| Abstract [eng] |
The goal of this work was to investigate the in-volume modification of glass combined with a mechanical cleaving process for glass cutting using picosecond Bessel-Gaussian beams. Experiments were carried out using the fundamental harmonic of diode-pumped solid-state lasers with pulse duration of 10 ps and 300 ps. The Bessel-Gaussian beam was generated by focusing the Gaussian beam with a conical lens together with a 4F optical system. The conical lens, generated intensity distribution, in-volume modifications of glass were investigated and glass cutting experiments were carried out during this research. It was found that due to manufacturing tolerances the investigated conical lens shape deviated from an ideal cone and had an oblate tip and an ellipse-shaped cross-section. The intensity pattern, generated by such lens, was nonsymmetrical and modulated along the propagation axis. The central core diameter depended on the distance from the axicon tip. Also, as the beam propagation distance increased, the intensity pattern was gradually spread into several maxima. Such beam distribution affected the formation of cracks in the bulk of glass, which tended to orientate along the major axis of an ellipse-shaped central core of the beam. The maximum length of cracks was 183 μm when 2 mJ laser pulses with duration of 300 ps were applied. Cracks size depended linearly on the pulse energy on the logarithmic scale. It was demonstrated that the direction of cracks orientation can be adjusted by rotating an axicon. Laser induced in-volume modifications combined with a cleaving process could be applied for thick glass cutting. Cutting of straight contours was demonstrated by single pass technique using a Bessel-Gaussian beam and 300 ps laser pulses. Maximum cutting speed of 1 mm-thick soda-lime glass sheets was 240 mm/s when 2 mJ laser pulses were applied. Cutting quality depended on the pulse energy and scanning speed. Minimal sidewall surface roughness was 1.6 μm when the pulse energy was 0.6 mJ, scanning speed 10 mm/s. It was concluded that the optimal cutting speed with the lowest roughness depends linearly on the pulse energy. |
