INVESTIGATIONS OF VARIOUS CW TERAHERTZ PHOTOMIXERS

Various cw terahertz (THz) photomixers were investigated and compared. Beams of two cw, tunable, single mode DFB (distributed feedback) diode lasers were used for illumination of the devices. Simple photoexcited gap structure, spiral-type and dipole-type integrated antennae patterns photomixers were used while carrying out investigations. Cw THz radiation has been generated by photoconductive devices made using low-temperature-grown GaAs layers. Antennae fabricated on GaAs and GaBiAs layers were used for coherent detection of cw THz radiation. It was obtained that the sensitivity of GaBiAs detectors is more than two times higher than in the case of GaAs detectors. GaAs emitters with integrated spiral-type antennae were most efficiently emitting in the low frequency range; enhanced bias voltages of such devices result in generated THz power comparable with the photomixers with interdigitated contact structures.