Nonlinear HTS lumped elements in microwave transmission and resonance circuits

Abstract

Certainly, the dip emergence in the resonator with NLE and the decay emergence in the line with NLE are of the same nature. One can see a full analogy between IL(Pin) dependence for the line and ILdip(Pin) dependence for the resonator with NLE (ILdip - insertion losses in the dip of AFC dependence). The rapid initial decrease in the dip on AFC dependence for resonators with NLE corresponds to the first step on the IL(Pin) dependence, obtained for the lines with NLE. Our measurements have revealed the linear dependencies ILdip(Pin)∼Pin and IL(Pin)∼Pin for resonators and lines, correspondingly (Pin is measured in dbm). The rapid increase of the dip on resonator AFC curves, as well as the rapid increase of the line decay with the input power increase, can be explained by a rapid increase of the NLE surface resistance, caused by its transition from superconducting to the normal state. The heat origin of these effects is supported by observations of hysteretic behavior of the IL(Pin) dependence, measured in the line with NLE. Coincidence of the critical current density values, obtained from microwave and dc transport measurements, indicate that penetration of microwave induced Abrikosov vortices is responsible for the YBCO film heating and its subsequent transition to the normal state, contrary to the suggested model of Josephson weak links [8]. Calculations, performed in the work [5], show that the NLE transition to the normal state proceeds not abruptly, but through formation of resistive domains, causing strong rise of the line decay, when the input power slightly increases.