S-c-S junctions as nonlinear elements of microwave receiving devices

Abstract

The analysis of possible phenomena in the superconductor-constriction-superconductor (S-c-S) junctions inserted into microwave circuits is carried out. The results of experiments in which properties of the junctions making them different in comparison with usual nonlinear microwave elements were studied are discussed. The characteristics of receiving devices such as amplifiers, detectors and converters operating on the basis of these phenomena are obtained. The limit characteristics of these devices in different regimes of operation are analysed and compared with experimentally achieved characteristics. It is shown that the noise properties of the receiving devices utilizing the S-c-S junctions close to ideal can be obtained for the frequencies lower than characteristic frequency of the junction. This frequency for known realizations of the S-c-S junctions (point contacts and thin film bridges of small dimensions) can reach of order of 500-1 000 GHz or in other words of the middle of the submillimeter waveband range

Noise and optimization of the dc SQUID

“…We observed that the peaks in Sv corresponding to the noise-free Josephson frequency, f J , and its harmonics become broadened in the presence of thermal noise. As i is reduced, the noi~e broadening increases in a manner that is consistent with the results of Vystavkin et al 34 At frequencies well below f J the power spectrum is white. We take the value of Sv in this region to be the low frequency spectral density S~.…”

Static and dynamic interactions between Josephson junctions

“…The case of a single Josephson weak link coupled to a series resonator has been studied by many groups. For a lowcapacitance weak link, we can summarize the main characteristics of the complex nonlinear interaction between the Josephson junction and the series resonator as follows (Vystavkin et al, 1974;Gubankov et al, 1975;Krech et al, 1979): (i) at resonance the impedance mismatch between the junction and the microwave circuit is reduced by a factor of Q, the loaded quality factor of the cavity; (ii) due to the regenerative interaction between the nonlinear junction and the cavity field the linewidth of the Josephson radiation is narrowed ("self-detection"); (iii) in the dc /-V characteristic a cavity-induced step appears, protruding downwards towards the low-current side of the I-V curve; and (iv) parametric generation of so-called "non-Josephson" radiation is observed at the resonance frequency v res when the junction is biased just below the cavity-induced step, (V) <hv rQS /2e. This radiation is emitted simultaneously with the Josephson radiation at the frequency Vj = 2e ( V) /h.…”

Thermal Fluctuations in Resonant Motion of Fluxons on a Josephson Transmission Line: Theory and Experiment

“…The result resembles published expressions for small tunnel junctions 4 and point contacts and microbridges. 5 The quantum phase difference cp{x,t) between the two superconductors of the Josephson junction is governed by the perturbed sine-Gordon equation 6 Vxx-Vtt-sintP^V+atPt+n&'t)'…”