Orientador: Flávio Caldas da Cruz / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-21T00:14:04Z (GMT). No. of bitstreams: 1 Nery_MarinaTrad_M.pdf: 8701569 bytes, checksum: 94cd9456a3956cb1553345343461b95e (MD5) Previous issue date: 2012 / Resumo: Esta tese reporta o projeto e a construção de um oscilador paramétrico óptico continuo de frequência unica e sintonizável em torno de 846 nm. 0 cristal responsável pela conversão de frequências e o MgO:PPSLT (Tantalato de Lftio periodicamente polado e dopado com 1% de Oxido de Magnésia), e este e bombeado por ate 6 W de um laser continuo emitindo em 532 nm. Um dos objetivos do experimento e a geração de segundo harmônica, a partir de luz infravermelha, resultando em radiação na região espectral do azul, mais ,precisamente em 423 nm, necessária para experimentos de aprisionamento e resfriamento de átomos neutros de Cálcio. Para isso foi montada uma cavidade em anel unicamente ressonante para o feixe sinal e foi observada oscilação do dispositivo em uma potencia limiar próxima de 5 W, mais alta do que o calculada previamente. Foi possível observar a emissão de 30 m W de radiação do feixe sinal o que representa uma potencia de 30 W dentro da cavidade, ja que o espelho de saída era 99,9% refletor. Também foi possível observar luz azul devido a geração de segundo harmônica (sem Casamento de fase) dentro do cristal PPSLT. Ao longo deste trabalho são apresentados cálculos detalhados da cavidade óptica, das curvas de sintonia do cristal por temperatura e periodicidade da grade e do ganho paramétrico óptico. Acreditamos que o alto limiar de oscilação do dispositivo esteja relacionado a perdas devidas ao efeito fotorrefrativo no cristal, produzido pelo laser de bombeio, já que as perdas da cavidade devido aos espelhos e ao cristal eram baixas. Esta hipótese deve ser melhor investigada em futuras implementação de OPOs bombeados por altas potencias na região espectral do visível / Abstract: This thesis reports the design and construction of an continuously tunable and single frequency optical parametric oscillator around 846 nm. The crystal responsible for the frequency conversion is MgO: PPSLT (periodically poled lithium tantalate doped 1% of magnesium oxide), pumped with up to 6 W by a continuous-wave laser emitting at 532 nm. One goal of the experiment is the second harmonic generation from infrared light, resulting in radiation in the blue spectral region, more precisely 423 nm, necessary for experiments of cooling and trapping of neutral calcium atoms. A ring cavity resonant only for the signal beam was mounted and oscillation has been observed with a threshold of 5 W, higher than previously calculated. It was observed 30 mW ofradiation from the signal representing an intracavity power of 30 W, given the output coupler reflectivity of 99.9% reflector. We also observed blue light due to second harmonic generation (without phase matching) within the crystal PPSLT. Throughout this work we present detailed calculations of the optical cavity, temperature tuning curves for the crystal period of the poling grate and the optical parametric gain. We believe that the observed high threshold is related to losses due to the photorefractive effect in the crystal produced by the pump laser, since other losses due to the cavity mirrors and the crystal were very low. This hypothesis should be further investigated in future implementations of OPOs pumped by high powers in the visible spectral region / Mestrado / Física / Mestra em Física

Orientador: Elnatan Chagas Ferreira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T00:34:06Z (GMT). No. of bitstreams: 1 Rossetto_JonatasFred._D.pdf: 4844072 bytes, checksum: 0f28d51130deaa192c51125f71eedf7b (MD5) Previous issue date: 2004 / Resumo: Sensores distribuídos a fibra óptica representam uma tecnologia chave para o desenvolvimento de estruturas inteligentes, uma vez que podem ser totalmente integrados aos materiais da estrutura. Efeitos ópticos não lineares podem ser utilizados para implementar esta nova classe de sensores, sem a necessidade da construção de componentes sensores individuais. Esta tese propõe a utilização do espalhamento Brillouin estimulado e do espalhamento Raman espontâneo, para desenvolver um sensor distribuído capaz de determinar o perfil de temperatura e deformação mecânica ao longo da fibra óptica sensora. Diversos resultados experimentais são apresentados para ambos os efeitos não-lineares ocorrendo em uma fibra óptica monomodo. Uma nova técnica para estabilizar a diferença de freqüência