Vacuum-ultraviolet dispersive wave emission driven by phase-locked pulse pairs in a gas-filled hollow-core fiber: a numerical study

Phase-locked laser pulse pairs are important tools in many advanced spectroscopy researches. This work investigated the propagation dynamics of a few-cycle pulse pair in a gas-filled hollow-core fiber (HCF), aiming at generation of ultrashort pulse pair, tunable in the vacuum ultraviolet (VUV) range through resonant dispersive wave emission. Although separated temporally, the 2nd pulse in the pulse pair sees a thin plasma (pre-plasma) in the wake of the leading pulse. While the pre-plasma generally reduces the 2nd pulse’s VUV conversion efficiency with the increase of electron density, it is found that for wavelengths shorter than 140 nm, the efficiency is largely suppressed, but for longer VUV wavelengths the pre-plasma has small effects. Analysis reveals that the different response to pre-plasma is determined by the magnitude of Kerr effect, instead of the electron density. It is further shown that the suppression of the VUV output can be compensated by increasing the 2nd pulse’s energy depending on the experimental implementations. Other factors that affect the VUV spectral fringes are also analyzed. This work paves the way to achieving unique VUV sources for many cutting-edge researches.