Ultra-broadband metamaterial absorber in the near-infrared to mid-infrared region

Metamaterial broadband absorbers with high absorption, strong resistance to environmental changes, and ease of configuration are in significant demand across a number of practical applications. In this paper, we design a novel metamaterial broadband absorber with a structure composed of vertically arranged subwavelength metal-dielectric-metal resonators. The calculation results show that within the infrared wavelength range of 1.7-8.7 μm, the absorber achieves an efficient absorption exceeding 90%, with an average absorption as high as 98%. Notably, this structure attains nearly perfect ultra-high average absorption (99.3%) within the wavelength range of 2-8 μm. In-depth analysis of the absorber's physical mechanism confirms that its broadband high absorption arises from the synergistic enhancement induced by both surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). Meanwhile, this structure exhibits excellent wide-angle absorption capability. Specifically, when the incident angle increases from 0° to 65°, the average absorption across the entire wavelength band consistently remains above 90%, highlighting its robustness under oblique illumination conditions. Furthermore, this structure demonstrates a high degree of adaptability to environmental changes. When the refractive index of the surrounding environment (medium/air) varies, the system can still maintain stable and efficient absorption performance, proving its resilience against environmental fluctuations. These advantages further enhance the reliability and durability of the absorber, ensuring its optimal performance under various potential harsh conditions.