Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
Nanoscale. 2017 Sep 14;9(35):13222-13234. doi: 10.1039/c7nr04524g.
Plasmonic Fano resonance arises from the destructive interference between a superradiant and a subradiant plasmon mode that overlap spectrally with each other. Because of its importance in revealing many physical phenomena and its applications in sensing, metamaterials, photoswitching and spectroscopy, a variety of metal nanostructures have been fabricated to generate Fano resonance. However, few metal nanostructures can support deep Fano resonance with strong polarization dependence. Herein, we report on the observation of deep Fano resonance with strong polarization dependence in Au nanoplate-nanosphere heterodimers. Experiments and simulations reveal that the presence of a nanosphere at one side edge or one vertex of the nanoplate causes distinct Fano resonance. With increasing nanosphere sizes, the shape of the scattering spectrum becomes more asymmetric, with the Fano dip getting deeper correspondingly. When the nanosphere diameter reaches 68 nm, the Fano dip almost reaches the spectral background. Moreover, the heterodimers with the nanosphere attached to one vertex of the nanoplate exhibit Fano resonance with strong polarization dependence. Such heterodimers are very attractive for constructing polarization-controlled plasmonic Fano switches.
等离子体 Fano 共振源于超辐射和亚辐射等离子体模式之间的破坏性干涉，这些模式在光谱上相互重叠。由于其在揭示许多物理现象及其在传感、超材料、光开关和光谱学中的应用中的重要性，已经制造了各种金属纳米结构以产生 Fano 共振。然而，很少有金属纳米结构能够支持具有强偏振依赖性的深 Fano 共振。在此，我们报告了在 Au 纳米板-纳米球异质二聚体中观察到的具有强偏振依赖性的深 Fano 共振。实验和模拟表明，纳米球位于纳米板的一侧边缘或一个顶点处会导致明显的 Fano 共振。随着纳米球尺寸的增加，散射光谱的形状变得更加不对称，相应地，Fano 凹陷变得更深。当纳米球直径达到 68nm 时，Fano 凹陷几乎达到光谱背景。此外，纳米球附着在纳米板顶点的异质二聚体表现出具有强偏振依赖性的 Fano 共振。这种异质二聚体非常适合构建偏振控制的等离子体 Fano 开关。
