A four-layer planar metamaterial absorber with a Cr-SiO 2 - Si 3 N 4 -Ti stack is presented, featuring a square-patterned top Cr layer, intermediate SiO 2 and Si 3 N 4 dielectric layers, and a bottom Ti substrate. Numerical simulations are performed using the finite-difference time-domain (FDTD) method. The absorber achieves an absorptivity exceeding 90% in the 8.58–16.20 μm band, with an average absorptivity of 96.9% and three absorption peaks at 8.86 μm (99.9%), 9.65 μm (99.9%), and 14.96 μm (99.5%). It exhibits polarization insensitivity at normal incidence (0°–90°) and maintains high absorptivity up to 50° oblique incidence for both TE and TM polarizations. The broadband high absorptivity originates from the synergistic coupling of localized surface plasmon resonance (LSPR), Fabry-Pérot (F-P) cavity resonance, and surface plasmon polaritons (SPPs).
Zhang et al. (Wed,) studied this question.