2. Introducing the terahertz domain

2.1 Why is the T

Far-infrared or terahertz radiation is a spectral range that complements current techniques (optics, RF, etc.). Its use has become increasingly widespread since the simultaneous advent of "femtosecond" lasers, but also thanks to constant progress in the design and manufacture of new micro- and even nanoelectronic components. For transferable applications, these new techniques are replacing conventional far-infrared methods, which use black bodies as radiation sources and bolometers as detectors (with long measurement times).

There are many advantages to using this type of radiation. Firstly, as opposed to well-known ionizing rays such as X-rays, terahertz radiation is capable of penetrating organic or inorganic matter without causing damage....