Vanadium dioxide-based H-shaped terahertz metasurface for beam modulation

Metasurfaces have become increasingly crucial in applications involving electromagnetic beam modulation. Herein, an H-shaped terahertz (THz) metasurface based on vanadium dioxide (VO₂) is proposed to achieve an equal reflectivity amplitude of approximately 0.7 and a phase difference of 180° when VO₂ is in the insulating and metallic states, with the deviation less than 0.3%. The distribution of the electromagnetic field indicates that the constant amplitude inversion phenomenon is caused by the mode change from three-quarter wavelength resonance to surface plasmon resonance. The proposed metasurface unit has a minimum size of 26.6 µm, which reduces the cost of fabrication. Additionally, five feasible size-designing schemes are proposed, in which the amplitude varies in a narrow range of 0.675–0.685 with a phase difference of 180°, solving the potential problem of dimensional distortion caused by manufacturing process limitations. This structure provides a new way for the development of high-precision and low-cost intelligent THz metasurfaces.

超表面（Metasurfaces）在电磁波束调控相关应用中的重要性与日俱增。本文提出一种基于二氧化钒（vanadium dioxide, VO₂）的H型太赫兹（THz）超表面：当二氧化钒处于绝缘态与金属态时，该结构可实现约0.7的均等反射振幅与180°的相位差，偏差小于0.3%。电磁场分布分析表明，恒定振幅反转现象源于谐振模式从四分之三波长谐振向表面等离子体谐振（surface plasmon resonance）的转变。所提出的超表面单元最小尺寸仅为26.6 μm，可有效降低制备成本。此外，本文还提出五种可行的尺寸设计方案，此类方案的反射振幅在0.675~0.685的窄区间内波动，且相位差始终维持180°，可解决由制造工艺局限引发的潜在尺寸畸变问题。该结构为高精度、低成本智能太赫兹超表面的研发提供了全新思路。