Experimental investigation of laser induced breakdown thresholds for bulk water

Abstract

Bulk water is one of the important transparent medium for laser applications. Its laser-induced breakdown threshold (LIBT) is of special value for the understanding of laser propagation and laser-induced damage. And it is also very important for laser applications such as laser-induced plasma spectroscopy. To further research the influence of water quality on the breakdown threshold, the breakdown of water and salt solution by nanosecond laser pulse irradiation was investigated in this work. It was found that the LIBT of solution decreased significantly with the increase of zinc acetate concentration, while the LIBT of pure water remained 1.705×1012 W/cm2. There is a linear correlation between zinc ion concentration and laser breakdown threshold. The difference between water and salt solution may suggest that impurities play an important role in laser damage in transparent media. The result provides a guidance for the understanding of the mechanism of laser damage for optically transparent media and LIBS application to detect metal ion in solution.