Breaking the Femtosecond Barrier in Multi-Kilometer Timing Synchronization Systems

Abstract

To observe electronic dynamics in atoms, molecules, and condensed matter taking place on an attosecond time scale, next-generation photon science facilities like X-ray free-electron lasers and intense laser beamlines require system-wide attosecondlevel synchronization of dozens of optical and microwave signals up to kilometer distances. Here, we present for the first time a timing synchronization system that can meet the strict timing requirements of such large-scale facilities. We discuss some key enabling technologies including master-laser jitter characterization, local timing synchronization, new designs of attosecond-precision timing/phase detectors, and analyze fundamental noise contributions in nonlinear pulse propagation in fiber links. Finally, a complete 4.7-km laser-microwave network with 950-as timing jitter is realized over tens of hours of continuous operation.

Noise Measurement and Reduction in Mode-Locked Lasers: Fundamentals for Low-Noise Optical Frequency Combs

“…Since then, the BOC technique has been widely applied in timing jitter measurement of various types of mode-locked lasers, e.g., solid-state mode-locked lasers [59][60][61], fiber mode-locked lasers [62][63][64][65][66], and fiber amplifiers [67,68] due to its practicality. Later in 2016, Xin et al improved the BOC technique and proposed the polarization-noise-suppressed balanced optical correlation (PNS-BOC) technique [69]. Through the insertion of a birefringence crystal before the optical correlator, the crosstalk between the pulses with orthogonal polarization states can be suppressed, leading to an improved SNR of error signals.…”

Synchronous multi-color laser network with daily sub-femtosecond timing drift

“…Three distant lasers are synchronized in a star network topology across two different timing-stabilized fiber links with 4.7-km total length. We apply the pulsed timing synchronization scheme [27][28][29] using balanced optical cross correlators (BOC) 19 to stabilize the signal delay through polarization-maintaining (PM) fiber links as well as to synchronize the remote slave lasers at the link outputs. Our master laser is a commercially available modelocked laser (Origami-15 from OneFive GmbH) operating at 216.67-MHz repetition rate with 1554-nm center wavelength and 172-fs pulse duration.…”

“…Here, we demonstrate a synchronous multi-color modelocked laser network distributed over 4.7-km distance with daily sub-femtosecond timing drift. The laser network is based on the pulsed timing synchronization scheme [27][28][29] which uses a modelocked laser with 1550-nm center wavelength as its master oscillator. Unlike the cw approach, the optical signal of the master laser is transmitted directly to the slave lasers via timingstabilized fiber links where synchronization has been achieved by four-wave mixing between the link outputs and the slave lasers.…”

Sub‐10‐fs Timing for Ultrafast Electron Diffraction with THz‐Driven Streak Camera

“…This approach has been used for improving the temporal stability of UED and FELs. [ 24,38–42 ] In this work, we used a differential‐biased fiber Sagnac‐loop‐interferometer‐based phase detector, named the FLOM‐PD, for stable RF‐to‐laser synchronization. More detailed information of FLOM‐PD can be found in other references.…”