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.