Temporal characterization of tunable few-cycle vacuum ultraviolet pulses

Abstract In the past few decades, the development of ultrafast lasers has revolutionized our ability to gain insight into light–matter interactions. The emergence of few-cycle light sources operating from the visible to the mid-infrared spectral range—as well as attosecond extreme ultraviolet and X-ray technologies—provide the possibility to directly observe and control ultrafast electron dynamics in matter on their natural timescale; however, the temporal characterization of few-femtosecond sources in the deep ultraviolet (4–6 eV, 300–200 nm) and the vacuum ultraviolet (VUV; 6–12 eV, 200–100 nm) spectral regions is challenging. Here we fully characterize the temporal shape of microjoule-energy VUV pulses tuned between 160 and 190 nm generated via resonant dispersive wave emission during soliton self-compression in a capillary using frequency-resolved optical gating based on two-photon photoionization in noble gases. The in situ measurements reveal that in most of the cases the pulses are shorter than 3 fs. These findings pave the way toward investigating ultrafast electron dynamics and valence excitation of a large class of atoms and molecules with a time-resolution that has been hitherto inaccessible when using VUV pulses.