Ce travail porte sur l'étude de la cohérence entre champs triplets générés par interaction non linéaire d'ordre trois. Un protocole indirect, basé sur l'étude du champ issu de la somme de fréquences des champs triplets dans un cristal non linéaire a été envisagé. Une modélisation théorique en formalisme quantique de l'évolution des champs, de leur génération à leur recombinaison, a été développée, donnant lieu à une recherche exhaustive des signatures de corrélations susceptibles d'émerger de notre protocole. Les expériences menées, à savoir la génération non linéaire bi-stimulée et la recombinaison des champs ainsi générés, sont en accord avec notre modèle théorique et permettent de mettre en évidence le masquage des corrélations entre les champs dans ce régime fortement injecté, ces corrélations étant contenues dans les fluctuations quantiques, alors négligeables, des opérateurs champs. Le calcul théorique prédit une signature de corrélations fortes entre les photons triplets dans la cas d'un génération par fluorescence paramétrique, et plus faible dans le cas d'une génération mono-stimulée. / This work deals about the study of coherence between triple photon beams generated by a third order non linear interaction. A protocol, based on the study of the field arising from sum-frequency of the triplet fields in a non linear crystal, was proposed. A theoretical model, in the quantum formalism, was developed, leading to an exhaustive research of the potential signature of the correlations. All the possible schemes were studied : triple fields generation from parametric fluorescence or from stimulated interaction, and recombination of two or three of the triple fields. The experiments we led, i.e. the bi-stimulated non linear generation and the recombination of the so-born fields, agree with our theoretical model and put into light the correlations hiding in this highly stimulated regime, since these correlations lie in the quantum fluctuations of the fields operators. The theoretical calculations predicts a strong correlations signature when the fields are generated from parametric fluorescence, and a weaker one in the case of a generation mono-stimulated.

D'importants progrès ont été accomplis dans le domaine des matériaux à transition despin depuis leur première observation par Cambi en 1931. La combinaison de lachiralité avec le magnétisme résulte en de nouvelles propriétés très intéressantes quiouvrent la voie pour de potentielles applications technologiques. Ce manuscrit décritles résultats obtenus par diverses stratégies poursuivies vers des matériauxmoléculaires non-centrosymétriques à transition de spin par combinaison decomplexes à transition de spin avec des anions chiraux à symétries D3 et D2. / Many advancements in the field of spin crossover materials have been carried outsince the first observation by Cambi in 1931. The combination of chirality andmagnetism yields fascinating properties that open the way for potential technologicalapplications. Obtaining new non-centrosymmetric magnetic compounds yieldsinteresting subjects for non-linear optical studies or crystallography. This manuscriptdescribes the results obtained by various strategies pursued toward spin crossovernon-centrosymmetric molecular materials by combining spin crossover complexes withchiral anions based on D3 and D2 symmetric anions.

Diese Arbeit beinhaltet experimentelle und theoretische Untersuchungen der optischen Frequenzverdopplung (second-harmonic generation, kurz SHG) an metallischen Nanopartikeln. Frequenzverdopplung bedeutet, daß ein bei der Frequenz omega angeregtes Nanopartikel Strahlung der Frequenz 2*omega emittiert. Dieser Effekt tritt nicht nur in Materialien mit nichtzentrosymmetrischer Kristallstruktur, sondern auch an der Oberfläche von Metallen auf. Deshalb läßt er sich gut mit plasmonischen Feldüberhöhungen an metallischen Nanoantennen verbinden. Die Frequenzverdopplung wird an verschiedenen Nanostrukturen wie dreieckförmigen, stäbchenförmigen und vor allem kegelförmigen Nanopartikeln experimentell untersucht, welche aufgrund ihrer scharfen Spitzen starke SHG-Signale emittieren. Besonders die Kegel sind interessant: Bei Anregung mit einem fokussierten, radial polarisierten Strahl dominiert je nach Kegelgröße und Umgebungsmedium