Detection of nanosecond-scale, high power THz pulses with a field effect transistor

We demonstrate detection and resolution of high power, 34 ns free electron laser pulses using a rectifying field effect transistor. The detector remains linear up to an input power of 11 +/- 0.5 W at a pulse energy of 20 +/- 1 mu J at 240 GHz. We compare its performance to a protected Schottky diode, finding a shorter intrinsic time constant. The damage threshold is estimated to be a few 100 W. The detector is, therefore, well-suited for characterizing high power THz pulses. We further demonstrate that the same detector can be used to detect low power continuous-wave THz signals with a post detection limited noise floor of 3.1 mu W/root Hz. Such ultrafast, high power detectors are important tools for high power and high energy THz facilities such as free electron lasers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705986]