Optical vortex torque measured with optically trapped microbarbells

TL;DR

This paper demonstrates a method to measure optical vortex torque using optically trapped microbarbells in a two-laser tweezers setup, combining experimental and modeling approaches for precise torque quantification.

Contribution

It introduces a novel microtool and experimental configurations for accurate optical vortex torque measurement, validated by numerical and analytical models.

Findings

Consistent torque measurements across four trapping configurations.

Agreement between experimental results and theoretical models.

Effective use of microbarbells in optical torque sensing.

Abstract

Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool - a microbarbell - is used in a two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four different trapping configurations provided different ways of sensing the torque and gave consistent results. The value of torque was determined by confronting the experimental results with numerical and analytical models.