Suppression of multiple scattered light by photon cross-correlation in a 3D experiment

Abstract

In strongly scattering media, the presence of multiple scattered light prevents the straight-forward interpretation of photon-auto correlation functions in terms of single scattering processes. In order to suppress the influence of multiple scattering Schätzel suggested a socalled 3-D cross-correlation technique. This technique operates by cross-correlating the intensities of the scattered light of two coherent laser beams illuminating the same scattering volume and so defining two scattering geometries. The cross-correlation function is identical to the auto-correlation function from single scattering if the scattering vector q is chosen to be identical for both scattering geometries. Based on this idea an experimental set-up has been developed, which appears to be a fairly simple modification of a conventional light scattering experiment. Test measurements with solutions of standard latex particles with a diameter of 109 nm at various concentrations show, that contributions due to multiple scattering are well suppressed even in the range of strong multiple scattering.