Long-haul optical fiber communication system is an important infrastructure to support the latest broadband communication in the world. It is important to study a technology to improve the performance of such system, and the Return-to-Zero Differential Phase Shift Keying (RZ-DPSK) modulation attracts much attention because of its improved long distance transmission performance. One important technology of the current long-haul optical fiber communication system is the dispersion map, and it is widely deployed for already installed undersea optical fiber communication system in the world. Recently, a new dispersion map that was totally different from the map used for already deployed system was proposed, and it demonstrated advantageous performance of the long-haul RZ-DPSK transmission. Even though, the reason of the performance improvement is not investigated, and it is important to clarify the physical mechanism of the performance improvement, because it will contribute to improve the system design of the long-haul optical fiber communication systems in near future. In this master thesis, the performance of the RZ-DPSK format in the long-haul transmission system is studied. Both computer simulations and experiments are conducted to confirm the effects of various factors in the long-haul RZ-DPSK transmission system. From the theoretical study, it is pointed out that the Self-Phase Modulation (SPM) played a significant role to degrade the transmission performance of the conventional map, while it does not cause so significant degradation in the new map. The effects of the SPM and the Cross-Phase Modulation (XPM) with the conventional map are investigated through the experimental study.

This study researches the nonlinear optical properties of the blue phase liquid crystals using the Z-scan technique. The purpose is to investigate the non-linear effect of the blue phase liquid crystals induced by the thermal and the liquid crystal reorientation effect. The Z-scan technique is common method to measure the non-linear index n2 and the non-linear absorption coefficient of materials. The measurement of the optical Kerr constant using Z-scan is based on the principle of spatial beam distortion due to the self-focusing or self-defocusing. For typical nematic liquid crystals, the nonlinear effect in the nematic phase is large than that in the isotropic phase. However, due to the anisotropic properties of the liquid crystal, the light-induced nonlinear effect in the nematic phase is polarization dependency. Unlike nematic phase, the blue phase is optical isotropic duo to its symmetric structure, and therefore blue phase are polarization independent and provide a larger non-linear effect. The experiments to measure the nonlinear refractive index n2 are as follows: firstly, a linearly polarized Ar+ laser light (£f=532nm) is focused in the z direction onto the sample via lens, and the detector was set behind the sample. Sequentially, the light intensity is recorded while the sample is scanned near the beam waist of the green laser. Finally, the non-linear index n2 of the material is derived from mathematical calculation. The study investigated two kinds of material, pure blue phase liquid crystal and dye-doped blue phase liquid crystal, and measured their non-linear index n2 in the blue phase and isotropic phase, respectively. The experimental results show that the non-linear index n2 of dye-doped blue phase liquid crystal is 100~1000 times as large as this of the pure blue phase liquid crystal at the blue phase. Besides, compared with isotropic phase in the blue phase liquid crystal, the blue phase actually possesses larger non-linear index n2. This experiment confirms that the nonlinear effect can be induced using linearly polarized Ar+ laser, and the nonlinear refractive index n2 can be measured using Z-scan technique.

