Ultra-broadband perfect absorber using triple-layer nanofilm in a long-wave near-infrared regime

Plasmonic absorbers have received considerable attention because of their promising applications in solar cells, controllable thermal emission, and infrared detection. Most proposed plasmonic absorbers are fabricated with a precisely designed surface-pattern, which require complex manufacturing process and are costly. Herein, we propose a simple plasmonic absorber composed of a triple-layer Ti/SiO₂/TiN nanosystem. The maximal absorption reaches 99.8% from 1554 nm to 1565 nm, and an average absorption of 95.3% is achieved in the long-wave near-infrared range (from 1100 nm to 2500 nm). The synergistic effect of the upper surface plasmon resonance and the Fabry-Perot resonance in the Ti/SiO₂/TiN cause the high absorption. Additionally, the effects of the incident angle, polarization state, structural materials, and geometric parameters on the absorption performance are investigated in detail. The proposed near-infrared absorber has potential application prospects in solar collectors, thermal emitters, and solar cells, owing to its high absorption, ultra-broadband bandwidth, insensitivity to incident angle and polarization state, low cost, and simple preparation process.