Blueprint for wafer-scale three-dimensional photonic band-gap synthesis by photoelectrochemical etching.

We present an architecture for three-dimensional photonic band-gap (PBG) material synthesis by oblique angle photoelectrochemical pore etching. This technique provides high aspect ratio pores, in which the pore diameter can be modulated by changing light intensity during the etch process. The naturally occurring "Kielovite" structure is a stretched version of the face-centered-cubic lattice of crisscrossing pores and exhibits a PBG to center frequency ratio of 8% in a background dielectric constant of 11.9 (silicon). We demonstrate that by modulating the pore radius in between pore intersections, the PBG can be doubled in size to nearly 16%. The enlarged PBG is robust against a number of structural perturbations.