Complete tunneling through the surface mode in a metal-insulator-metal waveguide

We report a novel phenomenon of complete tunneling based on amplification of an evanescent field through the surface plasmon mode in a metal-insulator-metal waveguide. Two different types of cutoff barriers, which are obtained by low-index and doubly-negative materials, are cascaded in such a way that the evanescently decaying and growing fields can compensate for each other, resulting in near-unity transmission. This phenomenon is different from previous resonant tunneling based on the longitudinal resonance in a propagating region sandwiched between two partially-reflecting mirrors. The numerical simulation results are in good agreement with the theoretical prediction. The effect of the length of each cut-off barrier on the transmission coefficient is also presented.