基于高能光电子非对称性的少周期激光载波包络相位确定

Carrier Envelope Phase Determination for Few-Cycle Laser Pulses Based on Asymmetry of Ionized High-Energy Electrons

提出了一种利用高能光电子的非对称角分布来确定少周期激光载波包络相位(CEP)的方法。通过二级强场近似方法研究了隧穿电离区域氦原子在少周期激光驱动下阈上电离高能光电子角分布对载波相位的依赖关系,选择合适能量范围的光电子分布,能够给出非对称参数随激光CEP的变化。研究结果表明,通过这种高能光电子得到的非对称参数和由数值求解含时薛定谔方程(TDSE)得到的非对称参数随CEP的变化趋势符合得很好。由数值求解TDSE获得的非对称参数包含了低能光电子的贡献,而二级强场近似的方法仅通过高能光电子得到,从而该方法为实验测定激光的载波包络相位提供了方便。

A method is proposed to determine the carrier envelope phase （CEP） for few-cycle laser pulses based on the asymmetry of the angular distributions of high- energy photoelectrons. The dependence of angular distributions of high-energy photoelectron for high-order above threshold ionization of helium in few-cycle laser pulses in the tunneling regime is investigated by using the second-order strong field approximation. By choosing the energy range in the photoelectron distributions appropriately, the dependence of the asymmetry parameter on the CEP can be obtained. Experimental results show that the change of the asymmetry parameter with the CEP obtained in the present work has the same trend with that from solving the time-dependent Schrodinger equation （TDSE）. While in the TDSE calculations the contributions from the low energy photoelectrons are included, the asymmetry parameters obtained in the present work only account for the high-energy photoelectrons. Therefore, the proposed method provides a more convenient way for experimental determination of laser carrier phase.