Broadband coupling of fast electrons to high-Q whispering-gallery mode resonators

TL;DR

This paper demonstrates broadband excitation of whispering-gallery modes in silica microresonators by fast electrons, enabling quantum optical studies in electron microscopy with high-Q resonators and potential quantum metrology applications.

Contribution

It introduces a novel method for coupling fast electrons to high-Q optical resonators, expanding the capabilities of electron microscopy for quantum optics research.

Findings

Observation of a comb of equidistant peaks in cathodoluminescence spectrum

Cavity quality factors exceeding 700 achieved

First demonstration of broadband electron excitation of whispering-gallery modes

Abstract

Transmission electron microscopy is an excellent experimental tool to study the interaction of free electrons with nanoscale light fields. However, up to now, applying electron microscopy to quantum optical investigations was hampered by the lack of experimental platforms which allow a strong coupling between fast electrons and high-quality resonators. Here, as a first step, we demonstrate the broad-band excitation of optical whispering-gallery modes in silica microresonators by fast electrons. In the emitted coherent cathodoluminescence spectrum, a comb of equidistant peaks is observed, resulting in cavity quality factors larger than 700. These results enable the study of quantum optical phenomena in electron microscopy with potential applications in quantum electron-light metrology.