Enhanced dual-mode terahertz absorption in a graphene-dielectric metasurface by quasi-bound states in the continuum

A graphene-dielectric metasurface driven by quasi-bound states in the continuum (BICs) is proposed for enhanced dual-mode absorption in the terahertz (THz) regime. The graphene-dielectric metasurface is composed of a periodic array of cross-shaped slabs and monolayer graphene. By introducing symmetry perturbation for the cross-shaped slab metasurface, the symmetry-protected BICs transform into quasi-BICs. Subsequently, monolayer graphene is introduced to the cross-shaped slab metasurface to demonstrate the potential of the enhanced dual-mode THz absorption. When the system reaches the critical coupling, each quasi-BIC can achieve the theoretical maximum absorption, with the Q-factor reaching 9033 and 2432, highlighting the unique capacity for tuning and efficient light absorption. This work provides a valuable approach for applications in absorption and manipulation of THz waves.