Controlling the absolute stereochemistry of molecules is a major challenge to contemporary chemists. Achieving high enantioselectivity with catalytic amounts of a chirality transfer (or inducing) agent, and the ease of regenerating such catalysts is yet another challenge. Due to the involvement of various transition metal complexes, the relatively young field of enantioselective catalysis has emerged as a powerful tool for organic chemistry. In our efforts towards the synthesis of a universal catalyst, O'Donnell Schiff base derived tetradentate ligands were shown to catalyze dialkylzinc additions to aldehydes in high selectivity. The three pot synthesis of bifurcated dipeptides in very good yields and the mechanistic aspects of diethylzinc additions to aromatic aldehydes are described in this dissertation. The chiral Lewis acidic behavior of these ligands was supported by a mechanistic study done examining the nonlinear effect. Unlike bidentate ligands such as (-)-3-exo-N,N-dimethylaminoisoborneol (DAIB), the tetradentate ligands in this study show strictly linear behavior. Also, the linear free energy relationships studied by observing the enantioselectivity with respect to electron donating or withdrawing substituents on the benzaldehyde substrates supported a Lewis acid role for the zinc complexes. A negative slope was obtained when ee's were plotted against sigma values of the substituted benzaldehydes. Since they bind to various bivalent transition metal cations, these ligands can be viewed as privileged structures, and may potentially become catalysts for various asymmetric reactions. As catalyst screening can be greatly facilitated by heterogeneous catalysis, solid phase ligands were synthesized using Wang and Merrifield resin supports. The synthetic methodology was developed using a diarylketimine linker with the aid of on-bead characterization techniques such as 13C NMR and UV-VIS spectroscopy. The ligands were shown to asymmetrically catalyze the alkenylzinc additions to aromatic aldehydes. In situ generation of alkenylzinc reagents by boron to zinc transmetalation followed by the addition to benzaldehyde in the presence chiral zinc complexes resulted in enantiomerically enriched allylic alcohols. The preliminary results for this transformation resulted in 3:1 selectivity in favor of S-isomer.

The linear propagation of optical beams through a transvers al periodic pattern, such as an optically induced lattice, have been reported to induce power oscillations between a pair of Fourier modes related by the Bragg resonance condition. These are Bloch modes with frequency within the band gap and thus, confined to the transversal plane (x,y), but otherwise traveling freely in the z-direction. Stemming from the coupling between the light beam and the periodic lattice, these twin-mode power oscillations have been referred as Rabi optical oscillations, due to the analogy with matter Rabi oscillations. In this work, investigates numerically investigate the behavior of such Rabi-type oscillations, under the influence of a selfdefocusing nonlinearity along the propagation direction. Is considered the incidence of a light pulse characterized by a Gaussian spectrum centered in one of the modes of the twin pair, into a one-dimensional photonic structure, with a periodic modulation of the optical refractive index lying in a transversal direction x. For a weak nonlinearities, observed an interesting interplay between linear twin coupling and selfdefocusing: the selfdefocusing effect spread energy of the central frequency to new neighboring modes occurring within the Gaussian spectrum input, centered in one mode of the pair, and transfer proportion of this energy to the correspondent resonant mode. In this way the center mode or frequency component of the spectrum in the presence of selfdefocusing effect, oscillates from one extreme to ano ther within the Brillouin zone. By increasing the nonlinearity, one finds a balanced combination of both effects, that is, Bragg resonance and selfdefocusing, which promotes the transference of the nonlinear reshaping of a Gaussian spectrum, occurring around the central frequency at the input, to the neighborhood of its twin mode. Thus, the nonlinear Rabi oscillations might reveal itself quite useful for optical techniques and optical devices in the sense that, by suitably tailoring the electromagnetic space one could allow the tuning of the nonlinear frequency spreading. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A propagação linear de feixes ópticos através de um padrão periódico transversal, como uma rede induzida opticamente, é conhecida por induzir as oscilações de potência entre um par de modos de Fourier relacionados pela condição de ressonância de Bragg. Estes são os modos de Bloch com frequência dentro do band gap, por conseguinte, confinados no plano transversal (x,y), mas viajam livrementena direção z. Partindo do acoplamento entre um feixe óptico e a rede periódica,essas oscilações das potências dos modos acoplados têm sido referidas como as oscilações de Rabi ópticas, devido à analogia com as oscilações de Rabi na matéria. Neste trabalho, investiga-se numericamente o comportamento de tais oscilações tipo Rabi, sob a influência da não linearidade de autodesfocalização ao longo da direção de propagação. Considera-se a incidência de um pulso de luz caracterizado por um espectro Gaussiano, centrado em um dos modos do par acoplado, em uma estrutura fotônica unidimensional com uma modulação periódica do índice de refração na direção transversal x. Para uma não linearidade fraca, pode-se observar uma interessante interação entre os dois modos acoplados em regime linear e o efeito de autodesfocalização: O efeito de autodesfocalização distribui energia da frequência central para os novos modos vizinhos, dentro do espectro inicialmente Gaussiano, centrado em dos modos acoplados, e transfere parte dessa energia para o modo ressonante correspondente. Desta forma, o modo ou a componente de frequência central do espectro na presença do efeito de autodesfocalização oscila de um extremo a outro dentro da zona de Brillouin. Ao aumentar a não linearidade, encontra-se uma combinação balanceada de ambos os efeitos, que são, ressonância de Bragg e autodesfocalização, que promovem a transferência não linear remodelando o espectro Gaussiano, que ocorre na entrada em torno de uma frequência central, para seu modo vizinho. Assim, as oscilações de Rabi não lineares podem revelar-se bastante proveitosas para técnicas ópticas e dispositivos ópticos no sentido de que, atravésde um espaço eletromagnético adequado permitir a sintonia de espalhamento não linear da frequência.

