Thermally tunable terahertz smart window based on VO₂ phase change material with broadband absorption and...

Metamaterial absorber devices that can achieve broadband control and be adapted to achieve dynamic and intelligent regulation of terahertz (THz) waves are research hotspots. A THz smart window device with a sandwich structure based on (VO₂) phase change material was designed. This device was composed of two layers of VO₂ at the top and bottom, and a SiO₂ dielectric layer in the middle. The top layer of VO₂ was etched into an axisymmetric square array microstructure. The thermally induced insulator-metal phase transition of VO₂ was simulated, and the absorption, reflection and transmission characteristics of the device were obtained through simulation. The effects of temperature, polarization direction, structural parameters and incident angle on the electromagnetic performance of the device were systematically investigated, and the intrinsic physical mechanism of absorption and transmission of the device was revealed simultaneously. The device realized dynamic switching between THz wave absorption and transmission by relying on the reversible phase transition of VO₂. In the low-temperature insulating state at 328 K to 333 K, it achieved a transmission rate >80% within a frequency range of 0 THz to 12.1 THz, corresponding to an ultra-wideband transmission bandwidth of 12.1 THz. In the high-temperature metallic state at 342 K to 345 K, it achieved an absorption rate >90% and a bandwidth of 6.47 THz for wideband absorption. The polarization-independent absorption and transmission characteristics of the device were attributed to the consistent electromagnetic response elicited by the axisymmetric microstructure design. The synergistic effect of LSPR and CR at high temperatures was the core mechanism for achieving high absorption in the device, while the all-dielectric structure at low temperatures ensured efficient transmission of THz waves. The device exhibited strong tolerance to processing deviations in key structural parameters (e.g., period and top VO₂ thickness) and retained superior angular stability if the incident angle was 0°-60°, and we could achieve on-demand regulation of absorption performance by fine-tuning the structural parameters. This device possessed thermal adjustable switching, strong environmental adaptability, and high manufacturing fault tolerance. Our study provides important structural ideas and theoretical references for the design and practical application of THz intelligent window devices.