ein SHG-Signal entweder von der Spitze oder von der Bodenkante des Kegels. Diese an den Kegeln gemessenen Resultate werden durch theoretische Untersuchungen untermauert. In diesen Rechnungen werden die plasmonischen Feldüberhöhungen und die sich daraus ergebende Frequenzverdopplung für einen Kegel mit verschiedenen Parametern modelliert. An einem einzelnen Kegel gewonnene Resultate werden auch mit den Fällen eines kugelförmigen und eines stäbchenförmigen Partikels verglichen. Ein weiterer Gegenstand der theoretischen Untersuchungen ist die Superposition der zweiten Harmonischen von mehreren emittierenden Nanopartikeln zu einem Feldmaximum. Dabei wird eine kreisförmige Anordnung von 8 Nanostäbchen bzw. Nanokegeln von einer radial polarisierten Mode angeregt. Die Superposition der emittierten zweiten Harmonischen ergibt ein Feldmaximum innerhalb der Anordnung der Emitter. Durch eine Verkippung des anregenden Strahls kann dieser Fokus im Raum bewegt werden. Letztere Untersuchung ist insbesondere interessant im Hinblick auf lokalisierte photochemische Reaktionen, die durch das frequenzverdoppelte Licht von Nanopartikeln ausgelöst werden sollen. Mit chemischen Substanzen, die bei omega transparent, bei 2*omega aber photoreaktiv sind, wäre im Nahfeld dieser Nanoantennen eine starke Lokalisierung der Reaktion auf Bereiche kleiner als 100~nm möglich. Anhand von Photolacken und Polymermatrizen mit diesen Eigenschaften wird experimentell untersucht, ob frequenzverdoppeltes Licht überhaupt solche Reaktionen auslösen kann oder ob die photochemische Reaktionen überwiegend durch direkte Zwei-Photonen-Absorption des anregenden Lichts ausgelöst werden. Die Ergebnisse zeigen allerdings, daß die Zwei-Photonen-Absorption dominant ist. Durch die Zwei-Photonen-Absorption im Nahfeld von Partikeln ist aber dennoch eine vergleichbare Lokalisierung der Reaktion möglich. / This work includes experimental and theoretical investigations of second-harmonic generation (SHG) at metallic nanoparticles. SHG means that a nanoparticle that is excited at the frequency omega emits radiation at the frequency 2*omega. SHG does not only occur in materials with noncentrosymmetric structure, but also on metal surfaces. Hence, SHG can be combined well with plasmonic field enhancement at metallic nanoantennae. SHG is investigated experimentally at different nanostructures such as triangle-like, rod-like and especially cone-like nanoparticles. With their sharp tips these structures show a much stronger SHG signal than spherical nanoparticles. Especially the cones are interesting: Excited with a focused radially polarized beam, for different cone sizes and in different surrounding media either the signal from the tip or the signal from the bottom edge dominates. The measurement results from the cones are underpinned by theoretical investigations. In these calculations the plasmonic field enhancements and the resulting SHG are modeled for a cone with different parameters. The single-cone results are also compared with the cases of a spherical or rod-shaped particle. A further subject of the theoretical investigations is the superposition of the SHG radiation from a number of emitting nanoparticles to a field maximum. For that, a circular arrangement of 8 nanorods or nanocones is excited by a radially polarized beam. The superposition of the second-harmonic radiation fields yields a field maximum in the space between the emitters. A tilt of the exciting beam can move this focus in space. The latter item is of special interest concerning localised photochemical reactions induced by the second-harmonic light from nanoparticles. In the near field of these nanoantennae, a strong localisation of the reaction on regions smaller than 100 nm would be possible by using chemical substances being transparent at omega, but photoreactive at 2*omega. With photoresists and polymer matrices, experiments are carried out to investigate whether SHG light can trigger such reactions at all, or if these photochemical reactions are triggered predominantly by direct two-photon absorption of the exciting light. The results show that the two-photon absorption is the dominant process. Yet, through two-photon absorption in the near field of particles, the localisation of the reaction is still similar.

