. First of all, we derive the propagation equations for the pump and Stokes waves, subjected to filamentation due to optical Kerr effect, stimulated Brillouin scattering and plasma generation. In the second part, we present numerical results on the nonlinear propagation of LIL laser beams. These results show that temporal distribution of the pump pulse play a key role in the competition between self-focusing and stimulated Brillouin scattering. These preliminary results valide the anti-Brillouin system opted on the MegaJoule laser (LMJ) on the basis of milimetric-size laser beam.In a third part, we present numerical and theoretical results on the filamentation in fused silica of nanosecond light pulses operating in ultraviolet and infrared range. Emphasis is put on the action of a dynamical plasma reponse on two counterpropagating waves. For a single wave, we develop a variational analysis which reproduces global propagation features for a quasistationary balance between self-focusing and plasma defocusing. However, such a quasistionary balance ceases to clean up modulational instabilites induced by plasma retroaction on the pump wave. We show that phase modulations supress both simulated Brillouin scattering and plasma instabilities. The robustness of phase modulations is evaluated in presence of random fluctuations in the input pump pulse profile.Finally, we study numerically the nonlinear propagation of femtosecond pulses in fused silica and KDP. First, we show that the presence of defects involving less photons for exciting electrons from the valence band to the conduction band promotes higher filamentation intensity levels. Then, we compare the filamentation dynamic in silica and KDP crystal. The ionization model for KDP crystal takes into account the presence of defects and the electron-hole dynamics. We show that the propagation dynamics in silica and KDP are almost identical at equivalent ratios of input power over the critical power self-focusing.The summary of this thesis recalls the original results obtained and discusses the possibility of future developments
Araújo, Michelle Oliveira de. "Investigação experimental e modelo teórico para o índice de refração não-linear da linha D2 do césio". Universidade Federal da Paraíba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/5739.
Pełny tekst źródłaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The response of a material to an incident radiation can be described in terms of the susceptibility of the medium. In an atomic vapor, this susceptibility strongly depends on the frequency of the radiation and can vary over several orders of magnitude near the resonance. When a material is illuminated by light whose electric field is intense, the Kerr effect may become significant, showing a linear variation of the refractive index as a function of the intensity of the laser beam. Several techniques allow the measurement of this nonlinear effect. One of the simplest and most accurate is the z-scan technique. It consists in moving the medium to be probed along the axis of a focused laser beam. The transmittance through an aperture is measured as a function of the cell position and the obtained curve allows one to determine the nonlinear refractive index (n2) of the material. In this work, we investigate the nonlinear refractive index of a vapor of cesium atoms. We used the z-scan technique for various detunings around the Cs D2 transition (wavelength at 852 nm). To monitor the frequency of the laser, we simultaneously used an auxiliary saturated absorption setup and a Fabry-Perot analyzer. Through simple relationships between n2 and the aperture transmittance, we obtained a value for n2 as a function of the laser detuning. A theoretical model was developed to be compared to our experimental results. We used the density matrix formalism to calculate n2, taking into account the velocity distribution of the atoms in the calculation of the matrix elements. We started by treating the atoms as two-level systems, which allows us to test different limits of velocity integration. We then carried out a more realistic model for the D2 line of Cs, considering one fundamental level and three excited levels. We showed that for each hyperfine transition, the third-order fundamental-excited coherence depends on the population of the excited states as well as on the coherence created between the excited levels. To our knowledge, our experimental results are the first measurements of n2 for a cesium vapor, using the z-scan technique. The measured values of n2 are consistent with our theoretical calculations.
