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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. |
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Title |
Terahertz scanning of the rabbit cornea with experimental UVB-induced damage: in vivo assessment of hydration and its verification |
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Journal Article |
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Year |
2021 |
Publication |
J. Biomed. Opt. |
Abbreviated Journal |
J. Biomed. Opt. |
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Volume |
26 |
Issue |
4 |
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Keywords |
medicine; scheimpflug imaging; UVB; confocal microscopy; cornea; optical coherent tomography; rabbit eyes; terahertz radiation |
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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. |
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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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1258 |
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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. |
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Title |
Time-resolved measurements of light–current characteristic and mode competition in pulsed THz quantum cascade laser |
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Journal Article |
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Year |
2021 |
Publication |
Optical Engineering |
Abbreviated Journal |
Optical Engineering |
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60 |
Issue |
8 |
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1-8 |
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Keywords |
HEB, terahertz pulse generation, terahertz pulse detection, QCL, quantum cascade laser, superconducting hot electron bolometer |
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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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10.1117/1.Oe.60.8.082019 |
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1260 |
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Ozhegov, R.; Elezov, M.; Kurochkin, Y.; Kurochkin, V.; Divochiy, A.; Kovalyuk, V.; Vachtomin, Y.; Smirnov, K.; Goltsman, G. |
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Quantum key distribution over 300 |
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Conference Article |
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2014 |
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Proc. SPIE |
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Proc. SPIE |
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9440 |
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1F (1 to 9) |
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SSPD, SNSPD applicatins, quantum key distribution, QKD |
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We discuss the possibility of polarization state reconstruction and measurement over 302 km by Superconducting Single- Photon Detectors (SSPDs). Because of the excellent characteristics and the possibility to be effectively coupled to singlemode optical fiber many applications of the SSPD have already been reported. The most impressive one is the quantum key distribution (QKD) over 250 km distance. This demonstration shows further possibilities for the improvement of the characteristics of quantum-cryptographic systems such as increasing the bit rate and the quantum channel length, and decreasing the quantum bit error rate (QBER). This improvement is possible because SSPDs have the best characteristics in comparison with other single-photon detectors. We have demonstrated the possibility of polarization state reconstruction and measurement over 302.5 km with superconducting single-photon detectors. The advantage of an autocompensating optical scheme, also known as “plugandplay” for quantum key distribution, is high stability in the presence of distortions along the line. To increase the distance of quantum key distribution with this optical scheme we implement the superconducting single photon detectors (SSPD). At the 5 MHz pulse repetition frequency and the average photon number equal to 0.4 we measured a 33 bit/s quantum key generation for a 101.7 km single mode ber quantum channel. The extremely low SSPD dark count rate allowed us to keep QBER at 1.6% level. |
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SPIE |
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Orlikovsky, A. A. |
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International Conference on Micro- and Nano-Electronics |
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RPLAB @ sasha @ ozhegov2014quantum |
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1048 |
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Rath, P.; Vetter, A.; Kovalyuk, V.; Ferrari, S.; Kahl, O.; Nebel, C.; Goltsman, G. N.; Korneev, A.; Pernice, W. H. P. |
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Travelling-wave single-photon detectors integrated with diamond photonic circuits: operation at visible and telecom wavelengths with a timing jitter down to 23 ps |
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Conference Article |
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2016 |
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Integrated Optics: Devices, Mat. Technol. XX |
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Integrated Optics: Devices, Mat. Technol. XX |
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9750 |
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135-142 |
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SSPD, Superconducting Nanowire Single-Photon Detector, SNSPD, Single Photon Detector, Diamond Photonics, Diamond Integrated Optics, Diamond Waveguides, Integrated Optics, Low Timing Jitter |
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We report on the design, fabrication and measurement of travelling-wave superconducting nanowire single-photon detectors (SNSPDs) integrated with polycrystalline diamond photonic circuits. We analyze their performance both in the near-infrared wavelength regime around 1600 nm and at 765 nm. Near-IR detection is important for compatibility with the telecommunication infrastructure, while operation in the visible wavelength range is relevant for compatibility with the emission line of silicon vacancy centers in diamond which can be used as efficient single-photon sources. Our detectors feature high critical currents (up to 31 μA) and high performance in terms of efficiency (up to 74% at 765 nm), noise-equivalent power (down to 4.4×10-19 W/Hz1/2 at 765 nm) and timing jitter (down to 23 ps). |
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Spie |
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Broquin, J.-E.; Conti, G.N. |
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1210 |
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Shcherbatenko, M.; Lobanov, Y.; Semenov, A.; Kovalyuk, V.; Korneev, A.; Ozhegov, R.; Kaurova, N.; Voronov, B.; Goltsman, G. |
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Coherent detection of weak signals with superconducting nanowire single photon detector at the telecommunication wavelength |
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Conference Article |
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2017 |
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Proc. SPIE |
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Proc. SPIE |
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10229 |
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0G (1 to 12) |
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SSPD mixer, SNSPD, coherent detection, weak signal detection, superconducting nanostructures |
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Achievement of the ultimate sensitivity along with a high spectral resolution is one of the frequently addressed problems, as the complication of the applied and fundamental scientific tasks being explored is growing up gradually. In our work, we have investigated performance of a superconducting nanowire photon-counting detector operating in the coherent mode for detection of weak signals at the telecommunication wavelength. Quantum-noise limited sensitivity of the detector was ensured by the nature of the photon-counting detection and restricted by the quantum efficiency of the detector only. Spectral resolution given by the heterodyne technique and was defined by the linewidth and stability of the Local Oscillator (LO). Response bandwidth was found to coincide with the detector’s pulse width, which, in turn, could be controlled by the nanowire length. In addition, the system noise bandwidth was shown to be governed by the electronics/lab equipment, and the detector noise bandwidth is predicted to depend on its jitter. As have been demonstrated, a very small amount of the LO power (of the order of a few picowatts down to hundreds of femtowatts) was required for sufficient detection of the test signal, and eventual optimization could lead to further reduction of the LO power required, which would perfectly suit for the foreseen development of receiver matrices and the need for detection of ultra-low signals at a level of less-than-one-photon per second. |
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Spie |
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Prochazka, I.; Sobolewski, R.; James, R.B. |
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Photon counting applications |
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10.1117/12.2267724 |
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1201 |
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