Recent advances in solid-state electronic terahertz systems

The terahertz (THz) band generally indicates the spectrum range that falls on roughly between the traditional electrical and optical frequency bands. Its definition varies over different sources, but one widely accepted definition is the frequency range of 0.1–10 THz. In terms of the wavelength in free space, it corresponds to the range of 3–0.03 mm. In terms of the more readily accepted band definition in the scientific community, the THz band partly include the mm-wave band (1 mm–1 cm, or 30–300 GHz) for the lower side and the infrared band (0.3 mm–750 nm, or 1–400 THz) for the upper boundary, while it covers the entire range of sub-millimeter band (0.1–1 mm, or 300 GHz–3 THz). It is notable that the range includes some scientifically significant points, one example being the frequency that corresponds to a photon energy equal to kT at room temperature (~6.2 THz).