Espectroscopia Ãptica nÃo linear de vidros especiais e colÃides

AUTOR(ES)

Luis Arturo GÃmez MalagÃn

DATA DE PUBLICAÇÃO

2008

RESUMO

Nonlinear optical properties of special glasses and colloids were studied using the zscan technique. This technique aalows to calculate the nonlinear refraction index and the nonlinear absorption coefficient using the self-focusing or defocusing effect that appears when the incident laser pass through a nonlinear medium. Orthophosphate and polyphosphate antimony glasses were characterized using femtosecond laser with 150 fs pulses at telecom wavelengths (1400-1600 nm). Values of the nonlinear refraction index, n2, S10-15 cm2/W were measured and nonlinear absorption coefficients, &2, less than 0.003 cm/GW were estimated. Figures of merit (FOM) were determined and the results show that these materials can be used for ultrafast all-optical switching. Sb-Ge-S glasses were characterized using a laser operating at 1560 nm with 65 fs pulses and 50 MHz of repetition rate. Due to the high repetition rate, the nonlinear optical properties were determined using the thermal managed z-scan. Values of n2 S10-13 cm2/W were measured and FOM values were estimated. The results indicate that these materials are good candidates for photonic applications. In the colloids case, colloids with nickel oxide and silver nanoparticles were studied using a Nd:YAG laser at 532 nm with pulses of 80 picoseconds. From the results it was calculated the nonlinear susceptibility of the particles using the Maxwell-Garnett model. For the NiO colloid in toluene it was determined a high nonlinear refraction index (10-13 â 10-12 cm2/W) and negligible nonlinear absorption for filling factors of 10-7 â 10-8. The influence of stabilizing agents and the solvent on the linear and nonlinear optical properties were studied in silver colloids. The expression for the extinction coefficient from the Mie Theory was fitted to the absorption spectra using the scattering parameter A. Different values of A were obtained and its relation with the nonlinear optical properties is discussed. The nonlinear results show that stabilizing agents and the solvent can change the susceptibility by S100% and S300%, respectively

ASSUNTO(S)

nanoparticles glasses fisica vidros colÃides antimony silver z-scan colloids Ãxido de nÃquel nonlinear optics Ãptica nÃo linear nickel oxide nanopartÃculas prata varredura z antimÃnio

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