Optimization of photoconducting receivers for THz spectroscopy

We have studied the sensitivity and noise of optically gated dipole receivers made from ion implanted Si and GaAs in an optimized time domain THz spectrometer. The spectrometer uses a room temperature, dc biased, semi-insulating GaAs stripline source capable of generating up to 30 µW average power. The 10% amplitude system bandwidth for 10 µm (50 µm) dipole receivers is 3 THz (1.5 THz). A dynamic range of 4 × 105 Hz−1/2 is achieved using a 10 µm dipole GaAs receiver and 2 × 106 Hz−1/2 using a 50 µm dipole for a total laser power of 110 mW and THz beam power of 20 µW. The dynamic range achieved with comparable silicon receivers is a factor of 2 smaller.