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Noise Temperature and Beam Pattern of a Quasioptical Heterodyne Receiver based on NbN Hot Electron Bolometer Mixer at 5.25 THz

Authors:
W. Zhang, P. Khosropanah, J. R. Gao, T. Bansal, T. M. Klapwijk, W. Miao, S. C. Shi
Abstract:
We report the measured sensitivities of a superconducting NbN hot electron bolometer (HEB) heterodyne receiver at 5.25 THz. The terahertz (THz) radiation is quasioptically coupled to the HEB mixer with a lens and a spiral antenna. Using a measurement setup with black body calibration sources and a beam splitter in vacuum, and an antireflection coated Si lens, we obtained a double sideband (DSB) receiver noise temperature (TrecDSB) of 1150 K, which is 4.5 times hv/k (the quantum limit). In addition, the measured far field beam patterns of the integrated lens antenna from 2.5 THz to 5.3 THz show collimated beams that make it reliable to measure TrecDSB using the vacuum setup. Our experimental results in combination with an antenna-to-bolometer coupling simulation suggest that the HEB mixer can work well at least up to 6 THz, suitable for next generation of high-resolution spectroscopic space telescopes and, in particular, for the detection of the neutral atomic oxygen (OI) line at 4.7 THz.
Categories:
Mixers, Superconductors
Year:
2010
Session:
9
Full-text:
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Page Number(s):
220-225