Damage/ablation morphology of laser conditioned sapphire under 1064 nm laser irradiation

The damage/ablation morphologies and laser induced damage threshold (LIDT) of three different sapphire samples: original, 1064 nm laser conditioned and 10.6 mu m CO2 laser polished substrates are investigated with ns pulses laser irradiation. The results indicate that the damage resistance capability cannot be enhanced by 1064 nm laser conditioning or CO2 laser polishing. The damage/ablation morphology of 1064 nm-laser conditioned samples is same as that of the original sapphire. But it is different from the damage/ablation morphology of the CO2 laser polished sapphire. The "gentle and strong" ablation phases are observed in this work and several phenomena are observed in the two ablation phases. Ripple is observed in the "gentle" ablation processes, while convex spots and raised rims are observed in the "strong" ablation processes. Meanwhile, stripe damage and pin-points are observed in the CO2 laser conditioned sapphire after ns laser irradiation. The formation mechanisms of the phenomena are also discussed for the explanation of related damage/ablation morphology. The results may be helpful for the damage/ablation investigation of sapphire in high power laser systems. (C) 2011 Elsevier Ltd. All rights reserved.