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Smirnov AV, Larionov PA, Finkel MI, Maslennikov SN, Voronov BM, Gol'tsman GN. NbZr films for THz phonon-cooled HEB mixers. In: Proc. 19th Int. Symp. Space Terahertz Technol. Groningen, Netherlands; 2008. p. 44–7.
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Baselmans J, Kooi J, Baryshev A, Yang ZQ, Hajenius M, Gao JR, et al. Full characterization of small volume NbN HEB mixers for space applications. In: Proc. 16th Int. Symp. Space Terahertz Technol. Göteborg, Sweden; 2005. p. 457–62.
Abstract: NbN phonon cooled HEB’s are one of the most promising bolometer mixer technologies for (near) future (space) applications. Their performance is usually quantified by mea- suring the receiver noise temperature at a given IF frequency, usually around 1 – 2 GHz. However, for any real applications it is vital that one fully knows all the relevant properties of the mixer, including LO power, stability, direct detection, gain bandwidth and noise bandwidth, not only the noise temperature at low IF frequencies. To this aim we have measured all these parameters at the optimal operating point of one single, small volume quasioptical NbN HEB mixer. We find a minimum noise temperature of 900 K at 1.46 THz. We observe a direct detection effect indicated by a change in bias current when changing from a 300 K hot load to a 77 K cold load. Due to this effect we overestimate the noise temperature by about 22% using a 300 K hot load and a 77 K cold load. The LO power needed to reach the optimal operating point is 80 nW at the receiver lens front, 59 nW inside the NbN bridge. However, using the isothermal technique we find a power absorbed in the NbN bridge of 25 nW, a difference of about a factor 2. We obtain a gain bandwidth of 2.3 GHz and a noise bandwidth of 4 GHz. The system Allan time is about 1 sec. in a 50 MHz spectral bandwidth and a deviation from white noise integration (governed by the radiometer equation) occurs at 0.2 sec., which implies a maximum integration time of a few seconds in a 1 MHz bandwidth spectrometer.
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Finkel MI, Maslennikov SN, Vachtomin YB, Svechnikov SI, Smirnov KV, Seleznev VA, et al. Hot electron bolometer mixer for 20 – 40 THz frequency range. In: Proc. 16th Int. Symp. Space Terahertz Technol. Göteborg, Sweden; 2005. p. 393–7.
Abstract: The developed HEB mixer was based on a 5 nm thick NbN film deposited on a GaAs substrate. The active area of the film was patterned as a 30×20 μm 2 strip and coupled with a 50 Ohm coplanar line deposited in situ. An extended hemispherical germanium lens was used to focus the LO radiation on the mixer. The responsivity of the mixer was measured in a direct detection mode in the 25÷64 THz frequency range. The noise performance of the mixer and the directivity of the receiver were investigated in a heterodyne mode. A 10.6 μm wavelength CW CO 2 laser was utilized as a local oscillator.
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Maslennikov SN, Finkel MI, Antipov SV, Polyakov SL, Zhang W, Ozhegov R, et al. Spiral antenna coupled and directly coupled NbN HEB mixers in the frequency range from 1 to 70 THz. In: Proc. 17th Int. Symp. Space Terahertz Technol. Paris, France; 2006. p. 177–9.
Abstract: We investigate both antenna coupled and directly coupled HEB mixers at several LO frequencies within the range of 2.5 THz to 70 THz. H20 (2.5+10.7 THz), and CO2 (30 THz) gas discharge lasers are used as the local oscillators. The noise temperature of antenna coupled mixers is measured at LO frequencies of 2.5 THz, 3.8 THz, and 30 THz. The results for both antenna coupled and directly coupled mixer types are compared. The devices with in—plane dimensions of 5x5 ,um 2 are pumped by LO radiation at 10.7 THz. The directly coupled HEB demonstrates nearly flat dependence of responsivity on frequency in the range of 25+64 THz.
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Gol'tsman G, Korneev A, Minaeva O, Antipov A, Divochiy A, Kaurova N, et al. Middle-infrared to visible-light ultrafast superconducting single-photon detector. In: Proc. ASC. Seattle; 2006.
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