Multipole Engineering of Attractive?Repulsive and Bending Optical Forces

Focused laser beams allow controlling the mechanical motion of objects and can serve as a tool for assembling micro nanostructures in space. While small particles mainly experience attractive gradient forces repulsive radiation pressure, introducing additional flexibility suggests approaching new capabilities. Herein, optical acting on high refractive index sphere focused Gaussian beam are analyzed regimes revealed. Multipolar analysis allows separating an force into interception recoil components, resulting different actions. In particular, interplaying radial multipolar resonances within particle lead to either trapping or antitrapping, depending system parameters. At same time, generates significant azimuthal component along with angular-dependent force. Those contributions enable enhancing antitrapping also introduce bending reactions. These effects linked far-field multipole interference and, specifically, asymmetric scattering patterns. The latter approach is extremely useful, it assessing nature optomechanical by observing far-fields. engineering forces, being quite general approach, not necessarily simple spherical shapes paves way possibilities microfluidic applications, including sorting microassembly.