Numerical analysis of an optical motor based on the radiation pressure

摘要

The radiation force exerted on a transparent disk-type optical rotator with shape dissymmetry is predicted using a ray-optics model. We performed a quantitative analysis of the torque exerted on the rotator while in a single-beam gradient-force optical trap. Rotation is due to the optical torque from the laser radiation pressure on the side walls. Thus, the maximum torque is obtained when a large proportion of the laser beam is incident to the side walls. Both the trapping force and the torque depend strongly on the position of the rotator and the numerical aperture. We also found that there is an optimum value of NA at which the maximum torque is generated. The validity of the ray-optics model for polystyrene latex spheres in the trap was also confirmed by our experimental results. From the experimental rotation speed of the polyimide rotator and the numerical results, we quantified the damping factor and the static frictional torque of the rotator.