Dynamical characteristics of tightly focused flat-topped double vortex beam for enhanced optical manipulation

Abstract

The Flat-topped Vortex (FTV) beam has shown remarkable utility in a diverse range of industrial procedures, primarily attributed to its central intensity plateau. Nevertheless, the substantial potential of the FTV beam in particle trapping and manipulation has been largely underappreciated. In this work, we conducted the first study on the focusing properties and dynamic characteristics of the Flat-topped double vortex (FTDV) beam under different polarization for the absorption of Rayleigh particles. Through superimposing linearly two FTV beams with equal but opposite topological charges, the FTDV beam emerged naturally. Moreover, a comprehensive numerical analysis was subsequently performed to decode the interactions between the focusing field of the FTDV beam and Rayleigh particles. The analysis demonstrated that the focusing field of FTDV beam can perform multi-particle capture and effectively manipulate particles by modulating the topological charge |m|, the flatness order n, and the polarization state of the FTDV. Furthermore, a comparison between the focusing field of FTDV beam with that of vector vortex (VV) beam revealed that the FTDV beam was capable to generate spin angular momentum (SAM) density and spin torque at least an order of magnitude higher. These findings highlight the superior capabilities of FTDV beam in optical manipulation, and provide essential theoretical support for its utilization in particle capture and management.