Prokhodtsov, A., Golikov, A., An, P., Kovalyuk, V., Goltsman, G., Arakelyan, S., et al. (2019). Effect of silicon oxide coating on a silicon nitride focusing grating coupler efficiency. In EPJ Web Conf. (Vol. 220, 02009).
Abstract: 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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Nikogosyan, A. S., Martirosyan, R. M., Hakhoumian, A. A., Makaryan, A. H., Tadevosyan, V. R., Goltsman, G. N., et al. (2019). Effect of absorption on the efficiency of terahertz radiation generation in the metal waveguide partially filled with nonlinear crystal LiNbO3, DAST or ZnTe. J. Contemp. Phys., 54(1), 97–104.
Abstract: 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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Kitaeva, G. K., Kornienko, V. V., Kuznetsov, K. A., Pentin, I. V., Smirnov, K. V., & Vakhtomin, Y. B. (2019). Direct detection of the idler THz radiation generated by spontaneous parametric down-conversion. Opt. Lett., 44(5), 1198–1201.
Abstract: We study parametric down-conversion (PDC) of optical laser radiation in the strongly frequency non-degenerate regime which is promising for the generation of quantum-correlated pairs of extremely different spectral ranges, the optical and the terahertz (THz) ones. The possibility to detect tenuous THz-frequency photon fluxes generated under low-gain spontaneous PDC is demonstrated using a hot electron bolometer. Then experimental dependences of the THz radiation power on the detection angle and on the pump intensity are analyzed.
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Romanov, N. R., Zolotov, P. I., & Smirnov, K. V. (2019). Development of disordered ultra-thin superconducting vanadium nitride films. In Proc. 8th Int. Conf. Photonics and Information Optics (pp. 425–426).
Abstract: We present the results of development and research of superconducting vanadium nitride VN films ~10 nm thick having different level of disorder. It is showed that both silicon substrate temperature T sub in process of magnetron sputtering and total gas pressure P affect superconducting transition temperature of sputtered films and R 300 /R 20 ratio defining their level of disorder. VN films suitable for development of superconducting single-photon detectors on their basis are obtained.
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Zubkova, E., Golikov, A., An, P., Kovalyuk, V., Korneev, A., Ferrari, S., et al. (2019). CWDM demultiplexer using anti-reflection, contra-directional couplers based on silicon nitride rib waveguide. In J. Phys.: Conf. Ser. (Vol. 1410, 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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