IFW Dresden, Helmholtzstr. 20, 01069, Dresden, Germany.
EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium.
Nat Commun. 2018 Oct 11;9(1):4207. doi: 10.1038/s41467-018-06572-9.
Plasmonic nanostructures and -devices are rapidly transforming light manipulation technology by allowing to modify and enhance optical fields on sub-wavelength scales. Advances in this field rely heavily on the development of new characterization methods for the fundamental nanoscale interactions. However, the direct and quantitative mapping of transient electric and magnetic fields characterizing the plasmonic coupling has been proven elusive to date. Here we demonstrate how to directly measure the inelastic momentum transfer of surface plasmon modes via the energy-loss filtered deflection of a focused electron beam in a transmission electron microscope. By scanning the beam over the sample we obtain a spatially and spectrally resolved deflection map and we further show how this deflection is related quantitatively to the spectral component of the induced electric and magnetic fields pertaining to the mode. In some regards this technique is an extension to the established differential phase contrast into the dynamic regime.
等离子体纳米结构和器件通过允许在亚波长尺度上修改和增强光场，正在快速改变光操控技术。该领域的进展在很大程度上依赖于新的用于基本纳米级相互作用的表征方法的开发。然而，迄今为止，对表征等离子体耦合的瞬态电场和磁场的直接和定量映射一直难以实现。在这里，我们展示了如何通过在透射电子显微镜中聚焦电子束的能量损失过滤来直接测量表面等离子体模式的非弹性动量转移。通过在样品上扫描光束，我们获得了空间和光谱分辨的偏转图，并且进一步展示了这种偏转如何与模式相关的感应电场和磁场的光谱分量定量相关。在某些方面，该技术是将已建立的微分相位对比技术扩展到动态范围。
