Niobium nitride(NbN) nanowires are commonly used as photosensitive materials for superconducting nanowire single-photon detectors(SNSPDs). Their optical properties are the key factors influencing the performance of SNSPD.According to the experimental data and simulation results, in this paper we systematically study the optical properties of various niobium nitride nanowire detector device structures, and characterize the reflection spectra and transmission spectra of the following four device structures: 1...