Influence of self-focusing on the stability of steady-state laser emission

An investigation is made of the stability of steady-state laser emission in the case when the resonator contains a lens whose focal length is a function of the field amplitude. Fast perturbations (with characteristic frequencies of the order of the intermode beat frequency) are considered. The amount of nonlinear matter in the resonator needed to produce an instability is determined. Fast perturbations require much less nonlinear matter than the slow perturbations discussed earlier.