Broadband and high-efficiency circular polarizer based on planar-helix chiral metamaterials

We reveal a broadband and high-efficiency circular polarizer based on chiral metamaterials composed of an array of planar helices, which can effectively reject the incident left-hand circularly polarized (LCP) wave, while allowing the right-hand circularly polarized (RCP) wave to pass through it. The physical mechanism of the proposed circular polarizer is explained with the aid of the current distributions under the excitations of LCP and RCP waves. Microwave experiments are performed to verify this idea, and measured results are in good agreement with the numerical ones. Experimental results show that a fractional bandwidth of 75.6% for the transmittance of the LCP wave lower than 0.2 can be obtained. Moreover, the proposed circular polarizer exhibits a high transmittance of over 0.9 for the RCP incident wave and a high circular polarization selection efficiency of over 0.95. The proposed circular polarizer will be potentially very useful for satellite and optical communications.