Contactless transfer of angular momentum by rotating laser beam

TL;DR

This paper demonstrates experimentally how a rotating laser beam can transfer angular momentum to a solid target without contact, with the direction of rotation depending on the liquid layer thickness, through thermocapillary and convective flows.

Contribution

It introduces a novel method for contactless angular momentum transfer using a rotating laser beam and analyzes the flow mechanisms involved.

Findings

Angular momentum transfer is achieved contactlessly via laser irradiation.

The direction of target rotation depends on the liquid layer thickness.

Thermocapillary and convective flows are key to the effect.

Abstract

Contactless transfer of angular momentum from rotating laser beam to a solid target is experimentally demonstrated. The effect is observed under irradiation of a glassy carbon target immersed in water by a pulsed laser beam that is scanned across the target surface along circular trajectory. The direction of target rotation coincides with that of the laser beam at small thickness of the liquid layer above the target while is opposite in case of higher thickness of the layer. The effect is interpreted as the interplay between thermocapillary and convective flows induced in the liquid by laser heating.