Transient evolution and steady-state emission from passively mode-locked lasers

An analytic determination is made of the direction of evolution of a field in a laser with an instantaneous-response saturable absorber and with a gain which follows changes in the average (over the axial period) intensity. It is shown that in the case of mode locking a laser system goes over, irrespective of the initial conditions, to a regime of steady-state emission of one pulse per axial period.