A resposta de um meio material à radiação incidente pode ser descrita em termos da susceptibilidade ótica desse meio. Em vapores atômicos, essa susceptibilidade depende fortemente da freqüência da radiação e pode variar, em torno da ressonância, por várias ordens de grandeza. Quando um material é iluminado por um feixe de luz cujo campo elétrico é muito intenso, evidencia-se o efeito Kerr, ou seja, o próprio índice de refração do material varia linearmente com a intensidade do feixe laser. Para medir esse efeito não linear da polarização do material, existem varias técnicas na literatura. Uma das mais simples e precisa é a varredura z (z-scan). O z-scan consiste em deslocar o meio a ser estudado ao longo do eixo de um feixe laser focalizado. Mede-se então a transmitância através de uma abertura, em função da posição da célula. A partir dessa curva de transmitância, é possível determinar o índice de refração não linear do material. Neste trabalho, investigamos a dependência espectral do índice de refração não linear do vapor atômico de césio. Realizamos experimentos com a técnica z-scan para várias dessintonizações na linha D2 (comprimento de onda de 852 nm). O monitoramento da freqüência do laser é feito através de uma montagem auxiliar de absorção saturada e de uma cavidade Fabry-Pérot. Utilizando relações simples entre n2 e a transmitância na abertura, obtivemos um valor de n2 para cada dessintonização. Para interpretar os resultados experimentais, usamos o formalismo de matriz densidade para calcular teoricamente o n2. No cálculo dos elementos da matriz densidade, deve-se levar em consideração a distribuição de velocidades dos átomos. Iniciamos nosso modelo tratando os átomos como sistemas de dois níveis, com o objetivo de compreender os diferentes limites da integração em velocidade. Em seguida passamos para um modelo mais realista para a linha D2 do Cs envolvendo um nível fundamental e três excitados. Mostramos que, para cada transição hiperfina, a coerência fundamental-excitada de terceira ordem depende de efeito de população dos estados excitados e da coerência criada entre eles. Nossos resultados experimentais são, até onde sabemos, as primeiras medidas usando z-scan para a obtenção do indice de refração de vapor de césio. Os valores medidos de n2 são condizentes com os nossos cálculos teóricos.
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.
Pełny tekst źródłaDoclot, Olivier. "Etude des propriétés optiques non linéaires de troisième ordre de la molécule et du cristal de 4-(N,N diéthylamino)-b-nitrostyrène par Z scan et ellipsométrie". Grenoble 1, 1996. http://www.theses.fr/1996GRE10230.
Pełny tekst źródła"Multi-wavelength optical Kerr effects in high nonlinearity single mode fibers and their applications in nonlinear signal processing". 2006. http://library.cuhk.edu.hk/record=b5892974.
Pełny tekst źródłaThesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references.
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- All-Optical Signal Processing in Optical Communications --- p.2
Chapter 1.2 --- Fiber-Based Optical Kerr Nonlinear Switches --- p.5
Chapter 1.3 --- Highly Nonlinear Fibers --- p.6
Chapter 1.4 --- Objectives and Scope of Study --- p.8
Chapter 1.5 --- Summary --- p.9
Chapter Chapter 2 --- Optical Nonlinearity --- p.14
Chapter 2.1 --- Fiber Nonlinearity --- p.15
Chapter 2.2 --- Dispersion --- p.21
Chapter 2.3 --- Cross-Phase Modulation --- p.26
Chapter 2.4 --- Cross-Polarization Modulation --- p.29
Chapter Chapter 3 --- Fibers: The Nonlinear Media --- p.47
Chapter 3.1 --- Average Dispersion --- p.48
Chapter 3.2 --- Longitudinal Dispersion Map --- p.53
Chapter 3.3 --- Nonlinear Refractive Index and Nonlinear Coefficient --- p.57
Chapter 3.4 --- Electrostrictive Contribution --- p.62
Chapter 3.5 --- List of the Fiber Properties --- p.66
Chapter Chapter 4 --- Multi-Wavelength Nonlinear Signal Processing --- p.69
Chapter 4.1 --- Challenge --- p.70
Chapter 4.2 --- Applications --- p.72
Chapter 4.3 --- Proposed System Application --- p.110
Chapter Chapter 5 --- Conclusion and Future Work --- p.114
Chapter 5.1 --- Comparisons between Proposed and Existing Approaches --- p.114
Chapter 5.2 --- Conclusion of the Dissertation --- p.115
Chapter 5.3 --- Prospects and Directions of Future Work --- p.117
Appdenix A Numerical Model for Dispersion Calculation --- p.I
Appdenix B Simulation Model of Wide Band Cross-Polarization Switch --- p.III
Appdenix C Simulation Model of Spectral Filtering under XPM --- p.VI
List of Publications --- p.IX
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.
Pełny tekst źródłaThesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-10-19 14:11:53.826
"Study of nonlinear optical properties of fullerenes and related compounds by optical Kerr effect: 應用光學克爾效應硏究足球烯分子及有關化合物之非線性光學性質". 1997. http://library.cuhk.edu.hk/record=b5889269.
Pełny tekst źródłaThesis (M.Phil.)--Chinese University of Hong Kong, 1997.
Includes bibliographical references.
