Superconducting parallel nanowire detector with photon number resolving functionality

TL;DR

This paper introduces a superconducting parallel nanowire detector capable of resolving photon numbers with high speed and sensitivity, outperforming existing detectors in simplicity and noise performance.

Contribution

The paper presents a novel superconducting nanowire-based photon number resolving detector with spatial multiplexing, demonstrating improved speed, sensitivity, and noise characteristics.

Findings

Photoresponse FWHM as low as 660ps

Counting performance at 80 MHz

Quantum efficiency estimated at 3% at 700 nm

Abstract

We present a new photon number resolving detector (PNR), the Parallel Nanowire Detector (PND), which uses spatial multiplexing on a subwavelength scale to provide a single electrical output proportional to the photon number. The basic structure of the PND is the parallel connection of several NbN superconducting nanowires (100 nm-wide, few nm-thick), folded in a meander pattern. Electrical and optical equivalents of the device were developed in order to gain insight on its working principle. PNDs were fabricated on 3-4 nm thick NbN films grown on sapphire (substrate temperature TS=900C) or MgO (TS=400C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture. The device performance was characterized in terms of speed and sensitivity. The photoresponse shows a full width at half maximum (FWHM) as low as 660ps. PNDs showed counting performance at 80 MHz repetition rate. Building the histograms of the photoresponse peak, no multiplication noise buildup is observable and a one photon quantum efficiency can be estimated to be QE=3% (at 700 nm wavelength and 4.2 K temperature). The PND significantly outperforms existing PNR detectors in terms of simplicity, sensitivity, speed, and multiplication noise.