Stochastic Approach to Undamped Spiking of Lasers

Abstract

We study the phenomenon of undamped spiking of lasers from the viewpoint of an example of the hard-mode instability in a nonlinear and off-equilibrium system on the basis of a stochastic model. We interpret this phenomenon as the repetitive Q-switching and adopt the model presented by Shimoda or Hofelich and Hofelich, considering the saturable absorber as a structureless sink of photons. The analysis of this model is carried out by means of the system size expansion. We found that the spiking instability is associated with the anomalous enhancement in the irreversible circulation of fluctuation which leads to the emergence of a limit cycle. It is also found that the character of transition between the stationary lasing and the spiking oscillation can be continuous or discontinuous, depending on parameters.