The orbital angular momentum of a turbulent atmosphere and its impact on propagating structured light fields

TL;DR

This paper investigates how atmospheric turbulence affects the orbital angular momentum (OAM) of light by analyzing the atmosphere's own OAM, providing new physical insights and confirming findings experimentally.

Contribution

It introduces a novel approach by calculating the atmosphere's OAM to understand its impact on structured light, offering a new perspective beyond traditional beam-focused models.

Findings

Atmospheric turbulence imparts measurable OAM to the atmosphere itself.

Experimental confirmation supports the theoretical model.

The approach can be extended to other structured light fields.

Abstract

When structured light is propagated through the atmosphere, turbulence results in modal scattering and distortions. An extensively studied example is that of light carrying orbital angular momentum (OAM), where the atmosphere is treated as a phase distortion and numerical tools extract the resulting modal cross-talk. This approach focuses on the light itself, perturbed by the atmosphere, yet does not easily lend itself to physical insights, and fails to ask a pertinent question: where did the OAM that the beam gained or lost come from? Here, we address this by forgoing the beam and instead calculating the OAM of the atmosphere itself. With this intuitive model we are able to draw general conclusions on the impact of atmospheric turbulence on OAM beams, which we confirm experimentally. Our work alters the perspective on this problem, opening new insights into the physics of OAM in turbulence, and is easily extended to other structured light fields through arbitrary aberrations.