Influence of a nonlinear lens on the stability of steady-state laser emission

The problem of stability of steady-state laser emission is considered for the case in which the resonator contains a medium whose refractive index is a function of the radiation intensity. It is shown that the instability threshold decreases as the diffraction losses increase. This threshold is derived for the cases when a nonlinear instantaneous-response dielectric or the active substance itself acts as the nonlinear medium.