Subpicosecond, freely propagating electromagnetic pulse generation and detection using GaAs:As epilayers

Using GaAs epilayers with arsenic precipitates (GaAs) as the photoconductive material in a broad-band optoelectronic terahertz beam system, we have generated and detected freely propagating, subpicosecond electromagnetic pulses. The receiver signal gave a measured integrated pulse width of 0.71 ps. Fast photoconductive rise times have been achieved which are characteristic of good mobility GaAs. In addition, the material exhibits a short "effective" carrier lifetime of several ps due to the embedded, closely spaced (about 20 nm) arsenic precipitates.