What is Terahertz?
Terahertz (THz) are electronic waves which operate at a frequency within the Terahertz spectrum. Their spectral fingerprint rests between microwaves and infrared, invisible due to being out of the visible light spectrum, and the least explored region of the electromagnetic spectrum. Until the 1990s, producing and detecting coherent terahertz radiation was challenging, but in modern times the terahertz spectrum can be utilised in many ways.
THz waves can pass through clothing, paper, cardboard, wood, plastic, fog and clouds, amongst other materials, but will not penetrate metal or water. Terahertz radiation has many properties which enable it to be used to create spectroscopic information and 3-D imaging of structures and materials in a number of different industries, including medical and pharmaceutical, semiconductor, solar and homeland security.
Uses for Terahertz for Homeland Security:
Research into terahertz has shown that different explosives have unique signatures within the terahertz spectrum. Traditionally, metal-only detectors are employed as detectors in the security industry; at airports for example. These can detect metal weapons such as knives or guns, but can offer a misleading impression of safety in a day when ceramic knives and liquid explosives are a real threat to homeland security. Whole body scanners implement the use of millimetre waves and X-Rays, but have proved extremely controversial for their ability to reveal the human anatomy.
Scientists have created terahertz light scanners which can be used to detect and identify explosives and improvised explosive devices (IEDs), even through numerous layers of clothing or when hidden inside shoes. This technology is safe, non-invasive and can be operated remotely, and detects frequencies rather than showing an image of a person. Terahertz will not only indicate the presence of explosive materials, but as each has a different spectral fingerprint in the terahertz range each material can be identified. In addition to this, terahertz scanners can identify ceramics, such as ceramic knives, which are not detected on metal detectors.
Other Uses for Terahertz Technology:
Other applications which can utilise the terahertz spectrum are medical imaging and spectroscopy, as terahertz radiation is less likely to damage tissues and DNA than X-Rays. Terahertz pulsed imaging can be used to indicate basal cell carcinoma (a common skin cancer) which is invisible to the naked eye, as well as other cancers too, and the radiation in non-ionising and safe. Dental imaging with terahertz creates a more accurate and detailed image than those offered by an X-Ray. Terahertz pulsed imaging can also be used in the pharmaceutical industry for its properties in determining protein structure, folding and characterisation.
Other uses for terahertz imaging and spectroscopy include communications, manufacturing, the solar industry and the semiconductor industry. The new developments into the terahertz spectrum have revealed a wealth of uses and potential uses, revealing the potential of terahertz to become a leading imaging and spectroscopy method across the globe.