Fig. 1. Sketch of the experimental setup. Inset: the laser field on the object plane with and without the concave lens, respectively.

Fig. 2. (a) AFM micrographs of the ablated spot after irradiation by a single laser pulse at a fluence of 0.90  J/cm2. The illustration shows the magnified details of the marked region. The black arrow shows the polarization E of the incident laser. (b) The height trace along the arrow perpendicular to the laser polarization, and (c) parallel to the laser polarization.

Fig. 3. AFM micrograph of the ablated spot after irradiation by a single laser pulse with (a) horizontal polarization and (b) vertical polarization.

Fig. 4. AFM micrograph of the ablation spot after irradiation by a single laser pulse at a fluence of (a) 1.67 and (b) 0.76  J/cm2. (c) The height traces along the arrows shown in (a) and (b).

Fig. 5. AFM micrograph of the ablated spot after irradiation by a single laser pulse at a fluence of 0.63  J/cm2.