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Kovalyuk, V., Ferrari, S., Kahl, O., Semenov, A., Lobanov, Y., Shcherbatenko, M., et al. (2017). Waveguide integrated superconducting single-photon detector for on-chip quantum and spectral photonic application. In J. Phys.: Conf. Ser. (Vol. 917, 062032).
Abstract: With use of the travelling-wave geometry approach, integrated superconductor- nanophotonic devices based on silicon nitride nanophotonic waveguide with a superconducting NbN-nanowire suited on top of the waveguide were fabricated. NbN-nanowire was operated as a single-photon counting detector with up to 92 % on-chip detection efficiency in the coherent mode, serving as a highly sensitive IR heterodyne mixer with spectral resolution (f/df) greater than 106 in C-band at 1550 nm wavelength
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Zubkova, E., An, P., Kovalyuk, V., Korneev, A., Ferrari, S., Pernice, W., et al. (2017). Integrated Bragg waveguides as an efficient optical notch filter on silicon nitride platform. In J. Phys.: Conf. Ser. (Vol. 917, 062042).
Abstract: We modeled and fabricated integrated optical Bragg waveguides on a silicon nitride (Si3N4) platform. These waveguides would serve as efficient notch-filters with the desired characteristics. Transmission spectra of the fabricated integrated notch filters have been measured and attenuation at the desired wavelength of 1550 nm down to -43 dB was observed. Performance of the filters has been studied depending on different parameters, such as pitch, filling factor, and height of teeth of the Bragg grating
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Chuprina, I. N., An, P. P., Zubkova, E. G., Kovalyuk, V. V., Kalachev, A. A., & Gol'tsman, G. N. (2017). Optimisation of spontaneous four-wave mixing in a ring microcavity. In J. Phys.: Conf. Ser. (Vol. 47, pp. 887–891).
Abstract: Abstract. A theory of spontaneous four-wave mixing in a ring microcavity is developed. The rate of emission of biphotons for pulsed and monochromatic pumping with allowance for the disper- sion of group velocities is analytically calculated. In the first case, pulses in the form of an increasing exponential are considered, which are optimal for excitation of an individual resonator mode. The behaviour of the group velocity dispersion as a function of the width and height of the waveguide is studied for a specific case of a ring microcavity made of silicon nitride. The results of the numeri- cal calculation are in good agreement with the experimental data. The ring microcavity is made of two types of waveguides: com- pletely etched and half etched. It is found that the latter allow for better control over the parameters in the manufacturing process, making them more predictable.
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Zolotov, P. I., Divochiy, A. V., Vakhtomin, Y. B., Morozov, P. V., Seleznev, V. A., & Smirnov, K. V. (2017). Development of high-effective superconducting single-photon detectors aimed for mid-IR spectrum range. In J. Phys.: Conf. Ser. (Vol. 917, 062037).
Abstract: We report on development of superconducting single-photon detectors (SSPD) with high intrinsic quantum efficiency in the wavelength range 1.31 – 3.3 μm. By optimization of the NbN film thickness and its compound, we managed to improve detection efficiency of the detectors in the range up to 3.3 μm. Optimized devices showed intrinsic quantum efficiencies as high as 10% at mid-IR range.
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Ferrari, S., Kovalyuk, V., Hartmann, W., Vetter, A., Kahl, O., Lee, C., et al. (2017). Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors. Opt. Express, 25(8), 8739–8750.
Abstract: We investigate how the bias current affects the hot-spot relaxation dynamics in niobium nitride. We use for this purpose a near-infrared pump-probe technique on a waveguide-integrated superconducting nanowire single-photon detector driven in the two-photon regime. We observe a strong increase in the picosecond relaxation time for higher bias currents. A minimum relaxation time of (22 +/- 1)ps is obtained when applying a bias current of 50% of the switching current at 1.7 K bath temperature. We also propose a practical approach to accurately estimate the photon detection regimes based on the reconstruction of the measured detector tomography at different bias currents and for different illumination conditions.
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