Abstract

Synthetic opal provides a 3-dimensional template for the formation of photonic crystals for visible light operation. Improvement of the photonic bandgap structure of opal has been approached via coating the inner surface of the opal with TiO2, InP or GaP layers using CVD and MOCVD. In contrast to other methods of embedding high refractive index materials in opal these methods allow the crystallinity of the original template to be preserved. The high refractive index coating serves to increase the width of the photonic stop-band and to squeeze the angular dispersion of the stopband. The combined effect of these two factors is overlapping of the stop-band over a wide range of solid angles, in total up to ±20–30° from the normal to the (111) plane of the opal package, thus exceeding by as much as 3 times the corresponding range for bare opal. The magnitude of this effect depends on the amount of deposited material. Qualitatively, the trend of changes in the PBG structure of coated opals, in comparison with bare opal, is the same as for completely infilled opals—but the remaining unfilled space in the photonic lattice void provides a low refractive index background, thus preserving a deeper modulation of the dielectric constant.

© 1999 Optical Society of America