Dynamics of a single-mode laser with an additional mirror

A control equation is derived that describes the dynamics of a laser with a low-reflecting additional mirror, which can be located both outside and inside the laser cavity. The latter variant is implemented, in particular, in the case of parasitic intracavity reflections of laser radiation. For class B lasers (solid-state or semiconductor), the conditions for the instability of the stationary regime due to the buildup of relaxation oscillations are determined.