Femtosecond laser high-efficiency drilling of high-aspect-ratio microholes based on free-electron-density adjustments

Lan Jiang, Juqiang Fang, Qiang Cao, Kaihu Zhang, Peng Wang, Yanwu Yu, Qiang Huang, Yongfeng Lu

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


We studied the micromachining of high-aspect-ratio holes in poly(methylmethacrylate) using a visible double-pulse femtosecond laser based on free-electron-density adjustments. Hole depth and aspect ratio increased simultaneously upon decreasing the wavelength in the visible-light zone. When the pulse energy reached a high level, the free-electron density was adjusted by using a double-pulse laser, which induced fewer free electrons, a lower reflectivity plasma plume, and more pulse energy deposition in the solid bottom. Thus, the aspect ratio of the hole was improved considerably. At a moderate pulse energy level, a 1.3-1.4 times enhancement of both the ablation depth and the aspect ratio was observed when the double-pulse delay was set between 100 and 300 fs, probably due to an enhanced photon-electron coupling effect through adjusting the free-electron density. At a lower pulse energy level, this effect also induced the generation of a submicrometer string. In addition, the ablation rate was improved significantly by using visible double pulses.

Original languageEnglish (US)
Pages (from-to)7290-7295
Number of pages6
JournalApplied optics
Issue number31
StatePublished - Nov 1 2014

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering


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