Terahertz Time Domain Spectroscopy for molecules inspection: water vapor and drugs

In this paper we report on an experimental study of the spectral response of different compounds in the THz range. We set up a THz Time Domain Spectroscopy System (TDS) that uses a Ti:Sapphire femtosecond laser and a pair of LTD GaAs photoconductive antennas for THz generation and detection. The THz TDS set up was validated through the matching of the main lines of the water vapor spectra in the 0.1-3THz range against the HITRAN database. Finally, the THz spectra of two commercial chemical compounds (paracetamol and ibuprofen) were obtained; the large difference found between the two spectra will easily allow to distinguish between both substances. Further work will be necessary to understand the fingerprints of those substances.