Tri-Band/Ultra-Broadband Switchable Terahertz Metamaterial Absorber Based on Graphene Patches

A tri-band/ultra-broadband switchable terahertz absorber based on graphene patches is proposed in this paper. By changing the bias voltage of the graphene patches, the operating modes of the absorber can be switched between tri-band and ultra-broadband absorption. The simulation results show that the absorption bandwidth can reach 6.34 THz when the mode is ultra-broadband absorption, and the relative bandwidth is 159.3%. The absorption bandwidths can reach 0.73 THz, 0.74 THz, and 0.59 THz, respectively, when the mode is tri-band absorption, and perfect absorption appears at 1.12 THz, 4.12 THz, and 6.86 THz. The absorptance within the absorption bands can exceed 90% in both modes. In addition, the absorber is characterized by polarization insensitivity, and it can maintain high absorptance of greater than 90% with an incidence angle below 40 degrees. The physical mechanisms of the proposed absorber are analyzed by electric field distribution and equivalent circuit theory. We believe the absorber is a potential candidate for terahertz 6G communication and electromagnetic stealth.