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Ryabchun, S. A., Tretyakov, I. V., Finkel, M. I., Maslennikov, S. N., Kaurova, N. S., Seleznev, V. A., et al. (2009). NbN phonon-cooled hot-electron bolometer mixer with additional diffusion cooling. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 151–154). Charlottesville, USA.
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Рябчун, С. А. (2009). Широкополосные высокостабильные терагерцовые смесители на горячих электронах из тонких сверхпроводниковых пленок NbN. Ph.D. thesis, , .
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Karpov, A., Miller, D., Stern, J. A., Bumble, B., LeDuc, H. G., & Zmuidzinas, J. (2009). Broadband SIS mixer for 1 THz Band. In Proc. 20th Int. Symp. Space Terahertz Technol. (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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Uzawa, Y., Kojima, T., Kroug, M., Takeda, M., Candotti, M., Fujii, Y., et al. (2009). Development of the 787-950 GHz ALMA band 10 cartridge. In Proc. 20th Int. Symp. Space Terahertz Technol. (p. 12).
Abstract: We are developing the Atacama Large Millimeter/Submillimeter Array (ALMA) Band 10 (787-950 GHz) receiver cartridge. The incoming beam from the 12-m antenna is reflected by a pair of two ellipsoidal mirrors placed in the cartridge, and then split into two orthogonal polarizations by a free-standing wire-grid. Each beam enters a corrugated feed horn attached to a double-side-band (DSB) mixer block. The mixer uses a full-height waveguide and an NbTiN- or NbN-based superconductor-insulator-superconductor (SIS) mixer chip. We are testing the following three types of mixer chips: 1) Nb SIS junctions + NbTiN/SiO2/Al tuning circuits on a quartz substrate, 2) Nb SIS junctions + NbN/SiO2/Al tuning circuits on an MgO substrate, and 3) NbN SIS junctions + NbN or NbTiN tuning circuits on an MgO substrate. The IF system uses a 4-12-GHz cooled low-noise InP-based MMIC amplifier developed by Caltech. So far, the type 1) has shown the best performance. At LO frequencies from 800 to 940 GHz, the mixer noise temperatures measured by using the standard Y-factor method were below 240 K at an operating physical temperature of 4 K. The lowest noise temperature, 169 K, was obtained at the center frequency of the band 10, as designed. These well-developed technologies will be implemented in the band 10 cartridge to achieve the ALMA specifications.
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Billade, B., Belitsky, V., Pavolotsky, A., Lapkin, I., & Kooi, J. (2009). ALMA band 5 (163-211 GHz) sideband separation mixer. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 19–23).
Abstract: We present the design of ALMA Band 5 sideband separation SIS mixer and experimental results for the double side band mixer and first measurement results 2SB mixer. In this mixer, the LO injection circuitry is integrated on the mixer substrate using a directional coupler, combining microstrip lines with slot-line branches in the ground plane. The isolated port of the LO coupler is terminated by wideband floating elliptical termination. The mixer employs two SIS junctions with junction area of 3 µm² each, in the twin junction configuration, followed by a quarter wave transformer to match the RF probe. 2SB mixer uses two identical but mirrored chips, whereas each DSB mixer has the same end-piece configuration. The 2S mixer has modular design such that DSB mixers are measured independently and then integrated into 2SB simply by placing around the middle piece. Measurements of the DSB mixer show noise temperature of around 40K over the entire band. 2SB mixer is not fully characterized yet, however, preliminary measurement indicates SSB (un-corrected) noise temperature of 80K.
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Li, C. - T., Chen, T. - J., Ni, T. - L., Lu, W. - C., Chiu, C. - P., Chen, C. - W., et al. (2009). Development of SIS mixers for SMA 400-520 GHz band. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 24–30).
