Optical characterization of GaAs photoconductive antennas for efficient generation and detection of Terahertz radiation

We report the optical characterization of low temperature (LT)-GaAs and Semi Insulating (SI)-GaAs based dipole types Photoconductive (PC) antennas with gap of 5 μm for the generation and detection of Terahertz (THz) signals. We have used tunable 140 femto-seconds laser pulses at 80 MHz repetition rate of different power and biasing voltage to evaluate the performance of our antennas as a THz generator and detector. Interestingly, we found that LT-GaAs and SI-GaAs have high photocurrent (density of charge carriers) response at some specific laser wavelengths such as 840 nm and 880 nm, respectively. We have employed these selected wavelengths for the generation and detection of THz radiation from these materials made PC antennas. The comparative study shows that the intensity of THz radiation in case of SI-GaAs is higher than the LT-GaAs made PC antennas. The THz frequency spectrum range of LT-GaAs and SI-GaAs antennas are extended up to 3.6 THz and 2.5 THz respectively. Finally, we have cross verified the reliability of our antennas to detect the THz radiation generated from ZnTe crystal.