Conditions of bistability in large-aperture optical systems

An analysis is made of the limits of validity of a description of large-aperture bistable systems on the basis of a theory of plane waves. The limitations arise because of transverse effects. The results show that instabilities of the transverse structure of the field in nonlinear interferometers can be suppressed effectively by using resonators with an expanding beam. The possibility of a low-threshold bistability in nonlinear reflection systems with two incident beams is discussed.