Three-dimensional hole drilling of silica glass from the rear surface withfemtosecond laser pulses

By moving silica glass in a preprogrammed structure, we directly produced t hree-dimensional holes with femtosecond laser pulses in single step. When d istilled water was introduced into a hole drilled from the rear surface of the glass, the effects of blocking and redeposition of ablated material wer e greatly reduced and the aspect ratio of the depth of the hole was increas ed. Straight holes of 4-mum diameter were more than 200 mum deep. Three-dim ensional channels can be micromachined inside transparent materials by use of this method, as we have demonstrated by drilling a square-wave-shaped ho le inside silica glass. (C) 2001 Optical Society of America.