Analysis of photonic band structure in a one-dimensional photonic crystal containing single-negative materials

A theoretical analysis on the angle- and thickness-dependent photonic band structure in a one-dimensional photonic crystal containing single-negative (SNG) materials is presented. The photonic crystal consists of two alternating SNG materials, including that one has a negative permittivity (ENG) and the other has a negative permeability (MNG). It is found that there are two types of SNG gaps. The first is the low-frequency gap which is very insensitive to the incident angle in the transversal electric (TE) wave. The second gap, which strongly relies on the incident angle for both TE and transversal magnetic (TM) waves, will close at the zero bandgap frequency at which the impedance match as well as the phase match in the constituent ENG and MNG layers must be simultaneously satisfied. This zero bandgap frequency is also strongly dependent on the incident angle. The band edges and the gap maps are investigated rigorously as a function of the incident angle and the ratio of thickness of the two SNG layers. The analyses are made in the lossless and lossy cases for both TE and TM waves. The inclusion of the loss enables us to further clarify two fundamentally distinct second SNG gaps which are separated by a threshold angle of incidence.