Abstract-A promising approach to localized spectroscopy at far-infrared ( 5 m) and terahertz frequencies (100-3000 GHz) is with scanning probe microscopes by transducing far-field radiation to the near field with a field confinement structure-a near-field antenna. Here we discuss the background of this idea and show encouraging results from a scale-model experiment using 3-GHz microwave radiation. We also present experiments to scale antennas to visible wavelengths and we discuss limits to scale modeling.Index Terms-Atomic force microscopy, coaxial aperture antennas, infrared spectroscopy, millimeter-wave antennas.