[12p-B410-1~16] 3.7 Laser processing

△ [12p-B410-9] Temporal change of the optical properties of titanium induced by pre-irradiation of below-ablation-threshold femtosecond laser pulse

〇(DC)Yuki Furukawa^1,2, Masaki Hashida^1,2, Shunsuke Inoue^1,2, Shuji Sakbe^1,2 (1.ICR, Kyoto Univ., 2.GSS, Kyoto Univ.)

Keywords:metal, ablation, optical properties

We have discovered that the pre-irradiation of a femtosecond laser pulse with the fluence below the ablation threshold of the titanium target reduces the ablation by the subsequent irradiation of another femtosecond laser pulse. This result suggested that the below-ablation-threshold pre-irradiation changed the optical properties of titanium surface. To verify this hypothesis, we developed and performed a new pump-and-probe measurement to estimate the temporal change of the effective laser penetration depth and the effective ablation threshold induced by a below-ablation-threshold pre-irradiation. The result indicates that the effective laser penetration depth of the titanium target was reduced by a below-ablation-threshold pre-irradiation with a delay of several hundreds of picosecond, resulting in the suppression of the ablation by the subsequent femtosecond laser pulse.