Spectral Terahertz Imaging with a Quantum-Cascade Laser

In this report we demonstrate a high-spectralresolution terahertz (THz) imaging system on the basis of a THz quantum-cascade laser (QCL), a fast scanning mirror (FSM), and a cryogenic-cooled Ge:Ga detector. During the scan through an absorption cell filled with methanol (CH3OH), spectral information is obtained through QCL frequency tuning within a range that covers the feature of interest. Our results provide information about the spatial distribution of CH3OH gas based on the transmission at the central frequency of the absorption line. The image acquisition time is on the order of a few seconds and only limited by the mechanics of the employed FSM. This allows for fast detection of a leaking THz-transparent tube that is mounted into the absorption cell