Phase-modulation instability of passive mode locking of solid-state lasers with a noninstantaneous-response saturable absorber

It is shown that when laser modes are locked by noninstantaneous nonlinear losses, a phase-modulation instability in generation of a single steady pulse (resulting from the nonlinearity of the refractive index of the intracavity medium) leads to the appearance of a regular time-periodic spatial structure of the generated pulse. An increase in the refractive index nonlinearity complicates the spatial structure of the radiation established in the lasing regime after the transient process, so that the time dependence of the structure ceases to be periodic and becomes chaotic.