Millimeter-wave scattering microscopy using a knife blade as a scanning probe

We report on the use of a knife blade as a scanning probe for scattering-type scanning near-field microscopy at millimeter wavelengths. Since the knife blade probe is a wider version of the metal tip antenna (whisker antenna) widely used in the terahertz and infrared regions, an improvement in signal intensity, and hence in the image contrast was expected. A scanning method and an image reconstruction algorithm based on computerized tomography were used to obtain 2-D near-field images. Experiments performed at 60 GHz using a knife blade with a tip radius of 6 μm (~λ/1000) showed that the signal intensity was enhanced by 20 dB compared with a metal tip antenna with an equivalent tip radius, and that an image resolution approaching the tip radius of the knife blade was achieved.