Poincaré sphere mapping of lateral optical forces on chiral particles

Optical lateral forces (OLFs) have broad applications in fields such as enantioselective sorting and sensing. However, the underlying mechanisms for generating and tailoring OLFs on chiral particles remain to be fully explored. In this study, we present a comprehensive analytical investigation of the physical origins of OLFs acting on chiral particles based on the dipole approximation theory. Unlike previous studies that focused primarily on a single light property, our analysis incorporates the roles of the electromagnetic chirality density gradient, the Poynting vector, its curl, and the magnetic spin angular momentum density. By tailoring the polarization state of the light field, we engineer OLFs on chiral particles in a line-focused optical field and find that circularly polarized light induces the maximum lateral force. Furthermore, analysis of particle size and refractive index reveals that left- and right-handed chiral particles exhibit opposite trends in optical force due to differences in their polarizabilities. Our work deepens the understanding of chiral light–matter interactions and provides an effective full-polarization strategy to engineer OLFs on chiral particles, which holds promise for enantioselective sorting and sensing.