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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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Richter H, Semenov A, Hubers H-W, Smirnov K, Gol’tsman G, Voronov B. Phonon cooled hot-electron bolometric mixer for 1-5 THz. In: Proc. 29th IRMMW / 12th THz.; 2004. p. 241–2.
Abstract: Heterodyne receivers for applications in astronomy and planetary research need quantum limited sensitivity. In instruments which are currently built for SOFIA and Herschel, superconducting hot electron bolometers (HEB) are used to achieve this goal at frequencies above 1.4 THz. In order to optimize the performance for this frequency of hot electron bolometer mixers with different in-plane dimensions and logarithmic-spiral feed antennas have been investigated. Their noise temperatures and beam patterns were measured. Above 3 THz the best performance was achieved with a superconducting bridge of 2.0/spl times/0.2 /spl mu/m/sup 2/ incorporated in a logarithmic spiral antenna. The DSB noise temperatures were 2700 K, 4700 and 6400 K at 3.1 THz, 4.3 THz and 5.2 THz, respectively. The results demonstrate that the NbN HEB is very well suited as a mixer for THz heterodyne receivers up to at least 5 THz.
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Cherednichenko S, Khosropanah P, Adam A, Merkel HF, Kollberg EL, Loudkov D, et al. 1.4- to 1.7-THz NbN hot-electron bolometer mixer for the Herschel space observatory. In: Phillips TG, Zmuidzinas J, editors. Proc. SPIE. Vol 4855. SPIE; 2003. p. 361–70.
Abstract: NbN hot- electron bolometer mixers have reached the level of 10hv/k in terms of the input noise temperature with the noise bandwidth of 4-6 GHz from subMM band up to 2.5 THz. In this paper we discuss the major characteristics of this kind of receiver, i.e. the gain and the noise bandwidth, the noise temperature in a wide RF band, bias regimes and optimisation of RF coupling to the quasioptical mixer. We present the status of the development of the mixer for Band 6 Low for Herschel Telescope.
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Vakhtomin YB, Finkel MI, Antipov SV, Smirnov KV, Kaurova NS, Drakinskii VN, et al. The gain bandwidth of mixers based on the electron heating effect in an ultrathin NbN film on a Si substrate with a buffer MgO layer. J of communications technol & electronics. 2003;48(6):671–5.
Abstract: Measurements of the intermediate frequency band 900 GHz of mixers based on the electron heating effect (EHE) in 2-nm- and 3.5-nm-thick superconducting NbN films sputtered on MgO and Si substrates with buffer MgO layers are presented. A 2-nm-thick superconducting NbN film with a critical temperature of 9.2 K has been obtained for the first time using a buffer MgO layer.
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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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Loudkov D, Khosropanah P, Cherednichenko S, Adam A, MerkeI H, Kollberg E, et al. Broadband fourier transform spectrometer (FTS) measurements of spiral and double-slot planar antennas at THz frequencies. In: Proc. 13th Int. Symp. Space Terahertz Technol.; 2002. p. 373–369.
Abstract: The direct responses of NbN phonon-cooled hot electron bolometer (HEB) mixers, integrated with different planar antennas, are measured, using Fourier Transform Spectrometer (F1S). One spiral antenna and several double slot antennas, designed for 0.6, 1.4, 1.6, 1.8 and 2.5 THz central frequencies, are investigated. The Optimization of the measurement set-up is discussed in terms of the beam splitter and the F11S-to-HEB coupling. The result shows that the spiral antenna is circular polarized and has a bandwidth of about 2 THz. The frequency bands of double slot antennas show some shift from the design values and their relative bandwidth increases by increasing the design frequency. The antenna responses do not depend on the HEB bias point and temperature, as long as the device is in the resistive state.
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Hübers H-W, Semenov A, Richter H, Birk M, Krocka M, Mair U, et al. Terahertz Heterodyn Receiver with a hot-electron bolometer mixer. In: Wolf U, Farhoomand J, McCreight CR, editors. Far-IR, Sub-mm & MM Detector Technology Workshop. NASA; 2002. p. 3–24. (NASA CP).
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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Kawamura J, Tong C-YE, Blundell R, Papa DC, Hunter TR, Patt F, et al. Terahertz-frequency waveguide NbN hot-electron bolometer mixer. IEEE Trans Appl Supercond. 2001;11(1):952–4.
Abstract: We have developed a low-noise waveguide heterodyne receiver for operation near 1 THz using phonon-cooled NbN hot-electron bolometers. The mixer elements are submicron-sized microbridges of 4 nm-thick NbN film fabricated on a quartz substrate. Operating at a bath temperature of 4.2 K, the double-sideband receiver noise temperature is 760 K at 1.02 THz and 1100 K at 1.26 THz. The local oscillator is provided by solid-state sources, and power measured at the source is less than 1 /spl mu/W. The intermediate frequency bandwidth exceeds 2 GHz. The receiver was used to make the first ground-based heterodyne detection of a celestial spectroscopic line above 1 THz.
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Antipov SV, Svechnikov SI, Smirnov KV, Vakhtomin YB, Finkel MI, Goltsman GN, et al. Noise temperature of quasioptical NbN hot electron bolometer mixers at 900 GHz. Physics of Vibrations. 2001;9(4):242–5.
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Svechnikov SI, Antipov SV, Vakhtomin YB, Goltsman GN, Gershenzon EM, Cherednichenko SI, et al. Conversion and noise bandwidths of terahertz NbN hot-electron bolometer mixers. Physics of Vibrations. 2001;9(3):205–10.
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