▎ 摘　　要

An ultra-broadband terahertz absorber is proposed by a metasurface consisting of coplanar graphene fishnet pattern and gold cross-shaped pattern. The mechanisms of the ultra-broad absorption band of the absorber are that multiple localized surface plasmon resonances are excited in the metasurface and the hybridization of the graphene and gold patterns enhances the field in the metasurface. Besides, the multiple reflections of incidence between the top surface and bottom mirror also enhance the absorbance. The design demonstrates that a band of 90% absorption can be expanded to 8.7 THz with a centric frequency 6.45 THz (134.88%). In addition, the proposed absorber is insensitive to the angle of polarization and it is slightly sensitive to the incident angle. Furthermore, the absorption bandwidth of 85% absorbance can be tuned from 28 THz to 211 THz via changing the bias voltage. The proposed absorber is interesting for the applications of sensing, detecting, and optoelectronic devices.