VUV Brillouin scattering from superpolished vitreous silica

TL;DR

This study reproduces UV Brillouin scattering in superpolished vitreous silica, showing that surface damage occurs after high fluence exposure, but no linewidth anomalies are observed up to 7.8 eV.

Contribution

It demonstrates the effects of high-fluence UV exposure on superpolished silica and confirms the absence of linewidth anomalies up to 7.8 eV.

Findings

Surface scattering is negligible in pristine samples.

High fluence exposure causes surface damage.

No linewidth anomalies observed up to 7.8 eV.

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.