Enhanced backscattering in a converging-beam configuration.

Enhanced backscattering (EBS) is investigated for a converging-beam geometry. We find that the functional form of the enhanced backscattering cone is preserved under a change of variables that involves the focal length of the lens and the lens-to-sample distance. In absolute terms, the effect of the lens is that the EBS enhancement cone is lowered in magnitude and narrowed in angle. The experimental data show good agreement with the theory presented, even for tightly focused beams, as long as the illuminated area is larger than the transport mean free path for the random medium.