Ultra-broad band diode-like asymmetric transmission of linearly polarized waves based on the three-layered chiral structure

We propose a kind of three-layered metamaterial which can realize ultra-broad band diode-like asymmetric transmission (AT) of linearly polarized waves and almost 90° cross-polarization rotation in the optical region. Numerical results reveal that the AT amplitude enables to achieve the maximum of 0.97 and surpass 0.8 ranging from 124 to 244 THz for linearly polarized waves. Two layers of sub-wavelength gratings and a split-ring resonator in the middle of the two dielectric substrates form the three-layered structure. We believe that our work will offer a new opportunity in many optical applications of optical devices such as polarization rotators and diode-like devices.