Tunable terahertz metalens based on VO2

In this study, we propose a meta-atom capable of efficient cross-polarization conversion for circularly polarized (CP) waves, demonstrating exceptional polarization conversion ratios exceeding 90% across an ultra-broadband frequency range of 0.86–2.02 THz. The reflective performance for CP waves exhibits remarkable sensitivity to the conductivity variations of vanadium dioxide (VO 2 ). Through precise rotational adjustment of the top VO 2 -metal hybrid structure, full 2 π phase modulation of the reflected CP wave can be achieved throughout the entire operational bandwidth. Furthermore, by employing strategic meta-atom arrangements and dynamically tuning VO 2 conductivity, we design reconfigurable metalenses capable of implementing diverse focusing schemes, including single-point focusing, dual-point focusing, and focusing orbital angular momentum. Comprehensive simulation results verify the outstanding wavefront modulation performance of our proposed tunable terahertz metalens. This research provides groundbreaking insights for the development of dynamically tunable focusing metalenses, holding substantial promise for transformative applications in advanced terahertz communication systems, high-resolution imaging technologies, and precision focusing devices. We believe that the proposed approach opens new avenues for metalenses in the terahertz regime.