Imaging transport current distribution in high temperature superconductors using room temperature scanning laser microscope

We report the feasibility of room temperature scanning laser microscopy (RTSLM) for the study of high temperature superconducing films. RTSLM images from SmBa2Cu3O7 and YBa2Cu3O7 thin films show that the ac-voltage response exists only in the section of the bridge where the transport current produces a voltage drop. A photolithographically defined 60 gm x 60 mum void in a 300 mum-wide bridge was clearly visible in a RTSLM image giving the spatial resolution smaller than 60 gm. In addition, the void disturbs the transport current distribution beyond itself generating an elongated shape void of 64 mum x 85 mum with the longer side along the direction of current flow in the RTSLM image. Our results indicate that the RTSLM is a useful tool to investigate the transport current distribution in high temperature superconductors.