In this study we have focused on exploring the photoacoustic signal generated by laser induced dielectric breakdown
process in pure water, under normal conditions. In this case the dielectric breakdown will lead to a
formation of a shock wave. We investigated the relation between pulse energy and amplitude, group velocity and
power spectrum of the shock wave. Also, the threshold for dielectric breakdown is estimated. A pulsed, high
power Nd:YAG laser with λ = 532 nm and a pulse duration of 12 ns was used. The laser pulse energy ranges
from 0.1 mJ to 7.4 mJ. Only photoacoustic signals generated from dielectric breakdown was considered. We
found that the amplitude and the average group velocity of the shock wave correlates to the laser pulse energy.
The frequency contents of the photoacoustic signal changes due to both non-linear behaviour and dissipative
effects. We estimated the dielectric breakdown threshold to be 0.44 × 10<sup>11</sup>Wcm<sup>-2</sup>.