Photonic band engineering through tailored microstructural order

Colloidal solids of monosized, solution-derived SiO2 were prepared under forced and unforced sedimentation conditions to tailor the level of particulate order. Photonic band gaps were observed in the blue part of the visible spectrum and their spectral shape is shown experimentally to correlate directly to the degree of long- and short-range particulate order. These results are discussed by analogy to the x-ray diffraction of crystals and glasses as is the practical applicability of “photonic glasses” with respect to the more widely studied “photonic crystals.”