Photonic band gap (PBG) structures are multidimensional lattices, formed by a strong modulation of dielectric constant which prevent the propagation of photons over a forbidden energy range1. Since the first demonstration of a PBG at microwave frequencies2-7, it has proved technologically difficult to create a PBG in the optical region of the spectrum8-11 since the band gap centre wavelength is of the order of twice the lattice pitch. Recently, we have succeeded in fabricating novel waveguide designs which incorporate a TE polarised visible photonic band gap12,13 By reducing the band gap to visible wavelengths, we greatly simplify the experimental investigation of the behaviour of these complicated structures.
In this paper, we present the fabrication and initial optical testing of devices with band gaps in the visible wavelength range 545nm-632.8nm. These devices demonstrate unusual optical effects dependent upon the number of lattice periods such as: broadband wavelength filtering, wavelength dependent beam splitting, and broadband polarisation selective routing. In contrast to the well known active applications of PBGs, we suggest a host of new passive applications for PBGs in optical computing and wavelength division multiplexed (WDM) communications.