Superluminal propagation in plasma photonic band gap materials

Electromagnetic wave propagation in one-dimensional plasma photonic crystal (PPC) made of alternate thin layers of two materials namely plasma and dielectric materials is theoretically studied. Dispersion relation is obtained. Group velocity, effective group index, reflectivity and superluminal behavior have been studied. The study of the reflectivity plot shows that the designed structure works as a perfect reflector/mirror in a certain range of frequency. Left-right and up-down symmetries (and flip-flop) are observed when we study the variation of group velocity with frequency. Abnormal behavior of group velocity (negative) inside the PPC structure creates the superluminal propagation of electromagnetic waves. The marked existence of symmetries may be exploited for directional switching in optical circuits.