Electrostrictive counter-force on fluid microdroplet in short laser pulse

TL;DR

This paper analyzes how ultrashort laser pulses affect fluid microdroplets, revealing the interplay between electrostriction and electromagnetic forces that determine whether droplets are compressed or deformed.

Contribution

It provides an analytical and numerical analysis of electrostrictive effects on fluid microdroplets under short laser pulses, bridging a gap in understanding laser-matter interactions.

Findings

Electrostriction counteracts radiation force in short pulses.

Longer pulses lead to droplet deformation due to electromagnetic forces.

Theoretical framework for combining electrostriction and electromagnetic effects.

Abstract

When a micrometer-sized fluid droplet is illuminated by a laser pulse, there is a fundamental distinction between two cases. If the pulse is short in comparison with the transit time for sound across the droplet, the disruptive optical Abraham-Minkowski radiation force is countered by electrostriction and the net stress is compressive. In contrast, if the pulse is long on this scale, electrostriction is cancelled by elastic pressure and the surviving term of the electromagnetic force, the Abraham-Minkowski force, is disruptive and deforms the droplet. Ultrashort laser pulses are routinely used in modern experiments, and impressive progress has moreover been made on laser manipulation of liquid surfaces in recent times, making a theory for combining the two pertinent. We analyze the electrostrictive contribution analytically and numerically for a spherical droplet.