Mixers based on superconductor–insulator–superconductor (SIS) tunnel junctions are the best input devices at frequencies from 0.1 to 1.2 THz. This is explained by both the extremely high nonlinearity of such elements and their extremely low intrinsic noise. Submicron tunnel junctions are necessary to realize the ultimate parameters of SIS receivers, which are used as standard devices on both ground and space radio telescopes around the world. The technology for manufacturing submicron Nb–AlN–NbN tunnel junctions using electron-beam lithography was developed and optimized. This article presents the results on the selection of the exposure dose, development time, and plasma chemical etching parameters to obtain high-quality junctions (the ratio of the resistances below and above the gap R_j/R_n). The use of a negative-resist ma-N 2400 with lower sensitivity and better contrast in comparison with a negative-resist UVN 2300-0.5 improved the reproducibility of the structure fabrication process. Submicron (area from 2.0 to 0.2 µm²) Nb–AlN–NbN tunnel junctions with high current densities and quality parameters R_j/R_n > 15 were fabricated. The spread of parameters of submicron tunnel structures across the substrate and the reproducibility of the cycle-to-cycle process of tunnel structure fabrication were measured.

For improving the dynamic range and sensitivity at high power load we have integrated Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) bolometers with a Frequency Selective Surface (FSS) based distributed absorber formed by a series and parallel array consisting of 25 annular antenna elements, each containing two SINIS bolometers. By using a design with 50 bolometers we reduce incident power load on each bolometer, increase sensitivity and saturation power which is important for ground-based and balloon-borne telescopes with high background power loads. Our main detector pixel is optimized for a frequency band centered at 345 GHz. The detectors are matched to incoming telescope beam by a back-to-back horn with a back reflector. Such a configuration improves both the efficiency and the bandwidth of the receiver. Measured voltage responsivity approaches 2*109 V/W with an amplifier-limited voltage noise of 20 nV/Hz1/2, which corresponds to a NEP=10-17 W/Hz1/2. The linear voltage response for incoming power is observed for absorbed power of about 5 pW. The current responsivity for parallel array is 2*104 A/W and the shot noise limited intrinsic noise equivalent power is NEP=5*10-18 W/Hz1/2. The noise equivalent temperature difference is NETD=100 μK/Hz1/2 at 2.7 K background radiation temperature.

This review presents the main characteristics and mechanisms of operation of superconductor–insulator–normal metal–insulator–superconductor (SINIS) microwave detectors. An analysis of the detectors’ performance against a quantum detector and a photon counter is given. Methods for cooling a superconductor using normal metal traps and the role of electron cooling in optimizing the current response to terahertz radiation are discussed. Fabrication methods using shadow evaporation as well as magnetron sputtering are described.

The study of the origin and transport of water in the universe is an important part of the scientific program of the Millimetron space observatory. This will be made possible by observations conducted in single-dish mode using an onboard instrument - the High Resolution Spectrometer (HRS). This instrument incorporates heterodyne array receivers operating within the range $0.5 -2.7$ THz, comprising 3-pixel arrays of superconductor-insulator-superconductor (SIS) mixers operating at frequencies below 1.3 THz and 7-pixel matrix receivers based on NbN HEB mixers observing above 1.3 THz. This paper presents the current status of development for a mixers planned for use in the HRS instrument of the Millimetron space observatory.

—Arrays of planar annular antennas in the 345 GHz range with integrated superconductor–insulator–normal metal–insulator–superconductor (SINIS) bolometers have been developed, fabricated, and experimentally investigated. To increase the absorption efficiency, the source signal was matched with the array using a back-to-back horn and a counter-reflector. The efficiency of the receiving structure was studied depending on the direction of irradiation—through the substrate and from the antenna—as well as on the thickness of the substrate. The methods for normalizing a received signal using a reference channel outside and inside a cryostat is described. The best results were obtained by irradiating the array from the antenna with a substrate thickness equivalent to a quarter wavelength in the dielectric and sputtering of the rear side with a gold film (counterreflector). The effective matching band in the main range was more than 50 GHz; the volt–watt sensitivity reaches 10⁹ V/W.

Integrated quasi-optical cryogenic terahertz receivers contain arrays of detectors, quasi-optical filters, interferometers, and other metamaterials. Matrices of quasi-optical band-pass, low-pass, and high-pass filters, Fabry–Perot grid interferometers, and arrays of half-wave and electrically small antennas with superconductor-insulator-normal metal-insulator-superconductor (SINIS) sub-terahertz wavelength range detectors were fabricated and experimentally studied on the same computational, technological, and experimental platform. For the design of the filters, we used the periodic frequency-selective surfaces (FSS) approach, contrary to detector arrays that can be presented in a model of distributed absorbers. The structures were fabricated using direct electron beam lithography, thermal shadow evaporation, lift-off, alternatively magnetron sputtering, and chemical and plasma etching. The numerical simulation methods of such structures are sufficiently different: for the reactive matrices with low losses, the approximation of an infinite structure with periodic boundary conditions is applicable, and for the arrays of detectors with dissipative elements of absorbers, a complete analysis of the finite structure with hundreds of interacting ports is applicable. The difference is determined by the presence of dissipation in the detector arrays, the phase of the reflected or re-emitted signal turned out to be undefined and the Floquet periodic boundary conditions are correct only for a phased array antenna. The spectral characteristics of the created filters, interferometers, and antenna arrays were measured in the frequency range 50–600 GHz.