▎ 摘　　要

We propose a tunable broadband reflective cross polarization converter (CPC) composed of a graphene sheet with a T-shaped carved-hollowarray. In the mid-infrared region, cross polarization conversion with 5.17 THz bandwidth is achieved due to the superimposition of the two reflection components with a phase difference of nearly 180 degrees. The polarization conversion ratio is larger than 80% in this broadband range, and the fractional bandwidth is 40%. The physical mechanism of CPC is attributed to the excitation of symmetric and antisymmetric graphene surface plasmons. The CPC broadband can always be retained when the incident angle increases from 0 degrees to 20 degrees, and the polarization angle increases from 40 degrees to 50 degrees. Also, the tunable responses of the reflective polarizer with Fermi energy and electron scattering time are discussed. Our design can be widely applied to adjustable broadband polarization conversion. (C) 2021 Optical Society of America