Dynamics of titanium ablation suppression induced by below-ablation-threshold femtosecond laser pulse irradiation

Y. Furukawa; S. Inoue; M. Hashida

doi:10.1117/12.2577962

5 March 2021 Dynamics of titanium ablation suppression induced by below-ablation-threshold femtosecond laser pulse irradiation

Y. Furukawa, S. Inoue, M. Hashida

Author Affiliations +

Proceedings Volume 11673, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXVI; 116730O (2021) https://doi.org/10.1117/12.2577962
Event: SPIE LASE, 2021, Online Only

Abstract

We have discovered that the pre-irradiation of a below-ablation-threshold femtosecond laser pulse (first pulse) suppressed titanium ablation rate by subsequent irradiation of another above-ablation-threshold femtosecond laser pulse (second pulse). To ablate titanium targets, we used linearly polarized femtosecond laser pulses (810nm wavelength, 45fs pulse duration, 10Hz repetition rate). Ablation suppression was transiently observed with the delay of several hundreds of picosecond. With these delays, the ablation rate with 10% below-ablation-threshold first-pulse pre-irradiation was suppressed to half of that without pre-irradiation. This result indicated that the below-ablation-threshold first-pulse preirradiation does not ablate the titanium target but changes the optical property of the surface. To understand the physics of the ablation suppression, we have developed and performed a new measurement to estimate the temporal changes of the effective laser penetration length (LPL) induced by the below-ablation-threshold first-pulse pre-irradiation. We developed a new description of the dependence of the ablation rate on the laser fluences and delay by considering the absorption and decay of the laser pulse energy in the target. We have demonstrated that below-ablation-threshold firstpulse pre-irradiation reduced LPL with the delay of several hundreds of picosecond. The result indicated that the preirradiation of a below-ablation-threshold first-pulse changed the titanium surface into a novel state with reduced LPL, which is not explained by simple heating of surface.

Conference Presentation

Citation Download Citation

Y. Furukawa, S. Inoue, and M. Hashida "Dynamics of titanium ablation suppression induced by below-ablation-threshold femtosecond laser pulse irradiation", Proc. SPIE 11673, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXVI, 116730O (5 March 2021); https://doi.org/10.1117/12.2577962

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