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Ultrafast Laser Drilling of Crack-Free, Debrisfree and Heat Affected Zone (Haz)-Free Blind Holes in Al2O3 with Flat Bottom and Reduced Taper Angles
Z-L. Li, O. Allegre, W. Guo, W-Y. Gao, B-H. Li, Q-L. Feng, X-P. Wu and L. Li

Laser drilling of blind holes in materials often results in tapering and pointed bottom due to inappropriate beam intensity distribution, beam geometry, beam focal position and material flow erosions. In this work the effect of polarization states on taper angle at different focal plane position was analysed. A new approach of using a spatial filter shaped Gaussian laser beam from a Ti:Sapphire femtosecond laser was introduced to control the taper in the laser drilling of blind holes in Al2O3 ceramic sheets. Low taper angles and flat bottom blind holes were demonstrated drilled with the femtosecond laser and the holes were free from microcracks, recast layer, debris and without obvious heat affected zone (HAZ).

Keywords: Ti:Sapphire femtosecond laser, alumina ceramic, Al2O3, laser drilling, blind hole, trepanning, taper angle, microcracks, recast layer, debris, spatter heat affected zone (HAZ)

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