Light Sci. Appl. 6, e16187 (2017)

Credit: HTTP://CREATIVECOMMONS.ORG/LICENSES/BY/4.0/

A kilometre-scale synchronous network linking optical and microwave devices with attosecond precision has been developed by a team of scientists from the Center for Free-Electron Laser Science in Hamburg, Germany and Massachusetts Institute of Technology (MIT) in the USA. Such networks will prove useful for X-ray science experiments relying on free-electron lasers (FELs) that require attosecond-level synchronization of optical and microwave signals across large distances, and may also benefit applications in geodesy, long-baseline interferometry and multi-telescope arrays. By mitigating the effects of optical fibre nonlinearity and sources of noise the team achieved stabilization of a 4.7-km-long fibre network with a timing jitter of just 580 attoseconds (root mean square) for over 40 hours. A complete laser-microwave network operated with a timing jitter of 950 attoseconds over a period of 18 hours. The ability to control the timing of FELs with this level of precision will be useful to make atomic and molecular movies at the attosecond timescale, thus aiding investigations in biology, drug development, materials science and fundamental physics.