Spectrally resolved free electron-light coupling strength in a transition metal dichalcogenide

TL;DR

This paper investigates the spectral and spatial dependence of free electron-light coupling in a MoS2 thin film using broadband light pulses, revealing interference effects and mode-guided phenomena with high resolution.

Contribution

It introduces a spectrally resolved approach to study electron-light interactions in transition metal dichalcogenides, combining experimental and numerical methods.

Findings

Coupling strength depends on position and photon energy.

Interference effects influence electron-light interactions.

Optical modes within the TMD film affect coupling behavior.

Abstract

Recent advancements in electron microscopy have introduced innovative techniques enabling the inelastic interaction of fast electrons with tightly confined and intense light fields. These techniques, commonly summarized under the term photon-induced nearfield electron microscopy now offer unprecedented capabilities for a precise mapping of the characteristics of optical near-fields with remarkable spatial resolution but their spectral resolution were only scarcely investigated. In this study, we employ a strongly chirped and temporally broadband light pulse to investigate the interaction between free electrons and light at the edge of a MoS2 thin film. Our approach unveils the details of electron-light coupling, revealing a pronounced dependence of the coupling strength on both the position and photon energy. Employing numerical simulations of a simplified model system we identify these modulations to be caused by optical interferences between the incident and reflected field as well as an optical mode guided within the transition metal dichalcogenide film.