Experiments of collinear Double Pulse Laser Ablation in Liquid (DP-LAL) were carried out for studying the production mechanisms of nanoparticles (NPs) in water, which revealed the fundamental role of the cavitation bubble dynamics in the formation of aqueous colloidal dispersions. In this work, DP-LAL was used to generate silver nanoparticles (AgNPs) from a silver target submerged in water at atmospheric pressure and room temperature, by using the second harmonic (532 nm) of two Nd:YAG lasers. The second laser pulse was shot at different delay times (i.e. interpulse delay) during the bubble temporal evolution of the first laser induced bubble. Optical Emission Spectroscopy, Shadowgraph Images, Surface Plasmon Resonance absorption spectroscopy and Dynamic Light Scattering were carried out to study the behaviour of laser-induced plasma and cavitation bubbles during the laser ablation in liquid, to monitor the generation of AgNPs under different conditions, and for characterization of NPs. The results of DP-LAL were always compared with the corresponding ones obtained with Single Pulse Laser Ablation in Liquid (SP-LAL), so as to highlight the peculiarities of the two different techniques.

Considerable interest has been paid to laser-induced breakdown in liquid because of its wide application to medical issues of the eye and environmental monitoring. Therefore, the present work aims to study the phenomena of LIB in bulk distilled water generated in laser-induced breakdown spectroscopy (LIBS) experiment. The effect of experimental parameters such as inter-pulse delay between the two lasers, laser pulse energy and detection time window have been studied to examine the temporal growth of the laser-induced plasma in bulk water. Electron density and plasma temperature have been determined. The Stark broadening profile has been utilized for the electron density determination where the hydrogen lines $H_{\unicode[STIX]{x1D6FC}}$ and $H_{\unicode[STIX]{x1D6FD}}$ have been used. A deviation between electron density values from the broadening of both lines has been observed and discussed. The electron density values are varied between $10\text{E}+18$ and $10\text{E}+17~\text{cm}^{-3}$ corresponding to the timing experimental parameters. The plasma temperature is varied over a range 16 000 $\text{K}$ to 10 700 $\text{K}$ due to the plasma’s temporal behaviour with experimental parameters.