arXiv subjects

Zhi-Juan Hu

Publications and source records attributed to Zhi-Juan Hu.

4 recordsLinked to original sources

arXiv2025

Revisiting optical rotation in helically-coiled fibers

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.

physics.optics↗

arXiv2023

Stokes parameters alone cannot completely characterize the polarization of plane light waves

It was generally assumed that the Stokes parameters are complete characterization for the state of polarization of a plane light wave so that their counterparts in quantum optics, called the Stokes operators, represent the polarization of photons. Here we show, through analyzing the properties of polarized plane waves in an optically active medium, that the Stokes parameters are not able to completely characterize the state of polarization of a plane wave. The key point is that only when a plane wave is expanded in terms of the orthogonal base modes, which are physically meaningful, can the two expansion coefficients make up the Jones vector. Taking this into consideration, we demonstrate that the Stokes parameters of any elliptically polarized wave in an isotropic chiral medium, determined solely by its Jones vector, are transmitted unchanged. They are not able to reflect the rotation of its polarization ellipse along with the propagation. The relationship of the Stokes parameters with the polarization of light needs further investigation.

physics.optics↗

arXiv2022

On a heuristic point of view concerning the optical activity

Motivated by a recent finding that Fresnel's phenomenological description of the optical activity in the chiral medium is not self-consistent, we conduct a thorough investigation into the nature of the polarization of a plane light wave. We demonstrate that the polarization of light is the reflection of one of its quantum-mechanical properties, called the quasi-spin. Unexpectedly, the quasi-spin is not an observable with respect to the laboratory coordinate system. Instead, it is with respect to the momentum-dependent local coordinate system. The representative operators for the quasi-spin are the Pauli matrices. The wavefunction is the Jones vector. In order to completely determine a state of polarization, two different kinds of degrees of freedom are needed. One is the degrees of freedom to characterize the state of quasi-spin. They are the Stokes parameters, the expectation values of the Pauli matrices in the state described by the Jones vector. The other is the degrees of freedom to specify the local coordinate system, including the propagation direction and an angle of rotation about it. Accordingly, there are two independent mechanisms to change the state of polarization. One is to change the state of quasi-spin in a fixed local coordinate system. This is the traditional mechanism that can be expressed as an SU(2) rotation of the Jones vector. The other is to change the local coordinate system with the state of quasi-spin remaining fixed in it. At last, we show that it is the newly-identified mechanism that accounts for the optical activity.

physics.optics↗

arXiv2022

No circular birefringence in a chiral medium: an analysis of single-mode refraction

It is generally believed that the right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) waves in an isotropic chiral medium propagate at different velocities, known as circular birefringence. Here we show that this is not the case. After obtaining the refraction and reflection coefficients of any elliptically polarized wave at the surface of a chiral medium, we derive the conditions for single-mode refraction. By means of the process of single-mode refraction, we demonstrate that both the refracted RCP and the refracted LCP waves at normal incidence can be expressed as a coherent superposition of a pair of orthogonal linearly polarized waves that are rotated simultaneously. As a result, they must propagate at the same velocity as the linearly polarized waves. A physical interpretation is also given in detail. In particular, we show that the state of polarization of any elliptically polarized wave in a chiral medium is rotated with propagation. Such a rotation amounts to the rotation of polarization bases without involving the change of the Jones vector. The rotation of the RCP and LCP waves, as special cases of elliptically polarized waves, results in two opposite phases as if they propagated at different phase velocities with their polarization states transmitted unchanged.

physics.optics↗