Drop Shaping by Laser-Pulse Impact

TL;DR

This paper investigates how nanosecond laser pulses cause liquid drops to propel and deform, combining experiments and simulations to understand the underlying physics relevant for nanolithography.

Contribution

It provides a detailed analysis of laser-induced drop propulsion and deformation, integrating experimental measurements with boundary-integral simulations.

Findings

Drop propels at several meters per second after laser impact

Deformation and fragmentation depend on laser energy and drop properties

Propulsion driven by recoil momentum from vaporization

Abstract

We show how the deposition of laser energy induces propulsion and strong deformation of an absorbing liquid body. Combining high speed with stroboscopic imaging, we observe that a millimeter-sized dyed water drop hit by a millijoule nanosecond laser pulse propels forward at several meters per second and deforms until it eventually fragments. The drop motion results from the recoil momentum imparted at the drop surface by water vaporization. We measure the propulsion speed and the time-deformation law of the drop, complemented by boundary-integral simulations. The drop propulsion and shaping are explained in terms of the laser-pulse energy, the drop size, and the liquid properties. These findings are, for instance, crucial for the generation of extreme ultraviolet light in nanolithography machines.