entre dois campos ópticos é proposta. Uma técnica de processamento de sinal é proposta para melhorar a resolução espacial de um sensor distribuído Brillouin. Uma topologia de ponta única é proposta para a implementação de um sensor distribuído Brillouin. Diversos aspectos sobre a implementação de um sensor distribuído Raman são discutidos. Uma nova topologia é proposta para o desenvolvimento de um sensor distribuído híbrido utilizando três diferentes tecnologias: Raman/Brillouin/FBGs, compartilhando a mesma fibra óptica sensora. Os resultados apresentados consolidam a pesquisa e indicam que o investimento em tecnologias correlatas é promissor tanto academicamente quanto comercialmente / Abstract: Fiber optic distributed sensors are a key technology for the development of smart structures, as it can be fully integrated to the structure materials. Nonlinear optical effects can be used to implement such kind of sensors, without the need of building individual sensor components. This thesis proposes the use of the stimulated Brillouin scattering and the spontaneous Raman scattering to develop an optical fiber distributed sensor capable of measuring both the temperature and the strain profile along a sensing optical fiber. Several experimental results are presented concerning both nonlinear effects occurring in a single-mode optical fiber. A new technique to stabilize the optical frequency difference between two optical fields is proposed. A signal processing technique is proposed to improve the spatial resolution of the Brillouin distributed sensor. An one-end topology is proposed to implement a Brillouin distributed sensor. Several aspects about the implementation of a Raman distributed sensor are discussed. A new topology is proposed for the development of a hybrid optical fiber distributed sensor using three different technologies, Raman/Brillouin/FBG, sharing the same sensing optical fiber. The presented results consolidate the research and indicate that the investment in correlated technologies is promising not only for the academic research but also for commercial applications / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica

Les propriétés optiques linéaires et non-linéaires de nanoparticules métalliques de tailles non-négligeables comparées à celles des longueurs d’onde excitatrices sont étudiées dans cette thèse. Les informations issues de la symétrie sont mises en avant afin de décrire des nanoparticules appartenant à des groupes ponctuels. Pour cela, un formalisme totalement irréductible est mis en place afin de prendre en compte l’extension spatiale des objets étudiés. Dans ce formalisme, le tenseur de réponse non-linéaire possède un nombre fini de valeurs significatives reliant les composantes multipolaires des champs incidents et sortants. Ce formalisme est alors appliqué analytiquement à l’étude de la réponse non- linéaire du second ordre de nano-étoiles d’or en interprétant des mesures de SHG résolue en polarisation. Finalement, des expériences de spectroscopies multidimensionnelles sont utilisées dans le but de connecter les propriétés spatiales et les propriétés spectrales de ces objets. L’introduction de modes propres définis par la symétrie des objets permet encore une fois de donner un sens physique aux comportements électroniques mis en jeu / Using metallic nanoparticles with a threefold symmetry thorough the study, the impact of the symmetry on the nonlinear properties is investigated. Interpretations of polarization-resolved SHG experiments indicate the importance of multipolar resonances, in particular quadrupole and octupole, to explain the strong values of the nonlinear susceptibilities in such systems. A fully irreducible formalism is then developed to treat extended objects like nanoparticles. In this formalism, the nonlinear response tensor is a discrete set of values easily constrained by symmetries instead of a field. This formalism permits to describe simply linear and nonlinear optical response from nanoparticles. Finally, time-domain experiments are conducted with the aim to connect spatial and spectral properties. These experiments allow to interpret the spectra in terms of eigenmodes

