Optical study of ΓL high energy photonic pseudogaps in ZnO inverted opals

We provide experimental evidence of the opening of two new pseudogaps in the high energy region of the Gamma L direction in ZnO inverted opals. The appearance of these new pseudogaps is brought about by the increase of refractive index contrast. The calculated band diagram in the Gamma L direction, which corresponds to propagation along the (111) crystallographic direction, accounts for the spectral width and position dependence of the pseudogaps on the ZnO fraction present in the opal. To prove this we have performed an optical study by means of reflection and transmission spectroscopy of ZnO inverted opals with different degrees of infiltration. We also study the pseudogap appearing in the highest energy spectral position as a function of sample thickness. In addition, the band engineering developed here allows us to isolate a nondispersive band from the others. (c) 2006 American Institute of Physics.