不对称外场驱动下高次谐波宏观效应研究

The macroscopic effects of high-order harmonic generation of monoatomioc gas driven by asymmetry electric fields will be investigated in this project, which include the intensity, coherence and spatial distribution of high-order harmonic spectrum variation with the focus property of the incident light beam, gas density and propagation distance. In our previous works on the high-order harmonic generation of atoms drvien by strong laser fields, we proposed a novel physical mechanism that the asymmetry of the driver field leads to the extension of the high-order harmonic spectrum cutoff. Based on this mechanism, we will explore the mechanism of ultra-broad coherent continuum spectrum generation and the scheme for the generation of sub-50 attoseond pulse driven by multi-cycle laser pulses, considering the propagation effect which can select the electron trajectory.

本项目主要进行原子气体在不对称外场驱动下高次谐波宏观效应的研究，考察高次谐波谱的强度、相干特性以及空间分布对入射光束的聚焦特性、气体密度以及传播距离的依赖关系。基于我们在强场激光与原子相互作用产生高次谐波的过程中提出的驱动场的不对称性导致高次谐波截止频率提高这一物理机制，结合传播效应能对电子运动轨道进行选择的特点，研究在多周期激光脉冲驱动下产生超宽相干连续谱的物理机制以及获取亚50阿秒脉冲的理论方案。

气体介质在强场激光的作用下，会产生一些高度非线性的光学现象，如高次谐波的产生和阈上电离过程。它们在极紫外及X射线波段激光脉冲的产生、超快过程的探测与控制、物质结构探测等方面有着广泛的应用。本项目围绕原子或分子气体在不对称外场驱动下的高次谐波宏观效应及阈上电离过程展开研究，提出了利用多色光束驱动在多周期条件下实现亚50as脉冲的可行性理论方案，并进一步讨论了高次谐波在少周期激光脉冲的载波包络相位的测量方面的应用，研究了不对称外场驱动下的阈上电离过程，并探讨了阈上电离谱在超快过程的探测中的应用。