Ultra-fast writing of self-organized bubble networks using femtosecond laser exposure in the cumulative regime

By continuously scanning a laser beam across a fused silica specimen in the cumulative regime, here we demonstrate the formation of self-organized bubbles buried in the material. Rather than using high intensity pulses and high numerical aperture to induce explosions in the material, we use moderate numerical apertures (NA <; 0.4) and low-energy pulses emitted at 9.4MHz. In that regime, the formation of bubbles is driven by thermal effects rather than from micro-explosions as observed with high-focused intensities and high NA. Interestingly, a transition between chaotic and self-organized patterns is observed at high scanning rate. In addition, we demonstrate its applicability for two- and three-dimensional gratings patterns written at very high speed.