Le développement de nanomatériaux à propriétés optiques et fonctionnalisés pour un marquage spécifique est en plein essor dans le domaine de l'imagerie biologique. Parmi les agents de contraste exogènes déjà utilisés, les marqueurs fluorescents tels que les nanocristaux semi-conducteurs (CdSe/ZnS,…) et les molécules organiques naturelles (GFP,…) ou synthétiques (fluorescéine,…) souffrent respectivement de clignotements (blinking) et de photo-blanchiment (bleaching) c'est-à-dire d'une faible tenue au rayonnement lumineux incident. Récemment, la microscopie de Génération de Second Harmonique (GSH) à partir de structures non-centrosymétriques de certains matériaux ou molécules optiquement non linéaires (ONL), s'est révélée un outil particulièrement prometteur. Les inconvénients du clignotement et du photo-blanchiment sont en effet absents pour le processus non linéaire de GSH. De plus, le principe de fonctionnement des marqueurs ONL repose sur un processus non résonant, contrairement aux marqueurs fluorescents, ce qui est un avantage décisif pour le choix de la longueur d'onde d'excitation des nanosondes. Pour des illuminations dans le proche infrarouge, cela permet de limiter l'énergie déposée dans le milieu biologique, d'augmenter la profondeur d'imagerie et enfin de bien séparer spectralement les signaux des marqueurs ONL de l'auto-fluorescence naturelle de certains échantillons. Notre objectif, dans ce contexte, était la synthèse et la caractérisation de nouvelles nanosondes ONL de forme sphérique et de taille inférieure à 100nm. Le matériau de structure cristalline non centrosymétrique retenu est l'iodate de fer (Fe(IO3)3) car ses éléments chimiques sont peu toxiques et que ses propriétés paramagnétiques peuvent également donner un contraste en imagerie par résonance magnétique (IRM) ce qui est potentiellement intéressant par rapport à d'autres cristaux ONL tels que ZnO, KNbO3, BaTiO3 et KTP. D'un point de vue synthèse, les microémulsions inverses sont bien référencées dans la littérature pour leur rôle de gabarit permettant un bon contrôle de la taille et de la morphologie des nanomatériaux obtenus par co-précipitation. Dans ce travail, les nano-réacteurs ont été préparés à partir des systèmes AOT/alcane/eau et Triton/1-hexanol/cyclohexane/eau. De manière très originale et pratique, le développement d'un banc optique de diffusion Hyper-Rayleigh (HRS) a permis de suivre in-situ et en temps réel les cinétiques de cristallisation des nanoparticules de Fe(IO3)3 en fonction de conditions expérimentales variables. Les mécanismes de croissance et de cristallisation des nano-bâtonnets de Fe(IO3)3 ont été élucidés en combinant d'autres techniques physico-chimiques usuelles comme la diffraction des rayons X, la diffusion dynamique de la lumière et la microscopie électronique en transmission. Nous avons démontré que la température et la nature du tensioactif influencent les forces d'interaction à l'interface organique-inorganique ce qui permet, pour certaines conditions expérimentales, de réduire la taille et la polydispersité des nanocristaux en fin de processus. Toutefois, avant d'envisager l'utilisation de ces derniers en tant que marqueurs optiques spécifiques, il est nécessaire d'encapsuler ces nanocristaux en raison de la faible stabilité du composé aux pH physiologiques. Les premiers essais de stabilisation en microémulsions par une couche de silice ont permis d'obtenir des nanoparticules de taille ~ 10 nm avec une forte réponse ONL. La caractérisation complète et la fonctionnalisation de ces nanostructures ainsi qu'une optimisation des interactions à l'interface particules – films de tensioactifs constituent les perspectives de ce travail. / The development of functionalized nanomaterials with optical properties for a site-specific labeling or conjugation has undergone a rapid growth in the biological imaging field. Among the exogenous contrast agents which are already used, fluorescent nanocrystals such as semi-conductor (CdSe / ZnS, ...) and natural organic molecules (GFP, ...) or synthetic molecules (fluorescein, ...) suffer from blinking and photobleaching, respectively. Recently, Second Harmonic Generation (SHG) from acentric structures of some Non-Linear Optical (NLO) materials or organic molecules appeared to be particularly promising. Indeed, the major disadvantages of blinking and photobleaching are absent in the SHG process. Additionally, imaging of NLO probes is based on a non-resonant process, contrary to traditional fluorescent probes, which is key in terms of excitation wavelength. Near infrared illumination can limit the energy deposited in the biological tissues, increase the imaging depth and, finally, the SHG signal can be more readily spectrally resolved from the natural auto-fluorescence. The main objectives of this thesis were the synthesis and characterization of new NLO nanoprobes with a spherical shape and a size lower than 100 nm. The non-centrosymmetric material of interest is iron iodate (Fe(IO3)3). Its chemical elements are non toxic and its paramagnetic response may also provide a contrast in Magnetic Resonance