Electromagnetic response of systems with spatial fluctuations. I. General formalism

Abstract

We obtain closed-form expressions for the macroscopic dielectric response of systems with spatial fluctuations, taking into account the local-field effect. The macroscopic response is written, without reference to any specific representation, in terms of the microscopic dielectric operator and the projection operators that extract the average and the fluctuation components of the microscopic fields. The results are very general since few assumptions are made about the nature of the system and of its microscopic response, and very relaxed conditions are imposed on the average and fluctuation projectors. We put special emphasis on systems for which the length scale of the fluctuations is much smaller than the wavelength of light.