Visualizing Standing Light Waves in Continuous-Beam Transmission Electron Microscopy

TL;DR

This paper demonstrates a method for visualizing standing light waves in a waveguide using electron microscopy, enabling phase-resolved imaging of optical modes with potential for advanced nano-optics measurements.

Contribution

It introduces a novel approach combining femtosecond light pulses and Lorentz microscopy to map optical modes in electron microscopy, expanding capabilities for phase-resolved light field imaging.

Findings

Successful mapping of optical modes in waveguides

Quantitative description of image contrast linked to light intensity

Robust imaging across various sample geometries

Abstract

The phase-resolved imaging of confined light fields by homodyne detection is a cornerstone of metrology in nano-optics and photonics, but its application in electron microscopy has been limited so far. Here, we report the mapping of optical modes in a waveguide structure by illumination with femtosecond light pulses in a continuous-beam transmission electron microscope. Multi-photon photoemission results in a remanent charging pattern which we image by Lorentz microscopy. The resulting image contrast is linked to the intensity distribution of the standing light wave and quantitatively described within an analytical model. The robustness of the approach is showcased in a wider parameter range and more complex sample geometries including micro- and nanostructures. We discuss further applications of light-interference-based charging for electron microscopy with in-situ optical excitation, laying the foundation for advanced measurement schemes for the phase-resolved imaging of propagating light fields.