Experimental technique to determine the band structure of two-dimensional photonic lattices

An experimental technique to probe the energy against wavevector dispersion curves of two-dimensional photonic bandgap structures is demonstrated from the study of 360 nm period air hole honeycomb lattices etched in AlGaAs waveguides, The technique relies on the coupling of external radiation incident on the lattices to the zone-folded bands of the photonic structures. This coupling is detected owing to observation of resonance features in the reflectivity spectra. Good agreement between experiment and theory is found for the second, third and fourth photonic bands. The technique allows external photons to be coupled into regions of the photonic dispersion curves close to the Brillouin zone boundaries, where the photon group velocity tends to zero, and thus has the potential to allow novel effects related to 'heavy photons' to be investigated.