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Lobanov, Y. V., Vakhtomin, Y. B., Pentin, I. V., Khabibullin, R. A., Shchavruk, N. V., Smirnov, K. V., et al. (2018). Characterization of the THz quantum cascade laser using fast superconducting hot electron bolometer. EPJ Web Conf., 195, 04004 (1 to 2).
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Ren, Y., Zhang, D. X., Zhou, K. M., Miao, W., Zhang, W., Shi, S. C., et al. (2019). 10.6 μm heterodyne receiver based on a superconducting hot-electron bolometer mixer and a quantum cascade laser. AIP Advances, 9(7), 075307.
Abstract: We report on the development of a heterodyne receiver at mid-infrared wavelength for high-resolution spectroscopy applications. The receiver employs a superconducting NbN hot electron bolometer as a mixer and a room temperature distributed feedback quantum cascade laser operating at 10.6 μm (28.2 THz) as a local oscillator. The stabilization of the heterodyne receiver has been achieved using a feedback loop controlling the output power of the laser. Improved Allan variance times as well as a double sideband receiver noise temperature of 5000 K and a noise bandwidth of 2.8 GHz of the receiver system are demonstrated.
The work is supported in part by the National Key R&D Program of China under Grant 2018YFA0404701, by the CAS program under Grant QYZDJ-SSW-SLH043 and GJJSTD20180003, by the National Natural Science Foundation of China (NSFC) under Grant 11773083, by the “Hundred Talents Program” of the “Pioneer Initiative”, and in part by the CAS Key Lab for Radio Astronomy.
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Semenov, A. D., & Gol’tsman, G. N. (2000). Nonthermal mixing mechanism in a diffusion-cooled hot-electron detector. J. Appl. Phys., 87(1), 502–510.
Abstract: We present an analysis of a diffusion-cooled hot-electron detector fabricated from clean superconducting material with low transition temperature. The distinctive feature of a clean material, i.e., material with large electron mean free path, is a relatively weak inelastic electron scattering that is not sufficient for the establishment of an elevated thermodynamic electron temperature when the detector is subjected to irradiation. We propose an athermal model of a diffusion-cooled detector that relies on suppression of the superconducting energy gap by the actual dynamic distribution of excess quasiparticles. The resistive state of the device is caused by the electric field penetrating into the superconducting bridge from metal contacts. The dependence of the penetration length on the energy gap delivers the detection mechanism. The sources of the electric noise are equilibrium fluctuations of the number of thermal quasiparticles and frequency dependent shot noise. Using material parameters typical for A1, we evaluate performance of the device in the heterodyne regime at terahertz frequencies. Estimates show that the mixer may have a noise temperature of a few quantum limits and a bandwidth of a few tens of GHz, while the required local oscillator power is in the μW range due to ineffective suppression of the energy gap by quasiparticles with high energies.
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Yagoubov, P., Kroug, M., Merkel, H., Kollberg, E., Gol'tsman, G., Svechnikov, S., et al. (1998). Noise temperature and local oscillator power requirement of NbN phonon-cooled hot electron bolometric mixers at terahertz frequencies. Appl. Phys. Lett., 73(19), 2814–2816.
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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Chen, J., Kang, L., Jin, B. B., Xu, W. W., Wu, P. H., Zhang, W., et al. (2008). Properties of terahertz superconducting hot electron bolometer mixers. Int. J. Terahertz Sci. Technol., 1(1), 37–41.
Abstract: A quasi-optical superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixer has been fabricated and measured in the terahertz (THz) frequency range of 0.5~2.52 THz. A receiver noise temperature of 2000 K at 2.52 THz has been obtained for the mixer without corrections. Also, the effect of a Parylene C anti-reflection (AR) coating on the silicon (Si) lens has been studied.
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Jiang, L., Antipov, S. V., Voronov, B. M., Gol'tsman, G. N., Zhang, W., Li, N., et al. (2007). Characterization of the performance of a quasi-optical NbN superconducting HEB mixer. IEEE Trans. Appl. Supercond., 17(2), 395–398.
