Phase control in high-temperature superconductors and novel fabrication procedure for superconducting components

We demonstrate a process by which phase control of high-T_c superconductors can be achieved by photoswitching. In oxygen-deficient YBa ₂Cu₃O_6+d, optical switching between two structural states can be achieved by applying visible and near-infrared light. The states also exhibit different transport properties, and thus this photoswitching gives an opportunity to control metastability and superconducting property in the same crystal as a function of photon density. With the help of scanning near-field optical microscope, we apply such a phase control technique to fabrication procedure for superconducting nano-components such as superconducting wires in insulating film and optical switches.