Detector calibration at INM using a correlated photons source

The correlated photons source is obtained from the parametric down conversion of photons generated in a non linear crystal. When associated with a system of coincidences counting, this source allows one to measure the detection efficiencies of detectors working at photon counting levels, without the need for reference sources or detectors. At the Institut National de Métrologie (France), this method was implemented with the aim of realising a new standard detector for the absolute measurement of very weak radiations. The relative standard uncertainty of the detection efficiency measurements is 1.1%.