Theoretical simulation of a dual-band and dual-broadband terahertz metamaterial absorber using two asymmetric rectangular rings

In this paper, a dual-band and dual-broadband terahertz (THz) metamaterial absorber (MA) using two asymmetric rectangular rings is proposed and studied. The proposed bifunctional MA possesses not only the dual-band absorption performance with absorptivities of 97.81% and 99.53% at 2.07 and 2.88 THz but also the dual-broadband absorption performance with absorptivity above 90% in two frequency ranges of 5.74-6.98 and 9.81-10.83 THz. The distributions of electric fields at resonant frequencies are utilized to analyze the working principle of the proposed bifunctional MA. Moreover, the influences of incident angle and polarization angle on dual-band and dual-broadband absorption performance are also investigated. Different from the previous MAs with asymmetric resonators, our bifunctional MA has polarization insensitivity despite the use of two asymmetric rectangular rings. Therefore, our design idea can be effectively utilized in the development of bifunctional MAs with simple structures and polarization insensitivity.