Enormous Amplification of Full-Coherent Radiation in the Extreme Ultraviolet Region with a Free-Electron Laser

摘要

High-order harmonic beam was injected as a seeding source to a 250-MeV free-electron-laser amplifier. When the amplification conditions were satisfied, strong enhancement of the radiation intensity by a factor of 650 was observed at a wavelength of 61.5 nm. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission based FEL radiation without the seeding pulse, were found to be suppressed drastically to form to a narrow-band, single peak profile at the seeding wavelength. The properties of the seeded FEL radiation were well reproduced by numerical simulations.