Development of near-field microscopy for THz imaging

The first demonstration of THz imaging by Hu and Nuss has stimulated many suggestions for applications ranging from biomedical imaging to semiconductor device inspection. However, many applications demand a microscopic resolution. For instance, THz imaging of biological cells would require submicron spatial resolutions because many cells have dimensions of the order of 10 μm. Even finer resolutions would be required in semiconductor technology where today many devices are smaller than 1 μm. Such resolutions are not easy to reach with THz technologies, because of the long wavelength of THz radiation (1 THz corresponds to a wavelength of 300 μm). Many works took up the challenge to reduce spatial resolutions down to the 1 μm barrier and recently our group demonstrated a resolution of 150 nm.