Ultrafast Transmission Electron Microscopy (UTEM)
The direct imaging of microscopic structural changes on ultrafast timescales is a particular challenge in the natural sciences. Alongside ultrafast X-ray techniques, time-resolved electron microscopy, diffraction and spectroscopy will yield unprecedented insights into rapid physical, chemical and biological processes. We follow a variety of imaging approaches with ultrashort, highly coherent electron pulses to investigate the dynamics of ultrafast electronic and structural phenomena.
Over the past few years, our research group has developed a novel implementation of Ultrafast Transmission Electron Microscopy ("UTEM"). The instrument employs a "pump-probe" scheme, in which two laser pulses are coupled into the column of a transmission electron microscope (TEM) (see image on the right): A first laser pulse excites an electronic or structural change in the investigated sample (red beam). In a special photocathode, a second, delayed laser pulse (blue beam) generates an ultrafast electron pulse (green), which then probes the induced sample change in microscopy, diffraction or spectroscopy. By varying the relative pulse delay, the dynamics can be followed in time.
Our ultrafast TEM is the first in Germany, and it is the first time-resolved TEM worldwide that uses the localized photoemission from a field-emission tip to create an extremely high laser-triggered electron beam quality (see image below).
Background on the development of ultrafast electron microscopy in Göttingen
Time-resolved electron microscopy with laser excitation was initially pursued by Prof. O. Bostanjoglo (TU Berlin) in the 1980s. By overcoming experimental difficulties and using advancements in laser technology, the group of nobel laureate A. H. Zewail (Caltech) has made significant progress in the technique since about 2005. In parallel, researchers at Lawrence Livermore National Laboratory (LLNL) carried out developments of a single-shot TEM. Presently, a variety of projects in Europe and around the world are focusing on the implementation and application of ultrafast transmission electron microscopy.
In Göttingen, we initiated work towards ultrafast TEM in 2009, motivated by our research on ultrafast photoemission from field emitter tips. We are convinced that the power and analytical capability of the technique will drastically grow by using nanoscale electron sources. Based on this concept, in 2011, we received funding from the Deutsche Forschungsgemeinschaft (DFG) and the "Niedersächsisches Vorab" (VolkswagenFoundation) for a transmission electron microscope and a femtosecond laser system (Principal Investigator: C. Ropers. Co-P.I.s: C. Jooß, M. Münzenberg, K. Samwer, M. Seibt, C. Volkert). After the preparation of suitable laboratory space in the Physics Faculty, the instruments were installed in 2012 and 2013 (TEM: JEOL-2100F; Laser: Coherent-RegA), and we began with the necessary modifications of the TEM.
Since 2013, the development of our UTEM is funded by the DFG within Collaborative Research Center 1073 "Atomic Scale Control of Energy Conversion" (in particular UTEM-project A05; PIs: C. Ropers, S. Schäfer). In 2014, we realized successful pulsed operation of the TEM and initiated time-resolved studies on a variety of systems and in different configurations. Presently, we are investigating quantum coherent interactions of free electrons with optical near-fields, optically induced magnetization dynamics and the dynamics of structural and electronic phase transitions.
"Pinning and gyration dynamics of magnetic vortices revealed by correlative Lorentz and bright-field imaging"
M. Möller, J. H. Gaida and C. Ropers
arXiv:2107.10208 , (2021) [arXiv]
"Integrated photonics enables continuous-beam electron phase modulation"
J.-W. Henke, A. S. Raja, A. Feist, G. Huang, G. Arend, Y. Yang, J. Kappert, R. N. Wang, M. Möller, J. Pan, J. Liu, O. Kfir, C. Ropers and T. J. Kippenberg
arXiv:2105.03729 , (2021) [arXiv]
"Modulation of Cathodoluminescence Emission by Interference with External Light"
V. Di Giulio, O. Kfir, C. Ropers, F.J. García de Abajo
ACS Nano 15(4), 7290-7304 (2021) [arXiv]
"Tailored high-contrast attosecond electron pulses for coherent excitation and scattering" openaccess
S. V. Yalunin, A. Feist, C. Ropers
Phys. Rev. Research 3, L032036 (2021) [arXiv]
"Optical coherence transfer mediated by free electrons" openaccess
O. Kfir, V. Di Giulio, F. J. García de Abajo, C. Ropers
