|Ph.D Student||Abdo Baleegh|
|Subject||Nonlinear Dynamics in Superconducting Stripline Resonators|
and Interference Devices
|Department||Department of Electrical Engineering||Supervisor||Professor Eyal Buks|
|Full Thesis text|
We study superconducting stripline resonators coupled to nonlinear elements (weak-links, microbridges and dc-SQUIDs) with emphasis on the resultant nonlinear behavior and nonlinear dynamics.
In the first part of the research, we study a variety of strong nonlinear effects observed in NbN superconducting stripline resonators at relatively low input powers. Namely, sudden and abrupt jumps in the resonance curves, frequency and power hysteresis, resonance frequency shift and self-sustained modulation. To account for these unique effects we consider a theoretical model in which local heating of weak links and thermal instability are responsible for these effects and we show that such model yields a good agreement with the experiments. Moreover, we apply this theoretical model of thermal instability in order to calculate and measure experimentally the noise-activated escape rate of metastable states of the system.
Furthermore, we utilize these strong nonlinearities in order to demonstrate two novel amplification schemes in superconducting resonators, the first is what is known as intermodulation amplification, where a small amplitude coherent signal is generated and amplified due to frequency mixing with an intense drive in the vicinity of an instability, while the second is the so called stochastic resonance phenomenon, where a weak modulating signal is amplified in the vicinity of a metastable state via coherent interaction with a certain amount of white noise.
While, in the second part of the research, we study unique nonlinear effects observed in superconducting stripline resonators integrated with dc-SQUIDs, such as intermodulation and parametric amplification, phase-sensitive modulation, and noise-induced spikes in the time domain. To account for the temporal response of the system we solve numerically the equations of motion for the integrated system, and present theoretical simulations which exhibit a good agreement with the experimental data.