AN EXPERIMENTAL APPARATUS FOR MEASURING SURFACE-RESISTANCE IN THE SUBMILLIMETER-WAVELENGTH REGION

A simple comparative technique to characterize surface electrical resistance of small metallic samples at submillimeter wavelengths is presented. A quasioptical hemispherical resonator, fed by an optically pumped far-infrared laser is used, with the sample serving as the plane mirror. The cavity developed combines a small beam size at the sample, enabling measurements on samples with widths as small as 5 mm, with a large quality factor Q, so that surface resistance losses are readily measurable. This cavity uses a simple new geometry that feeds the cavity through a single small coupling hole that also serves as a system of monitoring energy storage in the cavity by means of a single external beamsplitter. An alternate approach of inserting an internal beamsplitter into the resonator was found to be unacceptable due to excessive losses and alignment problems.