太赫兹滤波器在成像、光谱技术及传感等领域有着广泛的应用。提出并制备了一种基于三个方形封闭谐振环(CRR)结构的太赫兹多频带滤波器。利用时域有限差分法分析了共振峰产生的机理，讨论了CRR结构尺寸与共振频率之间的关系。三个CRR滤波器共振峰的产生除了有自身电场耦合作用和相邻环间的磁场耦合作用外，还有内、外环的作用。对所制备的滤波器进行了透射性能测试，获得该滤波器三个共振峰的中心频率分别为0.33、0.68、1.13 THz，实验结果与仿真设计基本相符。

Terahertz filter can be used for various applications such as imaging, spectroscopy and sensing. We propose and fabricate a terahertz multiband filter using three nested closed-ring resonators (CRRs) on polyimide substrate. We numerically analyze the physical origin of the multispectral response and discuss the dependence of the resonance frequencies on the geometrical parameters of the closed rings. It is found that the three resonant peaks of the proposed filter originate from not only the dipole electric response of the three rings and the magnetic response between the adjacent rings, but also the effect from inner or outer CRR. The performance of the filter is measured by terahertz time-domain spectroscopy (TDS), and the experimental results show three distinct resonant peaks at 0.33, 0.68, 1.13 THz, which are in good agreement with simulations.