Nonlinear microwave and millimeter wave phenomena in high-temperature superconducting devices.

摘要

Nonlinear inductance effects in high temperature superconductors (HTS) have been investigated at both microwave and millimeter wave frequencies. These effects can be characterized as temperature dependent effects such as the kinetic inductance, and device dependent effects such as Josephson junctions incorporated in parametric amplifiers. We have designed, measured, modeled, and analyzed structures that exhibit these effects so as to better understand and provide quantifiable design criteria for the development of such devices as narrowband filters, resonators, delay lines and parametric amplifiers. We examined coplanar waveguide resonators at 5 GHz in order to model the nonlinear kinetic inductance effect. With measured Q's of 16,000 we were able to model the devices behavior with a "T squared" dependence which is drastically different than the usual Gorter-Casimir dependence. Using this model we designed a coplanar waveguide delay line. By optically generating a picosecond electrical pulse we were able to examine the bandwidth and dispersion response of the delay line up to 100 GHz. The analysis of this structure's performance confirms the veracity of our kinetic inductance model. Investigating the nonlinear inductance device dependent effects, we developed the first all HTS Josephson junction parametric amplifier. We have fabricated and tested series arrays of HTS engineered step edge junctions for four photon parametric effects at 10 GHz. The series array of 25 junctions shows a 10 dB increase in reflected signal power as the pump power is increased at 10 K. At 50 K the reflected signal power shows a 3 dB increase. The reflected power at the characteristic idler frequency suggests four photon interaction. In addition, an anomalous gain saturation effect is experimentally observed whereby the reflected signal power maintains a constant increased value even as the reflected idler power decreases.