Asymmetric electromagnetic wave transmission of linear polarization via polarization conversion through chiral metamaterial structures

In this paper a kind of chiral metamaterial structure is proposed that can achieve asymmetric transmission for forward and backward propagations of linearly polarized electromagnetic (EM) waves. We first give a theoretical analysis on a kind of bilayered metamaterial structure with specific structure asymmetry that enables the asymmetric EM wave transmission only for linear polarization. Then by constructing a proof-of-concept metamaterial sample with twisted split ring resonator patterns on both sides of a dielectric slab, we demonstrate substantial asymmetric transmission for linear polarizations, but none for circular polarizations through full-wave simulation and measurement at microwave frequency. Strong optical activity is found in the chiral metamaterial indicating that the intriguing asymmetric transmission is caused by the directional difference in cross polarization conversion. By scaling down the structure, the proposed concept could be utilized in other frequency bands, such as terahertz and optical range.