Yung, Man Fai.
Acknowledgements --- p.iii
Abstract --- p.iv
Preface --- p.vi
Contents --- p.vii
List of Figures --- p.x
List of Tables --- p.xii
Chapter Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Physical Origin of Optical Nonlinearity --- p.3
Chapter 1.1.1 --- Mathematical Description --- p.3
Chapter 1.1.2 --- Anharmonic Oscillator Model --- p.4
Chapter 1.2 --- Nonlinear Optical Susceptibility --- p.4
Chapter 1.2.1 --- Molecular Hyperpolarizability --- p.4
Chapter 1.2.2 --- Macroscopic Nonlinear Susceptibility --- p.5
Chapter 1.2.3 --- Kleinman Conjecture --- p.6
Chapter 1.3 --- Third-Order Nonlinear Optical Process --- p.7
Chapter 1.3.1 --- Intensity Dependent Refractive Index --- p.7
Chapter 1.3.2 --- Physical Mechanisms --- p.8
Chapter 1.3.3 --- Tensor Nature of Third-Order Susceptibility x(3) --- p.10
Chapter 1.3.4 --- Conventions for Nonlinear Susceptibility --- p.11
References --- p.12
Chapter Chapter 2. --- Optical Kerr Effect --- p.13
Chapter 2.1 --- Introduction --- p.13
Chapter 2.2 --- Theoretical Background --- p.14
Chapter 2.2.1 --- Pump-Probe Technique --- p.14
Chapter 2.2.2 --- Description of Induced Birefringence --- p.15
Chapter 2.2.3 --- Signal Transmitted through OKE --- p.17
Chapter 2.2.4 --- Resonant OKE --- p.18
Chapter 2.2.5 --- Third-Order Autocorrelation --- p.19
Chapter 2.3 --- Applications --- p.20
References --- p.21
Tables --- p.23
Figure Captions --- p.24
Chapter Chapter 3. --- Nonlinear Optical Properties of Fullerenes --- p.26
Chapter 3.1 --- Introduction --- p.26
Chapter 3.2 --- Second Harmonic Generation --- p.27
Chapter 3.3 --- Third-Order Effects --- p.28
Chapter 3.4 --- Reverse Saturable Absorption and Optical Limiting --- p.29
References --- p.32
Figure Captions --- p.34
Chapter Chapter 4. --- Excited State Enhancement --- p.38
Chapter 4.1 --- Introduction --- p.38
Chapter 4.2 --- Origin and Properties of Excited State Enhancement --- p.39
Chapter 4.3 --- Experimental Demonstrations --- p.42
References --- p.44
Chapter Chapter 5. --- Experimental Setup --- p.46
Chapter 5.1 --- Introduction --- p.46
Chapter 5.2 --- Laser System --- p.46
Chapter 5.3 --- Optical Layout --- p.48
Chapter 5.4 --- Sample Preparation --- p.50
Chapter 5.5 --- Detection System --- p.51
Chapter 5.6 --- Third-Order Autocorrelation Measurement --- p.52
Chapter 5.7 --- Optical Limiting Measurement --- p.53
Chapter 5.8 --- Excited State Enhancement Measurement --- p.54
References --- p.56
Figure Captions --- p.57
Chapter Chapter 6. --- Results and Discussion --- p.69
Chapter 6.1 --- Introduction --- p.69
Chapter 6.2 --- Results of Pure Liquids --- p.69
Chapter 6.2.1 --- Carbon Disulfide (CS2) --- p.69
Chapter 6.2.2 --- Toluene --- p.71
Chapter 6.2.3 --- Nitrobenzene --- p.71
Chapter 6.3 --- Third-Order Autocorrelation of CS2 --- p.74
Chapter 6.4 --- Results of Fullerenes C60 and C70 --- p.75
Chapter 6.5 --- Optical Limiting of C60 --- p.78
Chapter 6.6 --- Excited State Enhancement of Fullerenes --- p.79
References --- p.82
Tables --- p.85
Figure Captions --- p.90
Chapter Chapter 7. --- Conclusion --- p.108
MARCUCCI, GIULIA. "Complex extreme nonlinear waves: classical and quantum theory for new computing models". Doctoral thesis, 2020. http://hdl.handle.net/11573/1353250.
Pełny tekst źródłaFilippov, Oleg. "Vectorial beam coupling in fast photorefractive crystals with AC-enhanced response". Doctoral thesis, 2004. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2004092812.
