Figure 3.

SEM and 3D-projections of SEM pictures of surface structures obtained after irradiation of the Tight Columns and the Coarse Columns samples with an average fluence of 0.12 J/cm² and different numbers of pulses. The evolution of structures is shown for different numbers of pulses. For the TC sample, successively appear disorganized filaments induced by spallation (N = 1), orientated filaments (N = 2), high spatial frequency laser-induced periodic surface structures (HSFL) parallel to the polarization intertwined between low spatial frequency laser-induced periodic surface structures (LSFL) perpendicular to the polarization (N = 5 and N =15). For the CC sample, successively appear residual cavitation bubbles (N = 2), LSFL (N = 3), horizontal HSFL and vertical LSFL (N = 4 and N = 15). The red arrow represents the electric field polarization. The symbols (||) and (ꓕ) respectively mean “parallel” and “perpendicular” to the polarization. 2D-Fourier transforms shown as insets support the presence of a crossed structure of HSFL and LSFL for the highest pulse numbers.