Simultaneous measurements by two techniques for in situ laser-induced damage threshold (LIDT) detection, based on optical diffraction and acoustic measurements, were demonstrated. Pulsed Nd:YAG laser (532 nm) ablation of 25-nm-thick aluminum films on quartz was studied as a test case. The two probes gave consistent LIDT values, and were sensitive and simple to operate. For above-threshold ablation, the diffraction and acoustic signals were found to be strongly correlated, rendering them useful not just for threshold detection, but for studying ablation dynamics as well.
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