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Tong C-YE, Meledin D, Loudkov D, Blundell R, Erickson N, Kawamura J, et al. A 1.5 THz Hot-Electron Bolometer mixer operated by a planar diode based local oscillator. In: IEEE MTT-S Int. Microwave Symp. Digest. Vol 2.; 2003. p. 751–4.
Abstract: We have developed a 1.5 THz superconducting NbN Hot-Electron Bolometer mixer. It is operated by an all-solid-state Local Oscillator comprising of a cascade of 4 planar doublers following an MMIC based W-band power amplifier. The threshold available pump power is estimated to be 1 /spl mu/W.
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Tong CYE, Blundell R, Paine S, Papa DC, Kawamura J, Stern J, et al. Design and characterization of a 250-350 GHz fixed-tuned superconductor-insulator-insulator receiver. IEEE Trans. Microw. Theory Techn.. 1996;44(9):1548–56.
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Tong CE, Blundell R, Papa DC, Smith M, Kawamura J, Gol'tsman G, et al. An all solid-state superconducting heterodyne receiver at terahertz frequencies. IEEE Microw Guid Wave Lett. 1999;9(9):366–8.
Abstract: A superconducting hot-electron bolometer mixer-receiver operating from 1 to 1.26 THz has been developed. This heterodyne receiver employs two solid-state local oscillators each consisting of a Gunn oscillator followed by two stages of varactor frequency multiplication. The measured receiver noise temperature is 1350 K at 1.035 THz and 2700 K at 1.26 THz. This receiver demonstrates that tunable solid-state local oscillators, supplying only a few micro-watts of output power, can be used in terahertz receiver applications.
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Kawamura J, Tong C-YE, Blundell R, Papa DC, Hunter TR, Patt F, et al. Terahertz-frequency waveguide NbN hot-electron bolometer mixer. IEEE Trans Appl Supercond. 2001;11(1):952–4.
Abstract: We have developed a low-noise waveguide heterodyne receiver for operation near 1 THz using phonon-cooled NbN hot-electron bolometers. The mixer elements are submicron-sized microbridges of 4 nm-thick NbN film fabricated on a quartz substrate. Operating at a bath temperature of 4.2 K, the double-sideband receiver noise temperature is 760 K at 1.02 THz and 1100 K at 1.26 THz. The local oscillator is provided by solid-state sources, and power measured at the source is less than 1 /spl mu/W. The intermediate frequency bandwidth exceeds 2 GHz. The receiver was used to make the first ground-based heterodyne detection of a celestial spectroscopic line above 1 THz.
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Kawamura J, Blundell R, Tong C‐yu E, Gol’tsman G, Gershenzon E, Voronov B. Performance of NbN lattice‐cooled hot‐electron bolometric mixers. J Appl Phys. 1996;80(7):4232–4.
Abstract: The heterodyne performance of lattice‐cooled hot‐electron bolometric mixers is measured at 200 GHz. Superconducting thin‐film niobium nitride strips with ∼5 nm thickness are used as waveguide mixer elements. A double‐sideband receiver noise temperature of 750 K at 244 GHz is measured at an intermediate frequency centered at 1.5 GHz with 500 MHz bandwidth and with 4.2 K device temperature. The instantaneous bandwidth for this mixer is 1.6 GHz. The local oscillator power required by the mixer is about 0.5 μW. The mixer is linear to within 1 dB up to an input power level 6 dB below the local oscillator power. A receiver incorporating a hot‐electron bolometric mixer was used to detect molecular line emission in a laboratory gascell. This experiment unambiguously confirms that the receiver noise temperature determined from Y‐factor measurements reflects the true heterodyne sensitivity.
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Kawamura J, Blundell R, Tong C-yu E, Gol’tsman G, Gershenzon E, Voronov B, et al. Low noise NbN lattice-cooled superconducting hot-electron bolometric mixers at submillimeter wavelengths. Appl Phys Lett. 1997;70(12):1619–21.
Abstract: Lattice-cooled superconducting hot-electron bolometric mixers are used in a submillimeter-wave waveguide heterodyne receiver. The mixer elements are niobium nitride film with 3.5 nm thickness and ∼10 μm2 area. The local oscillator power for optimal performance is estimated to be 0.5 μW, and the instantaneous bandwidth is 2.2 GHz. At an intermediate frequency centered at 1.4 GHz with 200 MHz bandwidth, the double sideband receiver noise temperature is 410 K at 430 GHz. The receiver has been used to detect molecular line emission in a laboratory gas cell.
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Kawamura J, Blundell R, Tong C-YE, Papa DC, Hunter TR, Paine SN, et al. Superconductive hot-electron-bolometer mixer receiver for 800-GHz operation. IEEE Trans Microw Theory Techn. 2000;48(4):683–9.
Abstract: In this paper, we describe a superconductive hot-electron-bolometer mixer receiver designed to operate in the partially transmissive 350-μm atmospheric window. The receiver employs an NbN thin-film microbridge as the mixer element, in which the main cooling mechanism of the hot electrons is through electron-phonon interaction. At a local-oscillator frequency of 808 GHz, the measured double-sideband receiver noise temperature is TRX=970 K, across a 1-GHz intermediate-frequency bandwidth centered at 1.8 GHz. We have measured the linearity of the receiver and the amount of local-oscillator power incident on the mixer for optimal operation, which is PLO≈1 μW. This receiver was used in making observations as a facility instrument at the Heinrich Hertz Telescope, Mt. Graham, AZ, during the 1998-1999 winter observing season.
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Kawamura J, Blundell R, Tong C-YE, Golts'man G, Gershenzon E, Voronov B. Superconductive NbN hot-electron bolometric mixer performance at 250 GHz. In: Proc. 7th Int. Symp. Space Terahertz Technol.; 1996. p. 331–6.
Abstract: Thin film NbN (<40 A) strips are used as waveguide mixer elements. The electron cooling mechanism for the geometry is the electron-phonon interaction. We report a receiver noise temperature of 750 K at 244 GHz, with / IF = 1.5 GHz, Af= 500 MHz, and Tphysical = 4 K. The instantaneous bandwidth for this mixer is 1.6 GHz. The local oscillator (LO) power is 0.5 1.tW with 3 dB-uncertainty. The mixer is linear to 1 dB up to an input power level 6 dB below the LO power. We report the first detection of a molecular line emission using this class of mixer, and that the receiver noise temperature determined from Y-factor measurements reflects the true heterodyne sensitivity.
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Kawamura J, Blundell R, Tong C-YE, Gol'tsman G, Gershenzon E, Voronov B. NbN hot-electron mixer measurements at 200 GHz. In: Proc. 6th Int. Symp. Space Terahertz Technol.; 1995. p. 254–61.
Abstract: We present noise and gain measurements of resistively driven NbN hot-electron mixers near 200 GHz. The device geometry is chosen so that the dominant cooling process of the hot-electrons is their interaction with the lattice. Except for a single batch, the intermediate frequency cut-off of these mixer elements is – 3 700 MHz, and has shown little variation among other batches of devices. At 100 MHz we measured intrinsic mixer losses as low as —3 dB. We measured the noise temperatures at several intermediate frequencies, and for the best de- vice at 137 MHz with 20 MHz bandwidth, we measured 2000 K; using a low-noise first- stage amplifier at 1.5 GHz with 200 MHz bandwidth, the receiver noise temperature measured 2800 K. We estimate that the noise contribution from the mixer is 500 K and the total losses are —15 dB at 137 MHz.
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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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