Imaging (MRI) which is not the case of the other NLO crystals such as ZnO, KNbO3, BaTiO3 and KTP. From a synthesis point of view, reverse microemulsions are well documented in the literature as good templates for the size and shape control of nanomaterials obtained by a coprecipitation reaction. In this work, nanoreactors were prepared from the AOT/alkane/water and Triton/1-hexanol /cyclohexane/water systems..A very original and convenient setup based on the Hyper-Rayleigh Scattering (HRS) was implemented so that the real-time crystallization kinetics of the growing acentric iron iodate nanocrystals in microemulsions could be measured according to different experimental conditions. We demonstrate that HRS is a fast, valuable and nondestructive alternative to probe in-situ the crystallization and growth dynamics of Fe(IO3)3 nanorods whereas the growth mechanism was elucidated by a combination of Dynamic Light Scattering, X-ray diffraction and Transmission Electron Microscopy experiments. The binding interaction between surfactant molecules and colloidal particles was studied as a function of the synthesis temperature as well as the surfactant nature. In some experimental conditions the size and polydispersity of the final nanorods can be thus reduced. However, the use of iron iodate as specific NLO optical probes is so far restricted due to its low stability at physiological pH. Preliminary encapsulation tests by a thin silica-coating in reverse microemulsions show the presence of ~ 10nm nanocparticles with a strong NLO response. The complete characterization and functionalization of these nanostructures as well as the optimization of the binding interactions at the organic-inorganic interface are the prospects of this work

Le développement de nouveaux capteurs, transducteurs et de dispositifs intégrés optoélectroniques et piézo-électriques nécessite l'élaboration de nouveaux matériaux avec des propriétés mécaniques, optiques et électriques couplées. Dans cette perspective, les nanocomposites à base de nanocristaux inorganiques non centrosymétriques dispersés dans une matrice polymère peuvent donner à la fois des propriétés piézoélectriques et optiques non-linéaires. Cependant, la dispersion et l’orientation des nanocristaux dans la matrice sont primordiales si on souhaite un comportement collectif des nanocristaux individuels et des propriétés résultantes significatives. Dans ce travail, nous avons utilisé des cristaux d’iodate de fer (Fe(IO3)3) comme nano-charges inorganiques et le PMMA/ PTMPTA comme matrice polymère. La réponse optique non-linéaire du Fe(IO3)3 est comparable à celle des cristaux les plus efficaces tels que BaB2O4 et LiNbO3. Le comportement piézoélectrique du matériau massif n’étant pas référencé, sa structure cristalline laisse toutefois envisager des propriétés piézoélectriques intéressantes. Par ailleurs, la matrice polymère a été choisie pour sa simplicité d'utilisation et de production, son coût relativement faible, sa versatilité et sa facilité de mise en forme. Les nanocomposites peuvent être élaborés par deux voix différentes : la première consiste à disperser mécaniquement des nanocristaux fonctionnalisés dans un polymère ou dans un solvant de polymère approprié et la deuxième concerne la polymérisation in-situ de microémulsions composées du monomère liquide. Les synthèses en microémulsions inverses ont été privilégiées pour d’une part élaborer des nanocristaux d’iodate de fer de taille et de forme contrôlées puis, d’autre part, photo-polymériser des couches minces déposées à la tournette. Un aspect très original de ce travail consiste en l’utilisation de la Diffusion Hyper-Rayleigh pour étudier in-situ les cinétiques de cristallisation des particules d’iodate de fer en fonction des conditions expérimentales de synthèse à savoir, la température et la composition des microémulsions. Cette technique qui consiste à détecter les réponses optiques non-linéaires des suspensions de nanoparticules en microémulsions a été combinée avec d’autres méthodes expérimentales plus classiques comme la diffraction des rayons X, la diffusion dynamique de la lumière et la microscopie électronique en transmission. Cela a permis d’élucider les mécanismes de croissance des nanocristaux d’iodate de fer en microémulsions inverses. Par la suite, des couches minces nanocomposites ont été préparées après orientation sous champs électriques des nanocristaux polaires dispersés dans le MMA. Les caractérisations mécaniques, optiques non linaires et piézoélectriques de ces couches sont encourageantes. / The development of new sensors, transducers and integrated optoelectronic and piezoelectric devices requires the preparation of new materials that link mechanical, optical and electrical properties. In this perspective, it is expected that nanocomposite materials with inclusions of acentric inorganic nanocrystals in a polymer matrix will give rise to both piezoelectric and nonlinear optical (NLO) properties. Dispersion and orientation of nanocrystals in the polymer matrix are however crucial to obtain a collective response of individual nanocrystals and