Dynamics of longitudinal modes in a ring laser

A space–time approach is used to make a theoretical analysis of the dynamics of a multimode traveling-wave ring laser with a homogeneously broadened active medium. It is found that there are two frequency branches with different instability mechanisms. The conditions for transition of the system from one longitudinal mode to another are determined, as are the conditions for multimode stimulated emission with stable rf pulsations and more complex laser dynamics as far as randomization. Analytic expressions are derived to describe the profile of an envelope of stable short radiation pulses. Bistable states of the system are observed.