人工分子结构中可调控低损耗的电磁共振机制研究

The electromagnetic interacton in meta-molecules is an important subfield of metamaterials. How to achieve tunable and low loss properties of electromagnetic response is crucial in this field. In this project, based on finite difference time domain (FDTD) method and coupled oscillator model, we explore the novel physical mechanism and manipulation method to solve the above issue. Firstly, by introducing the interaction between localized electromagnetic mode and propagating surface plasmon polariton (SPPs), lattice surface mode, respectively, the controling method based on incidence angle and low radiation, as well as absorption loss for electromagnetic resonances are exptected. Secondly, to manipulate the electromagnetic response in meta-molecules, we propose a possible way based on light intensity due to the interplay between light and nonlinear dielectric in the composite metallic nanostructures. Thirdly, we would investigate how to excite dark mode and suppress the radiation and absorption through designing meta-molecules structure. The method to tune electromagnetic response by polarization of light is also explored. Fourthly, we study the interaction between gain media (such as quantum dot) and meta-atoms in the visible and near-infrared region, to obtain the loss compensation mechanism for the surface wave and localized resonant electromagnetic mode. These works are expected to further elecuidate the interaction laws between light and metallic microstructures and provide knowledge for the development of metamaterials. At the same time, it is valuable to boost the applications of metamaterials in the fields such as biosensor with high resolution,enhanced light emitter.

人工分子结构中的电磁相互作用，是目前超构材料研究的重要分支。如何通过此类相互作用获得动态可调、低损耗的电磁响应性质，是这一领域发展的关键。本项目针对周期阵列的人工分子体系，采取时域有限差分法和耦合谐振子模型，探索解决这一问题的新型物理机制和手段。通过引入传播模式的表面等离极化激元模(SPPs)、晶格表面模与金属纳米粒子局域电磁共振的耦合效应，获得以光波入射角为手段的调控机制和低辐射损耗途径。引入非线性介质，探索基于光强的电磁耦合行为调控依据。设计合适的人工分子耦合体系，揭示低辐射损耗的暗模式激发规律和基于入射光偏振特性的调控方式。探索增益介质与人工分子的相互作用，阐明表面波和局域共振模式在光频至近红外波段能量损耗的补偿机制。研究工作有望进一步揭示光与人工分子结构的相互作用规律，为促进超构材料的发展提供新的知识；这对于推动超构材料在高分辨率纳米传感器、增强发光器件等领域的应用具有现实意义。

本项目针对周期阵列超构分子结构（项目申请书中称为“人工分子结构”）体系，采取时域有限差分法和解析计算，探索电磁共振模式的动态调控和低损耗问题。研究工作中，我们分别探讨了金属微结构和石墨烯纳米结构组成的超构分子中表面等离激元共振模式的动态调控和低损耗的实现途径。具体包括如下：1）探讨了光波偏振对超构分子电磁共振模式的调控和超构分子构形与表面等离激元杂化模式的依赖关系。我们分别设计了平面超构分子和三维超构分子结构，数值计算表明对于平面L形金属纳米粒子与金属纳米棒的复合结构，表面等离激元的杂化共振模式可以灵活地由入射光的偏振态进行“开”或“关”控制。对于三维三聚物超构分子，元胞构形强烈地改变此类杂化模式的共振能级分布，为有效地操控超构材料中的电磁共振频率和共振模式的个数提供了新的自由度；2）分别引入包括表面等离激元和晶格表面模在内的表面电磁波与超构分子的暗模式耦合，实现了高品质因子的共振杂化电磁模和入射角可调控的超构分子表面等离激元共振模式。特别是通过高阶局域表面等离激元与表面波的耦合，获得了高品质因子的共振态，进一步降低了电磁共振模式的辐射损耗。在此基础上，我们将局域表面等离激元与传播表面等离激元的耦合推广到金属与石墨烯复合结构，获得了动态可调的表面等离激元共振模式。3）将超构分子拓展到石墨烯复合周期结构，探索了外加门压和外部磁场对电磁共振模式的动态调控。特别是我们的工作揭示了外磁场作用下超构分子结构的法拉第效应，在保证高透射率的同时透射光的偏振态在外磁场为5T的条件下获得到了近40度的偏振旋转角。. 在项目资助下课题组已发表23篇SCI论文，其中Appl. Phys. Lett., Opt. Express， J. Phys. D: Appl. Phys等SCI二区期刊论文9篇， Plasmonics, Opt. Commun., J. Opt等SCI期刊论文14篇。这些已发表的论文他引总次数达50余次，为超构分子研究领域提供了比较有参考价值的知识和相关纳米光子器件模型。