OPTICAL FORCE ON A SPHERE CAUSED BY THE EVANESCENT FIELD OF A GAUSSIAN-BEAM - EFFECTS OF MULTIPLE-SCATTERING

We examine theoretically the optical force exerted on a dielectric sph ere by the evanescent field of a Gaussian beam, where multiple scatter ing of light between the sphere and the prism substrate is considered. We derive first an expression of the nth order field (n greater than or equal to 1) that is scattered by the sphere and we then formulate t he optical force due to the scattered fields up to nth order. Numerica l results show that the effect of multiple scattering up to third orde r exerted on the optical force is within the extent of similar to 10% in resonance regions but it is negligible in off-resonance regions.