Active Control of Bound States in the Continuum in Toroidal Metasurfaces

Abstract

The remarkable properties of toroidal metasurfaces, featuring ultrahigh‐Q bound states in the continuum (BIC) resonances and nonradiating anapole modes, have garnered significant attention. The active manipulation of quasi‐BIC resonance characteristics offers substantial potential for advancing tunable metasurfaces. This study explores explicitly the application of vanadium dioxide, a phase change material widely used in active photonics and room‐temperature bolometric detectors, to control quasi‐BIC resonances in toroidal metasurfaces. The phase change transition of vanadium dioxide occurs in a narrow temperature range, providing a large variation in material resistivity. Through heating thin film patches of vanadium dioxide integrated into a metasurface comprising gold split‐ring resonators on a sapphire substrate, remarkable control over the amplitude and frequency of quasi‐BIC resonances is achieved due to their high sensitivity to losses present in the system. Breaking the symmetry of meta‐atoms reveals enhanced tunability. The predicted maximum change in the quasi‐BIC resonance amplitude reaches 14 dB with a temperature variation of ≈10 °C.