标题： 负载二聚体间隙天线中等离激元腔模引起的散射增强与抑制共存 显示英文标题

标题： Coexistence of Scattering Enhancement and Suppression by Plasmonic Cavity Modes in Loaded Dimer Gap-Antennas

摘要： 等离子纳米天线在光学传感、单分子检测以及增强光学非线性效应、表面光学光谱学、光化学、光电发射、光伏等领域具有广阔的应用前景。 在这里，我们展示了在由两个金属纳米棒精心设计的二聚体间隙天线中，键合偶极子的纵向等离子体天线模式（AM）可以与横向等离子体腔模式（CMs）竞争，根据CMs的对称性特征（例如径向阶数n和方位量子数m），产生显著增强或抑制的散射效率。 更具体地说，证明了适当加载的间隙层能够激发大量的环状矩，并与其AM偶极矩发生强相互作用，从而在散射光谱中产生类似Fano或电磁诱导透明（EIT）的轮廓。 然而，对于方位数不为零的CMs，光谱特征是各自AM和CM共振的累积表现。 我们提供了这些现象的详细近场和远场分析，表明不同阶数的基本矩之间的模态重叠和相位关系起着关键作用。 提出了一种经典的耦合振子模型，该模型清晰地再现了散射增强和抑制共存的现象。 最后，我们展示了通过调整几何参数和负载的介电常数，可以调节AM和CM的共振带。 我们的结果可能在等离子体隐身、自旋极化定向光发射、超灵敏光学传感和等离子体介导的光致发光等方面有所帮助。 显示英文摘要

摘要： Plasmonic nanoantenna is of promising applications in optical sensing, single-molecular detection, and enhancement of optical nonlinear effect, surface optical spectroscopy, photochemistry, photoemission, photovoltaics, etc. Here we show that in a carefully-designed dimer gap-antenna made by two metallic nanorods, the longitudinal plasmon antenna mode (AM) of bonding dipoles can compete with the transverse plasmonic cavity modes (CMs), yielding dramatically enhanced or suppressed scattering efficiency, depending on the CMs symmetry characteristics (e.g., the radial order n and the azimuthal quantum number m ). More specifically, it is demonstrated that an appropriately loaded gap layer enables substantial excitation of toroidal moment and its strong interaction with the AM dipole moment, resulting in Fano- or electromagnetically induced transparency (EIT)-like profile in the scattering spectrum. However, for CMs with nonzero azimuthal number, the spectrum features a cumulative signature of the respective AM and CM resonances. We supply both detailed near-field and far-field analysis for these phenomena, showing that the modal overlap and phase relationship between the fundamental moments of different order play a crucial role. A classical coupled oscillator model is proposed which clearly reproduces the coexistence of scattering enhancement and suppression. Finally, we show that the resonance bands of the AM and CMs can be tuned by adjusting the geometry parameters and the permittivity of the load. Our results may be useful in plasmonic cloaking, spin-polarized directional light emission, ultra-sensitive optical sensing, and plasmon-mediated photoluminescence.