Debris-free rear-side picosecond laser ablation of thin germanium wafers in water with ethanol

- Picosecond laser cutting of fragile 150 μm thin germanium wafers (typically used for solar cell applications) in liquid results in debris-free surfaces.
- Liquid-assisted laser cutting is much better than air-assisted laser cutting in terms of recast, debris and cleanness of the resultant grooves.
- Laser cutting in ethanol-water mixtures result in better cut quality than those performed in pure water but lead to less cutting efficiency.
- Low repetition rate (10 kHz), mixed solution (1 wt% ethanol in water) and moderate scanning speed (100 μm/s) are preferable for ultrafine high-quality debris-free cutting.