Surface ablation of lithium tantalate by femtosecond laser

We report measurements of the laser induced breakdown threshold in lithium tantalate with different number of pulses delivered from a chirped pulse amplification Ti: sapphire system. The threshold fluences were determined from the relation between the diameter D2 of the ablated area and the laser fluence F0. The threshold of lithium tantalite under single-shot is found to be 1.84 J/cm2, and the avalanche rate was determined to be 1.01 cm2/J by calculation. We found that avalanche dominates the ablation process, while photoionization serves as a free electron provider.