Improvement of rear damage of thin fused silica by liquid-assisted femtosecond laser cutting

Rear damage around cutting edge reduces its mechanical strength, which confines the application of femtosecond (fs) laser cutting thin fused silica. In this paper, we report a method by liquid-assisted cutting to minimize the damage. The surface morphology and area of damage are investigated. It is found that the damage can be decreased by altering the polarization from perpendicular (S-polarization) to be parallel (P-polarization) to the plane incidence, owing to the decrease of reflectivity on the boundary during fs laser cutting. Based on this theory, we further reduce the reflection on the rear side of the glass by adding water. Experienced twice scans, the damage area per unit length along cutting direction can be reduced from 41.84 to 1.88 μm2 by water cutting. This method can open up prospects for high precision fabrication of thin transparent material.