Speaker
Description
How can we see nanoscale light–matter interactions and fast dynamics at interfaces without damaging fragile samples? In this colloquium, I will introduce Optical Near-field Electron Microscopy (ONEM), a new imaging approach that combines the non-invasiveness of light optics with high spatial resolution enabled by electron optics. The core idea is simple [1]: a specimen is illuminated with light, and the resulting near-field intensity patterns are converted into photoelectrons using a thin photocathode. Those photoelectrons are then imaged with a low-energy electron microscope, providing access to sub-diffraction near-field contrast with minimal invasiveness.
I will explain the underlying theory [1,2] and demonstrate that our prototype achieves a spatial resolution of ~ 30 nm at Hz frame rates [3]. I will then present three illustrative applications: mapping polarization-dependent plasmon modes in nanostructures, live imaging of E. coli in a liquid cell, and real-time visualization of copper electrodeposition. These examples demonstrate ONEM’s unique combination of high spatial resolution, fast temporal response, and compatibility with liquid and electrochemical environments. I will finish by discussing technical challenges, expected improvements, and potential future directions in biology, electrochemistry, and nanophotonics.
References:
[1] R. Marchand et al., Physical Review Applied 16 (1), 014008 (2021)
[2] L. Kienesberger et al., Physical Review Research 6 (2), 23204–23204 (2024)
[3] I. Zykov et al., arxiv (2025)