▎ 摘　　要

We propose a broadband polarization-insensitive absorber based on water and graphene resonators in the terahertz region. The absorption bandwidth of the absorber is effectively broadened by combining water with frequency dispersive permittivity and graphene resonator, which can provide a design reference for broadband metamaterial absorber in the terahertz region. The calculation results indicate that, at room temperature of 300 K, the bandwidth with absorption exceeding 90% of water-based terahertz metamaterial absorber reaches up to 4.50 THz around a central frequency of 6.77 THz at normal incidence, i.e., the relative bandwidth is 66.5%. Compared with the absorber without encapsulated water, the bandwidth with absorption over 90% of the water-based absorber is broadened 57.34%. Interestingly, the frequency dispersive permittivity property of water can not only broaden absorption bandwidth but also contribute to suppressing decline of absorption between adjacent peaks when multi resonance absorptions couple with each other. Furthermore, the proposed polarization-insensitive absorber maintains high absorption over 90% between 4.66 THz and 8.61 THz for the incident angle within 36. and performs stable at room temperature. Therefore, the absorber has potential applications in tunable sensor, thermal detector and terahertz imaging.