极紫外阿秒脉冲测量的新原理与新技术研究

Since 2002, human has strided from "femtosecond chemistry" era which is focus on the atomic motion in molecules forward to "attosecond physics" era which is focus on the electron motion in atoms. Development to date, attosecond science has made significant progress in generating the attosecond coherent light source with a shorter pulse width, higher photon energy and higher brightness, which will be better used in ultrafast information, materials science and technology, biological science, and other fields. However, to date, the duration measurement of attosecond pulses is based on ionization and the XUV photons are transformed to electrons which is measured by the time-of-flight time. This method will be limited by the resolution of the electron energy and the photoelectric conversion efficiency, especially when the photon energy is greater than 150eV, the electron energy resolution of the measurement is low. Therefore, the development of new duration measurement principles and technology of extreme ultraviolet attosecond pulses is a cutting-edge scientific problem to be urgently solved in this area at present. This research project aims to explore the new principles and technology of attosecond pulse measurement, by using the transient absorption characteristics of medium in XUV light and using dual-target high-order harmonic generation, and so on, to break the current limitations of measurement techniques based on XUV photoionization, and access to universal methods of attosecond pulse measurement including the pulses in water window and even keV band.

从2002 年至今，人类已由研究分子中原子运动的“飞秒化学” 时代进入到研究原子内电子运动的“阿秒物理学”时代。阿秒科学发展至今，在产生更短脉冲宽度、更高光子能量、更高亮度的阿秒相干光源方面已经取得了重要进展，并将更好地应用于超快信息、材料科学技术和生命科学等领域。然而，到目前为止，阿秒脉冲宽度的测量基本是采用电离将XUV光子转换成电子并通过时间飞行谱测量电子能量来实现。这种方法会受电子能量的分辨率和光电转换的效率的限制，尤其当光子能量大于150eV时，电子能量测量的分辨率很低。因此，发展极紫外阿秒脉冲宽度测量的新原理和新技术是目前该领域亟待解决的难题和前沿科学问题。本项目旨在探索研究阿秒脉冲宽度测量的新原理与新方法，通过利用介质对XUV光的瞬态吸收特性及双靶高次谐波产生等方案，突破目前基于XUV光电离的测量技术的局限性，获得包括水窗波段乃至keV波段在内的阿秒脉冲测量的普适方法。

从2002 年至今，人类已由研究分子中原子运动的“飞秒化学” 时代进入到研究原子内电子运动的“阿秒物理学”时代。阿秒科学发展至今，在产生更短脉冲宽度、更高光子能量、更高亮度的阿秒相干光源方面已经取得了重要进展，并将更好地应用于超快信息、材料科学技术和生命科学等领域。然而，到目前为止，阿秒脉冲宽度的测量基本是采用电离将极紫外(XUV)光子转换成电子并通过时间飞行谱测量电子能量来实现。这种方法会受电子能量的分辨率和光电转换的效率的限制，尤其当光子能量大于150eV时，电子能量测量的分辨率很低。因此，发展极紫外阿秒脉冲宽度测量的新原理和新技术是目前该领域亟待解决的难题和前沿科学问题。本项目先分别研究了高光子能量波段、高亮度及固体介质中的高次谐波产生特性，为高光子能量波段的阿秒脉宽测量、提高瞬态吸收光谱的信噪比及固体介质中的瞬态吸收特性研究等奠定了基础，在此基础上研究了气体和固体介质在扫描红外驱动激光和XUV脉冲相对延迟时的阿秒瞬态吸收光谱，提出了阿秒脉冲的啁啾效应和XUV啁啾的频谱调制特性可以为XUV谱相位的重建提供一种全光方法。