Terahertz pulse propagation in optical tunneling: causal vs. superluminal

Summary form only given. Recent claims of superluminal propagation of energy have returned to the forefront of current scientific debate including broad-band terahertz (THz) pulse propagation through frustrated total internal reflection (FTIR). Application of linear dispersion theory agrees precisely with our own experimental results. We have measured the amplitude and phase change of electromagnetic pulse transmission in FTIR with over 3 THz bandwidth. The pulse peaks arrive earlier in time as the width of the optical tunneling gap is increased with strong reshaping due to attenuation of the high frequency components. Although similar observations have led to claims of superluminal propagation of electromagnetic pulses, we demonstrate causal propagation with a simple model based on linear dispersion theory.