Near Field of Strongly Coupled Plasmons: Uncovering Dark Modes
Near Field of Strongly Coupled Plasmons: Uncovering Dark Modes
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DOI：
10.1021/nl204277y
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发表时间：
2012-04-01
期刊：
影响因子：
10.8
通讯作者：
Schoenhense, Gerd
中科院分区：
文献类型：
--
作者：
Schertz, Florian;Schmelzeisen, Marcus;Schoenhense, Gerd
强耦合等离子体激元在一个系统中的单个金纳米粒子放置在亚纳米距离的金膜（纳米粒子平面，NPOP）的研究使用两个互补的单粒子光谱技术。光学散射光谱专门检测通过其偶极矩耦合到远场的等离子体振子模式（亮模式）。通过使用光发射电子显微镜（PEEM），我们检测在相同的NPOP近场模式，不耦合到散射远场（暗模式），其特征在于由一个强烈增强的nonlinearelectron发射过程。据我们所知，这是第一次，远场和近场光谱进行相同的个人纳米结构通过亚纳米间隙相互作用。强共振电子发射发生在激发波长远偏离共振的散射光谱。
Strongly coupled plasmons in a system of individual gold nanoparticles placed at subnanometer distance to a gold film (nanoparticle-on-plane, NPOP) are investigated using two complementary single particle spectroscopy techniques. Optical scattering spectroscopy exclusively detects plasmon modes that couple to the far field via their dipole moment (bright modes). By using photoemission electron microscopy (PEEM), we detect in the identical NPOPs near-field modes that do not couple to the scattered far field (dark modes) and are characterized by a strongly enhanced nonlinearelectron emission process. To our knowledge, this is the first time that both far- and near-field spectroscopy are carried out for identical individual nanostructures interacting via a subnanometer gap. Strongly resonant electron emission occurs at excitation wavelengths far off-resonant in the scattering spectra.