Phase-transition-driven radiative-decay engineering for high-Q quasi-BIC states in graphene-VO2 metasurfaces.

Dynamic control of radiative coupling in photonic metasurfaces is typically constrained by fixed structural asymmetry, limiting active tunability of high-Q resonant states. Here, a hybrid graphene-vanadium dioxide (VO2) metasurface is proposed to realize phase-transition-driven modulation of radiative decay in the terahertz regime. The structure integrates a split VO2 resonator with a diagonally oriented graphene perturbation, where the phase-dependent conductivity evolution of VO2 actively governs the balance between radiative and dissipative loss channels. In the insulating phase, destructive interference suppresses radiation leakage, producing an ultranarrow quasi-bound state in the continuum (quasi-BIC) resonance with a quality factor (Q) of 1612.97, increasing to 2092.31 under oblique excitation. Following the thermally induced insulator-metal transition of VO2, enhanced conductive dissipation and modified electromagnetic boundary conditions progressively transform the response from a radiation-suppressed to a loss-dominated resonant regime. This establishes a materials-driven mechanism for dynamic resonance engineering without permanent structural modification. Additional tunability is achieved through thermal excitation, electrostatic regulation of graphene conductivity, and incident-angle variation, enabling multiparameter control of resonance confinement and linewidth. These findings demonstrate how correlated inorganic phase-transition materials can be exploited to manipulate radiative processes in hybrid nanophotonic architectures and provide insight into the structure-property relationships governing tunable electromagnetic confinement in graphene-VO2 systems.