Micromachining of borosilicate glass surfaces using femtosecond higher-order Bessel beams

We report experimental results on micromachining of borosilicate glass slides with femtosecond higher-order Bessel beams. Transverse intensity profiles of these beams comprise concentric rings that are maintained over extended linear focus zones, facilitating machining geometries with large working distances and high aspect ratios. Both single-shot and multi-shot front-surface machining and multi-shot back-surface processing are experimentally investigated. Material removal in the latter case is furnished through the immersion of the back side of the glass slide in water. Under certain conditions, we observe evidence of self-focusing and azimuthal breakup of the initially smooth ring intensity features of the beams near the glass-water interface. These beam dynamics result in the formation of beaded ring features on the back surface of the glass slide. In the case of multi-shot front-surface machining, pillar-like structures can be fabricated.