Absorption modulation of quasi-BIC in Si-VO2 composite metasurface at near-infrared wavelength

Bound states in the continuum (BIC) have attracted great attention in nanophotonics in the past few years. The metasurface with inverted symmetry breaking exhibits high Q resonance through quasi-BIC (Q-BIC), which realizes light modulation, sensing and nonlinear generation. In this work, a symmetry-broken Si-VO2 composite metasurface is studied and modulate near-infrared light absorption in Q-BIC mode. First, a L-shaped Si metasurface with broken C-4v symmetry is designed, which realizes the transition from BIC to Q-BIC and shows strong circular dichroism. Later, phase-change material VO2 is integrated into the L-shaped Si metasurface. By changing the ambient temperature, the Si-VO2 composite metasurface shows distinct light absorption characteristics, including insensitivity to incident angle and a maximum absorption modulation of up to 210%. The results show that VO2 can effectively modified Q-BIC resonator to realize the modulation absorption of near-infrared light.