Simultaneous multi-microhole drilling of soda-lime glass by water-assisted ablation with femtosecond laser pulses

Longitudinal and transverse microholes are drilled in soda-lime glass by water-assisted ablation with femtosecond laser pulses. True three-dimensional microchannels consisting of longitudinal and transverse microholes are presented. At low incident pulse energy, only one transverse microhole is observed. At high incident pulse energy, multiple transverse microholes can be simultaneously drilled. Using a focusing lens with numerical aperture of 0.5, two, three and four transverse microholes are fabricated at 3.2, 4.9 and 9.3µJ/pulse, which is qualitatively explained by the multiple foci process.