Focusing effects during ultrashort-pulse laser ablative generation of colloidal nanoparticles for antibacterial applications

Ultrashort (femto-picosecond) laser pulses with supercritical peak pulse powers undergo self-focusing and multiple filamentation during their propagation in transparent media. In this work, a comparative study of propagation and position-dependent ablation of a gold target in water by 0.3 ps and 10 ps 1030 nm laser pulses was performed. The filamentary laser propagation was visualized in water by the corresponding pre-focal plasma channels. The position-dependent ablative optical density yield of colloidal solutions and target mass loss along the filamentary tracks in water were characterized, for the first time enabling straightforward enhancement of colloidal generation for anti-bacterial, biomedical and nanophotonics applications.