Bifurcations and stochasticity induced by an external noise in a laser with a nonlinear absorber

A numerical investigation is reported of a five-dimensional dynamic system describing a laser (specifically a CO₂ laser) with a nonlinear absorber (in the form of a CO₂ cell). Two regions of periodic modulation of the Q factor are found at low and high pressures of the absorbing gas. The laws describing the behavior of the characteristics of a sequence of pulses are based on the general theory of bifurcations and of propagation of short light pulses in amplifying and absorbing media. A mechanism in which an external noise causes stochastization of spontaneous fluctuations is identified and the conditions under which this can occur are investigated.