Full Characterization of Few-Fs Pulses Tunable in the Vacuum Ultraviolet

Few-fs-long light pulses tunable across the ultraviolet (UV) are highly anticipated for the study of ultrafast valence electron dynamics in many materials. A recently introduced technique relying on resonant dispersive-wave (RDW) generation during solitonic propagation inside a gas-filled hollow capillary [1] can produce such pulses, ideally suited for time-resolved UV spectroscopy. However, the handling and especially the characterization of such pulses remain extremely challenging due to excessive material dispersion in the vicinity of resonances. Up to now sub-3 fs pulses tunable between 250 and 350 nm could be successfully measured by an all-optical self-diffraction frequency resolved optical gating (SD-FROG) device [2]. However, such optical methods break down at the even shorter wavelengths of the vacuum ultraviolet (VUV, 100–200 nm).