The study of core electron dynamics through nonlinear spectroscopy requires intense isolated attosecond extreme ultraviolet or even X-ray pulses. A robust way to produce these pulses is high-harmonic generation (HHG) in a gas medium. However, the energy upscaling of the process depends on a very demanding next-generation laser technology that provides multi-terawatt (TW) laser pulses with few-optical-cycle duration and controlled electric field. Here, we revisit the HHG process driven by 16-TW sub-two-cycle laser pulses to reach high intensity in the 100-eV spectral region and beyond. We show that the combination of above barrier-suppression intensity with a long generation medium significantly enhances the isolation of attosecond pulses compared to lower intensities and/or shorter media and this way reduces the pulse duration as well as field-stability requirements on the laser driver. This novel regime facilitates the real-time observation of electron dynamics at the attosecond timescale in atoms, molecules, and solids.

中文翻译：

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在100 eV光谱区域中增强传播的高谐波高连续谱的产生

通过非线性光谱学对核心电子动力学的研究需要强烈的孤立的阿秒极端紫外线或什至X射线脉冲。产生这些脉冲的可靠方法是在气体介质中产生高谐波（HHG）。但是，过程的能量放大取决于非常苛刻的下一代激光技术，该技术可提供光周期短且电场受控的多兆瓦（TW）激光脉冲。在这里，我们将重温由16-TW亚二周期激光脉冲驱动的HHG过程，使其在100-eV光谱范围内以及更高范围内达到高强度。我们表明，与较低的强度和/或更短的介质相比，上述势垒抑制强度与长寿命介质的组合显着增强了阿秒脉冲的隔离，并且这种方式减少了脉冲持续时间以及对激光驱动器的场稳定性要求。这种新颖的机制有助于在原子级，分子级和固体级的亚秒级时间尺度上实时观察电子动力学。