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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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Ryabchun, S. A.; Tretyakov, I. V.; Finkel, M. I.; Maslennikov, S. N.; Kaurova, N. S.; Seleznev, V. A.; Voronov, B. M.; Gol'tsman, G. N. |
| Title |
NbN phonon-cooled hot-electron bolometer mixer with additional diffusion cooling |
Type |
Conference Article |
| Year |
2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 20th ISSTT |
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Issue |
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Pages |
151-154 |
| Keywords |
HEB, mixer, bandwidth, noise temperatue, in-situ contacts, in situ contacts |
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Charlottesville, USA |
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590 |
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Рябчун, С. А. |
| Title |
Широкополосные высокостабильные терагерцовые смесители на горячих электронах из тонких сверхпроводниковых пленок NbN |
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Manuscript |
| Year |
2009 |
Publication |
М. МПГУ |
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Issue |
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Pages |
98 |
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HEB, mixer, terahertz, THz, stability, Allan variance, conversion bandwidth, in-situ technique, Au contacts |
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Ph.D. thesis |
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598 |
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Ryabchun, S. A.; Tretyakov, I. V.; Pentin, I. V.; Kaurova, N. S.; Seleznev, V. A.; Voronov, B. M.; Finkel, M. I.; Maslennikov, S. N.; Gol'tsman, G. N. |
| Title |
Low-noise wide-band hot-electron bolometer mixer based on an NbN film |
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Journal Article |
| Year |
2009 |
Publication |
Radiophys. Quant. Electron. |
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| Volume |
52 |
Issue |
8 |
Pages |
576-582 |
| Keywords |
HEB mixer, in-situ contacts, noise temperature, conversion gain bandwidth, diffusion cooling channel |
| Abstract |
We develop and study a hot-electron bolometer mixer made of a two-layer NbN–Au film in situ deposited on a silicon substrate. The double-sideband noise temperature of the mixer is 750 K at a frequency of 2.5 THz. The conversion efficiency measurements show that at the superconducting transition temperature, the intermediate-frequency bandwidth amounts to about 6.5 GHz for a mixer 0.112 μm long. These record-breaking characteristics are attributed to the improved contacts between a sensitive element and a helical antenna and are reached due to using the in situ deposition of NbN and Au layers at certain stages of the process. |
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599 |
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Рябчун, С. А.; Третьяков, И. В.; Пентин, И. В; Каурова, Н. С.; Селезнев, В. А; Воронов, Б. М.; Финкель, М. И.; Масленников, С. Н.; Гольцман, Г. Н. |
| Title |
Малошумящий широкополосный терагерцовый смеситель на эффекте электронного разогрева в плёнке NbN |
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Journal Article |
| Year |
2009 |
Publication |
Известия высших учебных заведений. Радиофизика |
Abbreviated Journal |
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52 |
Issue |
8 |
Pages |
641-648 |
| Keywords |
HEB mixer, in-situ contacts, noise temperature, conversion gain bandwidth, diffusion cooling channel |
| Abstract |
Разработан и исследован смеситель на горячих электронах, изготовленный из двуслойной плёнки NbN-Au, осаждённой на кремневую подложку in situ. Двухполосная шумовая температура устройства составила 750 К на частоте 2.5 ТГц. Измерения эффективности преобразования для смесителя длиной 0.112 мкм вблизи температуры сверхпроводящего перехода показали полосу промежуточных частот около 6.5 ГГц. Эти результаты являются рекордными и были получены за счёт улучшения контактов между чувствительным элементом и спиральной антенной при замене технологического маршрута с нанесением слоёв NbN и Au в отдельных процессах на технологический процесс, в котором данные слои наносятся in situ без нарушения вакуума. |
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600 |
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Risacher, C.; Meledin, D.; Belitsky, V.; Bergman, P. |
| Title |
First 1.3 THz observations at the APEX telescope |
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Conference Article |
| Year |
2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
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Issue |
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Pages |
54-61 |
| Keywords |
balanced HEB mixer noise temperature APEX telescope stability Allan variance aperture efficiency |
| Abstract |
The Atacama Pathfinder EXperiment (APEX) 12m telescope is operating on the Llano Chajnantor, Chile, since 2003 and a set of state of the art sub-millimeter receivers have been installed for frequencies spanning from 150 GHz to 1500 GHz. In 2008, a balanced 1.3 THz Hot Electron Bolometer (HEB) receiver was installed for the atmospheric window 1250-1380 GHz. This instrument is part of a 4-channel receiver cryostat with the other channels being 211-275 GHz, 275-370 GHz and 380-500 GHz Sideband Separating (SSB) SIS receivers. This paper presents the first observations obtained so far with the 1.3 THz band during its first months of operation. The sky measurements were taken during opportunistic commissioning and science verification phases, when the weather conditions were sufficiently good with a Precipitable Water Vapor (PWV) below 0.25 mm, which was the case only a few nights during these months. We present the first observations of the molecular transition CO J=(11-10) line on different sources such as Orion-FIR4, CW-Leo and SgrB2(M). We describe the many challenges and difficulties encountered for achieving successful THz observations from a large sub-millimeter ground-based telescope. |
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619 |
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Rabanus, D.; Graf, U. U.; Philipp, M.; Ricken, O.; Stutzki, J.; Vowinkel, B.; Wiedner, M. C.; Walther, C.; Fischer, M.; Faist, J. |
| Title |
