Tunneling of electromagnetic waves in two-dimensional photonic crystals

The tunneling of electromagnetic waves in the band-gap region of periodic dielectric arrays is investigated with the coherent microwave transient spectroscopy technique. Transmission probabilities at frequencies in the fundamental band gap are measured and found to depend exponentially on sample thickness. From these results the frequency dependence of the imaginary wave vector is determined. The peak imaginary wave vector, which occurs at midgap, is observed to be proportional to the width of the band gap, unlike the case for single-barrier tunneling of electrons, where the relationship is expected to vary as the square root of the barrier height.