Phase locking in an infrared short-pulse free-electron laser

The feasibility of the phase-locking procedure for the external selection of a single mode with reasonable power has been tested by simulation of the optical pulse evolution in a short-pulse free-electron laser using a model based on the self-consistent solution of the equations of motion for the electrons and the wave equation driven by single-particle currents. The simulations show that a high degree of coherence between successive pulses can be induced by a low-finesse etalon. Saturated operation in a greatly reduced number of modes, but with the same total power, is attained with a slight delay in the growth of the power as compared to the case without phase locking