Chiral coding metasurfaces with integrated vanadium dioxide for thermo-optic modulation of terahertz waves

摘要

ld of electromagnetics, there are many limitations to achieve simultaneous polarization conversion and wavefront control. The chiral coding metasurface based on the Pancharatnam-Berry (P-B) phase effectively helps to alleviate these restrictions and shows strong control over the terahertz radiation field. In this paper, the principle of chirality is theoretically analyzed and verified by simulation results. The circular dichroism Delta R (chiral effect) achieves 0.8. By combining the chirality and thermo-optic effect of vanadium dioxide (VO2), we propose three switchable metasurfaces for quantitative splitting and high-efficiency focusing (low-efficiency divergence) of terahertz beams. The amplitude switching efficiency of the circularly polarized (CP) and linearly polarized (LP) pencil beams is above 0.85. Under the excitation of LP waves, the first two chiral metasurfaces have one and two temperature-switchable reflective right-handed circularly polarized (RCP) pencil beams, respectively. The third chiral metasurface generates high-efficiency focusing for RCP waves and low-efficiency divergence for left-handed circularly polarized (LCP) waves. This work provides new methods for more flexible modulation of CP and LP waves and promotes the application of terahertz coding metasurfaces in communication. (C) 2020 Elsevier B.V. All rights reserved.