Single photon detectors based on superconducting nanowires over large active areas

Abstract

Single photon detectors based on superconducting niobium nitride (NbN) nanowires over areas of 30 μm×30 μm are fabricated using E-beam lithography (EBL) and reactive ion etching (RIE). SEM images of the NbN nanowires indicate that the widths are uniformly 200 nm over the whole lengths and the fill factors are about 66.7%. The detectors are characterized at optical wavelengths of 810, 1310 and 1550 nm, respectively. Maximum detector efficiencies (DE) of 0.3% at 1550 nm and 0.6% at 1310 nm are obtained, and the resetting times are just about 10 ns. Additionally we demonstrated the broadband response properties of the devices as well as linear relations between the count rates and incident photon numbers.