Experimental investigation of the detection mechanism in WSi nanowire superconducting single photon detectors
Rosalinda Gaudio, Jelmer J. Renema, Zili Zhou, Varun B. Verma, Jeffrey M. Shainline, Martin J. Stevens, Richard P. Mirin, Sae Woo Nam, Martin P. van Exter, Michiel J. de Dood, Andrea Fiore
We use quantum detector tomography to investigate the detection mechanism in WSi nanowire superconducting single photon detectors (SSPDs). To this purpose, we fabricated a 250 nm wide and 250 nm long WSi nanowire and measured its response to impinging photons with wavelengths ranging from λ = 900 nm to λ = 1650 nm. The tomographically resolved multiphoton response of the detector shows that the detector response depends on the total excitation energy only. Moreover, for excitation energies above 0.8eV the current energy relation is linear, similar to what was observed in NbN nanowires, whereas the current-energy relation deviates from linear behaviour for total energies below 0.8eV.