Modification of narrow ablating capillaries under the influence of multiple femtosecond laser pulses

TL;DR

This study investigates how femtosecond laser pulses modify narrow ablating capillaries, revealing surface structures, droplet deposition, and plug formation through experimental and theoretical analysis.

Contribution

It introduces a theoretical model predicting universal plug formation in narrow tubes subjected to short laser pulses, supported by experimental observations.

Findings

LIPSS and porous coatings form at low intensities

Droplet deposition occurs at higher intensities

A solid plug eventually blocks the capillary after many pulses

Abstract

Powerful femtosecond laser pulses that propagate through narrow ablating capillaries cause modification of capillary walls, which is studied experimentally and theoretically. At low intensities, laser-induced periodic surface structures (LIPSS) and porous coating composed of sub-micron particles appear on the walls. At higher intensities, the surface is covered by deposited droplets of the size up to 10 $\mu$m. In both cases, the ablated material forms a solid plug that completely blocks the capillary after several hundreds or thousands of pulses. The suggested theoretical model indicates that plug formation is a universal effect. It must take place in any narrow tube subject to ablation under the action of short laser pulses.