In the recent years, it has been shown that terahertz (or T-ray) spectroscopy is a versatile tool for biosensing and
safety applications. This is due to the fact that the THz-spectra of many biomolecules show very characteristic,
distinct spectroscopic features. Furthermore, most non-metallic packaging materials are nearly transparent in
this frequency range (0.1 - 6 THz, 3 cm-1 - 200 cm-1), so that it is possible to non-invasively identify even
sealed substances like pharmaceuticals, illicit drugs or explosives by their spectroscopic signatures. This opens a
significant potential for a wide range of applications from quality control of pharmaceutical substances via safety
applications through to biomedical applications.
The individual spectroscopic features below approximately 5 THz that spurred the increased world wide
interest in T-ray spectroscopy are mainly due to intermolecular rather than intramolecular vibrations in the
polycrystalline samples. The spectra of more complex biomolecules, like proteins and nucleotides, typically
show less or even no sharp features, due to the lack of long- range intermolecular order. Furthermore, due to the
typically significantly smaller sample amount, the signal to noise ratio is strongly increased. Water shows a strong
absorption in this frequency range, which all together makes real biomedical applications of T-ray spectroscopy
rather difficult. Yet, by combining a careful sample preparation, novel experimental techniques and an advanced
signal processing of the experimental data we can still clearly distinguish between even complex biomolecules
and therefore demonstrate the potential the technique holds for biomedical applications.