Using Cathodoluminescence Spectroscopy for Imaging Optical Modes of a Plasmonic Square Lattice
Paul Bittorf a, Fatemeh Davoodi a, Maximilian Black a, Nahid Talebi a
a Institute for Experimental and Applied Physics, Kiel University, 24118 Kiel, Germany
Proceedings of Electron Beam Spectroscopy for Nanooptics 2021 (EBSN2021)
Online, Spain, 2021 June 14th - 15th
Organizers: Mathieu Kociak and Nahid Talebi
Poster, Paul Bittorf, 042
Publication date: 8th June 2021

Plasmonic gold structures are fascinating for analyzing the effects of strong light-electron interactions. For example, they can be used for waveguides or development of faster optoelectronic devices. Here, we investigate a two-dimensional periodic hole structure with a square lattice (lattice parameter of approx. 1.6 µm) incorporated inside a plasmonic gold layer, which has a thickness of around 50 nm, using cathodoluminescence (CL) spectroscopy in a scanning electron microscope. Due to its high spatial and energy resolution, cathodoluminescence spectroscopy is used for imaging the optical response of the nanostructure in the visible to near infrared spectral range. When an electron beam interacts with metals, it generates light in the form of transition radiation (TR) and also excite propagating surface plasmon polaritons (SPP). These SPP do not radiate without help, but when reaching the edges of the holes, they are scattered and radiate. The interference between the radiation from different holes results in interference fringes in the acquired angle-resolved CL maps, that can be used to investigate the plasmonic modes. With the recorded hyperspectral maps of the gold surface between the holes, we reveal the spatial distribution of optical modes and compare this to our simulations and complementary dark-field microscopy for a better understanding of their radiation properties.

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