▎ 摘　　要

In this article, first, using conventional graphene-dielectric-metal layers, we have achieved a perfect dual-band terahertz absorber. The obtained results indicate that there are two absorption bands of 97.66% and 98.64% ranging in 5.45 and 7 THz, respectively. Then, the electric fields of this structure at the desired frequencies are also shown to understand the absorption mechanism better. Next, due to the symmetry in the structure relative to the center of the shape coordinate, by adding another layer, a nearly perfect quad-band absorber is obtained. Also, this model of structure has four absorption bands with peaks of 84.4%, 95.6%, 99.2% and 96.12% at frequencies of 4.15, 5.14, 5.58 and 7.35 THz, respectively. Usually, in multi-band structures, the average percentage of absorption bands is expressed, which in the proposed structure is 93.83%. Another interesting advantage of the proposed structure is that the absorption rate is insensitive to wave polarization changes. This structure, in addition to insensitive to being polarization, has a wide incident angle too. This structure can be used in sensor, photodetectors and imaging applications due to perfect absorption rates and multi-band capability.