  Niobium Nitride (NbN) nanowire is the most popular detection material of
superconducting nanowire single photon detectors (SNSPDs) for high repetition
rate and high efficiency. However, it has been assumed to be difficult for
fabricating SNSPDs with arrays over large area, which are critical components
of quantum imaging, linear optical quantum computing, satellite laser ranging,
and high-speed quantum key distribution. This paper reported a 4*4 pixel NbN
SNSPDs array with an equivalent receiving aperture of 300 micrometer associated
with beam compression technology, which is the first NbN SNSPD coupled by 300
micrometer fiber according to our knowledge. The designed pixel was compact
with a filling factor of 98.5%, resulting in a high quantum efficiency of
94.5%, a system efficiency of 46% for photons coupled from 300 micrometer fiber
without optimizing polarization, and a system time resolution of 92 ps. This
work demonstrates the feasibility of a large SNSPDs array, and paves the way
for developing efficient photon camera with NbN nanowires.
