Microdrilling of metals with ultrashort laser pulses

The pulse duration requirements for melting-free and burr-free drilling of metals have been observed in detail. It will be shown that the highest process efficiency and hole quality can be achieved by using pulse durations in the subpicosecond time scale. Furthermore, it will be demonstrated that nonlinear distortions due to high intensities can be successfully minimized by applying diffractive optical elements for beam forming. The influence of the polarization of the laser radiation on the process quality will be discussed. Experimental results will show that the rotation of linear polarized radiation during percussion drilling significantly improves the quality of the hole geometry.