This chapter summarizes the operation principles and the current state of the art of THz detectors. THz detection techniques can be divided between pulsed time domain and continuous wave (CW) modalities. For CW systems, two primary modalities exist for detection of signals in the terahertz range. Heterodyne detection involves the reduction of the terahertz signal to sufficiently low frequencies to allow amplification and signal processing. The second approach is direct detection, where the terahertz signal impinging upon a detecting device results in a measurable response. This chapter focuses only on the CW detection methods. Preference is given to the conventional direct detection followed by heterodyne detection. At the end we present plasmonic THz detection technique with the current status and future outlook.
