The mechanism of nonlinear microwave behaviour in high-Tc superconducting devices

First, this paper gives an overview of possible origins and mechanisms that might be responsible for experimentally observed nonlinear effects. Focusing on well-known physical loss mechanisms with nonlinear characteristics, their impact on microwave properties and their relevance in microwave devices are discussed. Secondly, an experimental investigation of the power handling capability of coplanar resonators in additionally applied dc magnetic fields in zero field cooled, field cooled, and field sweep experiments is presented. These experiments demonstrate that the microwave power handling capability of optimized high-T-c thin film devices is limited by a maximum current density, and suggest that the limitation is caused by the dc critical current density J(c) of the superconducting material.