The investigation of ultrafast nanoscale dynamics requires experimental imaging methodologies with a nanometer spatial and femtosecond temporal resolution.

In our group, we develop and apply ultrafast transmission electron microscopy (UTEM) for time-resolved imaging. In UTEM, a laser-pump/electron probe scheme is employed, utilizing femtosecond electron pulse illumination in a transmission electron microscope [1]. The Oldenburg UTEM is currently being implemented and is based on a laser-driven nanoscale electron sources [1,2]. Applications include the mapping of structural [3,4] and magnetic spatio-temporal dynamics [5,6], as well as the optical coherent control of free-electron pulses [7-9].

[1] A. Feist, N. Bach, N. Rubiano da Silva, Th. Danz, M. Möller, K. E. Priebe, T. Domröse, J. G. Gatzmann, S. Rost, J. Schauss, S. Strauch, R. Bormann, M. Sivis, S. Schäfer, C. Ropers, Ultrafast transmission electron microscopy using a laser-driven field emitter: femtosecond resolution with a high coherence electron beam, Ultramicroscopy 176, 63-73 (2017).
[2] N. Bach, T. Domröse, A. Feist, Th. Rittmann, S. Strauch, C. Ropers, S. Schäfer, Coulomb interactions in high-coherence femtosecond electron pulses from tip emitters, Structural Dynamics 6, 014301 (2019).
[3] A. Feist, N. Rubiano da Silva, W. Liang, C. Ropers, S. Schäfer, Nanoscale diffractive probing of strain dynamics in ultrafast transmission electron microscopy, Structural Dynamics 5, 014302 (2018).
[4] A. Feist, G. Storeck, S. Schäfer, C. Ropers, Structural dynamics probed by high-coherence electron pulses, MRS Bulletin 43, 505 (2018).
[5] T. Eggebrecht, M. Möller, J. G. Gatzmann, N. Rubiano da Silva, A. Feist, U. Martens, H. Ulrichs, M. Münzenberg, C. Ropers, S. Schäfer, A light induced metastable magnetic texture uncovered by in-situ Lorentz microscopy, Phys. Rev. Lett. 118, 097203 (2017).
[6] N. Rubiano da Silva, M. Möller, A. Feist, H. Ulrichs, C. Ropers, S. Schäfer, Nanoscale mapping of ultrafast magnetization dynamics with femtosecond Lorentz microscopy, Phys. Rev. X 8, 031052 (2018).
[7] A. Feist, K.E. Echternkamp, J. Schauss, S.V. Yalunin, S. Schäfer, C. Ropers, Quantum coherent optical phase modulation in an ultrafast transmission electron microscope, Nature 521, 200-203 (2015).
[8] K. E. Echternkamp, A. Feist, S. Schäfer, C. Ropers, Ramsey-type phase control of free electron beams, Nature Phys. 12, 1000-1004 (2016).
[9] K. E. Priebe, C. Rathje, S. V. Yalunin, Th. Hohage, A. Feist, S. Schäfer, C. Ropers, Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy, Nature Photonics 11, 793 (2017).