Abstract: SIS junction mixers were developed for SMA 400-520 GHz band. The results show receiver noise temperature around 100 K across the band, with noise contribution from RF loss and IF estimated to be around 50 K and 20K, respectively. Two schemes were used to tune out junction's parasitic capacitance. When a parallel inductor is employed, the input impedance is close to Rn, which facilitates impedance matching between the junction and the waveguide probe. Waveguide probes were designed to achieve a low feed-point impedance to match to the junction resistance. Optimum embedding impedances for lower receiver noise temperature were investigated. Performances of two schemes and composition of receiver noise were also discussed.
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Jackson, B. D., Hesper, R., Adema, J., Barkhof, J., Baryshev, A. M., Zijlstra, T., et al. (2009). Series production of state-of-the-art 602-720 GHz SIS receivers for band 9 of ALMA. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 7–11).
Abstract: The Atacama Large Millimeter/Sub-millimeter Array (ALMA) requires the development and production of 73 state-of-the-art receivers for the 602-720 GHz range – the ALMA Band 9 cartridges. Development and pre-production of the first 8 cartridges was completed between 2003 and 2008, resulting in a cartridge design that meets the project's challenging requirements. The cartridge design remains essentially unchanged for production, while the production and test processes developed during pre-production have been fine-tuned to address the biggest new challenge for this phase – ramping up production to a rate of 2 cartridges per month over 2009-2012.
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Risacher, C., Meledin, D., Belitsky, V., & Bergman, P. (2009). First 1.3 THz observations at the APEX telescope. In Proc. 20th Int. Symp. Space Terahertz Technol. (pp. 54–61).
Abstract: The Atacama Pathfinder EXperiment (APEX) 12m telescope is operating on the Llano Chajnantor, Chile, since 2003 and a set of state of the art sub-millimeter receivers have been installed for frequencies spanning from 150 GHz to 1500 GHz. In 2008, a balanced 1.3 THz Hot Electron Bolometer (HEB) receiver was installed for the atmospheric window 1250-1380 GHz. This instrument is part of a 4-channel receiver cryostat with the other channels being 211-275 GHz, 275-370 GHz and 380-500 GHz Sideband Separating (SSB) SIS receivers. This paper presents the first observations obtained so far with the 1.3 THz band during its first months of operation. The sky measurements were taken during opportunistic commissioning and science verification phases, when the weather conditions were sufficiently good with a Precipitable Water Vapor (PWV) below 0.25 mm, which was the case only a few nights during these months. We present the first observations of the molecular transition CO J=(11-10) line on different sources such as Orion-FIR4, CW-Leo and SgrB2(M). We describe the many challenges and difficulties encountered for achieving successful THz observations from a large sub-millimeter ground-based telescope.
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Sekine, N., & Hosako, I. (2009). Intensity modulation of terahertz quantum cascade lasers under external light injection. Appl. Phys. Lett., 95, 201106(1–3).
Abstract: We investigated the light-current characteristics of terahertz (THz) quantum cascade lasers under external light injection, which excites interband transitions in the active materials. It was found that the amount of reduction in the THz power was constant for all injection currents above threshold, and the dependence of the reduction amount on the wavelength of the external light was observed to show a resonancelike feature. The dominant intensity modulation mechanism was found to be the loss change caused by interband transitions in the active region. Further, the effective coupling efficiency plays an important role in the intensity modulation.
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Zhizhon, Y., & Majedi, H. A. (2009). Optoelectronic mixing in the NbN superconducting nanowire single photon detectors. In Proc. SPIE (Vol. 3786, 9).
Abstract: In this paper, we present our experimental results on the electrically pumped optoelectronic mixing effect exhibited in a niobium nitride (NbN) superconducting nanowire. The experimental setup in order to test the mixer has been reported in detail. This superconductive nanowire optoelectronic mixer demonstrates photodetection and mixing in an integrated manner. We have explored both effects under a great variety of external conditions, such as temperature and bias current, in order to seek potential ways toward quantum optoelectronic detection and mixing by such nanowire device.
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