Opal films 8 Artificial opals 4 Group velocities 4 High energy physics 4 High-energy range 4 KKR method 4 Lattice parameters 4 Light velocity 4 Light wavelengths 4 Optical response 4 Photonic crystals 4 Photonic devices 4 Photonic nanostructures 4 Spectral range 4 Superluminal 4 Three dimensional 4 Anomalous behavior 2 Close-packed planes 2 Colloids 2 Crystal size 2 Crystal structure 2 Crystal thickness 2 Crystalline structure 2 Defects 2 Design of experiments 2 Dielectric spheres 2 Diffraction 2 Direct identifications 2 Dispersion modes 2 Dynamics 2