Experimental evidence of polarization dependence in the optical response of opal-based photonic crystals

We report angle resolved reflectivity measurements showing the polarization dependence of the pseudogap in artificial opals. This kind of photonic crystals consist of silica spheres ordered in a face-centered-cubic lattice. The analyzed gap originates from the (111) family of planes. It is shown that the width of the Bragg peak observed in the reflectance spectra follows the bands determining the pseudogap, which are selectively excited according to the polarization (s or p) of the light impinging on the opal. Moreover, it is found that the coupling of light with the photonic bands occurs according to their predicted symmetry, which was assigned by arguments based on group theory.