Fig. 1. (a) Schematic view of the proposed graphene metasurface, where the width of graphene strip w = 300 nm, length a = 650 nm, period L = 900 nm, and the polarization is along the x axis. (b) Dispersion map of absorption with different spacings d offset by unity for clarity. (c) Simulated absorption spectra as a function of separation d between graphene strips and frequency.

Fig. 2. Localized field distribution 2D plot at 38 THz with different spacings: (a) d = 150 nm, (b) d = 100 nm, and (c) d = 50 nm in the hybridized mode. (d) Indication of the electric dipole (ED) moment and the orthogonal magnetic dipole (MD) moment involved with the super-radiant state and the quasi BIC, respectively.

Fig. 3. (a) Q-factor and band structure of BIC mode in the graphene metasurface. (b) Level scheme for the resonances in a schematic three-level system. The super-radiant mode is indicated by blue and the BIC-based mode by green.

Fig. 4. Absorption spectra and localized field distribution at resonances around 38 THz. (a) Symmetry-protected BIC composed of vertically aligned graphene strips. (b) Quasi BIC via breaking symmetry. (c) Super-radiant (bright) mode composed of horizontal graphene strips. (d) Three-level system for multi-line spectrum via hybridization.

Fig. 5. (a) Absorption spectra versus different relaxation times. (b), (c) Dispersion maps with different lengths and widths of graphene strips. The separation between graphene strips is 45 nm.

Fig. 6. Simulated absorption spectra as a function of polarization angle ϕ and frequency with 45 nm separation between graphene strips.