Electrostrictive counterforce on fluid microdroplet in short laser pulse.

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.