WUHAN, China (November 13, 2015) - Wuhan Optoelectronics Forum No. 106 was successfully held in Auditorium A101 at Wuhan National Laboratory for Optoelectronics (WNLO) in the morning of November 13.
Ultrafast transmission electron microscopy (UTEM) is a promising technique for the investigation of ultrafast dynamics with nanoscale spatial resolution. Based on the recent progress in the construction of coherent pulsed electron sources, we present the first implementation of a 3rd-generation UTEM instrument. Utilizing localized photoemission from a nanoscale needle photocathode, we obtain highly coherent electron pulses with electron focal spot sizes on the sample of a few nanometers and electron pulse durations of about 300 fs. In this colloquium, we will present several applications enabled by the advantageous beam properties in the Göttingen UTEM instrument: (1) we demonstrate real-space Lorentz imaging of magnetic vortex structures in a nanopatterned permalloy film, opening up the investigation of ultrafast magnetism in UTEM. (2) we locally probe laser-induced acoustic phonons, originating from the edge of a single-crystalline graphite flake. (3) we demonstrate optical phase modulation of free electron beams in laser-driven near-fields, yielding coherent superpositions of electron momentum states. Finally, I will discuss future research directions of 3rd-generation UTEM instruments, using their broad capabilities for time-resolved electron imaging, diffraction and spectroscopy.
Dr. Schäfer graduated at the Technical University Darmstadt (TUD) with honors in 2004; he received his Ph. D. diploma with honors at TUD in 2008. In 2009-2012 he worked as a post doctoral scholar in A. H. Zewail’s group at Caltech. Since 2012 he has been working for Habilitand at Georg-August-Universität Göttingen. Dr. Schäfer’s research interests include ultrafast electronic, magnetic and structural dynamics in inhomogeneous systems, methodical development of time-resolved electron microscopy and diffraction, and light-matter interaction at the nanoscale. He built the state-of-art ultrafast transmission electron microscopy and ultrafast low energy electron diffraction in Georg-August-Universität Göttingen. His work were published in high profile journals including Science and Nature. As a young scholar, Dr. Schäfer received many honors, such as the Feodor-Lynen-Fellow of the Alexander von Humboldt-Gesellschaft.
