Anomalous dispersion and superluminal group velocity in a coaxial photonic crystal: Theory and experiment

Abstract

We demonstrate that coaxial cables with a periodic impedance exhibit dispersion properties specific to photonic crystals, albeit on a much lower frequency scale. Highly superluminal (>2c) pulse propagation is observed near the photonic band gap at 10 MHz. The influence of group velocity dispersion and crystal length on the traveling speed and shape of a Gaussian pulse are discussed. Results compare favorably with a simple multilayer theory and a coupled-mass model of the structure.