Ce mémoire présente des techniques tout-optiques visant à préserver les paramètres physiques d’un signal télécom au cours de sa propagation dans une fibre optique de plusieurs kilomètres, tels que son état de polarisation, son profil d’intensité et son spectre. Il se compose en deux majeures parties.La première présente tout d’abord l’attraction de polarisation, ayant lieu au cours de l’interaction entre deux faisceaux contrapropagatifs, et qui permet d’imposer un état fixe de polarisation au signal à la sortie de la fibre indépendamment de son état initial. Des applications tout-optiques basées sur l’Omnipolariseur, un dispositif mis au point à Dijon et permettant le contrôle de ce phénomène non linéaire, sont ensuite développées. Elles fonctionnalisent l’état de polarisation d’un signal OOK-RZ à 10 Gbit/s pour mettre au point une mémoire optique à bascule, un routeur, un brouilleur chaotique, et une technique de copie/dissimulation de paquets de données dans une fibre spun de 5 km.La deuxième réalise la première démonstration expérimentale des parois de domaines de polarisation qui annulent les effets dégradant les profils d’intensité et spectral d’un signal codé au cours de sa propagation. Ce phénomène provient du couplage non-linéaire entre les deux modes de polarisation orthogonaux d’une lumière qui se propage dans un milieu Kerr en régime normal de dispersion, et provoque une modulation en opposition de phase des deux modes le long de la fibre. Il est possible de verrouiller deux trains d’impulsions optiques d’intensité complémentaire de sorte à ce que les impulsions ne subissent plus les effets de distorsion intervenant au sein de la fibre afin de conserver l’information à transmettre. Ainsi une propagation sans distorsion a pu être réalisée sur 50 km. / The second performs the first experimental demonstration of the polarization domain walls which cancel the effects which degrade the intensity and spectral profile of a telecom signal during propagation. This phenomenon comes from non-linear coupling between the two orthogonal polarization modes of light propagating in a Kerr medium in normal dispersion regime, and causes a modulation in phase opposition of the two modes along the fiber. It is possible to lock two optical pulse trains complementary intensity so that the pulses do not suffer the effects of distortion occurring in the fiber in order to maintain the information to be transmitted. And a distortion-free propagation was achieved on 50 km.

The Terahertz (1012 Hz) region of the electromagnetic spectrum covers the frequency range from roughly 300 GHz to 10 THz, which is in between the microwave and infrared regimes. The increasing interest in the development of ultra-compact, tunable room temperature Terahertz (THz) emitters with wide-range tunability has stimulated in-depth studies of different mechanisms of THz generation in the past decade due to its various potential applications such as biomedical diagnosis, security screening, chemical identification, life sciences and very high speed wireless communication. Despite the tremendous research and development efforts, all the available state-of-the-art THz emitters suffer from either being large, complex and costly, or operating at low temperatures, lacking tunability, having a very short spectral range and a low output power. Hence, the major objective of this research was to develop simple, inexpensive, compact, room temperature THz sources with wide-range tunability. We investigated THz radiation in a hybrid optical and THz micro-ring resonators system. For the first time, we were able to satisfy the DFG phase matching condition for the above-mentioned THz range in one single device geometry by employing a modal phase matching technique and using two separately designed resonators capable of oscillating at input optical waves and generated THz waves. In chapter 6, we proposed a novel plasmonic antenna geometry – the dimer rod-tapered antenna (DRTA), where we created a hot-spot in the nanogap between the dimer arms with a very large intensity enhancement of 4.1×105 at optical resonant wavelength. Then, we investigated DFG operation in the antenna geometry by incorporating a nonlinear nanodot in the hot-spot of the antenna and achieved continuously tunable enhanced THz radiation across 0.5-10 THz range. In chapter 8, we designed a multi-metallic resonators providing an ultrasharp toroidal response at THz frequency, then fabricated and experimentally demonstrated an efficient polarization dependent plasmonic toroid switch operating at THz frequency. In summary, we have successfully designed, analytically and numerically investigated novel THz emitters with the advantages of wide range tunability, compactness, room temperature operation, fast modulation and the possibility for monolithic integration, which are the most sought after properties in the new generation THz sources.

