Absolute self-calibration of the quantum efficiency of single-photon detectors
单光子探测器量子效率的绝对自身标定方法

An absolute self-calibration method is proposed for determining the quantum efficiency of a single photon detector which does not require any standard referenc e or a second detector. The method is based on the time correlation of photon pa irs generated in parametric downconversion. A beam of frequency downconverted ph otons is split at a polarizing beamsplitter then recombined at a second beamspli tter, but with a time delay introduced between them so that the two photons of a n original pair enter the detector one by one. The photoelectric pulses from the detector are split into three paths; a compensating delay is introduced into tw o of the paths so that the two signals arrive simultaneously at a coincidence co unter; the third path goes directly to a photon counter. From the ratio of the r eadings of the two counters we can derive the quantum efficiency of the detector . Two methods are given, one for continuous wave lasers and another for high rep etition rate pulsed lasers.