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 LIP to 30 muW average power. The 10% amplitude system bandwidth for 10 mum (50 mum) dipole receivers is 3 THz (1.5 THz). A dynamic range of 4 x 10(5) Hz(-1/2) is achieved using a 10 mum dipole GaAs receiver and 2 x 10(6) Hz(-1/2) using a 50 mum dipole for a total laser power of 110 mW and THz beam power of 20 muW. The dynamic range achieved with comparable silicon receivers is a factor of 2 smaller.