Damage-free cutting of chemically strengthened glass by creation of sub-surface cracks using femtosecond laser pulses

Chemically strengthened glass used for smartphones and tablets is cut into elaborate shapes by creating internal cracks using femtosecond laser pulses. The peak power is set at near ionization intensities of similar to 10(14) W/cm(2) to initiate sub-surface cracks by strong nonlinear absorption underneath the stress-compressed glass surface at a 560 mu m depth. Then sub-surface cracks are laterally guided with a feed-rate of 5-40 minis to realize accurate cutting along tensile-residual-stress lines formed around the material-modified zone inside the glass substrate. The cutting plane maintains a mirror-like cross-section profile without excessive flaws and thermal damage usually seen in conventional laser ablation. (C) 2017 Published by Elsevier Ltd on behalf of CIRP.