Spatially resolved spectral-imaging by a THz-FEL

Using the unique characteristics of the free-electron-laser (FEL), we successfully performed high-sensitivity spectral-imaging of different materials in the terahertz (THz) and far-infrared (FIR) domain. THz imaging at various wavelengths was achieved using in-situ spectroscopy by means of this wavelength tunable and monochromatic source. In particular, owing to its large intensity and directionality we could collect high-sensitivity transmission imaging of extremely low-transparency materials and three-dimensional objects in the 3-6 THz range. By accurately identifying the intrinsic absorption wavelength of organic and inorganic materials, we succeeded in the mapping of spatial distribution of individual components. This simple imaging technique using a focusing optics and a raster scan modality has made it possible to set up and carry out fast spectral-imaging experiments on different materials in this radiation facility.