Tunable broadband polarization rotator in terahertz frequency based on graphene metamaterial

Controlling the polarization state of terahertz waves, especially their dynamical manipulation, is highly demanded due to the increasing development of practical devices and application systems. Here, we present a terahertz dynamically tunable broadband metamaterial polarization rotator composed of two metal gratings and two orthogonal graphene grating structures as well as the dielectric spacers. By applying different bias voltages to adjust the Fermi energy of graphene, this rotator can conveniently rotate the polarization direction of the linearly polarized incident light by any desired angle among a wide range from 20 degrees to 70 degrees in transmission mode. Moreover, it can operate in a high efficiency, wide bandwidth, and wide angle of incidence tolerance and subwavelength thickness of approximately one fifth of the central wavelength. Therefore, this work could offer a new platform for exploring dynamically tunable terahertz polarized devices with graphene materials, and have potential applications in various areas, such as wireless communication and terahertz imaging. (C) 2018 Elsevier Ltd. All rights reserved.