| Records |
| 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 |
| Call Number |
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Serial |
1335 |
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| Author |
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 |
|
| 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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| Notes |
PMID:33834684; PMCID:PMC8027227 |
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no |
| Call Number |
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Serial |
1258 |
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| Author |
Sidorova, Maria V.; Divochiy, Alexander V.; Vakhtomin, Yury B.; Smirnov, Konstantin V. |
| Title |
Ultrafast superconducting single-photon detector with a reduced active area coupled to a tapered lensed single-mode fiber |
Type |
Journal Article |
| Year |
2015 |
Publication |
J. Nanophoton. |
Abbreviated Journal |
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| Volume |
9 |
Issue |
1 |
Pages |
093051 |
| Keywords |
SSPD, SNSPD |
| Abstract |
This paper presents an ultrafast niobium nitride (NbN) superconducting single-photon detector (SSPD) with an active area of 3×3 μm2 that offers better timing performance metrics than the previous SSPD with an active area of 7×7 μm2. The improved SSPD demonstrates a record timing jitter (<25 ps), an ultrashort recovery time (<2 ns), an extremely low dark count rate, and a high detection efficiency in a wide spectral range from visible part to near infrared. The record parameters were obtained due to the development of a new technique providing effective optical coupling between a detector with a reduced active area and a standard single-mode telecommunication fiber. The advantages of the new approach are experimentally confirmed by taking electro-optical measurements. |
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Edition |
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| ISSN |
1934-2608 |
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| Notes |
10.1117/1.JNP.9.093051 |
Approved |
no |
| Call Number |
RPLAB @ sasha @ |
Serial |
1052 |
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| 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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Spie |
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Approved |
no |
| Call Number |
10.1117/1.Oe.60.8.082019 |
Serial |
1260 |
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| Author |
Verevkin, A. A.; Ptitsina, N. G.; Smirnov, K. V.; Voronov, B. M.; Gol’tsman, G. N.; Gershenson, E. M.; Yngvesson, K. S. |
| Title |
Multiple Andreev reflection in hybrid AlGaAs/GaAs structures with superconducting NbN contacts |
Type |
Journal Article |
| Year |
1999 |
Publication |
Semicond. |
Abbreviated Journal |
Semicond. |
| Volume |
33 |
Issue |
5 |
Pages |
551-554 |
| Keywords |
2DEG, AlGaAs/GaAs heterostructures |
| Abstract |
The conductivity of hybrid microstructures with superconducting contacts made of niobium nitride to a semiconductor with a two-dimensional electron gas in a AlGaAs/GaAs heterostructure has been investigated. Distinctive features of the behavior of the conductivity indicate the presence of multiple Andreev reflection at scattering centers in the normal region near the superconductor-semiconductor boundary. |
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| ISSN |
1063-7826 |
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no |
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Serial |
1571 |
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| Author |
Men’shchikov, E. M.; Gogidze, I. G.; Sergeev, A. V.; Elant’ev, A. I.; Kuminov, P. B.; Gol’tsman, G. N.; Gershenzon, E. M. |
| Title |
Superconducting fast detector based on the nonequilibrium inductance response of a film of niobium nitride |
Type |
Journal Article |
| Year |
1997 |
Publication |
Tech. Phys. Lett. |
Abbreviated Journal |
Tech. Phys. Lett. |
| Volume |
23 |
Issue |
6 |
Pages |
486-488 |
| Keywords |
NbN KID |
| Abstract |
A new type of fast detector is proposed, whose operation is based on the variation of the kinetic inductance of a superconducting film caused by nonequilibrium quasiparticles created by the electromagnetic radiation. The speed of the detector is determined by the rate of multiplication of photo-excited quasiparticles, and is nearly independent of the temperature, being less than 1 ps for NbN. Models based on the Owen-Scalapino scheme give a good description of the experimentally determined dependence of the power-voltage sensitivity of the detector on the modulation frequency. The lifetime of the quasiparticles is determined, and it is shown that the reabsorption of nonequilibrium phonons by the condensate has a substantial effect even in ultrathin NbN films 5 nm thick, and results in the maximum possible quantum yield. A low concentration of equilibrium quasiparticles and a high quantum yield result in a detectivity D*=1012 W−1·Hz1/2 at a temperature T=4.2 K and D*=1016 W−1·cm· Hz1/2 at T=1.6 K. |
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1063-7850 |
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Approved |
no |
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Serial |
1593 |
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| Author |
Mel’nikov, A. P.; Gurvich, Y. A.; Shestakov, L. N.; Gershenzon, E. M. |
| Title |
Magnetic field effects on the nonohmic impurity conduction of uncompensated crystalline silicon |
Type |
Journal Article |
| Year |
