Effect of a selective saturable absorber on the dynamics of a two-mode laser

The dynamics of a two-mode laser is studied in the presence of a selective saturable absorber interacting only with one of the modes. The specific nature of the system is determined by the presence of the out-of-phase relaxation oscillation, which becomes undamped when a sufficiently dense saturable absorber interacts with the weaker mode. If the absorber interacts with the stronger mode, the in-phase relaxation oscillation is excited, and the situation becomes similar to that observed in a single-mode laser. In the case of a slowly relaxing absorber, the difference of populations of its working levels can be adiabatically excluded. This procedure substantially simplifies the model and does not change its dynamic characteristics.