Group velocity, negative and ultra-high index of refraction in photonic band gap materials

Abstract

This paper shows that inside photonic band gap (PEG) materials the effective index of refraction neff, defined in terms of group velocity, becomes negative in a certain range of frequencies. Also, near the photonic-band edge the effective index of refraction neff attains exceptionally high values, which are greater than the refractive indices of the materials (n1 and n2) used. This is related to the anomalous behaviour of group velocity, which becomes negative in a certain range and approaches zero near the photonic-band edge. PBG material with a modified index of refraction has applications in the system of lasing without inversion and can also be used in construction of a perfect lens and other optical devices. © 2004 Wiley Periodicals, Inc.