Light carrying photon momentum can push and pull microparticles through momentum exchange. This momentum exchange process generates optical forces, which either attracts (conventional optical tweezers), pushes (radiation force) or pulls (pulling force) microparticles. A new emerging research interest, optical lateral force which represents the optical force perpendicular to the propagating direction of a non-gradient beam, has attracted much attention. The lateral force can be generated using achiral particles through the conversion of spin and orbital momentum of a circularly polarized beam. It is also predicted that a chiral nanoparticle placed above a surface can generate the lateral force using a plane wave excitation. However, there are few demonstrations of the chirality dependent lateral force, and the particles used in the theoretical prediction are 100 nm which has limited applications. Besides, the theory of optical lateral force on bigger particles (size ~ wavelength) is lacking.
Click here for original story, Chirality-assisted lateral momentum transfer for bidirectional enantioselective separation
Source: Phys.org