Few-cycle sources with high average powers are required for applications to attosecond science. Raman-enhanced spectral broadening of Yb-doped laser amplifiers in molecular gases can yield few-cycle pulses, but thermal excitation of vibrational and rotational degrees of freedom may preclude high-power operation. Here we investigate changes in the spectral broadening associated with repetitive laser interactions in an ${{\rm{N}}_2}{\rm{O}}$-filled hollow-core fiber. By comparing experimental measurements of the spectrum associated with each laser pulse to simulations based on a density matrix model, we find that losses in a spectral bandwidth and transmission are largely dominated by thermal excitation of the gas.

中文翻译：

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分子气体填充中空纤维的热效应

应用到秒科学需要很少的具有高平均功率的循环源。掺有Yb的激光放大器在分子气体中的拉曼增强光谱加宽可以产生很少的周期脉冲，但是振动和旋转自由度的热激发可能会阻止大功率工作。在这里，我们研究了填充空心$ {{{\ rm {N}} _ 2} {\ rm {O}} $的空心光纤中与重复激光相互作用相关的光谱展宽变化。通过将与每个激光脉冲相关的光谱的实验测量结果与基于密度矩阵模型的模拟结果进行比较，我们发现光谱带宽和透射率的损失在很大程度上受气体的热激发支配。