Plasmonic effects and visible light diffraction in three-dimensional opal-metal photonic crystals

The angular dependence of the reflectivity spectrum for visible light was measured in opal-metal (Ag and W) composites with a high filling factor. The diffraction patterns were observed at a wavelength essentially exceeding the period of a three-dimensional photonic structure. The authors offer a qualitative explanation based on the similarity between the experimental observations and those modified by the three-dimensional periodicity plasmonic effects in two-dimensional periodic structures with a subwavelength defect.