Terahertz radiation

Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency^[1] (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahertz (THz),^[2] although the upper boundary is somewhat arbitrary and is considered by some sources as 30 THz.^[3] One terahertz is 10¹² Hz or 1,000 GHz. Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm = 100 μm. Because terahertz radiation begins at a wavelength of around 1 millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy. This band of electromagnetic radiation lies within the transition region between microwave and far infrared, and can be regarded as either.

Compared to lower radio frequencies, terahertz radiation is strongly absorbed by the gases of the atmosphere, and in air most of the energy is attenuated within a few meters,^[4][5][6] so it is not practical for long distance terrestrial radio communication. It can penetrate thin layers of materials but is blocked by thicker objects. THz beams transmitted through materials can be used for material characterization, layer inspection, relief measurement,^[7] and as a lower-energy alternative to X-rays for producing high resolution images of the interior of solid objects.^[8]

Terahertz radiation occupies a middle ground where the ranges of microwaves and infrared light waves overlap, known as the "terahertz gap"; it is called a "gap" because the technology for its generation and manipulation is still in its infancy. The generation and modulation of electromagnetic waves in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques.