Nonlinear dielectric response of partially resonant composites

The dielectric response of a nonlinear composite system, which is composed of coated sphere particles with linear (or nonlinear) cores and linear shells randomly embedded in a linear host matrix, is studied, It is shown that under a partial resonance condition the linear system behaves as a mixture of the host matrix and equivalent solid spheres with the same dielectric function as the original cores and radii equal to those of the original coating shells. When the linear partial resonance condition is satisfied in the nonlinear system, the nonlinear dielectric susceptibility of the equivalent solid spheres is larger than that of the original nonlinear cores, although the linear parts of their dielectric functions are equal. Moreover, the electric field within those equivalent nonlinear solid spheres is larger than that in a mixture of these solid spheres. In partial resonance, these effects facilitate a great enhancement of the nonlinear response in such a composite system. However, the nonlinear partial resonance cannot be realized in a composite of coated spherical particles.