Gigahertz Acoustic Spectroscopy by Micro-Brillouin Scattering

An interesting problem on condensed matter in pure and applied sciences is the understanding of vibration and relaxation dynamics in the gigahertz range, especially cooperative motions in nonequilibrium states. In this work, we review the progress in micro-Brillouin scattering spectroscopy (MBSS) for condensed matter. MBSS has been achieved by combining a tandem multipass Fabry–Perot interferometer and an optical microscope to probe the gigahertz dynamics in a microscopic area/sample. It provides the fundamental information on a variety of vibration and relaxation processes and elementary excitations related to the lattice instability of structural phase transitions of normal and relaxor ferroelectrics, nonequilibrium cooperative dynamics of liquid–glass transitions and the hydration dynamics of protein glass transitions. The most relevant studies on the various aspects of gigahertz dynamics are provided.