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Baselmans, J. J. A., Baryshev, A., Reker, S. F., Hajenius, M., Gao, J. R., Klapwijk, T. M., et al. (2005). Direct detection effect in small volume hot electron bolometer mixers. Appl. Phys. Lett., 86(16), 163503 (1 to 3).
Abstract: We measure the direct detection effect in a small volume (0.15μm×1μm×3.5nm)(0.15μm×1μm×3.5nm) quasioptical NbN phonon cooled hot electronbolometermixer at 1.6THz1.6THz. We find that the small signal sensitivity of the receiver is underestimated by 35% due to the direct detection effect and that the optimal operating point is shifted to higher bias voltages when using calibration loads of 300K300K and 77K77K. Using a 200GHz200GHzbandpass filter at 4.2K4.2K the direct detection effect virtually disappears. This has important implications for the calibration procedure of these receivers in real telescope systems.
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Maslennikov, S., Antipov, S., Shishkov, A., Svechnikov, S., Voronov, B., Smirnov, K., et al. (2002). NbN HEB mixer noise temperature measurements with hot/cold load mounted inside the helium cryostat at 300 GHz. In Proc. Int. Student Seminar on Microwave Appl. of Novel Physical Phenomena supported by IEEE. St.-Petersburg: LETI.
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Maslennikov, S., Vachtomin, Y., Antipov, S., Smirnov, K., Kaurova, N., Grishina, E., et al. (2004). NbN HEB mixers for frequencies of 2.5 and 3.8 THz. In Proc. Tenth All-Russian sceintific conference of student-physicists and young sceintists (VNKSF-10). Moscow.
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Kaurova, N. S., Finkel, M. I., Maslennikov, S. N., Vahtomin, Y. B., Antipov, S. V., Smirnov, K. V., et al. (2004). Submillimeter mixer based on YBa2Cu3O7-x thin film. In Proc. 1-st conf. Fundamental problems of high temperature superconductivity (291). Moscow-Zvenigorod.
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Antipov, S., Trifonov, A., Krause, S., Meledin, D., Desmaris, V., Belitsky, V., et al. (2017). Gain bandwidth of NbN HEB mixers on GaN buffer layer operating at 2 THz local oscillator frequency. In Proc. 28th Int. Symp. Space Terahertz Technol. (pp. 147–148).
Abstract: In this paper, we present IF bandwidth measurement results of NbN HEB mixers, which are employing NbN thin films grown on a GaN buffer-layer. The HEB mixers were operated in the heterodyne regime at a bath temperature of approximately 4.5 K and with a local oscillator operating at a frequency of 2 THz. A quantum cascade laser served as the local oscillator and a reference synthesizer based on a BWO generator (130-160 GHz) and a semiconductor superlattice (SSL) frequency multiplier was used as a signal source. By changing the LO frequency it was possible to record the IF response or gain bandwidth of the HEB with a spectrum analyzer at the operation point, which yielded lowest noise temperature. The gain bandwidth that was recorded in the heterodyne regime at 2 THz amounts to approximately 5 GHz and coincides well with a measurement that has been performed at elevated bath temperatures and lower LO frequency of 140 GHz. These findings strongly support that by using a GaN buffer-layer the phonon escape time of NbN HEBs can be significantly lower as compared to e.g. Si substrate, thus, providing higher gain bandwidth.
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