Efficient detection of short-pulse THz radiation with field effect transistors

Here we report on the efficient detection of THz radiation generated from Ti:sapphire femtosecond laser system. The large-area interdigitated antenna is excited by optical pulses with pulse duration from 15 to 47 fs. We have tested two AlGaN/GaN HEMT-based THz detectors with integrated broadband antennas. Detectors are comparable in sensitivity but differ in applied parasitic signals elimination techniques. Despite being sensitive, the pick-up of the first detector without strong parasitic elimination exceeded the theoretically expected noise level about 100 times. For a second detector we have implemented more stringent interference avoiding techniques, such as gate shunting with a low resistance value resistor, and have managed to significantly improve system's detection capabilities. We have lowered a pick-up near to the thermal noise level and have extended signal/noise ratio to 26 dB.