In 1920, Leon Brillouin discovered a new kind of light scattering – Brillouin scattering – which occurs as a result of the interaction of light with a transparent material’s temporal periodic variations in density and refractive index. Many advances have since been made in the study of Brillouin scattering, in particular in the field of fiber optics. An in-depth investigation of Brillouin scattering in optical fibers has been carried out in this thesis, and the theory of stimulated Brillouin scattering (SBS) and combined Brillouin gain and loss has been extended. Additionally, several important applications of SBS have been found and applied to current technologies. Several mathematical models of the pump-probe interaction undergoing SBS in the steady-state regime have emerged in recent years. Attempts have been made to find analytical solutions of this system of equations, however, previously obtained solutions are numerical with analytical portions and, therefore, qualify as hybrid solutions. Though the analytical portions provide useful information about intensity distributions along the fiber, they fall short of describing the spectral characteristics of the Brillouin amplification and the lack of analytical expressions for Brillouin spectra substantially limits the utility of the hybrid solutions for applications in spectral measurement techniques. In this thesis, a highly accurate, fully analytic solution for the pump wave and the Stokes wave in Brillouin amplification in optical fibers is given. It is experimentally confirmed that the reported analytic solution can account for spectral distortion and pump depletion in the parameter space that is relevant to Brillouin fiber sensor applications. The analytic solution provides a valid characterization of Brillouin amplification in both the low and high nonlinearity regime, for short fiber lengths. Additionally, a 3D parametric model of Brillouin amplification is proposed, which reflects the effects of input pump and Stokes powers on the level of pump wave depletion in the fiber, and acts as a classification tool to describe the level of similarity between various Brillouin amplification processes in optical fibers. At present, there exists a multitude of electro-optic modulators (EOM), which are used to modulate the amplitude, frequency, phase and polarization of a beam of light. Among these modulators, phase modulation provides the highest quality of transmitted signal. As such, an improved method of phase-modulation, based on the principles of stimulated Brillouin scattering, as well as an optical phase-modulator and optical phase network employing the same, has been developed. Due to its robustness, low threshold power, narrow spectrum and simplicity of operation, stimulated Brillouin scattering (SBS) has become a favourable underlying mechanism in fiber-based devices used for both sensing and telecommunication applications. Since birefringence is a detrimental effect for both, it is important to devise a comprehensive characterization of the SBS process in the presence of birefringence in an optical fiber. In this thesis, the most general model of elliptical birefringence in an optical fiber has been developed for a steady-state and transient stimulated Brillouin scattering (SBS) interaction, as well as the combined Brillouin gain and loss regime. The impact of the elliptical birefringence is to induce a Brillouin frequency shift and distort the Brillouin spectrum – which varies with different light polarizations and pulse widths. The model investigates the effects of birefringence and the corresponding evolution of spectral distortion effects along the fiber, and proposes regimes that are more favourable for sensing applications related to SBS – providing a valuable prediction tool for distributed sensing applications. In recent years, photonic computing has received considerable attention due to its numerous applications, such as high-speed optical signal processing, which would yield much faster computing times and higher bandwidths. For this reason, optical logic has been the focus of many research efforts and several schemes to improve conventional logic gates have been proposed. In view of this, a combined Brillouin gain and loss process has been proposed in a polarization maintaining optical fiber to realize all-Optical NAND/NOT/AND/OR logic gates in the frequency domain. A model describing the interaction of a Stokes, anti-Stokes and a pump wave, and two acoustic waves inside a fiber, ranging in length from 350m-2300m, was used to theoretically model the gates. Through the optimization of the pump depletion and gain saturation in the combined gain and loss process, switching contrasts of 20-83% have been simulated for different configurations.

Le présent travail visait à développer et à étudier une nouvelle méthode de fabrication des guides d'onde, « High Index Soft Proton Exchange » (HISoPE) , qui permet de réaliser des guides d'onde très confinés (dne = 0,1). Des caractérisations en génération d’harmonique localisée ont montré que les propriétés non linéaires de ces guides ne sont pas détruites mais les guides HISoPE réalisés sur coupe Z peuvent présenter des modes ayant des pertes élevées. Ces pertes peuvent être éliminés en utilisant des bains plus acides pour l’échange, mais cela implique des déformations plus importante dans les guides d'onde canal et la nature hybride des modes propageant. Dans le cadre du projet PhoXcry, nous avons essayé de réaliser un modulateur électro-optique très efficace en combinant des cristaux photoniques et des guides HISoPE sur coupe X. Dans les meilleurs guides d'onde fabriqués sur coupe X, les pertes à la propagation, expliquées par la nature hybride des modes sont de 1.75dB/cm, mais dans les guides d'ondes nanostructurés il n’a pas été possible d’identifier clairement une