2010 Volume 79 Issue 6 Pages 524-529
The laser was first realized in 1960 by the development of maser in the frequency of optical range based on stimulated emission of radiation. The frequency of the coherent radiation of a laser jumped to several hundred THz in a single step from GHz, which was the highest frequency of coherent electromagnetic waves when lasers were first realized. For a long time the intermediate frequency was left as an unexplored area called the “terahertz gap”. However, in recent years the development of THz-wave sources by various techniques has been accomplished, and a variety of applications have been investigated. The progress in the development of THz-wave sources and their future prospects are described.
