  This work presents new experimental results on low-temperature (LT)
characterization of local rf properties of passive superconducting (SC)
microwave devices using a novel Laser Scanning Microscope (LSM). In this
technique, a modulated laser beam is focused onto and scanned over the surface
of a resonant SC device to probe the spatial distribution of rf current. The
highly localized photo-induced change of the kinetic inductance of the SC
device produces both a shift of the resonant frequency f_0 and change of the
quality factor Q. An image of these changes is recorded as the laser spot is
scanned over the device. We present the first measurements of spatially
resolved intermodulation response in a High Temperature Superconducting (HTS)
co-planar waveguide resonator, opening up a new window into the local origins
of nonlinearity in the HTS materials.
