Polarization-selective branching of stop gaps in three-dimensional photonic crystals

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 fee symmetry. Polarized reflectivity measurements indicate the presence of stop gap branching for TE polarization, which is absent for TM polarization until the Brewster angle at the K point. In contrast, stop gap branching is present for both TE and TM polarizations at the 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 the on-resonance wavelength as compared to the off-resonance along both K and W points, and that is in accordance with theory. Our results have implications in polarization-induced light scattering in subwavelength photonic structures such as plasmonic crystals, and metamaterials.