Seed level requirement for improving the temporal coherence of a Free-Electron LaserG. Lambert1, 2, 3, T. Hara4, M. Labat3, 5, T. Tanikawa4, 6, Y. Tanaka4, M. Yabashi4, D. Garzella3, B. Carré3 and M. E. Couprie2
1 Laboratoire d'Optique Appliquée, ENSTA-CNRS-Polytechnique - Chemin de la Hunière, 91761 Palaiseau, France, EU
2 Synchrotron SOLEIL - Saint Aubin, BP 34, 91192 Gif-sur-Yvette, France, EU
3 IRAMIS/SPAM CEA-Saclay - 91191 Gif-sur-Yvette, France, EU
4 XFEL Project Head Office/RIKEN - 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
5 ENEA C.R. - Frascati, RM, Italy, EU
6 UVSOR facility, IMS - Okazaki 444-8585, Japan
received 9 September 2009; accepted in final form 17 November 2009; published December 2009
published online 15 December 2009
The temporal coherence of Free-Electron Laser (FEL) sources, which exhibit, in the self-amplified spontaneous-emission mode, spiking spectral and temporal distributions, can be drastically improved by seeding with an external laser or high-order harmonics. Here, experiments at 160 nm put in evidence that the improvement of spectral properties (and thus temporal coherence) of the FEL radiation takes place for a larger seed intensity than the one required to overcome the shot noise.
41.60.Cr - Free-electron lasers.
42.65.Ky - Frequency conversion; harmonic generation, including higher-order harmonic generation.
© EPLA 2009