Tunable CW-THz system with a log-periodic photoconductive emitter

A continuous wave(CW) terahertz(THz) optoelectronic system, based upon low-temperature-grown (LTG) GaAs photoconductor technology, capable of generating coherent radiation with frequencies tunable up to about 3 THz is reported in this paper. The aim of the research is to optimize the photoconductive emitter design for high output power. The results are obtained with a log-periodic circular-toothed antenna having a 6-finger photomixer at the driving point. The optical power sweep data are obtained at a frequency of 0.5 THz and a bias voltage of 20 V. At the maximum optical power of 26 mW, the recorded lock-in signal corresponds to a THz power level of ≈ 50 nW. The lock-in signal which is directly proportional to the THz power shows the characteristic quadratic behavior at low optical power levels.