Bi-layer Metamaterial based Broadband Linear Polarization Converter under Two Coherent Beam Illumination

We demonstrate a bi-layer metamaterial structure with mirror symmetry that acts as a linear polarization converter under two-antisymmetric-beam illumination. Its high performance, including broad bandwidth, high transmittance and high efficiency, originates from the combination of two interference processes: the Fabry-Perot-like cavity effect between two metallic patterned layers and coherent excitations of spatially separated subwavelength resonators. Terahertz (THz) experiments show good agreement with numerical simulations.