CHARACTERISTICS OF OPTICAL-BREAKDOWN IN ULTRAPURE WATER INDUCED BY NANOSECOND ND-YAG LASER-PULSES

Characteristics of dielectric breakdown in ultrapure liquid water using single nanosecond laser pulses have been investigated. The threshold for the systematic occurrence of laser-induced breakdown of ultrapure water has been found to be about one order of magnitude below the threshold of distilled water, and of impurity-rich liquids like ordinary tap water. The behaviour of the threshold value in relation to the addition of impurities is rather anomalous when compared to that of other liquids. The length of the plasma column with increasing input irradiance adheres to the model of moving breakdown. These findings are commented on the light of current knowledge of laser-induced plasmas in liquids and of their initiation mechanisms.