Diffraction radiation based on an anti-symmetry structure of spoof surface-plasmon waveguide

Spoof surface-plasmon (SP) modes can be excited efficiently and propagate along the surface of double-layer corrugated metallic strips with anti-symmetry. Here, we propose a spoof SP structure with diffraction radiation, which is achieved by introducing phase-reversal geometry into the SP waveguide structure with a π-phase shift for adjacently reversed units. At the junction between two adjacent units, the discontinuity of the periodic structure can be viewed as a perturbation to generate space harmonics, thereby enabling efficient conversion of SP modes into free-space radiation modes. We demonstrate experimentally that the resultant radiation is analogous to Cherenkov radiation wakes, which occurs in the form of a radiation cone. The vast majority of the energy based on the surface wave is emitted into the free space. We expect that the proposed method could be an alternative to transforming the spoof SP modes into the radiation modes.