Graphene-enabled tunable multifunctional metamaterial for dynamical polarization manipulation of broadband terahertz wave

Graphene-enabled metamaterials have emerged as promising photoelectric devices for dynamically controlling the polarization of electromagnetic waves. However, it is still a key technological challenge to design a tunable metamaterial possessing more sufficient freedom for polarization manipulation. Here, we propose a graphene-enabled tunable multifunctional metamaterial consisting of metallic strips arranged on a grounded polymer substrate embedded with a graphene sandwich structure to electrically control the polarization states of terahertz waves. By adjusting the Fermi energy of graphene through voltage biasing, the electromagnetic responses of the presented metamaterial can be tailored, resulting in dynamical tunable polarization manipulation in reflection mode. All expected performances are demonstrated through full wave simulation. The results reveal that this metamaterial device can operate as a switchable quarter-wave plate and a tunable half-wave plate for both linear- and circular-polarization incidences. Furthermore, the polarization conversion ratio, of which incident waves are converted to their cross-polarized reflection mode, can be continuously regulated from 2% to 95% in a wide band from 1.46 to 2.26 THz. The proposed metamaterial continues the process of developing tunable polarizers and polarization switchers with graphene materials, and may be applied in various areas such as wireless communication, terahertz sensing and imaging.