Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses.

Area of Science:

• Ultrafast spectroscopy
• X-ray science
• Chemical dynamics

Background:

• Femtosecond X-ray light sources enable probing chemical and structural changes in the 10-100 fs range.
• Existing timing systems at X-ray Free-Electron Laser (XFEL) facilities often have jitter exceeding 50 fs, limiting synchronization precision.
• Active stabilization schemes lack the precision required for synchronizing X-ray and optical pulses at the femtosecond scale.

Purpose of the Study:

• To review and detail the "measure-and-sort" technique for precise X-ray/optical pulse synchronization.
• To demonstrate a method for achieving timing resolution below 10 fs root mean square (rms).
• To enable high-precision pump-probe experiments at the femtosecond timescale.

Main Methods:

• Utilizing single-shot timing measurements for event processing and data sorting.
• Measuring the relative arrival time between X-ray and optical pulses using a spectrally encoded cross-correlation signal.
• Implementing filter-and-sort algorithms for real-time data processing based on time-stamps.

Main Results:

• The "measure-and-sort" technique achieves sub-10 fs rms timing resolution.
• This timing precision is comparable to the duration of the shortest available X-ray pulses.
• The method effectively accommodates limitations in active stabilization schemes.

Conclusions:

• The "measure-and-sort" approach provides a robust solution for synchronizing X-ray and optical pulses with unprecedented precision.
• This technique is vital for advancing X-ray/optical pump-probe experiments studying ultrafast phenomena.
• High timing resolution is achievable and essential for exploring chemical and structural dynamics at the femtosecond scale.