Near-field antennas integrated with scanning probes for THz to visible microscopy: scale modeling and limitations on performance

A promising approach to localized spectroscopy at far-infrared (/spl lambda/ > 5 /spl mu/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. 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.