Figure 1.

Block diagram of the terahertz dual-comb imaging system. A first optical frequency comb is generated from the output of the master laser by two phase modulators, then two teeth (with a frequency spacing equal to the central THz signal to be generated) are filtered by optical injection locking and a dual-comb signal is created from one of them; both signals are recombined on an UTC photodiode. The emitted THz signal is focused on the sample plane and detected later by a FET detector. The insets show (from left to right) the spectrum of the THz dual-comb, the responsivity of the FET detector and the spectrum of the multi-heterodyne signal after detection.