Stimulated Emission and Amplification in Josephson Junction Arrays

Phase-locking of disordered two-dimensional Josephson junction arrays to microwave radiation

“…The authors ascribed the e®ect to a \laser type" behavior of superradiant arrays. Also in the experiment of Barbara et al [13] it has been found evidence of threshold e®ects.…”

“…If con¯rmed by further experimental work this can be an important information for the design of optimal array based oscillators. We note that in the experiment performed by Barbara et al [13] arrays are precisely of the type N & M .…”

“…We want to propose a mechanism that can lead to the appearance of a threshold and is connected with the number of activated oscillators. For the underdamped junctions experiment [13] an explanation in terms of detuning between the natural frequencies of the oscillators and the cavity has been proposed [19], underlying that it is possible that the strong interaction between the cavity and the oscillators is responsible for the sudden increase of the number of phase-locked oscillators once a critical number of oscillators is activated. In the system under consideration the analysis is greatly simpli¯ed by the fact that the dynamics of the forcing term (the rf¯eld) is independent of the dynamics of the oscillators.…”

“…If our analysis is correct the average fraction of the phase locked rows for a given rf power should be proportional to the di®erence of cumulative Gaussian distribution (error integral), so the predictions of Eq.s (13,15) have been checked simulating Eq.s (2-6) using an explicit scheme similar to that used in [17]. .3c).…”

“…We want to emphasize that also other studies indicate the relevance of the row decomposition. For instance in a recent experiment [13] it has shown that individual rows seem capable to phase-lock, so that the whole system is better described in terms of oscillators constituted by rows than by considering the individual junctions as elementary oscillators. Also in theoretical investigations, such as those of Barahona and Watanabe [14], the motion of°uxons across the arrays, in absence of microwave excitations, has been handled starting from the dynamics of the elementary rows.…”