Backscattering enhancement of light and multiple scattering of surface waves at a randomly varying impedance plane

Abstract

The scattering of p- or s-polarized plane waves incident upon flat surfaces characterized by a randomly varying impedance is studied. The impedance is considered to be one dimensional, i.e., to vary along one of the two coordinates on the surface. Particular attention is paid to the role played by multiple scattering of surface waves in the production of enhanced backscattering at this kind of structure and its relation with the backscatter peak observed in metallic surfaces with height variations. The angular distribution of the scattered field is calculated for different realizations of the same statistical ensemble of impedance variations. A peak in the retroreflection direction is observed in p polarization for an inductive impedance and in s polarization for a capacitive impedance. The peak is clearly distinguished in the double-scattering contribution, but it is also present in higher-order multiple-scattering terms. It is shown that the observation of enhanced backscattering at these structures is always associated with the excitation of surface electromagnetic waves along the scatterer. An analogy between randomly varying impedance planes and actual corrugated surfaces is discussed.