In this paper, we perform a theoretical investigation of the plasmon coupling in silver (Ag) nanocube–nanosphere dimer using finite difference time domain (FDTD) technique. Due to plasmonic Fano resonance, we observe a pronounced dip in the absorption spectrum, which is induced by the destructive interference between the bright dipole mode from the Ag nanocube and the dark quadrupole mode from the Ag nanosphere. We study the effects on the Fano resonance by varying the dimensions of the nanocube and nanosphere, as well as the inter-surface gap distance between them. In addition, we vary the local dielectric environment surrounding the dimer and find a wide tuning in the Fano resonance line-shape. We calculate the localised surface plasmon resonance (LSPR) sensitivity of the nanocube–nanosphere dimer to the surrounding environment and find a high figure of merit (FOM) of 32.23, which indicates its promising potential as a plasmonic biosensor.

中文翻译：

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银纳米立方体-纳米球二聚体中法诺共振的观察

在本文中，我们使用有限差分时域 (FDTD) 技术对银 (Ag) 纳米立方体-纳米球二聚体中的等离子体耦合进行了理论研究。由于等离子体法诺共振，我们观察到吸收光谱的明显下降，这是由银纳米立方体的亮偶极子模式和银纳米球的暗四极子模式之间的相消干涉引起的。我们通过改变纳米立方体和纳米球的尺寸以及它们之间的表面间隙距离来研究对法诺共振的影响。此外，我们改变了二聚体周围的局部介电环境，并在 Fano 共振线形状中发现了广泛的调谐。