1] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [3].
1] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [3].
Nat Commun. 2014 Jun 18;5:4125. doi: 10.1038/ncomms5125.
High-spatial and energy resolution electron energy-loss spectroscopy (EELS) can be used for detailed characterization of localized and propagating surface-plasmon excitations in metal nanostructures, giving insight into fundamental physical phenomena and various plasmonic effects. Here, applying EELS to ultra-sharp convex grooves in gold, we directly probe extremely confined gap surface-plasmon (GSP) modes excited by swift electrons in nanometre-wide gaps. We reveal the resonance behaviour associated with the excitation of the antisymmetric GSP mode for extremely small gap widths, down to ~5 nm. We argue that excitation of this mode, featuring very strong absorption, has a crucial role in experimental realizations of non-resonant light absorption by ultra-sharp convex grooves with fabrication-induced asymmetry. The occurrence of the antisymmetric GSP mode along with the fundamental GSP mode exploited in plasmonic waveguides with extreme light confinement is a very important factor that should be taken into account in the design of nanoplasmonic circuits and devices.
高空间和能量分辨率电子能量损失谱（EELS）可用于详细表征金属纳米结构中局域和传播的表面等离激元激发，深入了解基本物理现象和各种等离子体效应。在这里，我们将 EELS 应用于金制的超锐凸槽，直接探测由纳米级宽间隙中的快速电子激发的极其受限的间隙表面等离激元（GSP）模式。我们揭示了与非常小的间隙宽度（低至~5nm）下激发的非对称 GSP 模式相关的共振行为。我们认为，这种模式的激发具有很强的吸收能力，在具有制造诱导不对称性的超锐凸槽的非共振光吸收的实验实现中起着至关重要的作用。非对称 GSP 模式与在具有极端光限制的等离子体波导中利用的基本 GSP 模式的同时出现，是在设计纳米等离子体电路和器件时应考虑的一个非常重要的因素。
