Tuning and optical study of the $ΓX$ and $ΓL$ photonic pseudogaps in opals Available to Purchase

In this letter we demonstrate a method to tune and optically investigate the two highest-symmetry pseudogaps in artificial opals which occur at the $L$ an $X$ points of the Brillouin zone and correspond to propagation along the (111) and (100) crystallographic directions, respectively. In particular we show that in artificial opals the gap at the $X$ point, which is closed for bare opals, can be opened by controlled infiltration with a high refractive index material such as ZnO. To prove this we take advantage of the fact that, in artificial opals grown by the vertical deposition method, regions with both (100) and (111) orientations of the face centerd cubic lattice occur naturally.