Observation of Bragg reflection in photonic crystals synthesized from air spheres in a titania matrix

Three-dimensional photonic crystals made of close-packed air spheres in an interconnected titania matrix have been fabricated using a self-organized t emplate of polystyrene microspheres of 400 nm diameter. The matrix was obta ined by vacuum-assisted infiltration of a precursor, with subsequent remova l of the microspheres by calcination. Electron microscopy has confirmed the ordering of the structure and the presence of features likely to enlarge t he photonic band gap. The reflection spectra of the crystal measured at dif ferent angles of incidence are consistent with Bragg's law and with theoret ical calculations, confirming the photonic nature of the material. (C) 2000 American Institute of Physics. [S0003-6951(00)04914-7].