Dynamics of multiple bubbles, excited by femtosecond filament in water: Role of aberrations

TL;DR

This study investigates the complex dynamics of cavitation bubbles generated by femtosecond laser filaments in water, highlighting the effects of aberrations and focusing conditions on bubble formation and evolution.

Contribution

It reveals how aberrations and focusing parameters influence cavitation bubble patterns and their interactions under high-energy femtosecond laser excitation.

Findings

Aberrations create hot spots along the filament axis.

Higher numerical aperture increases cavitation region length.

Bubble interactions significantly alter evolution, deviating from Rayleigh model.

Abstract

Using shadow photography, we observed microsecond time scale evolution of multiple cavitation bubbles, excited by tighty focused femtosecond laser pulse in water under supercritical power regime (~100 Pcr). In these extreme conditions high energy delivery into the microvolume of liquid sample leads to creation of single filament which becomes a source of cavitation region formation. When aberrations were added to the optical scheme the hot spots along the filament axis are formed. At high energies (more than 40uJ) filaments in these hot spots are fired and, as a result, complex pattern of cavitation bubbles is created. The bubbles can be isolated from each other or build exotic drop-shaped cavitation region, which evolution at the end of its life, before the final collapse, contains the jet emission. The dynamics of the cavitation pattern was investigated from pulse energy and focusing. We found that greater numerical aperture of the focusing optics leads to greater cavitation area length. The strong interaction between bubbles was also observed. This leads to a significant change of bubble evolution, which is not yet in accordance with Rayleigh model.