High-resolution low-level Brillouin spectroscopy in solids

In this paper some of the experimental considerations for obtaining phonon attenuation in solids by Brillouin scattering are described. Measurements of room temperature damping of longitudinal hypersonic waves in α-quartz, fused silica, and calcium fluoride are reported. The observed phonon frequency and linewidth for backward scattering of 6328-Å light in these solids is typically ∼ 30 GHz and ∼ 30 MHz (FWHM), respectively. This corresponds to a damping length of
\sim 60 \mu
, which is inaccessible by conventional ultrasonics techniques.