Experimental studies on ablation characteristics of alumina after irradiation with a 193-nm ArF excimer laser

Laser ablation of alumina ceramics was performed in the ambient air using a 193-nm ArF excimer laser. The effect of the laser parameters (pulse repetition frequency, laser spot diameter, fluence, and the number of laser pulses) on the ablation behavior was investigated. Scanning electron microscopy, optical microscopy, Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) were used to assess the crater morphology, ablation depth, and changes in the structure and chemical composition of the ablated material. There was no significant difference in the ablation rate between craters produced at a pulse repetition frequency of 10 and 100 Hz using a number of laser pulses up to 500. Increasing pulse repetition frequency to 300 Hz slightly reduced the ablation rate of the craters produced using > 150 laser pulses. The ablation rate was found to decrease from pulse to pulse at high fluence and was higher for small (25 µm) than for large (110 µm) laser spot diameters. The Raman and EDS spectra, collected at and near the ablated craters, were similar to those collected at pristine non-ablated areas, indicated no changes in the structure and chemical composition of alumina due to ablation. Ablation threshold fluence was calculated from the relationship between ablation rate and fluence for craters produced using 60 laser pulses and was found to be 1.35 J/cm2.