Highly-stable, flexible delivery of microjoule-level ultrafast pulses in vacuumized anti-resonant hollow- core fibers for active synchronization

Timing distribution technique, based on active synchronization of ultrafast optical pulses, has been widely used in a variety of large-scale laser and accelerator facilities, providing unprecedented temporal precision. We demonstrate the stable and flexible light delivery of multi-μJ, sub-200-fs pulses over a ~10-m-long vacuumized anti-resonant hollow-core fiber (AR-HCF), which was successfully used for high-performance pulse synchronization. Compared with the pulse train launched into the AR-HCF, the transmitted pulse train out of the fiber exhibits excellent stabilities in pulse power and spectrum, with pointing stability largely improved. The walk-off between the fiber-delivery and the other free-space-propagation pulse trains, in an open loop, was measured to be <6 fs root-mean-square (RMS) over 90 minutes, corresponding to a relative optical-path variation of <2×10 -7 . This walk-off can be further suppressed to ~2 fs RMS simply using an active control loop, highlighting the great application potentials of this AR-HCF set-up in large-scale laser and accelerator facilities.