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Ekström, H.; Karasik, B.; Kollberg, E.; Gol'tsman, G.; Gershenzon, E. |
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Title |
350 GHz NbN hot electron bolometer mixer |
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1995 |
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Proc. 6th Int. Symp. Space Terahertz Technol. |
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Proc. 6th Int. Symp. Space Terahertz Technol. |
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269-283 |
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NbN HEB mixers |
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Abstract |
Superconducting NbN hot-electron bolometer (HEB) mixer devices have been fabricated and measured at 350 GHz. The HEB is integrated with a double dipole antenna on an extended crystalline quartz hyper hemispherical substrate lens. Heterodyne measurement gave a -3 dB bandwidth, mainly determined by the electron- phonon interaction time, of about 680 and 1000 MHz for two different films with Tc = 8.5 and 11 K respectively. The measured DSB receiver noise temperature is around 3000 K at 800 MHz IF frequency. The main contribution to the output noise from the device is due to electron temperature fluctuations with the equivalent output noise temperature TFL-100 K. TH, has the same frequency dependence as the IF response. The contribution from Johnson noise is of the order of T. The RF coupling loss is estimated to be = 6 dB. The film with lower Tc, had an estimated intrinsic low-frequency conversion loss = 7 dB, while the other film had a conversion loss as high as 14 dB. The difference in intrinsic conversion loss is explained by less uniform absorption of radiation. Measurements of the small signal impedance shows a transition of the output impedance from the DC differential resistance Rd=dV/dI in the low frequency limit to the DC resistance R 0 =Uoff 0 in the bias point for frequencies above 3 GHz. We judge that the optimum shape of the IV-characteristic is more easily obtained at THz frequencies where the main restriction in performance should come from problems with the RF coupling. |
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1628 |
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Gerecht, E.; Musante, C. F.; Schuch, R.; Lutz, C. R.; Jr.; Yngvesson, K. S.; Mueller, E. R.; Waldivian, J.; Gol'tsman, G. N.; Voronov, B. M.; Gershenzon, E. M. |
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Title |
Hot electron detection and mixing experiments in NbN at 119 micrometer wavelength |
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Conference Article |
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1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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Proc. 6th Int. Symp. Space Terahertz Technol. |
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284-293 |
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NbN HEB mixers, detectors |
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We have performed preliminary experiments with the goal of demonstrating a Hot Electron Bolometric (HEB) mixer for a 119 micrometer wavelength (2.5 THz). We have chosen a NbN device of size 700 x 350 micrometers. This device can easily be coupled to a laser LO source, which is advantageous for performing a prototype experiment. The relatively large size of the device means that the LO power required is in the mW range; this power can be easily obtained from a THz laser source. We have measured the amount of laser power actually absorbed in the device, and from this have estimated the best optical coupling loss to be about 10 di . We are developing methods for improving the optical coupling further. Preliminary measurements of the response of the device to a chopped black-body have not yet resulted in a measured receiver noise temperature. We expect to be able to complete this measurement in the near future. |
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1629 |
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Yagubov, P.; Gol'tsman, G.; Voronov, B.; Seidman, L.; Siomash, V.; Cherednichenko, S.; Gershenzon, E. |
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The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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290-302 |
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NbN HEB mixers, fabrication process |
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We report on some unusual features observed during fabrication of ultrathin NbN films with high Tc. The films were used to fabricate HEB mixers, which were evaluated for IF bandwidth measurements at 140 GHz. Ultrathin films were fabricated using reactive dc magnetron sputtering with a discharge current source. Reproducible parameters of the films are assured keeping constant the difference between the discharge voltage in pure argon, and in a gas mixture, for the same current. A maximum bandwidth of 4 GHz at optimal LO and dc bias was obtained for mixer chip based on NbN film 35 A thick with Tc = 11 K. |
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Charlottesville, Virginia, USA |
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266 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Golts'man, G.; Gershenzon, E.; Voronov B. |
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Title |
Superconductive NbN hot-electron bolometric mixer performance at 250 GHz |
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Conference Article |
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1996 |
Publication |
Proc. 7th Int. Symp. Space Terahertz Technol. |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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331-336 |
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NbN HEB mixers |
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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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945 |
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Yagoubov, P.; Gol'tsman, G.; Voronov, B.; Svechnikov, S.; Cherednichenko, S.; Gershenzon, E.; Belitsky, V.; Ekström, H.; Semenov, A.; Gousev, Yu.; Renk, K. |
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Title |
Quasioptical phonon-cooled NbN hot-electron bolometer mixer at THz frequencies |
Type |
Conference Article |
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Year |
1996 |
Publication |
Proc. 7th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 7th Int. Symp. Space Terahertz Technol. |
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Pages |
303-317 |
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Keywords |
NbN HEB mixers |
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In our experiments we tested phonon-cooled hot-electron bolometer (HEB) quasioptical mixer based on spiral antenna designed for 0.5-1.2 THz frequency band and fabricated on sapphire, Si-coated sapphire and high resistivity silicon substrates. HEB devices were produced from thin superconducting NbN film 3.5-6 nm thick with the critical temperature of about 11-12 K. For these devices we achieved the receiver noise temperature T R (DSB) = 3000 K in the 500-700 GHz frequency range and an IF bandwidth of 3-4 GHz. Prelimanary measurements at frequencies 1-1.2 THz resulted the receiver noise temperature about 9000 K (DSB). |
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1614 |
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