On the Application of a Monolithic Array for Detecting Intensity-Correlated Photons Emitted by Different Source Types

TL;DR

This paper demonstrates how a monolithic 4x4 SPAD array, combined with an off-chip processing algorithm, effectively measures second-order photon correlations across various light sources, revealing effects inaccessible to single detectors.

Contribution

It introduces a novel off-chip algorithm for accurate g2 measurements using a monolithic SPAD array across diverse light fields.

Findings

Successful measurement of g2 in different light sources

Identification of detector background and afterpulsing effects

Enhanced access to otherwise unmeasurable photon correlation effects

Abstract

It is not widely appreciated that many subtleties are involved in the accurate measurement of intensity-correlated photons; even for the original experiments of Hanbury Brown and Twiss (HBT). Using a monolithic 4x4 array of single-photon avalanche diodes (SPADs), together with an off-chip algorithm for processing streaming data, we investigate the difficulties of measuring second-order photon correlations g2 in a wide variety of light fields that exhibit dramatically different correlation statistics: a multimode He-Ne laser, an incoherent intensity-modulated lamp-light source and a thermal light source. Our off-chip algorithm treats multiple photon-arrivals at pixel-array pairs, in any observation interval, with photon fluxes limited by detector saturation, in such a way that a correctly normalized g2 function is guaranteed. The impact of detector background correlations between SPAD pixels and afterpulsing effects on second-order coherence measurements is discussed. These results demonstrate that our monolithic SPAD array enables access to effects that are otherwise impossible to measure with stand-alone detectors.