Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media

TL;DR

This paper experimentally demonstrates how circularly polarized light's spin angular momentum can be converted into orbital angular momentum through interaction with inhomogeneous, anisotropic media, enabling control over light's wavefront helicity.

Contribution

It introduces a novel optical process for spin-to-orbital angular momentum conversion using inhomogeneous anisotropic media, linked to Pancharatnam-Berry phases.

Findings

Successful experimental demonstration of spin-to-orbital angular momentum conversion.

Control over wavefront helicity via input polarization.

Identification of the role of geometrical phases in the process.

Abstract

We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wavefront helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization.