Photonic crystal made by close packing SiO2 submicron spheres

Three-dimensional solid superstructures built with submicrometric SiO2 spheres ordered in a close packed arrangement are shown to behave as photonic crystals. Spheres are synthesised following the Stober-Fink-Bohn method. A close packed structure with a perfect short-range order (tens of microns) is then obtained by sedimentation, on suitable substrates. Specular reflectance of visible light is found to follow Bragg's law which indicates that these structures behave as photonic crystals. This work shows that the ordering of microparticles can be a method to build photonic bandgap materials. (C) 1997 Academic Press Limited.