bande interdite photonique. HISoPE en combinaison avec l’échange inverse (Reverse Proton Exchange, RPE) a montré un grand potentiel pour la fabrication de guides d'onde enterrés. Dans une expérience de SHG et malgré des pertes élevées de 2dB/cm, nous avons pu estimer une efficacité de conversion de 160%/W*cm2. Un comportement du coupleur directionnel a été observé dans les guides d'onde enterrés fabriqué en raison d’une cinétique RPE différente dans les différentes parties du guide d'onde. Un développement ultérieur de la méthode HISoPE + RPE devrait permettre d'améliorer la qualité des guides enterrés. / The present work aimed to develop and to study a new method of waveguide fabrication, High Index Soft Proton Exchange (HISoPE), which allows realizing highly confining waveguides in LiNbO3 (dne=0.1). Characterizations by localized SHG experiments, showed that the nonlinear properties of the HISoPE waveguides are not destroyed, but modes with high propagation loss were observed for planar HISoPE waveguides on Z-cut wafers. These losses can be eliminated by performing the exchange in more acidic bath, but this results in more important deformations in channel waveguides and in the hybrid nature of the propagating modes. In the frame of the project PhoXcry, we tried to realize a highly efficient electro-optical modulator by combining photonic crystals and HISoPE waveguides on X-cut wafers of LiNbO3. The losses of the waveguides fabricated on X-cut, attributed to the hybrid nature of the propagating modes, were estimated to be around 1.75dB/cm. The nanostructured waveguides exhibited high losses and it was not possible to identify clear optical band gap. HISoPE in combination with reverse proton exchange (RPE) showed a great potential for buried waveguide fabrication. We used them in a SHG experiment and despite elevated losses of 2dB/cm, the conversion efficiency was estimated as high as 160%/W*cm2. A directional coupler behavior was observed in the buried waveguides due to different RPE kinetics in different parts of the waveguide. A further development of the HISoPE+RPE process will improve the quality of the buried waveguides.

Le développement des nouvelles technologies, de l'informatique et d'internet ces dernières décennies s'est accompagné d'une demande croissante de supports de stockage de l'information. En particulier, le stockage optique de données. Les supports conventionnels (Cd-Rom, Blue-ray…), basés sur un stockage en surface du disque, ont atteint aujourd'hui leurs limites. Une nouvelle technologie en cours de développement, basée sur un stockage de données en trois dimensions, est une alternative prometteuse pour supplanter les supports conventionnels. Les matériaux doivent intégrer des entités aux propriétés photochromes (commutateur moléculaire) et d'absorption multi-photonique démontrées. Au cours de cette thèse, nous avons envisagé la synthèse de molécules fonctionnelles qui présenteraient ces deux caractéristiques. Dans un premier temps, nous nous sommes intéressés à la synthèse et à l'étude comparative de complexes homo et hétéroleptiques de ruthénium présentant une certaine potentialité pour l'absorption à deux photons. Nous avons montré que ces systèmes étaient très actifs et qu'ils permettaient d'accueillir une entité photochrome sans perte des propriétés bi-photoniques. Nous avons par la suite étudié les propriétés en photochromisme de complexes de ruthénium tris-bipyridine originaux comprenant un motif azobenzène. La complexation au métal bouleverse profondément le photochromisme de l'azobenzène avec des caractéristiques cinétiques notablement différentes de celles des ligands. Enfin, nous avons étudié les propriétés de complexes hybrides composés de ligands pour l'absorption à deux photons et d'autres pour le photochromisme, ces composés sont actifs dans ces deux domaines. Nous discutons finalement du potentiel du comportement optique de films composés de ces complexes. Nous avons procédé à des essais préliminaires de modulation du signal SHG sur ces films. Nous souhaitons optimiser toutes les composantes du processus afin de déterminer le potentiel de ces composés en stockage optique de données. / The development of new technologies , computer and internet in recent decades has been accompanied by an increasing demand for media storage information. In particular , the optical data storage .Conventional media ( CD-ROM , Blu-ray ... ) based on a storage disk surface, have now reached their limits. A new technology being developed , based on a data storage in three dimensions, is a promising alternative to replace conventional materials. Materials must include entities for photochromic properties (molecular switch) and multi- photon absorption demonstrated. In this thesis , we considered the synthesis of functional molecules which present these two characteristics. As a first step , we are interested in the synthesis and comparative study of homo and heteroleptic ruthenium complex having a certain potential for two-photon absorption . We have shown that these systems were very active and they allowed to host a photochromic entity lossless bi- photonic properties. We then studied the properties of originals photochromic ruthenium tris- bipyridine containing an azobenzene motif. The metal complexing profoundly changes the photochromism of azobenzene with significantly different from those ligands kinetics . Finally, we studied the properties of hybrid complexes of ligands for the two-photon absorption and others to photochromism , these compounds are active in both areas. We finally discuss the potential of the optical behavior of compounds of these complex films. We conducted preliminary tests of the SHG signal modulation on these films. We want to maximize all components of the process to determine the potential of these compounds in optical data storage .

