Revisiting optical rotation in helically-coiled fibers

TL;DR

This paper challenges the traditional interpretation of optical rotation in optically active media and helically-coiled fibers, arguing that circular birefringence is a fallacy and that polarization rotation is due to frame rotation, not birefringence.

Contribution

It provides a logical proof that helically coiled fibers do not exhibit circular birefringence and clarifies the geometric origin of optical rotation in such fibers.

Findings

Optical rotation in chiral media is not due to circular birefringence.

Helically coiled fibers do not exhibit circular birefringence.

Observed rotation reflects rotation of the local reference frame, not birefringence.

Abstract

The interpretation of optical rotation in optically active media as circular birefringence has persisted for over two centuries, yet the inherent fallacy in this phenomenological theory remains unnoticed. Recently, we employed logical reasoning to demonstrate that isotropic chiral media, a kind of optically active media, do not exhibit circular birefringence. This finding implies that the Jones vector is not able to completely describe the polarization state of a plane light wave. To further explore the reason, here we revisit the phenomenon of optical rotation in helically-coiled optical fibers. Firstly, we use similar logical reasoning to prove that helically coiled fibers do not exhibit circular birefringence, either. Secondly, based on the experimental observations of Papp and Harms, we argue that the Jones vector is mathematically an entity in the local reference frame associated with the propagation direction. It cannot completely describe the state of polarization relative to the laboratory reference frame. Meanwhile, we also demonstrate that the rotation observed by Papp and Harms reflects the rotation of the Tang frame relative to the Serret-Frenet frame.