Terahertz spoof surface plasmon polaritons unidirectional coupling via slit pair

Spoof surface plasmon polaritons (SSPPs), as a new frontier in the terahertz (THz) range, is difficult to be effectively directional launched. In this paper, based on the near-field interference of the SSPPs generated by a pair of slits, we demonstrate that the oblique incident plane wave results in the unidirectional excitation of SSPPs. The extinction ration obtained with the finite element method (FEM) reaches up to 5.5. The coupler is potentially useful in the THz highly integrated plasmonic circuits.