Multiband, polarization-insensitive absorber operating in the terahertz range

In this study, we analyze a thin-size metasurface-based multiband terahertz (THz) absorber with a top layer comprised of nickel-made circled plus-shaped resonators. The geometric structure of the proposed absorber consists of subwavelength size and periodically arranged nickel resonators at the top followed by substrate SiO₂ film, and the silver layer at the bottom features several high absorption bands within the 1–5-THz operating range. The proposed multiband THz absorber shows excellent absorption characteristics with perfect absorptivity, 100% at 1.5 THz, 98% at 3.2 THz, 96% at 3.72 THz, and 100% at 4.26 THz, respectively. The symmetry in the top-layer design of the unit cell shows persistence to incident waves with different polarization and makes this device independent of variation in the polarization of the waves. Besides that, surface current density analysis of the absorber illustrates that high absorption bands are achieved due to the existence of strong electric resonance in the unit cell structure. It is believed that the proposed multiband terahertz absorber with high absorption characteristics and polarization-independent behavior can be used in the field of THz shielding, THz detectors and emitters, THz sensing, and thermal imaging.