  We study the direction- and wavelength-dependent polarization anisotropy in
light scattering at the air-photonic crystal interface as a function of angle
of incidence for TE and TM polarized light. This is done using optical
reflectivity measurements at high-symmetry points in the Brillouin zone of a
three-dimensional photonic crystal with fcc symmetry. Polarized reflectivity
measurements indicate the presence of stop gap branching for TE polarization,
which is absent for TM polarization till the Brewster angle at K point. In
contrast, stop gap branching is present for both TE and TM polarizations at W
point due to the intricate mixing of crystal planes. This characteristic
behavior signifies the inevitable role of energy exchange in the stop gap
branching. The measured polarization anisotropy shows a prominent shift in the
Brewster angle for on-resonance wavelength as compared to the off-resonance
along both K and W points, and that, in accordance with theory. Our results
have implications in polarization-induced light scattering in sub-wavelength
photonic structures like plasmonic crystals, and meta-materials.
