Electron Beam Spectroscopy for Nanophotonics

TL;DR

Recent advances in electron-beam spectroscopy enable detailed, high-resolution studies of nanophotonic structures by analyzing electron energy losses and light emission, offering new insights into optical responses at the nanoscale.

Contribution

This review highlights recent progress in electron-beam spectroscopies, focusing on control over electron wave functions and applications in nanophotonics and optically resonant modes.

Findings

Enhanced spatial, energy, and time resolution in nanophotonics studies

Improved control over electron wave functions for targeted excitations

Applications in studying and utilizing nanostructure resonances

Abstract

Progress in electron-beam spectroscopies has recently enabled the study of optical excitations with combined space, energy and time resolution in the nanometer, millielectronvolt and femtosecond domain, thus providing unique access into nanophotonic structures and their detailed optical responses. These techniques rely on $\approx$ 1-300 keV electron beams focused at the sample down to sub-nanometer spots, temporally compressed in wavepackets a few femtoseconds long, and in some cases controlled by ultrafast light pulses. The electrons undergo energy losses and gains, also giving rise to cathodoluminescence light emission, which are recorded to reveal the optical landscape along the beam path. This review portraits these advances, with a focus on coherent excitations, emphasizing the increasing level of control over the electron wave functions and ensuing applications in the study and technological use of optically resonant modes and polaritons in nanoparticles, 2D materials and engineered nanostructures.