We fabricated and characterized nanowire superconducting single-photon detectors made of 4 nm thick amorphous Mo x Si1−x films. At 1.7 K the best devices exhibit a detection efficiency (DE) up to 18% ...at 1.2 wavelength of unpolarized light, a characteristic response time of about 6 ns and timing jitter of 120 ps. The DE was studied in wavelength range from 650 nm to 2500 nm. At wavelengths below 1200 nm these detectors reach their maximum DE limited by photon absorption in the thin MoSi film.
An electrothermal model is used to perform a theoretical analysis of the operation of a superconducting detector based on a strip of micrometer width and having photon number resolution. ...Configurations with series and parallel connections of detector sections are investigated. It is established that when such microstrips are used, a series connection of sections is better in terms of the number of simultaneously resolved photons and the amplitude of the response from a superconductor detector.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The topic of superconductivity in strongly disordered materials has attracted significant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as ...bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for the non-Bardeen-Cooper-Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for the operation of corresponding nanoelectronic devices. Here we report an experimental study of the electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. The temperature dependence of the critical current follows the textbook Ginzburg-Landau prediction for the quasi-one-dimensional superconducting channel Ic ∼ (1-T/Tc)3/2. We find that conventional models based on the the phase slip mechanism provide reasonable fits for the shape of R(T) transitions. Better agreement with R(T) data can be achieved assuming the existence of short 'weak links' with slightly reduced local critical temperature Tc. Hence, one may conclude that an 'exotic' intrinsic electronic inhomogeneity either does not exist in our structures, or, if it does exist, it does not affect their resistive state properties, or does not provide any specific impact distinguishable from conventional weak links.
We develop large area superconducting single-photon detector SSPD with a micron-wide strip suitable for free-space coupling or packaging with multi-mode optical fibres. The detector sensitive area is ...20 μm in diameter. In near infrared (1330 nm wavelength) our SSPD exhibits above 30% detection efficiency with low dark counts and 45 ps timing jitter.
We optimized NbN films on a Si substrate with a buffer SiO2 layer to produce superconducting microstrip single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized ...bias current. We varied thickness of films and observed the maximum QE saturation for device based on the thinner film with the lowest ratio RS300/RS20.
We experimentally demonstrate strong temperature dependence of the critical current of the superconducting 600-nm-wide and 5-μm-long bridge made of NbN/Au bilayer. The result is achieved due to the ...proximity effect realized between the highly disordered superconducting NbN layer and low resistive normal-metal Au layer.
We demonstrate coherent dynamics of quantized magnetic fluxes in a superconducting loop with a weak link, a nanobridge patterned from the same thin NbN film as the loop. The bridge is a short, ...rounded shape constriction, close to 10 nm long and 20–30 nm wide, having minimal width at its center. It superposes neighboring fluxoid states of the loop. Quantum state control and coherent oscillations in the driven time evolution of the tunnel-junctionless system are achieved. Decoherence and energy relaxation in the system are studied using a combination of microwave spectroscopy and direct time-domain techniques. The effective flux noise behavior suggests inductance fluctuations as a possible cause of the decoherence.
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