Claus Ropers1

1, University of Göttingen, Göttingen, , Germany

Novel methods in time-resolved electron microscopy, diffraction and spectroscopy promise unprecedented insight into the dynamics of structural, electronic and magnetic processes on the nanoscale. A key to the realization of such technologies is the generation of high-quality beams of ultrashort electron pulses. This talk will present our recent development of imaging and spectroscopy capabilities using laser-triggered field-emitter sources in electron microscopy [1].
Based on custom modifications of Schottky-field-emission transmission electron microscope, an ultrafast electron probe beam with temporal resolution down to 200 fs, a spectral width of 0.6 eV and sub-nanometer beam focusability is demonstrated.
First applications of this instrument will be discussed, which include studies of compressive and shear strain wave dynamics in thin films probed by ultrafast convergent beam electron diffraction [2], magnetization dynamics in nanostructures observed by ultrafast Lorentz microscopy[3], and imaging of optical near-fields using inelastic electron-light scattering. Moreover, new approaches to free-electron quantum optics [4,5] and the generation of attosecond pulse trains [6] will be introduced.

[1] A. Feist et al., “Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high-coherence electron beam”, Ultramicroscopy 176, 63 (2017).
[2] A. Feist et al., “Nanoscale diffractive probing of strain dynamics in ultrafast transmission electron microscopy”, arXiv:1709.02805 (2017).
[3] N. Rubiano da Silva et al., “Nanoscale mapping of ultrafast magnetization dynamics with femtosecond Lorentz Microscopy”, arXiv:1710.03307 (2017).
[4] A. Feist et al., “Quantum coherent optical phase modulation in an ultrafast transmission electron microscope”, Nature
521, 200 (2015).
[5] K. E. Echternkamp et al., “Ramsey-type phase control of free electron beams”, Nature Phys. 12, 1000 (2016).
[6] K. E. Priebe et al., “Attosecond Electron Pulse Trains and Quantum State Reconstruction in Ultrafast Transmission Electron Microscopy”, arXiv:1706.03680 (2017).