Highly efficient singular surface plasmon generation by achiral apertures

TL;DR

This paper demonstrates a highly efficient method for generating singular surface plasmon fields using achiral $ ext{Lambda}$-shaped apertures, with tunable spin-orbit coupling and maximum extinction ratio, advancing nanophotonics applications.

Contribution

It introduces a novel achiral aperture design that significantly improves surface plasmon generation efficiency and tunability compared to previous methods.

Findings

A $ ext{Lambda}$-shaped aperture with a 60° apex angle achieves maximum extinction ratio.

The structure enables tunable spin-orbit coupling via aperture angle adjustment.

The method enhances SP focusing and vortex generation for nanophotonics applications.

Abstract

We report a highly efficient generation of singular surface plasmon (SP) field by an achiral plasmonic structure consisting of $\Lambda$-shaped apertures. Our quantitative analysis based on leakage radiation microscopy (LRM) demonstrates that the induced spin-orbit coupling can be tuned by adjusting the apex angle of the $\Lambda$-shaped aperture. Specifically, the array of $\Lambda$-shaped apertures with the apex angle $60^\circ$ is shown to give rise to the directional coupling efficiency. The ring of $\Lambda$-shaped apertures with the apex angle $60^\circ$ realized to generate the maximum extinction ratio (ER=11) for the SP singularities between two different polarization states. This result provides a more efficient way for developing SP focusing and SP vortex in the field of nanophotonics such as optical tweezers.