介电-金属多层膜结构宽谱吸收器设计方法

Designing Broadband Absorbers Based on Dielectric-Metal Multilayer

本论文针对介电-金属多层周期结构提出设计宽谱完美吸收器的方法。该方法在不同波长区域分别使用布洛赫理论和等频率面的光学拓扑来调控吸收谱的起始以及终止波长。利用本设计方法,设计并制备了一个在可见光和近红外波段(0.4～2μm)高吸收的宽谱吸收器。理论计算和实验测量的平均吸收谱高达95%左右。为了进一步分析本方法的物理机制,本文利用导纳分析绘制了导纳图进行说明,随着层数的逐渐增加多层结构的导纳逐渐和真空中的导纳相匹配。本文设计的完美吸收器无需刻蚀等工艺,对于太阳能收集、辐射制冷、热成像等领域具有潜在应用价值。

In this paper, we propose a method to design broadband near-perfect absorbers consisting of a periodic dielectric-metal multilayer. In the method, the Bloch theorem and optical topological transition（OTT） of iso-frequency surfaces are employed to manipulate the start and end of the near-perfect spectral absorption band, respectively. We design and fabricate a broadband near-perfect absorber utilizing the proposed method. The average absorption of the designed absorber is about95% in the focused visible and near-infrared range（0.4-2μm）. Moreover, admittance analyses are employed to reveal the mechanism of the near-perfect absorption. By increasing the number of periods of the dielectric-metal layer gradually, the admittance change towards matching the free space admittance. This lithography-free near-perfect absorber is promising for solar energy harvesting,radiative cooling, and thermal imaging.