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Saveskul, N. A.; Titova, N. A.; Baeva, E. M.; Semenov, A. V.; Lubenchenko, A. V.; Saha, S.; Reddy, H.; Bogdanov, S. I.; Marinero, E. E.; Shalaev, V. M.; Boltasseva, A.; Khrapai, V. S.; Kardakova, A. I.; Goltsman, G. N. |
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Title |
Superconductivity behavior in epitaxial TiN films points at surface magnetic disorder |
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Miscellaneous |
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2019 |
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arXiv |
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arXiv |
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1-10 |
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We analyze the evolution of the normal and superconducting electronic properties in epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of in the residual resistivity, which becomes dominated by diffusive surface scattering for d≤20nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such a high quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of ∼1012cm−2. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films. |
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1278 |
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Moshkova, M.; Divochiy, A.; Morozov, P.; Vakhtomin, Y.; Antipov, A.; Zolotov, P.; Seleznev, V.; Ahmetov, M.; Smirnov, K. |
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Title |
High-performance superconducting photon-number-resolving detectors with 86% system efficiency at telecom range |
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Journal Article |
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Year |
2019 |
Publication |
J. Opt. Soc. Am. B |
Abbreviated Journal |
J. Opt. Soc. Am. B |
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36 |
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3 |
Pages |
B20 |
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NbN PNR SSPD, SNSPD |
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The use of improved fabrication technology, highly disordered NbN thin films, and intertwined section topology makes it possible to create high-performance photon-number-resolving superconducting single-photon detectors (PNR SSPDs) that are comparable to conventional single-element SSPDs at the telecom range. The developed four-section PNR SSPD has simultaneously an 86±3% system detection efficiency, 35 cps dark count rate, ∼2 ns dead time, and maximum 90 ps jitter. An investigation of the PNR SSPD’s detection efficiency for multiphoton events shows good uniformity across sections. As a result, such a PNR SSPD is a good candidate for retrieving the photon statistics for light sources and quantum key distribution systems. |
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0740-3224 |
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1225 |
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Baksheeva, K.; Vdovydchenko, A.; Gorshkov, K.; Ozhegov, R.; Kinev, N.; Koshelets, V.; Goltsman, G. |
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Study of human skin radiation in the terahertz frequency range |
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Conference Article |
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2019 |
Publication |
J. Phys.: Conf. Ser. |
Abbreviated Journal |
J. Phys.: Conf. Ser. |
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1410 |
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012076 (1 to 5) |
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Keywords |
SIS mixer, SIR, applications, medicine, sympathetic nervous system, SNS |
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The radiation of human skin in the terahertz frequency range under the influence of mental stresses has been studied in the current work. An experimental setup for observation of changes in human skin radiation, which occur under the influence of psychological stresses, by means of a superconducting integrated receiver has been developed. More than 30 volunteers participate in these studies, which allows us to verify presence of correlation between the signals from the superconducting integrated terahertz receiver and other sensors that monitor human mental stress. |
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1742-6588 |
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1272 |
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Nikogosyan, 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 terahertz radiation generation in the metal waveguide partially filled with nonlinear crystal LiNbO3, DAST or ZnTe |
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Journal Article |
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2019 |
Publication |
J. Contemp. Phys. |
Abbreviated Journal |
J. Contemp. Phys. |
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54 |
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1 |
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97-104 |
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nonlinear crystal, THz, waveguide |
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The influence of terahertz (THz) radiation absorption on the efficiency of generation of coherent THz radiation in the system ‘nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide’ has been investigated. The efficiency of the nonlinear frequency conversion of optical laser radiation to the THz range depends on the loss in the system and the fulfillment of the phase-matching (FM) condition in a nonlinear crystal. The method of partially filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. The phase matching is achieved by numerical determination of the thickness of the nonlinear crystal, that is the degree of partial filling of the waveguide. The attenuation of THz radiation caused by losses both in the metal walls of the waveguide and in the crystal was studied, taking into account the dimension of the cross section of the waveguide, the degree of partial filling, and the dielectric constant of the crystal. It is shown that the partial filling of the waveguide with a nonlinear crystal results in an increase in the efficiency of generation of THz radiation by an order of magnitude, owing to the decrease in absorption. |
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1068-3372 |
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1289 |
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Kovaluyk, V.; Lazarenko, P.; Kozyukhin, S.; An, P.; Prokhodtsov, A.; Goltsman, G.; Sherchenkov, A. |
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Title |
Influence of the phase state of Ge2Sb2Te5 thin cover on the parameters of the optical waveguide structures |
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Abstract |
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Year |
2019 |
Publication |
Proc. Amorphous and Nanostructured Chalcogenides |
Abbreviated Journal |
Proc. Amorphous and Nanostructured Chalcogenides |
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47-48 |
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optical waveguides |
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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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1281 |
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Prokhodtsov, A.; Golikov, A.; An, P.; Kovalyuk, V.; Goltsman, G.; Arakelyan, S.; Evlyukhin, A.; Kalachev, A.; Naumov, A. |
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Effect of silicon oxide coating on a silicon nitride focusing grating coupler efficiency |
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Conference Article |
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2019 |
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EPJ Web Conf. |
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EPJ Web Conf. |
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220 |
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02009 |
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grating coupler, SiO2 |
