| Records |
| Author |
Zolotov, P.; Divochiy, A.; Korneeva, Yu.; Vakhtomin, Yu.; Seleznev, V.; Smirnov, K. |
| Title |
Capability investigation of superconducting single-photon detectors, optimized for 800–1200 nm spectrum range |
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Miscellaneous |
| Year |
2015 |
Publication |
3th ICQT |
Abbreviated Journal |
3th ICQT |
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SSPD, SNSPD |
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Hotel Ukraina (Radisson), Moscow |
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1253 |
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Zolotov, P.; Vakhtomin, Yu.; Divochiy, A.; Seleznev, V.; Morozov, P.; Smirnov, K. |
| Title |
High-efficiency single-photon detectors based on NbN films |
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Miscellaneous |
| Year |
2013 |
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SSPD, SNSPD |
| Abstract |
We present our resent results in development and testing of Superconducting Single-Photon Detectors (SSPD) with detection efficiencies greater than 85%. High values of obtained results are assigned to proposed design of the detector with integrated resonator structure, including two-layer optical cavity and anti-reflective coating (ARC). |
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1254 |
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Kovaluyk, V.; Lazarenko, P.; Kozyukhin, S.; An, P.; Prokhodtsov, A.; Goltsman, G.; Sherchenkov, A. |
| Title |
Influence of the phase state of Ge2Sb2Te5 thin cover on the parameters of the optical waveguide structures |
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Abstract |
| Year |
2019 |
Publication |
Proc. Amorphous and Nanostructured Chalcogenides |
Abbreviated Journal |
Proc. Amorphous and Nanostructured Chalcogenides |
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Pages |
47-48 |
| Keywords |
optical waveguides |
| Abstract |
The fast switching time of Ge-Sb-Te thin films between amorphous and crystalline states initiated by laser beam as well as significant change of their optical properties and the preservation of metastable states for tens of years open wide perspectives for the application of these materials to fully optical devices [1], including high-speed optical memory [2]. Here we study optical properties of the Ge2Sb2Te5 (GST225) thin films integrated with on-chip silicon nitride O-ring resonator. The rib waveguide of the resonator was formed the first stage of e-beam lithography and subsequent reactive-ion etching. We used the second stage of e-beam lithography combining with lift-off method for the formation of GST225 active region on the resonator ring surface. The amorphous GST225 thin films were prepared by magnetron sputtering, and were capped by thin silicon oxide on their tops. The length of the GST225 active region varied from 0.1 to 20 μ m. Crystallization of amorphous thin films was carried out at the temperature of 400 °C for 30 minutes. Auger electron spectroscopy and transmission electron microscopy were used for studying composition and structure of investigated GST225thin films, respectively. It was observed that crystallization of amorphous GST225 film lead to a decrease of the optical power, transmitted through the waveguide. Comparison of the optical transmittance of O-ring resonators before and after the GST225 deposition allowed to identify the change in the Q-factor and the wavelength peak shift. This can be explained by the differences of the complex refractive indexes of GST225 thin films in the amorphous and crystalline states. From the measurement data, the GST225 effective refractive index was extracted depending on the ring waveguide width of the resonator for a telecommunication wavelength of 1550 nm. |
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Technical University of Moldova |
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no |
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1281 |
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Verevkin, A. A.; Ptitsina, N. G.; Chulcova, G. M.; Gol'Tsman, G. N.; Gershenzon, E. M.; Yngvesson, K. S. |
| Title |
Determination of the limiting mobility of a two-dimensional electron gas in AlxGa1-xAs/GaAs heterostructures and direct measurement of the energy relaxation time |
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Journal Article |
| Year |
1996 |
Publication |
Phys. Rev. B Condens. Matter. |
Abbreviated Journal |
Phys. Rev. B Condens. Matter. |
| Volume |
53 |
Issue |
12 |
Pages |
R7592-R7595 |
