Records |
Author |
Jiang, L.; Antipov, S. V.; Voronov, B. M.; Gol'tsman, G. N.; Zhang, W.; Li, N.; Lin, Z. H.; Yao, Q. J.; Miao, W.; Shi, S. C.; Svechnikov, S. I.; Vakhtomin, Y. B. |
Title |
Characterization of the performance of a quasi-optical NbN superconducting HEB mixer |
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Journal Article |
Year |
2007 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
17 |
Issue |
2 |
Pages |
395-398 |
Keywords |
NbN HEB mixers, noise temperature |
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. |
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1051-8223 |
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1429 |
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Author |
Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Blundell, Raymond; Gol'tsman, Gregory |
Title |
Stabilization scheme for hot-electron bolometer receivers using microwave radiation |
Type |
Journal Article |
Year |
2009 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
19 |
Issue |
1 |
Pages |
14-19 |
Keywords |
HEB, mixer, Allan variance, stabilization, radiometer equation |
Abstract |
We present the results of a stabilization scheme for terahertz receivers based on NbN hot-electron bolometer (HEB) mixers that uses microwave radiation with a frequency much lower than the gap frequency of NbN to compensate for mixer current fluctuations. A feedback control loop, which actively controls the power level of the injected microwave radiation, has successfully been implemented to stabilize the operating point of the HEB mixer. This allows us to increase the receiver Allan time to 10 s and also improve the temperature resolution of the receiver by about 30% in the total power mode of operation. |
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1051-8223 |
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RPLAB @ lobanovyury @ |
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559 |
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Author |
Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Paine, Scott; Lobanov, Yury; Blundell, Raymond; Goltsman, Gregory |
Title |
Temperature resolution of an HEB receiver at 810 GHz |
Type |
Journal Article |
Year |
2009 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
19 |
Issue |
3 |
Pages |
293-296 |
Keywords |
HEB mixer |
Abstract |
We present the results of direct measurements of the temperature resolution of an HEB receiver operating at 810 GHz, in both continuum and spectroscopic modes. In the continuum mode, the input of the receiver was switched between black bodies with different physical temperatures. With a system noise temperature of around 1100 K, the receiver was able to resolve loads which differed in temperature by about 1 K over an integration time of 5 seconds. This resolution is significantly worse than the value of 0.07 K given by the radiometer equation. In the spectroscopic mode, a gas cell filled with carbonyl sulphide (OCS) gas was used and the emission line at 813.3537060 GHz was measured using the receiver in conjunction with a digital spectrometer. From the observed spectra, we determined that the measurement uncertainty of the equivalent emission temperature was 2.8 K for an integration time of 0.25 seconds and a spectral resolution of 12 MHz, compared to a 1.4 K temperature resolution given by the radiometer equation. This relative improvement is due to the fact that at short integration times the contribution from 1/f noise and drift are less dominant. In both modes, the temperature resolution was improved by about 40% with the use of a feedback loop which adjusted the level of an injected microwave radiation to maintain a constant operating current of the HEB mixer. This stabilization scheme has proved to be very effective to keep the temperature resolution of the HEB receiver to close to the theoretical value given by the radiometer equation. |
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636 |
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Xiaolong Hu; Holzwarth, C.W.; Masciarelli, D.; Dauler, E.A.; Berggren, K.K. |
Title |
Efficiently coupling light to superconducting nanowire single-photon detectors |
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Journal Article |
Year |
2009 |
Publication |
IEEE Trans. Appl. Supercond. |
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Volume |
19 |
Issue |
3 |
Pages |
336-340 |
Keywords |
optical antennas; SNSPD |
Abstract |
We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for the fiber coupling, the absorptance of the NbN nanowire for TE-like-polarized photons can reach 76% including coupling efficiency at the wavelength of 1550 nm by adding a silicon nitride waveguide and an inverse-taper coupler. |
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RPLAB @ gujma @ |
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647 |
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Yang, J.K.W.; Kerman, A.J.; Dauler, E.A.; Cord, B.; Anant, V.; Molnar, R.J.; Berggren, K.K. |
Title |
Suppressed critical current in superconducting nanowire single-photon detectors with high fill-factors |
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Journal Article |
Year |
2009 |
Publication |
IEEE Trans. Appl. Supercond. |
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Volume |
19 |
Issue |
3 |
Pages |
318-322 |
Keywords |
SNSPD |
Abstract |
In this work we present a new fabrication process that enabled the fabrication of superconducting nanowire single photon detectors SNSPD with fill-factors as high as 88% with gaps between nanowires as small as 12 nm. This fabrication process combined high-resolution electron-beam lithography with photolithography. Although this work was motivated by the potential of increased detection efficiency with higher fill-factor devices, test results showed an unexpected systematic suppression in device critical currents with increasing fill-factor. |
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RPLAB @ gujma @ |
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677 |
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