Coupled dipole method to compute optical torque: Application to a micropropeller

Abstract

The coupled dipole method is a volume integral equation method which allows computation of the scattered field from an arbitrary object (shape and relative permittivity). This method has been extended to the computation of optical forces. In this article we further extend the coupled dipole method to the computation of optical torque. First, we establish the equation to obtain the optical torque using the coupled dipole method, stressing the importance of the radiative reaction term. Second, we compare our theory to existing models for validation. Third, we apply our method to the computation of optical torque, from a plane wave circularly polarized on a micropropeller. The influence of geometry and relative permittivity on the optical torque is studied.