A dual-directional metamaterial perfect absorber base on Al2O3 etched cross cavity in the visible and near-infrared ranges

Abstract

Due to their unique properties, metamaterial perfect absorbers have been widely used in such fields as solar energy absorption, seawater desalination, sensing and so on. Recently, ultra-wide band perfect absorbers and multi-narrow band perfect absorbers are studied and reported. However, there are a few researches on metamaterial perfect absorbers with both narrow-band and wide-band absorption properties. In this paper, we propose a dual-directional perfect absorber which can switch between wide band absorption and narrow band absorption. It consists of a multi-layer planar structure topped by a pattern layer being arranged periodically. In the wavelength range of 600 nm to 2000 nm, when the incident light is vertically incident from the upper surface of the structure, there will be three resonance absorption peaks, locating at 863 nm, 875nm and 1135 nm, and the absorption rates will reach to 99.51%, 99.61% and 99.58%, respectively. The analysis demonstrates that the structure has good sensing performance in the environment of different refractive index. When the incident light is incident from the lower surface of the structure, the absorber exhibits broadband absorption with an average absorption rate of 98.04% (600 ∼ 2000 nm). When the temperature reaches 1000 K, the total photothermal conversion efficiency of the absorber can still reach more than 92%. In addition, our research shows that the structure is independent of polarization. All these features promise for our proposed dual-function perfect absorber to realize diverse applications in the fields of sensing, detection, sunlight acquisition, optical conversion devices, and so on.