Picosecond-scale Terahertz pulse characterization with field-effect transistors

Precise real-time detection of Terahertz pulses is a key requirement in Terahertz communication technology,
non-destructive testing, and characterization of pulsed Terahertz sources. We experimentally evaluate the speed
limits of Terahertz rectification in field-effect transistors using the example of pulses from a free-electron laser. We develop an improved model for the description of these Terahertz pulses and demonstrate its validity experimentally by comparison to spectroscopic data as well as to expectation values calculated from free-electron laser physics.
The model in conjunction with the high speed of the detectors permits the detection of an exponential rise time of the pulses as short as 5 ps despite a post detection time constant of 11 and 14 ps for a large area and an antenna-coupled detector, respectively. This proves that field-effect transistors are excellent compact, roomtemperature Terahertz detectors for applications requiring an intermediate frequency bandwidth of several tens of GHz.