Combintion of Scanning Electron- and Darkfield-Microsocopes to study electron-light interactions

• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447330010

Our group is interested in characterizing nanoptical systems as well as free-electron-light interactions at the extreme levels. We ask ourselves, what kind of nanosystems can be realized, in order to foster enhanced electron-light interactions, leading to (i) the generation of coherent light in interaction with electron beams, (ii) nearly deterministic single-photon generation, and (iii) dynamical electron optics. We are interested in designing systems that in combination with laser excitations, lead to quantum-coherent elastic and inelastic transitions in free-electron wavepackets. Within this concept, we are interested in particular, in exploring the domain of parameters involved (like laser intensity, polarization, and incidence angle, electron velocity), to seek for regions where the interactions cannot be described adiabatically; therefore, a whole set of new physical principles emerge. As an example, quantum coherent interferences might occur as a result of temporarily driving the electrons out of equilibrium thanks to two-photon processes − in such a way that momentum-matching criterion can be satisfied for single-photon processes as well, whereas in normal conditions, single-photon interactions are forbidden. Moreover, quantum-coherent paths leading to such interactions may interfere; subsequently, exotic diffraction patterns are observed. In particular, we would like to design nano- and micro-structures that in interaction with electron beams, act as coherent sources of light in electron microscopes. Therefore, incorporation of those systems in electron microscopes can serve for correlative electron-light microscopy and spectroscopy. For this purpose, we intend to used hybrid excitonic/plasmonic systems, which through strong interaction of plasmons and excitons, both coherent polarizations as well as strong electron-induced radiations are achieved. Additionally, our plan is to realize systems for investigating the interactions of slow-electron wavepackets, with kinetic energies ranging from 200 eV to sub-10 keV, with light and nanostructures. Slow electrons are more sensitive to the electromagnetic interactions in comparison with their relativistic counterparts; as a result, nonadiabatic interactions are also more easily triggered. Within this project, laser pulses will be used to excite a field-emission electron source and to generate single-electron wavepackets as well. Interaction of photoemission electron wavepackets with light in the microscopy chamber will be investigated by means of commercial and house-build transmission electron detectors.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Kombination aus Rasterelektronen- und Dunkelfeldmikroskop zur Untersuchung von Elektronen-Licht-Wechselwirkungen
• Instrumentation Group: 5120 Rasterelektronenmikroskope (REM)
• Applicant Institution: Christian-Albrechts-Universität zu Kiel
• Leader: Professorin Nahid Talebi, Ph.D.