This thesis proposes the platform for the observation of a new type of electromagnetic interface mode, Coupled Interface Mode, and studies the utilization of this mode in second order nonlinear interaction in AlGaAs. The dispersion relations for theoretical examination of the modes are developed and used to design a waveguide structure that accommodates a three wave mixing process utilizing coupled interface modes. The waveguides are fabricated according to optimized fabrication recipes and characterized for linear and nonlinear properties. Second harmonic generation is adopted for the demonstration of nonlinear interaction, due to its convenient experimental set-up. Three different laser sources are used to pump the waveguides and second harmonic light is generated and characterized. Coupled interface modes in conjunction with other types of modes also existing within the same structures, offer the possibility to explore three-wave mixing processes such as sum and difference frequency generation.

This thesis proposes the platform for the observation of a new type of electromagnetic interface mode, Coupled Interface Mode, and studies the utilization of this mode in second order nonlinear interaction in AlGaAs. The dispersion relations for theoretical examination of the modes are developed and used to design a waveguide structure that accommodates a three wave mixing process utilizing coupled interface modes. The waveguides are fabricated according to optimized fabrication recipes and characterized for linear and nonlinear properties. Second harmonic generation is adopted for the demonstration of nonlinear interaction, due to its convenient experimental set-up. Three different laser sources are used to pump the waveguides and second harmonic light is generated and characterized. Coupled interface modes in conjunction with other types of modes also existing within the same structures, offer the possibility to explore three-wave mixing processes such as sum and difference frequency generation.

After decades of development, optical fiber technology has reached a high degree of sophistication and maturity, and currently serves as the backbone of today''s internet. Despite its technical versatility and capability, current silica fiber technology still has a significant flaw: since silica fibers only possess very weak second order nonlinearity, it has been impossible to develop a large number of important nonlinear optical devices and instruments, such as optical parametric amplifiers (OPA) and optical parametric oscillators (OPO). In this thesis,we show how to overcome this intrinsic limitation, and introduce second order nonlinearity into silica fiber devices. / Master of Science

Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of χ(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices. In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation. The effect of adding ionic salts to the dye solutions was studied, with hopes of increasing the chromophore density in the film by shielding inter-dye electrostatic repulsions. A linear relationship in deposited amount, as characterized by absorbance/bilayer, was observed as the salt concentration was increased. Little effect on χ;(2) was observed for films made with the as-received Procion Red MX-5B chromophore. However, films fabricated from purified Procion Brown MX-GRN showed a definite dependence on added salt. Exceptional χ(2) values were obtained for Procion Brown films deposited using 0.5 M NaCl and PAH. The importance of depositing from non-aggregated solutions was again highlighted, as films made with the less soluble Procion Orange were significantly less homogeneous than those made from Procion Red and Procion Brown which were highly soluble. The role of polycation structure on the deposition and orientation of Procion Brown and Red was examined. / Ph. D.

Owing to its centrosymmetric structure, the critical optical component of a silica fiber cannot to possess a second-order nonlinear optical susceptibility, Χ(²), preventing a silica fiber from many potential applications. Here, we theoretically and experimentally demonstrate a new technique to generate large and thermodynamically stable second-order nonlinearity into silica optical tapered fibers without breaking the centrosymmetry of the silica glass. The nonlinearity is introduced by surface layers with high polar-ordering fabricated by a novel hybrid covalent/ionic self-assembly multilayer technique. Despite the overall rotational symmetry of the nonlinear fiber, we observe significant second harmonic generation with ~ 400–500 fold enhancement of the SHG power compared to the traditional tapers. Phase matching for a SHG process in second-order nonlinear tapered fibers is also realized by the compensation of waveguide modal dispersion with material chromatic dispersion, which occurs only for submicron tapers where the modal dispersion is large. In addition, quasi-phase-matching for a nonlinear taper can be accomplished by introducing a periodic pattern into the nonlinear film coating. We use UV laser ablation for the controlled removal of particular nonlinear film segments on a taper surface in order to produce a Χ(²) grating structure. A resulting SHG enhancement from quasi-phase-matching is observed over a broadband spectrum of the pump light mainly due to the non-uniform shape of a taper waveguide. The laser ablation is a clean and fast technique able to produce well-define patterns of polymer films on either flat or curved substrate geometry. With surface layers containing reactive functional groups e.g. primary amines, we demonstrate that the resulting patterned film obtained from the laser ablation can be used as a template for further self-assembly of nanoparticles with high selectivity. A pattern feature size down to ~ 2μm or smaller can be fabricated using this approach. We also discuss preliminary results on a novel technique to further improve spatial accuracy for selective self-assembly of nanoparticles at an unprecedented level. Different types of nanoparticles are joined in order to form well-defined, molecular-like superstructures with nanoscale accuracy and precision. The technique is based on a selective surface functionalization of photosensitive molecules coated on metallic nanoparticles utilizing enhanced two-photon photocleavage at the plasmonically-active sites (hot spots) of the nanoparticles in resonance with an applied electromagnetic wave. As a result, the surface functional groups at the nanoparticle hot spots are different from the the other areas, allowing other kinds of nanoparticles to self-assemble at the hot spots with high degree of selectivity. / Ph. D.

