Broadband asymmetric transmission of linearly polarised wave based on bilayered chiral metamaterial

In this study, a bilayered chiral metamaterial is proposed to realise broadband asymmetric transmission of linearly polarised electromagnetic wave in two opposite directions. Simulated results show that the bilayered chiral metamaterial can achieve broadband cross-polarisation transmission with an efficiency of over 0.8 from 10.27 to 11.57 GHz with two peaks of 0.92 and 0.94 at around 10.5 and 11.3 GHz, respectively, in one direction, <0.07 in the opposite direction at the same polarisation of the incident wave during the considered frequency band. Except a little blue shift, the measured results agree well with the simulated ones. Meanwhile, the structure can achieve nearly 90° polarisation conversion for both x- and y-polarised incident wave in two opposite directions and was verified by studying the polarisation azimuth rotation angles. Then, the surface current was studied to reveal the physical origin of the broadband asymmetric transmission of the structure.