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Author |
Trifonov, A.; Tong, C.-Y. E.; Blundell, R.; Ryabchun, S.; Gol'tsman, G. |
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Title |
Probing the stability of HEB mixers with microwave injection |
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Journal Article |
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Year |
2015 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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Volume |
25 |
Issue |
3 |
Pages |
2300404 (1 to 4) |
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Keywords |
NbN HEB mixer, stability, Allan-variance |
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Abstract |
Using a microwave probe as a tool, we have performed experiments aimed at understanding the origin of the output-power fluctuations in hot-electron-bolometer (HEB) mixers. We use a probe frequency of 1.5 GHz. The microwave probe picks up impedance changes of the HEB, which are examined upon demodulation of the reflected wave outside the cryostat. This study shows that the HEB mixer operates in two different regimes under a terahertz pump. At a low pumping level, strong pulse modulation is observed, as the device switches between the superconducting state and the normal state at a rate of a few megahertz. When pumped much harder, to approximate the low-noise mixer operating point, residual modulation can still be observed, showing that the HEB mixer is intrinsically unstable even in the resistive state. Based on these observations, we introduced a low-frequency termination to the HEB mixer. By terminating the device in a 50-Ω resistor in the megahertz frequency range, we have been able to improve the output-power Allan time of our HEB receiver by a factor of four to about 10 s for a detection bandwidth of 15 MHz, with a corresponding gain fluctuation of about 0.035%. |
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1051-8223 |
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1355 |
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Hajenius, M.; Barends, R.; Gao, J. R.; Klapwijk, T. M.; Baselmans, J. J. A.; Baryshev, A.; Voronov, B.; Gol'tsman, G. |
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Title |
Local resistivity and the current-voltage characteristics of hot electron bolometer mixers |
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Journal Article |
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Year |
2005 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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15 |
Issue |
2 |
Pages |
495-498 |
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Keywords |
HEB mixer distributed model, HEB distributed model, distributed HEB model |
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Abstract |
Hot-electron bolometer devices, used successfully in low noise heterodyne mixing at frequencies up to 2.5 THz, have been analyzed. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, is used to model pumped IV curves and understand the physical conditions during the mixing process. We argue that the mixing is predominantly due to the strongly temperature dependent local resistivity of the NbN. Experimentally we identify the origins of different transition temperatures in a real HEB device, suggesting the importance of the intrinsic resistive transition of the superconducting bridge in the modeling. |
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1051-8223 |
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980 |
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Bell, M.; Kaurova, N.; Divochiy, A.; Gol'tsman, G.; Bird, J.; Sergeev, A.; Verevkin, A. |
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On the nature of resistive transition in disordered superconducting nanowires |
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Journal Article |
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2007 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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17 |
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2 |
Pages |
267-270 |
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SSPD, SNSPD |
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Hot-electron single-photon counters based on long superconducting nanowires are starting to become popular in optical and infrared technologies due to their ultimately high sensitivity and very high response speed. We investigate intrinsic fluctuations in long NbN nanowires in the temperature range of 4.2 K-20 K, i.e. above and below the superconducting transition. These fluctuations are responsible for fluctuation resistivity and also determine the noise in practical devices. Measurements of the fluctuation resistivity were performed at low current densities and also in external magnetic fields up to 5 T. Above the BCS critical temperature T co the resistivity is well described by the Aslamazov-Larkin (AL) theory for two-dimensional samples. Below T co the measured resistivity is in excellent agreement with the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory developed for one-dimensional superconductors. Despite that our nanowires of 100 nm width are two-dimensional with respect to the coherence length, our analysis shows that at relatively low current densities the one-dimensional LAMH mechanism based on thermally induced phase slip centers dominates over the two-dimensional mechanism related to unbinding of vortex-antivortex pairs below the Berezinskii-Kosterlitz-Thouless transition. |
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1051-8223 |
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1247 |
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Kitaygorsky, J.; Komissarov, I.; Jukna, A.; Pan, D.; Minaeva, O.; Kaurova, N.; Divochiy, A.; Korneev, A.; Tarkhov, M.; Voronov, B.; Milostnaya, I.; Gol'tsman, G.; Sobolewski, R.R. |
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Title |
Dark counts in nanostructured nbn superconducting single-photon detectors and bridges |
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Journal Article |
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Year |
2007 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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Volume |
17 |
Issue |
2 |
Pages |
275-278 |
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SSPD; SNSPD |
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We present our studies on dark counts, observed as transient voltage pulses, in current-biased NbN superconducting single-photon detectors (SSPDs), as well as in ultrathin (~4 nm), submicrometer-width (100 to 500 nm) NbN nanobridges. The duration of these spontaneous voltage pulses varied from 250 ps to 5 ns, depending on the device geometry, with the longest pulses observed in the large kinetic-inductance SSPD structures. Dark counts were measured while the devices were completely isolated (shielded by a metallic enclosure) from the outside world, in a temperature range between 1.5 and 6 K. Evidence shows that in our two-dimensional structures the dark counts are due to the depairing of vortex-antivortex pairs caused by the applied bias current. Our results shed some light on the vortex dynamics in 2D superconductors and, from the applied point of view, on intrinsic performance of nanostructured SSPDs. |
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1051-8223 |
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1248 |
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Author |
Skalare, A.; McGrath, William R.; Echternach, P. M.; Leduc, H. G.; Siddiqi, I.; Verevkin, A.; Prober, D. E. |
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Title |
Aluminum hot-electron bolometer mixers at submillimeter wavelengths |
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Journal Article |
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Year |
2001 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
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Volume |
11 |
Issue |
1 |
Pages |
641-644 |
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Keywords |
Al HEB mixer, contacts, interface, in situ, in-situ, Aluminium HEB mixer |
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Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 Ω down to about 9 Ω per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 μm long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies. |
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1051-8223 |
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ref919426b |
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1061 |
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