Role of a "soundguide" and "antisoundguide" in stimulated Brillouin scattering in a single-mode waveguide

An analysis is made of steady-state stimulated Brillouin scattering (STBS) in planar and cylindrical single-mode waveguides taking into account sound diffraction and refraction in a given transverse sound velocity profile ("soundguide" and "antisoundguide"). For a strong soundguide the STBS line has the same width and Lorentzian profile, the intensity being slightly attenuated compared with STBS of plane waves in an unbounded medium. For a strong antisoundguide the sound is "expelled," the attenuation length becomes of the order of the sound diffraction length, so that the STBS line is substantially broadened, attenuated, and becomes asymmetric.