CaracterizaÃÃo Ãptica de materiais nanoestruturados por tÃcnicas de geraÃÃo de segundo e terceiro harmÃnico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work is dedicated to the optical characterization of nanostructured materials that are of interest for non-linear optics, optoelectronics and nanophotonics. The hyper- Rayleigh scattering (HRS) technique and the third harmonic generation (THG) technique were used. The materials investigated were a glass-ceramics containing sodium niobate (NaNbO3) nanocrystals and colloids containing nanoparticles (NPs) of barium titanate (BaTiO3) and lead titanate (PbTiO3). Chapter 1 gives an introduction to nanostructured materials and its relations to nonlinear optics. In the same chapter we describe some particular properties of the materials investigated as well as the fabrication processing of the samples. Chapter 2 describes theoretically the generations of coherent and incoherent harmonics. Chapter 3 and 4 are dedicated to describe the HRS and the THG techniques. In chapter 3 we present the determination of first hyperpolarizability, β, of NaNbO3 NPs. This experiment represents the first investigation of a glass ceramics using HRS. We also determined the value of β for BaTiO3 and PbTiO3 NPs suspended in colloids. The β value of NaNbO3 NPs was much smaller than the values already known for semiconductor NPs of the same size. On the other hand the value of β for BaTiO3 and PbTiO3 NPs have the same order of magnitude than for semiconductor NPs. In chapter 4 the THG technique is utilized for the determination of the third order susceptibility χ(3) of transparent materials. For this work we used the Maker fringes method that is traditionally applied with monochromatic pulses. With this method it is possible to determine the coherence length of materials and the χ(3). In our work we performed the experiment for the first time with femtosecond pulses and developed a method for the determination of the dispersion curve of materials and the value of χ(3). The method was confirmed by experiments with quartz and two commercial glasses (BK7 and B270). Also the method was used for the characterization of the glassceramics containing NaNbO3 nanocrystals

ASSUNTO(S)

nanopartÃculas vitrocerÃmicas geraÃÃo de terceiro harmÃnico fisica third harmonics generation glassceramics nanoparticles hyper-rayleigh scattering espalhamento hiper-rayleigh

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