High-order-harmonic generation and superradiance in a seeded free-electron laser.
Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys. Rev. 93, 99 (1954).] has been observed. Superradiance has been induced by seeding a single-pass amplifier with the second harmonic of a Ti:sapphire laser, generated in a β-Barium borate crystal, at seed intensities comparable to the free-electron laser saturation intensity. Pulse energy and spectral distributions of the harmonics up to the 11th order have been measured and compared with simulations.
ENEA C.R. Frascati, Via E. Fermi, 45 00044 Frascati, Roma, Italy. Luca.Giannessi@enea.it
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