Tunable graphene/Sb2Se3 based metamaterials for reconfigurable terahertz devices

Abstract

Chiral metamaterials provide a powerful route for controlling the polarization state of terahertz (THz) waves; however, most reported structures rely on static metallic geometries with limited tunability. In this work, we present an actively tunable graphene/Sb2Se3 hybrid chiral metamaterial designed for dynamic modulation of THz polarization. The proposed architecture consists of double layer gold rosette resonators patterned on both sides of a sapphire substrate. Simulations performed using COMSOL Multiphysics analyze the chiroptical response through the frequency dependent Jones matrix formalism. Fabrication involved DC magnetron sputtering of Sb2Se3, resistive evaporation of gold, CVD grown graphene transfer, UV lithography, and ion beam etching. Continuous wave THz reflection spectroscopy is employed to characterize the chiral response under optical excitation. Illumination with a 915 nm laser induces a reversible modulation of the graphene surface conductivity mediated by the Sb2Se3 layer, resulting in a pronounced change in the polarization conversion efficiency. The 915 nm laser primarily induces photothermal heating in the Sb2Se3 layer, which in turn modulates the carrier density and surface conductivity of graphene, leading to a reversible change in the chiroptical response. The hybrid structure exhibits a significant tunable chiroptical response in the 0.50–0.75 THz frequency range, demonstrating the feasibility of all optical control of THz chirality. These results establish graphene/Sb2Se3 integrated chiral metamaterials as a compact and reconfigurable platform for active THz polarization modulation, with potential applications in sensing, imaging, and future wireless communication systems.