We have measured the average single-pulse longitudinal coherence characteristics of FLASH, a self amplified spontaneous emission free electron laser, at extreme UV wavelengths. Electric field autocorrelation measurements in the time domain were enabled by a wavefront division beam splitter applied to a tunable delay Mach–Zehnder interferometer. These data agree with the spectral bandwidth measurements made in the frequency domain. They exhibit two correlation time scales and the measured coherence curves have relevant implications for single-shot measurements.
© 2010 Optical Society of America
Original Manuscript: September 15, 2009
Revised Manuscript: November 21, 2009
Manuscript Accepted: November 23, 2009
Published: January 28, 2010
W. F. Schlotter, F. Sorgenfrei, T. Beeck, M. Beye, S. Gieschen, H. Meyer, M. Nagasono, A. Föhlisch, and W. Wurth, "Longitudinal coherence measurements of an extreme-ultraviolet free-electron laser," Opt. Lett. 35, 372-374 (2010)