Pełny tekst źródłaSu, Sheng-Pin, i 蘇聖斌. "Nano-scale Si doped Si-rich SiOx/ Si-rich SiNx/Si-rich SiCx ring waveguide based all-optical modulator using linear free-carrier absorption and nonlinear Kerr effect". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/81327990858089791098.
Pełny tekst źródła國立臺灣大學
光電工程學研究所
102
In this thesis, we simulate, fabricate and analyze the Si-QD doped Si-rich SiOx/ Si-rich SiCx/ Si-rich SiNx micro-ring waveguide resonator based all-optical modulator using linear free-carrier absorption and nonlinear Kerr effect. In the chapter 2, by integrating with a ring-resonator waveguide, the Si quantum dot doped SiOx strip-loaded waveguide based free-carrier absorption modulator with enhanced FCA loss modulation is demonstrated by different pumping wavelengths. The micro-ring waveguide resonator induced a dark-comb like throughput transfer function in wavelength domain, in which function with a Q-factor of 6×103 can be blue-shifted by varying the photo-excited electron-hole plasma density. When transmitting optical data stream at the central wavelength of any notch in the dark-comb throughput function, the output data-stream can be inverted by pumping the micro-ring waveguide resonator to up-shift the notch away from its original wavelength. As a result, this maximize the extinction ratio of output data stream. The largest FCA loss and highest free-carrier density can be enhanced up to 3.44 cm-1 and 9.29×1016 cm-3, respectively, at excitation intensity as high as 6.7 W/cm2. By adding the micro-ring waveguide resonator, the modulation depth can be further enhanced from 52.5% to 63.5% by up-shifting the transfer function of the micro-ring waveguide resonator with the photo-excited e-h plasma. The maximal wavelength of the transmittance notch shift can be up to 0.033 nm under the same pumping intensity at wavelength of 1563.42 nm. The excited free-carriers inside the micro-ring waveguide resonator is obtained to be ~5.25×1015 cm-3. The pumping wavelength dependent transmission notch linewidth is broadened from 0.26 nm to 0.3 nm when the ring waveguide resonator is pumped by 325-nm HeCd laser. Due to the speed of FCA based modulator is limited by the carrier lifetime which the modulation speed of SiOx:Si-QD is ~ 1 μs. As a result, the ultrafast nonlinear optical Kerr effect is employed in the following work. In the chapter 3, the ultrafast optical Kerr switch with a Si-rich SiC micro-ring resonator is demonstrated. In addition, the nonlinear refractive index of Si-rich SiC at telecommunication wavelengths is firstly estimated by the resonance red-shift, which is still unknown in the literature. With the 12 Gbit/s NRZ-OOK optical pump data-stream, the Si-rich SiC micro-ring resonator shows a great applicability in the real optical communication system. From the maximal inverted probe signal, the red-shift of resonance dip is 0.07 nm corresponding to refractive index change of 1.2×10-4. By the red-shift of resonance dip, the nonlinear refractive index of Si-rich SiC is estimated to be n2=3.14×10-13 cm2/W, which is several orders magnitude larger than that in SiC. From the analyses of XPS and the RSS, the excessive Si concentration of 37.2% which exist in the form of Si-QDs is observed. The existence of Si-QDs buried in the Si-rich SiC matrix can effectively result in a huge enhancement on the nonlinear refractive index, which can be explained by the quantum confinement effect. From the BPM analysis under single-mode condition, the waveguide width and height of 600 nm and 300 nm is determined. The fabricated micro-ring waveguide resonator is obtain with Q=22800 and the transmittance drop of nearly 60% at a wavelength of 1551.08 nm. In the chapter 4, the 12 Gbit/s optical Kerr switch has been demonstrated with a Si-rich SiN micro-ring resonator in the first time. The Si-rich SiN with excessive Si of 23.4% is grown by PECVD process with fluence ratio of [SiH4]/[NH3] equals 0.9. The fabricated mirco-ring resonator of Q=11000 is observed, which provides a field enhancement inside the micro ring resonator. By introducing the 12 Gbit/s NRZ-OOK data stream as the optical pump format, the ultra-fast response up to 83 ps of the Si-rich SiN micro-ring resonator shows a great applicability in the real-world optical communication system. The SNR is degraded from 9.66 dB to 5.32 dB after the wavelength conversion. According to the ultrafast response of nonlinear Kerr effect, the nonlinear refractive index of Si3N4:Si-QD at near-infrared wavelengths for optical telecommunications is instantly modified by the input optical data stream to cause the red-shift on the resonance of the micro-ring, thus providing a high-speed optical switch up to 12 Gbit/s via the cross-wavelength amplitude modulation effect. By analyzing the resonance dip red-shift of 0.13 nm corresponding toδn=2.2×10-4, the nonlinear refractive index of the Si-rich SiN is estimated as n2=δn/Ir=2.17×10-13 cm2/W, which is one order and two orders of magnitude larger than that in Si and SiN, respectively.
