Large Absolute Photonic Bandgap at High Frequencies in a Two-Dimensional Photonic Crystal with a Hexagonal Structure

A new large absolute photonic bandgap at high normalized frequencies can be obtained in a two-dimensional hexagonal structure with alumina cylinders in air by reducing the symmetry of the structure. An instructive procedure is described for finding the optimal configuration which gives the maximum absolute bandgap Δω = 0.091(2π c / a ).