Ultra-broadband linear polarization converter based on anisotropic metasurface

Through the manipulation of co-polarized reflection and cross-polarized reflection from a periodic array of metal-dielectric-metal resonators, a plethora of unprecedented metamaterial devices have been successfully demonstrated, such as perfect absorber and polarization converter. Recently, some broadband absorbers based on anisotropic resonators have been reported, which are actually poor absorbers when the cross-polarized reflection is considered. Here, we demonstrate that an ultra-wideband and high-efficiency reflective cross-polarization convertor can be achieved by breaking the symmetry of the resonator unit of a perfect absorber. Simulation results show that the polarization conversion ratio of the proposed metasurface is above 90% in the frequency range from 6.67 to 17.1 GHz and the relative bandwidth reaches 87.7%. The experimental results are in good agreement with the simulation results. The method paves a new way for the design of broadband polarization convertor, which can also be extended to the terahertz band.