Terahertz near-field microscopy

We report on the development of an apertureless scanning near-field optical microscope for characterization of dielectric properties of nano-structures at terahertz frequencies. A spatial resolution of similar to 150 nm is achieved, which corresponds to a sub-wavelength factor of similar to 1/1000. The imaging mechanism is due to a resonant coupling between light field and the tip-surface system. This allows for image contrasts which exceed those can be expected from Mie scattering by orders of magnitude. Terahertz images of organic and inorganic structures show that the apertureless terahertz microscopy gives insight into the dielectric properties on submicron scale.