Plasmonic trapping of sub-micro objects with metallic antennae

Abstract

Since optical trapping was first reported, its methods and targets have been broadened. In this paper, we propose ‘plasmonic clipping’, which traps objects on the plasmonic dot array. Localized surface plasmon polaritons (LSPPs), which localize optical energy in the nanometer-scale size and enhances the optical field, are excited in gaps between the dots. The objects are trapped by electric-field-gradient forces of LSPPs along the dot array. The dot arrays are arranged radially so that LSPPs are selectively excited in dot array corresponding to polarization direction of excitation light. The selective excitation results in directionally-selective ‘plasmonic clipping’. The radial dot arrays made of silver are numerically designed and fabricated by means of a focused ion beam (FIB). The arrays are illuminated with laser beam through the half wavelength plate to rotate polarization direction. As a result, the plasmonic clipping is observed along the array corresponding to polarization of the excitation light. It is expected to be utilized to align functional components for manufacturing, measurement, and material technologies.