Femtosecond pulse laser ablation of sapphire in ambient air

Femtosecond pulse laser ablation (pulse duration 150 fs, wavelength 775 nm, repetition rate 250 Hz) of sapphire in the ambient air was investigated. The quality and morphology of laser ablated sapphire were evaluated. The surface ablation threshold was found to decrease significantly with increasing the pulse number applied to the surface until reaching an almost constant level due to an incubation effect which is attributed to laser-induced defect formation. It was also showed that submicrometer pit holes, whose dimension was smaller than 1 mm, were produced with single femtosecond pulse due to the selffocusing effect of air. Under appropriate laser conditions, femtosecond pulse laser etching of sapphire with high quality could be achieved. The results have important consequences for applications, such as laser micromachining, and fabrication of sapphirerelated devices. # 2004 Elsevier B.V. All rights reserved.