Extreme ultraviolet free electron laser seeded with high-order
harmonic of Ti:sapphire laser

Abstract

The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as a seeding source to a 250-MeV free-electron-laser (FEL) amplifier. When the amplification conditions were fulfilled, strong enhancement of the radiation intensity by a factor of 650 was observed. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission (SASE) based FEL radiation without the seeding source, were found to be suppressed drastically to form to a narrow-band, single peak profile at 61.2 nm. The properties of the seeded FEL radiation were well reproduced by numerical simulations. We discuss the future precept of the seeded FEL scheme to the shorter wavelength region.

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser

“…The seed transfers its longitudinal coherence properties to the FEL pulse [8], and schemes based on this principle were proposed to improve the longitudinal coherence of FELs operating in a self amplified spontaneous emission mode [9][10][11], where the temporal pulse structure is dominated by stochastic fluctuations associated with the initial shot noise [12]. The seed amplification, combined with the generation of coherent harmonics, has been demonstrated first in the midinfrared [8,13] and then in the UV-VUV range [14][15][16][17]. User facilities based on the frequency up-conversion of a seed laser in the VUV soft-x-ray region of the spectrum are now in operation and provide radiation with unprecedented properties of longitudinal coherence [18].…”

Stabilization of a high-order harmonic generation seeded extreme ultraviolet free electron laser by time-synchronization control with electro-optic sampling

“…In the case of our former experiment in 2010 [12] , according to this definition, the effective hit rate was calculated as 0.3%. Figure 6 shows the correlation data plot between the spectral peak intensity of the output pulse subtracted by the average SASE intensity and the wavelength of the peak intensity in the data for 10,000 shots with seeded FEL operation in 2012.…”

“…These correspond to the 13th (61.5 nm) and 15th (53.3 nm) harmonics of a Ti:S laser (central wavelength: 800 nm). In 2010, we achieved the first successful seeding of the SCSS EUV-FEL at the 13th harmonic of the Ti:S laser [12] . However, the low contrast ratio of the pulse energy of the seeded FEL pulses with respect to the SASE background noise as well as the low probability of successful seeding events were not favoured for user experiments.…”

Synchronization of FEL and high-order harmonics of ultrashort-pulsed laser for generating intense full-coherent EUV light pulses

“…The pulse energy of the seeded FEL and SASE pulses were measured by a calibrated Ar gas monitor [8]. The averaged intensity of the seeding pulses was measured by the EUV spectrometer, and the pulse energy of the seeding pulses was estimated to be 2 nJ by comparing the averaged spectral intensity of the seeding pulses with the spectral intensity of the SASE pulses [9].…”