The threshold for second-order stimulated Brillouin scattering (SBS) in a fiber has been investigated; the study was motivated, in part, by the need to determine the operational dynamic range of SBS fiber beam combiners. Theoretical analysis showed that the second-order Stokes threshold is approximately 130 times the first-order threshold. Experimentally, however, the threshold was found to be only 15 times greater. This dramatic reduction in threshold was determined to be due to the generation of second-order Stokes photons through four-wave mixing, which in turn seeds the second-order SBS process. Suppression of internal Fresnel reflection at the front fiber facet can help to restore the threshold to the higher value.
© 2002 Optical Society of America
(140.3300) Lasers and laser optics : Laser beam shaping
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(230.4320) Optical devices : Nonlinear optical devices
(290.5900) Scattering : Scattering, stimulated Brillouin
Timothy H. Russell and Won B. Roh, "Threshold of second-order stimulated Brillouin scattering in optical fiber," J. Opt. Soc. Am. B 19, 2341-2345 (2002)