Three-dimensional photonic crystals based on macroporous silicon with modulated pore diameter

We report on the fabrication and optical characterization of a three-dimens ional (3D) photonic crystal on the basis of macroporous silicon. The struct ure consists of a 2D array of air pores in silicon whose diameter is varied (modulated) periodically with depth. The bandstructure of the resulting 3D hexagonal photonic crystal is calculated and compared with transmission me asurements. The described structure allows to adjust the dispersion relatio n along the pore axis almost independently from the dispersion relation in the plane perpendicular to the pore axis. (C) 2001 American Institute of Ph ysics.