|
|
Jiang, L., Zhang, W., Yao, Q. J., Lin, Z. H., Li, J., Shi, S. C., et al. (2005). Characterization of a quasi-optical NbN superconducting hot-electron bolometer mixer. In Proc. PIERS (Vol. 1, pp. 587–590).
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolome-ter) mixer measured at 500 GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled bya 4-K close-cycled refrigerator. Its receiver noise temperature and conversion gain are thoroughly investigatedfor different LO pumping levels and dc biases. The lowest receiver noise temperature is found to be approxi-mately 1200 K, and reduced to about 445 K after correcting theloss of the measurement system. The stabilityof the mixer’s IF output power is also demonstrated.
|
|
|
|
Jiang, L., Li, J., Zhang, W., Yao, Q. J., Lin, Z. L., Shi, S. C., et al. (2005). Characterization of NbN HEB mixers cooled by a close-cycled 4 Kelvin refrigerator. IEEE Trans. Appl. Supercond., 15(2), 511–513.
Abstract: It is quite beneficial to operate superconducting hot-electron-bolometer (HEB) mixers with a close-cycled 4 Kelvin refrigerator for real applications such as astronomy and atmospheric research. In this paper, a phononcooled NbN HEB mixer (quasioptical type) is thoroughly characterized under such a cooling circumstance. The effects of mechanical vibration, electrical interference, and temperature fluctuation of a two-stage Gifford-McMahon 4 Kelvin refrigerator upon the characteristics of the phononcooled NbN HEB mixer are investigated in particular. Detailed measurement results are presented.
|
|
|
|
Jiang, L., Antipov, S. V., Voronov, B. M., Gol'tsman, G. N., Zhang, W., Li, N., et al. (2007). Characterization of the performance of a quasi-optical NbN superconducting HEB mixer. IEEE Trans. Appl. Supercond., 17(2), 395–398.
Abstract: In this paper we focus mainly on the investigation of the performance of a quasi-optical (planar log-spiral antenna) phonon-cooled NbN superconducting hot electron bolometer (HEB) mixer, which is cryogenically cooled by a close-cycled 4-K cryocooler, at 500 and 850 GHz frequency bands. The mixer's noise performance, stability of IF output power, and local oscillator (LO) power requirement are characterized for three NbN superconducting HEB devices of different sizes. The transmission characteristics of Mylar and Zitex films with incidence waves of an elliptical polarization are also examined by measuring the mixer's noise temperature. The lowest receiver noise temperatures (with no corrections) of 750 and 1100 K are measured at 500 and 850 GHz, respectively. Experimental results also demonstrate that the bigger the HEB device is, the higher the stability of IF output power becomes.
|
|
|
|
Il'in, K. S., Cherednichenko, S. I., Gol'tsman, G. N., Currie, M., & Sobolewski, R. (1998). Comparative study of the bandwidth of phonon-cooled NbN hot-electron bolometers in submillimeter and optical wavelength ranges. In Proc. 9th Int. Symp. Space Terahertz Technol. (pp. 323–330).
Abstract: We report the results of the bandwidth measurements of NbN hot-electron bolometers, perfomied in the terahertz frequency domain at 140 GHz and 660 GHz and in time domain in the optical range at the wavelength of 395 nm.. Our studies were done on 3.5-nm-thick NbN films evaporated on sapphire substrates and patterned into ilin-size microbridges. In order to measure the gain bandwidth, we used two identical BWOs (140 or 660 GHz), one functioning as a local oscillator and the other as a signal source. The bandwidth we achieved was 3.5-4 GHz at 4.2 K with the optimal LO and DC biases. Time-domain measurements with a resolution below 300 fs were performed using an electro-optic sampling system, in the temperature range between 4.2 K to 9 K at various values of the bias current and optical power. The obtained response time of the NbN hot-electron bolometer to —100- fs-wide Ti:sapphire laser pulses was about 27 ps, what corresponds to the 5.9 GHz gain bandwidth.
|
|
|
|
Huebers, H. - W., Semenov, A., Schubert, J., Gol’tsman, G. N., Voronov, B. M., Gershenzon, E. M., et al. (2000). NbN hot-electron bolometer as THz mixer for SOFIA. In R. K. Melugin, & H. - P. Roeser (Eds.), Proc. SPIE (Vol. 4014, pp. 195–202). SPIE.
Abstract: Heterodyne receivers for applications in astronomy need quantum limited sensitivity. We have investigated phonon- cooled NbN hot electron bolometric mixers in the frequency range from 0.7 THz to 5.2 THz. The devices were 3.5 nm thin films with an in-plane dimension of 1.7 X 0.2 micrometers 2 integrated in a complementary logarithmic spiral antenna. The best measured DSB receiver noise temperatures are 1300 K (0.7 THz), 2000 K (1.4 THz), 2100 K (1.6 THz), 2600 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz), and 8800 K (5.2 THz). The sensitivity fluctuation, the long term stability, and the antenna pattern were measured. The results demonstrate that this mixer is very well suited for GREAT, the German heterodyne receiver for SOFIA.
|
|
