Effects of noncircular inner scatterers on absolute photonic band gap of 2D triangular annular photonic crystals

Using the plane wave expansion method, the photonic band gap (PBG) structures of quasi 2D triangular annular photonic crystals (PCs) with square and hexagonal inner scatterers have been calculated. We investigate the effects of structural parameters on absolute PBGs for silicon (Si)-based and germanium (Ge)-based annular PCs. The results reveal that the optimal inner scatterer shape is hexagonal. Moreover, we discuss the PBGs as a function of inner scatterer orientation. As for silicon annular PCs, utilization of high refractive index or anisotropic tellurium (Te) rods can lead to the formation of larger absolute PBGs.