significant resultant properties. In this work, iron iodate (Fe(IO3)3) nanocrystals were used as nanofillers of a PMMA / PTMPTA polymer matrix. The nonlinear optical response of Fe(IO3)3 is comparable to the most effective NLO crystals such as LiNbO3 and BaB2O4. Good piezoelectric properties are also expected due to the material crystalline structure. Moreover, the polymer matrix was chosen for its ease of use and production, its relatively low cost, versatility and ease in shaping. Elaboration of nanocomposites is usually based on two different experimental procedures: mechanical dispersion of functionalized nanocrystals in a suitable polymer or polymer solvent is a first route whereas in-situ polymerization of reverse microemulsions for which a liquid monomer is the oil phase is the second one. Water-in-Oil (W/O) microemulsions were preferred in order to control the size and shape of as-obtained iron iodate nanocrystals and then to polymerize spin-coated thin films. A very original aspect of this work is the implementation of the Hyper-Rayleigh Scattering technique to probe in-situ the crystallization kinetics of iron iodate nanoparticles according to the experimental conditions (synthesis temperature and microemulsions composition). Detection of the second-harmonic scattered light combined with more conventional experimental techniques such as X-ray diffraction, dynamic light scattering and Transmission Electron Microscopy allowed us to understand the growth mechanisms of iron iodate naocrystals in W/O microemulsions. Nanocomposite thin films were then spin-coated after electric fields orientation of dispersed polar nanocrystals in MMA.

Investigamos as propriedades quânticas conjuntas dos três feixes intensos de luz produzidos por um oscilador paramétrico ótico (OPO) operando acima do limiar, denominados bombeio, sinal e complementar. Analisamos experimentalmente as flutuações quânticas de intensidade e fase destes feixes, e como se correlacionam. Observamos pela primeira vez a presença de correlações quânticas entre as fases dos três campos. O ruído observado na soma das fases de sinal e complementar, Vq12=1,28(3)>1, passa a apresentar compressão de ruído após ser corrigido pelas flutuações de fase do feixe de bombeio, resultando em (Vq12)\' =0,84(3)<1. Para potências mais altas de bombeio, observamos também a existência de correlações quânticas diretamente entre as amplitudes do feixe de bombeio e um dos feixes convertidos (sinal ou complementar); a máxima compressão de ruído medida correspondeu a Vp02=0,86(3)<1. Estendemos nosso estudo às propriedades de emaranhamento deste sistema tripartite, para tanto utilizando dois critérios distintos. Nossos dados apontam a separabilidade do sistema no regime de operação estudado, em contradição com o modelo teórico. Utilizando o critério de emaranhamento de P. van Loock e A. Furusawa, obtivemos os seguintes valores para as combinação de variâncias que comprovariam a inseparabilidade caso fossem menores que 2: V0=1,29(5)<2, V1=2,04(11)>2 e V2=2,09(7)>2. Com relação ao segundo critério de separabilidade, positividade sob transposição parcial, obtivemos os seguintes autovalores simpléticos a partir da matriz de covariância medida: A0=0,94(8) e A1=0,36(6)<1, em que o emaranhamento seria evidenciado caso A0<1 e A1<1. Esta discordância com a previsão teórica está relacionada a um ruído clássico espúrio observado no sistema, cujas características são levantadas nesta tese. Nossa análise indica os rumos a serem seguidos para a observação do emaranhamento. Mostramos teoricamente que o emaranhamento tripartite previsto pode ser utilizado como recurso para a criação de um sistema emaranhado multipartite. Para tanto, diversos OPOs são utilizados em uma configuração em cadeia, na qual o feixe de bombeio refletido pelo primeiro OPO serve de bombeio para o segundo e assim sucessivamente. Este esquema permite a geração de uma rede quântica multicolor escalável. Por fim, descrevemos a construção de um laser de Ti:safira que representa o primeiro passo na integração entre luz não-clássica e física atômica a ser investigada em nosso laboratório. Este laser pode ser utilizado, ao mesmo tempo, como bombeio do OPO e de uma nuvem de átomos. O emaranhamento tripartite gerado no OPO estabeleceria a conexão destes últimos com os feixes convertidos, cujos comprimentos de onda possibilitariam a transmissão direta destes feixes de luz através de fibras óticas comerciais de telecomunicação. / We have investigated the collective quantum properties of the three bright light beams produced by an optical parametric oscillator (OPO) operating above threshold, named pump, signal, and idler. We have analyzed experimentally their intensity and phase quantum fluctuations, and how they are correlated. For the first time, we have observed the existence of phase quantum correlations among the three beams. The measured phase-sum noise between signal and idler, Vq12=1,28(3)>1, presents squeezing when corrected by the phase fluctuations of the pump beam, resulting in (Vq12)\'=0,84(3)<1. For higher pump powers, we have observed the existence