Optical studies of metal-infiltrated opal photonic crystals

We have studied the optical properties of metal infiltrated opal photonic c rystals and metallic replicas made of Sb, Hg, Bi and Pb. We observed dramat ic differences in the reflectivity spectra of two kinds of metallic structu res, namely those with either network or cermet topologies. We found that a ll metallic photonic crystals have Bragg stop bands in the visible spectral range. Highly interconnected metallic photonic crystal structures, however , showed about one order of magnitude decrease in the effective plasma freq uency compared to that of the bulk metals. Coherent backscattering measurem ents showed a much larger optical mean free path for the metal-infiltrated opals compared to the skin depth of the metals, in agreement. with the redu ction in the plasma frequency. We also found an extra band in the reflectiv ity spectra of network-type samples that is related to surface plasmons. A theoretical model that considers the metallic mesh inside the opal as a cub ic wire network agrees well with the experimental results. (C) 2001 Elsevie r Science B.V. All rights reserved.