Optical enantiomer sorting via background-particle electromagnetic matching

The performance of all-optical chirality-sorting systems is fundamentally governed by the competition between enantioselective chiral optical forces and non-discriminatory non-chiral forces. In this Letter, we demonstrate a background-particle electromagnetic matching approach, in contrast to light-field-tailoring methods, by immersing chiral particles in a medium with matched permittivity. Both analytical expressions and numerical simulations demonstrate that the electromagnetic-matching approach can generate a dominant chiral optical force that surpasses non-chiral ones, while preserving sufficiently strong force magnitudes to enable effective enantiomer separation. Dynamic simulations in standard optical tweezers further confirm efficient chiral sorting across a broad range of particle sizes and chiral strengths, even when employing a near-matching background medium, broadening the applicability of optical enantiomer separation.