Optical Intensity Interferometry through Atmospheric Turbulence

TL;DR

This paper demonstrates that optical intensity interferometry can reliably measure solar photon bunching signals despite atmospheric turbulence, showing its robustness and potential for large baseline astronomical observations.

Contribution

It provides experimental evidence that intensity interferometry is unaffected by atmospheric turbulence, enabling high-precision measurements from ground-based or orbital platforms.

Findings

Photon bunching signal of g^{(2)}(τ) = 1.693 ± 0.003 measured from the Sun

Robustness of intensity interferometry against atmospheric turbulence demonstrated

Feasibility of long-baseline, long-integration measurements confirmed

Abstract

Conventional ground-based astronomical observations suffer from image distortion due to atmospheric turbulence. This can be minimized by choosing suitable geographic locations or adaptive optical techniques, and avoided altogether by using orbital platforms outside the atmosphere. One of the promises of optical intensity interferometry is its independence from atmospherically induced phase fluctuations. By performing narrowband spectral filtering on sunlight and conducting temporal intensity interferometry using actively quenched avalanche photon detectors (APDs), the Solar $g^{(2)}(\tau)$ signature was directly measured. We observe an averaged photon bunching signal of $g^{(2)}(\tau) = 1.693 \pm 0.003$ from the Sun, consistently throughout the day despite fluctuating weather conditions, cloud cover and elevation angle. This demonstrates the robustness of the intensity interferometry technique against atmospheric turbulence and opto-mechanical instabilities, and the feasibility to implement measurement schemes with both large baselines and long integration times.