双层美特材料在深亚波长尺度下的近/远场相干调控研究

Manipulating electromagnetic responses of metamaterials via resonance-induced coherence at the deep subwavelength scale has attracted increased attention. Physical models in analogy to quantum interference effects are employed to describe those fascinating effects, including electromagnetically induced transparency (EIT) based on near-field coupling and anti-Hermitian coupling based on continuum-channel-mediated indirect interactions. A recent study has demonstrated novel coherent coupling effect involving both near- and far-field interactions. However, no intuitive model for this effect has been explored. The present project concerns the coherent coupling effects in bi-layer metamaterials among multiple near- and far-field interactions, for instance, nearest-neighbor, next-nearest-neighbor, in-plane, out-of-plane interactions, etc. The study concentrates on coherent coupling models based on analogue of quantum interference effects in multi-atom systems, and related electromagnetic manipulation methods. Metamaterials for novel coherent behaviors, such as decoupled non-radiant resonance and coherent perfect absorption, will be designed, simulated, and experimentally tested. This project may put forward the study of coherent coupling in metamaterials, and pave the way to the design of multi-layer metamaterials.

利用美特材料（metamaterials）在深亚波长尺度下的相干性来调控电磁响应特性是当前的热点研究领域之一。现有的几类主要模型均采用类比量子干涉的方法来进行物理刻画，包括以近场耦合为主导的类电磁诱导透明（EIT）模型、以及以连续态为媒介的间接耦合为主导的反厄米耦合模型等。近年来新发现的基于近场和远场的相干调控行为引起了人们的兴趣，然而目前尚未有直观的物理模型描述。本项目拟深入研究双层美特材料中近场和远场的多元相互作用（包括邻近、次邻近、面内、面外等），建立类比多原子体系量子干涉的相干耦合模型，揭示其内在物理机制，掌握相干调控方法，实现退耦合的非辐射共振效应、完美相干吸收、分频分区域场局域效应等新型电磁调控行为，并完成原理性验证实验。本项目一方面可以作为当前电磁结构相干调控研究的重要补充和拓展，另一方面可以为多层美特材料的设计提供理论指导。

本项目主要针对双层美特材料中的近/远场相互作用进行物理机理的挖掘，基于类量子干涉的思想和耦合模理论，构建了两个谐振腔耦合体系的杂化耦合模型，准确描述了近场和远场相互作用对系统电磁响应和本征谱的贡献。在基本模型的基础上，又分别引入了两束相干光入射的交互作用项和谐振腔偏振状态的自由度，从而实现更丰富的电磁特性调控。在物理模型的指导下，设计了太赫兹美特材料，实现了具有新奇功能的太赫兹调控手段。（1）超薄双层美特材料的相干完美吸收，实现了具有模式和频率选择性的暗态全吸收。（2）双层美特材料偏振态的相干调控，提出通过两束入射光的相位调控可以实现偏振转化的开关效果。（3）双层美特材料PT对称奇异点的高灵敏度探测，提出了具有准PT对称性的双层美特材料在极化空间来分辨小于谐振峰半宽的微小频率劈裂量，从而实现灵敏度近一个数量级的提升。（4）双层有源结构增强的自旋太赫兹源，提出双层有源结构来增强飞秒激光吸收，从而获得太赫兹出射效率的显著提升，最终达到1mm商用ZnTe晶体的水准，可以直接应用到太赫兹时域光谱系统中。