Ablation induced by single-and multiple-femtosecond laser pulses in lithium niobate

We present results on the surface-damage threshold of lithium niobate after single-and multiple-femtosecond laser pulse irradiation at the pulse duration of 80 fs, with a 800-nm wavelength, and a repetition rate of 1 kHz. The surface-ablation threshold was found to decrease significantly with an increase in the pulse number applied to the surface until reaching an almost constant level due to an incubation effect, which is attributed to the laser-induced defect formation. The threshold of lithium niobate under a single shot is found to be 2.82 J/cm², and the threshold fluence for an infinite number of pulses F _th(∞) converges to a common value of 0.52 ± 0.06 J/cm² for N > 80. The results have the potential for application in laser micromachining and the fabrication of related optical devices and applications in frequency conversion by a femtosecond laser in lithium niobate.