Optical force model based on sequential ray tracing

We discuss how information available from ray-tracing techniques can be used to calculate optical forces and torques on particles. A general ray-trace computer code is augmented with the polarization and irradiance distributions of the illumination and Fresnel surface coefficients to give a reasonably accurate prediction of interaction with large particles out of the focal plane. Calculations of trapping location versus nonuniform illumination conditions are compared with an experiment. Other example calculations include trapping a hemispherical lens and a two-particle trap. (C) 2009 Optical Society of America