Enhanced backscattering from a rough dielectric film on a reflecting substrate

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Abstract
We carry out computer simulations of the scattering of a beam of light with p or s polarization from a transparent dielectric film (BaSO4) on a perfectly conducting substrate. The dielectric–vacuum interface is assumed to be a random grating; the dielectric–conductor interface is assumed to be planar. It is found that for incident light of either polarization the angular dependence of the incoherent contribution to the mean intensity of the scattered light has a well-defined peak when the scattering angle corresponds to the retroreflection direction (enhanced backscattering). The existence of enhanced backscattering of p-polarized light in this geometry contrasts with its absence in the scattering of p-polarized light from a random grating on a semi-infinite dielectric medium that is characterized by the same roughness parameters and index of refraction. The enhanced backscattering that is observed in the scattering of s-polarized light from a random grating on a semi-infinite dielectric medium is stronger when the scattering takes place from the structure studied. For both polarizations the enhancement is most pronounced when the distance of the perfectly conducting substrate from the mean dielectric–vacuum interface is several (2–10) times the distance of the focusing plane of the rough interface from the mean interface.