Visualizing Electric and Magnetic Field Coupling in Au-Nanorod Trimer Structures via Stimulated Electron Energy Gain and Cathodoluminescence Spectroscopy: Implications for Meta-Atom Imaging
Visualizing Electric and Magnetic Field Coupling in Au-Nanorod Trimer Structures via Stimulated Electron Energy Gain and Cathodoluminescence Spectroscopy: Implications for Meta-Atom Imaging
复制标题
DOI：
10.1021/acsanm.1c03171
复制
发表时间：
2022-02
影响因子：
5.9
通讯作者：
David A. Garfinkel;V. Iyer;Robyn Seils;Grace Pakeltis;Marc R. Bourgeois;A. Rossi;Clay Klein;B. Lawrie;D. Masiello;P. Rack
中科院分区：
文献类型：
--
作者：
David A. Garfinkel;V. Iyer;Robyn Seils;Grace Pakeltis;Marc R. Bourgeois;A. Rossi;Clay Klein;B. Lawrie;D. Masiello;P. Rack
利用电子能量损失（EEL）、阴极发光（CL）和受激电子能量损失/增益（sEEL/sEEG）光谱对三聚体元原子的近场等离子体响应进行了表征。三聚体结构杂化成低能量模式，所有三个棒同步耦合，产生循环电流，从而产生磁场。下一个最高能量模式由两个非相耦合的棒组成，并产生净电偶极子。我们通过EEL和CL研究了磁电混合模式的近场，并关联了它们的光谱特征和强度图。然后，通过改变三聚体棒的长度，我们将磁模式和电模式调整为我们的激光能量，并通过sEEL/sEEG光谱表征激发态。对两种模式相对于光源的倾斜依赖性的探索表明，电模式sEEG强度的增加大于预期的光电场耦合的sin2（θ）依赖性（详细说明请参见支持信息）。在修正了近距离电模式的尾部后，我们通过光场的磁性分量与磁性元原子的耦合来证明sEEG，该耦合具有预期的cos2（θ）倾斜依赖性。这一发现为探索其他磁性元原子结构的纳米级激发态近场成像提供了可能。
Trimer meta-atoms composed of three gold rods in an equilateral triangular geometry were fabricated, and their near-field plasmonic responses were characterized via electron energy loss (EEL), cathodoluminescence (CL), and stimulated electron energy loss/gain (sEEL/sEEG) spectroscopy. The trimer structure hybridizes into a low-energy mode with all three rods coupling in-phase, which produces a circulating current and thus a magnetic field. The next highest-energy mode consists of two rods coupling out-of-phase and produces a net electric dipole. We investigate the near fields of hybridized magnetic and electric modes via EEL and CL and correlate their spectral characteristics and intensity maps. Then, by changing the length of the trimer rods, we tune the magnetic and electric modes to our laser energy and characterize the excited state via sEEL/sEEG spectroscopy. Exploration of the tilt dependence, relative to the optical source, of the two modes reveals that the electric mode sEEG intensity increases more than the expected sin2(θ) dependence of the optical electric field coupling (see the Supporting Information for a detailed description). After correcting for the tail of the close-proximity electric mode, we demonstrate sEEG via coupling of the magnetic component of the optical field to the magnetic meta-atoms, which has the expected cos2(θ) tilt dependence. This realization opens the possibility to explore the nanoscale excited-state near-field imaging of other magnetic meta-atom structures.