This paper reports the physical phenomenon of the temporal overlapping double femtosecond laser-induced ablation enhancement at different time delays. Detailed thermodynamic modeling demonstrates the ablation enhancement is highly dependent on the first pulse’s laser fluence. In the case of the first pulse laser fluence being higher than material’s ablation threshold, the ablation enhancement is attributed to optical absorption modification by the first pulse ablation. While the first pulse’s laser fluence is lower than the material’s ablation threshold, the first pulse-induced melting leads to much higher absorption of the second pulse. However, for the case of the first pulse’s laser fluence even lower than melting threshold, the ablation enhancement decreases obviously with time delay. The results of the temporal overlapping double femtosecond laser ablation of poly(e-caprolactone) are in good agreement with the theoretical predictions.

中文翻译：

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通过时间重叠双脉冲辐照增强飞秒激光诱导表面烧蚀

本文报道了不同时间延迟下时间重叠的双飞秒激光诱导烧蚀增强的物理现象。详细的热力学模型表明烧蚀增强高度依赖于第一个脉冲的激光能量密度。在第一脉冲激光能量密度高于材料烧蚀阈值的情况下，烧蚀增强归因于第一脉冲烧蚀的光吸收修正。虽然第一个脉冲的激光能量密度低于材料的烧蚀阈值，但第一个脉冲引起的熔化会导致第二个脉冲的吸收高得多。然而，对于第一脉冲的激光能量密度甚至低于熔化阈值的情况，烧蚀增强随着时间的延迟而明显下降。