Spatio-temporal shaping of electron wavepackets for time-domain electron holography

Advanced techniques of electron microscopy and spectroscopy require tools, which enable to control various degrees of freedom of electron beams (phase profile, temporal structure, orbital angular momentum, etc.). The inelastic quantum coherent interaction between light waves and electron wavepackets allows to structure the temporal probability distribution of electrons with attosecond precision, which may enable probing the coherent dynamics of optical excitations or plasmonic near-fields of nanostructures and metamaterials. Up to now, only electron-photon interactions mediated by solid-state structures have been considered, which have severe limitations. In this project I will develop a versatile tool for quantum coherent shaping and full characterisation of the phase profile and amplitude of the electron wave function in electron microscopes. The interaction will be mediated by the ponderomotive potential of spatio-temporally shaped light fields in vacuum. The electron wavepackets will be controlled on nanometer spatial and sub-femtosecond time scales that are natural for light waves. The optical coherence imprinted to the electron wavepackets will be exploited in two ways: i) I will explore the possibility to transfer the temporal coherence from density-modulated electron wavepackets to radiation and bound electron excitations in two-level quantum systems by detecting phase-resolved cathodoluminescence and coherent Smith-Purcell radiation driven by swift electrons. ii) I will introduce time-domain electron holography, which will exploit the temporal coherence of shaped electron wavepackets for phase-resolved imaging of optical excitations in nanostructures. The approaches proposed in this project open new pathways for electron-mediated optical quantum-coherent control and spectroscopy with atomic spatial resolution.