60 GHz active microscopy with a bow-tie antenna as near-field probe

A near-field reflectometry experiment operating at 60 GHz is built in view of material and circuit inspection. The linearly-polarized electric-field probe is a bow-tie antenna obtained from femtosecond laser cutting of pieces in a tungsten metal sheet subsequently attached to an open rectangular waveguide. First images reveal a true near-field detection with strongly subwavelength resolution up to λ/130 at a 5 μm probe-sample distance. Images of various metal objects evaporated on Si substrate also show near-field intensities that are quantitatively related to the conductivity of the different metals.