Tunable circular polarization conversion and asymmetric transmission of planar chiral graphene-metamaterial in terahertz region

Two-dimensional chirality induced polarization conversion and asymmetric transmission have great potential for polarization applications. We propose graphene-based planar chiral metamaterial and its complementary structure with dual functionality of both circular polarization conversion and asymmetric transmission in terahertz (THz) region. The conversion efficiency of chiral structure can reach up to 37.33/lambda, which is comparable with three-dimensional chiral structure made of metal due to the unique optoelectronic properties of graphene. The transmission asymmetry of complementary chiral meta-material originating from the high order plasmonic resonance can be tuned from 0.049% to 3.504% by changing Fermi energy, and the asymmetry can also be enhanced via geometrical optimization. This work raises the prospect of switchable, compact, and on-chip THz polarized devices with graphene materials. (C) 2017 Elsevier Ltd. All rights reserved.