Single- and multi-photon counting using an array of SNSPDs

We report on the design, fabrication and electro-optical characterization at T = 2.9 K of a photon number resolving detector designed to obtain a pulse-position resolution. This pulse-position-resolving detector (PPRD) is based on the spatial multiplexing of four superconducting nanowire avalanche photodiodes (SNAPs) [8, 9] connected in series. We choose to exploit the 2-SNAP configuration (i.e., 2 connected in parallel nanowires) to improve the signal-to-noise ratio (SNR) of the PPRD. Each pixel (i.e., a 2-SNAP) has in parallel AuPd resistor Ri (with i = 1, 4) of different value. As a result of a detection event, each pixel produces a pulse with peak voltage I
_b
R
_i
, allowing in this way position resolution of the detection event.