Mechanisms of the refractive index change in femtosecond laser-irradiated Au3+-doped silicate glasses.

We report on the refractive index change in Au3+-doped silicate glasses irradiated by a femtosecond laser and successive heat treatment. The refractive index of the irradiated area increased after the femtosecond laser irradiation and decreased with increasing annealing temperature up to 450 °C and then increased again with increasing annealing temperature. Absorption spectra of the glass samples before and after femtosecond laser irradiation and after further annealing manifested the formation of color centers after laser irradiation, disappearance of color centers after annealing at 300 °C, and precipitation of gold nanoparticles after annealing at high temperature. The mechanisms of the observed phenomena are discussed. [ABSTRACT FROM AUTHOR]