▎ 摘　　要

Traditional identification tags in the radio or optical domain are unsatisfactory in terms of size and security. In this paper, we theoretically demonstrate an ultracompact and chipless identification tag in the terahertz band using multi-resonant metasurfaces based on graphene. Benefiting from the exceptional electrical and optical properties of graphene, the proposed tags encoding different bit sequences have a uniform geometric shape and size, which is significant for large-scale fabrication processes. Also, their operating frequency could be independently tuned by altering the doping level of each graphene loop without changing their geometric parameters. Tag principles are revealed by absorption spectra and the physical mechanism is investigated with electric field distributions. In addition, we further evaluate the multilayer graphene-based terahertz identification tag for multi-bit coding application, which breaks the spatial constraints in a single layer. Therefore, the proposed terahertz identification tags based on graphene may have remarkable potential values in future chipless identification applications.