Zhang Yao, Yue Peng, Liu Jun-Yan, Geng Wei, Bai Ya-Ting, Liu Shao-Ding
Opt Express. 2019 May 27;27(11):16143-16155. doi: 10.1364/OE.27.016143.
Magnetic resonances generated with nonmagnetic nanostructures have been widely used to design various functional nanophotonic devices, and it is important to realize pure magnetic dipole scattering for the unambiguous study of magnetic light-matter interactions. However, the magnetic responses often spectrally overlapping with other multipoles, which is the main obstacle to achieve ideal magnetic dipole resonances. This study proposes and theoretically demonstrates that an ideal magnetic dipole resonance can be excited with metal-dielectric-metal hybridized nanodisks. It is shown that although the generated magnetic dipole scattering around the bonding resonance of the hybridized nanodisk is spectrally overlapping with strong electric dipole and electric quadrupole contributions, an almost perfect current loop can be generated by adjusting the geometry parameters and the refractive index of the dielectric layer, thereby leading to the suppressing of the overlapping multipoles and the formation of an ideal magnetic dipole scattering. What's more important is that both electric and magnetic near-fields are enhanced simultaneously with the increasing of the refractive index of the dielectric layer, which makes the hybridized nanodisk a promising platform for enhanced magnetic light-matter interactions.
由非磁性纳米结构产生的磁共振已被广泛用于设计各种功能纳米光子器件，对于明确研究磁光物质相互作用而言，实现纯磁偶极散射非常重要。然而，磁响应通常在光谱上与其他多极重叠，这是实现理想磁偶极共振的主要障碍。本研究提出并从理论上证明，金属 - 介质 - 金属杂化纳米盘可以激发理想的磁偶极共振。结果表明，尽管在杂化纳米盘的键合共振周围产生的磁偶极散射在光谱上与强电偶极和电四极贡献重叠，但通过调整几何参数和介电层的折射率，可以产生几乎完美的电流环，从而导致重叠多极的抑制和理想磁偶极散射的形成。更重要的是，随着介电层折射率的增加，电近场和磁近场同时增强，这使得杂化纳米盘成为增强磁光物质相互作用的有前途的平台。
