182 research outputs found
Stochastic Resonance with a Single Metastable State
We study thermal instability in NbN superconducting stripline resonators. The
system exhibits extreme nonlinearity near a bifurcation, which separates a
monostable zone and an astable one. The lifetime of the metastable state, which
is locally stable in the monostable zone, is measure near the bifurcation and
the results are compared with a theory. Near bifurcation, where the lifetime
becomes relatively short, the system exhibits strong amplification of a weak
input modulation signal. We find that the frequency bandwidth of this
amplification mechanism is limited by the rate of thermal relaxation. When the
frequency of the input modulation signal becomes comparable or larger than this
rate the response of the system exhibits sub-harmonics of various orders
Observation of Bifurcations and Hysteresis in Nonlinear NbN Superconducting Microwave Resonators
In this paper we report some extraordinary nonlinear dynamics measured in the
resonance curve of NbN superconducting stripline microwave resonators. Among
the nonlinearities observed: aburpt bifurcations in the resonance response at
relatively low input powers, asymmetric resonances, multiple jumps within the
resonance band, resonance frequency drift, frequency hysteresis, hysteresis
loops changing direction and critical coupling phenomenon. Weak links in the
NbN grain structure are hypothesized as the source of the nonlinearities.Comment: This work has been submitted to the IEEE for possible publicatio
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