Maslennikov, S. (2014). RF heating efficiency of the terahertz superconducting hot-electron bolometer. arXiv, 1404.5276, arXiv:1404.5276.
Abstract: We report results of the numerical solution by the Euler method of the system of heat balance equations written in recurrent form for the superconducting hot-electron bolometer (HEB) embedded in an electrical circuit. By taking into account the dependence of the HEB resistance on the transport current we have been able to calculate rigorously the RF heating efficiency, absorbed local oscillator (LO) power and conversion gain of the HEB mixer. We show that the calculated conversion gai nis in excellent agreement with the experimental results, and that the substitution of the calculated RF heating efficiency and absorbed LO power into the expressions for the conversion gain and noise temperature given by the analytical small-signal model of the HEB yields excellent agreement with the corresponding measured values
Keywords: superconducting hot-electron bolometer mixer, HEB, NbN, distributed model, HEB model, HEB mixer model, heat balance equa-tions, conversion gain, RF heating efficiency, noise temperature, simulation, Euler method
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Lobanov, Y., Shcherbatenko, M., Shurakov, A., Rodin, A. V., Klimchuk, A., Nadezhdinsky, A. I., et al. (2014). Heterodyne detection at near-infrared wavelengths with a superconducting NbN hot-electron bolometer mixer. Opt. Lett., 39(6), 1429–1432.
Abstract: We report on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer. The results are important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects, as well as for quantum optical tomography and fiber-optic sensing. Receiver configuration as well as fiber-to-detector light coupling designs are discussed. Light absorption of the superconducting detectors was enhanced by nano-optical antennas, which were coupled to optical fibers. An intermediate frequency (IF) bandwidth of about 3 GHz was found in agreement with measurements at 300 GHz, and a noise figure of about 25 dB was obtained that was only 10 dB above the quantum limit.
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Semenov, A. V., Devyatov, I. A., Ryabchun, S. A., Maslennikov, S. N., Maslennikova, A. S., Larionov, P. A., et al. (2011). Absorption of terahertz electromagnetic radiation in dirty superconducting film at arbitrary type of the spectral functions. Rus. J. Radio Electron., (10).
Abstract: A problem of absorption of high-frequency electromagnetic field in dirty superconductor is treated within Keldysh technic. Expression for the source term in the kinetic equation for quasiparticle distribution function is derived. The result is significant for deriving a consistent microscopic theory of superconducting detectors for terahertz frequency range, perspective detectors on kinetic inductance of current-biased superconducting strip and on Josephson inductance of tunnel.
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Pentin, I., Finkel, M., Maslennikov, S., Vakhtomin, Y., Smirnov, K., Kaurova, N., et al. (2017). Superconducting hot-electron-bolometer mixers for the mid-IR. Rus. J. Radio Electron., (10), http://jre.cplire.ru/jre/oct17/9/text.pdf.
Abstract: The work presents the result of development of the NbN superconducting hot-electron-bolometer (HEB) mixer. The sensitive element of the mixer is directly coupled to mid-IR radiation, and doesn’t have planar metallic antenna. Investigations of noise characteristics of NbN HEB mixer were performed at the frequency 28.4 THz (λ = 10.6 µm) by using gas-discharge CW CO2-laser without consideration of optical and electrical losses in the heterodyne receiver. The noise temperature of NbN HEB mixer with the size of the sensitive element 10 µm × 10 µm was 2320 K (~ 1.5hν/kB) at the heterodyne frequency of 28.4 THz. The noise temperature was determined by measuring the Y-factor taking into account the term which describes fluctuations of zero-point oscillations in accordance with the fluctuation-dissipation theorem of Calle-Welton. Isothermal method was used to estimate the absorbed heterodyne radiation power which was 9 µW at the optimal operating point for the minimum noise temperature of NbN HEB mixer.
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Gol'tsman, G., Maslennikov, S., Finkel, M., Antipov, S., Kaurova, N., Grishina, E., et al. (2006). Nanostructured ultrathin NbN film as a terahertz hot-electron bolometer mixer. In Proc. MRS (Vol. 935, 210 (1 to 6)).
Abstract: Planar spiral antenna coupled and directly lens coupled NbN HEB mixer structures are studied. An additional MgO buffer layer between the superconducting film and Si substrate is introduced. The buffer layer enables us to increase the gain bandwidth of a HEB mixer due to better acoustic transparency. The gain bandwidth is widened as NbN film thickness decreases and amounts to 5.2 GHz. The noise temperature of antenna coupled mixer is 1300 and 3100 K at 2.5 and 3.8 THz respectively. The structure and composition of NbN films is investigated by X-ray diffraction spectroscopy methods. Noise performance degradation at LO frequencies more than 3 THz is due to the use of a planar antenna and signal loss in contacts between the antenna and the sensitive NbN bridge. The mixer is reconfigured for operation at higher frequencies in a manner that receiver’s noise temperature is only 2300 K (3 times of quantum limit) at LO frequency of 30 THz.
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