| Records |
| Author |
Lobanov, Y. V.; Vakhtomin, Y. B.; Pentin, I. V.; Rosental, V. A.; Smirnov, K. V.; Goltsman, G. N.; Volkov, O. Y.; Dyuzhikov, I. N.; Galiev, R. R.; Ponomarev, D. S.; Khabibullin, R. A. |
| Title |
Time-resolved measurements of light–current characteristic and mode competition in pulsed THz quantum cascade laser |
Type |
Journal Article |
| Year |
2021 |
Publication |
Optical Engineering |
Abbreviated Journal |
Optical Engineering |
| Volume |
60 |
Issue |
8 |
Pages |
1-8 |
| Keywords |
HEB, terahertz pulse generation, terahertz pulse detection, QCL, quantum cascade laser, superconducting hot electron bolometer |
| Abstract |
Quantum cascade lasers (QCL) are widely adopted as prominent and easy-to-use solid-state sources of terahertz radiation. Yet some applications require generation and detection of very sharp and narrow terahertz-range pulses with a specific spectral composition. We have studied time-resolved light-current (L–I) characteristics of multimode THz QCL operated with a fast ramp of the injection current. Detection of THz pulses was carried out using an NbN superconducting hot-electron bolometer with the time constant of the order of 1 ns while the laser bias current was swept during a single driving pulse. A nonmonotonic behavior of the L–I characteristic with several visually separated subpeaks was found. This behavior is associated with the mode competition in THz QCL cavity, which we confirm by L–I measurements with use of an external Fabry–Perot interferometer for a discrete mode selection. We also have demonstrated the possibility to control the L–I shape with suppression of one of the subpeaks by simply adjusting the off-axis parabolic mirror for optimal optical alignment for one of the laser modes. The developed technique paves the way for rapid characterization of pulsed THz QCLs for further studies of the possibilities of using this approach in remote sensing. |
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10.1117/1.Oe.60.8.082019 |
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1260 |
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| Author |
Korneev, A. A. |
| Title |
Superconducting NbN microstrip single-photon detectors |
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Abstract |
| Year |
2021 |
Publication |
Proc. Quantum Optics and Photon Counting |
Abbreviated Journal |
Proc. Quantum Optics and Photon Counting |
| Volume |
11771 |
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| Keywords |
NbN SSPD, SNSPD |
| Abstract |
Superconducting Single-Photon Detectors (SSPD) invented two decades ago have evolved to a mature technology and have become devices of choice in the advanced applications of quantum optics, such as quantum cryptography and optical quantum computing. In these applications SSPDs are coupled to single-mode fibers and feature almost unity detection efficiency, negligible dark counts, picosecond timing jitter and MHz photon count rate. Meanwhile, there are great many applications requiring coupling to multi-mode fibers or free space. ‘Classical’ SSPDs with 100-nm-wide superconducting strip and covering area of about 100 µm2 are not suitable for further scaling due to degradation of performance and low fabrication yield. Recently we have demonstrated single-photon counting in micron-wide superconducting bridges and strips. Here we present our approach to the realization of practical photon-counting detectors of large enough area to be efficiently coupled to multi-mode fibers or free space. The detector is either a meander or a spiral of 1-µm-wide strip covering an area of 50x50 µm2. Being operated at 1.7K temperature it demonstrates the saturated detection efficiency (i.e. limited by the absorption in the detector) up to 1550 nm wavelength, about 10 ns dead time and timing jitter in range 50-100 ps. |
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Prochazka, I.; Štefaňák, M.; Sobolewski, R.; Gábris, A. |
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Quantum Optics and Photon Counting; SPIE Optics + Optoelectronics, 2021, Online Only |
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1784 |
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Moshkova, M. A.; Morozov, P. V.; Antipov, A. V.; Vakhtomin, Y. B.; Smirnov, K. V. |
| Title |
High-efficiency multi-element superconducting single-photon detector |
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Conference Article |
| Year |
2021 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
11771 |
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Pages |
2-8 |
| Keywords |
PNR SSPD, large active area, detection efficiency |
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We present the result of the creation and investigation of the multi-element superconducting single photon detectors, which can recognize the number of photons (up to six) in a short pulse of the radiation at telecommunication wavelengths range. The best receivers coupled with single-mode fiber have the system quantum efficiency of ⁓85%. The receivers have a 100 ps time resolution and a few nanoseconds dead time that allows them to operate at megahertz counting rate. Implementation of the multi-element architecture for creation of the superconducting single photon detectors with increased sensitive area allows to create the high efficiency receivers coupled with multi-mode fibers and with preserving of the all advantages of superconducting photon counters. |
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SPIE |
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Prochazka, I.; Štefaňák, M.; Sobolewski, R.; Gábris, A. |
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Quantum Optics and Photon Counting |
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1795 |
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Korneeva, Y. P.; Manova, N. N.; Dryazgov, M. A.; Simonov, N. O.; Zolotov, P. I.; Korneev, A. A. |
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Influence of sheet resistance and strip width on the detection efficiency saturation in micron-wide superconducting strips and large-area meanders |
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Journal Article |
| Year |
2021 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
| Volume |
34 |
Issue |
8 |
Pages |
084001 |
| Keywords |
NbN SSPD, SMSPD |
| Abstract |
We report our study of detection efficiency (DE) saturation in wavelength range 400 – 1550 nm for the NbN Superconducting Microstrip Single-Photon Detectors (SMSPD) featuring the strip width up to 3 μm. We observe an expected decrease of the $DE$ saturation plateau with the increase of photon wavelength and decrease of film sheet resistance. At 1.7 K temperature DE saturation can be clearly observed at 1550 nm wavelength in strip with the width up to 2 μm when sheet resistance of the film is above 630Ω/sq. In such strips the length of the saturation plateau almost does not depend on the strip width. We used these films to make meander-shaped detectors with the light sensitive area from 20×20μm2 to a circle 50 μm in diameter. In the latter case, the detector with the strip width of 0.49 μm demonstrates saturation of DE up to 1064 nm wavelength. Although DE at 1310 and 1550 nm is not saturated, it is as high as 60%. The response time is limited by the kinetic inductance and equals to 20 ns(by 1/e decay), timing jitter is 44 ps. When coupled to multi-mode fibre large-area meanders demonstrate significantly higher dark count rate which we attribute to thermal background photons, thus advanced filtering technique would be required for practical applications. |
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0953-2048 |
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1793 |
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Samsonova, Alena; Zolotov, Philipp; Baeva, Elmira; Lomakin, Andrey; Titova, Nadezhda; Kardakova, Anna; Goltsman, Gregory |
| Title |
Signatures of surface magnetic disorder in thin niobium films |
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Journal Article |
| Year |
2021 |
Publication |
IEEE Trans. Appl. Supercond. |
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1-1 |
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Temperature measurement, Temperature dependence, Superconducting magnets, Superconducting transition temperature, Substrates, Resistance, Scattering |
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We present our studies on the evolution of the normal and superconducting properties with thickness of thin Nb films with a low level of non-magnetic disorder (kFl 150 for the thickest film in the set). The analysis of the superconducting behavior points to the presence of magnetic moments, hidden in the native oxide on the surface of Nb films. Using the Abrikosov-Gorkov theory, we obtain the density of surface magnetic moments of 1013 cm-2, which is in agreement with the previously reported data for Nb films. |
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1051-8223 |
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1162 |
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