传播效应对宽带极紫外连续谱的影响

Propagation Effect on the Broad-bandwidth XUV Continuum Spectra

宽带极紫外连续谱是获得阿秒脉冲的重要途径,在此过程中传播效应是影响宽带极紫外连续谱产生的重要因素,本文针对传播效应对宽带极紫外连续谱的影响,采用慢变波近似的一阶传播方程,研究了传播过程对双色场周期量级激光脉冲产生宽带连续谱及其对应的单个阿秒脉冲的影响.通过分析不同聚焦位置和介质长度的传播过程,发现介质位于焦点之后有利于产生连续谱,同时随着介质长度的变长,虽然单个阿秒脉冲峰值强度有所提高,但是产生的阿秒脉冲宽度也会增加.进一步的分析表明,在特定的双色场延迟优化下,传播效应不仅使得阿秒脉冲强度增强,还可以获得与单原子模型下具有同样脉宽的单个阿秒脉冲,而不会因为传播效应导致阿秒脉冲宽度变宽.

Producing the broad XUV spectra is an important way to generate the isolated attosecond pulse,in which the propagation effect is an important factor.With the first order propagation equation of the slowly-evolving-wave approximation,the propagation effect on the broad XUV continuum spectra and the isolated attosecond pulse generated by two-color few-cycle laser pulse were investigated.By simulating the generation of the broad XUV spectra under different focal positions and different medium lengths,it was found that it is benefit for the generation of the continuum spectra when the medium is after the focal point.But,with the longer medium,the pulse duration of the isolated attosecond pulse will be longer,although its intensity becomes higher.With further analysis,it was found that if the delay between two-color pulses can be optimized,a strong isolated attosecond pulse with the same pulse duration as that of the single-active electron model can still be obtained.