Spin-Orbit Interaction of Light Enabled by Negative Coupling in High Quality Factor Optical Metasurfaces

TL;DR

This paper demonstrates how negative coupling in high-Q optical metasurfaces induces pseudo-spin-orbit interactions, creating circularly polarized eigenstates and enabling spin-selective light control with potential applications in sensing and nonlinear optics.

Contribution

It introduces a novel theoretical model showing pseudo-spin-orbit coupling in 2D metasurfaces with high-Q resonances and Type-II non-Hermitian points, expanding the understanding of light-matter interactions.

Findings

Discovery of pseudo-spin-orbit coupled bulk modes in 2D metasurfaces

Existence of circular polarization lines in momentum space

Spin-selective light deflections enabled by the metasurface

Abstract

We study the negative couplings amid local resonances of photonic metasurfaces. In our analysis, we discover pseudo-spin-orbit coupled bulk modes leading to lines of circularly polarized radiation eigenstates in two-dimensional momentum space which were considered to exist only in three-dimensions. Our theoretical model is exemplified via a guided resonance dielectric metasurface that possesses Type-II Non-Hermitian diabolical points, from where the circular polarization lines emanate. The designed metasurface carries circular polarized radiation eigenstates in both the 0th and the 1st diffraction orders, allowing spin-selective light deflections. The high quality factor nature and field enhancement of the designed metasurface could lead to applications for spin-selective sensing, beam control and nonlinear optics. Our findings open a gateway for the design of near-field couplings assisted metasurfaces.