Obtaining single mode spoof surface plasmon polaritons under circular polarized incidence

Abstract

The study of spoof surface plasmon polaritons (SSPPs) has become one of the hotspots of electromagnetics because of their peculiar properties and broad application prospects. Compared with linear polarized (LP) waves, which can be efficiently coupled into single (TE or TM) mode SSPPs by phase gradient metasurfaces (PGMs), circular polarized (CP) waves are difficult for SSPPs devices to use. Although Pancharatnam–Berry (PB) phase manipulating metasurfaces can successfully couple CP waves into hybrid (TE and TM) modes SSPPs, arbitrary pure mode SSPPs are still unavailable under CP incidence. In this study, a new scheme of PGMs coupler was designed to solve the above problem. The multi-layered PGMs consist of V-shaped structure and patch structure, which play the roles of achieving circular-to-linear polarization conversion and providing phase gradient respectively. A plasmonic metasurface placed 10 mm below the PGMs can support the propagation of TE and TM modes SSPPs. As a result, arbitrary single mode SSPPs can be excited and propagate under CP incidence at 12 GHz, which means that we can convert CP waves into either TE or TM mode SSPPs we want through this PGMs coupler. Both simulations and measurements demonstrated novel ideas, and the calculated coupling efficiencies are all higher than 62.0%. The PGMs coupler we designed will break the limitation of incident waves on coupled SSPPs and provide a new method for the control and utilization of CP waves in engineering.