Cette thèse expérimentale porte sur les ondes ultrasonores se propageant dans un milieu granulaire sec, sous contrainte. Dans une première partie, on s'intéresse à la propagation des ondes cohérentes de grande longueur d'onde. La mesure des vitesses de ces ondes en fonction de la contrainte et de la fréquence, montre que les propriétés élastiques du milieu résultent du contact de type Hertz-Mindlin, et que le milieu est non dispersif. La mesure d'atténuation indique un mécanisme dominant du type diffraction de Rayleigh. La propagation d'une onde de Biot à travers l'air dans un empilement sous gravité a été aussi mise en évidence. Dans une seconde partie, on s'est intéressé à la diffusion multiple d'onde acoustique. Nous avons déduit le coefficient de diffusion et le temps inélastique d'absorption en fonction de la contrainte et de la fréquence d'excitation. Le libre parcours moyen de transport a été déterminé en fonction du rapport de la longueur d'onde sur la taille de grains, montrant deux régimes distincts à basse et à haute fréquence. La dernière partie, porte sur le comportement non linéaire hystérétique d'un milieu granulaire, par méthode de résonance. Les modes fondamentaux d'ondes cohérentes ont été étudiés en fonction de l'amplitude d'excitation et de la contrainte de confinement. Un ramollissement élastique de 10%, pour l'onde longitudinale, et de 20%, pour l'onde transversale, sont observés, en bon accord avec un modèle de milieu effectif basé sur la théorie de Mindlin. Les effets d'interaction irréversible son-matière ont été examinés, tels que la compaction intermittente et le processus de cicatrisation. Enfin, on observe que l'atténuation de l'onde transversale dépend conjointement de l'amplitude d'excitation et de la fréquence / This experimental work deals with the ultrasound propagation in a dry granular medium under stress. The first chapter of the thesis concerns the coherent wave propagation in the long-wavelength limit. The measurement of sound velocity as a function of the applied stress and wave frequency confirm that the nonlinear elasticity of the medium originates from the Hertz-Mindlin contact and show that the medium is free of velocity-dispersion. On the other hand, the amplitude measurement reveals that the dominant mechanism of attenuation is due to the Rayleigh-like scattering. Additionally, the airborne Biot wave is observed and investigated. The second chapter is devoted to the diffusively scattered ultrasound. We particularly determine the diffusion coefficient and the inelastic absorption time as a function of stress and frequency. The mean transport free path was investigated versus the ratio of the wavelength to the grain size, which shows two distinct behaviours at low and high frequencies, respectively. The third and last chapter is focused on the hysteretic nonlinear behaviour studied by the resonance method. The fundamental modes of coherent waves are investigated as a function of the applied stress and excitation amplitude. The softening of elastic modulus is observed and can rises to 10% for the longitudinal wave and 20% for the transversal wave, which are in good agreement with the model prediction based on the Mindlin friction theory. Furthermore, the irreversible sound-matter interaction is examined; the intermittent compaction and the slow healing process are observed. Finally, the attenuation of transversal waves is shown to depend simultaneously on wave amplitude and frequency

Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificiels. / This work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers.