Chirality sorting using two-wave-interference–induced lateral optical force

We demonstrate that a lateral optical force (LOF) can be induced on chiral nanoparticles immersed in the two interfering plane waves. The LOF can push the chiral nanoparticle sideways, in the direction relying on the helicity of the particle as well as the phase difference between two waves. Analytical theory reveals that the LOF comes mostly from the direct coupling of the optical vorticity with the particle chirality. In particular, the LOF has a magnitude comparable to the gradient force and radiation pressure when the particle chirality is sufficiently large. The LOF may serve for chirality sorting due to its unusual properties and also provide an opportunity for passive chiral spectroscopy.