Laser-induced modification of bulk fused silica by femtosecond pulses

The features of the local nondestructive modifications of the bulk fused silica are experimentally studied. A method for the measurement of the refractive index in a transparent sample irradiated with femtosecond laser pulses is developed. The accuracy of the refractive-index measurements achieves about 10−5, and a spatial resolution is several microns. The quantitative data on the dynamics of the permanent modification of glass as a function of the radiation energy are obtained for the first time. The spatial localization of the modified area that is predominantly determined by the laser-beam divergence is analyzed. The femtosecond interferometry is used to investigate the laser-pulse propagation in amorphous silica.