Chirality sorting with 3D-arbitrarily-oriented circularly polarized ultra-long optical needle field

We propose an all-optical sorting method for chiral nanoparticles by use of a 3D-arbitrarily-oriented circularly polarized ultra-long optical needle field, which is constructed through reversing the radiation patterns from an array of spin dipole located in the focal volume of a 4Pi microscopy. It is demonstrated that particles with different chirality can be trapped at different positions along the optical needle by the chiral gradient force, and the direction and distance of sorting are determined by the orientation and length of the circularly polarized optical needle respectively, which can be easily controlled by modifying the quantity and orientation of the equivalent spin dipoles. This scheme combines the advantages of controllable sorting direction and long sorting distance, providing a feasible route toward all-optical enantiopure chemical syntheses and enantiomer separations in pharmaceuticals.