Spoof plasmon polariton coupler based on the high‐order modes of reflective metasurface

Different from previous phase gradient metasurfaces, in this letter we show that the spoof plasmon polariton conversion is dominated by the high‐order surface wave modes rather than the pre‐defined linear phase distribution. The latter becomes invalid due to the coupling between different metallic unit cells of the metasurface. To demonstrate this point, a metasurface, which includes six different H‐shaped structures in a super cell, is designed based on the high‐order surface wave modes with a nonlinear reflective phase distribution. The simulated and measured results support the proposed theory, that is, the designed metasurface can convert x‐ and y‐polarized incident waves into spoof plasmon polariton at 8.9, 10.6, and 11.9 GHz. The metasurface not only verifies the mechanism of spoof plasmon polariton conversion, but also shows great potential in realizing cloaks, flat antennas, and so on.