Enhanced backscattering from a free-standing 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 enhanced backscattering peak. Because of difficulty in the fabrication of 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 experimental results showing enhanced backscattering from a free-standing dielectric film and compare them with the results of numerical simulations of such scattering. The vacuum-dielectric interface is a one-dimensional, randomly rough surface, and the dielectric-vacuum interface is approximately planar.The results of the numerical simulations of scattering from a one-dimensional, randomly rough free-standing dielectric film are in qualitative agreement with the experimental data, and it is believed that the main mechanism responsible for the enhanced backscattering peak is the reflection from the flat dielectric-vacuum interface. The coherent addition of a given light path that interacts with the rough dielectric surface at two different points because of its partial reflection from the back surface and its time-reversed partner leads to an enhancement of the intensity of scattering in the retroreflection direction with respect to the intensity of scattering in other directions.