COHERENT TRANSIENTS IN THE FREE-ELECTRON LASER - LASER LETHARGY AND COHERENCE BRIGHTENING

The propagation of picosecond electron and optical pulses in the free-electron laser is studied using the coupled Maxwell and Boltzmann (quasi-Bloch) equations. The system exhibits phenomena similar to laser lethargy and swept-gain superradiance. By shortening the optical transit time of the cavity with respect to the repetition rate of the electron pulses optimized conditions are obtained. The shape of the velocity distribution of the emerging electrons is then in agreement with the Stanford experiments. © 1979.