Parametric-feedback stimulated Brillouin lasers

An experimental investigation was made of stimulated emission from stimulated Brillouin scattering (STBS) lasers in which one of the mirrors was of the self-pumped parametric type. The lasing threshold of a ring laser was found to be five times less than that of the conventional backward STBS. The duration of the linear stage of the development of lasing was measured for various values of the excess above the threshold and for different resonator lengths. Even when the resonator length was characterized by a Fresnel number ~ 1, the divergence of the radiation generated by a parametric laser was 1.5 times higher than the divergence of the pump radiation. The pump conversion efficiency was estimated theoretically for the steady-state operation. The theoretical dependence of the reflection coefficient on the pump intensity was confirmed experimentally. A phase conjugation method with a high energy efficiency was proposed and implemented.