HEXAGONAL PHOTONIC-BAND-GAP STRUCTURES

We investigate a class of two-dimensional hexagonal structures that po ssess photonic band gaps. This class includes the previously studied t riangular structure as a particular case. By symmetry analysis, we obt ain a clear insight into the gap opening and we show how the photonic band gaps are affected by the characteristics of materials, according to whether the dielectric constant of the cylinders is larger or small er than the background one. The photonic band structures present numer ous gaps, and we study the evolution of these gaps as functions of the diameter and nature of cylinders. Our results demonstrate the existen ce of absolute band gaps for many configurations, largest gaps being o btained for triangular and graphite structures.