Echo enabled harmonic generation free electron laser in a mode-locked configuration

Echo Enabled Harmonic Generation (EEHG) is a method of harmonic up-shifting proposed to extend the temporal coherence properties of Free Electron Lasers (FEL) at shorter wavelengths where coherent laser seed fields are not available. Previous theoretical studies of EEHG have applied periodic boundary conditions to the electron distribution in phase space. It is shown that when these periodic boundary conditions are removed a temporal comb of enhanced electron microbunching is revealed. By matching this comb structure in the electron microbunching to the radiation modes that are generated in a Mode-Locked Optical Klystron (MLOK) FEL configuration, a train of short radiation pulses can be generated. Copyright (c) EPLA, 2012