Q-switching bifurcation in a laser with a saturable absorber

The passive Q-switching operation in a laser with a saturable absorber consists of an operation with high-intensity spikes in the output power. It is known that this particular regime corresponds mathematically to a large-amplitude time-periodic solution of the laser equations. In this paper we propose a new asymptotic method to construct this solution. We show how the time-periodic solution appears from an infinite-period solution (homo-clinic solution) and analyze the behavior of the maximum intensity and the period as a function of a control parameter. This asymptotic method is based on a recent evaluation of the parameters for CO2 lasers with different absorbers [ E. Arimondo F. Casagrande L. A. Lugiato P. Glorieux , Appl. Phys. B30, 57 ( 1983)]. The relative magnitudes obtained by Arimondo et al. suggest a new approximation of the laser equations.