Effect of Current Amplitude and Coupling Strength on the microwave Performance of YBa2Cu3O7-x SQUIDs at 3 GHz

Abstract

The microwave properties of hysteretic single junction SQUIDs coupled to half-wavelength microstrip resonators were investigated at 3 GHz between 4.2 and 80 K. The samples were prepared from epitaxial YBa2Cu3O7-x films on LaAlO3 substrates with steps. Different designs of SQUID loop (with normalized inductance, β), coupling between loop and resonator and integrated flux focussers were chosen. The microwave current distribution across the resonant structure was simulated with a full-wave analysis computer code. The threshold behavior and periodic dependence of the dissipative SQUID response on the current amplitude yielded informations on β and the mutual inductance between loop and resonator. Coupling constants k of a few percent were deduced from the reactive SQUID response. The experimental data agreed with the results of the simulation.