Beam-coupling by stimulated Brillouin scattering

A theoretical/experimental study of beam coupling by stimulated Brillouin scattering (SBS) is reported. The theoretical work examines the build-up, transient through steady-state, of two SBS beams excited by partially overlapped pump-beams and is directed toward understanding how two output SBS beams are coupled together. Experimental work reports measurements of the mutual coherence of the two Stokes beams as a function of the relative intensity, overlap and polarizations of the pump beams. The experimental work verifies the key theoretical result that four-wave mixing is responsible for beam coupling and for the establishment of the mutual coherence of the two Stokes beams.