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Yagoubov, P., Kroug, M., Merkel, H., Kollberg, E., Schubert, J., Hubers, H. W., et al. (1999). Hot electron bolometric mixers based on NbN films deposited on MgO substrates. In Inst. Phys. Conf. Ser. (Vol. 167, pp. 687–690). Barcelona, Spain.
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Semenov, A. D., Hübers, H. –W., Schubert, J., Gol'tsman, G. N., Elantiev, A. I., Voronov, B. M., et al. (2000). Frequency dependent noise temperature of the lattice cooled hot-electron terahertz mixer. In Proc. 11th Int. Symp. Space Terahertz Technol. (pp. 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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Hübers, H. - W., Semenov, A. D., Richter, H., Schubert, J., Hadjiloucas, S., Bowen, J. W., et al. (2001). Antenna pattern of the quasi-optical hot-electron bolometric mixer at terahertz frequencies. In Proc. 12th Int. Symp. Space Terahertz Technol. (pp. 286–296). San Diego, CA, USA.
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Poglitsch, A., Waelkens, C., Geis, N., Feuchtgruber, H., Vandenbussche, B., Rodriguez, L., et al. (2010). The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory. A&A, 518, 12.
Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16×25 pixels, each, and two filled silicon bolometer arrays with 16×32 and 32×64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60-85 μm or 85-125 μm and 125-210 μm, over a field of view of ~1.75'× 3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47â€ × 47â€, resolved into 5×5 pixels, with an instantaneous spectral coverage of ~1500 km s-1 and a spectral resolution of ~175 km s-1. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.
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Schubert, J., Semenov, A., Gol'tsman, G., Hübers, H. - W., Schwaab, G., Voronov, B., et al. (1999). Noise temperature and sensitivity of a NbN hot-electron mixer at frequencies from 0.7 THz to 5.2 THz. In Proc. 10th Int. Symp. Space Terahertz Technol. (pp. 190–199).
Abstract: We report on noise temperature measurements of a NbN phonon-cooled hot-electron bolometric mixer at different bias regimes. The device was a 3 nm thick bridge with in-plane dimensions of 1.7 x 0.2 gm 2 integrated in a complementary logarithmic spiral antenna. Measurements were performed at frequencies ranging from 0.7 THz up 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). Two bias regimes are possible in order to achieve low noise temperatures. But only one of them yields sensitivity fluctuations close to the theoretical limit.
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