VUV Brillouin scattering from superpolished vitreous silica

Abstract

A previous inelastic UV scattering experiment on silica glass is reproduced using a high grade superpolished sample. In the pristine sample condition, surface scattering is not observable compared to Rayleigh scattering from the bulk. However, exposure to a fluence of the order of 100 J/cm$^2$ at photon energies slightly below the electronic gap generates observable surface damage. This occurs after a few hours illumination with the monochromatic spectrometer beam. No anomaly in the Brillouin linewidth was found up to an excitation energy of 7.8 eV.