Tunable Terahertz Metamaterials from Dual Narrowband Absorption to Broadband Absorption Enabled by Vanadium Dioxide

Abstract

Conventional terahertz (THz) metamaterial absorbers suffer from fixed electromagnetic responses after structural fabrication, which severely restricts the flexible switching between high-quality-factor narrowband absorption and high-efficiency broadband absorption. To overcome this limitation, a reconfigurable THz metamaterial absorber utilizing the phase-change material vanadium dioxide (VO 2 ) is proposed in this work. The proposed absorber adopts a multi-layer composite structure, which consists of a patterned metal resonant layer, a VO 2 functional modulation layer, a dielectric spacer layer, and a metal reflective bottom plate. Leveraging the significant reversible conductivity variation of VO 2 during its insulator-to-metal transition, the proposed absorber realizes tunable switching between dual-narrowband and broadband absorption via precise modulation of the VO 2 phase state. The designed multilayer absorber achieves tunable absorption mode switching by regulating the phase characteristics of VO 2 ; when VO 2 operates in the insulating state, structural cavity resonances are stimulated to yield efficient dual-narrowband absorption performance, while the phase transition of VO 2 to the metallic state enhances multi-resonance coupling effects to broaden and merge discrete absorption peaks, enabling high-efficiency broadband absorption. The proposed absorber maintains superior absorption efficiency across different conductivity states of VO 2 and possesses outstanding reconfigurability. Compared with traditional single-functional THz absorbers, this design integrates the high wavelength selectivity of narrowband absorption and the wide-range electromagnetic modulation capability of broadband absorption, exhibiting great application prospects in reconfigurable THz devices, high-precision sensing, and intelligent communication systems.