Thickness-dependent photonic bandgap in a onedimensional single-negative photonic crystal

The thickness-dependent photonic bandgap for a one-dimensional photonic crystal consisting of two different single-negative (SNG) materials is theoretically investigated. The two SNG materials include one with a single-negative permittivity (ε<0,μ>0) and the other with a single-negative permeability (μ<0,ε>0). It is found that the size of the bandgap and the positions of the band edges are strongly dependent on the thickness ratio of the two constituent SNG layers. First, the bandgap decreases with increase in the ratio and eventually shrinks to zero at a critical value of the ratio. Then the bandgap is opened up and enhanced when the thickness ratio is larger than the critical ratio. By using the composite right/left-hand transmission-line model, we qualitatively explained the bandgap's shifting behaviors that are due to the variation of the thickness.