Maslennikov, S. N., Morozov, D. V., Ozhegov, R. V., Smirnov, K. V., Okunev, O. V., & Gol’tsman, G. N. (2004). Imaging system for submillimeter wave range based on AlGaAs/GaAs hot electron bolometer mixers. In Proc. 5-th MSMW (Vol. 2, pp. 558–560).
Abstract: Electromagnetic radiation of the submillimeter (SMM) range is dispersed and absorbed significantly less than infrared (IR) radiation when passing through different objects. That is the reason for the development of an SMM imaging system. In this paper, we discuss the design of an SMM heterodyne imager, based on a matrix of AlGaAs/GaAs heterostructure hot electron bolometer mixers (HEB) with relatively high (about 77 K) operating temperature. The predicted double side band (DSB) noise temperature is about 1000 K and optimal local oscillator (LO) power is about 1 /spl mu/W for such mixers, which seems to be quite prospective for an SMM heterodyne imager.
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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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Cherednichenko, S., Kroug, M., Yagoubov, P., Merkel, H., Kollberg, E., Yngvesson, K. S., et al. (2000). IF bandwidth of phonon cooled HEB mixers made from NbN films on MgO substrates. In Proc. 11th Int. Symp. Space Terahertz Technol. (pp. 219–227).
Abstract: An investigation of gain and noise bandwidth of phonon-cooled hot-electron bolometric (HEB) mixers is presented. The radiation coupling to the mixers is quasioptical through either a spiral or twin-slot antenna. A maximum gain bandwidth of 4.8 GHz is obtained for mixers based on a 3.5 nm thin NbN film with Tc= 10 K. The noise bandwidth is 5.6 GHz, at the moment limited by parasitic elements in the, device mount fixture. At 0.65 THz the DSB receiver noise temperature is 700-800 К in the IF band 1-2 GHz, and 1150-2700 К in the band 3.5-7 GHz.
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Benz, A. O., Bruderer, S., van Dishoeck, E. F., Stäuber, P., Wampfler, S. F., Melchior, M., et al. (2010). Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system. Astron. Astrophys., 521, L35 (1 to 5).
Abstract: Context. Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays.
Aims. We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation.
Methods. W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (2500 s) in 8 spectral regions.
Results. The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J = 1–0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds.
Conclusions. The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.
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Cherednichenko, S., Drakinskiy, V., Berg, T., Khosropanah, P., & Kollberg, E. (2008). Hot-electron bolometer terahertz mixers for the Herschel Space Observatory. Rev. Sci. Instrum., 79, 034501.
Abstract: We report on low noise terahertz mixers(1.4–1.9THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5to2.5THz, with 30GHz resolution) and also by measuring the mixernoise temperature at a limited number of discrete frequencies. The lowest mixernoise temperature recorded was 750K [double sideband (DSB)] at 1.6THz and 950KDSB at 1.9THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4–4.8GHz, the mixernoise temperature was 1100KDSB at 1.6THz and 1450KDSB at 1.9THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200–500nW range.
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Tretyakov, I. V., Finkel, M. I., Ryabchun, S. A., Kardakova, A. I., Seliverstov, S. V., Petrenko, D. V., et al. (2014). Hot-electron bolometer mixers with in situ contacts. Radiophys. Quant. Electron., 56(8-9), 591–598.
Abstract: We report on the latest achievements in the development of superconducting hot-electron bolometer (HEB) mixers for terahertz superheterodyne receivers. We consider application ranges of such receivers and requirements for the basic characteristics of the mixers. Main features of the mixers, such as noise temperature, gain bandwidth, noise bandwidth, and required local-oscillator power, have been improved significantly over the past few years due to intense research work, both in terms of the element fabrication quality and in terms of understanding of the physics of the processes occurring in the HEB mixers. Contacts between the superconducting bridge and the planar antenna play a key role in the mixer operation. Improvement of the quality of the contacts leads simultaneously to a decrease in the noise temperature and an increase in the gain bandwidth of a mixer.
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Yagoubov, P., Hübers, H. - W., Gol’tsman, G., Semenov, A., Gao, J., Hoogeveen, R., et al. (2001). Hot-electron bolometer mixers – technology for far-infrared heterodyne instruments in future atmospheric chemistry missions. In S. Buehler, & Berlin (Eds.), Proc. 3rd Int. Symp. Submillimeter Wave Earth Observation From Space (pp. 57–69). Logos-Verlag.
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Gershenzon, E. M., & Gol'tsman, G. N. (1993). Hot electron superconductive mixers. In Proc. 4th Int. Symp. Space Terahertz Technol. (pp. 618–622).
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Karasik, B. S., Gol'tsman, G. N., Voronov, B. M., Svechnikov, S. I., Gershenzon, E. M., Ekstrom, H., et al. (1995). Hot electron quasioptical NbN superconducting mixer. IEEE Trans. Appl. Supercond., 5(2), 2232–2235.
Abstract: Hot electron superconductor mixer devices made of thin NbN films on SiO/sub 2/-Si/sub 3/N/sub 4/-Si membrane have been fabricated for 300-350 GHz operation. The device consists of 5-10 parallel strips each 5 /spl mu/m long by 1 /spl mu/m wide which are coupled to a tapered slot-line antenna. The I-V characteristics and position of optimum bias point were studied in the temperature range 4.5-8 K. The performance of the mixer at higher temperatures is closer to that predicted by theory for uniform electron heating. The intermediate frequency bandwidth versus bias has also been investigated. At the operating temperature 4.2 K a bandwidth as wide as 0.8 GHz has been measured for a mixer made of 6 nm thick film. The bandwidth tends to increase with operating temperature. The performance of the NbN mixer is expected to be better for higher frequencies where the absorption of radiation should be more uniform.
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Kollberg, E. L., Gershenzon, E., Goltsman, G., & Yngvesson, K. S. (1992). Hot electron mixers, the potential competition. In Proc. ESA Symp. on Photon Detectors for Space Instrumentation (pp. 201–206).
Abstract: There is an urgent need in radio astronomy for low noise heterodyne receivers for frequencies above about 500 GHz. It is not certain that mixers based on superconducting quasiparticle tunnelling (SIS mixers) may turn out to be the answer to this need. In order to try to find an alternative way for realizing low noise heterodyne receivers for submillimeter waves, so called hot electron bolometric effects for mixing are now being investigated. Two basically different approaches are tried, one based on semiconductors and one on superconductors. Both methods are briefly discussed in this overview paper.
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