Terahertz technologies bear great potential in spectroscopy, material science, security screening and high-speed wireless communication. At terahertz frequencies, light undergoes considerably less scattering in amorphous materials than in the visible or near-infrared spectral range, leading to several unique properties of terahertz rays.

However, the generation of intensive, directional terahertz radiation has been difficult, and the terahertz frequency range has long been considered the last final frontier of the electromagnetic spectrum. Recent progress in high power electronic sources and in optoelectronic terahertz generation techniques has helped to finally bridge the terahertz gap and has opened up a wealth of new applications.