THz waves (terahertz waves) include electromagnetic waves with frequencies from 0. 1 to 10THz. This term is applicable to the frequency between the high-frequency edge (300 GHz) and the low-frequency far-infrared edge (3000 GHz) of millimeter wave band of electromagnetic radiation, which corresponds to radiation with a wavelength range of 0.03mm ~ 3mm (or 30~3000μm).