Superconducting nanowire single-photon detector with polarization insensitivity, ultrafast response, and high efficiency.

This study proposed what we believe to be a novel method for fabricating superconducting nanowire single-photon detectors (SNSPDs) with high efficiency, polarization insensitivity, and ultrafast response. To achieve these properties in niobium nitride (NbN) SNSPDs, the periodic four-split rings (PFSR) were positioned above the nanowires. This design uses the localized surface plasmon resonance to enhance the electric field around nanowires. For an incident light with a wavelength of 1550 nm, the PFSR-SNSPD structure achieved a polarization extinction ratio of 1.0064 and absorptions of 88.94% and 88.37% under TE and TM polarizations, respectively. The nanowire length was reduced by 85% using a meandering nanowire arrangement with a fill factor of 0.074.

Stoichiometric characteristics and economic implications of water-soluble ions in PM2.5 from a resource-dependent city.

The stoichiometric characteristics of water-soluble ions (WSIs) in PM2.5, which can be used as an indicator socioeconomic development level, are mostly depending on the sources and formation mechanism of PM2.5. This work presents the stoichiometric characteristics and socioeconomic linkage of WSIs in PM2.5 from a resource-dependent city. The relationship between NO3-/SO42- and car parc indexes the contribution of mobile emission source. The equivalent ratio of WSIs suggested that aerosol particles were weak acidic due to the deficiency of cations in PM2.5, which was consistent with the average annual pH (6.27) of precipitation in Wuhai in 2015. NH4+ neutralizes PM2.5 acidity in clean and polluted days, while Ca2+ and NH4+ in dust storm days. Furthermore, the PCA analysis indicated the multi-sources pollution characteristics from Spring to Fall, which was related the small build-up area (only 62.30 km2) and the close-set of various industrial enterprises in Wuhai. The ratios of NO2/SO2 may not work effectively to identify the importance of mobile versus stationary pollution emission sources when the heavy emission from the secondary industry, especially the proportion of secondary industry higher than 65% and the ratios of NO2/SO2 lower than 0.4. This work contributes to more effective control strategies for PM2.5 in resource-dependent areas.