Band structure of air-photonic crystal fibre cladding

We calculate the photonic band structure for a two-dimensional (2D) photonic crystal (PC) formed by a hexagonal array of circular rings embedded in air. This crystal has been used as the cladding of a photonic crystal fibre whose core is composed by air. We solve the Maxwell equations using the plane wave method. Our calculations reveal that for propagation in the plane of periodicity, the PC possesses no complete photonic band gap. However we demonstrate the existence of complete photonic band gaps for propagation out of the plane of periodicity.