Exploiting the Modulation Effects of Epitaxial Vanadium Film in a Quasi-BIC-Based Terahertz Metamaterial

Terahertz (THz) metamaterials based on phase-change materials (PCMs) offer promising approaches to the dynamic modulation of electromagnetic responses. In this study, we design and experimentally demonstrate a tunable THz metamaterial composed of a symmetric split-ring resonator (SRR) pair, with the left halves covered by a 35 nm thick epitaxial vanadium dioxide (VO₂) film, enabling the simultaneous exploitation of both permittivity- and conductivity-induced modulation mechanisms. During the metal-insulator transition (MIT) of VO₂, cooperative changes in permittivity and conductivity lead to the excitation, redshift, and eventual disappearance of a quasi-bound state in the continuum (QBIC) resonance. Finite element simulations, using optical parameters of VO₂ film defined by the Drude-Smith model, predict the evolution of the transmission spectra well. These results indicate that the permittivity change originating from mesoscopic carrier confinement is a non-negligible factor in THz metamaterials hybridized with VO₂ film and also reveal the potential for developing reconfigurable THz metamaterials based on the dielectric modulation effects of VO₂ film.