Defocusing effect and energy absorption of plasma in picosecond laser drilling

Plasma is commonly existing in pulsed laser drilling and it has an important impact on drilling results. The effects include plasma absorption and defocusing effect caused by plasma. This paper studied the influence of plasma on laser drilling by a combination method of numerical simulation and experiment. Based on the combination of computational fluid dynamics (CFD), fluid–solid coupling theory, double-temperature model, C ++ programming and OpenFOAM simulation, this paper established and added the defocusing effect and energy absorption of plasma as sub-modules. Finally, this paper conducted a series of laser drilling experiments with different parameters such as repetition rate, laser power and pulse number. Comparison of the results of simulations and experiments were conducted to verify the accuracy of the improved model. The comparison results proved that plasma play a significant role in pulsed laser drilling and the accuracy of the modificated model is very high. There is another conclusion that the influence of defocusing effect on laser drilling is greater than that of energy absorption.