Synchronous Mode-locked Laser Network with Sub-fs Jitter and Multi-km Distance

Abstract

Abstract:We report a synchronous multi-color mode-locked laser network over 4.7-km distance. Output of two remotely synchronized lasers shows only 0.6-fs RMS drift over 40 hours reaching 20 th decimal uncertainty in less than 10000-s averaging time.OCIS codes: (060.1155) All-optical networks; (140.4050) Mode-locked lasers; (120.5050) Phase measurement IntroductionMode-locked lasers continue to revolutionize the fields of frequency metrology and laser spectroscopy due to their ultra-low noise properties. To realize the long standing scientific dream of capturing ultrafast structural dynamics with atomic resolution, new generation scientific facilities such as X-ray free-electron lasers [1] and intense laser beamline centers [2] aim to synchronize numerous mode-locked lasers with sub-fs precision across km-distances [3,4]. Similarly, comparison of remote optical clocks requires stabilized mode-locked lasers at each clock location to transfer the ultra-stable optical frequency to radio frequency (RF) domain as well as to the slave laser frequency responsible for the fiber-optic transmission [5]. Here we demonstrate a multi-color long-term stable synchronous mode-locked laser network with sub-fs precision and 4.7-km distance using balanced optical cross-correlators (BOC). Out-of-loop timing drift between two remote lasers is only 0.6 fs RMS over 40 hours corresponding to a timing instability of 1.2×10 -20 at 70000-s averaging time.

Breaking the Femtosecond Barrier in Multi-Kilometer Timing Synchronization Systems

“…For shorter link lengths (e.g., ∼300 m), because of lower required link operational power and smaller residual link dispersion, a better timing precision can be expected. Our technique can be easily transferred to multi-wavelength-laser networks [67], [68] with the help of two-color BOC [69], [70], and large-scale microwave networks with μrad precision [71]. The attosecond-precision laser-microwave network will enable next-generation FELs and other science facilities to operate with the unprecedented timing precision, thereby unfolding their full potential.…”