Imaging at the Single-Photon Limit Using Homodyne Detection

Imaging at the level of single photons is crucial in many application areas but, due detector technology, is largely restricted to the visible region of the spectrum. We present a full-field homodyne imaging system capable of imaging in the single-photon per image pixel regime operating in the short-wave infrared, despite the camera used having a noise floor $\approx 200$ times higher. This approach is inspired by Gabor's “Observation without Illumination” paradox ¹ and whilst having much in common with holographic interference microscopes ² , our approach extends the range of applications of low-light imaging, in biological, medical, and potentially covert imaging.