The Role of Spatial Coherence and Orbital Angular Momentum of Light in Astronomy

TL;DR

This paper investigates how the orbital angular momentum of light can be used in astronomy, especially considering the effects of spatial coherence reduction, with experimental and theoretical insights into observational challenges.

Contribution

It introduces a simple model predicting how reduced spatial coherence affects OAM measurements in astronomical observations, supported by lab experiments.

Findings

OAM spectrum depends on the position of the light-twisting object

Reduced spatial coherence significantly influences OAM detection

The developed model predicts observational effects of spatial coherence reduction

Abstract

The orbital angular momentum (OAM) of light is potentially interesting for astronomical study of rotating objects such as black holes, but the effect of reduced spatial coherence of astronomical light sources such as stars is largely unknown. In a lab-scale experiment, we find that the detected OAM spectrum depends strongly on the position of the light-twisting object along the line of sight. We develop a simple intuitive model to predict the influence of reduced spatial coherence in astronomical observations, and discuss line-of-sight and intensity issues.