Active modulation and sensing of quasi-bound states in the continuum in symmetry-broken all-dielectric metasurfaces based on VO 2 phase transition

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A symmetry-broken Si-VO 2 composite all-dielectric metasurface is constructed in this work, where a magnetic-dipole-dominated symmetry-protected bound state in the continuum (BIC) mode is realized at 1518.94 nm. Numerical simulations confirm that the embedding position of the VO 2 thin film serves as a critical structural parameter. As the VO 2 film shifts from the top to the bottom of the silicon resonator, the enhanced mode-field overlap yields a modulation depth of 311.29% under the bottom-embedding configuration at θ =4 ∘ . Meanwhile, an inherent trade-off between the Q-factor and modulation depth is revealed: as the symmetry-breaking angle θ increases from 2° to 10°, the Q-factor decreases continuously, while the relative transmission modulation depth rises monotonically and reaches a peak of 3986.62% at θ =10 ∘ , which provides flexible guidance for parameter selection in diverse application scenarios. In addition, the metasurface exhibits excellent refractive index sensing performance, with a sensitivity of 350 nm/RIU and a maximum figure of merit of 4217 according to simulation results. Distinct from most reported single-function structures, this work integrates active dynamic modulation and high-sensitivity sensing into a single quasi-bound state in the continuum (Q-BIC) mode, providing a systematic design strategy for high-performance near-infrared active photonic devices and holding broad application prospects in dynamic optical filtering, optical switching, biochemical sensing, and on-chip photonic integration.