Non-Thermal Absorption and Quantum Efficiency of SINIS Bolometer

We study mechanisms of absorption in two essentially different types of superconductor-insulator-normal metal-insulator-superconductor (SINIS) bolometers with absorber directly placed on Si wafer and with absorber suspended above the substrate. The figure of merit for quantum photon absorption is quantum efficiency equal to the number of detected electrons for one photon. The efficiency of absorption is dramatically dependent on phonon losses to substrate and electrodes, and electron energy losses to electrodes through tunnel junctions. The maximum quantum efficiency can approach n = hf/kT = 160 at f = 350 GHz T = 0.1 K, and current responsivity dI/dP = e/kT in quantum gain bolometer case, contrary to photon counter mode with quantum efficiency of n = 1 and responsivity dI/dP = e/hf. In experiments, we approach intrinsic quantum efficiency up to n = 80 electrons per photon in bolometer with suspended absorber, contrary to quantum efficiency of about one for absorber on the substrate. In the case of suspended Cu and Pd absorber, Kapitsa resistance protect from power leak to Al electrodes

Superconducting Receivers for Space, Balloon, and Ground-Based Sub-Terahertz Radio Telescopes

We give a review of both our own original scientific results of the development of superconducting receivers for sub-terahertz astronomy and the main leading concepts of the global instrumentation. The analysis of current astronomical problems, the results of microwave astroclimate research, and the development of equipment for sub-terahertz radio astronomy studies justify the need and feasibility of a major infrastructure project in Russia to create a sub-terahertz telescope, as well as to enhance the implementation of the ongoing Millimetron and Suffa projects. The following results are discussed: i) superconducting coherent receivers and broadband subterahertz detectors for space, balloon, and ground-based radio telescopes have been developed and tested; ii) ultrasensitive receiving systems based on tunnel structures such as superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal metal-insulator-superconductor (SINIS) have been created, fabricated, and examined; iii) a receiving array based on SINIS detectors and microwave readout system for such structures has been implemented; iv) methods for manufacturing high-quality tunnel structures Nb/AlOx/Nb and Nb/AlN/NbN based on niobium films with a current density of up to 30 kA/cm(2) have been developed. Receivers operated at 200 to 950 GHz and having a noise temperature only a factor of 2 to 5 higher than the quantum limit have been created and tested

Активность калликреин-кининовой и ренин-ангиотензиновой систем крови новорожденных с гипоксически-ишемической энцефалопатией

Oxygen insufficiency in newborns is associated with disturbed vascular tone, which are regulated by kallikrein-kinin (KKS) and renin-angiotensin systems (RAS).Important index of hemodynamic disturbances is the activity of kallikrein, of angiotensin-converting enzyme (ACE) and also inhibitors of proteinases: α1-proteinase inhibitor and α2-macroglobulin. In hypoxic-ischemic encephalopathy of mature newborns and children of the I, II premature degrees , blood KKS activity is increased in comparison with RAS. Decreased activity of α1-proteinase inhibitor is seen in 46% of premature infants of II degree which usually leads to chronic pathologic process. The increased activity of ACE is important for preventing hemodynamic disturbances.Кислородная недостаточность у новорожденных сопровождается нарушением тонуса сосудов, в регуляции которого принимают участие калликреин-кининовая (ККС) и ренин-ангиотензиновая системы (РАС). Важным показателем гемодинамических нарушений является активность калликреина, ангиотензинпревращающего фермента (АПФ), а также ингибиторов протеиназ - α1-протеиназного ингибитора (α1-ПИ) и α2-макроглобулина. При гипоксически-ишемической энцефалопатии доношенных и детей I, II степени недоношенности установлена более выраженная активация ККС крови по сравнению с РАС. Снижение активности α1-ПИ наблюдается у 46% новорожденных II степени недоношенности, что, как правило, приводит к хронизации патологического процесса. Для прогноза нарушений гемодинамики имеет значение повышенная активность АПФ. Экономическая оценка проводилась для оптимизации морфологических исследований в работе отдела сердечно-сосудистой хирургии НИИ кардиологии ТНЦ СО РАМН (г. Томск). Необходимость анализа степени дисфункции миокарда обусловливается выбором оптимальной тактики хирургического лечения больных ишемической кардиомиопатией или выявления противопоказаний к таковому

Arrays of sub‐terahertz cryogenic metamaterial

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

Observation of Photon Noise by a Parallel-Series Array of Cold-Electron Bolometers

The quasioptical qualification of cold-electron bolometers (CEB) operated in the cross-slot antenna at 350GHz, are presented. The photon noise observation by a parallel/series array of CEBs is demonstrated for power loads of the order of 1 pW. The experimental results have been fitted to theoretical model with two heat-balance equations for the absorber and for superconducting electrodes. The measured noise has been decomposed into several terms with the help of theory. It is demonstrated that the photon noise exceeds any other noise components at some voltage range, that allows us to conclude that the bolometers see the photon noise. A shape of the noise dependence on the bolometer voltage originates from the photonic component according to the theory. In the additional experiment on heating of the sample holder the photonic component is almost absent and the total noise is lower, proving the presence of the photon noise in the first experiment