论文标题
高增益谐波产生，具有时间重叠的种子脉冲并应用于超快光谱法
High-Gain Harmonic Generation with temporally overlapping seed pulses and application to ultrafast spectroscopy
论文作者
论文摘要
自由电子激光器（FEL）中高增生谐波产生（HGHG）过程的界线双脉冲播种是一种有前途的方法，可促进极端紫外线（XUV）光谱范围内各种相干非线性光谱方案。但是，在使用单个非线性介质的共线排列中，时间重叠的种子脉冲可能会引入非线性混合信号，从而在短时间内损害实验。在这里，我们通过扩展最近出版物中描述的分析（Wituschek等，Nat。Commun。，11，883，2020）中所述的分析来详细研究这些效果。在光子能量> $ 23 \，$ eV的高阶自相关和波包干涉测量实验中，进行了数值模拟。事实证明，自相关和波包干涉仪数据对饱和效应非常敏感，因此可以用于表征HGHG过程中的饱和度。我们的结果进一步表明，即使在时间延迟的时间延迟小于种子脉冲持续时间内，时间分辨的光谱实验也是可行的。
Collinear double-pulse seeding of the High-Gain Harmonic Generation (HGHG) process in a free-electron laser (FEL) is a promising approach to facilitate various coherent nonlinear spectroscopy schemes in the extreme ultraviolet (XUV) spectral range. However, in collinear arrangements using a single nonlinear medium, temporally overlapping seed pulses may introduce nonlinear mixing signals that compromise the experiment at short time delays. Here, we investigate these effects in detail by extending the analysis described in a recent publication (Wituschek et al., Nat. Commun., 11, 883, 2020). High-order fringe-resolved autocorrelation and wave-packet interferometry experiments at photon energies > $23\,$eV are performed, accompanied by numerical simulations. It turns out that both the autocorrelation and the wave-packet interferometry data are very sensitive to saturation effects and can thus be used to characterize saturation in the HGHG process. Our results further imply that time-resolved spectroscopy experiments are feasible even for time delays smaller than the seed pulse duration.
