arXiv subjects

Wei-Si Qiu

Publications and source records attributed to Wei-Si Qiu.

4 recordsLinked to original sources

arXiv2025

The Hall effects of vortex light in optical materials

For light, its spin can be independent of the spatial distribution of its wave function, whereas its intrinsic orbital angular momentum does depend on this distribution. This difference suggests that the spin Hall effect might differ from the orbital Hall effect as light propagates through optical materials. In this paper, we model optical materials as curved space-time and investigate light propagation in two specific materials by solving the covariant Maxwell equations. We find that the trajectory of light with spin $σ$ and intrinsic orbital angular momentum $\ell$ deviates from that of light without angular momentum ($σ=0$ and $\ell=0$) by an angle $θ_{σ,\ell} \propto 2σ+\ell$. In particular, the contribution of spin $σ$ to angle $θ_{σ,\ell}$ is twice that of the intrinsic orbital angular momentum $\ell$, highlighting their differing effects on light propagation in optical materials. Furthermore, this angle $θ_{σ,\ell}$ could potentially be observed experimentally, enhancing our understanding of the role of angular momentum in light propagation.

physics.optics↗

arXiv2024

Effective ray equations for vortex light and their application in an optical waveguide

Beyond its spin, light can also carry intrinsic orbital angular momentum (IOAM), termed as vortex light. In this study, we derive effective ray equations for vortex light by applying the WKB approximation to the covariant Maxwell equations. According to these equations, the propagation of vortex light can be significantly affected by its IOAM, as suggested by numerous studies. To examine the effects of IOAM, we solve the effective ray equations for vortex light and investigate its ray trajectory within a specific optical waveguide. Our findings indicate that the ray trajectory of vortex light exhibits a divergence perpendicular to the normal propagation plane, akin to the spin Hall effect in light. This divergence, termed as the orbital Hall effect, stems from the IOAM of the light. In this study, the effective ray equations are derived by modeling the interaction between light and media as light's free fall in a curved spacetime. Therefore, observing the orbital Hall effect could not only enhance our understanding of light's spin and IOAM, but also offer novel insights into the coupling between light and gravitational fields.

gr-qc↗

arXiv2024

Gravitational spin Hall effect of electrons in Schwarzschild metric

In this study, we derive the non-relativistic Hamiltonian for electrons within the Schwarzschild metric from covariant Dirac equations, using both the weak field approximation and the Foldy-Wouthuysen transformation. This Hamiltonian incorporates a gravitational spin-orbit coupling term, resulting in the gravitational spin Hall effect (SHE), which separates electrons by their spin. By solving the Schrödinger equation for these electrons, we investigate the gravitational SHE as they orbit a non-rotating gravitational source. Our findings reveal that the spin-dependent separation of electrons increases in proportion to their orbital periods, significantly improving the detectability of gravitational SHE. Specifically, for electrons in a low Earth orbit, the separation is estimated to be $3.0\times 10^{-12}\, \text{m}$ annually. These results indicate the practicality of detecting the gravitational SHE in electrons orbiting Earth, especially with prolonged orbital durations, underscoring the potential for quantum test of the Weak Equivalence Principle.

gr-qc↗

arXiv2024

Gravitational orbital Hall effect of vortex light in Lense-Thirring metric

Vortex light, characterized by an intrinsic orbital angular momentum aligned with its propagation direction, is described through vortex electromagnetic waves. Similar to the gravitational spin Hall effect (SHE), vortex light is expected to exhibit intrinsic orbital angular momentum dependent trajectories and deviations from the null geodesic plane when propagating through a gravitational field, a phenomenon termed the gravitational orbital Hall effect (OHE). In this work, we model the vortex light as vortex Laguerre-Gaussian electromagnetic wave packets and analyze its motion by solving covariant Maxwell equations within the Lense-Thirring metric. Our findings reveal that the trajectory of vortex light with an intrinsic orbital angular momentum deviates from the null geodesic in two ways. It deviates both perpendicular to, and within, the null geodesic plane. This behavior contrasts with the gravitational SHE, where spin-polarized light primarily deviates perpendicular to the null geodesic plane. Moreover, the relationship between the deviation and intrinsic orbital angular momentum differs significantly from that between the deviation and spin. These results suggest a unique interaction between intrinsic orbital angular momentum and gravity, distinct from the spin-gravity coupling, indicating that the gravitational OHE of light might not be precisely predicted by merely substituting spin with intrinsic orbital angular momentum in the gravitational SHE of light.

gr-qc↗