Hypersound damping in vitreous silica measured by picosecond acoustics

TL;DR

This study measures high-frequency sound damping in vitreous silica using picosecond acoustics, revealing damping behavior consistent with anharmonic relaxation and challenging recent claims of rapid damping increase beyond 100 GHz.

Contribution

It provides the first detailed measurement of hypersound damping near 250 GHz in vitreous silica, clarifying the damping mechanisms and extending previous optical Brillouin scattering data.

Findings

Sound damping at 250 GHz aligns with anharmonic relaxation models.

Contradicts recent deep-UV experiment claiming rapid damping increase beyond 100 GHz.

Proposes a comprehensive frequency-dependent damping profile for vitreous silica.

Abstract

The attenuation of longitudinal acoustic phonons up to frequencies nearing 250 GHz is measured in vitreous silica with a picosecond optical technique. Taking advantage of interferences on the probe beam, difficulties encountered in early pioneering experiments are alleviated. Sound damping at 250 GHz and room temperature is consistent with relaxation dominated by anharmonic interactions with the thermal bath, extending optical Brillouin scattering data. Our result is at variance with claims of a recent deep-UV experiment which reported a rapid damping increase beyond 100 GHz. A comprehensive picture of the frequency dependence of sound attenuation in $v$-SiO$_2$ can be proposed.