PRECISION SUBMILLIMETER WAVE LASER REFLECTION MEASUREMENTS OF HIGH-TEMPERATURE SUPERCONDUCTORS

Submillimeter wave laser reflection measurements Of surface resistance can provide improved capability in the combination of sensitivity, spatial resolution, and frequency range. We have made reflectivity measurements on metals at 1630 GHz with an uncertainty of less than 0.3%. This sensitivity corresponds to a measurement sensitivity for surface resistance of 0.3 OMEGA. Assuming an f2 frequency scaling of high-temperature superconductor surface resistance from the microwave to the terahertz frequency range, this sensitivity corresponds to about 1 x 10(-5) OMEGA at 10 GHz.Capability for 10(-7) OMEGA sensitivity could eventually be possible. Preliminary submillimeter wave reflection measurements of a YBCO thin film have been made with a sensitivity of 1%. Submillimeter wave reflectometry can make it possible to determine the spatial dependence of surface resistance in a wide range of material sizes and shapes. The spatial resolution could be on the order of 0.3-0.5 mm.