"Slow Light" in stimulated Brillouin scattering: on the influence of the spectral width of pump radiation on the group index.

An analytical solution of the basic coupled stimulated Brillouin scattering (SBS) equations is obtained in the Fourier domain, which describes the spectral evolution of the medium's response, and that of a Stokes pulse injected into this medium, when SBS is excited by non-monochromatic CW pump radiation. It shows that spectral broadening of pump radiation by any reasonable amount results in only minute increase of the spectral width of the resonant material's excitation in SBS, and cannot be effective in modifying the natural group index of the medium for the Stokes pulse.