Scattering near-field microscopy in the THz region using a free-electron laser

We present scattering-type scanning near-field optical micro-spectroscopy (s-SNOM) investigations successfully operated in the THz range with a wavelength independent spatial resolution of <; 150 nm. As a variable and monochromatic radiation source we use the free-electron laser (FELBE) located at the Forschungszentrum Dresden-Rossendorf (FZD) tunable over the wavelength range from 4-250 μm.