Optically active beams: non-reciprocal optical activity in free space induced by spin-orbital interaction of light

TL;DR

This paper demonstrates that free space can support non-reciprocal optical activity using Bessel beams and spin-orbital interaction, enabling media-independent optical components like rotators and isolators.

Contribution

It experimentally shows free-space non-reciprocal optical activity induced by spin-orbital interaction, expanding the understanding of optical activity beyond chiral media.

Findings

Realization of non-diffractive optically active beams in free space

Optical rotatory power controlled by simple optical elements

Potential for media-independent optical components

Abstract

Optical activity, the power of a medium to rotate the polarization of a light beam, has contributed significantly to molecular structure assessments in stereochemistry, biomolecular science and crystallography. Thus far, it is commonly believed that optical activity is manifested only in the chiral media which can give rise to circular birefringence of light. Here, we experimentally demonstrate that free space can also support the implementation of non-reciprocal optical activity with Bessel beams by spin-orbital interaction. Specifically, non-diffractive optically active beams are realized, with their optical rotatory power readily controlled by simple optical elements. We show that such free-space optical activity can be exploited to form non-reciprocal optical components such as polarization rotators, isolators, and circulators. Our results may bring about new possibilities of media-independent optical activity to other transverse waves ranging from radio to optical frequencies.