强太赫兹辐射场下超快电子动力学的研究

With the development of technology in generating intense terahertz fields, it becomes possible to use terahertz fields to manipulate the quantum states in atoms and molecules. The processes of terahertz emission, high-harmonic generation and above-threshold ionization are all attributed to the dynamics of the electronic wavepackets in strong laser fields and these phenomena can be interpreted in a unified physical picture. The two-color femtosecond laser pulses are used to generate the intense terahertz fields with single-cycle, stabilized carrier-envelope phase and controlled polarization. This proposal will perform systematic investigations and analysis of the influences of the intensity, polarization and even chirp of the terahertz fields on the terahertz-dressed above-threshold ionization photoelectron spectra. The purpose of this project is to research into the dynamical process and further to manipulate the quantum electric states with terahertz fields. This project will simultaneously study the high-order harmonic under the influence of the terahertz fields. One purpose is to investigate the relationship among terahertz emission, high-harmonic generation and photoelectron spectrum. The other purpose is to experimentally explore the effects and mechanisms of the intense terahertz fields on enhancing both cutoff frequency and efficiency of high-harmonic generation.

随着高功率太赫兹源技术的发展，人们利用太赫兹操控原子分子的量子态成为可能。太赫兹辐射、高次谐波、阈上电离都取决于强场下的电子波包动力学行为，可用统一的物理图像解释。本项目提出利用双色场飞秒脉冲电离气体产生的单周期，载波包络相位稳定，偏振态可控的强太赫兹场，系统地研究太赫兹的强度、偏振、甚至啁啾等参数对太赫兹调制下的阈上电离光电子谱的影响，以此来研究强场下的动力学行为，进而实现电子波包量子态的太赫兹操控。本项目同时观测太赫兹场对高次谐波的影响，研究太赫兹辐射、高次谐波、光电子谱之间的关联特性，并在实验上探索强太赫兹在提高高次谐波的截止频率与辐射效率方面的作用及其机理。

太赫兹辐射、高次谐波、阈上电离都取决于强场下的电子波包动力学行为，可用统一的物理图像解释。本项目的主要研究目标是太赫兹源的强度、偏振、甚至啁啾等参数对阈上电离电子谱的影响。为此，我们采用了基于铌酸锂的倾斜波前技术产生强太赫兹，其电场强度可以达到0.5MV/cm。我们搭建了具有多用途的的速度成像谱仪，该谱仪具有同时探测太赫兹（高次谐波）和电子动量谱的功能。最后，我们利用冷靶动量反冲谱仪研究了三价二氧化碳二聚体在飞秒激光下的解离过程并解析了其几何结构。