Yao Jin, Li Bin, Cai Guoxiong, Liu Qing Huo
Opt Lett. 2021 Feb 1;46(3):576-579. doi: 10.1364/OL.415423.
Anapole mode is a nonradiative resonance originating from the destructive interference between co-excited Cartesian electric dipole and toroidal dipole moments. With at least two symmetric circulating currents, the anapole mode in all-dielectric nanoresonators provides the opportunity to operate the double perfect electric conductor (PEC) mirror effects. In this work, unlike the conventional metal-dielectric-metal (MDM) nanostructure generating a plasmonic magnetic resonance, two metal components are employed to produce the fictitious images of the middle dielectric, and the whole system can thus excite the doubly mirror-induced anapole mode. Electric anapole mode and its magnetic counterpart are, respectively, investigated in two types of MDM configurations according to their own symmetric characteristics. Benefiting from the double PEC mirror effects, the doubly mirror-induced electric and magnetic anapole modes possess the larger average electric-field enhancement factors (9 and 56.9 folds compared with those of the conventional ones, respectively), as well as the narrower line widths. This work will pave a new way for tailoring and boosting anapole modes in metal-dielectric hybrid nanoresonators and open up new opportunities for many significant applications in nonlinear and quantum nanophotonics.
无偶极子模式是一种非辐射共振，它源于共激发的笛卡尔电偶极子和环形偶极矩之间的相消干涉。全介质纳米谐振器中的无偶极子模式具有至少两个对称的循环电流，为实现双理想导体（PEC）镜面效应提供了机会。在这项工作中，与产生等离子体磁共振的传统金属-介质-金属（MDM）纳米结构不同，采用两个金属组件来产生中间介质的虚拟图像，从而整个系统能够激发双镜面诱导的无偶极子模式。根据其自身的对称特性，在两种类型的MDM结构中分别研究了电无偶极子模式及其磁对应模式。受益于双PEC镜面效应，双镜面诱导的电和磁无偶极子模式具有更大的平均电场增强因子（分别比传统模式大9倍和56.9倍）以及更窄的线宽。这项工作将为在金属-介质混合纳米谐振器中定制和增强无偶极子模式开辟一条新途径，并为非线性和量子纳米光子学中的许多重要应用带来新机遇。
