设计了玻璃基底上的边对边型纳米棒聚合体周期性阵列结构,研究其磁共振机理,并用以实现Fano型共振。在横向激励下,即外加电场垂直于纳米棒长轴时,平面型纳米棒三聚体可实现单次Fano共振,而金属-绝缘体-金属型(MIM)纳米棒聚合体可实现双Fano共振。采用有限元法模拟分析了聚合体阵列在可见光至近红外波段内的近场电磁分布和远场消光谱,研究了其共振峰的特性与实现机理。分析表明,纳米棒局域表面等离激元共振模式的近场耦合与叠加,激发其磁表面等离激元(MSPs),从而得到Fano型共振。尤其MIM纳米棒的引入,为双次乃至多次Fano共振的实现提供更多可能。所设计纳米棒聚合体阵列的Fano共振损耗小,品质高,其带宽仅为30~50 nm,有望应用于多波长生化传感检测、光开关等器件中。

The periodic arrays of edge-to-edge nanorod oligomer on glass substrate are designed to investigate the magnetic resonances and to realize the Fano resonances. With the transverse excitation, that is, the polarized electric field of the incident light is perpendicular to the long axis of the nanorods, the planar symmetric nanorod trimer can obtain a single Fano resonance, while the metal-insulator-metal (MIM) nanorod oligomer can obtain double Fano resonances. The near field electromagnetic distributions and far field extinction spectra of the nanorod arrays are analyzed in visible to the near-infrared regions using finite element method. And the characteristics of its resonance peaks and its realization mechanism are studied. The analysis shows that the near field coupling and superposition of the localized surface plasmon resonance mode of nanorods excite its magnetic surface plasmons (MSPs) to obtain the Fano resonances. In particular, the introduction of MIM nanorods provides more possibilities for the realization of double or even multiple Fano resonances. The Fano resonances of designed nanorod oligomer arrays have the advantages of low resonant loss and high quality with the bandwidth of 30 to 50 nm, which can be potentially used in multi-wavelength biosensor, optical switch and other devices.