SELF-PULSING AND INSTABILITIES IN A UNIDIRECTIONAL RING DYE-LASER WITH INTRACAVITY FREQUENCY-SHIFT

We study the dynamics of a ring dye laser that contains a frequency shifting intracavity element as well as a bandwidth limiting filter. The laser emits a train of pulses with a repetition rate corresponding to K pulses per cavity round trip. The integer number K increases with increasing pump power P. The transition K <-> K + 1 exhibits a pronounced hysteresis as P is changed. Numerical simulations show that this behaviour of a dye laser with intracavity frequency shift results from a characteristic time variation of the instantaneous frequency which is converted into time dependent losses by the intracavity etalon. The pulsed operation at a given K is sustained by the concerted action of these frequency dependent: losses and the nonlinear coupling between the photon number in the cavity and the inversion of the active medium.