Sensitive ablation of brittle materials with pulsed CO2 laser radiation

The interaction process between pulsed CO2 laser radiation and glass was studied systematically. The concept of the structuring process is related to an absorption-controlled ablation of small elementary material volumes with reduced melt formation, the so-called elementary volume ablation (EVA). For this purpose, suitable pulse parameters were predicted on the basis of the optical and thermal materials properties. These pulses with durations as low as 10 μs and a peak power of up to 600 W were generated using a specific arrangement consisting of a commercially available continuous CO2 laser of high beam quality and a cascade of two interference laser beam modulators. Optical microscopy, scanning electron microscopy, white light interferometry, and tactile profilometry were used to investigate the influence of the CO2 laser pulse parameters on the processing quality. The results obtained from the ablation of borosilicate glass (Borofloat33) and 100 μm thick sheets of cerium doped borosilicate glass demonstrate that the EVA method is a suitable approach to select an appropriate range of processing parameters for a high precision thermal ablation of glass without microcrack formation.