INTRINSIC OPTICAL BISTABILITY AND RESONANCES IN NONLINEAR COMPOSITES

Optical bistability can be achieved in composite materials made of a nonlinear dielectric and a metal of which the dielectric constant has a negative real part and a small imaginary part. We propose a general framework that enables us to investigate the bistable behavior of such two-component composites. It is based on a relation between the electric field in the nonlinear component and the external applied electric field. The bistable behavior is strongly connected to the existence of sharp resonances in this relation in which the local field is greatly enhanced above its mean value. In the vicinity of such resonances, bistability can be achieved even when the nonlinear behavior is weak. This relation between the fields is exact in composites in which the field in the nonlinear component is constant and thus allows exact treatment of some microgeometries. The conditions for bistable behavior in a few three component composites are also investigated. It is found that the threshold field required for bistable behavior in them is much lower than in two component composites.