Spin-orbit interaction of light and diffraction of polarized beams

TL;DR

This paper theoretically investigates how the spin-orbit interaction of light influences the diffraction pattern of polarized beams, revealing polarization-dependent deviations and internal energy flows in the diffracted light.

Contribution

It introduces a theoretical analysis of spin-orbit interaction effects in edge diffraction of polarized light beams, highlighting polarization-dependent beam deviations and internal energy flow characteristics.

Findings

Circular polarization causes a small angular deviation in the diffracted beam's center of gravity.

The deviation direction depends on the polarization handedness.

The effect reveals the vortex nature of the longitudinal field component.

Abstract

The edge diffraction of a homogeneously polarized light beam is studied theoretically based on the paraxial optics and Fresnel-Kirchhoff approximation, and the dependence of the diffracted beam pattern of the incident beam polarization is predicted. If the incident beam is circularly polarized, the trajectory of the diffracted beam centre of gravity experiences a small angular deviation from the geometrically expected direction. The deviation is parallel to the screen edge and reverses the sign with the polarization handedness; it is explicitly calculated for the case of a Gaussian incident beam with plane wavefront. This effect is a manifestation of the spin-orbit interaction of light and can be interpreted as a revelation of the internal spin energy flow immanent in circularly polarized beams. It also exposes the vortex character of the weak longitudinal field component associated with the circularly polarized incident beam.