Design of Narrowband and Broadband Efficient Metamaterial Absorbers in the Long Infrared Region

ABSTRACT A narrowband all‐dielectric absorber capable of covering the long‐infrared band is designed. The structure of this absorber consists of an upper dielectric layer, a lower dielectric substrate, and a reflective layer. The absorption bandwidth of the absorber is 5 µm for an absorption greater than 90%. The absorber demonstrates polarization‐insensitive and large‐angle absorption characteristics in the wavelength range of 6–18 µm. To further broaden the absorption bandwidth, a broadband metamaterial absorber (BMA) was designed, which consists of a top Ti layer, middle and lower Si 3 N 4 dielectric layers, and a substrate layer. The absorption bandwidth of the BMA is 10.5 µm, with an average absorption of up to 92.5% in the 6–18 µm wavelength range. The BMA exhibits polarization‐insensitive and large‐angle absorption characteristics. At a 60° incident angle under TM and TE modes, the average absorption is 89% and 77%, respectively. The high absorption and broadband characteristics of the absorber are mainly attributed to the synergistic effect of localized surface plasmon resonance, propagating surface plasmon resonance, and cavity resonance, which jointly dominate the absorption process. This high‐performance absorber has promising development prospects in cutting‐edge fields such as infrared detection, stealth technology, and sensing.