Nonlinear absorption mechanism in ablation of transparent materials by high power and ultrashort laser pulses

The processes of nonlinear absorption are considered in transparent materials like nitride semiconductor, sapphire and other dielectrics under ultrashort (femtosecond (fs)-range) laser pulses irradiation. The ablation threshold is in the multi-TW/cm2 range. The power consumption under the ablation process is described in terms of tunneling absorption. The ablation threshold increases as about the third power of the energy bandgap of the material, in close agreement with the experimental data