Instabilities in a solid-state ring laser

In addition to a well-known type, two more types of relaxation oscillation are present in a solid-state ring laser. The frequencies of these specific oscillations depend on the difference in the eigenfrequencies of counterpropagating resonator modes (phase nonreciprocity). There are instability mechanisms that can convert these relaxation oscillations into undamped pulsations. The instability is responsible for the possibility of detecting low-frequency oscillation characteristic of a ring laser. In our experiment these oscillations are represented by resonant features in the intensity-fluctuation spectrum of a Nd:YAG laser operating in a stable traveling-wave regime although close to a self-modulation instability threshold.