Terahertz radiation

The term terahertz radiation refers to electromagnetic waves in the frequency range around 1 terahertz (1 terahertz [THz] = 1,000 gigahertz [GHz] = 10¹² hertz).

The upper and lower frequency limits are not clearly defined. As a minimum, terahertz radiation is considered to include frequencies from 0.3 to 3 terahertz, but the range is sometimes also expanded downwards (to 0.1 terahertz or even further) and upwards into the adjacent infrared region (up to 150 terahertz, for example).

The region between 30 and 300 gigahertz (= 0.03 to 0.3 terahertz) is referred to as millimetre waves. Immediately below that are the centimetre waves. Millimetre and centimetre waves are also referred to as microwaves.

Lastly, terahertz radiation with frequencies between 0.3 and 3 terahertz is also described as submillimetre waves or far infrared (FIR).