Stimulated Brillouin gain spectroscopy in a confined spatio-temporal domain (30 mu m, 170 ns)

The Brillouin gain spectrum of a test sample (liquid acetone at room temperature) on scales simultaneously confined in space (30 mu m) and time (170 ns) is reported. This is done using a pulsed stimulated Brillouin scattering gain spectrometer in a theta approximate to 90 degrees crossing beam configuration. After having identified and corrected for different sources of background signals, we obtained a Brillouin gain spectrum allowing an accurate measurement (MHz range) of the Brillouin frequency (few GHz). This is of interest for probing acoustic properties of transparent media subjected to repetitive fast transient phenomena on small length scales.