We propose a simple and efficient method to optimize two-color chirped laser pulses by forming a “temporal gate” for the generation of isolated attosecond pulses (IAPs) in soft X rays. We show that the generation process for higher and cutoff harmonics can be effectively limited within the temporal gate, and the harmonic emission interval can be further reduced with the help of phase-matching by only selecting the contribution from short-trajectory electrons. This two-color gating mechanism is verified by increasing the pulse duration, raising the gas pressure, and extending the target cutoff. Compared to the five-color waveform in Phys. Rev. Lett.102, 063003 (2009)PRLTAO0031-900710.1103/PhysRevLett.102.063003, our waveform can be used to generate the IAP in the long-duration laser pulse while the cutoff energy is higher without the reduction of harmonic yields. Our work provides an alternative temporal gating scheme for the generation of IAPs by simultaneously improving the harmonic conversion efficiency, thus making the attosecond soft X rays an intense and highly time-resolved tabletop light source for future applications.

中文翻译：

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双色啁啾激光器时间门优化用于在软X射线中产生孤立阿秒脉冲

我们提出了一种简单有效的方法，通过形成一个“时间门”来在软 X 射线中产生孤立的阿秒脉冲 (IAP)，从而优化双色啁啾激光脉冲。我们表明，高次谐波和截止谐波的产生过程可以有效地限制在时间门内，并且可以在相位匹配的帮助下通过仅选择短轨迹电子的贡献来进一步减少谐波发射间隔。通过增加脉冲持续时间、提高气体压力和延长目标截止时间来验证这种双色门控机制。与 Phys 中的五色波形相比。Rev. Lett.102, 063003 (2009)PRLTAO0031-900710.1103/PhysRevLett.102.063003, 我们的波形可用于在长持续时间激光脉冲中产生 IAP，同时截止能量更高，而不会降低谐波产量。我们的工作通过同时提高谐波转换效率为 IAP 的生成提供了一种替代的时间门控方案，从而使阿秒软 X 射线成为未来应用的强烈且高度时间分辨的桌面光源。