Abstract
Since terahertz (THz) spectra are sensitive to crystal structures, they are available for crystal polymorph
identification and quantification. They can also be utilized to detect defects in crystal, such as impurity
molecules. Thus, THz spectroscopy provide high sensitivity and a low detection limit for pharmaceutical
inspection. In this paper, we first present our originally developed high-frequency accurate CW
Gallium Phosphide (GaP) THz spectrometer and then demonstrate trace impurity detection in pharmaceuticals.
Such high-frequency accurate spectroscopy has potential for the inspection of middle molecular
weight (MMW) pharmaceuticals, which are expected to become mainstream in the near future.
