High pressure angle-dispersive Brillouin spectroscopy: A technique for determining acoustic velocities and attenuations in liquids and solids

We report the combination of a high-pressure sample chamber and a stable, nonscanning, angle-dispersive Fabry–Perot interferometer allowing the rapid measurement of inelastic light scattering from acoustic phonon modes in solid and liquid samples at high pressure. The primary components of the apparatus are a (i) narrow frequency gas ion laser, (ii) a solid or air-spaced etalon, (iii) a multichannel charge coupled device detector, and (iv) a large volume, high-pressure cell. The fundamental principle of this spectrometer is based on the angular dispersion of light through an etalon, whereupon the multiple-order frequency dispersed spectrum can be acquired with an array detector. Typical acquisition times are less than 1 s using low to moderate laser power.