Enhancing the expansion of a plasma shockwave by crater-induced laser refocusing in femtosecond laser ablation of fused silica

Qingsong Wang, Lan Jiang*, Jingya Sun, Changji Pan, Weina Han, Guoyan Wang, Hao Zhang, Costas P. Grigoropoulos, Yongfeng Lu

*此作品的通讯作者

科研成果: 期刊稿件文章同行评审

40 引用 (Scopus)

摘要

The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during the second pulse irradiation on the crater induced by the first pulse, the expansion of the plasma and shockwave is enhanced in the longitudinal direction. The plasma model and Fresnel diffraction theory are combined to calculate the laser intensity distribution by considering the change in surface morphology and transient material properties. The theoretical results show that after the free electron density induced by the rising edge of the pulse reaches the critical density, the originally transparent surface is transformed into a transient high-reflectivity surface (metallic state). Thus, the crater with a concave-lens-like morphology can tremendously reflect and refocus the latter part of the laser pulse, leading to a strong laser field with an intensity even higher than the incident intensity. This strong refocused laser pulse results in a stronger laser-induced air breakdown and enhances the subsequent expansion of the plasma and shockwave. In addition, similar shadowgraphs are also recorded in the single-pulse ablation of a concave microlens, providing experimental evidence for the enhancement mechanism.

源语言英语
页(从-至)488-493
页数6
期刊Photonics Research
5
5
DOI
出版状态已出版 - 1 10月 2017

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Wang, Q., Jiang, L., Sun, J., Pan, C., Han, W., Wang, G., Zhang, H., Grigoropoulos, C. P., & Lu, Y. (2017). Enhancing the expansion of a plasma shockwave by crater-induced laser refocusing in femtosecond laser ablation of fused silica. Photonics Research, 5(5), 488-493. https://doi.org/10.1364/PRJ.5.000488