Generation of short pulses of coherent electromagnetic radiation in a free-electron laser amplifier

Theoretical and experimental studies of the evolution of a frequency-chirped pulse under the influence of both phase and gain dispersion effects induced by the free-electron laser interaction are presented. For the experimental parameters used (electron beam voltage V=150 kV, wiggler periodicity l/sub w/=3.5 cm, gain approximately 10 dB, input pulse width Delta t approximately 200 ns, frequency w/sub 0//2 pi =10 GHz, and frequency chirp alpha /2 pi approximately 5 MHz/ns), pulses of a few nanoseconds were generated after an interaction length of 2.30 m, in good agreement with theoretical expectations.<>