Estudo e aplicações do fenômeno de absorção de dois fótons em moléculas azo-aromáticas / Studies and applications of two-photon absorption in azo-aromatic molecules
AUTOR(ES)
Ubaldo Martins das Neves
DATA DE PUBLICAÇÃO
2007
RESUMO
Here we investigated fundamental and applied aspects of the two-photon absorption process in azoaromatic compounds. Azoaromatic molecules have been studied in the last few years due to their applications in optical storage devices, light modulators and surface relief gratings, processes related to the photo-isomerization mechanism. The main focus of the results presented in this thesis was to explore the two-photon absorption process, taking advantage of the intrinsic photo-isomerization of the azo-aromatic chromophores. Our main goal was to study the advantages of utilizing intense pulses, which promote nonlinear excitation, to develop application with azo-aromatic compounds. Initially, we studied the two-photon absorption process in a new class of azo-aromatic compounds, named Salen Dyes. We investigated the influence of metal ions, presented in the Salen Dyes structure, on the two-photon absorption spectrum. Our results revealed that the metals have practically no influence in the nonlinear optical properties due to the lack of conjugation between the azo-moieties in the Salen Dyes. Through a theoretical model based on a sum-over-states calculation, we were able to determine the transition dipole moment of these molecules. Subsquently, we implememnted a technique to study the two-photon induced birefringence, resulting from the molecular re-orientation, in azo-aromatic compounds. We observed that the two-photon induced birefringence is confined to the focal volume, s demonstrated in a three dimensional optical storage experiment. Finally, we used coherent control processes to manipulate the two-photon induced birefringence in azo-compounds. It was demonstrated that it is possible to modulate the optically induced birefringence by manipulating the phase of the ultra-short pulses, via pulse shaping techniques.
ASSUNTO(S)
absorção de dois fótons armazenamento óptico azoaromatic compounds compostos azo-aromáticos optical storage two-photon absorption
