We performed what we believe are the first practical full-temporal-characterization measurements of ultrashort pulses from a free-electron laser (FEL). Second-harmonic-generation frequency-resolved optical gating (FROG) was used to measure a train of mid-IR pulses distorted by a saturated water-vapor absorption line and showing free-induction decay. The measured direction of time was unambiguous because of prior knowledge regarding free-induction decay. These measurements require only 10% of the power of the laser beam and demonstrate that FROG can be implemented as a pulse diagnostic simultaneously with other experiments on a FEL.
© 1997 Optical Society of America
B. A. Richman, M. A. Krumbügel, and R. Trebino, "Temporal characterization of mid-IR free-electron-laser pulses by frequency-resolved optical gating," Opt. Lett. 22, 721-723 (1997)