Abstract

We investigate the pulse duration dependence of harmonic yield in isotopic molecules of H₂⁺ and T₂⁺ driven by different laser intensities. Generally, the harmonic yield can be improved as pulse duration increases and then a maximum value can be obtained at the specific duration. Particularly, (i) driven by low laser intensity, the optimal pulse duration for H₂⁺ is 20 cycles, and the harmonic intensity of H₂⁺ is much higher than that of T₂⁺. (ii) Driven by middle laser intensity, the optimal pulse durations for H₂⁺ and T₂⁺ are 15 cycles and 22 cycles, respectively. Moreover, the harmonic intensities of H₂⁺ and T₂⁺ from optimal pulse durations are almost the same. (iii) Driven by high laser intensity, the optimal pulse duration for T₂⁺ is 15 cycles. For H₂⁺, the enhancement of harmonic yield is very slow as pulse duration increases. Furthermore, the similar harmonic yields of H₂⁺ and T₂⁺ can be found before 12 cycles; while, when the pulse duration is larger than 12 cycles, the harmonic yield of H₂⁺ is smaller than that of T₂⁺. Taking advantage of harmonic yield changing law and with assistance of controlling pulse, the intense and broad spectral plateau can be obtained, which can support the generation of isolated attosecond pulses with durations of sub-40 as.

Graphical abstract

中文翻译：

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H 2 +及其同位素分子的谐波产率的脉冲持续时间依赖性

摘要

我们研究了不同激光强度驱动的H ₂ ⁺和T ₂ ⁺同位素分子中谐波产量的脉冲持续时间依赖性。通常，随着脉冲持续时间的增加，谐波产量会提高，然后可以在特定的持续时间获得最大值。特别地，（i）由低激光强度驱动，H ₂ ⁺的最佳脉冲持续时间为20个周期，并且H ₂ ⁺的谐波强度远高于T ₂ ⁺的谐波强度。（ii）由中等激光强度驱动，H ₂ ⁺和T ₂ ⁺的最佳脉冲持续时间分别是15个循环和22个循环。而且，来自最佳脉冲持续时间的H ₂ ⁺和T ₂ ⁺的谐波强度几乎相同。（iii）在高激光强度的驱动下，T ₂ ⁺的最佳脉冲持续时间为15个周期。对于H ₂ ⁺，随着脉冲持续时间的增加，谐波产量的提高非常缓慢。此外，可以在12个循环之前发现H ₂ ⁺和T ₂ ⁺的相似谐波产量。而当脉冲持续时间大于12个周期时，H ₂ ⁺的谐波产量小于T ₂ ⁺的谐波产量。。利用谐波产量变化规律并在控制脉冲的帮助下，可以获得强烈而宽广的频谱平稳期，这可以支持产生持续时间低于40 as的孤立的阿秒脉冲。

图形概要