Abstract: In this paper we focus mainly on the investigation of the performance of a quasi-optical (planar log-spiral antenna) phonon-cooled NbN superconducting hot electron bolometer (HEB) mixer, which is cryogenically cooled by a close-cycled 4-K cryocooler, at 500 and 850 GHz frequency bands. The mixer's noise performance, stability of IF output power, and local oscillator (LO) power requirement are characterized for three NbN superconducting HEB devices of different sizes. The transmission characteristics of Mylar and Zitex films with incidence waves of an elliptical polarization are also examined by measuring the mixer's noise temperature. The lowest receiver noise temperatures (with no corrections) of 750 and 1100 K are measured at 500 and 850 GHz, respectively. Experimental results also demonstrate that the bigger the HEB device is, the higher the stability of IF output power becomes.
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Kawamura, J., Blundell, R., Tong, C. - Y. E., Papa, D. C., Hunter, T. R., Paine, S. N., et al. (2000). Superconductive hot-electron-bolometer mixer receiver for 800-GHz operation. IEEE Trans. Microw. Theory Techn., 48(4), 683–689.
Abstract: In this paper, we describe a superconductive hot-electron-bolometer mixer receiver designed to operate in the partially transmissive 350-μm atmospheric window. The receiver employs an NbN thin-film microbridge as the mixer element, in which the main cooling mechanism of the hot electrons is through electron-phonon interaction. At a local-oscillator frequency of 808 GHz, the measured double-sideband receiver noise temperature is TRX=970 K, across a 1-GHz intermediate-frequency bandwidth centered at 1.8 GHz. We have measured the linearity of the receiver and the amount of local-oscillator power incident on the mixer for optimal operation, which is PLO≈1 μW. This receiver was used in making observations as a facility instrument at the Heinrich Hertz Telescope, Mt. Graham, AZ, during the 1998-1999 winter observing season.
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Ekstörm, H., Kollberg, E., Yagoubov, P., Gol'tsman, G., Gershenzon, E., & Yngvesson, S. (1997). Gain and noise bandwidth of NbN hot-electron bolometric mixers. Appl. Phys. Lett., 70(24), 3296–3298.
Abstract: We have measured the noise performance and gain bandwidth of 35 Å thin NbN hot-electron mixers integrated with spiral antennas on silicon substrate lenses at 620 GHz. The best double-sideband receiver noise temperature is less than 1300 K with a 3 dB bandwidth of ≈5 GHz. The gain bandwidth is 3.2 GHz. The mixer output noise dominated by thermal fluctuations is 50 K, and the intrinsic conversion gain is about −12 dB. Without mismatch losses and excluding the loss from the beamsplitter, we expect to achieve a receiver noise temperature of less than 700 K.
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Hübers, H. - W., Semenov, A., Holldack, K., Schade, U., Wüstefeld, G., & Gol’tsman, G. (2005). Time domain analysis of coherent terahertz synchrotron radiation. Appl. Phys. Lett., 87(18), 184103 (1 to 3).
Abstract: The time structure of coherent terahertz synchrotron radiation at the electron storage ring of the Berliner Elektronensynchrotron und Speicherring Gesellschaft has been analyzed with a fast superconducting hot-electron bolometer. The emission from a single bunch of electrons was found to last ∼1500ps at frequencies around 0.4THz, which is much longer than the length of an electron bunch in the time domain (∼5ps). It is suggested that this is caused by multiple reflections at the walls of the beam line. The quadratic increase of the power with the number of electrons in the bunch as predicted for coherent synchrotron radiation and the transition from stable to bursting radiation were determined from a single storage ring fill pattern of bunches with different populations.
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Baubert, J., Salez, M., Merkel, H., Pons, P., Cherednichenko, S., Lecomte, B., et al. (2005). IF gain bandwidth of membrane-based NbN hot electron bolometers for SHAHIRA. IEEE Trans. Appl. Supercond., 15(2), 507–510.
Abstract: SHAHIRA (Submm Heterodyne Array for HIgh-speed Radio Astronomy) is a project supported by the European Space Agency (ESA) and is designed to fly on the SOFIA observatory. A quasi-optic design has been chosen for 2.5/2.7 THz and 4.7 THz, for hydroxyde radical OH, deuterated hydrogen HD and neutral atomic oxygen OI lines observations. Hot electron bolometers (HEBs) have been processed on 1 /spl mu/m thick SiO/sub 2//Si/sub 3/N/sub 4/ stress-less membranes. In this paper we analyse the intermediate frequency (IF) gain bandwidth from the theoretical point of view, and compare it to measurements.
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Semenov, A. D., Hübers, H. - W., Richter, H., Birk, M., Krocka, M., Mair, U., et al. (2002). 2.5 THz heterodyne receiver with NbN hot-electron-bolometer mixer. Phys. C: Supercond., 372-376, 448–453.
