Possible coherent backscattering of lightwaves from a strongly absorbing nanoporous medium

Abstract

We report on anomalous light retroreflection from strongly absorbing nanoporous semiconductor materials, GaAs and InP, with strongly polarized retroreflected light with linear polarization coinciding with that of incident beams. The high polarization of retroreflected waves suggests coherent backscattering as the underlying physical mechanism. This phenomenon resulting from multiple scattering is supposed to be possible in an absorbing medium owing to longitudinal electromagnetic waves generated at interfaces. Strong absorption for transverse waves has negligible effect on longitudinal ones and therefore does not prevent their multiple scattering but ensures a high refraction index promoting strong scattering. This hypothesis is supported by a theoretical model and calculations.