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Svechnikov, S. I., Finkel, M. I., Maslennikov, S. N., Vachtomin, Y. B., Smirnov, K. V., Seleznev, V. A., et al. (2006). Superconducting hot electron bolometer mixer for middle IR range. In Proc. 16th Int. Crimean Microwave and Telecommunication Technology (Vol. 2, pp. 686–687).
Abstract: The developed directly lens coupled hot electron bolometer (HEB) mixer was based on 5 nm superconducting NbN deposited on GaAs substrate. The layout of the structure, including 30x20 mcm^2 active area coupled with a 50 Ohm coplanar line, was patterned by photolithography. The responsivity of the mixer was measured in a direct detection mode in the 25-64 THz frequency range. The noise performance of the mixer and the directivity of the receiver were investigated in a heterodyne mode. A 10.6 mum wavelength CW CO2 laser was utilized as a local oscillator.
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Svechnikov, S. I., Okunev, O. V., Yagoubov, P. A., Gol'tsman, G. N., Voronov, B. M., Cherednichenko, S. I., et al. (1997). 2.5 THz NbN hot electron mixer with integrated tapered slot antenna. IEEE Trans. Appl. Supercond., 7(2), 3548–3551.
Abstract: A Hot Electron Bolometer (HEB) mixer for 2.5 THz utilizing a NbN thin film device, integrated with a Broken Linearly Tapered Slot Antenna (BLTSA), has been fabricated and is presently being tested. The NbN HEB device and the antenna were fabricated on a SiO2membrane. A 0.5 micrometer thick SiO2layer was grown by rf magnetron reactive sputtering on a GaAs wafer. The HEB device (phonon-cooled type) was produced as several parallel strips, 1 micrometer wide, from an ultrathin NbN film 4-7 nm thick, that was deposited onto the SiO2layer by dc magnetron reactive sputtering. The BLTSA was photoetched in a multilayer Ti-Au metallization. In order to strengthen the membrane, the front-side of the wafer was coated with a 5 micrometer thick polyimide layer just before the membrane formation. The last operation was anisotropic etching of the GaAs in a mixture of HNO3and H2O2.
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Svechnikov, S., Gol'tsman, G., Voronov, B., Yagoubov, P., Cherednichenko, S., Gershenzon, E., et al. (1997). Spiral antenna NbN hot-electron bolometer mixer at submm frequencies. IEEE Trans. Appl. Supercond., 7(2), 3395–3398.
Abstract: We have studied the phonon-cooled hot-electron bolometer (HEB) as a quasioptical mixer based on a spiral antenna designed for the 0.3-1 THz frequency band and fabricated on sapphire and high resistivity silicon substrates. HEB devices were produced from superconducting 3.5-5 nm thick NbN films with a critical temperature 10-12 K and a critical current density of approximately 10/sup 7/ A/cm/sup 2/ at 4.2 K. For these devices we reached a DSB receiver noise temperature below 1500 K, a total conversion loss of L/sub t/=16 dB in the 500-700 GHz frequency range, an IF bandwidth of 3-4 GHz and an optimal LO absorbed power of /spl sime/4 /spl mu/W. We experimentally analyzed various contributions to the conversion loss and obtained an RF coupling factor of about 5 dB, internal mixer loss of 10 dB and IF mismatch of 1 dB.
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Svechnikov, S., Verevkin, A., Voronov, B., Menschikov, E., Gershenzon, E., & Gol'tsman, G. (1998). Quasioptical phonon-cooled NbN hot electron bolometer mixers at 0.5-1.1 THz. In Proc. 9th Int. Symp. Space Terahertz Technol. (pp. 45–51).
Abstract: The noise performance of a receiver incorporating spiral antenna coupled NbN phonon-cooled superconducting hot electron bolometric mixer is measured from 450 GHz to 1200 GHz. The mixer element is thin (thickness nm) NbN 1.5 pm wide and 0.2 i.um long film fabricated by lift-off e-beam lithography on high-resistive silicon substrate. The noise of the receiver temperature is 1000 K at 800-900 GHz, 1200 K at 950 GHz, and 1600 K at 1.08 THz. The required (absorbed) local-oscillator power is —20 nW.
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Słysz, W., Węgrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2006). Fiber-coupled single-photon detectors based on NbN superconducting nanostructures for practical quantum cryptography and photon-correlation studies. Appl. Phys. Lett., 88(26), 261113 (1 to 3).
