Spin-orbit interactions of light

TL;DR

This paper reviews the fundamental origins and applications of spin-orbit interactions in light, highlighting their significance in modern nano-optics, photonics, and plasmonics at subwavelength scales.

Contribution

It provides a comprehensive overview of spin-orbit interaction phenomena in optics, including effects at interfaces, in nonparaxial fields, and via structured interfaces like metasurfaces.

Findings

Spin-orbit interactions are fundamental in all basic optical processes.

They enable spin-dependent effects in inhomogeneous media.

Spin-orbit effects are crucial at subwavelength scales in modern optics.

Abstract

Light carries spin and orbital angular momentum. These dynamical properties are determined by the polarization and spatial degrees of freedom of light. Modern nano-optics, photonics, and plasmonics, tend to explore subwavelength scales and additional degrees of freedom of structured, i.e., spatially-inhomogeneous, optical fields. In such fields, spin and orbital properties become strongly coupled with each other. We overview the fundamental origins and important applications of the main spin-orbit interaction phenomena in optics. These include: spin-Hall effects in inhomogeneous media and at optical interfaces, spin-dependent effects in nonparaxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces), as well as robust spin-directional coupling via evanescent near fields. We show that spin-orbit interactions are inherent in all basic optical processes, and they play a crucial role at subwavelength scales and structures in modern optics.