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Tretyakov I, Shurakov A, Perepelitsa A, Kaurova N, Svyatodukh S, Zilberley T, et al. Silicon room temperature IR detectors coated with Ag2S quantum dots. In: Proc. IWQO.; 2019. p. 369–71.
Abstract: For decades silicon has been the chief technological semiconducting material of modern microelectronics. Application of silicon detectors in optoelectronic devices are limited to the visible and near infrared ranges, due to their transparency for radiation with a wavelength higher than 1.1 μm. The expansion Si absorption towards longer wave lengths is a considerable interest to optoelectronic applications. In this work we present an elegant and effective solution to this problem using Ag2S quantum dots, creating impurity states in Si to cause sub-band gap photon absorption. The sensitivity of room temperature zero-bias Si_Ag2S detectors, which we obtained is 1011 cmHzW . Given the variety of QDs parameters such as: material, dimensions, our results open a path towards the future study and development of Si detectors for technological applications.
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Tretyakov I, Maslennikov S, Semenov A, Safir O, Finkel M, Ryabchun S, et al. Impact of operating conditions on noise and gain bandwidth of NbN HEB mixers. In: Proc. 26th Int. Symp. Space Terahertz Technol.; 2015. 39.
Abstract: Hot-electron bolometer mixers (HEB’s) are the most promising devices as mixing element for terahertz spectroscopy and astronomy at frequencies beyond 1.4 THz. They have a low noise temperature and low demands on local oscillator (LO) power. 1,2 An important limitation is the IF bandwidth, of the order of a few GHz, and which in principle depends on energy relaxation due to electron- phonon processes and on diffusion-cooling. It has been proposed by Prober that a reduction in length of the HEB would lead to an increased bandwidth. 3 This appeared to be achieved by Tretyakov et al by measuring the gain bandwidth close to the critical temperature of the NbN. 2 Unfortunately, the noise bandwidth of similar devices operated at temperatures around 4.2 K appear not depend on the length. The fundamental problem to be addressed is the position-dependent superconducting state of the HEB- devices under operating conditions, which determines the conditions for the cooling of the hot quasiparticles. Some progress has been made by Barends et al in a semi-empirical model to describe the I,V curves under operating conditions at a bath temperature around 4.2 K. 4 In more recent work Vercruyssen et al have analyzed the I,V curve, without any LO-equivalent bias, of a model NSN system. 5 This work suggests that the most appropriate model for an HEB under operating conditions is that of a potential-well in the superconducting gap in the center of the NbN, analogous the bimodal superconducting state described by Vercruyssen et al. Hot quasiparticles in the well can not diffuse out and can only cool by electron-phonon processes, those with higher energies than the heights of the walls of the well can diffuse out. Using this working hypothesis we have carried out experiments on a sub-micrometer NbN bridge connected to a gold (Au) planar spiral antenna. An in situ process is used to deposit Au on NbN. The Au is removed in the center to define the uncovered NbN, which will act as the superconducting mixer itself. The antenna is deposited on the remaining Au layer on the NbN. The Au contacts suppress the energy gap of the NbN film located underneath the gold layer 7,8 . The measured resistive transition is shown in Fig.1. It clearly shows a T c of the bilayer at 6.2 K and the resistive transition of the NbN itself around 9 K. In addition we show the measured noise bandwidth (red squares) for different bath temperatures. Clearly the noise bandwidth increases strongly by increasing the bath temperature from 5 K to 8 K, up to 13 GHz. We interpret this pattern as evidence for improved out-diffusion of hot electrons due to normal banks and a shallow superconducting potential well compared to k B T. As expected the noise temperature in this regime is much bigger than when biased at 4.2 K. R EFERENCES 1 W. Zhang, P. Khosropanah, J. R. Gao, E. L. Kollberg, K. S. Yngvesson, T. Bansal, R. Barends, and T. M. Klapwijk Appl. Phys. Lett. 96, 111113, (2010). 2 Ivan Tretyakov, Sergey Ryabchun, Matvey Finkel, Anna Maslennikova, Natalia Kaurova, Anastasia Lobastova, Boris Voronov, and Gregory Gol’tsman Appl. Phys. Lett. 98, 033507 (2011). 3 D. E. Prober, Appl. Phys. Lett. 62, 2119 (1992). 4 R. Barends, M. Hajenius, J. R. Gao, and T. M. Klapwijk, Appl. Phys. Lett. 87, 263506 (2005). 5 N. Vercruyssen, T. G. A. Verhagen, M. G. Flokstra, J. P. Pekola, and T. M. Klapwijk Physical Review B 85, 224503 (2012).
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Baeva EM, Titova NA, Veyrat L, Sacépé B, Semenov AV, Goltsman GN, et al. Thermal relaxation in metal films bottlenecked by diffuson lattice excitations of amorphous substrates [Internet].; 2021 [cited 2024 Jul 8].arXiv:2101.07071v1 [cond-mat.mtrl-sci]. Available from: https://arxiv.org/abs/2101.07071v1
Abstract: Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature Te of the films as a function of Joule power per unit of area P2D. In all samples, we observe the dependence P2D∝Tne with the exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear T-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
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Titova NA, Baeva EM, Kardakova AI, Goltsman GN. Fabrication of NbN/SiNx:H/SiO2 membrane structures for study of heat conduction at low temperatures. In: J. Phys.: Conf. Ser. Vol 1695.; 2020. 012190.
