Optical torque on a Rayleigh particle by photonic jet

Abstract

The optical torque exerted on a dielectric Rayleigh spherical particle by photonic jet is investigated. In the study of optical torque by dipole approximation, orbital and spin torques are usually considered. Optical Orbital Torque (OOT) is a type of optical torque that causes a particle to rotate along the optical axis, and the rotation of a tiny particle around its center of mass is caused by Optical Spin Torque (OST). The photonic jet is generated by a plane wave illuminating a dielectric Generalized Luneburg Lens (GLLs). The effects of wavelength, focal length and radius of the GLLs on the OOT and OST are analyzed in this paper. The numerical results show that the wavelength and focal length of GLLs greatly affect the optical orbital torque. Optical spin torques contain a large amount of negative torques and are sensitive to the focal length of the GLLs. The results of this paper are expected to provide theoretical support for the manipulation and rotation of the Rayleigh particle.