Nous avons développé une nouvelle méthode de microscopie par effet électro-optique linéaire (effet Pockels), dite PLEOM, permettant de cartographier la susceptibilité du deuxième ordre Chi(2) d'un matériau non-centrosymétrique [1, 2]. Cette méthode est complémentaire de la microscopie de génération de seconde harmonique, et s’en distingue par différents aspects physiques et pratiques. Grâce à une détection interférométrique stabilisée, le retard de phase provoqué par une variation d'indice locale du matériau non-linéaire sous l'effet d'un champ électrique est détecté à 10-6 radians près, ouvrant la voie à l'imagerie d'échantillons biologiques ou au suivi du mouvement de nano-sondes [3]. PLEOM apporte un type de données nouveau, la "réponse en phase" du matériau, porteuse d'information physiques plus difficilement accessibles en microscopie biphotonique.Ce manuscrit décrit de nouveaux domaines de développement et d’application de PLEOM, qui a évolué vers une plateforme aux applications variées et multi-échelles, allant du nanométrique au millimétrique.Nous avons tout d’abord montré comment déterminer le vecteur de polarisation attaché à des nano-cristaux ferroélectriques uniques, en vue de leur utilisation comme nano-sondes. Cette nouvelle méthode permet, à notre connaissance de façon unique, de distinguer deux nano-cristaux mono-domaines d'orientations exactement opposées, dont les réponses en SHG ne peuvent pas être distinguées. Une image de phase électro-optique, combinée à un diagramme de polarisation, donne accès à l'orientation vectorielle d'un nano-cristal orienté aléatoirement dans le référentiel du laboratoire. Un verrou est ainsi levé pour des applications comme l'imagerie de nano-domaines ferroélectriques, celle de potentiels électrochimiques membranaires, où l'étude de la dynamique de rotation de molécules. Deux spécificités remarquables de PLEOM en font une méthode d'avenir : la faible intensité de pompage qui assure une bien meilleure biocompatibilité ainsi que la simplicité de la source laser continue utilisée.Nous avons ainsi pu utiliser PLEOM pour caractériser les domaines ferroélectriques d'un cristal de KTiOPO4 périodiquement réorienté en vue d’un quasi-accord de phase, ainsi que ceux d'un cristal bidimensionnel quasi-périodique de LiNbO3. Un retournement clair de la phase de 180 degree est observé au travers des parois de domaines, dont les coefficients électro-optiques apparaissent opposés dans le référentiel du laboratoire. PLEOM se présente ainsi comme un outil de caractérisation non destructif des propriétés de ces cristaux artificiels dont les motifs et les défauts (tels qu'une orientation localement incomplète) ont été caractérisés spatialement, et permet de mesurer localement leurs propriétés non-linéaires, dont le caractère tensoriel permet d’aller au-delà des informations acquises en microscopie classique.En outre, nous avons fait la preuve de principe d'une nouvelle expérience biomimétique, visant à étudier les potentiels membranaires cellulaires, en utilisant PLEOM sur des membranes phospholipidiques créées sur puce micro-fluidique et dopées en colorants. / Complementing Second-Harmonic Generation (SHG) microscopy, a new home-made nonlinear microscope named Pockels Linear Electro-Optical Microscopy (PLEOM) based on the linear electrooptic (Pockels) effect, has been developed and used to map the second-order susceptibility Chi(2) of non-centrosymmetric materials with high sensitivity due to a stabilized interferometric homodyne detection scheme [1, 2]. This enables PLEOM to detect the electrooptic phase retardation of light resulting from the variation of the refractive index of nonlinear materials down to 10-6 radian and to investigate nonlinear materials at the nano-scale [3] towards applications in imaging of biological samples and tracking of labels therein. With PLEOM, a new imaging method allows to access, besides the aplitude, the no less crucial phase response, which is not readily amenable to classical SHG microscopy. In the frame of this dissertation, we have further extended the range of applications of PLEOM to investigate nonlinear materials and structures from nano- to millimeter-scale.Firstly, we have proposed and demonstrated a new approach towards the full vector determination of the spontaneous polarization of single ferroelectric nano-crystals used as SHG nano-probes. This method allows to remove the ambiguity inherent to earlier polarization-resolved SHG microscopy experiments, and has permitted full determination of the orientation of single domain ferroelectric nano-crystals. The electrooptic phase response obtained in the form of phase images and