增益窄化效应限制了啁啾脉冲放大系统输出的最短脉冲宽度,需要对注入放大系统的种子啁啾脉冲进行光谱整形,以保证放大后的啁啾脉冲光具有足够的带宽并满足特定的光谱分布。理论上假定放大后啁啾脉冲的光谱分布为高斯分布或超高斯分布,对“百焦耳级钕玻璃啁啾脉冲放大系统”进行逆运算。研究发现,所需种子啁啾光的能量、带宽以及压缩后脉冲的信噪比都与该分布密切相关。通过光谱整形,使放大后的啁啾脉冲光的光谱分布为二阶超高斯分布,能够获得小于400 fs高信噪比的超短脉冲输出,此时所需种子啁啾脉冲能量仅为33 μJ,带宽14 nm,在装置前级注入能力的范围之内。为百焦耳装置光谱整形实验的开展提供了理论指导。

In order to obtain a shorter pulse in a chirped pulse amplification system, the spectrum of the seed pulse is shaped to compensate the effect of gain narrowing, to make sure the amplified pulse has enough spectral width and given distribution. Supposing the spectral distribution of the chirped pulse after amplification is be Gauss or super-Gauss distribution, the inverse calculation on 100 J Nd∶glass chirped pulse amplication system is carried out. It is found that the energy, bandwidth of the seed pulse and the signal-to-noise ratio of the compressed pulse are strongly related to the distribution of the amplified pulse spectrum. After spectral shaping, the amplified pulse spectrum is second-order super-Gauss distribution, and 400 fs pulses are obtained with high signal-to-noise ratio, 33 μJ seed pulse energy and 14 nm bandwidth. The results provide a theoretical base for the spectral shaping experiment of 100 J system.