Mechanically reconfigurable and electrically tunable active terahertz chiral metamaterials

Active and efficient control of polarization states of electromagnetic wave is highly desirable in broad optical and terahertz (THz) devices. Herein, we have proposed a type of mechanically reconfigurable and electrically tunable THz chiral metamaterials that are consisting of periodical U-shaped split ring resonators (USRRs) patterned on the graphene Miura-origami (G-Mori) structures. We demonstrate that their circular dichroism (CD) as high as 0.93 originate from the coupling effect between the proper arranged USRRs and the G-Mori structure, which can be tuned through continuous change of the folding angle and Fermi energy level of graphene origami via mechanical and electrical methods in reversible manner, respectively. Furthermore, the proposed chiral metamaterials possess ideal quarter-wave-plate behavior at the resonance which also can be controlled by combining mechanical and electrical methods. The mechanically reconfigurable and electrically tunable circular dichroism and polarization conversion properties of the chiral metamaterials will be suitable for development of various polarization-related THz devices, such as highly sensitive chiral sensors, active polarization modulators and converters.