用于太赫兹天文探测的新型滤波器件研究

Nowadays, it is significant to achieve a narrow bandpass filter (FWHM<10%) with high transparency (T>90%) for submillimeter astronomy. In order to solve this problem, we propose a novel terahertz filters based on fractal physics and Babinet principle. The novel filter is made of self-similar complementary electromagnetic resonator on the both sides of flexible polymer substrate. In combination of the function of interference filter, the proposed metamaterials-based THz bandpass filter is satisfied with aforementioned technical specifications. Therefore, it is necessary to solve the most critical scientific problems: the relationship between the coupling mechanism between variable fractal structure and the resonant modes, such as high Q factors and transmittance maximum. This problem will be systematically realized via theoritical modelization and experiment, such as the dynamics mechanism between Hausdorff fractal dimension of unit cells and terahertz electromagnetic resonance; the polarization-sensitive features and symmetry of different fractal structures; The influence of substrate and metal structures on THz modulation depth; The enhancement of resonance modes in the bilayer structure of the filter owing to the interference effect. Finally, the scientific reports and prototype devices are expected to provide significantly technical support for the research of submillimeter astronomy in China.

具有高透射率（最大透过率>90%）和窄通频带宽（半高全宽<10%）的太赫兹滤波器，是当前亚毫米波天文研究急需的关键器件之一。本项目根据分形几何结构对电磁场的调制作用结合Babinet原理，创造性地提出基于柔性分形结构干涉滤光型窄带通滤波器件，从而满足天文探测需求。要达到上述技术指标，就必须系统地解决二维平面和三维空间上，分形结构对太赫兹电磁谐振模式相互作用机制这一关键科学问题。本项目通过设计、制造、测试原型器件，结合电磁场数值模拟建立物理模型，系统地阐述分形单元的Hausdorff维数与太赫兹电磁共振的动力学机理；中心对称结构与轴对称结构对不同频率偏振敏感的特性及其物理机制；不同金属微结构与柔性衬底介电环境对太赫兹波调制深度的影响；谐振模式在双层结构下的干涉效应对提高透射率的机理等科学问题。最终成果有望为我国亚毫米波天文学研究提供重要的技术支撑。

通过研究通过研究不同分形结构、不同Hausdorff维度下电磁谐振单元在不同耦合方式下，最大谐振强度和谐振带宽之间的关系及其产生机制。分形结构空间对称性与太赫兹波段电磁波的电磁对称性之间的关系，分形结构共振单元的Hausdorff维度与响应带宽的关系。揭示电偶极子振荡、磁偶极子振荡、电四极子振荡、电容-电感振荡之间相互耦合的动力学机制；重点研究近场耦合与导电耦合对改变谐振模式的主要效果差异，为提高太赫兹滤波器的通频带宽提供理论依据。不同分形结构的共振单元上电磁场在2维空间上的分布呈现规律，以及太赫兹波激发类表面等离子体以及引起的表面电流特性，结果实现最大透过率提高到90%以上，通频带宽压缩到中心谐振频率两侧±10%以内的太赫兹滤波器，满足下一代太赫兹超导探测器在天文观测中的应用需要。