Phase locking of a 1.5 terahertz quantum cascade laser and use as a local oscillator in a heterodyne HEB receiver |
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Journal Article |
| Year |
2009 |
Publication |
Optics Express |
Abbreviated Journal |
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| Volume |
17 |
Issue |
3 |
Pages |
1159-1168 |
| Keywords |
QCL heterodyne, 300 uW at 1.5 THz, HEB mixer |
| Abstract |
We demonstrate for the first time the closure of an electronic phase lock loop for a continuous–wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better than 100 Hz, limited by the resolution bandwidth of the spectrum analyser. The PLL electronics make use of the intermediate frequency (IF) obtained from a hot electron bolometer (HEB) which is downconverted to a PLL IF of 125 MHz. The coarse selection of the longitudinal mode and the fine tuning is achieved via the bias voltage of the QCL. Within a QCL cavity mode, the free-running QCL shows frequency fluctuations of about 5 MHz, which the PLL circuit is able to control via the Stark–shift of the QCL gain material. Temperature dependent tuning is shown to be nonlinear, and of the order of -16 MHz/K. Additionally we have used the QCL as local oscillator (LO) to pump an HEB and perform, again for the first time at 1.5 THz, a heterodyne experiment, and obtain a receiver noise temperature of 1741 K. |
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628 |
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Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Paine, Scott; Lobanov, Yury; Blundell, Raymond; Goltsman, Gregory |
| Title |
Temperature resolution of an HEB receiver at 810 GHz |
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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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Lobanov, Y.; Tong, C.; Blundell, R.; Gol'tsman, G. |
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A study of direct detection effect on the linearity of hot electron bolometer mixers |
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Conference Article |
| Year |
2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 20th ISSTT |
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282-287 |
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HEB mixer, direct detection effect |
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We have performed a study of how direct detection affects the linearity and hence the calibration of an HEB mixer. Two types of waveguide HEB devices have been used: a 0.8 THz HEB mixer and a 1.0 THz HEB mixer which is ~5 times smaller than the former. Two independent experimental approaches were used. In the ΔG/G method, the conversion gain of the HEB mixer is first measured as a function of the bias current for a number of bias voltages. At each bias setting, we carefully measure the change in the operating current when the input loads are switched. From the measured data, we can derive the expected difference in gain between the hot and cold loads. In the second method (injection method [1]), the linearity of the HEB mixer is independently measured by injecting a modulated signal for different input load temperatures. The results of both approaches confirm that there is gain compression in the operation of HEB mixers. Based on the results of our measurements, we discuss the impact of direct detection effects on the operation of HEB mixers. |
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RPLAB @ gujma @ |
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724 |
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Pekker, David; Shah, Nayana; Sahu, Mitrabhanu; Bezryadin, Alexey; Goldbart, Paul M. |
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Stochastic dynamics of phase-slip trains and superconductive-resistive switching in current-biased nanowires |
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Journal Article |
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2009 |
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Phys. Rev. B |
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80 |
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214525 (1 to 17) |
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superconducting nanowire, phase-slip, order parameter, HEB distributed model, HEB model |
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Superconducting nanowires fabricated via carbon-nanotube templating can be used to realize and study quasi-one-dimensional superconductors. However, measurement of the linear resistance of these nanowires have been inconclusive in determining the low-temperature behavior of phase-slip fluctuations, both quantal and thermal. Thus, we are motivated to study the nonlinear current-voltage characteristics in current-biased nanowires and the stochastic dynamics of superconductive-resistive switching, as a way of probing phase-slip events. In particular, we address the question: can a single phase-slip event occurring somewhere along the wire—during which the order-parameter fluctuates to zero—induce switching, via the local heating it causes? We explore this and related issues by constructing a stochastic model for the time evolution of the temperature in a nanowire whose ends are maintained at a fixed temperature. We derive the corresponding master equation as a tool for evaluating and analyzing the mean switching time at a given value of current (smaller than the depairing critical current). The model indicates that although, in general, several phase-slip events are necessary to induce switching via a thermal runaway, there is indeed a regime of temperatures and currents in which a single event is sufficient. We carry out a detailed comparison of the results of the model with experimental measurements of the distribution of switching currents, and provide an explanation for the rather counterintuitive broadening of the distribution width that is observed upon lowering the temperature. Moreover, we identify a regime in which the experiments are probing individual phase-slip events, and thus offer a way of unearthing and exploring the physics of nanoscale quantum tunneling of the one-dimensional collective quantum field associated with the superconducting order parameter. |
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Recommended by Klapwijk |
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