多频段超材料完美吸波器的设计在多色光学领域具有重要意义。提出一种多频段金属-绝缘层-金属超材料吸波器,其表面电磁响应单元为三圈嵌套的金属环阵列,采用时域有限差分方法计算结构单元的吸收光谱和电磁场密度分布。结果表明:该结构单元在1.44,2.28,3.25 μm处分别实现了98.5%、99.6%和99.9%的吸收率,物理机理为磁激元共振激发。系统分析结构几何参数对共振的影响,通过改变金属环的直径和高度,可以对不同的共振进行独立调控。该结构单元的吸收光谱对入射光极化角度具有良好的稳健性。并进一步分析了超材料吸波器的传感特性,其最大品质因数高达8.3 RIU ^-1(RIU为折射率单元),对应的灵敏度为1.08 μm·RIU ^-1,表现出优良的红外传感性能。该吸波器可应用于传感领域,亦可为其他超材料的设计带来新启示。

The design of multi-band metamaterial perfect absorbers is of great significance in the field of multi-color optics. In this study, a multi-band metal-insulator-metal metamaterial absorber is designed. Its surface electromagnetic response unit is a three-loop nested metal ring array. The finite-difference time-domain method is used to calculate the absorption spectra and electromagnetic field density distributions of the unit. The results show three absorption peaks at 1.44, 2.28, and 3.25 μm with maximal absorptivity of 98.5%, 99.6%, and 99.9%, respectively. The physical mechanism for these peaks is ascribed to the excitation of magnetic polaritons. The influence of the structural geometric parameters on the resonance is systematically analyzed. By altering the height and outer diameter of metal rings, different resonance wavelengths can be independently tuned. The absorption spectra of the structure are very robust to the polarization angle of incident light. In addition, the refractive index infrared sensing performance of the metamaterial absorber is examined. It is found that the structure exhibits excellent performance for refractive index sensing. The maximum figure of merit can reach 8.3 RIU -1(RIU is the refractivity unit), and the corresponding sensitivity reaches 1.08 μm·RIU -1. The proposed absorber can be applied to the sensing field and provide new insights for the design of other metamaterials.