Experimental study on infrared nanosecond laser-induced backside ablation of sapphire

Experimental study has been performed on infrared nanosecond laser-induced backside ablation (LIBA) of sapphire with black paint as the backing layer, where laser energy absorption and material removal occur around the sapphire–backing-layer interface. The effect of laser fluence and pulse duration on ablation rate has been revealed. It has been found that LIBA using nanosecond lasers can produce ∼∼3 to ∼∼80 times higher ablation rate than direct laser ablation using femtosecond or picosecond laser pulses with the same fluence per pulse. Reasonably good ablation quality can be obtained using LIBA without chemical contamination from the backing layer. It has also been found that under the studied conditions the ablation rate in LIBA is not sensitive to laser pulse duration, and the damage threshold is not sensitive to laser pulse number. The experimental data in this work provides very important and useful information for practical applications of LIBA in sapphire micromachining and for the fundamental understanding and quantitative modeling of the process.