polarization diagrams yields the full orientation in the laboratory frame of randomly dispersed single nano-crystals, together with their electric polarization dipole. The complete vector determination of the dipole orientation is a prerequisite to important applications including ferroelectric nano-domain orientation, membrane potential imaging and rotation dynamics of single biomolecules, especially by using a new low-cost non-invasive imaging method with a low intensity illumination beam.The ferroelectric domain pattern of periodically poled KTiOPO4 and of a two-dimensional decagonal quasi-periodic LiNbO3 nonlinear crystal was determined by local measurement of their electro-optically induced phase retardation. Owing to the sign reversal of the electrooptic coefficients upon domain inversion, a 180 degree (pi) phase shift is observed across domain barriers between domains with opposed orientations. PLEOM allows to reveal the nonlinear and electrooptic spatially modulated patterns in ferroelectric crystals in a non-destructive manner and to determine their poling period, duty cycle and short-range order as well as to detect local defects in the domain structure, such due to incomplete poling.In addition, we have also proposed and demonstrated a new method, based on the voltage dependence of the electrooptic dephasing, to mimic the membrane potential in cells, working at this stage on nonlinear dye containing phospholipidic membranes, grown in a microfluidic set-up.

Orientador: Luis Eduardo Evangelista de Araujo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T01:12:06Z (GMT). No. of bitstreams: 1 Carvalho_SilvaniaAlvesde_M.pdf: 47841969 bytes, checksum: 80b56cd870f97d9119c7f4935d7685ad (MD5) Previous issue date: 2006 / Resumo: Neste trabalho estudamos o fenômeno de transparência induzida eletromag-neticamente (EIT) em sistemas de três níveis nas configurações lambda, V e cascata. Nestes sistemas, a transparência de um feixe de prova é induzida por um feixe de acoplamento mais forte. Uma comparação sistemática da largura do sinal de EIT e da dispersão no meio para os três sistemas, usando diferentes valores relativos de comprimento de onda dos dois feixes, é apresentada para meios atômicos alargados inomogeneamente. A dependência da EIT com o ângulo entre os feixes de prova e acoplamento é também investigada. Observamos que, embora os sinais de EIT mais estreitos e profundos, e uma maior inclinação da curva de dispersão sejam obtidos para o sistema lambda, o sistema V é o mais robusto com relação ao ângulo entre os feixes e ao comprimento de onda relativo dos feixes. Por fim, apresentamos os resultados obtidos no experimento realizado em um sistema de 3 níveis na configuração cascata levando em conta os níveis 1S01 1P01 e 1D2em átomos de cálcio, descrevendo o uso inédito da técnica de deteção optogalvânica na observação de EIT. Neste experimento observamos EIT em uma lâmpada de catodo oco de Ca com vapor de fundo de Kr que nos forneceu até 76% de cancelamento da absorção de um laser em 423 nm induzido por um laser amarelo 586 nm forte contrapropagante. EIT neste mesmo sistema cascata considerando uma geometria copropagante dos feixes de laser foi observada / Abstract: In this work we studied the phenomenon of electromagnetically induced trans-parency (EIT) in three level systems in the L, Vee and cascade configurations. In these systems, the transparency of a probe beam is induced by a strong coupling beam. A systematic comparison of the EIT signal width and the dispersion in the medium for the three systems for different relative values of wavelength of the two beams is presented for inhomogeneously Doppler-broadened medium. EIT dependence on the angle between the probe and coupling beams is also investigated. We observe that although the narrowest and deepest EIT signal, and the greatest slope of the dispersion curve are obtained for the L system, the V system is the more robust relative to the angle between the beams and to the relative wavelength of the beams. Finally, we present the results obtained in an experiment in a three level cascade system considering the levels 1S01 1P01 and 1D2 in Ca atoms. We describe, for the first time to our knowledge, the use of the optogalvanic detection technique for observing EIT. In this experiment we observed EIT in a Ca hollow cathode lamp with Kr buffer gas, obtaining up to 76% cancellation of absorption of a blue laser beam (423 nm) induced by a strong and counterpropagating yellow beam (586 nm). EIT in a cascade system considering a copropagating geometry of the laser beams was observed. / Mestrado / Física Atômica e Molecular / Mestre em Física