Second-Harmonic Generation of Spoof Surface Plasmon Polaritons Using Nonlinear Plasmonic Metamaterials

Second-harmonic generation is one of the most important applications of nonlinear effects, which has attracted great interest in nonlinear optics and microwaves in the past decades. Here, the second harmonics of spoof surface plasmon polaritons (SPPs) are generated with high efficiency at microwave frequencies using a subwavelength-scale nonlinear active device that is integrated on specially designed plasmonic waveguides. Composed of two ultrathin corrugated metallic strips printed on the top and bottom surfaces of a thin dielectric slab antisymmetrically, the plasmonic waveguide supports broadband propagations of spoof SPPs with a strong subwavelength effect, whose dispersion property can be controlled by changing the geometrical parameters. By loading the nonlinear device to the intersection of two plasmonic waveguides with different corrugation depths, the efficient generation of second-harmonic SPPs is experimentally demonstrated in the broad frequency band. The proposed second-harmonic generator is directly used as an SPP frequency multiplier, and the proposed method can be extended to achieve high-order harmonics, which are essential to SPP integrated circuits and systems.