Spin-orbit Interaction-mediated Measurement of Surface Chirality

TL;DR

This paper demonstrates how spin-orbit interaction in light beams can be used to measure the surface chirality of materials by analyzing vortex transformations influenced by polarization and reflection.

Contribution

It introduces a novel optical method utilizing vortex trajectories to quantify surface chirality, validated through simulations and experiments.

Findings

Chirality-dependent vortex transformations observed

Optical vortex trajectory correlates with surface chirality

Method accurately measures chiral parameter of quartz

Abstract

The spin-orbit interaction in a focused-reflected beam of light results in spatially non-uniform polarization in the beam cross-section due to the superposition of orthogonal field components and polarization-dependent interface reflection coefficients. Polarization filtering the output beam leads to an interchangeable transformation of - or + 2 charge vortex into two - or + unit charge vortices, for + or - circular polarization of the input Gaussian beam. This transformation follows a trajectory, named optical vortex trajectory, that depend on the input beam spin and hence the vortex charge and reflecting surface characteristics. The OVT is used here to quantify both the sign and the magnitude of the chiral parameter of a quartz crystal. The Jones matrix-based simulation anticipates the chirality-dependent OVT that matches with experimental measurements.