| Keywords |
2DEG, AlGaAs/GaAs heterostructures |
| Abstract |
We present results for a method to measure directly the energy relaxation time (τe) for electrons in a single AlxGa1−xAs/GaAs heterojunction; measurements were performed from 1.6 to 15 K under quasiequilibrium conditions. We find τeαT−1 below 4 K, and τe independent of T above 4 K. We have also measured the energy-loss rate, ⟨Q⟩, by the Shubnikov-de Haas technique, and find ⟨Q⟩α(T3e−T3) for T<~4.2 K; Te is the electron temperature. The values and temperature dependence of τe and ⟨Q⟩ for T<4 K agree with calculations based on piezoelectric and deformation potential acoustic phonon scattering. At 4.2 K, we can also estimate the momentum relaxation time, τm, from our measured τe. This leads to a preliminary estimate of the phonon-limited mobility at 4.2 K of μ=3×107 cm2/Vs (ns=4.2×1011 cm−2), which agrees well with published numerical calculations, as well as with an earlier indirect estimate based on measurements on a sample with much higher mobility. |
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0163-1829 |
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PMID:9982274 |
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no |
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1612 |
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Iomdina, E. N.; Seliverstov, S. V.; Teplyakova, K. O.; Jani, E. V.; Pozdniakova, V. V.; Polyakova, O. N.; Goltsman, G. N. |
| Title |
Terahertz scanning of the rabbit cornea with experimental UVB-induced damage: in vivo assessment of hydration and its verification |
Type |
Journal Article |
| Year |
2021 |
Publication |
J. Biomed. Opt. |
Abbreviated Journal |
J. Biomed. Opt. |
| Volume |
26 |
Issue |
4 |
Pages |
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| Keywords |
medicine; scheimpflug imaging; UVB; confocal microscopy; cornea; optical coherent tomography; rabbit eyes; terahertz radiation |
| Abstract |
SIGNIFICANCE: Water content plays a vital role in the normally functioning visual system; even a minor disruption in the water balance may be harmful. Today, no direct method exists for corneal hydration assessment, while it could be instrumental in early diagnosis and control of a variety of eye diseases. The use of terahertz (THz) radiation, which is highly sensitive to water content, appears to be very promising. AIM: To find out how THz scanning parameters of corneal tissue measured by an experimental setup, specially developed for in vivo contactless estimations of corneal reflectivity coefficient (RC), are related to pathological changes in the cornea caused by B-band ultraviolet (UVB) exposure. APPROACH: The setup was tested on rabbit eyes in vivo. Prior to the course of UVB irradiation and 1, 5, and 30 days after it, a series of examinations of the corneal state was made. At the same time points, corneal hydration was assessed by measuring RC. RESULTS: The obtained data confirmed the negative impact of UVB irradiation course on the intensity of tear production and on the corneal thickness and optical parameters. A significant (1.8 times) increase in RC on the 5th day after the irradiation course, followed by a slight decrease on the 30th day after it was revealed. The RC increase measured 5 days after the UVB irradiation course generally corresponded to the increase (by a factor of 1.3) of tear production. RC increase occurred with the corneal edema, which was manifested by corneal thickening (by 18.2% in the middle area and 17.6% in corneal periphery) and an increased volume of corneal tissue (by 17.6%). CONCLUSIONS: Our results demonstrate that the proposed approach can be used for in vivo contactless estimation of the reflectivity of rabbit cornea in the THz range and, thereby, of cornea hydration. |
| Address |
National Research University Higher School of Economics, Moscow Institute of Electronics and Mathema, Russia |
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English |
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1083-3668 |
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PMID:33834684; PMCID:PMC8027227 |
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no |
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1258 |
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Morozov, P.; Lukina, M.; Shirmanova, M.; Divochiy, A.; Dudenkova, V.; Gol'tsman, G. N.; Becker, W.; Shcheslavskiy, V. I. |
| Title |
Singlet oxygen phosphorescence imaging by superconducting single-photon detector and time-correlated single-photon counting |
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Journal Article |
| Year |
2021 |
Publication |
Opt. Lett. |
Abbreviated Journal |
Opt. Lett. |
| Volume |
46 |
Issue |
6 |
Pages |
1217-1220 |
| Keywords |
SSPD, SNSPD, applications |
| Abstract |
This Letter presents, to the best of our knowledge, a novel optical configuration for direct time-resolved measurements of luminescence from singlet oxygen, both in solutions and from cultured cells on photodynamic therapy. The system is based on the superconducting single-photon detector, coupled to the confocal scanner that is modified for the near-infrared measurements. The recording of a phosphorescence signal from singlet oxygen at 1270 nm has been done using time-correlated single-photon counting. The performance of the system is verified by measuring phosphorescence from singlet oxygen generated by the photosensitizers commonly used in photodynamic therapy: methylene blue and chlorin e6. The described system can be easily upgraded to the configuration when both phosphorescence from singlet oxygen and fluorescence from the cells can be detected in the imaging mode. Thus, co-localization of the signal from singlet oxygen with the areas inside the cells can be done. |
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0146-9592 |
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PMID:33720151 |
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no |
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1221 |
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Gayduchenko, I.; Xu, S. G.; Alymov, G.; Moskotin, M.; Tretyakov, I.; Taniguchi, T.; Watanabe, K.; Goltsman, G.; Geim, A. K.; Fedorov, G.; Svintsov, D.; Bandurin, D. A. |
| Title |
Tunnel field-effect transistors for sensitive terahertz detection |
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Journal Article |
| Year |
2021 |
Publication |
Nat. Commun. |
Abbreviated Journal |
Nat. Commun. |
| Volume |
12 |
Issue |
1 |
Pages |
543 |
| Keywords |
field-effect transistors, bilayer graphene, BLG |
| Abstract |
The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here, we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG's electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high responsivity (>4 kV/W) and low-noise (0.2 pW/[Formula: see text]) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors' responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor. |
| Address |
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA. bandurin@mit.edu |
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2041-1723 |
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PMID:33483488; PMCID:PMC7822863 |
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no |
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1261 |
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Gorokhov, G.; Bychanok, D.; Gayduchenko, I.; Rogov, Y.; Zhukova, E.; Zhukov, S.; Kadyrov, L.; Fedorov, G.; Ivanov, E.; Kotsilkova, R.; Macutkevic, J.; Kuzhir, P. |
| Title |
THz spectroscopy as a versatile tool for filler distribution diagnostics in polymer nanocomposites |
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Journal Article |
| Year |
2020 |
Publication |
Polymers (Basel) |
Abbreviated Journal |
Polymers (Basel) |
| Volume |
12 |
Issue |
12 |
Pages |
3037 (1 to 14) |
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THz spectroscopy; nanocomposites, percolation threshold, time-domain spectroscopy, time-domain spectrometer, TDS |
| Abstract |
Polymer composites containing nanocarbon fillers are under intensive investigation worldwide due to their remarkable electromagnetic properties distinguished not only by components as such, but the distribution and interaction of the fillers inside the polymer matrix. The theory herein reveals that a particular effect connected with the homogeneity of a composite manifests itself in the terahertz range. Transmission time-domain terahertz spectroscopy was applied to the investigation of nanocomposites obtained by co-extrusion of PLA polymer with additions of graphene nanoplatelets and multi-walled carbon nanotubes. The THz peak of permittivity's imaginary part predicted by the applied model was experimentally shown for GNP-containing composites both below and above the percolation threshold. The physical nature of the peak was explained by the impact on filler particles excluded from the percolation network due to the peculiarities of filler distribution. Terahertz spectroscopy as a versatile instrument of filler distribution diagnostics is discussed. |
