| Abstract [eng] |
The goal of this study – to evaluate water, KOH, NaCl solutions impact on glass samples femtosecond laser micromachining. Main tasks: 1. To perform femtosecond laser micromachining of glass samples in air, water, KOH and NaCl solutions. 2. To evaluate profile alteration of formed grooves depth when machining is performed on dry glass surface and on the contrary when sample is immersed in solution. Lasers with ultrashort pulse durations have demonstrated excellent micromachining quality, because pulse widths are shorter than the time for converting the energy of excited electrons into thermal energy [6, 7]. Micromachining performed in liquids can significantly improve the ablation quality and material removal efficiency. Bubbles that form in the liquid during laser heating determine used liquids movement. Throughout ablation process removed material particles sink slower in liquids. In this way sediment can be removed efficiently from laser formed grooves. Also, additional water layer above material surface performs a cooling function so sample fractures and cracks are avoided. Usually water is the most commonly used liquid medium for femtosecond laser micromachining [9–13]. In this study glass samples laser micromachining was performed in various concentrations of KOH and NaCl solutions, water and on dry sample surface. In the experiments, when the salt and KOH solutions are maintained above the sample, the etching properties are more pronounced at a lower scanning speed. In this case, greater number of pulses is detected per unit area, therefore higher temperature is reached which speeds up the etching processes. Formed grooves depth and its’ profile were analysed in various mediums while changing the number of scans. Micromachined formed grooves were deeper on dry samples in comparison to liquid medium when the number of scans was low (1 – 500). By increasing the number of scans (500 – 5000), deeper grooves were obtained when an additional layer of water or KOH solutions were maintained above the sample. When the number of scans is equal to 5000, the groove depths vary even by 2,7 times. Although the KOH solution has strong etching properties, the depth of the grooves obtained by immersing the glass in this solution is compared with that formed by maintaining the water layer above the sample. Selected high scanning speed and during the reaction formed hydrogen bubbles may have prevented reaching deeper depths. Grooves depth profiles were also evaluated. The grooves formed in the liquid medium are characterized by blunt apexes. The pointed shape is characterized by grooves obtained on the dry surface of the sample. It is hypothesized that the additional layer of liquid replaces Gaussian beam. For this reason, the larger depths of the formed grooves are achieved and changes in the shape of the profiles observed. |
