Lateral optical force along the translationally invariant direction of optical fields formed by circularly polarized plane waves

Based on the generalized Lorenz-Mie method and Maxwell stress tensor theory, we demonstrate that a lateral optical force (OF) can be induced on a spherical particle along the translationally invariant direction of incident optical fields formed by multiple circularly polarized plane waves. It is analytically shown that the lateral OF depends on two quantities associated with the illuminating field, regardless of the particle properties such as material composition and particle size. Interestingly, for some special cases like two- or three-wave interference field, the lateral OF is rigorously proportional to the Poynting vector. As examples, the numerical results for the interference field composed of two or three circular polarized plane waves show that the spatial distribution pattern of the lateral OF is always determined by Poynting vectors of the illuminating field itself, while the particle size and material affect solely the magnitude but not the spatial profile of the lateral OF. In addition, the magnitude of the lateral OF is comparable to other components of the OF. The lateral OF is traced to the scattering force due to the interference between multipoles excited on the particle. These findings may enrich the concept of the lateral OF and also add an additional implement to the optical manipulation toolbox.