The experimental results of drilling microholes using high energy picosecond laser pulses is reported. The aim of this study is to present the limits of laser drilling in respect to the maximum drilling depth and quality. The experiments has performed with a laser source with pulse energies up to 1.3 mJ and repetition rates in the range of 30 kHz to 300 kHz. Using an online OCT, the drilling progress was observed. A maximum drilling depth of up to 8 mm was achieved.
A combination of a cylindrical lens with a spherical lens was used to create an elliptical beam shape on the surface of the processed workpieces in order to increase the ablation efficiency producing linear grooves. Near-infrared 8 ps laser pulses with energies of up to 2.3 mJ were applied at a repetition rate of 300 kHz to ablate the grooves on the surface of the samples. The ablation rates obtained at different feed rates were examined. At a peak fluence of 4 J/cm2, an power specific ablation rate of almost 0.4 mm3/min/W was achieved for a beam with an ellipticity of 0.9955.