Modulation of Cathodoluminescence Emission by Interference with External Light

TL;DR

This paper demonstrates that free-electron pulses can interfere with external light in nanostructures, enabling modulation of cathodoluminescence spectra and opening new avenues for ultrafast material manipulation.

Contribution

It introduces a first-principles theory showing electron-light interference in cathodoluminescence, challenging the notion of incoherent spontaneous processes.

Findings

Electron-light interference modulates cathodoluminescence spectra.

Phase-locked laser can cancel cathodoluminescence.

Simulations show feasibility in ultrafast electron microscopes.

Abstract

Spontaneous processes triggered in a sample by free electrons are commonly regarded as incoherent, and therefore unable to interfere with external light sources. Here, we challenge this concept by showing through first-principles theory that light and free-electron pulses can interfere when interacting with a nanostructure, giving rise to a modulation in the spectral distribution of the cathodoluminescence light emission that is strongly dependent on the electron wave function. Specifically, for a temporally focused electron, cathodoluminescence can be cancelled upon illumination with a spectrally modulated dimmed laser that is phase-locked relative to the electron density profile. We illustrate this idea with realistic simulations under attainable conditions in currently available ultrafast electron microscopes. We further argue that the interference between excitations produced by light and free electrons opens a new window to manipulate the ultrafast materials response by combining the spectral and temporal selectivity of the light with the atomic resolution of electron beams.