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Kroug M, Yagoubov P, Gol'tsman G, Kollberg E. NbN quasioptical phonon cooled hot electron bolometric mixers at THz frequencies. In: Inst. Phys. Conf. Ser. Vol 1. Bristol; 1997. p. 405–8.
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Semenov A, Richter H, Hübers H-W, Smirnov K, Voronov B, Gol'tsman G. Development of terahertz superconducting hot-electron bolometer mixers. In: Proc. 6th European Conf. Appl. Supercond. Vol 181.; 2003. p. 2960–5.
Abstract: We present recent results of the development of phonon cooled hot-electron bolometric (HEB) mixers for airborne and balloon borne terahertz heterodyne receivers. Three iomportant issues have been addresses: the quality of NbN films the HEB mixers were made from, the spectral properties of the HEB mixers and the local oscillator power required for optical operation. Studies with an atomic force microscope indicate, that the performance of the HEB mixer might have been effected by the microstructure of the NbN film. Antenna gain and noise temperature were investigated at terahertz frequencies for a HEB embedded in either log-spiral or twin-slot feed antenna. Comparison suggests that at frequencies above 3 THz the spiral feed provides better overall performance. At 1.6 THz, a power of 2.5 µW was required from the local oscillator for optimal operation of the HEB mixer.
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Tong C-YE, Meledin D, Loudkov D, Blundell R, Erickson N, Kawamura J, et al. A 1.5 THz Hot-Electron Bolometer mixer operated by a planar diode based local oscillator. In: IEEE MTT-S Int. Microwave Symp. Digest. Vol 2.; 2003. p. 751–4.
Abstract: We have developed a 1.5 THz superconducting NbN Hot-Electron Bolometer mixer. It is operated by an all-solid-state Local Oscillator comprising of a cascade of 4 planar doublers following an MMIC based W-band power amplifier. The threshold available pump power is estimated to be 1 /spl mu/W.
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Ekström H, Kroug M, Belitsky V, Kollberg E, Olsson H, Goltsman G, et al. Hot electron mixers for THz applications. In: Rolfe EJ, Pilbratt G, editors. Proc. 30th ESLAB.; 1996. p. 207–10.
Abstract: We have measured the noise performance of 35 A thin NbN HEB devices integrated with spiral antennas on antireflection coated silicon substrate lenses at 620 GHz. From the noise measurements we have determined a total conversion gain of the receiver of—16 dB, and an intrinsic conversion of about-10 dB. The IF bandwidth of the 35 A thick NbN devices is at least 3 GHz. The DSB receiver noise temperature is less than 1450 K. Without mismatch losses, which is possible to obtain with a shorter device, and with reduced loss from the beamsplitter, we expect to achieve a DSB receiver noise temperature of less ‘than 700 K.
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Hübers H-W, Semenov A, Richter H, Birk M, Krocka M, Mair U, et al. Terahertz heterodyne receiver with a hot-electron bolometer mixer. In: Wold J, Davidson J, editors. Proc. Far-IR, Sub-mm, and mm Detector Technology Workshop.; 2002.
Abstract: During the past decade major advances have been made regarding low noise mixers for terahertz (THz) heterodyne receivers. State of the art hot-electron-bolometer (HEB) mixers have noise temperatures close to the quantum limit and require less than a µW power from the local oscillator (LO). The technology is now at a point where the performance of a practical receiver employing such mixer, rather than the figures of merit of the mixer itself, are of major concern. We have incorporated a phonon-cooled NbN HEB mixer in a 2.5 THz heterodyne receiver and investigated the performance of the receiver. This yields important information for the development of heterodyne receivers such as GREAT (German receiver for astronomy at THz frequencies aboard SOFIA)[1] and TELIS (Terahertz limb sounder), a balloon borne heterodyne receiver for atmospheric research [2]. Both are currently under development at DLR.
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Hübers H-W, Semenov A, Richter H, Smirnov K, Gol'tsman G, Voronov B. Phonon cooled far-infrared hot electron bolometer mixer [abstract]. In: NASA/ADS.; 2002.
