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Optical Engineering

Ultrafast reflection and secondary ablation in laser processing of transparent dielectrics with ultrashort pulses
Author(s): Mingying Sun; Urs Eppelt; Wolfgang Schulz; Jianqiang Zhu
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Paper Abstract

Ultrafast reflection and secondary ablation have been theoretically investigated with a Fresnel-Drude model in laser processing of transparent dielectrics with picosecond pulsed laser. The time-dependent refractive index has a crucial effect on the cascade ionization rate and, thereby, on the plasma generation. The relative roles of the plasma gas and the incident angle in the reflection are discussed in the case of the oblique incidence. The angular dependence of the reflectivity on the laser-excited surface for s- and p-polarization is significantly different from the usual Fresnel reflectivity curve in the low-fluence limit. A road map to the secondary ablation induced by the reflected pulse is obtained on the angles of the first and second incidence. It indicates that the laser-induced plasma plays a major role in the secondary ablation, which could overcome the saturation of the ablation crater depth or generate microcracks underneath the crater wall.

Paper Details

Date Published: 27 January 2014
PDF: 9 pages
Opt. Eng. 53(5) 051512 doi: 10.1117/1.OE.53.5.051512
Published in: Optical Engineering Volume 53, Issue 5
Show Author Affiliations
Mingying Sun, Shanghai Institute of Optics and Fine Mechanics (China)
Urs Eppelt, Fraunhofer-Institut für Lasertechnik (Germany)
Wolfgang Schulz, Fraunhofer-Institut für Lasertechnik (Germany)
Jianqiang Zhu, Shanghai Institute of Optics and Fine Mechanics (China)


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