Gas ejection mechanism of glass structuring induced by nanosecond laser pulses

Abstract

In this work, results on a new laser-induced mechanism of microstructures formation on the surface of borosilicate glass are presented. The samples are fabricated by melt quenching method and consist of 50% SiO2, 20% Al2O3, 20% B2O3, 5% CaO, 2% Li2O, 3% MgO (in wt.%). Irradiation at 266 nm delivered by Nd:YAG nanosecond system is used to modify the glass surface. It is found that this processing may result in the formation of voids in the irradiated area that have submicron mean diameter. The effect is observed at fluences below the ablation threshold. Different laser fluences and pulse number are applied to estimate their role on the induced surface morphology. It is observed that voids are also observed in the remaining material after ablation of the irradiated zone at high fluences. In this regime, glass structure modifications can also be observed under the glass surface at depths that may reach 100 µm. Based on measurements by differential thermal analysis equipped by mass spectrometer is concluded that the void formation is related to emission of gas phase from the glass induced by the laser heating.