Patent ID: 8563955

Claim:
A passive terahertz radiation source configured to emit electromagnetic radiation having a frequency in a range of 10 GHz to 50 THz, the passive terahertz radiation source comprising: a source of a pulsed excitation light; an emitter comprising one or more emitter elements, each emitter element comprising a semiconductor layer being arranged such that at least a portion of a first major surface of said semiconductor layer is exposed to the pulsed excitation light; where each emitter element is configured such that upon exposure to the pulsed excitation light, a gradient of a charge carrier density is generated in the semiconductor layer in an area of transition between a first area of the semiconductor layer and a second area of the semiconductor layer, the gradient being substantially parallel to the first major surface of the semiconductor layer, and where the passive terahertz radiation source is configured to emit electromagnetic radiation without using an external magnetic field.