Terahertz-Optics

THz radiation (3 mm-30 µm, 1011-1013 Hz) is low in energy and therefore not harmful. It penetrates major types of plastics, paper, clothing and semiconductors. However, it is absorbed by water and reflected by metal. Moreover, the molecules of many organic substances, medication, illegal drugs and explosives, have rotational transitions that can be detected and identified with the THz radiation.