Stimulated Brillouin scattering interactions in optical fibers involve the exchange of energy and linear momentum between the optical and acoustic fields. In most settings, the angular momenta of the two fields remain unchanged. In this presentation, I discuss the vector properties of forward stimulated Brillouin scattering processes in standard, single-mode fibers. The process make take place through guided acoustic modes of two-fold azimuthal symmetry, which appear in degenerate pairs. Analysis shows that a pair of optical pump waves, with circular and orthogonal polarizations, may stimulate a superposition the pair of acoustic modes. That superposition takes up the form of a rotating acoustic vortex beam. The stimulation process is associated with the transfer of angular momentum quanta between the optical and acoustic fields. This type of interaction adds a new dimension to stimulated Brillouin scattering processes in fibers.
|