Sub-Rayleigh Imaging via N-Photon Detection

Abstract

The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam—in an arbitrary, object-covering pattern that is unknown to the imager—and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ∼(N-N̅ [subscript max])1/2 beyond the Rayleigh bound, where N̅ [subscript max] is the maximum average detected photon number in the image, in good agreement with theory.