Opal-based photonic crystal with double photonic bandgap structure

The interior surfaces of one part of a piece of artificial opal have been c oated with GaP so that the remaining part of the opal crystal remains empty , thus forming a photonic heterostructure. Two Bragg resonances have been o bserved in the optical transmission and reflectance spectra. These two reso nances were found to behave differently with changes in the polarization of the incident light and the angle of propagation of the light with respect to the (111) planes of opal. Depolarization of the light was observed to oc cur most effectively at frequencies within the stop-bands, apparently due t o the re-coupling of the propagating electromagnetic wave to a different sy stem of eigenmodes when it crosses the interface separating two parts of th e double photonic crystal.