SCATTERING OF LIGHT FROM A ROUGH DIELECTRIC FILM ON A REFLECTING SUBSTRATE - DIFFUSE FRINGES

The scattering of light from a one-dimensional randomly rough dielectr ic film deposited on a flat reflecting substrate is studied by means o f a small-amplitude perturbation theory and rigorous numerical simulat ions. In particular, we study the appearance of well-defined fringes i n the angular distribution of the diffusely scattered intensity and th eir dependence on the angle of incidence, the roughness of the film, a nd the film's mean thickness. We find that, for slightly rough films, the angle of incidence modulates the intensity of the fringes but has no effect on their angular position. For rougher films the contrast of the pattern decreases, and the fringes move with the angle of inciden ce in such a way that there are always bright fringes in the specular and backscattering directions. Eventually, for very rough films, the f ringe pattern disappears, and a well-defined backscattering peak emerg es in the retroreflection direction. (C) 1998 Optical Society of Ameri ca.