High-quality micropore drilling by using orthogonally polarized femtosecond double-pulse bursts

The present study proposes a facile method for fabricating high-quality, high-precision, and small-taper micropores. An YVO4 crystal is used to split a single pulse into two sub-pulses with perpendicular polarization, and the pulse delay is adjusted by controlling the crystal's thickness. The femtosecond double-pulse bursts can enhance the ablation, and the maximum ablation efficiency is achieved when the pulse delay is 4 ps. The two-temperature model revealed that the ablation can be enhanced by enhancing electron-phonon coupling and decreasing the electron thermal conductivity when changing the pulse delay. The orthogonally polarized femtosecond doublepulse bursts eliminate the polarization removal caused by the reflectivity difference between p- and s-polarized light, improving the uniformity of the micropore sidewall and the consistency of the inlet and outlet. The mechanism underlying defect formation and the relationship between the processing parameters and heat accumulation were systematically investigated. Elemental composition and phase analyses indicated that femtosecond double-pulse bursts had negligible adverse effects on samples. The proposed facile method can be used to drill high-quality micropores in various industrial applications.