Near-field Brillouin scattering as a probe of low-frequency dynamics at an interface

Brillouin scattering is known to offer important information on the low-frequency dynamics of bulk materials such as sound wave propagation and cooperative fluctuation. It is expected to give the dynamical properties at an interface, which are difficult to obtain by usual spectroscopic tools. Under near-field excitation, however, the Brillouin spectra often undergo the considerable deformation due to the discontinuous structure of the interface. We have shown from experimental and theoretical studies that its spectral shape is largely affected by the scattering geometry and under an appropriate geometry, dynamical and structural information at an interface are clearly discernible, which promises us the development of this spectroscopy as a valuable probe of interface dynamics.