| Records |
| Author |
Ovchinnikov, O. V.; Perepelitsa, A. S.; Smirnov, M. S.; Latyshev, A. N.; Grevtseva, I. G.; Vasiliev, R. B.; Goltsman, G. N.; Vitukhnovsky, A. G. |
| Title |
Luminescence of colloidal Ag2S/ZnS core/shell quantum dots capped with thioglycolic acid |
Type |
Journal Article |
| Year |
2020 |
Publication |
J. Luminescence |
Abbreviated Journal |
J. Luminescence |
| Volume |
220 |
Issue |
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Pages  |
117008 (1 to 7) |
| Keywords |
Ag2S QD, quantum dots |
| 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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| ISSN |
0022-2313 |
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no |
| Call Number |
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Serial |
1267 |
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| Author |
Rasulova, G. K.; Pentin, I. V.; Goltsman, G. N. |
| Title |
Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations |
Type |
Journal Article |
| Year |
2019 |
Publication |
AIP Advances |
Abbreviated Journal |
AIP Advances |
| Volume |
9 |
Issue |
10 |
Pages |
105220 |
| Keywords |
GaAs/AlGaAs superlattice, SL, NbN HEB |
| Abstract |
Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level. |
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| ISSN |
2158-3226 |
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no |
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Serial |
1274 |
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| Author |
Vodolazov, D. Y.; Korneeva, Y. P.; Semenov, A. V.; Korneev, A. A.; Goltsman, G. N. |
| Title |
Vortex-assisted mechanism of photon counting in a superconducting nanowire single-photon detector revealed by external magnetic field |
Type |
Journal Article |
| Year |
2015 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
| Volume |
92 |
Issue |
10 |
Pages |
104503 (1 to 9) |
| Keywords |
SSPD, SNSPD |
| Abstract |
We use an external magnetic field to probe the detection mechanism of a superconducting nanowire single-photon detector. We argue that the hot belt model (which assumes partial suppression of the superconducting order parameter Δ across the whole width of the superconducting nanowire after absorption of the photon) does not explain observed weak-field dependence of the photon count rate (PCR) for photons with λ=450nm and noticeable decrease of PCR (with increasing the magnetic field) in a range of the currents for photons with wavelengths λ=450–1200nm. Found experimental results for all studied wavelengths can be explained by the vortex hot spot model (which assumes partial suppression of Δ in the area with size smaller than the width of the nanowire) if one takes into account nucleation and entrance of the vortices to the photon induced hot spot and their pinning by the hot spot with relatively large size and strongly suppressed Δ. |
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Edition |
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| ISSN |
1098-0121 |
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no |
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Serial |
1343 |
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| Author |
Iomdina, E. N.; Goltsman, G. N.; Seliverstov, S. V.; Sianosyan, A. A.; Teplyakova, K. O.; Rusova, A. A. |
| Title |
Study of transmittance and reflectance spectra of the cornea and the sclera in the THz frequency range |
Type |
Journal Article |
| Year |
2016 |
Publication |
J. Biomed. Opt. |
Abbreviated Journal |
J. Biomed. Opt. |
| Volume |
21 |
Issue |
9 |
Pages |
97002 (1 to 5) |
| Keywords |
BWO, IMPATT diode, Schottky diode, medicine, animals, cornea, physiology, humans, rabbits, sclera diagnostic imaging, physiology |
| Abstract |
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. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application. |
| Address |
Moscow State Pedagogical University, Department of Physics, 29 Malaya Pirogovskaya Street, Moscow 119435, Russia |
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English |
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| ISSN |
1083-3668 |
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| Notes |
PMID:27626901 |
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no |
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Serial |
1335 |
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| Author |
Korneeva, Y. P.; Mikhailov, M. Y.; Pershin, Y. P.; Manova, N. N.; Divochiy, A. V.; Vakhtomin, Y. B.; Korneev, A. A.; Smirnov, K. V.; Sivakov, A. G.; Devizenko, A. Y.; Goltsman, G. N. |
| Title |
Superconducting single-photon detector made of MoSi film |
Type |
Journal Article |
| Year |
2014 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
| Volume |
27 |
Issue |
9 |
Pages |
095012 |
| Keywords |
SSPD, SNSPD |
| Abstract |
We fabricated and characterized nanowire superconducting single-photon detectors made of 4 nm thick amorphous Mox Si1−x films. At 1.7 K the best devices exhibit a detection efficiency (DE) up to 18% at 1.2 $\mu {\rm m}$ wavelength of unpolarized light, a characteristic response time of about 6 ns and timing jitter of 120 ps. The DE was studied in wavelength range from 650 nm to 2500 nm. At wavelengths below 1200 nm these detectors reach their maximum DE limited by photon absorption in the thin MoSi film. |
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IOP Publishing |
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| ISSN |
0953-2048 |
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no |
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RPLAB @ sasha @ korneeva2014superconducting |
Serial |
1044 |
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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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| ISSN |
0953-2048 |
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no |
| Call Number |
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Serial |
1358 |
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| Author |
