What is TeraHertz?

When we refer to ‘TeraHertz energy’, we are referring to energy radiated within the terahertz (THz) region of the electromagnetic spectrum.

Terahertz, is a unit of frequency, defined as one trillion (1012) cycles per second or 1012 hertz. The THz region lies between the microwave and infra-red regions and subsequently shares some properties with each of these. The THz region is commonly considered to encompass the frequency range of 0.1 to 3 THz.

TeraHertz energy is naturally emitted from objects with a temperature greater than 2 degrees Kelvin, however metals emit negligible amounts of THz energy.  THz energy can be generated artificially using lasers and other electronic sources however SubTera’s NDT solutions function by measuring naturally occurring THz energy.

Capabilities of TeraHertz NDT

TeraHertz energy transmits through many materials, however it is attenuated heavily by liquids and metals.  Liquids absorb THz energy waves and metal reflects them.  Therefore SubTera’s THz NDT solutions cannot be used to inspect inside metals and liquids.

THz energy that is transmitted through materials can be used for material characterisation and internal or underlying feature inspection.

THz energy is non-ionising, therefore it does not present the same health and safety risks as X-ray inspection. It can however be used as an alternative to X-rays for producing suitably high resolution images of internal features within an object.


There are many applications for TeraHertz NDT within the high-value manufacturing, processing and quality control industries.  Due to the properties of many non-metallic materials, TeraHertz energy can be used to see internal or concealed defects, and to detect the presence of foreign objects within the material.

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