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 wa veguides, The technique relies on the coupling of external radiation incide nt on the lattices to the zone-folded bands of the photonic structures. Thi s coupling is detected owing to observation of resonance features in the re flectivity spectra. Good agreement between experiment and theory is found f or the second, third and fourth photonic bands. The technique allows extern al photons to be coupled into regions of the photonic dispersion curves clo se to the Brillouin zone boundaries, where the photon group velocity tends to zero, and thus has the potential to allow novel effects related to 'heav y photons' to be investigated.