Investigation of glass rear side milling using laser

Fast growing market of glass microelements leads to higher demand on laser machining because of its high quality and speed. Laser rear side milling is attractive glass machining method because it allows to mill complex shapes with zero taper walls. However, there is still lack of information about this technology when milling with different parameters. The aim of this work is to investigate the glass rear side milling using first harmonic wavelength with nanosecond and picosecond pulses and burst regime. It was shown that the optimal parameters for milling undamaged and damaged surfaces differ, because of the larger damage treshold of the polished surface. Therefore, for the initiation of stable milling, the surface needs to be processed. For example, it could be roughened or coated with absorbtive coating. When milling is done with the minimal fluence needed to achieve stable milling with 13 ps the average roughness is 5,5 times smaller (1,5 μm Ra) than with 5 ns (8,2 μm Ra). The average surface roughness is 3,7 times larger when comparing milling with bursts from 20 pulses (6 μm Ra) to single pulse regime (1,6 μm Ra). Experiments has shown that rear side milling with bursts proves to be advantegous over the single pulse regime when milling with 5 ps pulses. The efficiency is 2,6 times higher when comparing to the single pulse milling. The highest efficiency value of 0,29 mm3/J was achieved with 1030 nm 100 kHz 53 J/cm2 bursts from 20 pulses. The highest milling efficiency value found in scientific literature for fused silica laser milling is 2,2 times smaller than the efficiency demonstrated in this work.