Design, simulation, and analysis of an ultra-broadband polarization-insensitive terahertz metamaterial absorber

A novel ultra-broadband polarization-insensitive metamaterial absorber is presented in this paper, which can work in the terahertz (THz) regime. By stacking two layers with a certain proportion separated by dielectric spacing layers, on which six nested rings of different sizes and other metal resonators are arranged, the metamaterial absorber for a TE wave can achieve absorption of over 90% at 2.28–5.58 THz, and that for the TM wave is located at 2.3–5.82 THz, whose relative bandwidths (RBWs) are 82.5% and 88%, respectively, which is shown in the simulation results. Moreover, the absorption performance of such an absorber remains stable at 2.3–5.58 THz, whose RBW is 82% when the wave is incident with different polarization angles, which implies that the metamaterial absorber has insensitivity towards polarization. The absorption mechanism for this absorber originates from the Fabry–Perot resonances among different layers and the magnetic resonances among the metal resonators, based on analysis of the distributions of the power loss density, surface current, and magnetic fields. The metamaterial absorber presented in this work is promising for application owing to its broad absorption band and insensitivity towards polarization.