Interferometric pump–probe experiments in the extreme ultraviolet (XUV) domain are experimentally very challenging due to the high phase stability required between the XUV pulses. Recently, an efficient phase stabilization scheme was introduced for seeded XUV free electron lasers (FELs) combining shot-to-shot phase modulation with lock-in detection Wituschek et al (2020 Nat. Commun. 11 883). This method stabilized the seed laser beampath on the fundamental ultraviolet wavelength to a high degree. Here, we extend this scheme including the stabilization of the XUV beampath, incorporating phase fluctuations from the FEL high gain harmonic generation process. Our analysis reveals a clear signal improvement with the new method compared to the previous stabilization scheme.

中文翻译：

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改进的极紫外量子干涉实验稳定方案

由于 XUV 脉冲之间所需的高相位稳定性，极紫外 (XUV) 域中的干涉泵-探针实验在实验上非常具有挑战性。最近，针对种子 XUV 自由电子激光器 (FEL) 引入了一种有效的相位稳定方案，该方案结合了发射到发射相位调制和锁定检测 Wituschek等人(2020纳特。公社。 11883). 该方法高度稳定了基本紫外波长上的种子激光束路径。在这里，我们扩展了该方案，包括 XUV 光束路径的稳定性，并结合了 FEL 高增益谐波生成过程中的相位波动。我们的分析表明，与之前的稳定方案相比，新方法明显改善了信号。