Scattering of electromagnetic waves from a bounded medium with a random surface

By small-amplitude perturbation theory and by a computer-simulation approach we have studied the incoherent scattering of electromagnetic waves from a randomly rough, dielectric film deposited on a planar, perfectly conducting surface. The thickness of the dielectric film is such that in the absence of the roughness the scattering system supports two guided waves. As a consequence, each multiply scattered wave is now degenerate. The coherent interference of each of these degenerate waves with the waves obtained from them by time reversal produces two satellite peaks in the angular dependence of the intensity of the incoherent component of the scattered field, in addition to the enhanced backscattering peak. These satellite peaks occur at scattering angles ${\mathrm{\theta }}_{\mathit{s}}$ that are related to the angle of incidence ${\mathrm{\theta }}_0$ by sin${\mathrm{\theta }}_{\mathit{s}}$=-sin${\mathrm{\theta }}_0$±(c/ω)[${\mathit{q}}_1$(ω)-${\mathit{q}}_2$(ω)], where ${\mathit{q}}_1$(ω) and ${\mathit{q}}_2$(ω) are the wave numbers of the two guided waves supported by the scattering system at the frequency ω of the incident field. These peaks are present in the results of both the perturbation and simulation calculations. They are shown to be multiple-scattering effects, and not a single-scattering phenomenon.