O efeito Raman ressonante do complexo (NH4)4Mo2Cl8.NH4Cl.H2O, contendo o íon Mo2Cl84-, foi estudado tanto na temperatura ambiente como na de nitrogênio líquido. Com base nos resultados obtidos mostra-se que a explicação previamente oferecida por outros autores para o aparecimento de ressonância com excitação em 568,2 nm não é correta. É sugerida uma explicação diferente para este comportamento baseada nos espectros Raman e de absorção. A transferência de elétron fotoestimulada no íon complexo (NH3)5RuII-pz-CuII foi comprovada através do estudo do efeito Raman ressonante. Com base nos espectros Raman obtidos em condições de ressonância e também nas medidas de polarização, o estado eletrônico excitado envolvido foi caraterizado. Os perfis de excitação para v1 e 2vl do íon RuO42- em solução aquosa foram obtidos usando diversas radiações excitantes. Os perfis mostraram uma desintensificação das intensidades Raman pré-ressonantes na região da transição interna do íon. O efeito foi interpretado usando o tratamento proposto por Stein e col. para o efeito Raman anti-ressonante. / The Raman resonance effect of the complex (NH4)4Mo2Cl8.NH4Cl.H2O, containing the Mo2Cl84- ion, was investigated at both room and liquid nitrogen temperatures. On basis of the obtained results it is shown that the previous explanation given by others authors for the resonance observed with 568.2 nm excitation is not a correct one. A different explanation for this behaviour is suggested, based on the Raman and absorption spectra. The photostimulated electron transfer in the complex ion (NH3)5RuII-pz-CuII was confirmed trough the investigation of its Raman ressonance effect. The Raman ressonance spectra and the polarization measurements had enabled the characterization of the electronic excited state involved in the transition. The excitation profiles of v1 and 2v1 of the RuO42- ion in aqueous solution were obtained using several exciting radiations. The profiles present a de-enhancement of the pre-resonant Raman intensities in the region of the ion internal transition. This effect was interpreted using the treatment proposed by Stein et al. for the anti-resonance Raman effect.

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007) Vita. Includes bibliographical references.

RESUME Parmi les divers processus permettant l'amplification optique indispensable aux systèmes de télécommunications par fibre, l'effet Raman, basé sur l'échange de puissance entre un signal et un laser de pompe de fréquence supérieure à travers un couplage avec les vibrations moléculaires de la silice, permet d'amplifier à n'importe quelle longueur d'onde avec une grande bande passante. Un des inconvénients majeurs de cette technique est la forte puissance optique nécessaire à sa réalisation qui génère l'apparition de nombreux effets non linéaires potentiellement dommageables pour la bonne transmission du signal. L'interaction des effets Kerr ou de la diffusion Brillouin avec les autres caractéristiques de la propagation dans les fibres peut entraîner une diminution des performances. Dans la première partie de cette thèse, nous décrivons un nouveau processus d'élargissement spectral induit par l'effet Kerr dans les amplificateurs Raman fibrés. Nous avons également mis à jour ce même processus dans les lasers Raman. L'application de ce phénomène à la suppression de la diffusion Brillouin est ensuite démontrée avec succès. La deuxième partie de ce travail démontre comment tirer avantage des effets non linéaires afin de générer des impulsions optiques de haute puissance dans un laser Raman fibré. Enfin, dans la troisième partie, nous proposons et démontrons l'application de deux nouvelles méthodes de caractérisation à la mesure de la distribution des effets Raman et Kerr le long des fibres optiques grâce à une technique de réflectométrie optique cohérente. SUMMARY Among the various processes that allow optical amplification that is required for fiber telecommunication systems, the Raman effect, based on the power exchange between a signal and a pump laser with higher frequency through a coupling with molecular vibrations of silica, enables to amplify at any wavelength with a large bandwidth. One of the major drawbacks of this technique is the high power required to realize it, generating the appearance of numerous nonlinear effects, potentially harmful for the quality transmission. The interplay between Kerr effects or Brillouin scattering and other propagation characteristics of optical fibers can lead to a decrease of the performances. In the first part of this thesis we describe a new broadening mechanism induced by the Kerr effect in Raman fiber amplifiers. This effect was also discovered in Raman fiber lasers. An application of this phenomenon as an efficient way to suppress Brillouin scattering is then successfully demonstrated. The second part of this work demonstrated how to take advantage of optical nonlinearities to generate high peak power pulses with a Raman fiber laser. Finally, in the third part, we propose and demonstrate the application of two new methods to measure the spatial distribution of Raman and Kerr effects along optical fibers thanks to a coherent optical reflectometry technique.

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Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Fizik Anabilim Dalı, 2009. / Kaynakça var.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 107-119).

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published_or_final_version / Chemistry / Master / Master of Philosophy

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