PHOTOMIXING UP TO 3.8-THZ IN LOW-TEMPERATURE-GROWN GAAS

Low-temperature-grown (LTG) GaAs is used as an optical-heterodyne converter or photomixer, to generate coherent continuous-wave output radiation from microwave frequencies up to 3.8 THz. The photomixer consists of an epitaxial layer of LTG GaAs with interdigitated electrodes fabricated on the top surface. Terahertz photocurrents are generated in the gaps between the electrodes, and power is radiated into free space through a three-turn self-complementary spiral antenna. In a photomixer having a 0.27-ps electron-hole lifetime and small electrode capacitance, the output power is practically flat up to about 300 GHz and then rolls off at a rate of approximately 12 dB/oct. © 1995 American Institute of Physics.