Near-field scanning millimeter-wave microscope using a standard resonant waveguide probe at millimeter wavelengths

We demonstrate a millimeter-wave surface imaging technique using a near-field scanning millimeter-wave microscope with a resonant standard waveguide probe. The operating frequency is 30-39 GHz. The probe tip is mounted in a standard resonant waveguide. By tuning the insertion length of the probe tip, we could modulate the coupling power between the probe tip and the resonant waveguide. Measuring the detector output power and the frequency, we obtained near-field scanning millimeter-wave images of patterned YBa₂Cu₃O_y on a MgO substrate and Cr film on a glass substrate with a spatial resolution better than 2 μm. To characterize the sensitivity of our system, we measured reflectivity of films using a network analyzer for Ag, ITO, organic copper (II) phthalocyanine thin films.