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Burke PJ, Schoelkopf RJ, Prober DE, Skalare A, Karasik BS, Gaidis MC, et al. Mixing and noise in diffusion and phonon cooled superconducting hot-electron bolometers. J. Appl. Phys.. 1999;85(3):1644–53.
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Burke PJ, Schoelkopf RJ, Prober DE, Skalare A, Karasik BS, Gaidis MC, et al. Spectrum of thermal fluctuation noise in diffusion and phonon cooled hot-electron mixers. Appl Phys Lett. 1998;72(12):1516–8.
Abstract: A systematic study of the intermediate frequency noise bandwidth of Nb thin-film superconducting hot-electron bolometers is presented. We have measured the spectrum of the output noise as well as the conversion efficiency over a very broad intermediate frequency range (from 0.1 to 7.5 GHz) for devices varying in length from 0.08 μm to 3 μm. Local oscillator and rf signals from 8 to 40 GHz were used. For a device of a given length, the spectrum of the output noise and the conversion efficiency behave similarly for intermediate frequencies less than the gain bandwidth, in accordance with a simple thermal model for both the mixing and thermal fluctuation noise. For higher intermediate frequencies the conversion efficiency decreases; in contrast, the noise decreases but has a second contribution which dominates at higher frequency. The noise bandwidth is larger than the gain bandwidth, and the mixer noise is low, between 120 and 530 K (double side band).
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Chattopadhyay G, Rice F, Miller D, LeDuc HG, Zmuidzinas J. A 530-GHz balanced mixer. IEEE Microw. and Guided Wave Lett.. 1999;9(11):467–9.
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Hartogh P, Jarchow C, Lellouch E, de Val-Borro M, Rengel M, Moreno R, et al. Herschel/HIFI observations of Mars: First detection of O2 at submillimetre wavelengths and upper limits on HCl and H2O2. Astron. Astrophys.. 2010;521:L49.
Abstract: We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H2O2), and molecular oxygen (O2) in the Martian atmosphere performed on 13 and 16 April 2010 (Ls ~ 77°). We derived a constant volume mixing ratio of 1400 ± 120 ppm for O2 and determined upper limits of 200 ppt for HCl and 2 ppb for H2O2. Radiative transfer model calculations indicate that the vertical profile of O2 may not be constant. Photochemical models determine the lowest values of H2O2 to be around Ls ~ 75° but overestimate the volume mixing ratio compared to our measurements.
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Karpov A, Miller D, Rice F, Zmuidzinas J, Stern JA, Bumble B, et al. Low noise 1.2 THz SIS receiver. In: Jet Propulsion Laboratory CIit.u.t.e of T, editor. Proc. 12th Int. Symp. Space Terahertz Technol. San Diego, CA, USA; 2001. p. 21–2.
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Karpov A, Miller D, Rice F, Stern JA, Bumble B, LeDuc HG, et al. Development of 1.25 THz SIS mixer for Herschel Space Observatory. In: Zmuidzinas J, Holland WS, editors. Proc. SPIE. Vol 6275.; 2006. 62751.
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Karpov A, Miller D, Stern JA, Bumble B, LeDuc HG, Zmuidzinas J. Broadband SIS mixer for 1 THz Band. In: Proc. 20th Int. Symp. Space Terahertz Technol.; 2009. p. 35.
Abstract: We report the development of a low noise and broadband SIS mixer aimed for 1 THz channel of the Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver (CASIMIR), designed for the Stratospheric Observatory for Far Infrared Astronomy, (SOFIA). The mixer uses an array of 0.24 µm² Nb/Al-AlN/NbTiN SIS junctions with critical current density of 30-50 KA/cm². The junctions are shaped in order to optimize the suppression of the Josephson DC currents. We are using a double slot planar antenna to couple the mixer chip with the telescope beam. The RF matching microcircuit is made using Nb and gold films. The mixer IF circuit is designed to cover 4 – 8 GHz band. A test receiver with the new mixer has a low noise operation in a 0.87 – 1.12 THz band. The minimum DSB receiver noise measured at 1 THz is 260 K (Y=1.64), apparently the lowest reported up to date. The receiver noise corrected for the loss in the LO injection beam splitter and in the cryostat window is 200 K. The combination of a broad operation band of about 250 GHz with a low receiver noise is making the new mixer a useful element for application at SOFIA. We will discuss the prospective of a further improvement of the sensitivity and extension of the upper frequency of operation of SIS mixer.
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Kenyon M, Day PK, Bradford CM, Bock JJ, Leduc HG. Background-limited membrane-isolated TES bolometers for far-IR/submillimeter direct-detection spectroscopy. Nucl. Instr. & Meth. Phys. Res. A. 2006;559:456–8.
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Skalare A, McGrath WR, Echternach PM, Leduc HG, Siddiqi I, Verevkin A, et al. Aluminum hot-electron bolometer mixers at submillimeter wavelengths. IEEE Trans. Appl. Supercond.. 2001;11(1):641–4.
Abstract: Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 Ω down to about 9 Ω per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 μm long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies.
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Tong CYE, Blundell R, Paine S, Papa DC, Kawamura J, Stern J, et al. Design and characterization of a 250-350 GHz fixed-tuned superconductor-insulator-insulator receiver. IEEE Trans. Microw. Theory Techn.. 1996;44(9):1548–56.
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