Detection efficiency measurement of an up-conversion single-photon detector at 3.39μm based on SPDC

Up-conversion single-photon detector (UCSPD) is promising in weak light radiometry at mid-infrared spectrum. This paper proposed a method to measure the detection efficiency of UCSPD at 3.39μm based on the visible-infrared correlated photons generated by spontaneous parametric down-conversion (SPDC). No infrared standard light source or standard detector was used in measurement and calibration result was insensitive to ambient thermal radiation. An experimental facility was established to obtained a detection efficiency of 0.0085 with a relative uncertainty of 2.8% (k = 1). Factors affecting measuring uncertainty were analyzed and corrected. Bandwidth matching between trigger channel and channel under test is a key problem in detection efficiency calibration. By measuring the bandwidth of the trigger channel and analyzing the bandwidth of the optical elements in the channel under test, we confirm that the acceptance bandwidth of up-conversion crystal is the narrowest. The two channels meet the bandwidth matching conditions, and the detection efficiency can be obtained directly without the bandwidth correction algorithm. Measured detection efficiency agreed well with the result obtained by a continuous laser measurement facility within a difference about 4.7%.