As an optical technique, terahertz spectroscopy and imaging offer the advantages of non-contact measurements i.e. avoiding direct contact with the material, which is highly desired when studying small and fragile samples. On a larger scale such as in an industrial facility, optical measurements for materials inspection can be fast and flexibly integrated along with a production line.
However, several technical difficulties are associated with the less mature terahertz technology compared to other optical techniques. For example, weak sources, insensitive detectors, bulky optical components, and the complex analysis for extracting material parameters may limit its potential for industrial usage. For terahertz imaging, a major challenge is that the diffraction limit dictates that the spatial resolution will be worse than hundreds of micrometers for conventional systems. To overcome this several near-field terahertz imaging have been invented, where the Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) based terahertz nanoscope offers a spatial resolution on the order of 20 nm.
In this presentation, an overview of today’s terahertz spectroscopy and imaging techniques is given, where recent advances can enable both measurements on the nanoscale and larger scales relevant for production lines in the industry. This leads to our recent work on measurements of carrier dynamics in nanocomponents and thin-film solar cell materials, and terahertz systems for sorting of recycling plastics.