On the Influence of Earth's Rotation on Light Propagation in Waveguides

TL;DR

This paper investigates how Earth's rotation affects light propagation in optical waveguides, revealing weak mode coupling and anisotropic effects through Maxwell's equations and geometrical optics.

Contribution

It provides the first detailed calculation of Earth's rotation impact on electromagnetic modes in waveguides using perturbative methods.

Findings

Earth's rotation induces weak mode coupling in waveguides.

The correction to dispersion relations quantifies light anisotropy due to Earth's rotation.

Numerical agreement with geometrical optics approximation.

Abstract

We analyse the influence of Earth's rotation (both around its own axis and around the Sun) on the propagation of light in optical media. This is done using both geometrical optics and a perturbative calculation based on Maxwell's equations in rotating coordinates in flat spacetime. Considering light propagation in cylindrical step-index waveguides in particular, the first order correction to electromagnetic modes is computed. The calculation shows that Earth's rotation causes a weak mode coupling, giving rise to sidebands, whose amplitudes are computed as well. The correction to the dispersion relation derived here allows to assess the anisotropy of light propagation due to Earth's rotation. The linearisation of this result is found to agree numerically with a simple formula derived from geometrical optics.