Chirped Seeded Free-Electron Lasers: Self-Standing Light Sources for Two-Color Pump-Probe Experiments

Abstract

We demonstrate the possibility of running a single-pass free electron laser (FEL) in a dynamical regime, which can be exploited to perform two-color pump-probe experiments in the vacuum ultraviolet or x-ray domain, using the free-electron laser emission both as a pump and as a probe. The studied regime is induced by triggering the free-electron laser process with a powerful laser pulse, carrying a significant and adjustable frequency chirp. As a result, the output FEL radiation is split in two pulses, separated in time (as previously observed by different authors), and having different central wavelengths. We show that both the spectral and temporal distances between FEL pulses can be independently controlled. We also provide a theoretical description of this phenomenon, which is found in good agreement with experiments performed on the FERMI@Elettra free-electron laser.

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

“…Newly developed capabilities at x-ray free-electron lasers (XFELs) allow for the production of two intense x-ray pulses with a controlled time delay [1][2][3][4][5][6]. Those capabilities open the possibility to track, with femtosecond resolution, x-rayinduced phenomena in matter.…”

Free-Electron Laser Design for Four-Wave Mixing Experiments with Soft-X-Ray Pulses

“…Detailed numerical simulations are used to illustrate the more impressive characteristics of this scheme. The unequivocal success of existing x-ray free-electron lasers (XFELs) such as FLASH [1], LCLS [2], SACLA [3], and Fermi@elettra [4] has been followed by further development and demonstration of expanded facility capabilities such as implementation of hard x-ray self seeding at LCLS [5], obtaining two-pulse, two-color jitter free x rays at LCLS [6,7] and Fermi@elettra [8,9], and improvements in the temporal coherence of SASE at LCLS [10]. The high intensity electromagnetic fields produced by XFELs could also allow us to extend a vast arsenal of nonlinear optics techniques to x rays [11][12][13][14][15].…”

Echo-Enabled Harmonic Generation Studies for the FERMI Free-Electron Laser

“…Besides having the potential to produce fully coherent, transform-limited pulses [24], the scheme offers a natural way to control the spectrotemporal and spatial properties of the FEL pulse, by shaping the seed [25,26]. Furthermore, fine control over the output wavelengths in double-color operation can be achieved, either by using a single seed and a strongly chirped e-beam [27], or by using two seed lasers operating at different wavelengths [28].…”