Silicon CMOS-based THz detection

The detection of THz radiation, until recently the domain of specialized technologies, is now becoming linked to main-stream silicon CMOS technology, which entails significant advantages concerning costs, reliability, function integration, etc. Following the prediction that field-effect transistors (FETs) can detect THz radiation far above their cut-off frequency by a mixing process involving plasma waves in the FET's channel, we and others have developed CMOS FET detectors and arrays of them which are entirely fabricated in commercial foundries. We report an excellent noise-equivalent power of 43 pW/√Hz at room temperature and of a few pW/√Hz at cryogenic temperatures of detectors for 0.6-THz radiation. An added advantage of FETs is their high cut-off frequency which permits their use in heterodyne mode. The sensitivity is enhanced, and the detection of amplitude and phase of the radiation not only allows the determination of the complex dielectric constant of materials but also opens the way to three-dimensional imaging. We finally specify parameters for real-time active imaging at 0.6 THz.