Phys. Rev. A 84, 015801 (2011)

Honeycomb photonic crystal — the photonic analogue of graphene — has been actively studied for its range of interesting optical phenomena. Recent work by Chunfang Ouyang and colleagues from Fudan University in China now shows that the light states at the zigzag edges of photonic graphene have a sinusoidal dispersion similar to photonic crystal coupled-resonator optical waveguides. The structure under study is a honeycomb lattice of dielectric rods in air. The researchers theoretically show that by tuning the radii of the inner rods, the curve of sinusoidal dispersion can be made very flat to obtain simultaneously low group velocity and low group velocity dispersion. Because the edge states are below the light line in vacuum, the researchers say that their approach does not have intrinsic radiation loss and exhibits a larger group velocity bandwidth product (0.24) than that of photonic crystal coupled-resonator optical waveguides (0.09).