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Description
Stellar Intensity Interferometry (SII) is undergoing a major revival [1,2], yet its sensitivity remains bound by the performance of traditional photon counters. For SII in 500-700 nm range, standard avalanche photodiodes (APDs) enjoy a relatively high quantum efficiency but suffer from timing jitter, which directly affects the measurable second-order correlation.
In this work, we present the laboratory implementation of a 4-pixel Superconducting Nanowire Single-Photon Detector (SNSPD) system [3] as a next-generation technology for SII. SNSPDs bring a combination of ultralow timing jitter, reduced dark counts, and negligible afterpulsing. In our architecture, each pixel is a 100-nm width nanowire meander of ~50 × 50 µm², read out independently and combined into a single logical channel with picosecond-level delay corrections. This design simultaneously boosts count rate while fully preserving the intrinsic timing resolution of each pixel.
To evaluate the system, we developed a 100-µm-core multimode fiber-coupled Hanbury Brown and Twiss interferometer with a thermal light source. Benchmarked against conventional APDs, the 4-pixel SNSPD array delivers a correlation peak width (FWHM) of 113 ps, with improved SNR, 4 times better contrast and no measurable afterpulsing, while maintaining comparable detection efficiency.
These results establish multi-pixel SNSPDs as a foundational architecture for the next generation of high-sensitivity SII instruments.
References
[1] R. Hanbury Brown and R. Q. Twiss, Nature 177, 27 (1956).
[2] W. Guerin, et al., Comptes Rendus Physique 26, 659 (2025).
[3] I. Esmaeil Zadeh, et al., Appl. Phys. Lett. 118, 190502 (2021).
