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<p>The surface modification of molybdenum under picosecond laser irradiation was systematically investigated, with particular emphasis on establishing a&#xa0;quantitative link between plasma parameters and ablation crater morphology. A&#xa0;picosecond Nd:YAG laser operating at a&#xa0;wavelength of 1064 nm with a&#xa0;pulse duration of 28 ps was used to irradiate molybdenum samples at laser fluences of 34.06, 36.59, and 38.02 J/cm<sup>2</sup>. Ablation efficiency was evaluated by measuring crater diameters via surface profilometry, and the resulting surface morphology was examined by scanning electron microscopy (SEM). Laser-induced breakdown spectroscopy (LIBS) was employed to determine the fundamental plasma parameters. The electron temperature was found to vary within the range of 12,263–12,781 K, whereas the electron density decreased from <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(0.55 \times 10^{18}\)</EquationSource> </InlineEquation> cm<sup>−3</sup> to <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(0.40 \times 10^{18}\)</EquationSource> </InlineEquation> cm<sup>−3</sup> with increasing laser fluence. A&#xa0;strong negative correlation (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(r \approx -0.99\)</EquationSource> </InlineEquation>) between electron density and ablation crater diameter was identified, indicating that plasma shielding is the dominant factor limiting material removal at higher fluences. The key novelty of this work lies in the experimental demonstration of a&#xa0;self-regulating plasma regime during picosecond laser ablation of molybdenum, in which inverse bremsstrahlung absorption and plasma expansion provide a&#xa0;feedback mechanism that stabilizes both plasma parameters and crater dimensions. This quantitative correlation among electron density, plasma absorption, and crater formation has not been reported previously for molybdenum under picosecond irradiation. The results obtained advance fundamental understanding of laser-plasma-matter interactions and provide practical guidelines for high-precision laser micromachining of refractory, high-melting-point metals.</p>

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Self-regulated crater formation governed by electron density in picosecond Nd:YAG laser-induced molybdenum plasma

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Munisbek Akhmedov,
  • Jurabek Sadullayev,
  • Murodbek Vapayev,
  • Anvar Matnazarov,
  • Ikram Davletov,
  • Javlon Rayimbaev

摘要

The surface modification of molybdenum under picosecond laser irradiation was systematically investigated, with particular emphasis on establishing a quantitative link between plasma parameters and ablation crater morphology. A picosecond Nd:YAG laser operating at a wavelength of 1064 nm with a pulse duration of 28 ps was used to irradiate molybdenum samples at laser fluences of 34.06, 36.59, and 38.02 J/cm2. Ablation efficiency was evaluated by measuring crater diameters via surface profilometry, and the resulting surface morphology was examined by scanning electron microscopy (SEM). Laser-induced breakdown spectroscopy (LIBS) was employed to determine the fundamental plasma parameters. The electron temperature was found to vary within the range of 12,263–12,781 K, whereas the electron density decreased from \(0.55 \times 10^{18}\) cm−3 to \(0.40 \times 10^{18}\) cm−3 with increasing laser fluence. A strong negative correlation ( \(r \approx -0.99\) ) between electron density and ablation crater diameter was identified, indicating that plasma shielding is the dominant factor limiting material removal at higher fluences. The key novelty of this work lies in the experimental demonstration of a self-regulating plasma regime during picosecond laser ablation of molybdenum, in which inverse bremsstrahlung absorption and plasma expansion provide a feedback mechanism that stabilizes both plasma parameters and crater dimensions. This quantitative correlation among electron density, plasma absorption, and crater formation has not been reported previously for molybdenum under picosecond irradiation. The results obtained advance fundamental understanding of laser-plasma-matter interactions and provide practical guidelines for high-precision laser micromachining of refractory, high-melting-point metals.