Korneev, A.; Korneeva, Y.; Florya, I.; Voronov, B.; Goltsman, G. |
| Title |
Spectral sensitivity of narrow strip NbN superconducting single-photon detector |
Type |
Conference Article |
| Year |
2011 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
8072 |
Issue |
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Pages |
80720G (1 to 9) |
| Keywords |
NbN SSPD, SNSPD |
| Abstract |
Superconducting single-photon detector (SSPD) is patterned from 4-nm-thick NbN film deposited on sapphire substrate as a 100-nm-wide strip. Due to its high detection efficiency, low dark counts, and picosecond timing jitter SSPD has become a competitor to the InGaAs avalanche photodiodes at 1550 nm and longer wavelengths. Although the SSPD is operated at liquid helium temperature its efficient single-mode fibre coupling enabled its usage in many applications ranging from single-photon sources research to quantum cryptography. In our strive to increase the detection efficiency at 1550 nm and longer wavelengths we developed and fabricated SSPD with the strip almost twice narrower compared to the standard 100 nm. To increase the voltage response of the device we utilized cascade switching mechanism: we connected 50-nm-wide and 10-μm-long strips in parallel covering the area of 10 μmx10 μm. Absorption of a photon breaks the superconductivity in a strip leading to the bias current redistribution between other strips followed their cascade switching. As the total current of all the strips about is 1 mA by the order of magnitude the response voltage of such an SSPD is several times higher compared to the traditional meander-shaped SSPDs. In middle infrared (about 3 μm wavelength) these devices have the detection efficiency several times higher compared to the traditional SSPDs. |
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SPIE |
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Editor |
Fiurásek, J.; Prochazka, I. |
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Photon Counting Applications, Quantum Optics, and Quantum Information Transfer and Processing III |
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Approved |
no |
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Serial |
1387 |
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| Author |
Antipov, S.; Trifonov, A.; Krause, S.; Meledin, D.; Kaurova, N.; Rudzinski, M.; Desmaris, V.; Belitsky, V.; Goltsman, G. |
| Title |
Improved bandwidth of a 2 THz hot-electron bolometer heterodyne mixer fabricated on sapphire with a GaN buffer layer |
Type |
Journal Article |
| Year |
2019 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
| Volume |
32 |
Issue |
7 |
Pages |
075003 |
| Keywords |
NbN HEB mixer, GaN buffer layer, sapphire substrate |
| Abstract |
We report on the signal-to-noise and gain bandwidth of a niobium nitride (NbN) hot-electron bolometer (HEB) mixer at 2 THz fabricated on a sapphire substrate with a GaN buffer layer. Two mixers with different DC properties and geometrical dimensions were studied and they demonstrated very close bandwidth performance. The signal-to-noise bandwidth is increased to 8 GHz in comparison to the previous results, obtained without a buffer-layer. The data were taken in a quasi-optical system with the use of the signal-to-noise method, which is close to the signal levels used in actual astrophysical observations. We find an increase of the gain bandwidth to 5 GHz. The results indicate that prior results obtained on a substrate of crystalline GaN can also be obtained on a conventional sapphire substrate with a few micron MOCVD-deposited GaN buffer-layer. |
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IOP Publishing |
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no |
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Antipov_2019 |
Serial |
1277 |
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| Author |
Goltsman, G. N. |
| Title |
Ultrafast nanowire superconducting single-photon detector with photon number resolving capability |
Type |
Conference Article |
| Year |
2009 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
7236 |
Issue |
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Pages |
72360D (1 to 11) |
| Keywords |
PNR NbN SSPD, SNSPD, superconducting single-photon detectors, photon number resolving detectors, ultrathin NbN films |
| Abstract |
In this paper we present a review of the state-of-the-art superconducting single-photon detector (SSPD), its characterization and applications. We also present here the next step in the development of SSPD, i.e. photon-number resolving SSPD which simultaneously features GHz counting rate. We have demonstrated resolution up to 4 photons with quantum efficiency of 2.5% and 300 ps response pulse duration providing very short dead time. |
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SPIE |
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Arakawa, Y.; Sasaki, M.; Sotobayashi, H. |
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no |
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Serial |
1403 |
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| Author |
Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, T.; Bustarret, E. |
| Title |
Relaxation of the resistive superconducting state in boron-doped diamond films |
Type |
Journal Article |
| Year |
2016 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
| Volume |
93 |
Issue |
6 |
Pages |
064506 |
| Keywords |
boron-doped diamond films, resistive superconducting state, relaxation time |
| Abstract |
We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5×1021cm−3 and a critical temperature of about 2K. By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T−2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc. |
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2469-9950 |
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no |
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1167 |
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