Fiedler Saskia, Stamatopoulou P Elli, Assadillayev Artyom, Wolff Christian, Sugimoto Hiroshi, Fujii Minoru, Mortensen N Asger, Raza Søren, Tserkezis Christos
Center for Nano Optics, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Department of Physics, Technical University of Denmark, Fysikvej, DK-2800 Kongens Lyngby, Denmark.
Nano Lett. 2022 Mar 23;22(6):2320-2327. doi: 10.1021/acs.nanolett.1c04754. Epub 2022 Mar 14.
Cathodoluminescence spectroscopy performed in an electron microscope has proven a versatile tool for analyzing the near- and far-field optical response of plasmonic and dielectric nanostructures. Nevertheless, the transition radiation produced by electron impact is often disregarded in the interpretation of the spectra recorded from resonant nanoparticles. Here we show, experimentally and theoretically, that transition radiation can by itself generate distinct resonances that, depending on the time-of-flight of the electron beam inside the particle, can result from constructive or destructive interference in time. Superimposed on the eigenmodes of the investigated structures, these resonances can distort the recorded spectrum and lead to potentially erroneous assignment of modal characters to the spectral features. We develop an intuitive analogy that helps distinguish between the two contributions. As an example, we focus on the case of silicon nanospheres and show that our analysis facilitates the unambiguous interpretation of experimental measurements on Mie-resonant nanoparticles.
在电子显微镜中进行的阴极发光光谱已被证明是分析等离子体和介电纳米结构近场和远场光学响应的通用工具。然而，在解释从共振纳米颗粒记录的光谱时，电子撞击产生的过渡辐射常常被忽视。在这里，我们通过实验和理论表明，过渡辐射本身可以产生不同的共振，这取决于电子束在颗粒内部的飞行时间，可能是由时间上的相长干涉或相消干涉导致的。叠加在所研究结构的本征模上，这些共振会扭曲记录的光谱，并可能导致对光谱特征的模态特征进行错误的归属。我们开发了一个直观的类比来帮助区分这两种贡献。作为一个例子，我们专注于硅纳米球的情况，并表明我们的分析有助于对米氏共振纳米颗粒的实验测量进行明确的解释。