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Institute of Photonics, University of Eastern Finland, Yliopistokatu 7, FI-80101 Joensuu, Finland |
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English |
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2073-4360 |
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PMID:33353036; PMCID:PMC7767186 |
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no |
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1780 |
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Pentin, I.; Vakhtomin, Y.; Seleznev, V.; Smirnov, K. |
| Title |
Hot electron energy relaxation time in vanadium nitride superconducting film structures under THz and IR radiation |
Type |
Journal Article |
| Year |
2020 |
Publication |
Sci. Rep. |
Abbreviated Journal |
Sci. Rep. |
| Volume |
10 |
Issue |
1 |
Pages |
16819 |
| Keywords |
VN HEB |
| Abstract |
The paper presents the experimental results of studying the dynamics of electron energy relaxation in structures made of thin (d approximately 6 nm) disordered superconducting vanadium nitride (VN) films converted to a resistive state by high-frequency radiation and transport current. Under conditions of quasi-equilibrium superconductivity and temperature range close to critical (~ Tc), a direct measurement of the energy relaxation time of electrons by the beats method arising from two monochromatic sources with close frequencies radiation in sub-THz region (omega approximately 0.140 THz) and sources in the IR region (omega approximately 193 THz) was conducted. The measured time of energy relaxation of electrons in the studied VN structures upon heating of THz and IR radiation completely coincided and amounted to (2.6-2.7) ns. The studied response of VN structures to IR (omega approximately 193 THz) picosecond laser pulses also allowed us to estimate the energy relaxation time in VN structures, which was ~ 2.8 ns and is in good agreement with the result obtained by the mixing method. Also, we present the experimentally measured volt-watt responsivity (S~) within the frequency range omega approximately (0.3-6) THz VN HEB detector. The estimated values of noise equivalent power (NEP) for VN HEB and its minimum energy level (deltaE) reached NEP@1MHz approximately 6.3 x 10(-14) W/ radicalHz and deltaE approximately 8.1 x 10(-18) J, respectively. |
| Address |
National Research University Higher School of Economics, 20 Myasnitskaya Str., Moscow, 101000, Russia |
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2045-2322 |
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PMID:33033360; PMCID:PMC7546726 |
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no |
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Serial |
1797 |
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Matyushkin, Y.; Danilov, S.; Moskotin, M.; Belosevich, V.; Kaurova, N.; Rybin, M.; Obraztsova, E. D.; Fedorov, G.; Gorbenko, I.; Kachorovskii, V.; Ganichev, S. |
| Title |
Helicity-sensitive plasmonic terahertz interferometer |
Type |
Journal Article |
| Year |
2020 |
Publication |
Nano Lett. |
Abbreviated Journal |
Nano Lett. |
| Volume |
20 |
Issue |
10 |
Pages |
7296-7303 |
| Keywords |
graphene, plasmonic interferometer, radiation helicity, terahertz radiation |
| Abstract |
Plasmonic interferometry is a rapidly growing area of research with a huge potential for applications in the terahertz frequency range. In this Letter, we explore a plasmonic interferometer based on graphene field effect transistor connected to specially designed antennas. As a key result, we observe helicity- and phase-sensitive conversion of circularly polarized radiation into dc photovoltage caused by the plasmon-interference mechanism: two plasma waves, excited at the source and drain part of the transistor, interfere inside the channel. The helicity-sensitive phase shift between these waves is achieved by using an asymmetric antenna configuration. The dc signal changes sign with inversion of the helicity. A suggested plasmonic interferometer is capable of measuring the phase difference between two arbitrary phase-shifted optical signals. The observed effect opens a wide avenue for phase-sensitive probing of plasma wave excitations in two-dimensional materials. |
| Address |
CENTERA Laboratories, Institute of High Pressure Physics, PAS, 01-142 Warsaw, Poland |
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1530-6984 |
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PMID:32903004 |
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1781 |
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