Temperature‐Tunable Terahertz Device Constructed With Vanadium Dioxide Metasurface

This study develops a simply‐structured multifunctional terahertz absorber through numerical simulation. The device is constructed in a three‐layer stack: a gold thin‐film substrate at the bottom, silicon dioxide as the dielectric spacer in the middle, and vanadium dioxide thin film on the top. Vanadium dioxide possesses a typical thermally induced insulator–metal phase transition mechanism: it maintains an insulating state with a band gap at low temperatures, and thermal excitation can trigger the rearrangement of its crystal structure and electronic band structure, enabling it to transform into a metallic conductive state at high temperatures. Benefiting from this unique thermally triggered insulator–metal phase transition property of vanadium dioxide, the electromagnetic performance of the absorber can be thermally tuned. Simulation results show that the device produces full reflection of incoming terahertz waves at 312 K. As the temperature increases to 345 K, ultra‐high absorption is obtained across 4.5–10.1 THz, and the absorbance can be continuously adjusted from 0 to 0.999. Electric‐field distributions within the structure under different temperatures are compared to reveal the underlying mechanism for the reflection‐absorption switching effect, which is further explained using impedance‐matching theory. Moreover, how key structural parameters affect the absorption performance is analyzed, which supplies valid data for device fabrication and practical usage. The absorber is insensitive to polarization and maintains stable performance under oblique incidence. Absorption hardly degrades when the incident angle varies from 0° to 50°. With promising application prospects in terahertz stealth and light modulation, the device offers useful insights for the design of similar terahertz functional devices.