Characteristics of surface plasmon polaritons in a dielectrically chiral-metal-chiral waveguiding structure

Arbitrary-order three-point finite difference method for the modal analysis of chiral waveguides

A three-point finite difference method with an arbitrary order of accuracy is proposed for the modal analysis of chiral planar waveguides. The elaborate application of a nonuniform grid, compact finite difference technique, and boundary conditions results in an efficient, easily implemented, and versatile tool for the modal analysis of chiral planar waveguides with an arbitrarily discontinuous profile of permittivity, permeability, and chirality. In particular, this method efficiently resolves the fine structures in plasmon and photonic crystal waveguides. For the test model of a chiral-metallic plasmon waveguide, stable convergence up to a sixteenth order of accuracy can be obtained, which produces a relative error on the effective index that approaches the machine precision with only eighty grid points.

Behavior of SPPs in chiral-graphene-chiral structure

In this Letter, considering the chiral-graphene-chiral structure, we investigate the more universal dispersion relation covering the achiral cases, the effect of the chirality of a medium, and the chemical potential of graphene on the behavior of graphene surface plasmon polaritons (GSPPs) and transverse spin density, which is key to understanding the lateral optical force. This research is dedicated to looking for a regulating mechanism based on chirality and graphene to apply in devices of information processing and biosensor for identifying molecular chirality. We found the averaging effect of chirality in both sides of graphene in tuning the behavior of GSPPs. We believe this work can make contributions to enrich SPP theory and benefit the development of novel detection techniques for chiral molecules based on graphene.

Optical lateral forces and torques induced by chiral surface-plasmon-polaritons and their potential applications in recognition and separation of chiral enantiomers

Surface plasmon polaritons carry an intrinsic transverse spin angular momentum which is locked to their propagation direction due to the quantum spin Hall effect of light. We study the chirality-sorting lateral optical forces arising from this phenomenon in a Kretschmann configuration. We show that the characteristics of surface plasmon polaritons are affected by small changes of the environment's chirality. This property can be utilized to detect the medium's chirality in the macro-world. Furthermore, we explain how the the lateral forces and optical torques interact with the chirality of nano-particles located or adsorbed in the vicinity of the surface in the micro-world. Finally, we demonstrate that introducing one handedness of chirality to the dielectric medium in the Kretschmann configuration will benefit the discrimination of chiral enantiomers compared with the nonchiral case. Our work presents physical insights into chirality-selective lateral forces using surface plasmon polaritons and provides a new approach to discriminating and separating chiral enantiomers in the chemical and pharmaceutical industries.