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Author |
Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A; Vacelet, T |
Title |
Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges |
Type |
Journal Article |
Year |
2014 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
<ef><bf><bc>Appl. Phys. Lett. |
Volume |
104 |
Issue |
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Pages |
052605(1-4) |
Keywords |
NbN HEB mixers, local oscillator power, RF nonuniform absorption |
Abstract |
We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film. |
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935 |
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Author |
Maslennikov, S. |
Title |
RF heating efficiency of the terahertz superconducting hot-electron bolometer |
Type |
Journal Article |
Year |
2014 |
Publication |
arXiv |
Abbreviated Journal |
arXiv |
Volume |
1404.5276 |
Issue |
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Pages |
1-4 |
Keywords |
superconducting hot-electron bolometer mixer, HEB, NbN, distributed model, HEB model, HEB mixer model, heat balance equa-tions, conversion gain, RF heating efficiency, noise temperature, simulation, Euler method |
Abstract |
We report results of the numerical solution by the Euler method of the system of heat balance equations written in recurrent form for the superconducting hot-electron bolometer (HEB) embedded in an electrical circuit. By taking into account the dependence of the HEB resistance on the transport current we have been able to calculate rigorously the RF heating efficiency, absorbed local oscillator (LO) power and conversion gain of the HEB mixer. We show that the calculated conversion gai nis in excellent agreement with the experimental results, and that the substitution of the calculated RF heating efficiency and absorbed LO power into the expressions for the conversion gain and noise temperature given by the analytical small-signal model of the HEB yields excellent agreement with the corresponding measured values |
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RPLAB @ atomics90 @ |
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954 |
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Author |
Zhang, W.; Miao, W.; Zhong, J. Q.; Shi, S. C.; Hayton, D. J.; Vercruyssen, N.; Gao, J. R.; Goltsman, G. N. |
Title |
Temperature dependence of the receiver noise temperature and IF bandwidth of superconducting hot electron bolometer mixers |
Type |
Journal Article |
Year |
2014 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
Volume |
27 |
Issue |
8 |
Pages |
085013 (1 to 5) |
Keywords |
NbN HEB mixers |
Abstract |
In this paper we study the temperature dependence of the receiver noise temperature and IF noise bandwidth of superconducting hot electron bolometer (HEB) mixers. Three superconducting NbN HEB devices of different transition temperatures (Tc) are measured at 0.85 THz and 1.4 THz at different bath temperatures (Tbath) between 4 K and 9 K. Measurement results demonstrate that the receiver noise temperature of superconducting NbN HEB devices is nearly constant for Tbath/Tc, less than 0.8, which is consistent with the simulation based on a distributed hot-spot model. In addition, the IF noise bandwidth appears independent of Tbath/Tc, indicating the dominance of phonon cooling in the investigated HEB devices. |
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0953-2048 |
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1358 |
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Gurovich, B. A.; Tarkhov, M. A.; Prikhod'ko, K. E.; Kuleshova, E. A.; Komarov, D. A.; Stolyarov, V. L.; Olshanskii, E. D.; Goncharov, B. V.; Goncharova, D. A.; Kutuzov, L. V.; Domantovskii, A. G. |
Title |
Controlled modification of superconducting properties of NbN ultrathin films under composite ion beam irradiation |
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Journal Article |
Year |
2014 |
Publication |
Nanotechnologies in Russia |
Abbreviated Journal |
Nanotechnologies in Russia |
Volume |
9 |
Issue |
7 |
Pages |
386-390 |
Keywords |
superconducting NbN films composite ion beam irradiation protoning |
Abstract |
In this work, the results of studying the microstructure and superconducting properties of ultrathin films on the basis of NbN in the initial state and after modification by being subjecting to composite ion beam irradiation with the energy ~1–3) keV are presented. HRTEM analysis showed that the initial films on the sapphire substrate in orientation “c-cut†are characterized by a grain size essentially exceeding the film thickness, while on the other substrates the size of grains corresponds to the thickness of film. Using XPS analysis, it was shown that in the initial films the atomic ratio of Nb and N is 0.51/0.49, respectively, the percentage of oxygen being lower than 5%. For ultrathin films 5 nm in thickness, the critical temperature of transit to superconducting state (T c) is found to be ~3.6 K and the density of critical current is jc ~8MA/cm2. In the work it is experimentally determined that the irradiation of NbN films by composite ion beams leads to the controlled modification of its superconducting properties due to the process of selective substitution of nitrogen atoms on the oxygen atoms. |
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1000 |
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Lusche, R.; Semenov, A.; Ilin, K.; Siegel, M.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Goltsman, G.; Vodolazov, D.; Hübers, H.-W. |
Title |
Effect of the wire width on the intrinsic detection efficiency of superconducting-nanowire single-photon detectors |
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Journal Article |
Year |
2014 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
Volume |
116 |
Issue |
4 |
Pages |
043906 (1 to 9) |
Keywords |
NbN SSPD, SNSPD, TaN |
Abstract |
A thorough spectral study of the intrinsic single-photon detection efficiency in superconducting TaN and NbN nanowires with different widths has been performed. The experiment shows that the cut-off of the intrinsic detection efficiency at near-infrared wavelengths is most likely controlled by the local suppression of the barrier for vortex nucleation around the absorption site. Beyond the cut-off quasi-particle diffusion in combination with spontaneous, thermally activated vortex crossing explains the detection process. For both materials, the reciprocal cut-off wavelength scales linearly with the wire width where the scaling factor agrees with the hot-spot detection model. |
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0021-8979 |
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1357 |
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