Terahertz science and technology has a wide range of applications, and often it is the potential for application that has driven the innovative research in this field.  Some applications are well enough developed that there is already commercially available technology.  Other applications are more speculative and there is a huge amount of activity both in academic and industrial research to make these exciting prospects a reality.

THz science and technology requires that some combination of producing, controlling, collecting and measuring or analysing THz radiation is required.  Applying this beyond the laboratory requires considerations of convenience, size and cost to be successfully negotiated.

Applications in THz can be largely categorised into three areas (although there is overlap between these categories) – THz Imaging, THz spectroscopy and THz Communication.

THz Imaging

THz imaging essentially involves taking a picture with electromagnetic radiation at the THz frequencies.  This is comparable to taking a photograph or an X-ray which both use electromagnetic radiation from different parts of the electromagnetic spectrum.  The benefit of THz radiation is that some materials that are opaque to visible light are transparent to THz waves, allowing the potential to see through some materials.  Unlike X-rays, the THz waves are not energetic enough to damage cells.  THz imaging allows higher resolution imaging than microwave imaging because of the shorter wavelength. 

THz imaging usually involves THz waves being directed at the object of study, and then the waves being studied after they have interacted with the object.  A subset of THz imaging is “passive imaging” which collects THz electromagnetic radiation naturally being radiated by the body that is being studied. This is similar to a thermal camera which collects infrared (heat) wavelengths.  People naturally emit electromagnetic radiation in the THz range.  Passive imaging would help allay concerns about the safety and privacy of THz scanners.

THz Spectroscopy

THz spectroscopy moves beyond imaging to look at information available within the THz electromagnetic radiation emitted from a body.  Detailed investigation of the radiation will reveal that the radiation is not being emitted at all frequencies, and the pattern of frequencies being absorbed and emitted by a material forms a spectroscopic “fingerprint” that can allow identification. Many molecules absorb and emit radiation at THz frequencies.

 The techniques of imaging and spectroscopy can be combined to allow “functional imaging” – where a subject is both imaged and its composition analysed.

Terahertz Communication

 Communication at THz frequencies is an attractive proposition due to the “crowding” at longer wavelengths.  There is a continuing demand for wireless communication but the radio frequency bands already host wi-fi, radio, t.v and mobile phone technology. The available bandwidth in the THz region allows the possibility of high data transfer rates. Strong absorption in the atmosphere due to water vapour means that there is a restriction on the range of use, but there have been exciting improvements in the last ten years in the power and efficiency of sources.