Anisotropy of weak light scattering in thin opal films

The forward and backward light scattering that accompanied the almost ballistic light propagation in opal-based three-dimensional photonic crystal (PhC) has been experimentally studied. The light path memory and the high anisotropy of scattering have been associated with low-order scattering at large-scale crystal defects. The strong backscattered light intensity has been linked to the uncoupled light at a PhC surface. The exponent of power-law approximation of angle diagrams of the scattered light intensity has been suggested as a measure of the scattering anisotropy. The scattering anisotropy spectra have demonstrated that in a vicinity to the first photonic bandgap, the lower directionality of the forward scattering is complemented by the higher directionality of the backward scattering