Instabilities in a single-frequency solid-state ring laser and regenerative amplification of noise

An investigation is reported of the influence of the amplitude and phase nonreciprocities of a resonator on low-frequency characteristics of radiation emitted by a solid-state ring laser. It is shown that singularities of the spectrum of the intensity fluctuations, reflecting the existence of relaxation fluctuations specific to solid-state ring lasers, may be manifested only near the stability limit of steady-state lasing because of regenerative amplification of noise at the frequencies of these fluctuations. The asymmetry of the lasing characteristics of a YAG:Nd ring laser relative to the sign of the phase nonreciprocity is due to the existence of two active transitions with similar frequencies.