Kaertner, RLE/EECS team set new standards for high precision synchronization

November 5, 2008

As announced in the Nov. 4, 2008 Research Laboratory of Electronics, RLE, press release, EECS Professor and senior member of the RLE Optics and Quantum Electronics Group, Franz X. Kaertner, and his research team have reported in the Nov. 2, 2008 online issue of Nature Photonics, a set of techniques for long-term stable timing synchronization based on mode-locked lasers. This achievement is an important milestone in transitioning mode-locked laser-based synchronization systems from the laboratory into real-world systems.

The need by existing large-scale facilities for such femtosecond accuracy for many hours of continuous operation makes this an achievement for both immediate and long term application. For example, advanced X-ray free-electron lasers (FELs)--some under construction and others planned in the near future--currently require this kind of high precision timing accuracy. Another application that can benefit from this advance is the phased-array antenna for radio astronomy such as the Atacama Large Millimeter Array (ALMA). The demonstrated accuracy of synchronization--equivalent to keeping the timing within less than one second error since the birth of the universe--can also significantly enhance the synchronization of future communication and computation networks as well as the performance of positioning and tracking systems.

The work by the Kaertner team, including first author Dr. Jungwon Kim, EECS PhD '07, and currently postdoctoral associate in RLE, and EECS graduate students Jonathan Cox and Jian Chen, was begun four years ago in the face of skepticism that this kind of precision and stability with femtosecond mode-locked lasers could be achieved. Now, as reported in their Nature Photonics paper, the EECS RLE team has reached, for the first time, sub-10 femtosecond timing accuracy maintained over 10 hours and over distances of more than 300 meters.

The research was funded by the European Union, under the EuroFEL program; the U.S. Office of Naval Research (ONR), under the Multidisciplinary University Research Initiative (MURI) program; the U.S. Air Force Office of Scientific Research (AFOSR); the U.S. Defense Advanced Research Projects Agency (DARPA); the University of Wisconsin; and the Samsung Scholarship Foundation.

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