Development of a Digital Astronomical Intensity Interferometer: laboratory tests with thermal light

TL;DR

This paper demonstrates a digital intensity interferometer setup using Hanbury-Brown and Twiss interferometry to measure spatial coherence of thermal light, with potential applications in astronomical imaging.

Contribution

It introduces a digital correlator approach for intensity interferometry and shows how polarization and detector separation affect measurements, enhancing astronomical observation techniques.

Findings

Uncorrelated intensity fluctuations at orthogonal polarizations

Reduced systematic noise through polarization and separation strategies

Applicable to existing and future astronomical telescopes

Abstract

We present measurements of the second order spatial coherence function of thermal light sources using Hanbury-Brown and Twiss interferometry with a digital correlator. We demonstrate that intensity fluctuations between orthogonal polarizations, or at detector separations greater than the spatial coherence length of the source, are uncorrelated but can be used to reduce systematic noise. The work performed here can readily be applied to existing and future Imaging Air-Cherenkov Telescopes used as star light collectors for Stellar Intensity Interferometry (SII) to measure spatial properties of astronomical objects.