Microspectroscopy and imaging in the THz range using coherent CW radiation.

A novel THz near-field spectrometer is presented which allows the performance of biological and medical studies with high spectral resolution combined with a spatial resolution down to lambda/100. In the setup an aperture much smaller than the used wavelength is placed in the beam very close to the sample. The sample is probed by the evanescent wave behind the aperture. The distance is measured extremely accurately by a confocal microscope. We use monochromatic sources which provide powerful coherent cw radiation tuneable from 50 GHz up to 1.5 THz. Transmission and reflection experiments can be performed which enable us to study solids and molecules in aqueous solution. Examples for spectroscopic investigations on biological tissues are presented.