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Yagoubov P, Kroug M, Merkel H, Kollberg E, Gol'tsman G, Svechnikov S, et al. Noise temperature and local oscillator power requirement of NbN phonon-cooled hot electron bolometric mixers at terahertz frequencies. Appl Phys Lett. 1998;73(19):2814–6.
Abstract: In this letter, the noise performance of NbN-based phonon-cooled hot electron bolometric quasioptical mixers is investigated in the 0.55–1.1 THz frequency range. The best results of the double-sideband <cd><2018>DSB<cd><2019> noise temperature are: 500 K at 640 GHz, 600 K at 750 GHz, 850 K at 910 GHz, and 1250 K at 1.1 THz. The water vapor in the signal path causes significant contribution to the measured receiver noise temperature around 1.1 THz. The devices are made from 3-nm-thick NbN film on high-resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are typically 0.2Ï«2 um. The amount of local oscillator power absorbed in the bolometer is less than 100 nW.
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Yagoubov P, Kroug M, Merkel H, Kollberg E, Hübers H-W, Schubert J, et al. NbN hot electron bolometric mixers at frequencies between 0.7 and 3.1 THz. In: Proc. 10th Int. Symp. Space Terahertz Technol.; 1999. p. 238–46.
Abstract: The performance of NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixers is investigated in the 0.7-3.1 THz frequency range. The devices are made from a 3.5-4 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The length of the bolometer microbridge is 0.1- 0.2 gm, the width is 1-2 gm. The best results of the DSB receiver noise temperature measured at 1.5 GHz intermediate frequency are: 800 K at 0.7 THz, 1100 K at 1.6 THz, 2000 K at 2.5 THz and 4200 K at 3.1 THz. The measurements were performed with a far infrared laser as the local oscillator (LO) source. The estimated LO power required is less than 500 nW at the receiver input. First results on the spiral antenna polarization measurements are reported.
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Yagoubov P, Kroug M, Merkel H, Kollberg E, Schubert J, Hubers HW, et al. Hot electron bolometric mixers based on NbN films deposited on MgO substrates. In: Inst. Phys. Conf. Ser. Vol 167. Barcelona, Spain; 1999. p. 687–90.
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Yagoubov P, Kroug M, Merkel H, Kollberg E, Schubert J, Hubers H-W, et al. Heterodyne measurements of a NbN superconducting hot electron mixer at terahertz frequencies. IEEE Trans Appl Supercond. 1999;9(2):3757–60.
Abstract: The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.
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Yagubov P, Gol'tsman G, Voronov B, Seidman L, Siomash V, Cherednichenko S, et al. The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate. In: Proc. 7th Int. Symp. Space Terahertz Technol. Charlottesville, Virginia, USA; 1996. p. 290–302.
Abstract: We report on some unusual features observed during fabrication of ultrathin NbN films with high Tc. The films were used to fabricate HEB mixers, which were evaluated for IF bandwidth measurements at 140 GHz. Ultrathin films were fabricated using reactive dc magnetron sputtering with a discharge current source. Reproducible parameters of the films are assured keeping constant the difference between the discharge voltage in pure argon, and in a gas mixture, for the same current. A maximum bandwidth of 4 GHz at optimal LO and dc bias was obtained for mixer chip based on NbN film 35 A thick with Tc = 11 K.
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Yazoubov P, Kroug M, Merkel H, Kollberg E, Gol'tsman G, Lipatov A, et al. Quasioptical NbN phonon-cooled hot electron bolometric mixers with low optimal local oscillator power. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 131–40.
Abstract: In this paper, the noise perform.ance of NIN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixers is investigated in the 0.55-1.1 THz frequency range. The best results of the DSB noise temperature are: 500 K at 640 GHz, 600 K at 750 GHz, 850 K at 910 GHz and 1250 K at 1.1 THz. The water vapor in the signal path causes a significant contribution to the measured noise temperature around 1.1 THz. The required LO power is typically about 60 nW. The frequency response of the spiral antenna+lens system is measured using a Fourier Transform Spectrometer with the HEB operating in a detector mode.
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Zhang J, Boiadjieva N, Chulkova G, Deslandes H, Gol'tsman GN, Korneev A, et al. Noninvasive CMOS circuit testing with NbN superconducting single-photon detectors. Electron Lett. 2003;39(14):1086–8.
Abstract: The 3.5 nm thick-film, meander-structured NbN superconducting single-photon detectors have been implemented in the CMOS circuit-testing system based on the detection of near-infrared photon emission from switching transistors and have significantly improved the performance of the system. Photon emissions from both p- and n-MOS transistors have been observed.
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Zhang J, Slysz W, Verevkin A, Okunev O, Chulkova G, Korneev A, et al. Response time characterization of NbN superconducting single-photon detectors. IEEE Trans. Appl. Supercond.. 2003;13(2):180–3.
Abstract: We report our time-resolved measurements of NbN-based superconducting single-photon detectors. The structures are meander-type, 10-nm thick, and 200-nm wide stripes and were operated at 4.2 K. We have shown that the NbN devices can count single-photon pulses with below 100-ps time resolution. The response signal pulse width was about 150 ps, and the system jitter was measured to be 35 ps.
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Zhang W, Jiang L, Lin ZH, Yao QJ, Li J, Shi SC, et al. Development of a quasi-optical NbN superconducting HEB mixer. In: Proc. 16th Int. Symp. Space Terahertz Technol.; 2005. p. 209–13.
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolometer) mixer measured at 500 and 850GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled by a 4-K close-cycled refrigerator. Measured receiver noise temperature at 850 and 500GHz are 3000K and 2500K respectively with wire grid as beamsplitter, while the lowest receiver noise temperature is found to be approximately 1200K with Mylar film. The theoretical receiver noise temperature (taking into account the elliptical polarization of log-spiral antenna) is consistent with measured one. The receiver noise temperature and conversion gain with 15-μm Mylar film as the beamsplitter at 500GHz are thoroughly investigated for different LO pumping levels and dc biases. The stability of the mixer’s IF output power is also demonstrated.
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Zhang W, Li N, Jiang L, Miao W, Lin Z-H, Yao Q-J, et al. Noise behaviour of a THz superconducting hot-electron bolometer mixer. Chinese Phys Lett. 2007;24(6):1778–81.
Abstract: A quasi-optical superconducting NbN hot-electron bolometer (HEB) mixer is measured in the frequency range of 0.5–2.5 THz for understanding of the frequency dependence of noise temperature of THz coherent detectors. It has been found that noise temperature increasing with frequency is mainly due to the coupling loss between the quasi-optical planar antenna and the superconducting HEB bridge when taking account of non-uniform distribution of high-frequency current. With the coupling loss corrected, the superconducting HEB mixer demonstrates a noise temperature nearly independent of frequency.
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