Femtosecond laser double pulse Bessel beam ablation of silicon.

Here, a double pulse Bessel beam was acquired by modulating a femtosecond laser Gaussian beam from both spatial and temporal scales. The double pulse Bessel beam ablation of silicon was studied systematically. The experimental results showed that when the time delay was 0.5 ps, the ablation efficiency slightly increased. As the time delay increased from 0.5 to 100 ps, the ablation rate was significantly suppressed, which could be attributed to the fact that the time delay was longer than the time for free electron density reaching its maximum value approximately 150 fs. Moreover, the morphology of the ablation spot indicated that the time delay had a significant effect on the changes in morphology. More importantly, a different time delay affected the percentage of oxygen on the processed spot. Finally, using the double pulse Bessel beam ablation of silicon, controllable antireflection and superhydrophobic functional surfaces could be easily obtained.