Abstract
During green wavelength femtosecond laser ablation, d-band electrons are excited to become free and to participate in the absorption process. The increased electron temperature also induces the density of state shift and causes the gap between the d-band and the Fermi level to expand. The d-band electron transition effect during the laser ablation process causes nonlinear absorption, therefore, it should always be considered during simulations of laser-copper interaction.This study used a single femtosecond laser pulse with a wavelength of 515 nm and a pulse duration of 300 fs to ablate copper with fluence 0.7–63 J/cm2. The experimental results were compared with the theoretical results, where a modified Drude-critical point model was adopted to simulate the ablation depth. The modified model considered the electron transition effect and a two-temperature model that assumed both the linear and nonlinear absorption effect. Comparison of the experimental and simulated results revealed that the simulated ablation depth obtained using the nonlinear absorption model was consistent with the experimental results.
Highlights
In the past decades, there have been several experimental and theoretical studies on femtosecond laser irradiation on copper
The AFM data of a copper surface irradiated by a single-shot femtosecond green wavelength laser with laser fluences of 0.7, 7, and 63 J/cm2 are shown in the supplement material
The experimental and simulation results were reported for the single femtosecond green wavelength laser pulse ablation of copper with different fluences (0.7 – 63 J/cm2)
Summary
There have been several experimental and theoretical studies on femtosecond laser irradiation on copper. Among the investigations on copper, the IR wavelengths regime [2, 3, 5,6,7,8,9,10,11,12,13,14] was the main focus, and the green wavelength regime has been rarely discussed. Some recent investigations were conducted on drilling copper with a femtosecond laser at two wavelengths, 1030 nm and 515 nm [4, 15], neither the ablation depth nor the theoretical investigation was presented. The laser-copper interaction for green wavelengths should be further investigated
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