PMTs were tested for DCR, efficiency, timing jitter and afterpulsing probability.
Various aspects of the detector construction are described and the methods adopted to calibrate in situ the efficiency, timing and positioning of the detector are presented.
Results from the PMT samples indicated small (but still significant) degradation in DCR and almost no degradation in any other measured property (efficiency, timing jitter, and afterpulsing probability) after applied radiation.
Other photon detection characteristics, such as photon detection efficiency, timing jitter, and afterpulsing probability, fluctuate but the overall performance of quantum communications should be largely unaffected by these variations.
Prior to irradiation, we measured the breakdown voltage, DCR, efficiency, timing jitter and afterpulsing probability of all APD samples at (-20^{circ}mbox{C}). Group 4 and the control group were also characterized at lower temperatures.
Laser annealing also affects other important photon counting parameters including photon detection efficiency, timing jitter, and afterpulsing probability, but the operation of quantum communications applications should not be significantly influenced by these changes.
Although most detection properties were preserved, including efficiency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-to-satellite quantum communications.
This permits to select a right trade-off between photon detection efficiency, timing resolution and dark count rate.
Open image in new window Fig. 10 The relationship between efficiency versus ignition timing.
Breakdown voltage, detection efficiency, afterpulsing and timing response jitter of all APDs demonstrated no notable change after thermal annealing.
