Localized spoof surface plasmons in textured open metal surfaces.

We experimentally demonstrate that textured open metal surfaces, i.e., the ultrathin fan-shaped metallic strips, are able to support spoof localized surface plasmons (spoof-LSPs) in the microwave frequencies. Unlike conventional spoof-LSPs supported on textured closed metal surfaces, which originate from the interference of clockwise and counterclockwise propagating surface modes, spoof-LSPs on textured open metal surfaces arise from the Fabry-Perot-like resonances due to the terminations of the open surfaces. We show that both the number of modes and the resonance frequencies of spoof-LSPs on textured open metal surfaces can be engineered through tuning the grating numbers (or total length) of the structured fan-shaped metallic strip. This enables the tuning of the spoof-plasmonic resonator by simply changing its length, rather than the complete geometry, simplifying the design to just one degree of freedom. Experimental evidence of the spoof-LSP Fabry-Perot resonators in the microwave regimes is presented with near-field response spectra and mode profiles imaged directly.