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 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.