Reconfigurable Spoof plasmonic Coupler for Dynamic Switching between Forward and Backward Propagations

A reconfigurable coupler constructed using two spoof surface plasmon polariton (SSPP) waveguides and a spoof localized surface plasmon (SLSP) resonator to achieve switching between the forward and backward coupling of SSPP waves is proposed. By changing the bias voltage applied to the varactor diodes loaded in the SSPP waveguide, the dispersion of the plasmonic structure is adjusted to achieve a reversed group velocity. Consequently, the direction of the coupled SSPP waves can be dynamically controlled at the same operating frequency. The tunability of this coupler can be further improved by incorporating varactor diodes into the SLSP resonator, where forward–backward coupling can be achieved at multiple frequencies.