EFFECTIVE DIELECTRIC RESPONSE OF NONLINEAR COMPOSITES

A perturbative approach is developed to compute the local field for th e case of a nonlinear inclusion embedded in a nonlinear host. The resu lt is applied to nonlinear composites. General formulas for calculatin g the effective nonlinear susceptibility up to the case of fifth-order nonlinearity are given. The formulation is applied to problems in two dimensions (2D) and in three dimensions (3D). For 2D problems, the ca ses of cylindrical inclusions and concentric cylindrical inclusions ar e studied. By invoking an exact mapping, the problem of the concentric cylinder can be mapped onto the problem of an elliptic cylinder. A ge neral expression of the effective nonlinear susceptibility for a dilut e composite of randomly oriented elliptic cylinders embedded in a line ar host is derived. For 3D problems, the cases of spherical inclusions and coated spherical inclusion are studied. General expressions for t he effective nonlinear susceptibility are given in the dilute limit up to the case of fifth-order nonlinearity. For composites consisting of spherical inclusions coated by a nonlinear material and embedded in l inear host, it is possible to enhance the nonlinear response of the co mposite by tuning material parameters such as the linear dielectric co nstants of the host, coating and core materials, and by adjusting the thickness of the coating.