Threefold Efficiency Enhancement and Narrowed Nanoparticle Size Distribution in Laser Ablation of Gold in Water by GHz-Burst Irradiation

Abstract

Laser ablation in liquids enables the synthesis of surfactant-free nanoparticles but remains limited in productivity due to intrinsic constraints imposed by the liquid environment. These constraints include nonlinear optical losses, material redeposition, and cavitation bubble-induced shielding. Temporal intensity shaping of the incident laser pulse offers a potential route to mitigate these limitations. Here, ultrashort GHz-burst ablation is applied to laser ablation of gold in water. By distributing the pulse energy into a sequence of picosecond sub-pulses arriving within the nanosecond time window preceding cavitation bubble formation, GHz-burst irradiation enables energy delivery before the onset of bubble-induced shielding. This increases the threshold fluence for nonlinear losses and yields an ablation efficiency enhancement of up to a factor of three compared to single-pulse ablation. Importantly, this efficiency gain is not accompanied by an increase in cavitation bubble size or lifetime. In addition to enhanced efficiency, burst irradiation yields a twofold narrower nanoparticle size distribution. These results demonstrate that GHz-burst ablation is a promising approach to increase productivity while simultaneously improving nanoparticle quality.