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Meledin D, Tong CY-E, Blundell R, Kaurova N, Smirnov K, Voronov B, et al. Study of the IF bandwidth of NbN HEB mixers based on crystalline quartz substrate with an MgO buffer layer. IEEE Trans Appl Supercond. 2003;13(2):164–7.
Abstract: In this paper, we present the results of IF bandwidth measurements on 3-4 nm thick NbN hot electron bolometer waveguide mixers, which have been fabricated on a 200-nm thick MgO buffer layer deposited on a crystalline quartz substrate. The 3-dB IF bandwidth, measured at an LO frequency of 0.81 THz, is 3.7 GHz at the optimal bias point for low noise receiver operation. We have also made measurements of the IF dynamic impedance, which allow us to evaluate the intrinsic electron temperature relaxation time and self-heating parameters at different bias conditions.
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Tong C-YE, Meledin DV, Marrone DP, Paine SN, Gibson H, Blundell R. Near field vector beam measurements at 1 THz. IEEE Microw. Compon. Lett.. 2003;13(6):235–7.
Abstract: We have performed near-field vector beam measurements at 1.03 THz to characterize and align the receiver optics of a superconducting receiver. The signal source is a harmonic generator mounted on an X-Y translation stage. We model the measured two-dimensional complex beam pattern by a fundamental Gaussian mode, from which we derive the position of the beam center, the beam radius and the direction of propagation. By performing scans in the planes separated by 400 mm, we have confirmed that our beam pattern measurements are highly reliable.
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Meledin D, Tong C-YE, Blundell R, Goltsman G. Measurement of intermediate frequency bandwidth of hot electron bolometer mixers at terahertz frequency range. IEEE Microw Wireless Compon Lett. 2003;13(11):493–5.
Abstract: We have developed a new experimental setup for measuring the IF bandwidth of superconducting hot electron bolometer mixers. In our measurement system we use a chopped hot filament as a broadband signal source, and can perform a high-speed IF scan with no loss of accuracy when compared to coherent methods. Using this technique we have measured the 3 dB IF bandwidth of hot electron bolometer mixers, designed for THz frequency operation, and made from 3-4 nm thick NbN film deposited on an MgO buffer layer over crystalline quartz.
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Kawamura J, Hunter TR, Tong CYE, Blundell R, Papa DC, Patt F, et al. Ground-based terahertz CO spectroscopy towards Orion. A&A. 2002;394(1):271–4.
Abstract: Using a superconductive hot-electron bolometer heterodyne receiver on the 10-m Heinrich Hertz Telescope on Mount Graham, Arizona, we have obtained velocity-resolved 1.037 THz CO () spectra toward several positions along the Orion Molecular Cloud (OMC-1) ridge. We confirm the general results of prior observations of high-J CO lines that show that the high temperature, , high density molecular gas, , is quite extended, found along a ~ region centered on BN/KL. However, our observations have significantly improved angular resolution, and with a beam size of we are able to spatially and kinematically discriminate the emission originating in the extended quiescent ridge from the very strong and broadened emission originating in the compact molecular outflow. The ridge emission very close to the BN/KL region appears to originate from two distinct clouds along the line of sight with and ≈ . The former component dominates the emission to the south of BN/KL and the latter to the north, with a turnover point coincident with or near BN/KL. Our evidence precludes a simple rotation of the inner ridge and lends support to a model in which there are multiple molecular clouds along the line of sight towards the Orion ridge.
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Meledin D, Tong CY-E, Blundell R, Kaurova N, Smirnov K, Voronov B, et al. The sensitivity and IF bandwidth of waveguide NbN hot electron bolometer mixers on MgO buffer layers over crystalline quartz. In: Harvard university, editor. Proc. 13th Int. Symp. Space Terahertz Technol. Cambridge, MA, USA; 2002. p. 65–72.
Abstract: We have developed and characterized waveguide phonon-cooled NbN Hot Electron Bolometer (FMB) mixers fabricated from a 3-4 nm thick NbN film deposited on a 200nm thick MgO buffer layer over crystalline quartz. Double side band receiver noise temperatures of 900-1050 K at 1.035 THz, and 1300-1400 K at 1.26 THz have been measured at an intermediate frequency of 1.5 GHz. The intermediate frequency bandwidth, measured at 0.8 THz LO frequency, is 3.2 GHz at the optimal bias point for low noise receiver operation.
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