Force and torque on an electric dipole by spinning light fields

TL;DR

This paper analyzes how spinning light fields exert force and torque on electric dipoles, revealing the dependence of force on orbital energy flow and the torque on spin energy flow, with implications for plasmonic configurations.

Contribution

It introduces a detailed calculation of optical force and torque on dipoles in spinning light fields, emphasizing the role of phase gradients and energy flows, especially near plasmonic surfaces.

Findings

Dissipative force depends on orbital energy flow.

Spin energy flow induces optical torque.

Surface plasmon modes significantly alter force behavior.

Abstract

We calculate the optical force and torque applied to an electric dipole by a spinning light field. We find that the dissipative part of the force depends on the orbital energy flow of the field only, because the latter is related to the phase gradient generalized for such a light field. As for the remaining spin energy flow, it gives rise to an optical torque. The resulting change in the optical force is detailed for different experimentally relevant configurations, and we show in particular how this change is critical when surface plasmon modes are involved.