of amplitude quantum correlations directly between pump and one of the downconverted beams (signal or idler); the maximum measured squeezing level corresponded to the noise Vp02=0,86(3)<1. Our investigations included the entanglement properties of this tripartite system, tested by two different criteria. Our data points to the separability of the system in the accessible regime of operation, in contradiction with the theoretical predictions. Applying the criterion by P. van Loock and A. Furusawa, we have obtained the following values of combinations of variances which would attest the inseparability in case values smaller than 2 would be obtained: V0=1,29(5)<2, V1=2,04(11)>2, and V2=2,09(7)>2. For the second criterion, the positivity under partial transpose, we have obtained the following symplectic eigenvalues calculated from the measured covariance matrix: A0=0,94(8) and A1=0,36(6)<1, where entanglement is attested in case A0<1,and A1<1. This discrepancy with the theoretical prediction is caused by a classical spurious noise observed in the system, which characteristics are investigated in this thesis. Our analysis indicates the path to successfully observe tripartite entanglement. We show theoretically that the predicted tripartite entanglement can be employed as a resource for the construction of a multipartite entangled system. This is accomplished by pumping several OPO\'s with the same optical field, such that the pump beam reflected by the first OPO is utilized to pump a second one, and so on. This scheme allows the generation of a multicolor scalable quantum network. Finally, we describe the construction of a Ti:sapphire laser which represents the first step in the integration between non-classical light and atomic physics to be investigated in our laboratory. This laser could be employed at the same time to pump an OPO and to interact with a cloud of atoms. The tripartite entanglement produced by the OPO could then entangle the atoms to the downconverted beams, which wavelength would allow the transmission of these beams through commercial optical fibers for telecom.

Neste trabalho estudamos teórica e experimentalmente o efeito de Conjugação de Fase por Mistura Degenerada de Quatro Ondas (CFMD40) e Modulação Transversal de Fase em cristais dopados com Cr+3. Estudamos a CFMD40 em Al2O3:Cr+3 (rubi) e GdAlO3:Cr+3 com um laser de Ar (em &#955;=514nm) obtendo um bom acordo entre os resultados experimentais e os teóricos (nestes cálculos usamos os valores de n2 de um trabalho anterior [1]). O modelo teórico que fizemos explica muito bem o comportamento de saturação da eficiência da CFMD40 que não era compreendido em trabalhos anteriores [47,48.2]. Usando os mesmos valores de n2 obtivemos um bom acordo entre os resultados experimentais e teóricos para o efeito de Modulação Transversal de Fase. Também fizemos um modelo teórico para o efeito de Modulação Transversal de Fase em CFMD40 que explica nossas observações [2]. A não linearidade destes materiais foi investigada usando-se três técnicas experimentais diferentes [1.2] e por dois outros grupos [61.62] (para o rubi) através de mistura de duas ondas não degeneradas. Todas estas medidas estão em bom acordo. Na alexandrita (BeAl2O 4:Cr+3) estudamos o espectro de &#967;(3) (ou n2) em ressonância das linhas R. Nos atribuímos a forma assimétrica do espectro como sendo oriunda de duas contribuições para susceptibilidade, onde um termo é devido a interação ressonante com o sistema de dois níveis e o outro devido a mudança de polarizabilidade causada pela população do estado excitado (esta é a primeira vez que este efeito foi observado). / In this work we studied theoretical and experimentally the effects of Phase Conjugation by Degenerate Four Wave Mixing and Transversal Phase (PCD4WM) Modulation in Cr+3 doped crystals. We studied the PDC4WM in Al2O3:Cr+3 (ruby) and GdAlO3:Cr+3 with on Ar laser (at &#955;= 514 nm) and obtained a good agreement between our experimental and theoretical results (in these ca1culations we used the nonlinear refractive index n 2 values from a previous paper [1]. The theoretical model that we developed explains very well the saturation behaviour of the PDC4WM efficiency that was not understood in previous papers [47.48,2]. These values of n2 are also in good agreement with our results in Transverse Phase Modulation. We also developed a theoretical model for the effect of Transverse Phase Modulation in PCDFWM that explains our observations [2]. The nonlinearity ?n IND.2? from these materials was investigated by us using three different techniques [1.2], by other two groups [61.62] (for the ruby) in nondegenerate two-wave mixing and all those measurements are in good agreement. In alexandrite (BeAl2O4:Cr +3) we studied the &#967;(3) (or n2) spectrum in resonance with the R lines. We attributed the asymetric shape of the spectrum by the effect of two differents contributions, one term due to the resonant interaction of the two-level system and the other due to the polarizability change caused by excited state population (this is the first observation of this kind of effect.