Abstract: We have fabricated and tested a two-channel single-photon detector system based on two fiber-coupled superconducting single-photon detectors (SSPDs). Our best device reached the system quantum efficiency of 0.3% in the 1540-nm telecommunication wavelength with a fiber-to-detector coupling factor of about 30%. The photoresponse consisted of 2.5-ns-wide voltage pulses with a rise time of 250ps and timing jitter below 40ps. The overall system response time, measured as a second-order, photon cross-correlation function, was below 400ps. Our SSPDs operate at 4.2K inside a liquid-helium Dewar, but their optical fiber inputs and electrical outputs are at room temperature. Our two-channel detector system should find applications in practical quantum cryptography and in antibunching-type quantum correlation measurements.
The authors would like to thank Dr. Marc Currie for his assistance in early time-resolved photoresponse measurements and Professor Atac Imamoglu for his support. This work was supported by the Polish Ministry of Science under Project No. 3 T11B 052 26 (Warsaw), RFBR 03-02-17697 and INTAS 03-51-4145 grants (Moscow), CRDF Grant No. RE2-2531-MO-03 (Moscow), RE2-2529-MO-03 (Moscow and Rochester), and US AFOSR FA9550-04-1-0123 (Rochester). Additional funding was provided by the grants from the MIT Lincoln Laboratory and BBN Technologies Corp.
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Słysz, W., Wegrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2007). Fibre-coupled, single photon detector based on NbN superconducting nanostructures for quantum communications. J. Modern Opt., 54(2-3), 315–326.
Abstract: We present a novel, two-channel, single photon receiver based on two fibre-coupled, NbN, superconducting, single photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders and are known for ultrafast and efficient detection of visible-to-infrared photons. Coupling between the NbN detector and optical fibre was achieved using a micromechanical photoresist ring placed directly over the SSPD, holding the fibre in place. With this arrangement, we obtained coupling efficiencies up to ∼30%. Our experimental results showed that the best receiver had a near-infrared system quantum efficiency of 0.33% at 4.2 K. The quantum efficiency increased exponentially with the photon energy increase, reaching a few percent level for visible-light photons. The photoresponse pulses of our devices were limited by the meander high kinetic inductance and had the rise and fall times of approximately 250 ps and 5 ns, respectively. The receiver's timing jitter was in the 37 to 58 ps range, approximately 2 to 3 times larger than in our older free-space-coupled SSPDs. We stipulate that this timing jitter is in part due to optical fibre properties. Besides quantum communications, the two-detector arrangement should also find applications in quantum correlation experiments.
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Tarkhov, M., Claudon, J., Poizat, J. P., Korneev, A., Divochiy, A., Minaeva, O., et al. (2008). Ultrafast reset time of superconducting single photon detectors. Appl. Phys. Lett., 92(24), 241112 (1 to 3).
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Tarkhov, M., Morozov, D., Mauskopf, P., Seleznev, V., Korneev, A., Kaurova, N., et al. (2006). Single photon counting detector for THz radioastronomy. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 119–122).
Abstract: In this paper we present the results of the research on the superconducting NbN-ultrathin-film single- photon detectors (SSPD) which are capable to detect single quanta in middle IR range. The detection mechanism is based on the hotspot formation in quasi-two-dimensional superconducting structures upon photon absorption. Spectral measurements showed that up to 5.7 gm wavelength (52 THz) the SSPD exhibits single-photon sensitivity. Reduction of operation temperature to 1.6 K allowed us to measure quantum efficiency of -4% at 60 THz. Although further decrease of the operation temperature far below 1 K does not lead to any significant increase of quantum efficiency. We expect that the improvement of the SSPD's performance at reduced operation temperature will make SSPD a practical detector with high characteristics for much lower THz frequencies as well.
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Tong, C. E., Blundell, R., Papa, D. C., Smith, M., Kawamura, J., Gol'tsman, G., et al. (1999). An all solid-state superconducting heterodyne receiver at terahertz frequencies. IEEE Microw. Guid. Wave Lett., 9(9), 366–368.
Abstract: A superconducting hot-electron bolometer mixer-receiver operating from 1 to 1.26 THz has been developed. This heterodyne receiver employs two solid-state local oscillators each consisting of a Gunn oscillator followed by two stages of varactor frequency multiplication. The measured receiver noise temperature is 1350 K at 1.035 THz and 2700 K at 1.26 THz. This receiver demonstrates that tunable solid-state local oscillators, supplying only a few micro-watts of output power, can be used in terahertz receiver applications.
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Tret'yakov, I. V., Kaurova, N. S., Voronov, B. M., Anfert'ev, V. A., Revin, L. S., Vaks, V. L., et al. (2016). The influence of the diffusion cooling on the noise band of the superconductor NbN hot-electron bolometer operating in the terahertz range. Tech. Phys. Lett., 42(6), 563–566.
Abstract: Results of an experimental study of the noise temperature (Tn) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (Tb) are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (Tc) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature Tb close to Tc was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at Tb â‰<aa> Tc for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/ metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.
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