Two Dimensional Intermodulation Distortion Scanning of Superconducting Filter Resonators
Dr. Steven Remillard
Superconductor nonlinearity, manifest through non-Ohmic conductivity, is not fully understood. In the past global methods, or a weighted average of an entire sample, have been used. But in order to fully understand where the nonlinearity comes from, one must use local methods or measurements that look at a specific point in the sample. Ohm’s law for the sample becomes V=IR(I) because the resistance of the sample is dependent on the current. One local method consists of raster scanning samples with a magnetic loop probe. A problem encountered in doing this was that the probe resolution was too inadequate to image details across the width of a transmission line. This limitation was addressed in this work by reducing the size of the dipole loop on the magnetic loop probe. Using the electromagnetic field solver Sonnet, two dimensional current simulations of superconducting microwave filters composed of Tl2Ba2CaCu2O8/LaAlO3 or of YBa2Cu3O7/LaAlO3 reveal microwave current which is bunched up at the corners and sides of the sample. Two dimensional images of third order intermodulation distortion made with the magnetic probe at the same corners and edges reveal elevated distortion in the same places. Using the magnetic probe, third order intermodulation was seen to come from the same corners and edges where the current is bunched.
A recommended citation will become available once a downloadable file has been added to this entry.