Tuning superconducting microwave filters by laser trimming

At present, superconducting filters are usually tuned using screws, but there are many reasons to seek an alternative. Laser trimming is an attractive choice. A laser trimming system is described that can tune a high temperature superconductor microstrip filter while it is cooled and connected to a network analyser. Software has been written to control the system, fit measured data and modify a filter design to account for unintended couplings. The residual material left after trimming YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// has been shown to have negligible microwave loss. The system has been used to tune a simple three-resonator filter.