High-resolution Brillouin gain spectroscopy in fused silica

We report what is to our knowledge the first high-resolution Brillouin gain spectrum in a solid. Resonances corresponding to longitudinal (compressional) and transverse (shear) acoustic waves in fused silica are observed with good resolution and a high signal-to-noise ratio. Absolute gain coefficients, linewidths, and Brillouin frequency shifts are measured. The agreement with previously measured values is good.