环偶极子超介质的广义多极子等效介质理论及电磁透明机理研究

Toroidal dipoles are ubiquitous in nature structures such as DNA. It is possible to achieve toroidal dipoles in microwave or optical regions as the research of metamaterials move along. Their novel electromagnetic oscillating and transparent effects can be used for the designing of low threshold lasers, biological sensors, optical storage devices and so forth. Therefore, the application prospect is very broad. In this project, we will firstly build models with toroidal dipolar response by suppressing conventional electromagnetic multipoles, taking the flexible and controllable advantages of metamaterials. This can provide theoretical and experimental basis for the analysis of toroidal dipoles. Then we establish a generalized multipole effective medium theory by calculating scattered power of conventional electromagnetic multipoles together with toroidal dipoles. The aim is to establish the relationship between microscopic coupling mechanism and macroscopic electromagnetic properties. It can fundamentally solve multi-valued problems and unphysical phenomena that exist in S-parameter retrieval procedure. Finally, we will describe the relationship between the multipoles' scattered powers, coupling effect and resonant characteristics by the means of generalized multipole effective medium theory. This can provide an effective way to reveal the physical mechanism of the toroidal induced electromagnetically transparency. This project is an important exploration on electromagnetic theoretical research of toroidal metamaterials. Notably, the proposed generalized multipole effective medium theory and quantitative analysis of electromagnetically transparency provide new ideas on metamaterials designing and characteristic analysis.

磁环偶极子广泛存在于诸如DNA等物质结构中，随着电磁超介质的深入研究，在微波或光学频段实现环偶极子效应成为可能，其新颖的电磁振荡与透明效应有望实现低阈值激光器、生物传感器和光存储器等器件设计，应用前景十分广阔。项目首先利用电磁超介质的灵活性与可控性，克服传统电磁多极子干扰，构建磁环偶极子效应的超介质模型，为研究其特性奠定理论和实验基础。接着，计算包含磁环偶极子在内的多极子散射功率，形成广义多极子等效介质理论，建立微观耦合机制与宏观电磁特性两者间联系，从根本上解决S参数反演中存在的多值性问题和非物理现象。最后，利用多极子等效介质理论，揭示不同多极子散射功率大小以及互耦效应与谐振特性的关系，阐明磁环偶极子产生电磁透明的物理机理。本项目是对环偶极子超介质电磁理论研究的一次重要探索，所提出的广义多极子等效介质理论和电磁透明机理定量分析方法，是一条对超介质设计及特性分析具有普遍指导意义的新思路。

磁环偶极子广泛存在于诸如DNA、蛋白质等自然物质结构中，而电磁超介质微结构建模，在微波（或光学）频段增强环偶极子效应，使其达到可探测的量级，为研究其与电、磁、光性质相关联的信息元件的突破提供了一个全新的研究方法。本文通过抑制传统偶极子和其它多极子响应，增强环偶极子效应，研究不同多极子散射功率与等效电磁参数以及宏观电磁特性之间的关系。通过传输特性分析、多极矩散射能量对比、表面电流分布、电磁场分布、能耗分布、多极子耦合等多种研究方法，提出并实验验证了几种环偶极子超介质模型，包括立体矩形开口谐振环电/磁环偶极子模型、电环偶极子模型、平面不对称开口谐振环磁环偶极子模型等，着重研究了基于环偶极子效应的电磁透明特性。除此以外，对相关电磁超介质的小型化吸波和手征负折射率特性也完成了相关理论和实验研究。研究结果表明，无论是立体结构还是平面结构，通过电磁微结构的超介质构建环形偶极子的方法是可行的，基于其的电磁透明特性也具备高Q值、极化转化、不受基底介质损耗影响以及高灵敏度等特性。其应用前景广阔，包括THz频段、红外波段、可见光波段的超介质设计，在微型测辐射热仪、探测器、高灵敏度传感器及医学成像等领域，有着重要的应用价值。