Stochastic and Deterministic Fluctuations in Stimulated Brillouin Scattering.

摘要

The dynamical behavior of stimulated Brillouin scattering (SBS) under a variety of conditions is investigated both theoretically and experimentally. Under conditions of a single continuous-wave laser field, the initiation of the SBS process is treated by including the thermal fluctuations of the material density which lead to spontaneous Brillouin scattering. Predictions are made for the threshold of the Stokes light. The spectrum of the output Stokes light is predicted to exhibit gain-narrowing as the input laser intensity is increased. Under certain conditions, the Stokes output intensity is expected to exhibit nearly 100% fluctuations even far above the threshold for SBS. Experiments performed in a single-mode optical fiber verify many of the predictions of the theory. Stimulated Brillouin scattering in the presence of two counterpropagating laser beams is studied. Under these conditions, the laser beams become temporally unstable to the growth of Stokes and anti-Stokes light. For the case when the input intensities of the two waves are comparable, the threshold for instability can be significantly lower than he threshold for usual single-beam SBS and, for the case of a broad Brillouin line, the system can show a period-doubling route to chaos. This Brillouin instability was observed experimentally using carbon disulfide as the Brillouin-active material.