Sub-Rayleigh imaging via N-photon detection

Phys Rev Lett. 2010 Oct 15;105(16):163602. doi: 10.1103/PhysRevLett.105.163602. Epub 2010 Oct 14.


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-N(max))(½) beyond the Rayleigh bound, where N(max) is the maximum average detected photon number in the image, in good agreement with theory.