Groove-shape-induced bandwidth expansion of spoof surface plasmon polaritons on planar corrugated Goubau line in millimeter-wave range

•We present another method to control bandwidth of spoof SPPs without changing the depth of groove on ultrathin periodic corrugated Goubau lines.•We investigated groove-shape-induced bandwidth expansion effect by dispersion relation, slowdown factor and equivalent circuit mode of the three SSPPs, quantitatively.

Surface plasmon polaritons (SPPs) do not exist naturally in millimeter-wave range, but can be assisted by plasmonic meta-materials, generally periodic corrugated Goubau lines (PCGLs) coated on ultrathin flexible dielectric films. Compared to traditional PCGLs with rectangular groove, we present two single-edge PCGLs with different corrugation groove shapes of triangle and trapezoid to realize more broadband transmission of spoof SPPs (SSPPs). Both the simulated and experimental results show that the pass-band of SSPPs is expanded for the PCGLs with trapezoidal and triangular grooves in the same actual depth and conversion efficiency, compared to the case of traditional rectangular grooves. The dispersion relation and the equivalent circuit model of the three SSPPs are investigated to explain the groove-shape-induced bandwidth expansion effect. The bandwidth expansion effect opens up another path to control the pass-band of SSPPs.