Near-field scanning microwave probe based on a dielectric resonator

We report a near-field microwave microscopy based on a novel scanning probe—a long and narrow slot microfabricated on the convex surface of the dielectric resonator. The probe is mounted in the cylindrical waveguide. Tunable coupling to the probe is effectuated through the variable air gap. The whole probe is very compact, has a coaxial input, operates at 25–30 GHz, has a spatial resolution of 1–10 μm and, most important, has a low impedance of ∼20 Ω. This allows us to use it for characterization of metallic layers with high conductivity, in particular, thickness mapping.