Tunable High-Q Resonance Based on Hybrid Phase-Change Metasurfaces

High-Q resonances based on metasurfaces have attracted widespread attention in recent years for enhancing light–matter interaction at the nanoscale. Particularly, bound states in the continuum provide a fascinating method for generating the high-Q resonances. However, the resonant wavelengths of most high-Q metasurfaces are fixed once they are fabricated. Here, we numerically demonstrate a tunable high-Q resonance by integrating a silicon metasurface with the phase-change material Ge2Sb2Te5. The hybrid metasurface can support both a magnetic dipole resonance and a toroidal dipole resonance. Notably, the toroidal dipole resonance can be converted into bound states in the continuum by adjusting the geometric parameters. Moreover, the wavelength of the high-Q toroidal dipole resonance can be dynamically tuned through the phase transition of Ge2Sb2Te5. In addition, a high-Q analogue of electromagnetically induced transparency is also numerically realized through the interaction between the magnetic dipole mode and toroidal dipole mode and can be switched off by the phase transition of Ge2Sb2Te5. The tunable high-Q metasurfaces have potential applications in nonlinear enhancement, biosensors, and slow-light devices.