Badorreck, Holger. "Nichtlineare Optik mit ultrakurzen Laserpulsen: Suszeptibilität dritter Ordnung und kleine Polaronen sowie Interferenz und Holographie verschiedenfarbiger Laserpulse". Doctoral thesis, 2016. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2016061314530.
Pełny tekst źródłaAllodi, Marco Alberto. "On Ultrafast Time-Domain TeraHertz Spectroscopy in the Condensed Phase: Linear Spectroscopic Measurements of Hydrogen-Bond Dynamics of Astrochemical Ice Analogs and Nonlinear TeraHertz Kerr Effect Measurements of Vibrational Quantum Beats". Thesis, 2015. https://thesis.library.caltech.edu/8949/10/marco_allodi_thesis_2015.pdf.
Pełny tekst źródłaMuch of the chemistry that affects life on planet Earth occurs in the condensed phase. The TeraHertz (THz) or far-infrared (far-IR) region of the electromagnetic spectrum (from 0.1 THz to 10 THz, 3 cm-1 to 300 cm-1, or 3000 μm to 30 μm) has been shown to provide unique possibilities in the study of condensed-phase processes. The goal of this work is to expand the possibilities available in the THz region and undertake new investigations of fundamental interest to chemistry. Since we are fundamentally interested in condensed-phase processes, this thesis focuses on two areas where THz spectroscopy can provide new understanding: astrochemistry and solvation science. To advance these fields, we had to develop new instrumentation that would enable the experiments necessary to answer new questions in either astrochemistry or solvation science. We first developed a new experimental setup capable of studying astrochemical ice analogs in both the TeraHertz (THz), or far-Infrared (far-IR), region (0.3 - 7.5 THz; 10 - 250 cm-1) and the mid-IR (400 - 4000 cm-1). The importance of astrochemical ices lies in their key role in the formation of complex organic molecules, such as amino acids and sugars in space. Thus, the instruments are capable of performing variety of spectroscopic studies that can provide especially relevant laboratory data to support astronomical observations from telescopes such as the Herschel Space Telescope, the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the Atacama Large Millimeter Array (ALMA). The experimental apparatus uses a THz time-domain spectrometer, with a 1750/875 nm plasma source and a GaP detector crystal, to cover the bandwidth mentioned above with ~10 GHz (~0.3 cm-1) resolution.
Using the above instrumentation, experimental spectra of astrochemical ice analogs of water and carbon dioxide in pure, mixed, and layered ices were collected at different temperatures under high vacuum conditions with the goal of investigating the structure of the ice. We tentatively observe a new feature in both amorphous solid water and crystalline water at 33 cm-1 (1 THz). In addition, our studies of mixed and layered ices show how it is possible to identify the location of carbon dioxide as it segregates within the ice by observing its effect on the THz spectrum of water ice. The THz spectra of mixed and layered ices are further analyzed by fitting their spectra features to those of pure amorphous solid water and crystalline water ice to quantify the effects of temperature changes on structure. From the results of this work, it appears that THz spectroscopy is potentially well suited to study thermal transformations within the ice.
To advance the study of liquids with THz spectroscopy, we developed a new ultrafast nonlinear THz spectroscopic technique: heterodyne-detected, ultrafast THz Kerr effect (TKE) spectroscopy. We implemented a heterodyne-detection scheme into a TKE spectrometer that uses a stilbazoiumbased THz emitter, 4-N,N-dimethylamino-4-N-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS), and high numerical aperture optics which generates THz electric field in excess of 300 kV/cm, in the sample. This allows us to report the first measurement of quantum beats at terahertz (THz) frequencies that result from vibrational coherences initiated by the nonlinear, dipolar interaction of a broadband, high-energy, (sub)picosecond THz pulse with the sample. Our instrument improves on both the frequency coverage, and sensitivity previously reported; it also ensures a backgroundless measurement of the THz Kerr effect in pure liquids. For liquid diiodomethane, we observe a quantum beat at 3.66 THz (122 cm-1), in exact agreement with the fundamental transition frequency of the υ4 vibration of the molecule. This result provides new insight into dipolar vs. Raman selection rules at terahertz frequencies.
