Self-amplified coherent spontaneous emission in the planar wiggler free-electron laser

Coherent spontaneous emission (CSE) is a potentially important self-generated source of seed radiation in a free-electron laser (FEL) amplifier. A model is derived that describes CSE at the fundamental resonant frequency and its harmonics in a planar wiggler FEL. The subsequent self-amplification of the CSE is investigated in the nonlinear regime for a FEL amplifier configuration