近日，浙江师范大学的钱义先及其研究小组与华中科技大学的张庆斌合作并取得一项新进展。经过不懈努力，他们揭示啁啾圆偏振阿秒脉冲多光子电离中对光电子涡旋的啁啾效应。相关研究成果已于2025年1月14日在国际知名学术期刊《物理评论A》上发表。

该研究团队从理论上研究了线性啁啾、具有时延的圆偏振脉冲对氙原子的多光子电离过程。通过求解二维含时薛定谔方程获得数值结果，并利用微扰理论进行分析。研究人员比较不同啁啾率激光脉冲的电离概率、能量、动量和角分布等可观测量，并发现电离过程对脉冲啁啾有明显的依赖性。具体而言，在同向旋转脉冲中，他们研究了光电子能量分布中相邻干涉条纹的能量间隔对啁啾率的依赖性。在反向旋转脉冲中，对光电子角分布的分析揭示，由于啁啾引起的相位差，光电子出射角对啁啾率敏感。

此外，根据不同多光子电离过程中光电子动量分布中的多起点螺旋结构，确定了临界啁啾率，并将其应用于控制光电子涡旋。这里讨论的发射电子可观测量对啁啾的依赖性，可能为表征啁啾激光脉冲提供一种理想的诊断工具。

附：英文原文

Title: Chirp effects on photoelectron vortices in multiphoton ionization by chirped circularly polarized attosecond pulses

Author:Run Wang^1,2,*, Qingbin Zhang³, and Yixian Qian^1,2

Issue&Volume: 2025-01-14

Abstract: We theoretically investigate the multiphoton ionization of the xenon atom by pairs of linearly chirped, time-delayed circularly polarized pulses. The numerical results are obtained by solving the two-dimensional time-dependent Schrdinger equation and analyzed by using perturbation theory. By comparing observables such as the ionization probabilities and the energy, momentum, and angular distributions for laser pulses with different chirp rates, we find that the ionization processes have a clear dependence on the pulse chirp. Specifically, the dependence of the energy separation between adjacent interference fringes in the photoelectron energy distributions on the chirp rate is studied in corotating pulses. In counter-rotating pulses, the analysis of the photoelectron angular distributions reveals that the photoelectron ejection angle is sensitive to the chirp rate due to chirp-induced phase difference. Moreover, the critical chirp rates for different multiphoton ionization processes are determined from the multistart spiral structures in photoelectron momentum distributions and applied for control of the photoelectron vortices. The chirp dependence of the emitted electron observables discussed here may provide an ideal diagnostic tool for characterizing the chirped laser pulses.

DOI: 10.1103/PhysRevA.111.013106

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.111.013106