The spectrum of light scattered from acoustic waves has a form of a triplet, consisting of the central Rayleigh peak and two Brillouin peaks shifted from the frequency of the incident light by the frequency of acoustic wave in the medium. The Brillouin shift and the intensity of the Brillouin peaks are much smaller than the frequency and intensity of the incident light, respectively. Hence, they are difficult to determine experimentally.
We conduct self-consistent rigorous numerical simulations of nonlinear acoustic wave interaction in liquids and of light scattering from the fundamental and nonlinear generated waves. We demonstrate that the intensity of Brillouin peaks is strongly enhanced by an ultra-small plasmonic nanonatenna. We show that this enhancement can be used to generate Brillouin frequency combs with spectral components controlled by tuning the nonlinear acoustic interaction.