Towards better temporal diagnostics of ultrafast pulses from free-electron lasers

4 March 2021

Spatially encoded measurements of transient optical transmissivity became a standard tool for temporal diagnostics of free-electron-laser (FEL) pulses. The modern experimental techniques can measure changes in such optical coefficients with a temporal resolution better than 10 fs. This, in an ideal case, would imply a similar resolution for the temporal pulse properties and the arrival time jitter between the FEL and optical laser pulses. The observed changes of transient optical coefficients are due to the emergent carriers, electron and holes, produced in the X-ray excited material. However, additional processes such as carrier transport and carrier recombination can make the diagnostic measurement inaccurate. In a combined experimental and theoretical study, an international team, with participating IFJ PAN scientists, identified the main processes contributing to the unwanted escape of carriers during diagnostic measurement. By controlling their contribution in future applications, one can gain a very high temporal resolution for the reconstruction of FEL pulse properties measured with semiconductor based diagnostic tools.

Scientific papers:

„Effect of Auger recombination on transient optical properties in XUV and soft X-ray irradiated silicon nitride”
V. Tkachenko et al.;
Scientific Reports (2021)