Arrays of sub‐terahertz cryogenic metamaterial

Review article, 2021

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 bSeam 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.