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Ryabchun, S. A., Tretyakov, I. V., Finkel, M. I., Maslennikov, S. N., Kaurova, N. S., Seleznev, V. A., et al. (2008). Fabrication and characterisation of NbN HEB mixers with in situ gold contacts. In Proc. 19th Int. Symp. Space Terahertz Technol. (pp. 62–67). Groningen, Netherlands.
Abstract: We present our recent results of the fabrication and testing of NbN hot-electron bolometer mixers with in situ gold contacts. An intermediate frequency bandwidth of about 6 GHz has been measured for the mixers made of a 3.5-nm NbN film on a plane Si substrate with in situ gold contacts, compared to 3.5 GHz for devices made of the same film with ex situ gold contacts. The increase in the intermediate frequency bandwidth is attributed to additional diffusion cooling through the improved contacts, which is further supported by the its dependence on the bridge length: intermediate frequency bandwidths of 3.5 GHz and 6 GHz have been measured for devices with lengths of 0.35 μm and 0.16 μm respectively at a local oscillator frequency of 300 GHz near the superconducting transition. At a local oscillator frequency of 2.5 THz the receiver has offered a DSB noise temperature of 950 K. When compared to the previous result of 1300 K obtained at the same local oscillator frequency for devices fabricated with an ex situ route, such a low value of the noise temperature may also be attributed to the improved gold contacts.
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Cherednichenko, S., Kollberg, E., Angelov, I., Drakinskiy, V., Berg, T., & Merkel, H. (2005). Effect of the direct detection effect on the HEB receiver sensitivity calibration. In Proc. 16th Int. Symp. Space Terahertz Technol. (pp. 235–239). Göteborg, Sweden.
Abstract: We analyze the scale of the HEB receiver sensitivity calibration error caused by the so called “direct detection effect”. The effect comes from changing of the HEB parameters when whey face the calibration loads of different temperatures. We found that for HIFI Band 6 mixers (Herschel Space Observatory) the noise temperature error is of the order of 8% for 300K/77K loads (lab receiver) and 2.5% for 100K/10K loads (in HIFI). Using different approach we also predict that with an isolator between the mixer and the low noise amplifiers the error can be much smaller.
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Cherednichenko, S., Drakinskiy, V., Baubert, J., Lecomte, B., Dauplay, F., Krieg, J. M., et al. (2006). 2.5 THz multipixel heterodyne receiver based on NbN HEB mixers. In Proc. SPIE (Vol. 6275, 62750I (1 to 11)).
Abstract: A 16 pixel heterodyne receiver for 2.5 THz has been developed based on NbN superconducting hot-electron bolometer (HEB) mixers. The receiver uses a quasioptical RF coupling approach where HEB mixers are integrated into double dipole antennas on 1.5 µm thick Si3N4/SiO2 membranes. Spherical mirrors (one per pixel) and backshort distance from the antenna have been used to design the output mixer beam profile. The camera design allows all 16 pixel IF readout in parallel. The gain bandwidth of the HEB mixers on Si3N4/SiO2 membranes was found to be 0.7÷0.9 GHz, which is much smaller than for similar devices on silicon. Application of buffer layers and use of alternative types of membranes (e.g. silicon-on-insulator) is under investigation.
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Kawamura, J., Blundell, R., Tong, C. - Y. E., Papa, D. C., Hunter, T. R., Gol'tsman, G., et al. (1998). First light with an 800 GHz phonon-cooled HEB mixer receiver. In Proc. 9th Int. Symp. Space Terahertz Technol. (pp. 35–43). Pasadena, California, USA.
Abstract: Phonon-cooled superconductive hot-electron bolometric (HEB) mixers are incorporated in a waveguide receiver designed to operate near 800 Gliz. The mixer elements are thin-film nio- bium nitride microbridges with dimensions of 4 nm thickness, 0.2 to 0.3 p.m in length and 2 jun in width. At 780 GHz the best receiver noise temperature is 840 K (DSB). The mixer IF bandwidth is 2.0 GHz, the absorbed LO power is —0.1 1.1W. A fixed-tuned version of the re- ceiver was installed at the Submillimeter Telescope Observatory on Mt. Graham, Arizona, to conduct astronomical observations. These observations represent the first time that a receiver incorporating any superconducting HEB mixer has been used to detect a spectral line of celes- tial origin.
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Cao, A., Jiang, L., Chen, S. H., Antipov, S. V., & Shi, S. C. (2007). IF gain bandwidth of a quasi-optical NbN superconducting HEB mixer. In Proc. International conference on microwave and millimeter wave technology (pp. 1–3). Builin.
Abstract: In this paper, the intermediate frequency (IF) gain bandwidth of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer is investigated at 500 GHz with an IF system incorporating with a frequency down-converting scheme which is able to sweep the IF signal in a frequency range of 0.3-4 GHz. The IF gain bandwidth of the device is measured to be 1.5 GHz when it is biased at a voltage of the minimum noise temperature, and becomes larger when the bias voltage increases.
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Ryabchun, S. A., Tretyakov, I. V., Finkel, M. I., Maslennikov, S. N., Kaurova, N. S., Seleznev, V. A., et al. (2009). NbN phonon-cooled hot-electron bolometer mixer with additional diffusion cooling. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 151–154). Charlottesville, USA.
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Tretyakov, I. V., Ryabchun, S. A., Maslennikov, S. N., Finkel, M. I., Kaurova, N. S., Seleznev, V. A., et al. (2008). NbN HEB mixer: fabrication, noise temperature reduction and characterization. In Proc. Basic problems of superconductivity. Moscow-Zvenigorod.
Abstract: We demonstrate that in the terahertz region superconducting hot-electron mixers offer the lowest noise temperature, opening the possibility of using HTS's in the future to fabricate these devices. Specifically, a noise temperature of 950 K was measured for the receiver operating at 2.5 THz with a NbN HEB mixer, and a gain bandwidth of 6 GHz was measured at 300 GHz near Tc for the same mixer.
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Baselmans, J. J. A., Baryshev, A., Reker, S. F., Hajenius, M., Gao, J. R., Klapwijk, T. M., et al. (2005). Direct detection effect in small volume hot electron bolometer mixers. Appl. Phys. Lett., 86(16), 163503 (1 to 3).
Abstract: We measure the direct detection effect in a small volume (0.15μm×1μm×3.5nm)(0.15μm×1μm×3.5nm) quasioptical NbN phonon cooled hot electronbolometermixer at 1.6THz1.6THz. We find that the small signal sensitivity of the receiver is underestimated by 35% due to the direct detection effect and that the optimal operating point is shifted to higher bias voltages when using calibration loads of 300K300K and 77K77K. Using a 200GHz200GHzbandpass filter at 4.2K4.2K the direct detection effect virtually disappears. This has important implications for the calibration procedure of these receivers in real telescope systems.
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Гольцман, Г. Н., & Лудков, Д. Н. (2003). Сверхпроводниковые смесители на горячих электронах терагерцового диапазона и их применение в радиоастрономии. Изв. высших учебных заведений. Радиофизика, 46(8/9).
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Uzawa, Y., Miki, S., Wang, Z., Kawakami, A., Kroug, M., Yagoubov, P., et al. (2002). Performance of a quasi-optical NbN hot-electron bolometric mixer at terahertz frequencies. Supercond. Sci. Technol., 15(1), 141–145.
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