Low-Energy Electron-Photon Interactions in a Scanning Electron Microscope

The interaction of free-electrons with matter and light is among the most fundamental of processes in nature. From the use of free-electrons for atomic imaging, to their use in the generation of high-intensity, tunable light in synchrotrons, the physics of unconfined electrons has wide application. In recent years, there has been a new focus on the quantum nature of individual electrons in electron microscopes to enable further improvements in these technologies. This work takes advantage of developments in ultrafast optics, electron spectroscopy, quantum optics, and nanofabrication to explore various electron-electron, electron-photon, and electron-material interactions. In this thesis, we construct a low-energy, ultrafast scanning electron microscope, using it to explore quantum coherent interactions between electrons, light, and matter. In Chapter 1, we review the history of free electron experiments and how advances in nanofabrication, low-dimensional materials, and ultrafast optics have opened new opportunities for electron-light interactions to a degree not previously possible. In Chapter 2 we discuss experimental forms of quantum electron microscopy known as interaction-free measurement and electron multi-passing. Chapter 3 details a general theory of electron-photon interactions, including simulations with quantum two-level systems and extended optical nanostructures. In Chapter 4, we design and construct a second microscope with ultrafast triggering, an electron spectrometer with sub-eV resolution, nanostructured interaction regions, and active beam alignment. Chapter 5 explores various experimental results, demonstrating enhanced loss spectroscopy of 2D materials, energy resolution of gold nanoparticle plasmons, as well as spectroscopy of time-tagged cathodoluminescence from optical fibers. Finally, in chapter 6 we discuss future perspectives of this approach, analyzing the impact a heralded electron source would have on electron microscopy and lithography.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2025

Author dc:creator

• Simonaitis, John

Advisors dc:contributor.advisor

• Keathley, Phillip D.
• Berggren, Karl K.

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright retained by author(s)

Licence dc:rights.uri

• https://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/164160

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/164160