He^＋离子在啁啾激光和高频脉冲组合场中产生的单个阿秒脉冲

Isolated pulse generation of He^+ ion in an intense chirped laser and its high frequency pulse

利用数值求解含时薛定谔方程的方法,从理论上研究了一维模型He+离子在波长为1064nm的线性啁啾激光和高频脉冲形成的组合场中产生的高次谐波以及由这种高次谐波构造的阿秒脉冲特征.发现在组合场中,由于啁啾脉冲的作用和在适当的时刻加入了高频脉冲,不仅使高次谐波谱的平台区域能得到很大的扩展,而且谐波转化效率也得到有效地提高,当对第二平台区域的不同范围内高次谐波迭加都可得到单个阿秒脉冲,最短可达21阿秒.最后通过经典分析和时频分析解释了这种高次谐波展宽与阿秒脉冲发射过程的特点.

By solving the time-dependent Schrdinger equation numerically,theoretically we study the high-order harmonics of a model He＋ion exposed to the combined field of an intense chirped laser pulse and its high frequency pulse,and analyze the characteristics of the attosecond pulse produced by the high-order harmonics（HHG）.Due to the presence of the chirped pulse and the high frequency pulse in the case of the combined fields,it is shown that the plateau of the high-order harmonics is extended largely and the conversion efficiency of high-order harmonics is enhanced effectively.By superimposing some orders harmonics in different region of the second plateau,all of the pulses obtained are single attosecond ones,minimum pulse achieves 21 as.To better understand the physical reasons of HHG enhancement and attosecond pulse emission,we perform classical analysis and the time-frequency analysis.