Patent ID: 7915641

Claim:
A terahertz electromagnetic wave radiation element which receives two coherent light waves, mixes them, and radiates a terahertz electromagnetic wave corresponding to the difference frequency thereof, the element comprising: a semiinsulating semiconductor bulk layer; a two-dimensional electron layer formed directly above the semiconductor bulk layer by a semiconductor heterojunction structure; a source electrode electrically connected to one side of the two-dimensional electron layer; a drain electrode electrically connected to another side of the two-dimensional electron layer opposite to the source electrode; a double gate electrode grating provided in the vicinity of an upper surface of the two-dimensional electron layer and parallel to the two-dimensional electron layer, two different dc bias potentials being able to be alternately set for the double gate electrode grating; and a transparent metal mirror provided in contact with a lower surface of the semiconductor bulk layer, formed into a film shape, functioning as a reflecting mirror in the terahertz band, and being transparent in the light wave band, wherein two light waves are caused to enter from a lower surface of the transparent metal mirror, and two different dc bias potentials are alternately applied to the double gate electrode grating so as to periodically modulate the electron density of the two-dimensional electron layer in accordance with the configuration of the double gate electrode grating.