All-Optical Chirality-Sensitive SortingviaReversible Lateral Forces in Interference Fields

Abstract

Separating substances by their chirality faces great challenges as well as opportunities in chemistry and biology. In this study, we propose an all-optical solution for passive sorting of chiral objects using chirality-dependent lateral optical forces induced by judiciously interfered fields. First, we investigate the optical forces when the chiral objects are situated in the interference field formed by two plane waves with arbitrary polarization states. When the plane waves are either linearly or circularly polarized, nonzero lateral forces are found at the particle's trapping positions, making such sideways motions observable. Although the lateral forces have different magnitudes on particles with different chirality, their directions are the same for opposite handedness particles, rendering it difficult to separate the chiral particles. We further solve the sorting problem by investigating more complicated polarization states. Finally, we achieve the chiral-selective separation by illuminating only one beam toward the chiral substance situated at an interface between two media, taking advantage of the native interference between the incident and reflective beams at the interface. Our study provides a robust and insightful approach to sort chiral substances and biomolecules with plausible optical setups.

Optical Enantioseparation of Racemic Emulsions of Chiral Microparticles

“…Despite ever-increasing theoretical efforts from many groups to establish the foundations of this challenging topic (see, e.g., Refs. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]), there are only a few experimental reports to date that deal with discriminatory effects for single chiral microparticles at a time [30][31][32][33][34][35].…”

Macroscopic direct observation of optical spin-dependent lateral forces and left-handed torques

“…Other situations where lateral forces appear have been proposed using purely optical schemes, by placing a spinning particle in the course of a light beam [21,22], or placing a particle in a inhomogeneous light field resulting two-wave interferences [23][24][25] or tightly focused vector beams [26]. Finally, we also mention many theoretical efforts to deploy spin-dependent lateral forces towards sorting material chirality by chiral light [27][28][29][30][31][32][33][34][35] soon after first experimental demonstrations restricted to the use of longitudinal forces [36,37]. That said, the study of lateral optical forces represents an attractive emerging research area with both fundamental and applied interests.…”

Enantioselective manipulation of single chiral nanoparticles using optical tweezers

“…To circumvent these limitations, optical enantioselective mechanisms have emerged as promising strategies to achieve contactless chiral resolution. Indeed, fostered by progresses in the field of plasmonics and metamaterials, many theoretical optical chiral resolution methods have been proposed [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and some of them have been experimentally realized [21][22][23][24][25][26]. However, due to the weak magnitude of optical forces, optical enantioselective meth- * r.ali@if.ufrj.br ods are typically limited to particles larger than proteins and molecules of biological and pharmaceutical interest.…”