In this study, we use a phase-changing material vanadium dioxide (VO₂) to design a multilayer metasurface structure to achieve the transition from an electromagnetically induced transparency(EIT) device to an absorber. The structure consists of a gold layer, a polyimide spacer layer, a VO₂ layer, and a sapphire substrate. The top layer consists of one cut wire and two split-ring resonators with the same parameters. When the VO₂ layer is in its insulating phase at room temperature, the peak of the EIT device will appear near 1.138 THz. When the VO₂ layer is in the metallic state, two absorption peaks above 99.5% appear separately at 1.19 and 1.378 THz, respectively. To the best of our knowledge, this is the first time that a coupled mode equation is used to perform theoretical calculations for EIT devices and perfect absorbers simultaneously, and this is also the first time that coupled mode equations are used for the theoretical calculations of two absorption peaks in an absorber. The proposed metasurface combines the advantages of terahertz absorption, EIT and active device control, which will provide more ideas for the design of future terahertz devices and is also significant for the design and development of radomes for future stealth aircraft.

Coupling is a ubiquitous phenomenon observed in various systems, which profoundly alters the original oscillation state of resonant systems and leads to the unique optical properties of metasurfaces. In this study, we introduce a terahertz (THz) tunable coupling metasurface characterized by a four-fold rotation (C₄) symmetry-breaking structural array achieved through the incorporation of vanadium dioxide (VO₂). This disruption of the C₄ symmetry results in dynamically controlled electromagnetic interactions and couplings between excitation modes. The coupling between new resonant modes modifies the peak of electromagnetic-induced transparency (EIT) within the C₄ symmetric metasurfaces, simulating the mutual interference process between modes. Additionally, breaking the C₄ symmetry enhances the mirror asymmetry, and imparts distinct chiral properties in the far-field during the experimental process. This research demonstrates promising applications in diverse fields, including biological monitoring, light modulation, sensing, and nonlinear enhancement.