Tunable transmissive terahertz polarization rotator based on a resonance-decoupled metal-VO₂ hybrid metasurface

The emergence of novel tunable materials such as vanadium dioxide (VO₂), graphene, and black phosphorus has endowed terahertz (THz) metasurfaces with more flexibility and dynamic tunability, promoting the development of THz lasers, modulators, and detectors. In previous studies, most transmissive THz linear polarization rotators based on these materials are complicated in structure or suffer from poor performance, such as low transmittance and modulation depth. In this paper, we present a tunable transmissive THz linear polarization rotator based on VO₂. Theoretical analysis and numerical simulation indicate that by adjusting the conductivity of VO₂ with temperature, the rotator outputs linearly polarized light with a tunable rotation angle. It can achieve a rotation angle tuning range from 40° to -36° while maintaining the transmittance above 66.9%. Furthermore, the rotation angles in the insulating and metallic states can be tuned independently by adjusting the orientation of the structure, and the difference in the rotation angles between the two states can be tuned in the range of 0°∼90°. Such an excellent performance is attributed to the decoupled magnetic and electric dipole resonances excited in the hybrid metasurface, as well as constructive interference in the dielectric cavity. Finally, a polarization-selective dynamic display scheme is proposed, which enables a switchable display of two polarization patterns by varying the temperature. Our work provides inspiration for the design and fabrication of tunable THz polarization modulators.