Enhanced complete photonic band gap in moderate refractive index contrast chalcogenide-air system with connected-annular-rods photonic crystals

Connected-annular-rods photonic crystals (CARPC) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap (CPBG) for chalcogenide material systems with moderate refractive index contrast. For the typical chalcogenide-glass—air system with index contrast of 2.8:1, the optimized square lattice CARPC exhibits a significantly larger normalized CPBG of about 13.50 %, though the use of triangular lattice CARPC is unable to enhance the CPBG. It is almost twice as large as our previously reported result. Moreover, the CPBG of the square lattice CARPC could remain until an index contrast as low as 2.24:1. The result not only favors wideband CPBG applications for index contrast systems near 2.8:1, but also makes various optical applications that are dependent on CPBG possible for more widely index contrast systems.