Fig. 1. Schematic of experimental setup

Fig. 2. Beam profiles and intensity distributions. (a) Beam profile of Gaussian laser; (b) intensity of Gaussian laser; (c) beam profile of flattop laser; (d) intensity of flattop laser

Fig. 3. Ablation crater morphology of copper sample after 1000 laser pulses. (a)-(b) Gaussian laser; (c)-(d) flattop laser

Fig. 4. Laser energy of 1000 laser pulse for Gaussian laser and flattop laser

Fig. 5. Change of Cu element spectra line intensity with pulse number at Gaussian laser and flattop laser. (a) Cu 324.84 nm; (b) Cu 327.53 nm; (c) Cu 515.29 nm; (d) Cu 521.83 nm

Fig. 6. Change of plasma temperature and electron density with pulse numbers for Cu plasma at Gaussian laser and flattop laser