Compact InGaAs/InP single-photon detector module with ultra-narrowband interference circuits

Gated InGaAs/InP avalanche photodiodes are the most practical device for detection of telecom single photons arriving at regular intervals. Here, we report the development of a compact single-photon detector (SPD) module measured just 8.8 × 6 × 2 cm 3 in size and fully integrated with driving signal generation, faint avalanche readout, and discrimination circuits as well as temperature regulation and compensation. The readout circuit employs our previously reported ultra-narrowband interference circuits (UNICs) to eliminate the capacitive response to the gating signal. We characterize a UNIC-SPD module with a 1.25-GHz clock input and find its performance comparable to its counterpart built upon discrete functional blocks. Setting its detection efficiency to 30% for 1,550-nm photons, we obtain an afterpulsing probability of 2.4% and a dark count probability of 8 × 10 −7 per gate under 3-ns hold-off time. We believe that UNIC-SPDs will be useful in important applications such as quantum key distribution.