  Generally, a superconducting nanowire single-photon detector (SNSPD) is
composed of wires with a typical width of ~100 nm. Recent studies have found
that superconducting strips with a micrometer-scale width can also detect
single photons. Compared with the SNSPD, the superconducting microstrip
single-photon detector (SMSPD) has smaller kinetic inductance, higher working
current, and lower requirement in fabrication accuracy, providing potential
applications in the development of ultra-large active area detectors. However,
the study on SMSPD is still in its infancy, and the realization of its
high-performance and practical use remains an opening question. This study
demonstrates a NbN SMSPD with a saturated system detection efficiency (SDE) of
~92.2% at a dark count rate of ~200 cps, a polarization sensitivity of ~1.03,
and a minimum timing jitter of ~48 ps, at the telecom wavelength of 1550 nm
when coupled with a single mode fiber and operated at 0.84 K. Furthermore, the
detector's SDE is over 70% when operated at a 2.1-K closed-cycle cryocooler.
