基于人工等离激元结构的高阶Fano共振特性研究

Fano resonances produced in plasmonic structures have broad application prospects in sensing, slowing light, light switch, nonlinear optics, and filtering. The Fano resonances include two types of lower-order Fano resonances and higher-order Fano resonances. Compared with the lower-order Fano resonances, the higher-order Fano resonances generally have narrower spectra, which imply that the resonances probably possess more superior performances in many applications. Presently, considerable research is done on the lower-order Fano resonances rather than the higher-order Fano resonances. Besides,some new physical phenomena produced in the higher-order Fano resonances need to be explored and their corresponding mechanisms also need to be disclosed. In this project, the higher-order Fano resonances produced in plasmonic structures will be systematically investigated. The project will be carried out following three aspects, namely, the higher-order Fano resonances based on electric plasmonic structures, the higher-order Fano resonances based on magnetic plasmonic structures, and the higher-order Fano resonances based on electric and magnetic coexisting plasmonic structures. During the processes, we will analyze in detail and systematically investigate the forming progresses, the couplings between lower-order and higher-order modes, and the hybridizations between different higher-order modes in the three kinds of higher-order Fano resonances. Our object is to clarify the characteristics of the resonances and reveal their physical mechanisms, offering theoretical bases for their potential applications.

基于等离激元结构的Fano共振在传感、慢光、光开关、非线性光学和滤波等方面具有广泛的应用前景。它包括低阶Fano共振和高阶Fano共振两种形式，与低阶Fano共振谱相比，高阶Fano共振谱宽更窄，该特性决定了高阶Fano共振在诸多应用方面可能更具优越性。目前，研究者们更多地研究等离激元结构中的低阶Fano共振，而对该类结构中的高阶Fano共振却研究很少，并且，未知的高阶Fano共振中还会存在一些新的物理现象以及还需要用新的物理机制去诠释这些现象。本项目将系统全面地对电等离激元、磁等离激元和电磁共存等离激元三类结构中的高阶Fano共振特性进行研究。在此过程中，将对结构中的高阶Fano共振的产生过程、低阶模与高阶模之间的耦合过程、各高阶模之间的杂化过程等进行系统地分析和研究，弄清共振特性，揭示物理机理，为共振的可能应用提供理论依据。

基于等离激元结构的Fano共振在传感、慢光、光开关、非线性光学和滤波等方面具有广泛的应用前景。它包括低阶Fano共振和高阶Fano共振两种形式，与低阶Fano共振谱相比，高阶Fano共振具有独有的特性，该特性决定了高阶Fano共振在诸多应用方面可能更具优越性。课题组主要研究了如下几个方面。（1）研究由庞磁阻构成的电等离激元和磁等离激元结构的高阶Fano共振。发现改变外加在结构上的磁场强度能够调控Fano共振强弱，从而实现了对高阶Fano共振的主动调谐。当外磁场的强度变化时，该结构透射谱的相位也受到较大的调谐，这种调谐方法在可控光电元件中有潜在的应用。（2）研究了环型等离激元结构的高阶Fano共振。研究结果显示这些结构具有品质因数非常高或是谱线非常窄，根据这一特点，可以设计出一款高灵敏折射率传感器。（3）研究了杆型等离激元结构的高阶Fano共振。研究结果显示不对称的等离激元结构具有方向极化敏感特性。利用此性质可设计成极化控制开关。对称的等离激元结构在强的光吸收、电磁诱导透明等特性方面展现出方向不敏感性。利用此性质，可设计成各向同性光电元件。