Polarization of near-forward-scattered light from particulate substrates illuminated at near-grazing angles

Laboratory photopolarimetric measurements of light scattered by substrates consisting of semitransparent particles with sizes significantly larger than the wavelength show a polarization shoulder at small scattering angles near θ=10-30° in addition to the Brewster maximum positioned near θ=50°. With ray-tracing simulations, we find that the shoulder appears to be related to light passing through particles in the upper layers of the substrates. We study the dependence on particle absorption and packing density of particulate substrates. The studies show that the shoulder weakens with increased absorption and packing density.