Femtosecond streaking of electron diffraction patterns to study structural dynamics in crystalline matter

Abstract

A table-top femtosecond, non-relativistic, electron diffraction setup is combined with a low-jitter, photo-triggered streak camera to follow the optically induced structural dynamics in complex solids. A temporal resolution of 550 fs is experimentally demonstrated, while the route to streaking with sub-250 fs temporal resolution is outlined. The streaking technique allows for parallel capturing of temporal information as opposed to the serial data acquisition in a conventional scanning femtosecond electron diffraction. Moreover, its temporal resolution is not corrupted by increasing the number of electrons per pulse. Thus, compared to the conventional scanning approach, a substantial increase in signal-to-noise ratio (SNR) can be achieved. These benefits are demonstrated by studying a photo-induced charge density wave phase transition in 4H_b-TaSe₂ using both methods. Within the same data acquisition time a three-fold increase in SNR is achieved when compared to the scanning method, with ways for a further improvement outlined.