Abstract: Heterodyne receivers for applications in astronomy need quantum-limited sensitivity. At frequencies above 1.4 THz superconducting hot electron bolometers (HEB) can be used to achieve this goal. We present results of the development of a quasi-optical phonon-cooled NbN HEB mixer for GREAT, the German heterodyne receiver for SOFIA. Different mixers with logarithmic spiral and double slot feed antennas have been investigated with respect to their noise temperature, conversion loss, linearity and beam pattern at several frequencies between 0.7 THz and 5.2 THz. At 2.5 THz a double sideband noise temperature of 2200 K was achieved. The conversion loss was 16 dB. The response of the mixer was linear up to 400 K load temperature. This performance was verified by measuring an emission line of methanol at 2.5 THz. The results demonstrate that the NbN HEB is very well suited as a mixer for FIR heterodyne receivers.
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Blundell R, Kawamura JH, Tong CE, Papa DC, Hunter TR, Gol’tsman GN, et al. A hot-electron bolometer mixer receiver for the 680-830 GHz frequency range. In: Proc. 6-th Int. Conf. Terahertz Electron. IEEE; 1998. p. 18–20.
Abstract: We describe a heterodyne receiver designed to operate in the partially transparent atmospheric windows centered on 680 and 830 GHz. The receiver incorporates a niobium nitride thin film, cooled to 4.2 K, as the phonon-cooled hot-electron mixer element. The double sideband receiver noise, measured over the frequency range 680-830 GHz, is typically 700-1300 K. The instantaneous output bandwidth of the receiver is 600 MHz. This receiver has recently been used at the SubMillimeter Telescope, jointly operated by the Steward Observatory and the Max Planck Institute for Radioastronomy, for observations of the neutral carbon and CO spectral lines at 810 GHz and at 806 and 691 GHz respectively. Laboratory measurements on a second mixer in the same test receiver have yielded extended high frequency performance to 1 THz.
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Antipov SV, Vachtomin YB, Maslennikov SN, Smirnov KV, Kaurova NS, Grishina EV, et al. Noise performance of quasioptical ultrathin NbN hot electron bolometer mixer at 2.5 and 3.8 THz. In: Proc. 5-th MSMW. Vol 2. Kharkov, Ukraine; 2004. p. 592–4.
Abstract: To put space-based and airborne heterodyne instruments into operation at frequencies above 1 THz the superconducting NbN hot-electron bolometer (HEB) will be incorporated into heterodyne receiver as a mixer. At frequencies above 1.3 THz the sensitivity of the NbN HEB mixers outperform the one of the Schottky diodes and SIS-mixers, and the receiver noise temperature of the NbN HEB mixers increase with frequency. In this paper we present the results of the noise temperature measurements within one batch of NbN HEB mixers based on 3.5 mn thick superconducting NbN film grown on Si substrate with MgO buffer layer at the LO frequencies 2.5 THz and 3.8 THz.
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Jiang L, Zhang W, Yao QJ, Lin ZH, Li J, Shi SC, et al. Characterization of a quasi-optical NbN superconducting hot-electron bolometer mixer. In: Proc. PIERS. Vol 1.; 2005. p. 587–90.
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolome-ter) mixer measured at 500 GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled bya 4-K close-cycled refrigerator. Its receiver noise temperature and conversion gain are thoroughly investigatedfor different LO pumping levels and dc biases. The lowest receiver noise temperature is found to be approxi-mately 1200 K, and reduced to about 445 K after correcting theloss of the measurement system. The stabilityof the mixer’s IF output power is also demonstrated.
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Hübers H-W, Semenov A, Schubert J, Gol'tsman G, Voronov B, Gershenzon E. Performance of the phonon-cooled hot-electron bolometric mixer between 0.7 THz and 5.2 THz. In: Proc. 8-th Int. Conf. on Terahertz Electronics.; 2000. p. 117–9.
Abstract: We report on the phonon cooled NbN hot electron bolometer as mixer in the terahertz frequency range. Its hybrid antenna consists of a hyperhemispheric silicon lens and a logarithmic-spiral feed antenna. Noise temperatures have been measured between 0.7 THz and 5.2 THz. A quarter wavelength layer of Parylene works as antireflection coating for the silicon lens and reduces the noise temperature by about 30. It was found that the antenna pattern at 2.5 THz is determined by the feed antenna and not by the diameter of the lens.
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