THREE-DIMENSIONAL SIMULATIONS OF STIMULATED BRILLOUIN SCATTERING WITH FOCUSED GAUSSIAN BEAMS

Abstract

We report on a detailed investigation of the process of SBS with focused Gaussian beams via a three-dimensional simulation of the SBS process that includes spontaneous noise. We show that spontaneous noise present at points other than where the initiation of SBS occurs does not significantly affect the Stokes wave. The effects on the Stokes beam of modes not present in the pump wave (nonconjugate modes) are investigated and it is found that the phase of a given Stokes mode is affected by the presence of other modes, a process termed phase pulling. We also show that for a focused Gaussian beam the Brillouin gain parameter does not increase linearly with increased pump power once SBS threshold is reached; rather, above threshold the SBS process resembles a reverse saturable absorber for the pump wave at any point. between the entrance to the medium and the focal point of the pump beam.