Nano-optical observation of cascade switching in a parallel   superconducting nanowire single photon detector
  The device physics of parallel-wire superconducting nanowire single photon detectors is based on a cascade process. Using nano-optical techniques and a parallel wire device with spatially-separate pixels we explicitly demonstrate the single- and multi-photon triggering regimes. We develop a model for describing efficiency of a detector operating in the arm-trigger regime. We investigate the timing response of the detector when illuminating a single pixel and two pixels. We see a change in the active area of the detector between the two regimes and find the two-pixel trigger regime to have a faster timing response than the one-pixel regime. 
Robert M. Heath, Michael G. Tanner, Alessandro Casaburi, Mark G.   Webster, Lara San Emeterio Alvarez, Zoe H. Barber, Richar...
quant-ph cond-mat.supr-con physics.optics