Au cours des dernières années, les matériaux optiques non linéaires ont attiré beaucoup d'attention en raison de leur application dans les télécommunications optiques. Les vitro-céramiques pour l’optique non-linéaire, ayant une microstructure alignée, présentent des propriétés physiques anisotropes. Il est donc intéressant de maîtriser la cristallisation dans ce genre de verre. Nous avons étudié ici la distribution, la taille et l'orientation sous un champ supplémentaire, en particulier par l’irradiation femtoseconde, de verres silicatés. Ce travail est important pour la conception et la production de nouveaux matériaux optiques non linéaires multi- fonction. Dans cette thèse, le champ thermique a été utilisé pour produire des cristaux dans un verre SrO-TiO₂-SiO₂. L’analyse a été menée à l’aide de la méthode des franges de Maker et de de diffraction des rayons X pour étudier la cristallisation et les propriétés optiques non-linéaires. Il a montré que les cristaux non linéaires Sr₂TiSi₂O₈ peut être obtenue dans la couche de surface par traitement thermique. L'axe polaire de cristaux orientés est perpendiculaire à la surface du verre. En augmentant la température ou en prolongeant la durée de traitement thermique, l’apparition d’une intensité non-nulle de génération de second harmonique (GSH) en incidence perpendiculaire indique la présence de cristaux orientés de manière aléatoire dans le volume du verre. Etant donné la cristallisation, spatialement difficile à contrôler par traitement thermique, l’irradiation laser femtoseconde pour contrôler la cristallisation dans le verre sont proposée en raison de son contrôle précis du dépôt d'énergie dans le temps et dans l'espace. Il ouvre des possibilités fantastiques pour la fabrication de matériaux multifonctionnels par maîtrisant la cristallization des cristaux non linéaires dans le verre. Nous avons précipité des cristaux orientés de LiNbO₃ et de Sr₂TiSi₂O₈ en volume par irradiation laser femtoseconde à haute cadence (typ. 300 kHz). Dans le verre Li₂O-Nb₂O₅-SiO₂, les micro-/nano-cristaux en variant l'énergie d'impulsion et la direction de polarisation ont obtenu. En particulier, lors de l'application à basse énergie et de la polarisation parallèle à la direction d'inscription du laser, la cristallization orientée en nanomètre a été démontrée par EBSD (Electron diffraction rétro-diffusée). Le mesure microscopique de SH a prouvé l’orientation préférentielle de cristallisation parallèlement à la direction de déplacement du faisceau laser. Afin de comprendre l'orientation exacte des cristaux par rapport à la direction d'écriture, une série de mesurer les signaux cohérent de SH ont été réalisés dans des paires de lignes de laser avec des orientations de déplacement opposées. EDS (spectromètre à dispersion d'énergie) et la micro-sonde nucléaire ont été utilisées pour réaliser l'analyse chimique dans les lignes de laser. Nous discutons aussi le mécanisme de cristallisation orientée en mode statique et en mode dynamique en illustrant la distribution des gradients différents. Pour le système SrO-TiO₂-SiO₂, l'irradiation du laser a été appliquée dans les verres stoechiométrique et non-stoechiométrique. Dans le premier cas, non seulement la taille et la distribution peuvent être contrôlées en variant les paramètres du laser, mais aussi la phase peuvent être choisis dans l'échantillon. La mesure de SH a montré que l'axe polaire de cristaux est toujours dans le sens de l'écriture. Pour le verre non-stoechiométrique, des purs cristaux de Sr₂TiSi₂O₈ ont été obtenus seulement. En utilisant EBSD, l'écriture asymétrique ont été étudiés en variant l’orientation de la polarisation et de l'écriture. On a montré ainsi que le mécanisme d'orientation est probablement dû à l'action combinée du front « tilté » de l’impulsion et à l’orientation du plan de polarisation qui conduit à une photosensibilité anisotrope. En conséquence, cela induit une distribution asymétrique des gradients thermiques et chimiques. / In the past few years, nonlinear optical materials have attracted much attention due to their application in optical telecommunications. Nonlinear optical glass-related materials have been widely studied according to their advantages. Glass ceramics having an aligned microstructure would exhibit an anisotropy of physical properties. This dissertation mainly contributes to the control of micro/nano-crystallization in silicate glass in crystalline phase, distribution, size and orientation under additional field, particularly by femtosecond irradiation, to master the nonlinear optical properties of glass further. This work is significant for the design and production of novel nonlinear optical material with multi-function in future. In this thesis, thermal field was used to induce crystals in SrO-TiO₂-SiO₂ glass. The crystallization behavior of glasses in different heat-treated condition and their second-order nonlinear optical properties have been analyzed by Maker fringes method and X-ray diffraction measurement, respectively. It showed that the oriented crystallization of nonlinear Sr₂TiSi₂O₈ crystals can be obtained in the surface layer by heat treatment. The polar axis of oriented crystals was perpendicular to the sample surface. Moreover, by applying higher temperature or prolonging the time duration of heat treatment, the maximum intensity of second harmonic generation shifting toward 0º is likely due to the presence of randomly distributed crystals in glass and surface crystallization turns to be volume at this moment. However, since it is hard to control crystallization by heat treatment and time-consuming, femtosecond laser irradiation was proposed to realize the control of crystallization in glass owing to the accessible control of energy deposition in time and in space. It opens fantastic opportunities to manufacture novel multifunctional materials by manipulating the crystallization of nonlinear crystals embedded in glasses. Therefore, we achieved to precipitate preferential oriented LiNbO₃ and Sr₂TiSi₂O₈ crystals in glass with femtosecond laser irradiation at high repetition rate (typ. 300 kHz). In Li₂O-Nb₂O₅-SiO₂ glass, we obtained micro-/nano-crystals in glass sample by varying pulse energy and polarization direction. Specifically, when applying low pulse energy and polarization parallel to laser writing direction, the oriented nano-crystallization has been obtained as shown by EBSD (Electron back-scattered diffraction). Second harmonic (SH) microscopy measurement illustrated preferred orientation of crystallization in laser lines. In order to understand the exact orientation of crystals with respect to the writing direction, a series of coherent SH measurement has been achieved in pairs of laser lines written in opposite orientation. EDS (Energy Dispersive Spectrometer) and nuclear micro-probe has been used to realize the chemical analysis in laser lines. The mechanism of oriented crystallization was discussed both in static mode and in dynamic mode through illustrating the distribution of different gradients. In SrO-TiO₂-SiO₂ system， laser irradiation was applied both in stoichiometric and non-stoichiometric glasses. In the former case, not only the size and distribution can be controlled by varying laser parameters, but also the crystalline phase can be chosen in samples. SH microscopy measurement was used to characterize the nonlinear properties of glass and it implied that the polar axis of crystals is always along the writing direction. In non-stoichiometric glass, only pure Sr₂TiSi₂O₈ crystals were obtained. The asymmetric writing involving oriented crystallization has been studied by varying polarization and writing orientation. The orientational dependent is likely due to the combined action of oblique pulse front tilt affected by the polarization orientation plane leading to different anisotropic photosensitivity and its aftereffects to induce asymmetric distribution of thermal and chemical gradients.

