A review of stimulated Brillouin scattering excited with a broad-band pump laser

Stimulated Brillouin scattering (SBS) excited by a pump laser with a bandwidth large compared to the Brillouin linewidth is reviewed. SBS amplifier results show that either for low gain or for short pulses, the broad-band SBS gain is substantially lower than the steady-state gain. In the high gain limit, however, the fast phase fluctuations that are typical of a broad-band pump have a small effect on amplifier gain. Results for SBS that grows from noise show that fast pump phase fluctuations affect the gain only under two conditions. The first is when the coherence length of the pump is shorter than the gain length in the SBS medium. The second is when the pump is made up of two or more temporal modes separated by more than the SBS linewidth and aberrated with independent spatial profiles. In this case, the quality of wavefront inversion may be badly degraded as well. Areas for further work, including competing nonlinearities, are discussed.