Asymmetric all-dielectric metasurfaces supporting quasi-bound states in the continuum for tunable terahertz modulation and ultra-sensitive refractive index sensing

This paper presents the design and investigation of an asymmetric all-dielectric metasurface that supports high quality-factor ( Q -factor) quasi-bound states in the continuum (quasi-BIC) Fano resonances. The structural asymmetry is introduced by varying the dimensions of circular apertures, which effectively excites a series of sharp resonance modes. Multipole decomposition analysis is employed to elucidate their physical characteristics. The effects of incident angle and polarization state on the resonance properties are systematically investigated, and the highly tunable and sensitive response of the structure is confirmed. By incorporating graphene as an active modulation medium, dynamic control of the resonance peak amplitude and frequency is achieved through the adjustment of its Fermi level (chemical potential), offering an effective solution for terahertz modulators and switching devices. Furthermore, the structure demonstrates exceptional performance in the realm of refractive index sensing, with sensitivity and figure of merit values reaching 0.6847 THz/RIU and 4610.6RIU −1 , respectively. These results surpass those of many traditional sensors and indicate significant potential for broad applications.