基于高折射率介质颗粒的环偶极子共振及其在毫米波天线中的应用研究

Recently, artificial constructions of toroidal dipoles have received widespread attentions in the international academic communities. Toroidal dipolar resonances exhibit very special electromagnetic characteristics (e.g., high Q-factor, strong magnetic-field localization), which have potential applications in designs of new photoelectric devices. The states of art of designing toroidal dipoles based on metallic micro/nano structures are relatively mature nowadays. However, the metallic Ohmic loss, which reduces the radiation efficiency of toroidal dipoles, is still inevitable. In this project, the designs of toroidal dipoles are proposed using high-refractive index dielectric particles, and two systems are taken as starting points, i.e., multiple disks and a single torus. In order to enhance the radiation from toroidal dipoles and suppress those from other multipoles, the physical parameters (e.g., geometry, refractive index, etc.) are optimized in this project. Meanwhile, millimeter-wave antennas are designed using periodic arrays of high-refractive index dielectric particles. The impacts of toroidal dipolar resonances on antennas parameters (e.g., Q-factor, radiation efficiency, directivity, etc.) are investigated by numerical simulations and experiments. This project may benefit the investigations of new effects of toroidal dipolar resonances, such as bound states in the continuum (BIC), Fano effect and meta-surface.

近年来，“人工构建”环偶极子的研究引起了国际学术界的广泛关注。环偶极子共振具有非常独特的电磁特性（如：高品质因子、强的磁场局域性），在设计新型光电器件上具有潜在的应用价值。目前基于金属微纳结构“人工构建”环偶极子的技术已相对成熟，但其中无法避免的问题是金属的欧姆损耗会降低环偶极子的辐射效率。鉴于此，本项目拟围绕高折射率介质颗粒，以多个圆盘和单个圆环体这两种体系为切入点构建环偶极子。通过优化物理参数（几何结构、折射率等）力图提高环偶极子辐射效率，并抑制其他多极子的辐射。同时，本项目拟基于高折射率介质颗粒的周期性列阵设计毫米波天线。通过数值仿真和实验手段，研究环偶极子共振对天线的品质因子、辐射效率、定向性等重要参数的影响。本项目工作的开展有助于探索环偶极子共振的新物理特性，如：连续态中的束缚态(BIC)、Fano效应、超表面等。

本项目基于有限元电磁仿真与多极距展开理论，研究了高折射率环形体、圆盘等体系的环偶极子激发特性，以及环偶极子参与的Fano共振、超级散射等物理现象。主要有以下几处研究成果：1）基于高折射率环形体的几何特征，发现了环偶极子型Mie散射，提供了一种简单的环偶极子激发形式。 2）发现环偶极子与其他多极距的叠加可形成超级散射，散射截面远大于单通道极限。3）发现了一种基于环偶极子的Fano共振现象，具有高品质因子与磁场增强的效果。4）揭示了多颗粒体系中环偶极子激发效率与对称性之间的联系。5）发现了基于量子涨落(Casimir效应)的可调控微颗粒悬浮现象。6）发现全介质圆盘之间的耦合存在高品质的电环偶极子模式，为毫米波的天线提供理论参考。