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Yang JKW, Dauler E, Ferri A, Pearlman A, Verevkin A, Gol’tsman G, et al. Fabrication development for nanowire GHz-counting-rate single-photon detectors. IEEE Trans Appl Supercond. 2005;15(2):626–30.
Abstract: We have developed a fabrication process for GHz-counting-rate, single-photon, high-detection-efficiency, NbN, nanowire detectors. We have demonstrated two processes for the device patterning, one based on the standard polymethylmethacrylate (PMMA) organic positive-tone electron-beam resist, and the other based on the newer hydrogen silsesquioxane (HSQ) negative-tone spin-on-glass resist. The HSQ-based process is simple and robust, providing high resolution and the prospect of high fill-factors. Initial testing results show superconductivity in the films, and suggest that the devices exhibit photosensitivity.
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Gol’tsman GN, Smirnov K, Kouminov P, Voronov B, Kaurova N, Drakinsky V, et al. Fabrication of nanostructured superconducting single-photon detectors. IEEE Trans Appl Supercond. 2003;13(2):192–5.
Abstract: Fabrication of NbN superconducting single-photon detectors, based on the hotspot effect is presented. The hotspot formation arises in an ultrathin and submicrometer-width superconductor stripe and, together with the supercurrent redistribution, leads to the resistive detector response upon absorption of a photon. The detector has a meander structure to maximally increase its active area and reach the highest detection efficiency. Main processing steps, leading to efficient devices, sensitive in 0.4-5 /spl mu/m wavelength range, are presented. The impact of various processing steps on the performance and operational parameters of our detectors is discussed.
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Seliverstov S, Maslennikov S, Ryabchun S, Finkel M, Klapwijk TM, Kaurova N, et al. Fast and sensitive terahertz direct detector based on superconducting antenna-coupled hot electron bolometer. IEEE Trans Appl Supercond. 2015;25(3):2300304.
Abstract: We characterize superconducting antenna-coupled hot-electron bolometers for direct detection of terahertz radiation operating at a temperature of 9.0 K. The estimated value of responsivity obtained from lumped-element theory is strongly different from the measured one. A numerical calculation of the detector responsivity is developed, using the Euler method, applied to the system of heat balance equations written in recurrent form. This distributed element model takes into account the effect of nonuniform heating of the detector along its length and provides results that are in better agreement with the experiment. At a signal frequency of 2.5 THz, the measured value of the optical detector noise equivalent power is 2.0 × 10-13 W · Hz-0.5. The value of the bolometer time constant is 35 ps. The corresponding energy resolution is about 3 aJ. This detector has a sensitivity similar to that of the state-of-the-art sub-millimeter detectors operating at accessible cryogenic temperatures, but with a response time several orders of magnitude shorter.
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Zorin M, Milostnaya I, Gol'tsman GN, Gershenzon EM. Fast NbN superconducting switch controlled by optical radiation. IEEE Trans Appl Supercond. 1997;7(2):3734–7.
Abstract: The switching time and the optical control power of the NbN superconducting switch have been measured. The device is based on the ultrathin film 5-8 nm thick patterned as a structure of several narrow parallel strips (/spl sim/1 /spl mu/m wide) connected to wide current leads. The current-voltage characteristic of the switch at temperature 4.2 K demonstrated a hysteresis due to DC current self-heating. We studied the superconducting-to-resistive state transition induced by both optical and bias-current excitations. The optical pulse duration was /spl sim/20 ps and the rise time of the current step was determined to be less than 50 ps. The optical pulse was delivered to the switch by the semiconductor laser through an optical fiber. We found that the measured switching time is less than the duration of the optical excitation. The threshold optical power density does not exceed 3/spl middot/10/sup 3/ W/cm/sup 2/. The proposed device can be used in the fiber input of LTS rapid single flux quantum circuits.
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Galeazzi M. Fundamental noise processes in TES devices. IEEE Trans Appl Supercond. 2011;21(3):267–71.
Abstract: Microcalorimeters and bolometers are noise-limited devices, therefore, a proper understanding of all noise sources is essential to predict and interpret their performance. In this paper, I review the fundamental noise processes contributing to Transition Edge Sensor (TES) microcalorimeters and bolometers and their effect on device performance. In particular, I will start with a simple, monolithic device model, moving to a more complex one involving discrete components, to finally move to today's more realistic, comprehensive model. In addition to the basic noise contribution (equilibrium Johnson noise and phonon noise), TES are significantly affected by extra noise, which is commonly referred to as excess noise. Different fundamental processes have been proposed and investigated to explain the origin of this excess noise, in particular near equilibrium non-linear Johnson noise, flux-flow noise, and internal thermal fluctuation noise. Experimental evidence shows that all three processes are real and contribute, at different levels, to the TES noise, although different processes become important at different regimes. It is therefore time to discard the term “excess noise” and consider these terms part of the “fundamental noise processes” instead.
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