The amplitudes of the first Shapiro steps for an external signal with frequencies of 72 and 265 GHz are measured as function of the temperature from 20 to 80 K for a 6 μm Josephson grain boundary ...junction fabricated by YBaCuO film deposition on an yttria-stabilized zirconia bicrystal substrate. Non-monotonic dependences of step heights for different external signal frequencies were found in the limit of a weak driving signal, with the maxima occurring at different points as function of the temperature. The step heights are in agreement with the calculations based on the resistively-capacitively shunted junction model and Bessel theory. The emergence of the receiving optima is explained by the mutual influence of the varying critical current and the characteristic frequency.
We consider properties of dichroic antenna arrays on a silicon substrate with integrated cold-electron bolometers to detect radiation at frequencies of 210 and 240 GHz. This frequency range is widely ...used in cosmic microwave background experiments in space, balloon, and ground-based missions such as BICEP Array, LSPE, LiteBIRD, QUBIC, Simons Observatory, and AliCPT. As a direct radiation detector, we use cold-electron bolometers, which have high sensitivity and a wide operating frequency range, as well as immunity to spurious cosmic rays. Their other advantages are the compact size of the order of a few micrometers and the effect of direct electron cooling, which can improve sensitivity in typical closed-loop cycle
He cryostats for space applications. We study a novel concept of cold-electron bolometers with two SIN tunnel junctions and one SN contact. The amplitude-frequency characteristics measured with YBCO Josephson Junction oscillators show narrow peaks at 205 GHz for the 210 GHz array and at 225 GHz for the 240 GHz array; the separation of these two frequency bands is clearly visible. The noise equivalent power level at an operating point in the current bias mode is 5 × 10
W/√Hz.
The resonant properties of Cold-Electron Bolometers (CEBs) located at a 0.3 K cryostat plate are measured using a 50 μm long high-temperature YBa2Cu3O7−δ (YBCO) Josephson junction oscillator, placed ...on a 2.7 K plate of the same cryostat. For these purposes, a bunch of YBCO Josephson oscillators with various lengths of dipole antennas and overlapping generation bands has been developed and investigated in 50–500 GHz frequency range. Two setups of Josephson junction placement were compared, and as a result, various narrow-band receiving systems with CEBs have been measured, demonstrating the feasibility of the presented approach.
We have studied photoconductivity under the action of strong laser terahertz pulses in optimally doped and underdoped films of the high-T c superconductor YBa 2 Cu 3 O 7- δ in the vicinity of the ...critical temperature. In the optimally doped film, the negative photoconductivity with delayed signal increment and decay has been observed. In the underdoped film, a fast positive photoresponse has been detected on top of the negative photoconductivity background at temperatures above the transition temperature. Possible mechanisms responsible for the effects observed are discussed.
YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCo) thin films on R-plane sapphire up to 5-cm-diam with ZrO/sub 2/:Y (YSZ) buffer layers were fabricated by in-situ off-axis DC magnetron sputtering-and ...laser ablation. The film DC properties, critical current density (J/sub c/), effective microwave surface resistance (R/sub s/), X-ray data and surface morphology as functions of deposition temperature (T/sub d/) from 600 to 750/spl deg/C were studied. We have found out that the two processes simultaneously and in different ways affect the YBCO layers superconducting properties versus T/sub d/. The results show that films deposited at both ends of T/sub d/ range have equal critical temperatures but their J/sub c/ and R/sub s/ differ up to an order of magnitude. High-homogeneity 5-cm-diam films with J/sub c/>4 MA/cm/sup 2/ and R/sub s/<0.8, m/spl Omega/ at 10 GHz, and 77 K were routinely fabricated under optimum growth conditions. The effective 2 GHz short-dipole antenna and Wilkinson divider were developed and fabricated from the films.< >
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