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Svechnikov, S. I., Okunev, O. V., Yagoubov, P. A., Gol'tsman, G. N., Voronov, B. M., Cherednichenko, S. I., et al. (1997). 2.5 THz NbN hot electron mixer with integrated tapered slot antenna. IEEE Trans. Appl. Supercond., 7(2), 3548–3551.
Abstract: A Hot Electron Bolometer (HEB) mixer for 2.5 THz utilizing a NbN thin film device, integrated with a Broken Linearly Tapered Slot Antenna (BLTSA), has been fabricated and is presently being tested. The NbN HEB device and the antenna were fabricated on a SiO2membrane. A 0.5 micrometer thick SiO2layer was grown by rf magnetron reactive sputtering on a GaAs wafer. The HEB device (phonon-cooled type) was produced as several parallel strips, 1 micrometer wide, from an ultrathin NbN film 4-7 nm thick, that was deposited onto the SiO2layer by dc magnetron reactive sputtering. The BLTSA was photoetched in a multilayer Ti-Au metallization. In order to strengthen the membrane, the front-side of the wafer was coated with a 5 micrometer thick polyimide layer just before the membrane formation. The last operation was anisotropic etching of the GaAs in a mixture of HNO3and H2O2.
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Yagoubov, P., Hoogeveen, R., Torgashin, M., Khudchenko, A., Koshelets, V., Suttiwong, N., et al. (2006). 550-650 GHz spectrometer development for TELIS. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 338–341).
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Ekstörm, H., Kollberg, E., Yagoubov, P., Gol'tsman, G., Gershenzon, E., & Yngvesson, S. (1997). Gain and noise bandwidth of NbN hot-electron bolometric mixers. Appl. Phys. Lett., 70(24), 3296–3298.
Abstract: We have measured the noise performance and gain bandwidth of 35 Å thin NbN hot-electron mixers integrated with spiral antennas on silicon substrate lenses at 620 GHz. The best double-sideband receiver noise temperature is less than 1300 K with a 3 dB bandwidth of ≈5 GHz. The gain bandwidth is 3.2 GHz. The mixer output noise dominated by thermal fluctuations is 50 K, and the intrinsic conversion gain is about −12 dB. Without mismatch losses and excluding the loss from the beamsplitter, we expect to achieve a receiver noise temperature of less than 700 K.
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Semenov, A. D., Gousev, Y. P., Nebosis, R. S., Renk, K. F., Yagoubov, P., Voronov, B. M., et al. (1996). Heterodyne detection of THz radiation with a superconducting hot‐electron bolometer mixer. Appl. Phys. Lett., 69(2), 260–262.
Abstract: We report on the use of a superconducting hot‐electron bolometer mixer for heterodyne detection of terahertz radiation. Radiation with a wavelength of 119 μm was coupled to the mixer, a NbN microbridge, by a hybrid quasioptical antenna consisting of an extended hyperhemispherical lens and a planar logarithmic spiral antenna. We found, at an intermediate frequency of 1.5 GHz, a system double side band noise temperature of ≊40 000 K and conversion losses of 25 dB. We also discuss the possibilities of further improvement of the mixer performance.
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Yagoubov, P., Kroug, M., Merkel, H., Kollberg, E., Schubert, J., Hubers, H. - W., et al. (1999). Heterodyne measurements of a NbN superconducting hot electron mixer at terahertz frequencies. IEEE Trans. Appl. Supercond., 9(2), 3757–3760.
Abstract: The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.
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