Initial process of the refractive index change induced by tightly focused femtosecond laser inside a transparent material

Masaaki Sakakura; Masahide Terazima

doi:10.1117/12.546952

20 September 2004 Initial process of the refractive index change induced by tightly focused femtosecond laser inside a transparent material

Masaaki Sakakura, Masahide Terazima

Author Affiliations +

Proceedings Volume 5448, High-Power Laser Ablation V; (2004) https://doi.org/10.1117/12.546952
Event: High-Power Laser Ablation, 2004, Taos, New Mexico, United States

Abstract

When a femtosecond laser pulse is moderately focused inside a glass using an objective lens, the density of the irradiated region increases. Although this phenomena has become one of the key technique to fabricate various three dimensional devices, the mechanism has not been well understood. In this study, the initial step of refractive index change of the irradiated region was investigated using the time-resolved transient lens method with a time resolution of sub-picosecond. The oscillating signal intensity with several GHz was observed, and it was interpreted in terms of the density change due to the thermoelastic relaxation after the photoexcitation. The calculation of the thermoelastic relaxation of the ultrafast heated material surrounded by the solid material indicates that the density at the center of the heated region is reduced, and the acoustic wave is generated and propagated. The oscillation in the transient lens signal can be almost perfectly simulated using the density change from the thermoelastic calculation. The temporal profile of the transient lens signal will be a good method to monitor the time dependence of the refractive index change at the laser light focal region.

Citation Download Citation

Masaaki Sakakura and Masahide Terazima "Initial process of the refractive index change induced by tightly focused femtosecond laser inside a transparent material", Proc. SPIE 5448, High-Power Laser Ablation V, (20 September 2004); https://doi.org/10.1117/12.546952

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