Terahertzradiation is the electro-magnetic radiation in a frequency range betweenmillimeter waves and microwaves on the one end, and infrared radiation on theother. The former are used by radios, satellite TV, and mobile phones, whilethe latter are used by infrared cameras and heat radiators. In numbers,Terahertz radiation has a frequency between 100 Gigahertz (GHz) and 10 Terahertz (THz). Until a few years ago, the generation of useful THz radiationtook high efforts.

Manyelectrically non-conducting materials like paper, plastics, and compositematerials are transparent for THz radiation. It is therefore possible to lookinto closed containers and packages similarto using x-rays. In addition, the material composition and material interfaces can be analyzed precisely.

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