1. Physics and applications of THz electromagnetic waves

1.1 Terahertz waves

The boundaries of the THz domain are not rigorously defined, but rather the subject of consensus. It is accepted that this domain extends between the microwave and mid-infrared (MIR) frequencies, over the spectral range 100 GHz to 10 THz. These "round" numbers have the advantage of being easy to remember. In view of the increasing frequency of microwave techniques, some people are now pushing the lower limit towards 300 GHz. We use the following relationships between photon energy E and frequency f, wavelength λ, or equivalent temperature T :