ENHANCED BACKSCATTERING FROM A FREESTANDING DIELECTRIC FILM

It has been known theoretically for a few years that not only a rough metallic surface but also a rough dielectric surface can produce an en hanced backscattering peak. Because of difficulty in the fabrication o f one- or two-dimensional rough dielectric surfaces with a high index of refraction, no experiments to date have been able to reveal such a peak in scattering from a rough dielectric surface. We present experim ental results showing enhanced backscattering from a free-standing die lectric film and compare them with the results of numerical simulation s of such scattering. The vacuum-dielectric interface is a one-dimensi onal, randomly rough surface, and the dielectric-vacuum interface is a pproximately planar. The results of the numerical simulations of scatt ering from a one-dimensional, randomly rough free-standing dielectric film are in qualitative agreement with the experimental data, and it i s believed that the main mechanism responsible for the enhanced backsc attering peak is the reflection from the flat dielectric-vacuum interf ace. The coherent addition of a given light path that interacts with t he rough dielectric surface at two different points because of its par tial reflection from the back surface and its time-reversed partner le ads to an enhancement of the intensity of scattering in the retrorefle ction direction with respect to the intensity of scattering in other d irections.