Multiple-band terahertz perfect light absorbers enabled by using multiple metallic bars

Abstract Triple-band terahertz metamaterial absorber with near 100% absorption is suggested in this paper. It is designed by two different lengths of Au bars and an Au substrate separated by an ultra-thin thickness of dielectric spacer. Three separated resonance absorption peaks (labeled A, B, and C) with narrow bandwidths and high absorption rates are realized. The first two peaks A and B are ascribed to the fundamental modes of the two Au bars, respectively, whereas the excitation of 3-order response in the longer Au bar results in the peak C. The field distributions of peaks A, B, and C are provided to verify their mechanisms. Independent frequency modulation of the three peaks (with slight change of absorption strength) can also be achieved, which is different from previous works that changes in parameters affect all absorption peaks. Further structure optimization allows for more absorption peaks, such as quad-band or penta-band. These suggested light absorbers could be designed for potential applications in terahertz technology related fields.