Ultra-broadband terahertz absorber based on double truncated pyramid structure

Terahertz (THz) absorbers have attracted considerable attention due to their potential applications. However, the limited bandwidth of THz absorbers limits their further applications. To achieve ultra-broadband and high absorption characteristics in the THz band, a double truncated pyramid unit structure combining the hybrid planar structure and the few-layers vertical structure is proposed. The double truncated pyramid structure composed of five metal layers and five graphene layers has the advantages of ultra-broadband, tunability, polarization-insensitive and wide-angle absorption. The simulation results show that the absorption coefficient of the absorber is over 0.9 from 1.49 THz to 12.72 THz. The double truncated structure provides perfect ultra-broadband absorption, which can be attributed to the localized surface plasmon and surface plasmon. The mechanism of resonance can be further explained by surface current distribution. Meanwhile, the absorption mechanism of the absorber can also be explained by the impedance matching theory. The proposed THz absorbers have potential applications in sensing, stealth and other multispectral devices.