Ovchinnikov, O. V., Perepelitsa, A. S., Smirnov, M. S., Latyshev, A. N., Grevtseva, I. G., Vasiliev, R. B., et al. (2020). Luminescence of colloidal Ag2S/ZnS core/shell quantum dots capped with thioglycolic acid. J. Luminescence, 220, 117008 (1 to 7).
Abstract: The features of IR luminescence of colloidal AgS QDs passivated with thioglycolic acid (AgS/TGA) under the formation of AgS/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of AgS/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the AgS/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the AgS core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the AgS core QDs act as luminescence quenching centers and do not reveal structural transformations into AgS, provided that the clusters are not in contact with TGA.
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Shcherbatenko, M. L., Elezov, M. S., Goltsman, G. N., & Sych, D. V. (2020). Sub-shot-noise-limited fiber-optic quantum receiver. Phys. Rev. A, 101(3), 032306 (1 to 5).
Abstract: We experimentally demonstrate a quantum receiver based on the Kennedy scheme for discrimination between two phase-modulated weak coherent states. The receiver is assembled entirely from standard fiber-optic elements and operates at a conventional telecom wavelength of 1.55 μm. The local oscillator and the signal are transmitted through different optical fibers, and the displaced signal is measured with a high-efficiency superconducting nanowire single-photon detector. We show the discrimination error rate is two times below that of a shot-noise-limited receiver with the same system detection efficiency.
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Saveskul, N. A., Titova, N. A., Baeva, E. M., Semenov, A. V., Lubenchenko, A. V., Saha, S., et al. (2019). Superconductivity behavior in epitaxial TiN films points to surface magnetic disorder. Phys. Rev. Applied, 12(5), 054001.
Abstract: We analyze the evolution of the normal and superconducting properties of epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of the residual resistivity, that becomes dominated by diffusive surface scattering for d≤20nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such high-quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of approximately 1012cm−2. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films.
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Bakhvalova, T., Belkin, M. E., Kovalyuk, V. V., Prokhodtcov, A. I., Goltsman, G. N., & Sigov, A. S. (2019). Studying key principles for design and fabrication of silicon photonic-based beamforming networks. In PIERS-Spring (pp. 745–751).
Abstract: In the paper, we address key principles for computer-aided design and fabrication of silicon-photonics-based optical beamforming network selecting the optimal approach by simulation and experimental results. To clarify the consideration, the study is conducted on the example of a widely used binary switchable silicon-nitride optical beamforming network based on TriPleX platform. Comparison of simulation results and experimental studies of the prototype shows that the relative error due to technological imperfections does not exceed 3%. According to the estimation, such an error introduces insignificant distortion in the radiation pattern of the referred antenna array.
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Titova, N., Gayduchenko, I. A., Moskotin, M. V., Fedorov, G. F., & Goltsman, G. N. (2019). Carbon nanotube based terahertz radiation detectors. In J. Phys.: Conf. Ser. (Vol. 1410, 012208 (1 to 5)).
Abstract: In this paper, we study terahertz detectors based on single quasimetallic carbon nanotubes (CNT) with asymmetric contacts and different metal pairs. We demonstrate that, depending on the contact metallization of the device, various detection mechanisms are manifested.
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