5. Detectors sensitive to THz wave amplitude

5.1 Measurement techniques

From radio waves to microwaves, the electric field of an incident wave is detected by the alternating current it induces in a metal conductor acting as an antenna. However, the THz wave field oscillates with a periodicity of the order of a picosecond or less, and today there are no electronics capable of recording such brief signals. If a detector delivers a signal proportional to this THz field, this signal can only be recorded with the required temporal accuracy using equivalent-time techniques. There are, however, a few publications presenting single-shot techniques, based on frequency drift (chirp) of laser readout pulses, or on geometrical time delay effects, but these have not been widely used to date.

The equivalent-time measurement...