Influence of surface structures

Terahertz time-domain spectroscopy (TDS) is an established technology for identification and characterization of materials. For mobile applications, reflective TDS measurements will often be required. This poses additional challenges, caused by the surface topology of a tested material. Surface roughness can be in the same order of magnitude as the wavelength of the THz signal and will alter it through scattering and diffraction effects. This needs to be considered, e.g. when training a classifier to identify materials based on TDS. To systematically investigate the effects of surface topology, we have developed methods to fabricate material samples with defined surface profiles. The surface profiles are computer-generated based on predefined parameters, e.g. with a target RMS roughness. Based on the digital model, we employ a CNC mill, 3D printers and molding processes to create specimen of many different materials. These include polymers (plastics), wood, resins and other solidifying materials.