Solid-state ring laser with a nonlinear absorber

Theoretical and experimental investigations were made of the feasibility of controlling the amplitude and frequency characteristics of a YAG:Nd³⁺ ring laser by self-diffraction of opposite (counterpropagating) light waves on gratings of the absorption coefficient and refractive index induced in nonlinear absorbers. These absorbers were unpumped YAG:N³⁺ crystals or crystals of LiF containing F₂^– centers. It was established that in the absence of an offset between the centers of the gain and absorption lines the competition between the opposite waves in the ring laser was reduced. In the presence of an offset an amplitude nonreciprocity was observed and it was proportional to the difference between the frequencies of the opposite waves. However, when fast-response nonlinear absorbers were used, suppression of one of the opposite waves could be weak even in the case of a large offset. The distortions of the amplitude and frequency characteristics of a rotating ring laser were shown to be small in the presence of nonlinear absorbers with a short relaxation time and a low initial absorption coefficient.