Multipole Engineering of Optical Forces

In most cases, the smallest particles are subjected to forces of attraction and repulsion due to the gradient and radiation pressure. The use of additional degrees of freedom in optomechanical manipulations opens up new possibilities. In this work, we investigate the optical forces acting on a high refractive index silicon sphere in a focused Gaussian beam. Analysis of multipolarity allows us to separate the optical force into trapping and scattering components, which have different physical nature and result in different mechanical effects. These effects are associated with multipolar interference and asymmetric far-field scattering patterns. Such an approach is useful for understanding optomechanical motion and its regularities in the far-field zone. Multipolar engineering of optical forces, not limited to spherical shapes, opens up new possibilities in microfluidic applications, including sorting and assembly of complex volumetric geometries. #COMESYSO1120.