Time resolved studies reveal the origin of the unparalleled high efficiency of one nanosecond laser ablation in liquids

Abstract

Laser ablation in liquid is a scalable nanoparticle production method with applications in areas like catalysis and biomedicine. Due to laser-liquid interactions, different energy dissipation channels such as absorption by the liquid and scattering at the ablation plume and cavitation bubble lead to reduced laser energy available for nanoparticle production. Ultrashort pulse durations cause unwanted nonlinear effects in the liquid, and for ns pulses, intra-pulse energy deposition attenuation effects are to be expected. However, intermediate pulse durations ranging from hundreds of picoseconds up to one nanosecond have rarely been studied in particular in single-pulse settings. In this study, we explore the pico-to nanosecond pulse duration regimes to find the pulse duration with the highest ablation efficiency. We find that pulse durations around 1 –2 ns enable the most efficient laser ablation in liquid since the laser beam shielding by the ablation plume and cavitation bubble sets in only at longer pulse durations. Furthermore, pump-probe microscopy imaging re-veals that the plume dynamics in liquids start to differ from plume dynamics in air at about 2 ns after pulse impact.