Absorption dynamics and structural changes due to laser-induced breakdown in transparent dielectrics

Abstract

Amount of energy deposited by a single, tightly focused nanosecond laser pulse in different transparent materials was measured vs. either the incident intensity or energy fluence. An integrating sphere enabled quantification of the energy scattered during the long-lived breakdown process. It was shown that absorptance dependence on the photon flux can be analytically described by the sigmoidal Hill function. We suggest using this analytical description to quantify empirical laser-induced breakdown threshold (LIBT). The structured changes in the breakdown area were analysed by the means of different kinds of microscopy, especially by the high-resolutiontransmission-electron-microscopy (HRTEM). The analysis revealed nanocrystallisation in the densified material surrounding the void.