Role of laser-induced plasma in ultradeep drilling of materials by nanosecond laser pulses

Radiative effects of the laser-induced ablative plasma on the heating and ablation dynamics of materials irradiated by nanosecond laser pulses are studied by the example of graphite ablation. On the basis of combined thermal and gas dynamic modeling, the laser-induced plasma plume is shown to be a controlling factor responsible for ultradeep laser drilling due to plasma radiation, both bremsstrahlung and recombinative. We demonstrate that plasma radiative heating of the target considerably deepens the molten layer, thus explaining the observed crater depths.

► We show that laser-induced plasma plume is responsible for ultradeep laser drilling. ► Much of the laser energy absorbed by plasma can be reradiated back toward the target. ► A model of thermal laser ablation under plasma reradiation conditions is developed. ► Plasma radiative heating considerably deepens the molten layer on the target. ► The proposed mechanism of ultradeep drilling is verified by experiments and modeling.