Scientists at the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences have proposed and validated a novel approach for single-shot characterization of ultrashort free-electron laser pulses based on self-referenced spectral interferometry. Their innovative approach, published in Physical Review Letters, offers a promising solution to the challenges of ultrafast scientific experiments.
Attosecond light pulses can be used to observe and manipulate the electronic motion in atoms and molecules, thus helping scientists to gain a deeper understanding of chemical reactions, electronic structures, and molecular dynamics. The complete spectrotemporal characterization of attosecond X-ray free-electron lasers is of great significance to ultrafast scientific experiments. However, the precise single-shot characterization of these pulses has been a major bottleneck in the application of attosecond X-ray free-electron lasers.
Led by Prof. FENG Chao, the researchers have innovatively proposed a approach of using the frequency-pulling effect as a way to induce the spectral shear. This approach allows the generation of both the ultrafast radiation pulse and the reference pulse from the same electron beam, enabling self-referenced spectral interferometry of the radiation pulse.
With the help of the parameters of the Shanghai soft X-ray free-electron laser facility, the researchers demonstrated that this approach can accurately reconstruct the complete spectrotemporal information of attosecond X-ray pulses, with a reconstruction error rate of less than 6%.
Compared to traditional ultrafast pulse characterization methods in free-electron laser facilities, this approach has several advantages. It employs simple equipment, yet achieves high diagnostic efficiency in real-time and single-shot measurements,
Simultaneously, it provides complete spectrotemporal information and higher diagnostic precision for shorter radiation pulses. These advantages present a unique diagnostic approach for optimizing and fine-tuning ultrafast X-ray free-electron lasers and future attosecond scientific experiments based on X-ray free-electron lasers.
This study marks a significant breakthrough in high-precision real-time diagnostics for attosecond free-electron laser pulses.
Schematic layout of the proposed method and spectrotemporal reconstructions of attosecond X-ray free-electron laser pulses (Image by SARI)