Photoconductive Antennas Based on Low Temperature Grown GaAs on Silicon Substrates for Broadband Terahertz Generation and Detection

We present investigations of photoconductive antennas (PCA) based on low temperature grown GaAs (LT GaAs) on silicon substrates for terahertz (THz) generation and detection. The PCAs consist of 2 mu m thick layers of LT GaAs grown on a high resistivity silicon substrate in order to reduce the intrinsic absorption losses around 8 THz due to a strong phonon resonance in GaAs. Using 20 fs long pump pulses around 800 nm and dipole antennas with dipole lengths between 20 mu m and 60 mu m a maximum bandwidth up to 12 THz and a maximum dynamic range exceeding 90 dB at 0.5 THz were obtained. The average output power was measured with a calibrated detector to be 95 mu W at a repetition rate of 80 MHz.