Ultrasensitive mid-infrared up-conversion imaging at few-photon level

We demonstrated few-photon-level mid-infrared imaging at 3.39 mu m by efficient frequency up-conversion. The quantum frequency up-conversion efficiency of mid-infrared photons was high to 32.9%, while mid-infrared images were up-converted with the quantum efficiency of 12.5%. The mid-infrared imaging sensitivity was improved by counting the frequency up-conversion photons temporally confined within the time-window of the pump pulse. The frequency up-conversion system induced a background noise of 1.1 x 10(3) counts per second. (C) 2013 AIP Publishing LLC.