Use of single-negative material as a tunable defect in a dielectric photonic crystal heterostructure

The defect mode in a photonic crystal heterostructure of (1/2) N (2/1)N tuned by using a single-negative layer as a defect layer; that is, the structure to be considered is (1/2)ND (2/1)N, where 1, 2 are dielectrics, N is the stack number, and D is a defect layer taken to be a single-negative material. The results show that when D is a mu-negative (μ < 0) medium, the defect mode frequency is redshifted as a function of the thickness of D as well as the static permittivity. On the other hand, if D is an epsilon-negative (ε < 0) medium, the defect mode frequency is blueshifted as the defect layer thickness increases, but it is independent of the static permeability. We also investigate the angular dependence of the defect frequency for both two polarizations, transverse electric (TE) wave and transverse magnetic (TM) wave. The defect mode frequency is shown to be blueshifted as a function of the angle of incidence. Additionally, the shift in the TE wave is larger than that in the TM wave.