A Metasurface Dual-Band Cut-Off Perfect Absorber for Visible and Near-Infrared Bands

Metasurface cut-off perfect absorbers (MCPAs) are of great significance in technology. Research on MCPAs is extensive, whereas that on metasurface dual-band cut-off absorbers (MDCPAs) remains relatively scarce. An MDCPA operating in the visible and near-infrared (NIR) bands is proposed. This absorber realizes dual-band cut-off perfect absorption by integrating a bottom silver (Ag) layer, a silicon nitride (Si3N4) layer, Ag cylinders embedded with alumina (Al2O3) cylinders, and Al2O3 fan-shaped pillars. Finite-difference time-domain (FDTD) simulation calculation indicates that the absorber achieves polarization-independent high absorption (average 0.956) in the 676 nm–872 nm band and low absorptions (averages: 0.075 and 0.019, respectively) in the 400–600 nm and 980–1400 nm bands. We also use electromagnetic multipole decomposition, which is combined with electromagnetic field diagrams, to explain the origin of the dual-band cut-off absorption. This work proposes an effective strategy for realizing a high-performance MDCPA in the visible and NIR bands. With high cut-off sharpness and absorption contrast, the proposed MDCPA exhibits significant application potential in advanced nanophotonic devices and systems.