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.

锁相激光脉冲对是许多先进光谱学研究的重要工具。这项工作研究了充气空心光纤（HCF）中几个周期脉冲对的传播动力学，旨在生成超短脉冲对，通过谐振色散波发射在真空紫外（VUV）范围内可调。尽管时间上分开，但脉冲对中的第二个脉冲在前导脉冲之后看到了薄等离子体（前等离子体）。虽然预等离子体通常会随着电子密度的增加而降低第二脉冲的VUV转换效率，但发现对于短于140 nm的波长，效率被很大程度上抑制，但对于较长的VUV波长，预等离子体的影响较小。分析表明，对前等离子体的不同响应是由克尔效应的大小决定的，而不是由电子密度决定的。进一步表明，根据实验实现，可以通过增加第二个脉冲的能量来补偿 VUV 输出的抑制。还分析了影响真​​空紫外光谱条纹的其他因素。这项工作为许多前沿研究获得独特的真空紫外光源铺平了道路。