High-sensitivity weak light detector

The utility model discloses a high-sensitivity weak light detector. The device specifically comprises a shell, a semiconductor cooler, a single photon avalanche photodiode assembly, a heat sink, a coupling lens group and an optical fiber, the optical fiber, the coupling lens group and the single photon avalanche photodiode chip are sequentially connected and fixed on the heat sink, and the heat sink is assembled on the cold end face of the semiconductor cooler; the coupling lens group is used for focusing an emergent light signal in the optical fiber and transmitting the emergent light signal to the single-photon avalanche photodiode chip, and the single-photon avalanche photodiode chip is used for converting light information into an electric signal; and the semiconductor cooler is used for cooling devices assembled on the semiconductor cold surface. Compared with a traditional method, the single photon avalanche photodiode chip has the advantages that the coupling lens group is additionally arranged, so tha