Self-Pulsing in Lasers

The origin of pulse formation in lasers is investigated. The main features of this phonomenon are explained in terms of a homogeneously broadened, two-level ring laser model. First, it is found that a stationary (cw) solution cannot exist for certain choices of laser parameters. By a numerical integration of the laser equations, it is shown next that a buildup of a pulse occurs for these parameters. The final (steady-state) pulse shape and its velocity are determined. Furthermore, it is found that a multistable operation is possible. A simple approximate equation is derived, by which most of the features of the final pulse are given analytically.