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Korneev, A.; Korneeva, Y.; Florya, I.; Voronov, B.; Goltsman, G. |
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Title |
NbN nanowire superconducting single-photon detector for mid-infrared |
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Journal Article |
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Year |
2012 |
Publication |
Phys. Procedia |
Abbreviated Journal |
Phys. Procedia |
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36 |
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72-76 |
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Keywords |
NbN SSPD, SNSPD |
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Abstract |
Superconducting single-photon detectors (SSPD) is typically 100 nm-wide supercondiucting strip in a shape of meander made of 4-nm-thick film. To reduce response time and increase voltage response a parallel connection of the strips was proposed. Recently we demonstrated that reduction of the strip width improves the quantum effciency of such a detector at wavelengths longer than 1.5 μm. Being encourage by this progress in quantum effciency we improved the fabrication process and made parallel-wire SSPD with 40-nm-wide strips covering total area of 10 μm x 10 μm. In this paper we present the results of the characterization of such a parallel-wire SSPD at 10.6 μm wavelength and demonstrate linear dependence of the count rate on the light power as it should be in case of single-photon response. |
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1875-3892 |
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1382 |
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Nikoghosyan, A. S.; Martirosyan, R. M.; Hakhoumian, A. A.; Makaryan, A. H.; Tadevosyan, V. R.; Goltsman, G. N.; Antipov, S. V. |
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Title |
Effect of absorption on the efficiency of THz radiation generation in a nonlinear crystal placed into a waveguide |
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Journal Article |
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Year |
2018 |
Publication |
Armenian J. Phys. |
Abbreviated Journal |
Armenian J. Phys. |
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11 |
Issue |
4 |
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257-262 |
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Keywords |
THz, waveguide, nonlinear crystal |
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The effect of THz radiation absorption on the efficiency of generation of coherent THz radiation in a nonlinear optical crystal placed into a metal rectangular waveguide is studied. The efficiency of the nonlinear conversion of optical laser radiation to the THz band is also a function of the phase-matching (PM) condition inside the nonlinear crystal. The method of partial filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. Phase matching was obtained by the proper choice of the thickness of the nonlinear crystal, namely the degree of partial filling of the waveguide. We have studied the THz radiation attenuation caused by the losses in both the metal walls of the waveguide and in the crystal, taking into account the dimension of the cross section of the waveguide, the degree of partial filling and its dielectric constant. |
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1829-1171 |
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1291 |
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Vasilev, D. D.; Malevannaya, E. I.; Moiseev, K. M.; Zolotov, P. I.; Antipov, A. V.; Vakhtomin, Y. B.; Smirnov, K. V. |
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Title |
Influence of deposited material energy on superconducting properties of the WSi films |
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Conference Article |
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2020 |
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IOP Conf. Ser.: Mater. Sci. Eng. |
Abbreviated Journal |
IOP Conf. Ser.: Mater. Sci. Eng. |
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Volume |
781 |
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012013 (1 to 6) |
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Keywords |
WSi SSPD, SNSPD |
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WSi thin films have the advantages for creating SNSPDs with a large active area or array of detectors on a single substrate due to the amorphous structure. The superconducting properties of ultrathin WSi films substantially depends on their structure and thickness as the NbN films. Scientific groups investigating WSi films mainly focused only on changes of their thickness and the ratio of the components on the substrate at room temperature. This paper presents experiments to determine the effect of the bias potential on the substrate, the temperature of the substrate, and the peak power of pulsed magnetron sputtering, which is the equivalent of ionization, a tungsten target, on the surface resistance and superconducting properties of the WSi ultrathin films. The negative effect of the substrate temperature and the positive effect of the bias potential and the ionization coefficient (peak current) allow one to choose the best WSi films formation mode for SNSPD: substrate temperature 297 K, bias potential -60 V, and peak current 3.5 A. |
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1757-899X |
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1798 |
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Antipov, A. V.; Seleznev, V. A.; Vakhtomin, Y. B.; Morozov, P. V.; Vasilev, D. D.; Malevannaya, E. I.; Moiseev, K. M.; Smirnov, K. |
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Title |
Investigation of WSi and NbN superconducting single-photon detectors in mid-IR range |
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Conference Article |
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Year |
2020 |
Publication |
IOP Conf. Ser.: Mater. Sci. Eng. |
Abbreviated Journal |
IOP Conf. Ser.: Mater. Sci. Eng. |
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Volume |
781 |
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012011 (1 to 5) |
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Keywords |
WSi, NbN SSPD, SNSPD |
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Spectral characteristics of WSi and NbN superconducting single-photon detectors with different surface resistance and width of nanowire strips have been investigated in the wavelength range of 1.3-2.5 μm. WSi structures with narrower strips demonstrated better performance for detection of single photons in longer wavelength range. The difference in normalized photon count rate for such structures reaches one order of magnitude higher in comparison with structures based on NbN thin films at 2.5 μm. |
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1757-899X |
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1799 |
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Iomdina, E. N.; Seliverstov, S.; Sianosyan, A.; Teplyakova, K.; Rusova, A.; Goltsman, G. |
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Title |
The prospects of using the radiation for the assessment of corneal and scleral hydration |
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Abstract |
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Year |
2016 |
Publication |
Acta Ophthalmol. |
Abbreviated Journal |
Acta Ophthalmol. |
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94 |
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BWO, avalanche transit‐time diode, medicine, biology |
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Abstract |
Purpose
An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells – the cornea and the sclera. THz systems creating images in reflected beams are likely to become ideal instruments of noninvasive testing of corneal and scleral hydration degree as THz radiation is highly sensitive to water content. The paper aims at studying the transmittance and reflectance spectra of the cornea and the sclera of rabbit and human eyes, as well as those of the whole rabbit eye, in the frequency range of 0.13–0.32 THz.
Methods
The experiments were carried out on 3 corneas and 3 rabbit scleras, 2 whole rabbit eyes, and 3 human healthy adult scleras using a specially developed THz system based on reliable and easy‐to‐use continuous wave sources: a backward‐wave oscillator and an avalanche transit‐time diode.
Results
The transmittance spectra of the cornea and the sclera and the dependence of the reflection coefficient of these tissues in THz range on water percentage content were determined. Comparison of the rabbit cornea hydrated from 73.2% to 76.3% concentration by mass demonstrated an approximately linear relationship between THz reflectivity and water concentration. The decrease of free water concentration by 1% leads to a drop of the reflectance coefficient by 13%. The parameters studied displayed noticeable differences between the sclera and the cornea of rabbits and between rabbit sclera and human sclera.
Conclusions
Preliminary results demonstrate that the proposed technique, based on continuous THz radiation, may be used to create a device for noninvasive testing of corneal and scleral hydration, which has good potential of wide‐scale practical application.
The work was supported by the Russian Foundation of Basic Research (grant No.15‐29‐03843) |
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1755375X |
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1333 |
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