Metal-Graphene Hybrid Terahertz Metasurfaces Based on Bound States in the Continuum (Bic) and Quasi-Bic for Dynamic Near-Field Imaging

The bound state in the continuum (BIC) and quasi-BIC are widely used in biosensing, lasers, and nonlinear optics due to their strong abilities of light-limiting and high-Q resonance. Most of the work is dedicated to achieving the goal of static conversion between BIC and quasi-BIC, but lacks sufficient attention to their dynamic continuous manipulation. To alleviate this situation, a type of graphene-metal hybrid metasurfaces for BIC and quasi-BIC of terahertz linearly polarized waves are proposed by combining the tunable properties of graphene with the C 2 asymmetry of the structure. The free continuous modulation can be achieved by the Fermi level driven by an external voltage. The transmission amplitude corresponding to the maximum radiation leakage is 0.13. The quasi-BIC can be actively modulated in the modulation range of 0.13 ~ 0.63, and the modulation depth is as high as 0.5. Based on this, the terahertz dynamic near-field imaging of five "UESTC" images with different contrasts is developed and demonstrated. All the features of the electric field intensity and arrow direction show good imaging results. This work provides a new way for the design of terahertz modulators based on metasurfaces, and enriches the applications of BIC and quasi-BIC.