Speaker
Description
Synchrotrons and X-ray free electron lasers (XFEL) are intrinsically pulsed sources of light, which makes them ideal tools for time-resolved measurements. A wide range of ultrafast X-ray imaging techniques have been well established, and are now being widely utilized at numerous facilities worldwide. However, all of these methods require an averaging over an extended period of time (or a large number of pulse repetitions) to yield a high-quality image. Consequently, they are only capable of capturing highly reproducible and triggerable sample dynamics.
At the same time, many nanometer-scale systems exhibit fluctuations and stochastic processes, particularly in the presence of disorder. Recently, a new experimental method called Coherent Correlation Imaging (CCI) has been introduced [1]. This is a high-resolution, full-field microscopy technique that realizes multi-shot, time-resolved imaging of stochastic dynamics. The central idea of CCI is the classification of Fourier-space coherent diffraction patterns – even at a low photon count, where single-shot imaging is not feasible. This enables a selective averaging of the same-state frames, which are then converted into real-space images by a holographically-assisted iterative phase retrieval algorithm [2, 3].
In my talk, I will demonstrate the first implementations of CCI at XFELs that allow detection of ultrafast stochastic dynamics. We employ this new technique to resolve infra-red laser- and X-ray-induced nanometer-scale transformations of magnetic textures in ferromagnetic thin films. Our results establish CCI as a powerful, non-destructive imaging method, capable of revealing ultrafast stochastic phenomena that were previously inaccessible by conventional pump–probe or single-shot techniques.
[1] Klose, C. et. al. Nature 614, 256 (2023).
[2] Zayko, S. et al. Nat. Commun. 12, 6337 (2021).
[3] Battistelli, R. et al. Optica 11, 234 (2024).
| Scientific Topics | Imaging |
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