Strong tangential force within a small trapping volume under near-field Laguerre-Gaussian beam illumination

Near-field rotation of a trapped particle under focused evanescent Laguerre-Gaussian beam illumination is theoretically investigated by mapping the two-dimensional transverse trapping efficiency exerting on the particle. It is revealed that the severe focal field deformation associated with a focused evanescent Laguerre-Gaussian beam causes a significant impact on the transverse trapping performance of the microparticle. Compared with the far-field trapping force, strong tangential force components have been observed in the transverse efficiency mapping, which potentially lead to rotational motions to the particle within a small trapping volume in the optical near-field.