Observations of band structure and reduced group velocity in epitaxial GaN-sapphire 2D photonic crystals

We report experimental results for the band structure of 2-dimensional tria ngular photonic crystals of air holes in an epitaxial group III-nitride wav eguide film. Surface coupling techniques enable the observation of sharp re sonance dips in the transmission spectra due to a resonance phenomenon betw een the incident light and Bloch modes of the photonic crystal. The positio n of the dips has been measured as a function of angle of incidence and the photonic band structure has been successfully constructed by the measureme nt. Corresponding Bloch-mode group velocities have also been obtained.