Kawamura J, Blundell R, Tong C-YE, Gol'tsman G, Gershenzon E, Voronov B, et al. Phonon-cooled NbN HEB mixers for submillimeter wavelengths. In: Proc. 8th Int. Symp. Space Terahertz Technol.; 1997. p. 23–8.
Abstract: The noise performance of receivers incorporating NbN phonon-cooled superconducting hot electron bolometric mixers is measured from 200 GHz to 900 GHz. The mixer elements are thin-film (thickness — 4 nm) NbN with —5 to 40 pm area fabricated on crystalline quartz sub- strates. The receiver noise temperature from 200 GHz to 900 GHz demonstrates no unexpected degradation with increasing frequency, being roughly TRx ,; 1-2 K The best receiver noise temperatures are 410 K (DSB) at 430 GHz, 483 K at 636 GHz, and 1150 K at 800 GHz.
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Gerecht E, Musante CF, Jian H, Yngvesson KS, Dickinson J, Waldman J, et al. Measured results for NbN phonon-cooled hot electron bolometric mixers at 0.6-0.75 THz, 1.56 THz, and 2.5 THz. In: Proc. 9th Int. Symp. Space Terahertz Technol.; 1998. p. 105–14.
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Yagoubov P, Kroug M, Merkel H, Kollberg E, Schubert J, Hubers HW, et al. Hot electron bolometric mixers based on NbN films deposited on MgO substrates. In: Inst. Phys. Conf. Ser. Vol 167. Barcelona, Spain; 1999. p. 687–90.
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Schubert J, Semenov A, Gol'tsman G, Hübers H-W, Schwaab G, Voronov B, et al. Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz. Supercond. Sci. Technol.. 1999;12(11):748–50.
Abstract: We report on noise temperature measurements of an NbN phonon-cooled hot-electron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7 × 0.2 µm2 and 0.9 × 0.2 µm2 integrated in a complementary logarithmic-spiral antenna. Measurements were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 8800 K (5.2 THz).
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Semenov AD, Hübers H–W, Schubert J, Gol'tsman GN, Elantiev AI, Voronov BM, et al. Frequency dependent noise temperature of the lattice cooled hot-electron terahertz mixer. In: Proc. 11th Int. Symp. Space Terahertz Technol.; 2000. p. 39–48.
Abstract: We present the measurements and the theoretical model on the frequency dependent noise temperature of a lattice cooled hot electron bolometer (HEB) mixer in the terahertz frequency range. The experimentally observed increase of the noise temperature with frequency is a cumulative effect of the non-uniform distribution of the high frequency current in the bolometer and the charge imbalance, which occurs near the edges of the normal domain and contacts with normal metal. In addition, we present experimental results which show that the noise temperature of a HEB mixer can be reduced by about 30% due to a Parylene antireflection coating on the Silicon hyperhemispheric lens.
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