设计了一种基于SU8介质材料的工作波段为20-30微米范围内的的多层超材料吸收器.该吸收器由金属颗粒周期阵列、介质间隔层和金属底层组成.利用LC模型和FDTD数值模拟方法, 通过对SU8介质层厚度、金属颗粒阵列周期、金属颗粒尺寸等参数的优化, 实现了对20-30微米波段范围内入射波的接近100%的完美吸收.并在上述研究基础上进一步设计了具有双层谐振腔的双模完美吸收器.通过数值模拟发现, 由于SU8介质间隔层厚度的增加, 上下两个谐振吸收器可以分别独立实现对特定波长的完美吸收.相应的特征共振吸收波长符合LC模型的预测.同时, 数值模拟结果进一步证实了共振吸收频率与入射角度无关.该完美吸收机制可以归因于入射光在金属底层-SU8介质层-金属颗粒层所组成的谐振腔内多次反射吸收.

A theoretical study on the perfect absorbers working in the far-infrared region with SU8 based multiple-layer metamaterials has been demonstrated. The perfect absorbers consist of periodic array of metal particles, SU8 dielectric spacing layer and a thicker metallic bottom layer. Through the LC model and the finite element numerical simulation methods, we studied the performance of the absorber. With finely tuned parameters, such like the thickness of the SU8 dielectric layers, the periodicity of the metal particles array, and the length of the metal particles, the near perfect absorption up to~100% at the wavelength range between 20 μm to 30 μm for far infrared can be achieved. Based on these results, further design for the double-resonator absorber has been provided. Dual band perfect absorption can be accurately and independently obtained by adjusting the particle size of the upper and the lower metal layers. Moreover, the wavelength of the perfect absorption is also almost independent of the incident angle. These phenomena can be attributed to the multiple reflections between the thick metallic bottom layer and metal particle layers separated by SU8 dielectric layer, which can also be explained using a LC model as the resonant absorption in the metal-dielectric-metal cavities.