Optical probing technique for inhomogeneous superconducting films

We report a nondestructive optical probing technique for superconducting films, by which a cross-sectional gradient of the local transition temperature Tc and a two-dimensional map of the local critical current I c of an Al film were obtained. The two-dimensional map clearly shows a variety of defects of the Al film. Some of them can be correlated to visible pinholes.