Abstract: Here we report on the development of NbN/SiNx:H/SiO2-membrane structures for investigation of the thermal transport at low temperatures. Thin NbN films are known to be in the regime of a strong electron-phonon coupling, and one can assume that the phononic and electronic baths in the NbN are in local equilibrium. In such case, the cooling of the NbN-based devices strongly depends on acoustic matching to the substrate and substrate thermal characteristics. For the insulating membrane much thicker than the NbN film, our preliminary results demonstrate that the membrane serves as an additional channel for the thermal relaxation of the NbN sample. That implies a negligible role of thermal boundary resistance of the NbN-SiNx:H interface in comparison with the internal thermal resistance of the insulating membrane.
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Komrakova S, Kovalyuk V, An P, Golikov A, Rybin M, Obraztsova E, et al. Effective absorption coefficient of a graphene atop of silicon nitride nanophotonic circuit. In: J. Phys.: Conf. Ser. Vol 1695.; 2020. 012135.
Abstract: In this paper, we demonstrate the results of a study of the optical absorption properties of graphene integrated with silicon nitride O-ring resonator. We fabricated an array of O-ring resonators with different graphene coverage area atop. By measuring the transmission spectra of nanophotonic devices with and without graphene, we calculated the effective absorption coefficient of the graphene on a rib silicon nitride waveguide.
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Prokhodtsov A, Kovalyuk V, An P, Golikov A, Shakhovoy R, Sharoglazova V, et al. Silicon nitride Mach-Zehnder interferometer for on-chip quantum random number generation. In: J. Phys.: Conf. Ser. Vol 1695.; 2020. 012118.
Abstract: In this work, we experimentally studied silicon nitride Mach-Zehnder interferometer (MZI) with two directional couplers and 400 ps optical delay line for telecom wavelength 1550 nm. We achieved the extinction ratio in a range of 0.76-13.86 dB and system coupling losses of 28-44 dB, depending on the parameters of directional couplers. The developed interferometer is promising for the use in a compact random number generator for the needs of a fully integrated quantum cryptography system, where compact design, as well as high generation speed, are needed.
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Venediktov IO, Elezov MS, Prokhodtsov AI, Kovalyuk VV, An PP, Golikov AD, et al. Study of microheater’s phase modulation for on-chip Kennedy receiver. In: J. Phys.: Conf. Ser. Vol 1695.; 2020. 012117.
Abstract: In this work we describe phase modulators for several Mach-Zehnder interferometers (MZI) on silicon nitride platform for telecomm wavelength (1550 nm). We obtained current-voltage and phase-voltage curves for these modulators. MZI are needed for experimental realisation of various quantum receivers that can distinguish weak coherent states of light with extremely low error. Thermo-optical (TO) modulation is ensured by microheaters on one of the arms of MZI, which enables the change of the refractive index of the material with temperature. This approach allows to apply the necessary voltage to the golden microheaters to obtain the required phase change. For the on-chip microheaters we demonstrate the dependence of the phase shift on the voltage applied to our on-chip microheaters.
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Elmanov I, Sardi F, Xia K, Kornher T, Kovalyuk V, Prokhodtsov A, et al. Development of focusing grating couplers for lithium niobate on insulator platform. In: J. Phys.: Conf. Ser. Vol 1695.; 2020. 012127.
Abstract: In this paper, we fabricate and experimentally study focusing grating couplers for lithium niobate on an insulator photonic platform. The transmittance of a waveguide equipped with in- and out-couplers with respect to the grating period is measured with and without silicon dioxide cladding applied. Our results show the influence of silicon dioxide cladding on the efficiency and the central wavelength of grating couplers and can be used to improve grating coupling efficiency. Our study is supported by numerical simulations.
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Komrakova S, Javadzade J, Vorobyov V, Bolshedvorskii S, Soshenko V, Akimov A, et al. CMOS compatible nanoantenna-nanodiamond integration. In: J. Phys.: Conf. Ser. Vol 1410.; 2019. 012180.
Abstract: Here we demonstrate CMOS compatible method to deterministically produce nanoantenna with nanodiamonds systems on example of bull-eye antenna on top of on hyperbolic metamaterials. We study the statistics of the placement of nanodiamonds and measure the fluorescence lifetime and the second-order correlation function of NV-centers inside nanodiamonds.
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Zubkova E, Golikov A, An P, Kovalyuk V, Korneev A, Ferrari S, et al. CWDM demultiplexer using anti-reflection, contra-directional couplers based on silicon nitride rib waveguide. In: J. Phys.: Conf. Ser. Vol 1410.; 2019. 012179.
Abstract: We report on the development and fabrication of a 9-channel coarse wavelength-division multiplexing for telecommunication wavelengths (1550 nm) using anti-reflection contra-directional couplers, based on silicon nitride (Si3N4) rib waveguide. The transmitted and reflected spectrum in each channel of the demultiplexer were measured. The average full width at half maximum of the transmitted (reflected) spectra is about 3 nm.
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