Quantifying the advantage of photon correlation microscopy using arrays of single-photon detectors

Correlation microscopy is an emerging technique for improving optical resolution. By taking advantage of the photon statistics from single-photon fluorophores, more information about the emitters (including number and location) is obtained compared with classical microscopy. Although it is known that the resolution can be improved by increasing detector numbers, as well as using photon correlations, the quantitative relationship between these two approaches is not immediately clear. Here we explore widefield photon correlation microscopy using arrays of single-photon detectors. We explicitly compare the use of N detectors used in photon counting mode vs N/2 detectors used to measure photon correlations. i.e., where there are N/2 Hanbury Brown and Twiss systems, using the same N detectors, on randomly generated two-emitter systems and triangular three-emitter systems. We find regimes where N/2 Hanbury Brown and Twiss detectors provide improved localisation compared to N photon counting detectors, as a function of emitter position and number of photons sampled.