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3 results on '"Fedor V Khan"'

1. Superconducting Sub-Terahertz Oscillator with Continuous Frequency Tuning

Author

Maxim E. Paramonov, Lyudmila V. Filippenko, Fedor V. Khan, Oleg S. Kiselev, and Valery P. Koshelets

Subjects
superconducting local oscillator, long Josephson junction, superconducting integrated receiver, high-quality tunnel junctions, sub-terahertz frequency range, continuous frequency tuning, Technology, Engineering (General). Civil engineering (General), TA1-2040, Biology (General), QH301-705.5, Physics, QC1-999, Chemistry, QD1-999
Abstract

The development and approbation of a superconducting local oscillator based on a long Josephson junction made it possible to create a fully superconducting integrated receiver in sub-terahertz frequency range, which was successfully tested both on board a high-altitude balloon and in the laboratory. In order to expand the frequency range of a superconducting integrated local oscillator, it is necessary to ensure the continuous tuning of its frequency at an arbitrary bias current, including a so-called resonant mode regime. The resonant mode regime takes place for high-quality tunnel junctions with low leakage; in this regime, stable generation is possible only at Fiske steps, the distance in frequency between which is tens of GHz. A method for suppressing resonances has been proposed and implemented; this method is based on the introduction of normal metal layers into the region near the long Josephson junction. Modeling of the propagation of electromagnetic waves in the proposed integrated structure was carried out; experimental samples were fabricated, and their comprehensive study was performed. The complete suppression of resonances and the possibility of the continuous tuning of the frequency of a superconducting local oscillator in the range of 200–700 GHz have been demonstrated. The linewidth of the FFO radiation does not exceed 15 MHz over the entire frequency range, which makes it possible to implement the phase locked loop mode in an integrated receiver intended for spectral studies.

Published
2022
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2. Shunted Josephson Junctions and Optimization of Niobium Integrated Matching Circuits

Author

Artem Chekushkin, Artemiy A. Atepalikhin, Lyudmila V. Filippenko, Mariia S. Shevchenko, Fedor V Khan, and Valery P. Koshelets

Subjects
Josephson effect, Materials science, business.industry, Terahertz radiation, Detector, Integrated circuit, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, law.invention, law, Condensed Matter::Superconductivity, Parasitic element, Optoelectronics, Electrical and Electronic Engineering, business, Microwave, Voltage, Electronic circuit
Abstract

Josephson junctions (JJs) with non-hysteretic I-V characteristic and high critical parameters are required for many applications; in particular, they are needed to create tunable THz range oscillators. We fabricated and studied shunted superconductor-insulator-superconductor (SIS) Nb-AlOx-Nb tunnel junctions with an area of about 1m2, estimated their parameters, and compared them with theoretical models. To assess the performance of shunted junctions in the terahertz range, their characteristics were studied under the influence of a high-frequency signal; the estimated value of the characteristic voltage for the shunted junction at a high frequency is about 1 mV. To improve the circuit parameters, a new type of the shunting based on application of NIS junctions was proposed, which reduces the influence of parasitic inductance, expands the frequency range of the generator, and decreases the size of the structure. The JJs with a new type of shunting have been fabricated and studied. The niobium integrated circuits intended for matching the superconducting oscillator and an SIS junction as a microwave detector were designed, fabricated, and tested. Such structures are required for studying the spectral characteristics and analyzing the operation of the oscillator. The developed circuits have demonstrated efficient operation at frequencies from 300 to 700 GHz; the experimental results are in good agreement with the simulated characteristics. The results obtained will be implemented for further development of the THz range oscillators.

Published
2022

3. Dispersive Fourier Transform Spectrometer for Characterizing superconducting NbTiN films at THz frequencies

Author

Pavel N. Dmitriev, K. I. Rudakov, Bram N.R. Lap, A. Khudchenko, Fedor V Khan, Andrey M. Baryshev, Ronald Hesper, and Valery P. Koshelets

Subjects
Superconductivity, Materials science, Physics::Instrumentation and Detectors, business.industry, Terahertz radiation, Detector, Fourier transform spectrometers, Physics::Optics, Fourier transform spectroscopy, Optics, Condensed Matter::Superconductivity, Thin film, Reflection coefficient, business
Abstract

A Terahertz Dispersive Fourier Transform Spectrometer was used to study the RF properties of superconducting films used for THz detectors. The experimental results were fitted using an extended Mattis-Bardeen theory and show a good agreement.

Published
2021

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