Abstract: We describe a 2.5 THz heterodyne receiver for applications in astronomy and atmospheric research. The receiver employs a superconducting NbN phonon-cooled hot-electron-bolometer mixer and an optically pumped far-infrared gas laser as local oscillator. 2200 K double sideband mixer noise temperature was measured at 2.5 THz across a 1 GHz intermediate frequency bandwidth centred at 1.5 GHz. The total conversion losses were 17 dB. The mixer response was linear at load temperatures smaller than 400 K. The receiver was tested in the laboratory environment by measuring the methanol line in emission. Observed pressure broadening confirms the true heterodyne detection regime of the mixer.
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Cherednichenko, S., Kroug, M., Merkel, H., Khosropanah, P., Adam, A., Kollberg, E., et al. (2002). 1.6 THz heterodyne receiver for the far infrared space telescope. Phys. C: Supercond., 372-376, 427–431.
Abstract: A low noise heterodyne receiver is being developed for the terahertz range using a phonon-cooled hot-electron bolometric mixer based on 3.5 nm thick superconducting NbN film. In the 1–2 GHz intermediate frequency band the double-sideband receiver noise temperature was 450 K at 0.6 THz, 700 K at 1.6 THz and 1100 K at 2.5 THz. In the 3–8 GHz IF band the lowest receiver noise temperature was 700 K at 0.6 THz, 1500 K at 1.6 THz and 3000 K at 2.5 THz while it increased by a factor of 3 towards 8 GHz.
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Hübers, H. - W., Schubert, J., Krabbe, A., Birk, M., Wagner, G., Semenov, A., et al. (2001). Parylene anti-reflection coating of a quasi-optical hot-electron-bolometric mixer at terahertz frequencies. Infrared Physics & Technology, 42(1), 41–47.
Abstract: Parylene C was investigated as anti-reflection coating for silicon at terahertz frequencies. Measurements with a Fourier-transform spectrometer show that the transmittance of pure silicon can be improved by about 30% when applying a layer of Parylene C with a quarter wavelength optical thickness. The 10% bandwidth of this coating extends from 1.5 to 3 THz for a center frequency of 2.3–2.5 THz, where the transmittance is constant. Heterodyne measurements demonstrate that the noise temperature of a hot-electron-bolometric mixer can be reduced significantly by coating the silicon lens of the hybrid antenna with a quarter wavelength Parylene C layer. Compared to the same mixer with an uncoated lens the improvement is about 30% at a frequency of 2.5 THz.
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Hajenius, M., Baselmans, J. J. A., Gao, J. R., Klapwijk, T. M., de Korte, P. A. J., Voronov, B., et al. (2004). Low noise NbN superconducting hot electron bolometer mixers at 1.9 and 2.5 THz. Supercond. Sci. Technol., 17(5), S224–S228.
Abstract: NbN phonon-cooled hot electron bolometer mixers (HEBs) have been realized with negligible contact resistance between the bolometer itself and the contact structure. Using a combination of in situ cleaning of the NbN film and the use of an additional superconducting interlayer of a 10 nm NbTiN layer between the Au of the contact structure and the NbN film superior noise temperatures have been obtained as low as 950 K at 2.5 THz and 750 K at 1.9 THz. Here we address in detail the DC characterization of these devices, the interface transparencies between the bolometers and the contacts and the consequences of these factors on the mixer performance.
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Gol'tsman, G. N., Karasik, B. S., Okunev, O. V., Dzardanov, A. L., Gershenzon, E. M., Ekstrom, H., et al. (1995). NbN hot electron superconducting mixers for 100 GHz operation. IEEE Trans. Appl. Supercond., 5(2), 3065–3068.
Abstract: NbN is a promising superconducting material for hot-electron superconducting mixers with an IF bandwidth larger than 1 GHz. In the 1OO GHz frequency range, the following parameters were obtained for 50 /spl Aring/ thick NbN films at 4.2 K: receiver noise temperature (DSB) /spl sim/1000 K; conversion loss /spl sim/10 dB; IF bandwidth /spl sim/1 GHz; and local oscillator power /spl sim/1 /spl mu/W. An increase of the critical current of the NbN film, increased working temperature, and a better mixer matching may allow a broader IF bandwidth up to 2 GHz, reduced conversion losses down to 3-5 dB and a receiver noise temperature (DSB) down to 200-300 K.
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