A novel plasmonic waveguide for the dual-band transmission of spoof surface plasmon polaritons

The previously reported dual-band spoof surface plasmon polariton (SSPP) waveguides are based on Goubau line, microstrip technology, composite structures, or ultra-thick materials, which makes the fabrication difficult and hinders the mass production. In this paper, dual-band transmission mode of spoof surface plasmon polaritons (SSPPs) is generated along with a leaky region by a simple ultra-thin S-shaped spoof surface plasmon polariton waveguide. A CPW-type-based spoof SPP waveguide with periodic S-shaped grooves is designed for highly efficient dual-band mode conversion between the quasi-TEM mode in the common coplanar waveguide and the spoof SPPs on the S-shaped spoof SPP waveguide. From the dispersion analysis of the spoof SPP waveguide with and without the strips of S-shaped unit-cells, we clearly reveal the mechanism of the dual-band transmission characteristic for this compact waveguide. The evolution of wave vectors of the strips of S-shaped unit-cells in dual-band transmission mode and bandgap feature is also presented. The dispersion curve shows the leaky field is radiated during the fundamental to first higher order mode conversion due to the periodically modulated surface impedance of metallic strips of the S-shaped grooves. High transmission efficiency can be realized by the proposed design as indicated by the simulation results (|S11|< − 40 dB and |S21|> − 0.1 dB). There exists excellent synchronization between measured and simulated results, confirming the practical realizability of this concept.