固体中强场超快电离动力学的研究

Ionization processes in solids unfold on sub-femtosecond or attosecond timescale, which provides an opportunity to investigate the attosecond dynamics in solids. Despite this, the recent major advances in attosecond science are based on atoms and molecules in gas phase. The metrology applied in attosecond science in gases are based on detecting electrons, ions and high harmonic, which can not be used inside solids, so new metrology is required. In this study, we utilize a pump-probe and spectral interference scheme to study the ultrafast ionization dynamics, for the property of laser beam propagating through the solids has been modified, such as refractivity and absorption. We measure the phase variation of the supercontinuum, which is generated during few-cycle laser pulses with stabilized carrier-envelope phase filament in solid. Thus the sub-cycle ionization dynamics can be obtained. The scheme is generalized to crystal and surface of dielectric to study the effect of crystal structure on ionization and the metallization of dielectric, respectively. This study can give new insights into the ionization processes in solids and investigate the ionization dynamics in solids in a much shorter time scale.

固态介质中的强场电离过程发生在亚飞秒或者阿秒尺度内，它开启了固体中的阿秒动力学过程的研究。然而，最近阿秒科学的进展都集中在气态原子分子中。气态原子分子中的阿秒科学是基于探测电子、离子和高次谐波，这些探测手段在固体中不再适用，需要探寻新的测量手段。在本项目中，我们提出用谱干涉和泵浦探测方案研究固体中的超快电离动力学过程。由于固体中电离过程影响在其中传播的光束的性质，如折射率，吸收等，通过测量载波包络相位稳定的周期量级激光脉冲在固体中成丝过程产生的超连续谱的相位变化，可以提取亚光学周期的电离动力学信息。将该研究推广到晶体中和电介质的表面，分别研究晶体的结构对电离过程的影响和电介质中的金属化过程。通过本项目的研究可以更深入地理解固体中的电离过程，在更短的时间尺度内研究固体内部的动力学过程。

本项目围绕固体中强激光场电离动力学展开研究。首先，搭建了基于谱干涉的泵浦-探测实验装置，并将该装置拓展到研究飞秒激光脉冲在固体中成丝。我们利用该光谱学的方法研究了飞秒强激光脉冲在熔石英中成丝，证实了飞秒脉冲在固体中成丝的过程是激光脉冲自发的演化成非线性X波的过程，固体中强激光场电离在此过程中不起决定性的作用。同时，在惰性气体中展开了强激光场电离的研究，发现Keldysh参数在1附近时，强椭圆激光场电离原子中存在绝热效应，这有助于理解固体强激光场电离动力学。