Spectral cut-off in the efficiency of the resistive state formation caused by absorption of a single-photon in current-carrying superconducting nano-strips

We have studied supercurrent-assisted formation of the resistive state in nano-structured disordered superconducting Nb(N) films after absorption of a single optical to near-infrared photon. The efficiency of the resistive state formation has a pronounced spectral cut-off; corresponding threshold photon energy decreases with the bias current. Analysis of the experimental data in the framework of the refined hot-spot model suggests that the quantum yield for near-infrared photons increases with the photon energy. Relaxation of the resistive state depends on the photon energy making the phenomena feasible for the development of energy resolving single-photon detectors. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005