MEASUREMENT OF THE POWER DISTRIBUTION DURING STIMULATED BRILLOUIN-SCATTERING WITH FOCUSED GAUSSIAN BEAMS

We show both theoretically and experimentally that, when stimulated Br illouin scattering (SBS) is produced using focused Gaussian beams, the spatial extent of the pump depletion region changes significantly wit h the input power. We also show that the location of the SBS interacti on region depends on the ratio of the input power to the SBS threshold power. Only below and near SBS threshold is the interaction region la rgely located within several confocal parameters of the beam waist, as is often assumed in simplified treatments of the SBS process.