发表机构
Lund University; ASML Research, ASML Netherlands B.V.（隆德大学; ASML研究部，ASML荷兰有限公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用后压缩掺镱激光器在氖气中研究高次谐波产生，发现等离子体对驱动场的重塑显著影响相位匹配，并提出了轴上相位匹配模型来解释谱移现象。
AI 中文摘要
从钛蓝宝石到掺镱激光技术的转变，使得在高重复频率下实现高次谐波产生（HHG）装置的即插即用成为可能，从而开辟了新的应用，例如在半导体计量学中。然而，这需要探索和理解新实验条件的影响。在此，我们利用后压缩的掺镱激光器，在8-17纳米光谱范围内以高光谱分辨率研究氖气中的HHG。我们的测量揭示了一个大的随脉冲能量和气压变化的谱移，跨越超过两个谐波级次。谐波发射的飞秒啁啾与基频场的蓝移相结合，使我们能够将观察到的谱移与由相位匹配决定的谐波产生时间窗口联系起来。为了理解这些动力学，考虑驱动激光场在等离子体内部的重新塑形至关重要，尽管驱动强度低且脉冲持续时间长。我们引入了一种轴上相位匹配描述，该描述捕捉了这些效应并再现了实验和模拟的趋势。这些结果表明了等离子体诱导的激光重塑在HHG相位匹配中的核心作用，在多参数优化源时应予以考虑。
英文摘要
The transition from titanium-sapphire to ytterbium-based laser technology enables turnkey implementations of high-order harmonic generation (HHG) setups at high repetition rates, opening up new applications, e.g., in semiconductor metrology. This, however, requires exploring and understanding the impact of new experimental conditions. Here, we study HHG in neon over the spectral range 8-17 nm with high spectral resolution, using a post-compressed ytterbium laser. Our measurements reveal a large pulse-energy- and pressure-dependent spectral shift, spanning more than two harmonic orders. The femto-chirp of the harmonic emission combined with the blueshift of the fundamental field allows us to relate the observed spectral shifts to the temporal window of harmonic generation, which is determined by phase-matching. To understand these dynamics, it is essential to consider the reshaping of the driving laser field inside the plasma, despite the low driving intensity and long pulse duration. We introduce an on-axis phase-matching description that captures these effects and reproduces the experimental and simulated trends. These results demonstrate the central role of plasma-induced laser reshaping in phase-matching of HHG, which should be accounted for when optimizing sources in a multi-parameter landscape.
Comments27 pages, 8 figures
