▎ 摘　　要

We present a broadband tunable polarization converter in terahertz (THz) frequency based on a hybrid metamaterial comprising I-shaped metallic resonators and double layer graphene sheets. The proposed device can dynamically switch its functionalities among linear-to-linear, linear-to-circular, and linear-to-elliptical polarization conversion in broadband by electrically controlling the Fermi energy of the graphene sheets without reoptimizing and refabricating the structures. This device concept offers a further step in developing broadband tunable polarizers and polarization switchers and has potentially applications in THz communications, sensing and spectroscopy.