Sci. Adv. 7 (18), eabf6380 (2021) [arXiv]
"Observation of fluctuation-mediated picosecond nucleation of a topological phase"
F. Büttner,, B. Pfau, M. Böttcher, M. Schneider, G. Mercurio, C. M. Günther, P. Hessing, C. Klose, A. Wittmann, K. Gerlinger, L.-M. Kern, C. Strüber, C. von Korff Schmising, J. Fuchs, D. Engel, A. Churikova, S. Hu
Nat. Mater. 20, 30-37 (2021)
"Spontaneous and Stimulated Electron-Photon Interactions in Nanoscale Plasmonic Near Fields" openaccess
M. Liebtrau, M. Sivis, A. Feist, H. Lourenço-Martins, N. Pazos-Pérez, R. A. Alvarez-Puebla, F. J. García de Abajo, A. Polman and C. Ropers
Light Sci. Appl. 10(82), (2021) [arXiv]
"Ultrafast nanoimaging of the order parameter in a structural phase transition"
Th. Danz, T. Domröse, C. Ropers
Science 371, 371-374 (2021) [arXiv]
"Toward Quantum Optics with Free Electrons"
K. Wang, R. Dahan, S. Nehemia, O. Reinhardt, S. Tsesses, I. Kaminer, O. Kfir, H. Lourenço-Martins, A. Feist, C. Ropers, T.J. Kippenberg
Opt Photonics News 31 (12), 35 (2020)
P. Dombi, Z. Pápa, J. Vogelsang, S. V. Yalunin, M. Sivis, G. Herink, S. Schäfer, P. Groß, C. Ropers, and C. Lienau
Rev. Mod. Phys. 92, 025003-1 (2020)
"Nanoscale Nonlinear Spectroscopy with Electron Beams"
A. Konecná, V. Di Giulio, V. Mkhitaryan, C. Ropers, F. J. García de Abajo
ACS Photonics 7, 1290-1296 (2020) [arXiv]
"Few-nm tracking of current-driven magnetic vortex orbits using ultrafast Lorentz microscopy" openaccess
M. Möller, J. H. Gaida, S. Schäfer and C. Ropers
Commun. Phys. 3, 36 (2020) [arXiv]
"Density matrix reconstructions in ultrafast transmission electron microscopy: uniqueness, stability, and convergence rates"
C. Shi, C. Ropers, T. Hohage
Inverse Problems 36, 025005 (2020)
"Controlling free electrons with optical whispering-gallery modes"
O. Kfir, H. Lourenço-Martins, G. Storeck, M. Sivis, T. R. Harvey, T. J. Kippenberg, A. Feist, C. Ropers
Nature 582, 46-49 (2020) [arXiv]
"Probing chirality with inelastic electron-light scattering"
T. R. Harvey, J.-W. Henke, O. Kfir, H. Lourenço-Martins, A. Feist, F. J. García de Abajo, C. Ropers
Nano Lett. 20, 4377-4383 (2020) [arXiv]
"High-purity free-electron momentum states prepared by three-dimensional optical phase modulation"
A. Feist, S. V. Yalunin, S. Schäfer, C. Ropers
Phys. Rev. Research 2, 043227 (2020) [arXiv]
"Coulomb interactions in high-coherence femtosecond electron pulses from tip emitters" openaccess
N. Bach, T. Domröse, A. Feist, T. Rittmann, S. Strauch, C. Ropers and S. Schäfer
Struct. Dyn. 6, 014301 (2019)
"Structural dynamics probed by high-coherence electron pulses"
A. Feist, G. Storeck, S. Schaefer, and C. Ropers
MRS Bull. 43, 504-511 (2018)
"Nanoscale mapping of ultrafast magnetization dynamics with femtosecond Lorentz microscopy" openaccess
N. Rubiano da Silva, M. Moeller, A. Feist, H. Ulrichs, C. Ropers, and S. Schaefer
Phys. Rev. X 8, 031052 (2018) [arXiv]
"Nanoscale diffractive probing of strain dynamics in ultrafast transmission electron microscopy" openaccess
A. Feist, N. Rubiano da Silva, W. Liang, C. Ropers, S. Schaefer
Struct. Dyn. 5, 014302 (2018) [arXiv]
"Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam" openaccess
A. Feist, N. Bach, N. R. da Silva, Th. Danz, M. Moeller, K. E. Priebe, T. Domroese, J. G. Gatzmann, S. Rost, J. Schauss, S. Strauch, R. Bormann, M. Sivis, S. Schaefer, C. Ropers
Ultramicroscopy 176, 63-73 (2017) [arXiv]
"Light-Induced Metastable Magnetic Texture Uncovered by in situ Lorentz Microscopy"
T. Eggebrecht, M. Moeller, J. G. Gatzmann, N. Rubiano da Silva, A. Feist, U. Martens, H. Ulrichs, M. Muenzenberg, C. Ropers, S. Schaefer
Phys. Rev. Lett. 118, 097203 (2017)
"Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy"
K. E. Priebe, C. Rathje, S. V. Yalunin, T. Hohage, A. Feist, S. Schaefer, C. Ropers
Nat. Photonics 11, 793-797 (2017) [arXiv]
"Structural and magnetic characterization of large area, free-standing thin films of magnetic ion intercalated dichalcogenides Mn0.25TaS2 and Fe0.25TaS2"
Th. Danz, Q. Liu, X. D. Zhu, L. H. Wang, S. W. Cheong, I. Radu, C. Ropers, R. I. Tobey
J. Phys. Condens. Matter 28, 356002 (2016) [arXiv]
"Ramsey-type phase control of free-electron beams"
K. E. Echternkamp, A. Feist, S. Schaefer, C. Ropers
Nat. Phys. 12, 1000-1004 (2016)
"Quantum coherent optical phase modulation in an ultrafast transmission electron microscope"
A. Feist, K. E. Echternkamp, J. Schauss, S. V. Yalunin, S. Schaefer, C. Ropers
Nature 521, 200-203 (2015)