Fig. 1. Schematic of one-dimensional silicon irradiated by femtosecond laser pulse

Fig. 2. Variation of electron density on silicon surface under femtosecond pulse irradiation

Fig. 3. Temperature evolution of electron and lattice systems

Fig. 4. Evolution of thermal conductivity of system

Fig. 5. Comparison of multiple scanning process of Gaussian spot and single scanning process of flat top spot. (a) Multiple scanning process of Gaussian spot; (b) single scanning process of flat top spot

Fig. 6. Comparison of flat-top Gaussian distribution functions with different orders

Fig. 7. Ablative crater shapes under different laser pulse numbers. (a) 1 pulse; (b) 5 pulses; (c) 10 pulses

Fig. 8. Ablation crater depth versus laser fluence

Fig. 9. Optical path diagram of flat-top laser grooving experiment

Fig. 10. Spot overlap rate and spot interval during flat top spot scanning

Fig. 11. Groove surface and bottom images at same location

Fig. 12. 2D groove shape test result