Les molécules organométalliques présentant d’intéressantes propriétés, notamment en optique non linéaire (ONL), en luminescence et en photovoltaïque, trouvent leur utilité dans la préparation de nouveaux matériaux pour des applications dans les domaines de l’optoélectronique, de la photonique et des cellules solaires à colorant photosensible (DSSC). Ce manuscrit de thèse présente la synthèse et les résultats des propriétés ONL du second ordre de nouveaux complexes dissymétriques push-pull de motif D–π–M–π–A et basés sur les diacétylures de platine (II), les diacétylures de ruthénium (II) et les dérivés du ferrocène. Ces complexes sont constitués de ligands du méthylènepyrane en tant que groupes électrodonneurs pro-aromatiques (D) et de ligands formaldéhyde, indane-1,3-dione, pyrazine, pyrimidine ou iodure de pyrimidinium en tant que groupes électroattracteurs (A), ces deux groupes étant séparés par le centre métallique et différents espaceurs π-conjugués. La réponse en optique non linéaire (ONL) du second ordre des complexes a été mesurée à l’aide de la méthode EFISH (Electric-Field-Induced Second Harmonic) et a été comparée à celle de leurs analogues tout organiques. Tous les complexes ont donné des valeurs µβ de la réponse ONL, fortement augmentées par la méthylation de la pyrimidine. En utilisant les mêmes types de groupes électrodonneurs et électroattracteurs, les plus fortes réponses ONL ont été obtenues avec les complexes de ruthénium. Pour l’un d’entre-eux, une valeur µβ0 particulièrement élevée de 6000.10-48 esu a pu être mesurée. / Organometallic molecular systems exhibiting interesting properties, such as non-linear optical (NLO) responses, luminescence and energy photoconversion, are of great interest in the preparation of novel materials with potential applications in opto-electronics, photonics and Dye-Sensitized Solar Cells (DSSC). This manuscript highlights the synthesis, characterization and the second-order NLO properties of new asymmetrical D–π–M–π–A push–pull dialkynyl ruthenium- and platinum-based as well as dialkenyl ferrocene-based complexes. All complexes incorporate pyranylidene ligands as pro-aromatic donor groups (D) and formaldehyde, indane-1,3-dione pyrazine, pyrimidine or pyrimidinium iodide as electron-withdrawing groups (A) separated by the metal fragment and various π-linkers. The second order nonlinear optical (NLO) properties of all complexes were measured by the electric-field-induced second harmonic generation (EFISH) technique and compared to those of their purely organic analogs. All complexes exhibited µβ values, which dramatically increased upon methylation of the pyrimidine group. With the same donor–acceptor group combination, the strongest NLO response was obtained with the ruthenium complexes, which exhibited a remarkably high µβ0 value of 6000.10-48 esu.

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