Variation of group velocity and complete bandgaps in two-dimensional photonic crystals with drilling holes into the dielectric rods

Two-dimensional square lattices of square cross-section dielectric rods in air, designed with an air hole drilled into each square rod, are studied theoretically. By adjusting the shift of the hole position in the square rod in each unit cell, the dielectric distribution of the square rod will be modified. A sizable complete band gap occurs for certain structural parameters and exhibits very flat photonic bands near such gap edge, which resulting in a sharp peak of density of states. In addition, the zero or small group velocities are observed in a broad region of k-space. This structure can be fabricated with materials widely used today and opens a fascinating area for applications in optoelectric devices.