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.
|Status||Udgivet - 23. mar. 2022|
Bibliografisk noteFunding Information:
S.R. is a Sapere Aude Research Leader supported by Independent Research Fund Denmark (Grant 7026-00117B). N.A.M. is a VILLUM Investigator supported by VILLUM FONDEN (Grant 16498). C.W. acknowledges funding from a MULTIPLY fellowship under the Marie Skłodowska-Curie COFUND Action (Grant Agreement 713694). P.E.S. is the recipient of the Zonta Denmark’s Scholarship for female Ph.D. students in Science and Technology 2021.
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