Femtosecond laser ablation from dielectric materials: Comparison to arc discharge erosion

After explosive ablation from sapphire crystals by linearly polarised laser pulses, regular structures are observed on the bottom of the ablation pit. These structures do not comply with conventional ripple patterns. Instead, they more nearly resemble wickerwork, aligned perpendicular to the laser beam polarisation. A similar morphology is obtained by arc discharge erosion at AgCdO electrodes, suggesting that an explosive laser ablation may be characterised by high electric field effects and self organisation in the ablation craters.