Compact Broadband Terahertz Perfect Absorber Based on Multi-Interference and Diffraction Effects

High absorption over a wide frequency band has attracted considerable interest due to its potential applications in imaging and anti-radar cloaking devices. In order to make these devices more integrated, the thickness of the absorber is crucial. In this paper, a compact, polarization-independent, broadband, omnidirectional terahertz (THz) absorber is proposed, fabricated, and evaluated. This THz absorber is based on the combined effect of the multi-interference and diffraction. It is experimentally demonstrated that over 95% absorption can be obtained in the frequency range from 0.75 to 2.41 THz. This well-designed thinner absorber not only reduces the device thickness to 120 μm, but also introduces more interference peaks so that the absorption spectrum is significantly enlarged. Five successive absorption peaks at 0.88, 1.20, 1.53, 1.96, and 2.23 THz are combined into a broadband THz absorption spectrum.