强激光驱动固体表面等离子体高次谐波光源产生与表征

Development and characterization of intense laser-induced surface-plasma high-harmonic generation

  • 摘要: 超强超短激光技术为强场物理、超快动力学及新物态研究提供了极端非线性相互作用的独特平台。在强激光驱动下,固体/液体表面等离子体相互作用产生的表面高次谐波(Surface High Harmonic Generation, SHHG)具备高单脉冲能量、阿秒级脉冲持续时间及高时空相干性,是获取高峰值功率密度极紫外(Extreme Ultraviolet, XUV)至软X射线波段辐射的可靠途径。本文以综述形式,系统总结了本研究团队近年来在提升SHHG光源亮度、传输品质及检测技术方面的研究进展。我们通过自主建设高重复频率气体及表面高次谐波综合实验平台,系统开展了覆盖千赫兹重频与拍瓦级峰值功率等不同激光尺度的SHHG产生实验。通过引入波形整形与预脉冲控制技术,展现了不同能量尺度下谐波转换效率与截止频率的调控途径与优化潜力。此外,本研究重点发展了基于高数值孔径哈特曼波前传感器(Hartmann Wavefront Sensor, HWS)的XUV波前诊断技术,提出了针对相对论等离子体阿秒脉冲的时域完整表征方案——光谱相位干涉直接电场重建法(Spectral Phase Interferometry for Direct Electric Field Reconstruction,SPIDER)及空间编码排列方案(Spatially Encoded Arrangement for SPIDER, SEA-SPIDER),并结合近场-远场传播算法,为SHHG光源时空特性的精确量化与调控提供了完整技术途径。研究结果验证了驱动激光参数(如脉宽、对比度、CEP)对谐波辐射机理及输出品质的影响,为构建高稳定性、可控的实验室台式阿秒相干光源及其在精密计量、材料动力学研究中的应用提供了坚实的技术与物理基础。

     

    Abstract: Ultra-intense and ultra-short laser technology provides a unique platform for studying strong-field physics, ultrafast dynamics, and new states of matter in the extreme nonlinear regime. Surface High Harmonic Generation (SHHG) driven by intense laser-plasma interactions offers a reliable route to obtain high-peak-power-density extreme ultraviolet (XUV) to soft X-ray radiation, characterized by high single-pulse energy, attosecond pulse duration, and excellent spatio-temporal coherence. This paper summarizes recent research progress by our team in enhancing the brightness, transmission quality, and diagnostic techniques of SHHG sources. We have constructed a comprehensive experimental platform for high-repetition-rate gas and surface high harmonic generation, systematically conducting SHHG experiments on platforms ranging from kilohertz-repetition-rate to petawatt-peak-power laser systems. By implementing waveform shaping and pre-pulse control techniques, we have verified the tuning pathways and optimization potential of harmonic conversion efficiency and cut-off frequencies across different energy scales. Furthermore, we have developed advanced XUV wavefront diagnostic techniques based on high-numerical-aperture Hartmann Wavefront Sensors (HWS), combined with full temporal characterization schemes , the Spectral Phase Interferometry for Direct Electric Field Reconstruction (SPIDER) and Spatially Encoded Arrangement for SPIDER(SEA-SPIDER), in conjunction with near-to-far-field propagation algorithms, enabling precise quantification and control of the spatio-temporal properties of SHHG sources. Our results verify the influence of driving laser parameters—such as pulse duration, contrast, and carrier-envelope phase (CEP)—on the harmonic emission mechanism and output quality. These findings establish a solid technical and physical foundation for developing highly stable, controllable, tabletop attosecond coherent sources and their applications in precision metrology and material dynamics research.

     

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