Esta tese descreve a demonstração experimental de dispositivos baseados em fibras de cristal fotônico (PCFs), que aproveitam a flexibilidade estrutural oferecida pela matriz de capilares que compõe a seção reta da fibra, de forma a preencher estes capilares com líquidos e materiais nanoestruturados. Para o caso de materiais nanoestruturados, uma vez preenchida a fibra, os materiais nela inseridos interagem eficientemente com a luz guiada. Essa arquitetura diferenciada em relação às fibras ópticas convencionais abre novas perspectivas no desenvolvimento de aplicações como óptica não-linear e sensoriamento. PCFs de núcleo líquido, por outro lado, impõe dificuldades para a implementação de dispositivos práticos, devido às altas taxas de evaporação dos líquidos inseridos. Por esta razão, foi desenvolvida uma nova técnica para vedar seletivamente ambas as faces externas do núcleo líquido de uma PCF, utilizando um polímero curável. Estes tampões poliméricos evitam a evaporação, causando um impacto mínimo no guiamento da luz, tornando o dispositivo usável por semanas. Esta nova técnica de vedação foi empregada em um experimento para a geração de supercontínuo em uma PCF com núcleo de água destilada, proporcionando uma estabilidade de pelo menos 1 hora. Combinando líquidos e materiais nanoestruturados, foi também foi desenvolvido um sensor de temperatura baseado no preenchimento do núcleo de uma PCF por uma amostra coloidal de nanopartículas semicondutoras de CdSe/ZnS, dispersas em óleo mineral. O espectro de luminescência destes pontos quânticos coloidais é fortemente dependente da temperatura e os resultados obtidos mostraram que a grande interação entre a luz e o colóide, aliada a geometria da fibra, proporcionando uma sensibilidade ~5,5 vezes maior que a apresentada por uma rede de Bragg escrita em uma fibra óptica padrão, com boa relação sinal-ruído. / This thesis describes the experimental demonstration of devices based on photonic crystal fibers (PCFs). PCFs are optical fibers whose core is surrounded by a regular matrix of holes, which runs longitudinally across its length. This singular configuration allows the insertion of liquids and nanostructured material into the fiber. Nanostructured materials embedded inside the fiber efficiently interact with the guided light, opening up possibilities of novel applications regarding the fields of non-linear optics, as well as optical sensing. On the other hand, liquid-core PCFs suffer from some disadvantages concerning practical device applications, on account of the high evaporation of the inserted liquids. In order to address this issue, we developed a novel technique to selectively seal the external faces of a liquid-core PCF, by using a polymer plug. These polymer plugs avoid evaporation while causing a minimum impact on the light guiding characteristics of the PCF. This novel sealing technique was employed in a supercontinuum generation experiment, by using a PCF whose core was water-filled. A temporal stability of at least one-hour on the resulting spectrum was achieved. Combining the above techniques, we also developed a temperature sensor based on the core-filling of a PCF by a colloidal ensemble of CdSe/ZnS semiconductor nanoparticles dispersed in mineral oil. Those colloidal quantum-dots display a luminescence spectrum which is strongly dependent on temperature and the experimental results indicated that the greater interaction between the guided light and the colloidal sample, provided by the fiber geometry, allowed a sensitivity which is approximately 5.5 times than possible with a conventional Bragg grating, while keeping a satisfactory signal-to-noise ratio.

Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-03-27T20:46:23Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação.pdf: 3142879 bytes, checksum: 86acc16510c6eb3acd7d645922238d47 (MD5) / Made available in DSpace on 2017-03-27T20:46:23Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação.pdf: 3142879 bytes, checksum: 86acc16510c6eb3acd7d645922238d47 (MD5) / Trabalhos anteriores já mostraram o dobramento do momento angular orbital de feixes após a geração de segundo harmônico em meios não lineares. Nesse trabalho pretendemos usar a polarização como parâmetro auxiliar para poder incidir em um cristal não linear dois feixes colineares com momentos angulares orbitais diferentes e obter na geração de seu segundo harmônico a soma de seus momentos angulares orbitais e veri car este resultado experimentalmente. / Previous work have already shown the orbital angular momentum doubling after second harmonic generation in non-linear media. In this work we intend to use the polarization as an auxiliary parameter to focus in a non-linear crystal two colinear beams with different orbital angular momentum and obtain in its second harmonic generation the sum of their orbital angular momentum and to verify it exeperimentally.

Le sujet de cette thèse porte sur les phénomènes d’auto-organisations d’ondes optiques non-linéaires. Ce travail principalement théorique et numérique repose sur différents formalismes de turbulenced’ondes, les singularités Hamiltoniennes et diverses expériences.Une première partie de la thèse porte sur les processus irréversibles de thermalisation et de conden-sation d’ondes. Le phénomène de condensation se caractérise par la formation d’une structure cohérenteà grande échelle (condensat) qui reste immergée dans une mer de fluctuations aux petites échelles (parti-cules non condensées). En dépit des longueurs de propagation rédhibitoires pour atteindre l’état d’équilibrecondensé, nous avons mis en évidence expérimentalement et théoriquement un phénomène de pré-condensation qui a lieu loin de l’équilibre etqui joue un rôle précurseur pour l’état d’équilibre asymptotique. Par ailleurs, sur la base d’observations ex-périmentales récentes du phénomène de nettoyage de faisceau dans une fibre optique multimode, nousavons développé une approche cinétique de turbulence d’ondes prenant en compte le désordre structu-rel du matériau. La théorie révèle que le désordre entraîne une accélération significative du processus decondensation permettant d’expliquer l’effet de nettoyage de faisceau. Les expériences effectuées reportentl’observation d’une transition de la distribution thermique vers la condensation, avec une fraction macro-scopique de puissance condensée dans le mode fondamental. Nous avons aussi étudié l’impact d’une ré-ponse fortement non-locale (ou non-instantanée) sur la propagation d’un speckle, ce qui a permis d’iden-tifier un mécanisme d’émergence spontanée de cohérence de phase à longue portée.Une seconde partie des travaux est centrée sur le phénomène d’attraction de polarisation lors de l’in-jection d’ondes incohérentes aux deux extrémités d’une fibre optique. La dynamique spatio-temporelle desondes partiellement polarisées contra-propagatives relaxe vers un état stationnaire où se produit un phé-nomène d’auto-polarisation survenant au point milieu de la fibre. Ce phénomène est lié à la présence desingularités dans le système Hamiltonien associé à l’état stationnaire. / The subject of this thesis concerns the study of phenomena of self-organization of incoherentoptical waves. This work is essentially theoretical and numerical and relies on different formalisms of waveturbulence theory, the Hamiltonian singularities, and different experiments.The first part of the thesis deals with the irreversible processes of thermalization and condensation ofincoherent waves. The phenomenon of condensation is characterized by the formation of a large scale co-herent structure (condensate) that remains immersed in a sea of small scale fluctuations (uncondensedparticules). In spite of the large propagation lengths required to reach the condensed equilibrium state, wehave identified theoretically and experimentally in atomic vapors a phenomenon of pre-condensation thatoccurs far from thermal equilibrium and that plays the role of a precursor for the asymptotic equilibriumstate. On the other hand, on the basis of recent experimental observations of the effect of beam self-cleaningin multimode optical fibers, we have developed a kinetic wave turbulence approach that accounts for theimpact of a structural disorder of the material. The theory reveals that disorder leads to a significant ac-celeration of the condensation process, which can explain the beam self-cleaning effect. Our experimentsreport the observation of the transition from the thermal distribution toward condensation with a macro-scopic fraction of condensed power into the fundamental mode. We have studied the impact of a highlynonlocal (or non-instantaneous) response on the nonlinear propagation of a speckle beam, which allowedus to identify a mechanism of spontaneous emergence of long-range phase coherence.The second part of the manuscript is based on a phenomenon of polarization attraction when two in-coherent waves are injected at both ends of an optical fiber. The spatio-temporal dynamics of the counter-propagating partially polarized waves relax toward a quasi-stationary state characterized by a phenomenonof self-polarization that occurs just in the middle point of the optical fiber. This effect is related to the pre-sence of singularities in the Hamiltonian system associated to the stationary state.