Mode locking in a free-electron laser amplifier

Thompson, N R and McNeil, B W J (2008) Mode locking in a free-electron laser amplifier. Physical Review Letters, 100 (20). 203901. ISSN 0031-9007 (

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A technique is proposed to generate attosecond pulse trains of radiation from a free-electron laser amplifier. The optics-free technique synthesizes a comb of longitudinal modes by applying a series of spatiotemporal shifts between the copropagating radiation and electron bunch in the free-electron laser. The modes may be phase locked by modulating the electron beam energy at the mode spacing frequency. Three-dimensional simulations demonstrate the generation of a train of 400 as pulses at gigawatt power levels evenly spaced by 2.5 fs at a wavelength of 124 A. In the x-ray at wavelength 1.5 A, trains of 23 as pulses evenly spaced by 150 as and of peak power up to 6 GW are predicted.


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