  A novel THz near-field spectrometer is presented which allows to perform
biological and medical studies with high spectral resolution combined with a
spatial resolution down to l/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 accurate 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.
