Crack growth analysis of ultraviolet nanosecond laser scanning glass with acoustic emission.

Undesirable crossing crack defects are prone to occur in the laser processing of glass, but a comprehensive analysis of the crack mechanism is absent. We apply an acoustic emission (AE) monitoring technique in the glass's laser scanning to reveal the crack phenomenon. A two-step experiment (single-line and multi-line scanning) is designed to present the crossing crack's occurrence and growth, and the corresponding AE signals are collected and analyzed in different domains. The time-domain AE feature (root mean square) correlates strongly with the laser ablation intensity in the single-line scanning experiment, and the frequency content of 150 ∼ 200 kHz is extracted as the crack characteristic in the multi-line experiment. The crossing crack growth is proved to be generated by the rapid release of thermal stress in the overlapped heat-affected zone by a brief mechanism discussion. This paper interprets the crack behavior in glass's laser scanning and provides a basis for other monitoring research on laser processing.