Spectral properties of opal-based photonic crystals having a SiO2 matrix

We study the transmission and reflection of electromagnetic waves propagati ng in bare opal photonic crystals. We find that the incomplete gap at the L point fully inhibits the transmission of waves propagating in the [111] di rection for opal sample thicknesses that are easily obtainable. This proper ty shows that bare opals could be good candidates for complete inhibition o f transmission in the near-infrared and visible frequency range for given o rientations. The dependence of the total reflectance on the angle of incide nce has been calculated, and a good agreement has been found with available experimental data. We have also analyzed the modification of the transmiss ion properties of bare opals induced by a sintering process. Our calculatio n predicts a linear decreasing of L-midgap frequency when the filling fract ion decreases due to sintering, which is also in accordance with experiment s. [S0163-1829(99)07239-2].