2001 |
Publication |
Jetp Lett. |
Abbreviated Journal |
Jetp Lett. |
| Volume |
73 |
Issue |
1 |
Pages |
44-47 |
| Keywords |
uncompensated crystalline silicon, nonohmic impurity conduction, magnetic field |
| Abstract |
The impurity conduction of a series of crystalline silicon samples with the concentration of major impurity N ≈ 3 × 1016 cm−3 and with a varied, but very small, compensation K was measured as a function of the electric field E in various magnetic fields H-σ(H, E). It was found that, at K < 10−3 and in moderate E, where these samples are characterized by a negative nonohmicity (dσ(0, E)/dE < 0), the ratio σ(H, E)/σ(0, E) > 1 (negative magnetoresistance). With increasing E, these inequalities are simultaneously reversed (positive nonohmicity and positive magnetoresistance). It is suggested that both negative and positive nonohmicities are due to electron transitions in electric fields from impurity ground states to states in the Mott-Hubbard gap. |
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0021-3640 |
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no |
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Serial |
1752 |
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Gol’tsman, G. N.; Smirnov, K. V. |
| Title |
Electron-phonon interaction in a two-dimensional electron gas of semiconductor heterostructures at low temperatures |
Type |
Journal Article |
| Year |
2001 |
Publication |
Jetp Lett. |
Abbreviated Journal |
Jetp Lett. |
| Volume |
74 |
Issue |
9 |
Pages |
474-479 |
| Keywords |
2DEG, AlGaAs/GaAs heterostructures |
| Abstract |
Theoretical and experimental works devoted to studying electron-phonon interaction in the two-dimensional electron gas of semiconductor heterostructures at low temperatures in the case of strong heating in an electric field under quasi-equilibrium conditions and in a quantizing magnetic field perpendicular to the 2D layer are considered. |
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0021-3640 |
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По итогам проектов российского фонда фундаментальных исследований. Проект РФФИ # 98-02-16897 Электрон-фононное взаимодействие в двумерном электронном газе полупроводниковых гетероструктур при низких температурах |
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no |
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1541 |
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| Author |
Morozov, D. V.; Smirnov, K. V.; Smirnov, A. V.; Lyakhov, V. A.; Goltsman, G. N. |
| Title |
A millimeter-submillimeter phonon-cooled hot-electron bolometer mixer based on two-dimensional electron gas in an AlGaAs/GaAs heterostructure |
Type |
Journal Article |
| Year |
2005 |
Publication |
Semicond. |
Abbreviated Journal |
Semicond. |
| Volume |
39 |
Issue |
9 |
Pages |
1082-1086 |
| Keywords |
2D electron gas, AlGaAs/GaAs heterostructures, mixers |
| Abstract |
Experimental results obtained by studying the main characteristics of a millimeter-submillimeter wave mixer based on the hot-electron effect in a two-dimensional electron gas in a AlGaAs/GaAs heterostructure with a phonon-scattering cooling mechanism for charge carriers are reported. The gain bandwidth of the mixer is 4 GHz, the internal conversion losses are 13 dB, and the optimum local-oscillator power is 0.5 μW (for a mixer area of 1 μm2). It is shown that a millimeter-submillimeter-wave receiver with a noise temperature of 1900 K can be developed on the basis of a AlGaAs/GaAs mixer. This mixer also appears to be promising for use in array receiver elements. |
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1063-7826 |
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no |
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1463 |
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Verevkin, A. A.; Ptitsina, N. G.; Smirnov, K. V.; Gol’tsman, G. N.; Gershenzon, E. M.; Ingvesson, K. S. |
| Title |
Direct measurements of energy relaxation times on an AlGaAs/GaAs heterointerface in the range 4.2–50 K |
Type |
Journal Article |
| Year |
1996 |
Publication |
JETP Lett. |
Abbreviated Journal |
JETP Lett. |
| Volume |
64 |
Issue |
5 |
Pages |
404-409 |
| Keywords |
2DEG, AlGaAs/GaAs heterostructures |
| Abstract |
The temperature dependence of the energy relaxation time τe (T) of a two-dimensional electron gas at an AlGaAs/GaAs heterointerface is measured under quasiequilibrium conditions in the region of the transition from scattering by acoustic phonons to scattering with the participation of optical phonons. The temperature interval of constant τe, where scattering by the deformation potential predominates, is determined. In the preceding, low-temperature region, where piezoacoustic and deformation-potential-induced scattering processes coexist, τ e decreases slowly with increasing temperature. Optical phonons start to participate in the scattering processes at T∼25 K (the characteristic phonon lifetime was equal to τLOτ4.5 ps). The energy losses calculated from the τe data in a model with an effective nonequilibrium electron temperature agree with the published data obtained under strong heating conditions. |
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0021-3640 |
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http://jetpletters.ru/ps/981/article_14955.shtml (“Прямые измерения времен энергетической релаксации на гетерогранице AlGaAs/GaAs в диапазоне 4.2 – 50 К”) |
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1608 |
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