Chiral lateral optical force near plasmonic ring induced by Laguerre–Gaussian beam

Abstract

Owing to the good adjustability and the strong near-field enhancement, surface plasmons are widely used in optical force trap, thus the optical force trap can achieve excellent performance. Here, we use the Laguerre–Gaussian beam and a plasmonic gold ring to separate enantiomers by the chiral optical force. Along with the radial optical force that traps the particles, there is also a chirality-sign-sensitive lateral force arising from the optical spin angular momentum, which is caused by the interaction between optical orbit angular momentum and gold ring structure. By selecting a specific incident wavelength, the strong angular scattering and non-chiral related azimuthal optical force can be suppressed. Thus the chiral related azimuthal optical force can induce an opposite orbital rotation of the trapped particles with chirality of different sign near the gold ring. This work proposes an effective approach for catchingand separating chiral enantiomers.