To conclude we discuss future directions for the nonlinear THz spectroscopy in the Blake lab. We report the first results from an experiment using a plasma-based THz source for nonlinear spectroscopy that has the potential to enable nonlinear THz spectra with a sub-100 fs temporal resolution, and how the optics involved in the plasma mechanism can enable THz pulse shaping. Finally, we discuss how a single-shot THz detection scheme could improve the acquisition of THz data and how such a scheme could be implemented in the Blake lab. The instruments developed herein will hopefully remain a part of the groups core competencies and serve as building blocks for the next generation of THz instrumentation that pushes the frontiers of both chemistry and the scientific enterprise as a whole.
Χατζηκυριάκος, Γεώργιος. "Μη-γραμμικές οπτικές ιδιότητες μεταλλικών νανοσωματιδίων (Pd, οξειδίων σιδήρου), διθειολενικών συμπλόκων και φουλλερενικών παραγώγων". Thesis, 2011. http://hdl.handle.net/10889/5097.
Pełny tekst źródłaThe field of optics that examines the interaction of matter with very high intensity radiation is called nonlinear optics. When a material is exposed to radiation with high intensity such as the radiation emitted by a laser, the optical properties of the material change as a result of the induced polarization that occurs in the atoms or the molecules that constitute the material. This in turn can lead to a variety of phenomena that helps us to understand and establish relations between the structure and the physical mechanisms that take place when light interacts with matter. Materials with large nonlinear optical properties are considered possible candidates for applications in a wide range of technology such us optical or quantum computers or even in the field of telecommunications. In this work the nonlinear optical properties of metallic nanoparticles, organometallic molecules and fullerene derivates is examined. The investigated systems were in form of solutions and the nonlinear optical properties were determined with the use of Z-scan and OKE techniques. The laser pulse duration was 35 ps and 4 ns, while the excitation wavelength was 532 nm and 1064 nm respectively. In the first chapter an introduction is presented to some elements of the field of nonlinear optics. Then the derivation of the relations that describe the nonlinear optical parameters like the third order susceptibility (χ(3)) with the use of electromagnetic theory and quantum mechanics is presented. At the end some interesting phenomena that occur as a result of third order susceptibility are described. The second chapter is devoted to the experimental techniques that were used to determine the nonlinear optical properties of the investigated systems that are presented in this work. The Z-scan and OKE techniques are described thoroughly as well and the process of the determination of the nonlinear optical properties from the experimental data. In the next four chapters, experimental results are presented of the nonlinear optical properties for all the systems that were studied during this work. At the third chapter the results for γ-Fe2O3 nanoparticles are presented. Those systems were either covered or uncovered with polymeric brushes, and had different sizes of the nanoparticle core. The results show that the presence or not of the polymeric brushes, as well and the size of the core has an impact on the nonlinear optical properties those systems. In chapter four are presented the results from the investigation of the nonlinear optical properties of Pd nanoparticles encapsulated into amphiphilic block copolymer micelles. The investigation was done under 35 ps and 4 ns laser pulse duration at excitation wavelengths of 532 and 1064 nm. It is concluded that the NLO response of the systems is depending on the size of the micelle, the shape but also from the metallic load of the micelle. In the final two chapters they are presented the results regarding the NLO properties of organometallic and fullerene derivates molecules. In chapter five the investigation of the nonlinear optical properties of various dithiolene complexes is presented, under 35 ps laser pulse duration at 532 and 1064 nm. The results shows that the central atom attached to the molecule is playing crucial role to the NLO response but also and the number and the nature of substituent attached to the molecule. At the final chapter the determined NLO properties of some donor – acceptor fullerene derivatives are presented. The results show that functionalized fullerene derivatives have greater NLO response than the neat fullerene making them promising candidates for applications in optoelectronics and all-optical switching.
Wagner, Sean. "Wavelength Conversion in Domain-disordered Quasi-phase Matching Superlattice Waveguides". Thesis, 2011. http://hdl.handle.net/1807/29903.
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