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The dependence of the efficiency of the focusing grating couplers on the period and filling factor before and after deposition of the upper silicon oxide layer was experimentally studied. The obtained data are of practical importance for tunable integrated-optical devices based on silicon nitride platform. |
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2100-014X |
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1188 |
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Tiulina, V.; Iomdina, E.; Goltsman, G.; Seliverstov, S.; Sianosyan, A.; Teplyakova, K.; Rusova, A.; Zaitsev, S.; Zernii, E.; Senin, I. |
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UVB promotes the initiation of uveitic inflammatory and changes in thehydration of the cornea in vivo |
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Miscellaneous |
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2019 |
Publication |
FEBS Open Bio |
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FEBS Open Bio |
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9 |
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S1 |
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79 |
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medicine; scheimpflug imaging; UVB; confocal microscopy; cornea; optical coherent tomography; rabbit eyes; terahertz radiation |
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Recently, active research has been conducted in the field of terahertz (THz) scanning of human tissues for noninvasive determination of their hydration level, which haves hown high diagnostic efficiency of this technology in various pathological conditions. Recently, we have developed a laboratory model of the facility for monitoring the state of the water balance of the cornea using THz scanning in vivo, which opens up the possibility of applying this approach in ophthalmology. The aim of the work wasto compare the results of the THz scan of the cornea with its clinical changes using the example of an experimental model of the UV induced keratouveitis. Anexperimental study, which included a comprehensive assessment of clinical changes in the cornea of rabbits during keratouveitis induction, revealed a decrease in the stability of the tear film, pathological changes in the corneal epithelium and stroma, as well as its anatomical and optical parameters. Comparison of data obtained in the THz scan of the cornea with tears production, optical coherence tomography and confocal microscopy showed their consistency in all observation periods, which allows us to conclude that the developed laboratory setup works and the feasibility of further research to promote the corneal hydration evaluation technology in clinical practice. Acknowledgements: Research was funded by the RSF, grant number 161500255. |
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2211-5463 |
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Poster P-01-040 |
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1276 |
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Rasulova, G. K.; Pentin, I. V.; Goltsman, G. N. |
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Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations |
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Journal Article |
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2019 |
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AIP Advances |
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AIP Advances |
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Volume |
9 |
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10 |
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105220 |
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GaAs/AlGaAs superlattice, SL, NbN HEB |
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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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2158-3226 |
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1274 |
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Bandurin, Denis; Svintsov, Dmitry; Gayduchenko, Igor; Xu, Shuigang; Principi, Alessandro; Moskotin, Maksim; Tretyakov, Ivan; Yagodkin, Denis; Zhukov, Sergey; Taniguchi, Takashi; Watanabe, Kenji; Grigorieva, Irina; Polini, Marco; Goltsman, Gregory; Geim, Andre; Fedorov, Georgy |
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Resonant terahertz photoresponse and superlattice plasmons in graphene field-effect transistors |
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2019 |
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APS March Meeting |
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APS March Meeting |
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F14.015 |
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Plasmons, collective oscillations of electron systems, can couple light and electric current, and thus can be used to create compact photodetectors, radiation mixers, and spectrometers. Despite the effort, it has proven challenging to implement plasmonic devices operating at THz frequencies. The material capable to meet this challenge is graphene as it supports long-lived electrically-tunable plasmons. In this talk, we will demonstrate plasmon-assisted resonant detection of THz radiation by antenna-coupled graphene FETs that act as both rectifying elements and plasmonic Fabry-Perot cavities amplifying the photoresponse. We will show that by varying the plasmon velocity using gate voltage, our detectors can be tuned between multiple resonant modes, a functionality that we apply to measure plasmons' wavelength and lifetime in graphene as well as to probe collective modes in its moire minibands. Our approach offers a convenient tool for further plasmonic research that is often difficult under non-ambient conditions and promises a viable route for various THz applications. We acknowledge Leverhulme Trust, Russian Science Foundation Grants N18-72-00234 and 17-72-30036, Russian Foundation for Basic Research No. 18-57-06001 and 16-29-03402. |
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Chandrasekar, R.; Lapin, Z. J.; Nichols, A. S.; Braun, R. M.; Fountain, A. W. |
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Photonic integrated circuits for Department of Defense-relevant chemical and biological sensing applications: state-of-the-art and future outlooks |
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Conference Article |
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2019 |
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Opt. Eng. |
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Opt. Eng. |
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58 |
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02 |
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1 |
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photonic integrated circuits, PIC, optical waveguides, defense applications |
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Photonic integrated circuits (PICs), the optical counterpart of traditional electronic integrated circuits, are paving the way toward truly portable and highly accurate biochemical sensors for Department of Defense (DoD)-relevant applications. We introduce the fundamentals of PIC-based biochemical sensing and describe common PIC sensor architectures developed to-date for single-identification and spectroscopic sensor classes. We discuss DoD investments in PIC research and summarize current challenges. We also provide future research directions likely required to realize widespread application of PIC-based biochemical sensors. These research directions include materials research to optimize sensor components for multiplexed sensing; engineering improvements to enhance the practicality of PIC-based devices for field use; and the use of synthetic biology techniques to design new selective receptors for chemical and biological agents. |
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0091-3286 |
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