US Patent 7709799 Terahertz detector

A detector for electromagnetic radiation in the range 80 GHz to 4 THz comprises a laser light source (115) an optical modulator (13) arranged to modulate light from the laser light source (11) and a filter system (17) for selecting a defined range of frequencies of the modulated light. The optical modulator is an electroabsorption modulator (13) with an antenna (15) which is sensitive to electromagnetic radiation in the range 80 GHz to 4 THz. The signal received by the antenna (15) modulates the electric field across the electroabsorption modulator (13), whereby to modulate the light from the laser light source (11).