结合多层波导结构与杂化耦合理论,设计了一种宽波段、高吸收率的多层矩形吸收器。该吸收器由矩形缝隙天线与多层金属-介质-金属矩形结构组成,采用时域有限差分方法分析了该吸收器在宽波段、不同偏振状态以及大角度斜入射条件下的吸收特性。数值分析结果表明,该吸收器在400~1400 nm波段的平均吸收率可达95%,呈一定的偏振不敏感特性,且60°斜入射时仍能保持93%的平均吸收率。通过监测谐振频点下的电磁场分布,发现该吸收器的宽波段高吸收特性主要由法布里-珀罗共振、慢波效应、局域表面等离子体共振及他们之间的杂化耦合作用决定。这种宽波段、高吸收、对偏振与斜入射角度不敏感的吸收器,有望在隐形设备、太阳能电池等领域发挥重要的作用。

A multilayer rectangular absorber with wide band and high absorption rate is designed based on multilayer waveguide structure and hybrid coupling theory. The absorber unit is composed of a rectangular slot antenna and a multi-layer metal-dielectric-metal rectangular structure. We use finite-difference time-domain method to analyze the absorption characteristics of the multilayer rectangular absorber under the conditions of wide band, different polarization states and large angle oblique incidence. Numerical results reveal that the absorption band of the absorber is 400--1400 nm, and its average absorption rate can reach 95%, showing a certain polarization insensitivity, and it can still maintain an average absorbance of 93% at 60° oblique incidence. By monitoring the electromagnetic field distribution at the resonance frequency point, we find that the high-absorption characteristics of the absorber in a broadband which is mainly caused by Fabry-Perot resonance, slow-wave effects, local surface plasmon resonance, and the hybrid coupling among them. The proposed metamaterial absorber is expected to play a role in invisible devices, solar cells and other fields owing to its wide bandwidth, high absorption, insensitivity to polarization and oblique incidence angle.